Pressure
Pressure Relief
Relief Valves
Valves
Technical
Technical Manual
Manual
ANDERSON GREENWOOD
flow control
Anderson Greenwood Pressure Relief Valves
Technical Manual
Contents
Pressure Relief Valves
General Information ...........................................................................
Glossary ............................................................................................
1, 2
3, 4
Valve Sizing
Nomenclatures ...................................................................................
Valve Data .........................................................................................
Back Pressure and Subsonic Correction............................................
Gas and Vapor....................................................................................
Steam .................................................................................................
Liquid ..................................................................................................
Subsonic Flow ....................................................................................
Special Applications ...........................................................................
Reaction Forces .................................................................................
5-7
8 - 14
16 - 21
22 - 24
25 - 30
31 - 35
37 - 45
46 - 47
48
Conversion Factors
........................................................................................................... 49 - 55
Fluid Data
........................................................................................................... 56 - 61
ANSI Flange Standards
........................................................................................................... 62 - 76
Valve Installations - Handling Procedures
...........................................................................................................
ASME Code Section
77
I1
Excerpts ............................................................................................. 78 - 91
ASME Code Section IV1
Excerpts ............................................................................................. 92 - 97
ASME Code Section VIII1
Excerpts ............................................................................................. 98 - 116
API RP 520 Part I1
Excerpts ............................................................................................117 - 149
API RP 520 Part II1
Pressure Relief Valve
Technical Manual
NACE MR0175-951
Revised May 1998
Catalog: PRVTM-US.97
API RP 5211
Excerpts ............................................................................................150 - 158
Excerpts ............................................................................................159 - 169
Noise Levels ......................................................................................
170
API RP 5271
Seat Leakage Requirements ..............................................................171 - 173
Note
1. Some referenced figures, tables, equations,
or paragraphs may not be included. Consult
original document for complete text.
Section 16
Chemical Resistance for Metals ........................................................174 - 180
Section 17
Chemical Resistance for Elastomers/Thermoplastics ........................181 - 205
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
3
Anderson Greenwood Pressure Relief Valves
Technical Manual
General Information
Intro
Body Materials
Anderson Greenwood is a globally recognized leader in the field of pressure relief
device technology. Fundamental to our
ability to solve the most challenging application is our belief in understanding all
application parameters. As a leader in the
field of pressure relief device education, we
proudly provide this manual for use as the
finest technical source on our technology
and the specialized area of these safety
devices. The users of this manual will benefit from its completeness as a pressure
relief device resource document.
Pressure relief valve standard body materials are ASME SA-216 grade WCB or
WCC CS, or ASME SA-351 GR. CF8M
SS. Also available at additional costs are
bodies of special alloys, such as Hastelloy®
‘C’, Monel®, high temperature alloy, duplex SS, Titanium, alloy 20 and others.
Castings
Valve castings to meet requirements of
radiography, magnetic particle, liquid penetrant examination and Charpy Impact
tests are available on special order. Our
documented quality control can provide
complete chemical and physical analysis
for all cast materials on request.
Standard Flanged Connections
(a) All steel flange ratings conform to
ANSI B-16.5 – 1977 and are indicated
on each orifice selector chart in the applicable product catalog. Heavier outlet
flanges are available on application.
For back pressure exceeding listed
values, consult the factory for valve
limitations. Steel raised face flanges
are provided with a serrated finish on
the flange face.
(b) Standard Aluminum valves are manufactured with flat faced flange finish in
accordance with commercial practice.
The flanges are designated as Class
125 FF, with drilling equal to ANSI
Class 150.
Copyright Notes
1. © ASME: the American Society of
Mechanical Engineers.
2. © NACE: National Association of Corrosion
Engineers.
3. © API: American Petroleum Institute.
Notes
1. Shop test procedure for temperature compensation available on request.
2. All shop orders will state 100°F [38°C] unless customer’s purchase order states
otherwise.
3. Inconel® and Monel® are registered trademarks of the International Nickel Company.
4. KYNAR® is a registered trademark of the
Pennwatt Chemical Corporation.
5. Hastelloy® is a registered trademark of
Haynes International.
(c) All iron flange ratings conform to
ANSI B-16.1 – 1977 and to Flange
Dimension Table (page 70). Iron flat
face flanges are supplied with a
smooth surface on flange face.
(d) Bronze flange ratings conform to ANSI
B-16.24 and to Flange Dimension
Table (page 86). Bronze flat face
flanges are supplied with a smooth
surface on flange face.
(e) All ring joint flange facings comply with
ANSI B-16.5 – 1977 ring groove. For
ring joint facing dimensions, refer to
the Flange Dimension Table (page 73).
(f) Flange facings different from raised
face can be furnished at additional cost.
The standard surface finish roughness
is 125-250 AARH. DIN, JIS, or other
flange finishes may be available on a
product-by-product basis. Contact our
sales department for availabilities.
(g) Drilling of both inlet and outlet flanges
always straddles center lines. Offset
drilling is available with proper application.
Special Flanges
Anderson, Greenwood offers a variety of
non-standard connection arrangements to
meet the most exacting special flange requirement.
Spring Materials
Pressure relief valve standard spring materials are carbon steel aluminum painted.
Spring materials of special alloys, such as
tungsten steel, 316 SS, 302 SS, phosphor
bronze, K-Monel® and Inconel® and others are all available in many models on
request.
Spring Assembly
Corrosion Protection
At additional cost, springs can be furnished with protective finishes of phenolic,
plastic, epoxy resin, and nickel plate.
Bellows Valves
For easy field conversion, the conventional valve – D Series – may be changed to a
bellows valve – all orifice sizes from F to T
– by installing the bellows assembly and
gaskets. Standard material for all bellows
is Inconel® 625. KYNAR® coating, Monel®
and other materials available at additional
cost. Bellows conversions in D and E orifices require a body adapter, stem, guide,
gaskets and bellows.
Bellows Coating
The standard bellows is Inconel® 625.
KYNAR® coating of the bellows for additional corrosion protection is available at
additional cost.
Seating Surfaces
Armco 17-4 PH stainless steel hardened
to hardfaced equivalence is an optional
D Series disc material. The seating surfaces for other models with stainless steel
trim can be hardfaced, when specified, at
additional cost.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
1
Anderson Greenwood Pressure Relief Valves
Technical Manual
General Information
O-ring Seat Seals
Seat Tightness
Steam Jacketed Valves
Anderson Greenwood offers the most
complete line of pressure relief valves with
O-ring seat seals. All valves are available
– up to the maximum pressure limits – in
a variety of O-ring materials. See O-ring
Seals Section for complete details and
specifications.
All metal seated pressure relief valves are
tested for seat leakage per API STD 527
and ANSI B147.1.
To keep viscous fluids flowing or to prevent lading fluids from becoming solidified,
heat is often applied to the valves. Application of heat, to the valves and piping,
however, is often a problem. Steam
tracing lines and insulation are frequently
required, in addition to heating coils.
Removal and reinstallation of a valve is
expensive, time consuming and can create costly delays in a process application.
Trim or Wetted Parts
Trim refers to the nozzle or base and the
disc in direct spring valves. Consult each
product catalog for available materials.
Operating and Set
Pressure Differentials
Optimum performance of a direct spring
pressure relief valve protected system is
available at operating pressures up to
90% of valve set pressure. Pump and
compressor discharge pulsations are offset by the greatest allowable valve set
pressure differentials. System pressure
pulsations can cause valve malfunctions.
Therefore, the pressure relief valve should
be set as high as possible above the
discharge line pressure. Applications requiring closer system-to-valve pressure
differentials may be accommodated by
soft seat seal, or Anderson, Greenwood
high performance Series 80 or Pilot
Operated Valves.
Cold Differential Test
Pressure Recommendations
When pressure relief valves for high temperature service are tested at room
temperature, a compensating adjustment
is made in the set pressure. High temperature reduces set pressure – lessens
spring load – via thermal expansion of
spring, body and bonnet. Cold differential
test pressure adjustments are also
required on unbalanced valves when
constant applied back pressure conditions
exist. Cold differential test pressure
adjustments are indicated on the valve
nameplate, and are recorded on the functional test report.
The Anderson Greenwood tightness
standard for Series 80 and Pilot Operated
pressure relief valves soft seated valves
is: ‘no leakage at 95% of set pressure for
set pressures of 60 psig [4.13 barg] and
higher, or no leakage at 3 psig [.21 barg]
below the set pressure for set pressures
below 60 psig [4.13 barg].’ For all other direct spring, soft-seated pressure relief
valves, seat tightness is: ‘no leakage at
90% of set pressure for set pressures 15
psig [1.03 barg], or no leakage at 3 psig
[.21 barg] below the set pressure for set
pressures below 15 psig [1.03 barg].’
Special Applications
Many exacting process applications require specially built valves. When your
valve requirements exceed catalog descriptions, Anderson Greenwood invites
you to submit the specifications. Design
data and quotations will be furnished.
Valves for Corrosive Service
A design advantage frequently overlooked
in corrosive application is the full nozzle
inlet option on many of our valve models.
Until a valve discharges – an infrequent
occurrence – the only contact surfaces
are the wetted parts – nozzle and disc.
Where standard materials are susceptible
to attack, corrosion resistant alloys are
recommended.
Valves for Low Temperature
Service
Anderson Greenwood has a wide range of
pressure relief devices to meet service
temperatures to -450°F [-267°C].
Contact your Anderson Greenwood
representative or the factory for more information on Steam Jacketed Valves.
Steam Jackets are available in integrally
cast or bolt on type for the D and L Series
only.
Installation and Maintenance
Complete installation and maintenance
training manuals are available on request.
Replacement Valves
and Repair Parts
Submit valve serial number for exact
replacement. Anderson Greenwood will
supply a valve with correct materials and
dimensions. The serial number for most
valves is located on the nameplate and
stamped on the perimeter of the outlet
or body flange. Proper replacement will
be made for valves which have become
obsolete. Iron and bronze valves may require the complete model number, located
on the nameplate.
Repair Tools
For proper maintenance of Anderson
Greenwood Pressure Relief Valves, nozzle wrenches, lapping discs and lapping
plates are available, as are complete
operating, installation and maintenance
manuals.
Set Pressure Lower Limits
Minimum set pressure per valve series
is listed in the applicable product catalog.
©
Anderson
Greenwood reserves
the right to change
© 1997
1995
Keystone/Anderson,
Greenwood
& Co.product
designs and specifications without notice.
Proper heat transfer to keep viscous fluids
in their correct flowing state can be obtained by integrally jacketing the housing
of the valve. Piping can be simplified, thus
reducing maintenance time and permitting
the use of many standard replacement
parts.
2
2
Anderson Greenwood Pressure Relief Valves
Technical Manual
Glossary
Accumulation is the pressure increase
over the maximum allowable working
pressure of the vessel during discharge
through the pressure relief device, expressed in pressure units or as a percent.
Maximum allowable accumulations are
established by applicable codes for operating and fire contingencies.
Design Gauge Pressure refers to at least
the most severe conditions of coincident
temperature and pressure expected during
operation. This pressure may be used in
place of the maximum allowable working
pressure in all cases where the MAWP has
not been established. The design pressure
is equal to or less than the MAWP.
Actual Discharge Area is the measured
minimum net area that determines the
flow through a valve.
Effective Discharge Area or Equivalent
Flow Area is a nominal or computed area
of a pressure relief valve used in recognized flow formulas to determine the size
of the valve. It will be less than the actual
discharge area.
Back Pressure is the pressure that
exists at the outlet of a pressure relief
device as a result of the pressure in the
discharge system.
Balanced Pressure Relief Valve is a
spring-loaded pressure relief valve that incorporates a means for minimizing the
effect of back pressure on the performance characteristics.
Blowdown is the difference between the
set pressure and the closing pressure of a
pressure relief valve, expressed as a percent of the set pressure or in pressure
units.
Built-up Back Pressure is the increase in
pressure in the discharge header that develops as a result of flow after the
pressure relief device opens.
Closing Pressure is the value of decreasing inlet static pressure at which the
valve disc re-establishes contact with the
seat or at which lift becomes zero.
Cold Differential Test Pressure is the
pressure at which the pressure relief valve
is adjusted to open on the test stand. The
cold differential test pressure includes corrections for the service conditions of back
pressure or temperature or both.
Conventional Pressure Relief Valve is a
spring-loaded pressure relief valve whose
performance characteristics are directly
affected by changes in the back pressure
on the valve.
Curtain Area is the area of the cylindrical
or conical discharge opening between the
seating surfaces above the nozzle seat
created by the lift of the disc.
Huddling Chamber is an annular pressure chamber in a pressure relief valve
located beyond the seat for the purpose
of generating a rapid opening.
Inlet Size is the nominal pipe size (NPS)
of the valve at the inlet connection, unless
otherwise designated.
Leak-test Pressure is the specified inlet
static pressure at which a seat leak test is
performed.
Lift is the actual travel of the disc away
from the closed position when a valve is
relieving.
Maximum Allowable Working Pressure
(MAWP) is the maximum gauge pressure
permissible at the top of a completed
vessel in its operating position for a designated temperature. The pressure is based
on calculations for each element in a vessel using nominal thicknesses, exclusive
of additional metal thicknesses allowed for
corrosion and loadings other than pressure. The maximum allowable working
pressure is the basis for the pressure setting of the pressure relief devices that
protect the vessel.
Maximum Operating Pressure is the
maximum pressure expected during system operation.
Nozzle Area is the cross-sectional flow
area of a nozzle at the minimum nozzle
diameter.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
3
Anderson Greenwood Pressure Relief Valves
Technical Manual
Glossary
Opening Pressure is the value of increasing inlet static pressure at which
there is a measurable lift of the disc or at
which discharge of the fluid becomes continuous.
Outlet Size is the nominal pipe size
(NPS) of the valve at the discharge connection, unless otherwise designated.
Overpressure is the pressure increase
over the set pressure of the relieving device, expressed in pressure units or as a
percent. It is the same as accumulation
when the relieving device is set at the
maximum allowable working pressure
of the vessel, and the inlet pipe pressure
loss is zero.
Pilot Operated Pressure Relief Valve is
a pressure relief valve in which the main
valve is combined with and controlled by
an auxiliary pressure relief device.
Pressure Relief Device is actuated by
inlet static pressure and designed to open
during an emergency or abnormal conditions to prevent a rise of internal fluid
pressure in excess of a specified value.
The device also may be designed to prevent excessive internal vacuum. The
device may be a pressure relief valve,
a nonreclosing pressure relief device, or
a vacuum relief valve.
Rated Relieving Capacity is that portion
of the measured relieving capacity permitted by the applicable code or regulation to
be used as a basis for the application of a
pressure relief device.
Relief Valve is a spring-loaded pressure
relief valve actuated by the static pressure
upstream of the valve. The valve opens
normally in proportion to the pressure increase over the opening pressure. A relief
valve is used primarily with incompressible fluids.
Rupture Disc Device is a nonreclosing
differential pressure relief device actuated
by inlet static pressure and designed to
function by bursting the pressure-containing rupture disc. A rupture disc device
includes a rupture disc and a rupture disc
holder.
Safety Relief Valve is a spring-loaded
pressure relief valve that may be used as
either a safety or relief valve depending
on the application.
Safety Valve is a spring-loaded pressure
relief valve actuated by the static pressure
upstream of the valve and characterized
by rapid opening or pop action. A safety
valve is normally used with compressible
fluids.
Set Pressure is the inlet gauge pressure
at which the pressure relief valve is set to
open under service conditions.
Simmer is the audible or visible escape of
compressible fluid between the seat and
disc at an inlet static pressure below the set
pressure and at no measurable capacity.
Spring-loaded Pressure Relief Valve is
a pressure relief device designed to automatically reclose and prevent the further
flow of fluid.
Stamped Capacity is the rated relieving
capacity that appears on the device
nameplate. The stamped capacity is
based on the set pressure or burst pressure plus the allowable overpressure for
compressible fluids and the differential
pressure for incompressible fluids.
Superimposed Back Pressure is the
static pressure that exists at the outlet of
a pressure relief device before it actuates.
It is the result of pressure in the discharge
system coming from other sources and
may be constant or variable.
Relieving Conditions is the term used to
indicate the inlet pressure and temperature on a pressure relief device at a
specific overpressure. The relieving pressure is equal to the valve set pressure (or
rupture disc burst pressure) plus the overpressure. (The temperature of the flowing
fluid at relieving conditions may be higher
or lower than the operating temperature.)
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
4
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Nomenclature
Gas and Steam Flow
Symbol Description
Inch
Pounds
Metric
Units
square inch
(in2)
square centimeter
[cm2]
A
Orifice area or equivalent flow area.
C
The gas constant of gas, derived from
the specific heat ratio, k. If C is unknown, use C = 315, a conservative
value. Refer also to Physical Properties
of Selected Gases.
—
—
F´
Subsonic flow factor, based on the ratio
of specific heats and pressure drop (differential) across the valve or nozzle.
—
—
k
The ratio of specific heats of gas, where
k = Cp/Cv. When the value of k is unknown, use k = 1.001, a conservative
value. Refer also to Physical Properties
of Selected Gases.
—
—
K
The valve coefficient to be used where
set pressure is 15 psig [1.03 barg] and
greater, and in accordance with the requirements of Section VIII, Division 1 of
the ASME Boiler and Pressure Vessel
Code, ASME I, and ASME III. Valve coefficient K includes the required derating
to 90% of actual average measured nozzle coefficient, KD, as required by the
ASME Code. Please note that safety
valve models available for gas and liquid applications will have differing
nozzle coefficients.
—
—
Kb A back pressure correction factor for
gas, used when the flow becomes subsonic, occurring when the pressure ratio
across the valve nozzle exceeds the
critical pressure, PCF/P1.
—
—
KN Steam flow correction factor, from the
Napier equation.
—
—
KSH Superheat correction factor for use in
the steam formulas.
—
—
M
Molecular weight of the flowing gas.
Refer to Physical Properties of Selected
Gases, or other resources, for listing of M.
—
—
P
Set pressure in gauge units. All formulas
herein are based on barg or psig.
lb/in2 gauge
(psig)
bar gauge
[barg]
lb/in2 gauge
(psig)
bar gauge
[barg]
Pb Back pressure, under relieving conditions, at valve outlet in gauge pressure
units.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
5
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Nomenclature
Note
Gas and Steam Flow
Symbol Description
Inch
Pounds
Metric
Units
1. The formulas using this pseudo pressure
ratio are valid only for the specified pressure units to the right and for the Series 90
low pressure pilot operated safety valves.
P1
Absolute pressure at valve inlet connection under relieving conditions
and equal to set pressure, p + overpressure + atmospheric pressure.
Atmospheric pressure will be equal
to standard sea level pressure,
14.7 psia [1.013 bara], unless otherwise specified. When a local plant
site barometric pressure is mentioned, sizing for orifice area should
be made with the stated local barometric pressure.
lb/in2 absolute
(psia)
bar absolute
[bara]
P2
Absolute pressure at valve outlet
under relieving conditions; equal to
back pressure, pb + atmospheric
pressure (as expressed in previous
paragraph).
lb/in2 absolute
(psia)
bar absolute
[bara]
PCF/P1 Critical pressure ratio. The critical pressure ratio is used to determine if the
back pressure correction factor Kb
shall be applied to the sizing formula.
t
Relieving temperature, to be evaluated at the valve inlet, under relieving
condition.
T
Absolute relieving temperature,
equal to relieving temperature plus
base temperature, where:
T [°Rankin] = t [°F] + 460 and
T [Kelvin]
= t [°C] + 273
V
Gas flow capacity expressed in
volumetric units per time unit. The
formulas in this section are based
on a sea level atmospheric pressure
of 14.7 psia [1.013 bars] and a
temperature base of 60°F or 0°C,
respectively for metric and inchpound systems. Refer to Gas Flow
Conversions for other pressure and
temperature bases as well as other
units of measure.
W
Gas flow capacity expressed in
weight units per time unit. Refer to
Gas Flow Conversions for other
units of measure.
Z
Compressibility factor, correcting for
the difference between the physical
characteristics of a theoretical gas
and the actual gas under consideration. If Z is unknown, use Z = 1.00.
P2
lb/in2
absolute
(psia)
—
bar absolute
[bara]
P1
—
degrees Fahrenheit
(°F)
degrees Celsius
[°C]
degrees Rankin
(°R)
degrees Kelvin
[°K]
Set pressure = 15 psig
[1.03 barg] and higher
standard cubic feet normal cubic meters
per minute
per hour
(scfm)
[Nm3/h]
P2
pounds per hour
(lb/h)
kilograms per hour
[kg/h]
—
—
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
P1
Set pressure is less than
15 psig [1.03 barg]
6
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Nomenclature
Notes
Liquid Flow
1. Relief valves certified for liquid applica-
tions with full lift at 10% overpressure,
shall use Kp = 1.00 at 10% and greater
overpressure. The 1985 revision to ASME
VIII required all liquid relief valves to have
certified capacities at 10% overpressure.
Therefore, the use of Kp in the sizing formula would apply to non-ASME Code
valves only.
2. The maximum permitted values of over-
Symbol Description
Liquid Safety
Valve Type
10%
Pilot operated.
10%
Conventional and balanced direct spring
operated, with certified full
lift at 10% overpressure.
25%
Conventional and
balanced direct spring operated valves not meeting
the above requirements.
Note: Sizing may be done
at 10% overpressure when
the correction factor Kp is
made equal to 0.60.
Metric
Units
square inch
(in2)
—
square centimeter
[cm2]
—
A
Orifice area
G
Relative density of liquid at flowing temperature, referred to water at 68°F [20°C].
Gwater = 1.00.
K
Effective or certified nozzle coefficient. The
certified nozzle coefficients, when given,
are in accordance with the requirements of
Section VIII, Division 1 of the ASME Boiler
and Pressure Vessel Code, ASME I, and
ASME III and include a derating to 90% of
actual, as required by the Code. The effective nozzle coefficients, when given, also
assume the same derating, but are not certified by the National Board of Boiler and
Pressure Vessel Inspectors. Please note
that safety valve models available for gas
and liquid applications will have differing
nozzle coefficients.
—
—
Kp Capacity correction factor due to lift characteristics of conventional and balanced spring
operated valves, in liquid service, where full
lift is achieved at 25% overpressure. Use Kp
= 0.60 for sizing these valve types at 10%
overpressure, and Kp = 1.00 for 25% and
greater overpressure.1
—
—
Kv Capacity correction factor due to viscosity.
For most applications, viscosity may not be
significant, in which case use Kv = 1.00.
—
—
Kw Capacity correction factor for balanced bellows safety valves due to back pressure.
Use Kw = 1.00 for conventional (unbalanced) and pilot operated safety valves.
—
—
p1 Upstream pressure under relieving conditions. This is set pressure, plus
overpressure.2
lb/in2 gauge
(psig)
bar gauge
[barg]
p2 Total back pressure, under relieving conditions, at valve outlet.
lb/in2 gauge
(psig)
bar gauge
[barg]
—
—
pressure for various types of liquid safety
valves in this manual are as follows:
Maximum
Overpressure
Inch
Pounds
R
Reynolds Number. A dimensionless expression for the flow behavior of fluids
and is used to determine the viscosity
correction factor Kv.
µ
Absolute viscosity of the liquid at the relieving temperature. Kinematic viscosity
and/or viscosity expressed in other units
of measure must be converted to absolute viscosity in centipoise. Most liquid
applications need not consider viscosity
and should therefore use a Kv = 1.00.
The approximate viscosity of water under
most conditions is 1 centipoise. When viscosity is given, it should be considered.
centipoise
centipoise
W
Liquid flow rate.
US gallons
per min
(US gpm)
cubic meters
per hour
[m3/h]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
7
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Nozzle Coefficients
ASME Nozzle Coefficients – Direct Spring PRVs
Valve
ASME I
Steam
Hot Water
A Series
Steam
ASME III
Gas, Vapor
ASME IV
Steam
Liquids
.975
D Series
.878
.878
.700
Steam
ASME VIII
Gas, Vapor Liquids
.878
.878
.710
.878
.878
.700
F Series
.798
.878
.878
G Series
.840
.878
.878
K Series
.878
.878
L Series
Y Series
.874
.874
.475
.840
15W
.874
.874
.878
.878
.475
.975
Model 61
.877
Model 63B
.877
Model 83F
.847
Model 81, 83
.988
Model 86
.816
.816
Model 81P
.720
API Nozzle Coefficients – Direct Spring PRVs
Valve
ASME I
Steam
Hot Water
A Series
Steam
ASME III
Gas, Vapor
ASME IV
Steam
Liquids
Steam
ASME VIII
Gas, Vapor Liquids
.878
D Series
.971
.971
.776
.971
.971
F Series
.876
.910
.910
G Series
.876
.910
.910
K Series
.878
L Series
Y Series
.776
.878
.971
.971
.528
.971
.971
.528
.876
15W
.975
Model 61
.877
Model 63B
.847
Model 83F
.998
Model 81, 83
.816
Model 86
.816
Model 81P
.720
Note
1. ASME nozzle coefficient is the actual coefficient recorded by the National Board of
Boiler and Pressure Vessel Inspectors. It
differs from the API nozzle coefficient.
When sizing PRVs using the ASME coefficient, the ASME area must be used.
The API nozzle coefficient is an effective
coefficient to be used when sizing PRVs
using API 526 orifice areas.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
8
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Nozzle Coefficients
ASME Nozzle Coefficients – Pilot Operated PRVs
Valve
Steam
ASME VIII
Gas, Vapor
Liquids
223, 233
.830
423, 433
.830
.650
623, 633
.830
.650
823, 833
.830
.650
923, 933
.830
.650
226
.833
526
.833
.833
576
.809
.809
727
.788
.650
.788
273, 473, 673, 873, 973
.809
91/94
.770
93/93T
.845
95
.852
9300
.629
API Nozzle Coefficients – Pilot Operated PRVs
Valve
Steam
ASME VIII
Gas, Vapor
Liquids
223, 233
.860
423, 433
.860
.670
623, 633
.860
.670
823, 833
.860
.670
923, 933
.860
.670
226
.860
526
.860
.860
576
.860
.860
727
.975
.975
273, 473, 673, 873, 973
.860
91/94
.770
93/93T
.845
95
.852
9300
.629
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
9
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Orifice Areas
Orifice Areas – Direct Spring PRVs
Valve
Orifice
Designation
ASME Area
(in2)
[cm2]
API Area
(in2)
[cm2]
A Series
D
.1213
.783
.110
.710
A Series
E
.2157
1.392
.196
1.265
A Series
F
.3369
2.174
.307
1.981
A Series
G
.553
3.568
.503
3.245
A Series
H
.864
5.574
.785
5.065
A Series
J
1.415
9.129
1.287
8.303
D Series
D
.1219
.786
.110
.710
D Series
E
.2173
1.402
.196
1.265
D Series
F
.340
2.194
.307
1.981
D Series
G
.558
3.600
.503
3.245
D Series
H
.869
5.606
.785
5.065
D Series
J
1.427
9.206
1.287
8.303
D Series
K
2.036
13.135
1.838
11.858
D Series
L
3.160
20.380
2.853
18.406
D Series
M
3.987
25.720
3.600
23.230
D Series
N
4.807
31.010
4.340
28.030
D Series
P
7.070
45.610
6.380
41.160
D Series
Q
12.240
73.970
11.050
71.290
D Series
R
17.720
114.320
16.000
103.230
D Series
T
28.800
185.810
26.000
167.740
Note
1. The ASME area is the actual flow area certified by the National Board of Boiler and
Pressure Vessel Inspectors. The API area is
the flow area defined per API 526. When
sizing PRVs, care should be exercised to
not mix API and ASME values.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
10
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Orifice Areas
Orifice Areas – Direct Spring PRVs
Valve
Orifice
Designation
ASME Area
(in2)
[cm2]
API Area
(in2)
[cm2]
K Series
F
.307
1.981
.307
1.981
K Series
G
.503
3.245
.503
3.245
K Series
H
.785
5.065
.785
5.065
K Series
J
1.287
8.303
1.287
8.303
K Series
K
1.838
11.858
1.838
11.858
K Series
L
2.853
18.406
2.853
18.406
K Series
M
3.597
23.200
3.600
23.230
K Series
N
4.340
28.030
4.340
28.030
K Series
P
6.380
41.160
6.380
41.160
K Series
Q
11.045
71.260
11.050
71.290
L Series
—
.0767
.495
.069
.445
L Series
C
.150
.968
.135
.871
L Series
V
.248
1.600
.223
1.439
L Series
G
.559
3.606
.503
3.245
.110
.710
.110
.710
Model 61
Model 63B
5
.150
.968
.150
.968
Model 63B
7
.437
2.819
.437
2.819
Model 81, 83, 81P
-4
.049
.316
.049
.316
Model 81, 83
-6
.110
.710
.110
.710
Model 81, 83, 81P
-8
.196
1.265
.196
1.265
Model 81, 83
F
.307
1.981
.307
1.981
Model 81, 83, 81P
G
.503
3.245
.503
3.245
Model 81, 83
H
.785
5.065
.785
5.065
Model 81, 83, 81P
J
1.287
8.303
1.287
8.303
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
11
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Orifice Areas
ASME Orifice Areas – Pilot Operated PRVs
Valve Size
Type
X331
[0.98]2
Type
X231
Type
X731
Orifice Area, in2 [cm2]
Type 226/526
Type 576
Type 727
1” x 2”
11/2” x 2”
0.152 (‘D’)
0.265 (‘E’) [1.71]
0.318 (‘F’) [2.05]
—
—
—
—
11/2” x 2”
0.599 (‘G’) [3.86]3
0.817 (‘H’) [5.27]3
1.336 [8.62]
—
1.336 [8.62]
—
11/2”
0.599 (‘G’) [3.86]
0.817 (‘H’) [5.27]
—
0.817 (‘H’) [5.27]
—
x 3”
2” x 3”
3” x 4”
0.631 (‘G’) [4.07]
0.973 (‘H’) [6.28]
1.448 (‘J’) [9.34]
2.162 (‘K’) [13.95]
1.336 (‘J’) [8.62]
2.530 [16.32]
1.336 (‘J’) [8.62]
2.530 [16.32]
4.369 (‘M’) [28.19]
0.981 (‘H’) [6.33]
1.635 (‘J’) [10.55]
2.985 (‘L’) [19.26]
6.651 [42.91]
2.985 (‘L’) [19.26]
6.651 [42.91]
1.635 (‘J’) [10.55]
2.298 (‘K’) [14.82]
3.557 (‘L’) [22.95]
3.557 (‘L’) [22.95]
3.512 (‘L’) [22.66]
4” x 6”
—
0.629 (‘G’) [4.06]
6.651 (‘P’) [42.91]
9.629 [62.12]
6.651 (‘P’) [42.91]
9.629 [62.12]
5.054 (‘N’) [32.61]
4.505 (‘M’) [29.06]
5.425 (‘N’) [35.00]
7.911 (‘P’) [51.04]
6” x 8”
12.350 (‘Q’) [79.68]
16.655 (‘R’) [107.45]
6” x Dual 8”
—
—
16.655 (‘R’) [107.45]
21.520 [138.84]
13.813 (‘Q’) [89.12]
20.000 (‘R’) [129.03]
22.990 (‘RR’) [148.32]
21.520 [138.84]
—
—
—
—
8” x 10”
—
27.109 (‘T’) [174.90]
—
27.109 (‘T’) [174.90]
44.180 [285.03]
32.500 (‘T’) [209.68]
8” x Dual 8”
—
—
29.420 [189.81]
—
—
—
8” x Dual 10”
8” x Single 10”
—
—
44.180 [285.03]
—
44.180 [285.03]
—
Notes
1. Series 200/300/400/600/800/900.
2. Except for liquid service.
3. Threaded body only.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
12
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Orifice Areas
API Orifice Areas – Pilot Operated PRVs
Valve Size
Type
X331
Type
X231
Type
X731
Orifice Area, in2 [cm2]
Type 226/526
Type 576
Type 727
1” x 2”
11/2” x 2”
0.110 (‘D’) [0.71]2
0.196 (‘E’) [1.26]
0.307 (‘F’) [1.98]
—
—
—
—
11/2” x 2”
0.503 (‘G’) [3.24]3
0.785 (‘H’) [5.06]3
1.257 [8.11]
—
1.257 [8.11]
—
11/2”
0.503 (‘G’) [3.24]
0.785 (‘H’) [5.06]
—
0.785 (‘H’) [5.06]
—
x 3”
2” x 3”
3” x 4”
0.503 (‘G’) [3.24]
0.785 (‘H’) [5.06]
1.287 (‘J’) [8.30]
1.838 (‘K’) [11.86]
1.287 (‘J’) [8.30]
2.380 [15.35]
1.287 (‘J’) [8.30]
2.380 [15.35]
3.60 (‘M’) [23.22]
2.853 (‘L’) [18.41]
6.257 [40.37]
2.853 (‘L’) [18.41]
6.257 [40.37]
11.05 (‘Q’) [71.29]
6” x Dual 8”
8” x 10”
1.287 (‘J’) [8.30]
1.838 (‘K’) [11.86]
2.853 (‘L’) [18.41]
2.853 (‘L’) [18.41]
6.38 (‘P’) [41.16]
9.058 [58.44]
6.38 (‘P’) [41.16]
9.058 [58.44]
4.34 (‘N’) [28.00]
6” x 8”
0.785 (‘H’) [5.06]
1.287 (‘J’) [8.30]
2.853 (‘L’) [18.41]
4” x 6”
—
0.503 (‘G’) [3.24]
3.60 (‘M’) [23.22]
4.34 (‘N’) [28.00]
6.38 (‘P’) [41.16]
16.00 (‘R’) [103.22]
—
11.05 (‘Q’) [71.29]
16.00 (‘R’) [103.22]
16.00 (‘R’) [103.22]
—
—
—
20.244 [130.61]
—
—
—
—
26.00 (‘T’) [167.74]
—
26.00 (‘T’) [167.74]
41.56 [268.13]
26.00 (‘T’) [167.74]
8” x Dual 8”
—
—
27.675 [178.55]
—
—
—
8” x Dual 10”
8” x Single 10”
—
—
41.56 [268.13]
—
41.56 [268.13]
—
Notes
1. Series 200/300/400/600/800/900.
2. Except for liquid service.
3. Threaded body only.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
13
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Orifice Areas
Orifice Areas - Types 93/93T
Valve
Size
ASME
(in2) [cm2]
Orifice Areas - Types 91/94
API
(in2) [cm2]
Valve
Size
ASME
(in2) [cm2]
API
(in2) [cm2]
2”
2.29
14.77
2.29
14.77
2”
2.92
18.84
2.92
18.84
3”
5.16
33.29
5.16
33.29
3”
6.24
40.26
6.24
40.26
8.74
4”
8.74
56.38
56.38
4”
10.33
66.65
10.33
66.65
6”
19.56
126.93
19.56 126.93
6”
22.22
143.35
22.22
143.35
8”
36.40
234.84
36.40 234.84
8”
39.57
255.29
39.57
255.29
10”
51.00
329.03
51.00 329.03
10”
56.75
366.12
56.75
366.12
12”
84.00
541.93
84.00 541.93
12”
89.87
579.80
89.87
579.80
Orifice Areas - Type 95
Valve
Size
ASME
(in2) [cm2]
Orifice Areas - Type 96A
API
(in2) [cm2]
Valve
Size
ASME
(in2) [cm2]
API
(in2) [cm2]
2”
2.92
18.84
2.92
18.84
2”
11.70
75.48
11.70
75.48
3”
6.25
40.32
6.25
40.32
3”
23.89
154.12
23.89
154.12
4”
10.32
66.58
10.32
66.58
4”
36.80
237.42
36.80
237.42
6”
22.15
142.90
22.15 142.90
6”
80.93
522.12
80.93
522.12
Orifice Areas - Series 9000
Valve
Size
2”
3”
4”
ASME
(in2) [cm2]
3.356
7.393
21.65
47.69
API
(in2) [cm2]
3.356
7.393
21.65
47.69
12.73
82.12
12.73
82.12
6”
28.89
186.38
28.89
186.38
8”
50.027
322.71
50.027 322.71
10”
78.854
508.73
78.854 508.73
12”
113.097
729.66
113.097 729.66
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
14
Anderson Greenwood Pressure Relief Valves
Technical Manual
Back Pressure and Subsonic Flow Correction Factor
for Section I and Section VIII Sizing Formulas for Gas,
Steam and Liquid
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
15
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Evaluating Back Pressure Correction
Kb Factor for Gas and Steam
Sources of Back Pressure
When any back pressure exists, a test for
subsonic flow should be made. If the absolute outlet-to-inlet flowing pressure ratio
(P2/P1) is greater than 0.30 a back pressure correction factor Kb may be required
subject to the additional commentary below.
A pressure relief valve whose outlet is discharging into vent piping or to another
pressure vessel or system will encounter
one or two types of back pressure: superimposed and/or built-up.
The required values of Kb as a function of
P outlet/P inlet are determined from the
curves presented in this section for both
conventional spring operated and pilot operated pressure relief valves.
General
Whenever flow through a pressure relief
valve occurs under sonic conditions, the
value of Kb is 1.00. When a pressure relief
valve discharges directly to the atmosphere and the set pressure is 15 psig
[1.03 barg] or greater, flow is considered
to be sonic, therefore Kb remains equal to
1.00. If the pressure relief valve discharges into any piping where the back
pressure at the valve outlet under relieving conditions exceeds a definitive limit,
flow will be subsonic. The orifice area calculation of a pressure relief valve, flowing
under these conditions, must be mathematically adjusted using the back
pressure correction factor Kb.
Kw Factor for Liquids
Whenever back pressure is encountered
in bellows and pressure balanced spring
operated liquid relief valves, a reduction in
flow capacity due to reduced valve lift can
result. A Kw factor to correct for this reduction is included in the liquid capacity
equation. The required values of Kw
based upon P2/P1 are determined from
the curves at the back of this section.
Superimposed back pressure may come
from the vent system due to the discharge
of other pressure relief valves into a common manifold or due to the nature of other
processes that affect the downstream
pressure. The presence of superimposed
back pressure may not necessarily create
subsonic flow. However the outlet pressure may rise further, due to flow from the
pressure relief valve, and may be sufficient to cause subsonic flow.
Built-up back pressure occurs as a result
of the discharge of fluid through a flowing
pressure relief valve with connected
downstream piping or equipment. In some
instances, relatively short sections of piping connected by the outlet of a pressure
relief valve and venting to the atmosphere
will be sufficient to create back pressure
during a relieving cycle that will cause flow
to be subsonic.
The result will be a reduction of flow
capacity. If this is less than the required
relieving capacity, the inlet pressure may
rise sufficiently to exceed the permissible
accumulation for the application. The problem is compounded when there is also
some superimposed back pressure, since
built-up back pressure will be additive.
Conventional Direct Spring
Operated Pressure Relief Valves
If a conventional, direct spring operated
pressure relief valve is to be applied
where any built-up back pressure will be
developed, the maximum permissible
built-up back pressure shall not exceed
10% of set pressure. Under this limit, no
back pressure correction factor need be
applied, except as follows:
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
16
• When a conventional pressure relief
valve is set to open with a superimposed back pressure sufficiently high to
create subsonic flow, the back pressure
correction factor may be applied (assuming that the pressure ratio exceeds
the critical ratio).
• If the valve is known to be tolerant to a
greater amount, the back pressure correction factor may be applied.
Balanced Pressure Relief Valves
The balanced bellows valve is balanced
against superimposed back pressure. It
is also resistant to a moderate amount
of built-up back pressure. Apply the back
pressure correction factor Kb. When
balanced bellows valves are used, the
maximum permissible built-up back pressure should not exceed 40%.
Pilot Operated Pressure
Relief Valves
A properly selected and installed pilot operated pressure relief valve will operate
effectively under all combinations of superimposed and built-up back pressure,
limited only by the valve pressure rating
and practical considerations. Apply the
back pressure correction factor Kb, if applicable.
Solving for Kb
The critical pressure ratio is a function of
the value of k, the specific heat ratio of the
gas. The value of PCF /P1 varies from
0.444 to 0.607 for a range of k between
1.00 and 2.00. When sizing valve designs
for set pressures below 15 psig covered
under API 2000, the P outlet/P inlet ratio
may be calculated and compared directly
to the correct P critical for the gas or vapor k value. The k values for selected
gases, the P critical vs. k equation and a
set of P critical vs. k curves for frequently
encountered k values are presented in the
‘Fluid Data’ section of this manual.
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Superimposed Back Pressure
Correction Factors
Direct Spring PRVs/Vapor and Gases ASME Section VIII
Constant Back Pressure Correction Factor Kb
Back Pressure Correction Factor Kb
1.00
.90
.80
.70
.60
.50
.40
.30
.20
.10
0
▲
▲
▲
▲
▲
▲
▲
▲
▲
▲
▲
0
10
20
30
40
50
60
70
80
90
100
Back Pressure Percentage =
Back pressure, psia or bara
x 100
Flowing pressure, psia or bara
Example:
Set pressure = 200 psig [13.79 barg]
Constant back pressure = 160 psig [11.03 barg]
160 + 14.7
Back pressure percentage (absolute) = –––––––––––––– x 100 = 74% or
200 + 20 + 14.7
11.03 + 1.013
–––––––––––––––––– = 74%
13.79 + 1.38 + 1.013
Factor Kb = 0.91 (follow dotted line from curve)
Capacity with back pressure = 0.91 x rated capacity without back pressure
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
17
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Superimposed and Built Up Back
Pressure/Subsonic Flow Correction Factors
Capacity with back pressure
Variable Back Pressure Correction Factor Kb
Capacity with back pressure
Back pressure, psig or barg
x 100
Set pressure, psig or barg
50 psig [3.44 barg]
and over
.90
Example:
Set pressure = 100 psig [6.89 barg]
Back pressure = 0 to 35 psig [2.41 barg]
35
Back pressure percentage (gauge) = –––
100
x 100 = 35% max.
10% Overpressure
.80
15 psig
[1.013 barg]
.70
Factor Kb = 0.94 (follow dotted line from
curve)
Capacity with back pressure = 0.94 x rated
capacity without back pressure
.60
▲
0
▲
5
▲
10
▲
15
▲
20
▲
25
▲
30
▲
35
▲
40
▲
45
▲
50
Back pressure percentage =
Back pressure, psig or barg
x 100
Set pressure, psig or barg
Variable Back Pressure Correction Factor Kb
Example:
Set pressure = 100 psig [6.89 barg]
Back pressure = 0 to 35 psig [2.41 barg]
35
Back pressure percentage (gauge) = –––
100
x 100 = 35% max.
50 psig [3.44 barg]
and over
1.00
20% Overpressure
.90
15 psig
[1.013 barg]
.80
▲
0
▲
5
▲
10
▲
15
▲
20
▲
25
▲
30
▲
35
▲
40
▲
45
Factor Kb = 0.99 (follow dotted line from
curve)
Capacity with back pressure = 0.99 x rated
capacity without back pressure
▲
50
Kb =
Rated capacity without back pressure
Back pressure percentage =
1.00
Kb =
Rated capacity without back pressure
Direct Spring PRVs - Model Designations - Bellows Valves Only/Vapors
and Gases ASME Section VIII
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
18
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Superimposed and Built Up Back
Pressure/Subsonic Flow Correction Factor (Kb)
Back Pressure Correction Factor for Piston Pilot Operated PRVs Gas, Vapor, or Steam
1.000
k = 1.0
0.900
k = 1.2
k = 1.4
0.800
k = 1.6
k = 1.8
Back Pressure Factor, Kb
0.700
k = 2.0
0.600
0.500
0.400
0.300
0.200
0.100
0.000
0.200
0.300
0.400
P2
P1
0.500
0.600
0.700
0.800
0.900
1.000
= Absolute Pressure Ratio at Valve Inlet
The above curves are applicable for all
pressure ranges and overpressures and
accurately predict the reduction on capaci-
ty for full lift, API orifice valves. For full
bore valves, multiply above ‘Kb’ values by
0.95.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
19
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing - Back Pressure Correction Factor for Type 727 – Gas, Vapor or Steam
1.0
0.98
k = 1.0
0.96
Back Pressure Factor, K b
k = 1.2
0.94
k = 1.4
0.92
k = 1.6
0.90
k = 1.8
0.88
k = 2.0
0.86
0.40
0.45
0.50
0.55
0.60
P2 /P1 = Absolute Pressure Ratio at Orifice
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
20
0.65
0.70
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing - Liquid Flow
Direct Spring PRVs - Model Designation - Bellows Valves Only/Liquid
Service
Rated capacity based on Fd
Factor Kw = 0.95 (follow dotted line from
curve)
Capacity with variable back pressure =
0.95 x rated capacity
Based on differential pressure Fd
Variable or Constant Back Pressure Correction Factor Kw
1.00
.90
.80
.70
.60
▲
0
Kw =
Example:
Set pressure = 100 psig [6.89 barg]
Back pressure = 0 to 24 psig [1.65 barg]
24
Back pressure percentage (gauge) = –––
100
x 100 = 24% max.
▲
5
▲
10
▲
20
▲
15
▲
30
▲
25
▲
45
▲
40
▲
35
▲
50
Curve to Evaluate Liquid Back Pressure for Series 81P
Correction Factor kw
1.00
Kw = Back Pressure Correction Factor
Based on 10% Overpressure
Back pressure, psig or barg
x 100
Set pressure, psig or barg
Capacity with variable back pressure
Back pressure percentage =
0.90
0.80
Correction Curve
for Types 81P - 4
and 81P - 8
0.70
0.60
Correction Curve
for Types 81P - G
and 81P - J
0.50
0.40
0.30
0.20
0.10
0.00
▲
0
▲
5
▲
10
▲
15
▲
20
▲
25
Percentage Back Pressure =
▲
30
▲
35
▲
40
▲
45
▲
50
▲
55
▲
60
Back Pressure, psig [barg]
x 100
Set Pressure, psig [barg]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
21
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Gas and Vapor Equations
Sizing Information
ASME Section I and VIII
ASME VIII Gas Flow (Set Pressure ≥ 15 psig [1.03 barg])
U.S. Weight Flow (lb/h)
Formula 1
W
A = –––––––
CK P1Kb
––––
TZ
–––
M
√
U.S. Volumetric Flow (scfm)
Formula 2
––––
V √ MTZ
A = ––––––––––––
6.32 CK P1Kb
Metric Weight Flow [kg/h]
Formula 1M
1.316 W
A = –––––––
CK P1Kb
After system capacity has been determined, a properly sized pressure relief
valve is determined by the following
method.
––––
TZ
–––
M
√
Metric Volumetric Flow [Nm3/h]
Formula 2M
A. From the formulas in this section
calculate required orifice area as a
function of capacity. The orifice sizes
for steam, air, or water may be obtained from the capacity tables
catalog.
B. Identify the required orifice letter designation, such as D, E, F, etc. Always
choose an orifice which is equal to, or
greater than the required orifice area.
––––
V √ MTZ
A = –––––––––––––
17.02 CK P1Kb
C. Specifications exceeding Anderson
Greenwood standard catalog descriptions should be referred to our sales
department.
D. When selecting orifice areas and
nozzle coefficients, either select the
ASME area and nozzle coefficient,
or the equivalent API area and nozzle
coefficient.
Mixing ASME and API values is incorrect and may result in a dangerous
sizing error.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
22
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Gas and Vapor Flow (English Units)
Examples for Steam and Gas Applications
Example 1 - ASME VIII Gas
Solution:
Given: Butane, with a required flow rate of
16,000 scfm, set at 88 psig, 10%
overpressure, gas temperature
of 60°F, discharging to a closed
header system. The back pressure
(maximum) is 40 psig.
Use Formula 1
Find:
The required orifice area.
–––––
V √ MTZ
A = ––––––––––––
6.32 CK P1Kb
––––––––––––––
16,999 √ (58.12)(520)(1)
12.108
A = ––––––––––––––––––––– = ––––––
6.32 (326)(111.5) K Kb
K Kb
V
= 16,000
M
= 58.12
C
= 326
T
= 60 + 460 = 520
Z
= 1.0
P1
= 88 (1.1) + 14.7 = 111.5
Kb
= 40 = 45%
88
Bellows Valve – Kb = 0.77
Pilot Valve – 40 + 14.7 = 49%
111.5
Kb
= 0.98
For the bellows valve, the correct orifice selection would be an 8T10 (26.0 in2). For the
case of selecting a POSRV, the correct orifice selection would be 6R8 (16.00 in2).
Case 1 - Select a DB Series with K = 0.971, Kb = 0.77, A = 16.19 in2.
Case 2 - Select a POSRV with K = 0.86, Kb = 0.98, A = 14.36 in2.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
23
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Gas and Vapor Flow - [Metric Units]
Examples for Gas and Steam Applications
Solution:
Example 2
Use formula 1M and the physical properties found on pages 51-63.
Given: Butane, with a required flow rate
of 9,000 Nm3/h, set at 5 barg,
10% overpressure, relieving temperature of 15°C, discharging to
atmosphere.
P1
T
M
Z
Kb
=
=
=
=
=
5 x (1.1) + 1.013 = 6.513 bara
15 + 273 = 288°K
58.12, C = 326
1.00 (used when no value is given)
1.00 (when back pressure equals atmospheric)
Find:
––––––––––––––––
9,000 √ 58.12 x 288 x 1.00
32.22 cm2
A [cm2] = ––––––––––––––––––––––––– = –––––––––
17.02 x 326 x K x 6.513 x 1.00
K
A=
The required orifice area for a typical conventional safety valve and
the orifice selected.
32.22
= 33.18 cm2
.971
Selecting a valve with a K = 0.971, the orifice to be selected is a 4P6 (41.16 cm2).
Solution:
The same data is used as in example 2, except use a nozzle coefficient K = 0.809 (from
page 9) in formula 2M.
––––––––––––––––
9,000 √ 58.12 x 288 x 1.00
2
A [cm ] = –––––––––––––––––––––––––––– = 39.83 cm2
17.02 x 326 x 0.809 x 6.513 x 1.00
Example 3
Given: Same as example 2.
Find:
The appropriate size valve for a
piston type (Series 200, 300, etc.),
pilot operated safety valve.
From page 12, the next larger available orifice is 42.91 cm2 corresponding to a ‘fullbore,’ 3-inch x 4-inch valve, Series 273 or 473. Note in this example, ASME not API
coefficients are used.
Solution:
Example 4
The back pressure represents 44% of the set pressure (2.2/5.0).
For a Direct Spring SRV, Kb = 0.78, for a 200 Series Pilot Operated PRV, the back pressure represents 49% of the absolute pressure ratio:
2.2 + 1.03
5.0 x 1.1 + 1.03
Given: The same as example 2, except
with a built-up back pressure of
2.2 barg.
Find:
Therefore, the Kb for the Series 200 = 0.985 (from page 19).
Again using formula 2M, for the Direct Spring Valve:
–––––––––––––––
9,000 √ 58.12 x 288 x 1.0
A = ––––––––––––––––––––––––––– = 42.54 cm2
17.02 x 326 x 971 x 6.513 x .78
Selecting a direct spring would result in a 6Q8 (71.29 cm2).
For the POSRV:
A
–––––––––––––––
9,000 √ 58.12 x 288 x 1.0
32.71 cm2
= ––––––––––––––––––––––––––– = ––––––––
17.02 x 326 x K x 6.513 x .985
K
Case 1 - Select a Type 223, K = 0.830, A = 39.40 cm2.
Case 2 - Select a Type 273, K = 0.809, A = 40.43 cm2.
Selecting a pilot valve could either be a 4P6 (42.91 cm2) or a full bore 3 x 4 (42.91 cm2).
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
24
The appropriate size to meet the
relieving conditions.
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Steam Flow
Sizing Information
ASME Section I and VIII
After system capacity has been determined, a properly sized pressure relief
valve is determined by the following
method.
A. From the formulas in this section
calculate required orifice area as a
function of capacity. The orifice sizes
for steam, air, or water may be obtained from the capacity tables
catalog.
B. Identify the required orifice letter designation, such as D, E, F, etc. Always
choose an orifice which is equal to, or
greater than the required orifice area.
C. Specifications exceeding Anderson
Greenwood standard catalog descriptions should be referred to our sales
department.
D. When selecting orifice areas and nozzle coefficients, either select the ASME
area and nozzle coefficient, or the
equivalent API area and nozzle coefficient.
Mixing ASME and API values is incorrect and may result in a dangerous
sizing error.
ASME I Sonic Steam Flow (Set Pressure ≥ 15 psig [1.03 barg])
U.S. Units (lb/h)
Formula 3
Metric Units [kg/h]
Formula 3M
W
A = –––––––––––––––––
51.45 K P1KSHKNK b
W
A = –––––––––––––––––
52.45 K P1KSHKNK b
KN = 1.00 for P ≤ 1500 psig
KN = 1.00 for P ≤ 103.4 barg
0.1906 P - 1000
KN = –––––––––––––
0.2292 P - 1061
2.764 P - 1000
KN = –––––––––––––
3.323 P - 1061
where 1500 psig < P < 3200 psig
where 103.4 barg < P < 220.7 barg
ASME VIII Sonic Steam Flow (Set Pressure ≥ 15 psig [1.03 barg])
U.S. Units (lb/h)
Formula 4
Metric Units [kg/h]
Formula 4M
W
A = ––––––––––––––––
51.5 K P1KSHKNK b
W
A = ––––––––––––––––
52.5 K P1KSHKNK b
KN = 1.00 for P ≤ 1500 psig
KN = 1.00 for P ≤ 103.4 barg
0.1906 P - 1000
KN = –––––––––––––
0.2292 P - 1061
2.764 P - 1000
KN = –––––––––––––
3.323 P - 1061
where 1500 psig < P < 3200 psig
where 103.4 barg < P < 220.7 barg
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
25
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Steam (English Units)
Examples for Steam Applications
Solution:
Example 5 - ASME I Steam
W
Use Formula 3
Given: Steam, with a required flow rate
of 4,050 lb/h, set at 18 psig, is
required for an ASME I boiler
application. Steam temperature
is 420°F.
KSH = 0.97
W
A=
51.45 K P1KSHKNKb
4050
A = –––––––––––––––––––– =
51.45 K (.97)(1)(34.7)(1)
= 4050
KN = 1.00
2.388
––––––
K
Kb
= 1.00
P1
= 18 + 2 + 14.7 = 34.7
Find:
Selecting a valve with a K = 0.878 (K Series), A = 2.66 in2.
=
in2).
Note the overpressure for set
This orifice corresponds to an L orifice (2.853
pressures between 15 psig and 70 psig is 3% or 2 psig minimum.
Solution:
2.338
K
Example 6 - ASME VIII Steam
Use Formula 4
W
W
A=
51.5 K P1KSHKNKb
Given: Steam, with a required flow rate
of 84,000 lb/h, set at 400 psig,
is required for an unfired pressure
vessel application. Steam temperature is 448°F.
= 84,000
KSH = 1.00
KN = 1.00
84,000
A = –––––––––––––––––––– =
51.5 (K)(1)(1)(454.7)(1)
3.587
––––––
K
Kb
= 1.00
P1
= 400 (1.1) + 14.7 = 454.7
Selecting a valve with a K = 0.971 (D Series), A = 3.69 in2.
This orifice corresponds to a 4N6 orifice (4.34 in2).
The approximate flowing capacity can be estimated from the ratio of actual area to
required area as follows:
W = 84,000 x
The required orifice area.
4.34
= 98,796 lb/hr
3.69
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
26
Find:
The required orifice area and
approximate valve capacity.
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Sonic Flow (English Units)
Curve to Evaluate Napier Correction Factor KN for High Pressure
Dry Saturated Steam
1.200
1.190
1.180
1.170
1.160
KN =
1.150
where 1500 psig < P < 3200 psig
1.140
Napier Correction Factor, KN
0.1906 P - 1000
(10a)
0.2292 P - 1061
1.130
1.120
1.110
1.100
1.090
1.080
1.070
1.060
1.050
1.040
1.030
1.020
1.010
1.000
▲
1500
▲
1700
▲
1900
▲
2100
▲
2300
▲
2500
▲
2700
▲
2900
▲
3100
▲
3300
Steam Relieving Pressure, P1 (psig)
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
27
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Sonic Flow [Metric Units]
Curve to Evaluate Napier Correction Factor KN for High Pressure
Dry Saturated Steam
1.210
1.200
1.190
1.180
1.170
KN =
2.764 P - 1000
3.323 P - 1061
(10)
where 103.4 barg < P < 220.7 barg
1.160
Napier Correction Factor, KN
1.150
1.140
1.130
1.120
1.110
1.000
1.090
1.080
1.070
1.060
1.050
1.040
1.030
1.020
1.010
▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲
100 110 120 130 140 150 160 170 180 190 200 210 220 230
Steam Relieving Pressure, P1 (barg)
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
28
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Steam – Superheat Correction
Superheat Correction Factor (KSH) for Superheated Steam
Relieving
Pressure
psia [bara]
50
[3.4]
Total Steam Temperature °F [°C]
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200
[204] [232] [260] [288] [316] [343] [371] [399] [427] [454] [482] [510] [538] [566] [593] [621] [649]
.987
.957
.930
.905
.882
.861
.841
.823
.805
.789
.774
.759
.745
.732
.719
.708
.696
100
[6.9]
.998
.963
.935
.909
.885
.864
.843
.825
.807
.790
.775
.760
.746
.733
.720
.708
.697
150
[10.3]
.984
.970
.940
.913
.888
.866
.846
.826
.808
.792
.776
.761
.747
.733
.721
.709
.697
200
[13.8]
.979
250
[17.2]
.977
.945
.917
.892
.869
.848
.828
.810
.793
.777
.762
.748
.734
.721
.709
.698
.972
.951
.921
.895
.871
.850
.830
.812
.794
.778
.763
.749
.735
.722
.710
.698
300
[20.7]
.968
.957
.926
.898
.874
.852
.832
.813
.796
.780
.764
.750
.736
.723
.710
.699
350
[24.1]
.968
.963
.930
.902
.877
.854
.834
.815
.797
.781
.765
.750
.736
.723
.711
.699
400
[27.6]
.963
.935
.906
.880
.857
.836
.816
.798
.782
.766
.751
.737
.724
.712
.700
450
[31.0]
.961
.940
.909
.883
.859
.838
.818
.800
.783
.767
.752
.738
.725
.712
.700
500
[34.5]
.961
.946
.914
.886
.862
.840
.820
.801
.784
.768
.753
.739
.725
.713
.701
550
[37.9]
.962
.952
.918
.889
.864
.842
.822
.803
.785
.769
.754
.740
.726
.713
.701
600
[41.4]
.964
.958
.922
.892
.867
.844
.823
.804
.787
.770
.755
.740
.727
.714
.702
650
[44.8]
.968
.958
.927
.896
.869
.846
.825
.806
.788
.771
.756
.741
.728
.715
.702
700
[48.3]
.958
.931
.899
.872
.848
.827
.807
.789
.772
.757
.742
.728
.715
.703
750
[51.7]
.958
.936
.903
.875
.850
.828
.809
.790
.774
.758
.743
.729
.716
.703
800
[55.2]
.960
.942
.906
.878
.852
.830
.810
.792
.774
.759
.744
.730
.716
.704
850
[58.6]
.962
.947
.910
.880
.855
.832
.812
.793
.776
.760
.744
.730
.717
.704
900
[62.1]
.965
.953
.914
.883
.857
.834
.813
.794
.777
.760
.745
.731
.718
.705
950
[65.5]
.969
.958
.918
.886
.860
.836
.815
.796
.778
.761
.746
.732
.718
.705
1000
[69.0]
.974
1050
[72.4]
.959
.923
.890
.862
.838
.816
.797
.779
.762
.747
.732
.719
.706
.960
.927
.893
.864
.840
.818
.798
.780
.763
.748
.733
.719
.707
1100
[75.9]
.962
.931
.896
.867
.842
.820
.800
.781
.764
.749
.734
.720
.707
1150
[79.3]
.964
.936
.899
.870
.844
.821
.801
.782
.765
.749
.735
.721
.708
1200
[82.8]
.966
.941
.903
.872
.846
.823
.802
.784
.766
.750
.735
.721
.708
1250
[86.2]
.969
.946
.906
.875
.848
.825
.804
.785
.767
.751
.736
.722
.709
1300
[89.7]
.973
.952
.910
.878
.850
.826
.805
.786
.768
.752
.737
.723
.709
1350
[93.1]
.977
.958
.914
.880
.852
.828
.807
.787
.769
.753
.737
.723
.710
1400
[96.6]
.982
.963
.918
.883
.854
.830
.808
.788
.770
.754
.738
.724
.710
1450 [100.0]
.987
.968
.922
.886
.857
.832
.809
.790
.771
.754
.739
.724
.711
1500 [103.4]
.993
.970
.926
.889
.859
.833
.811
.791
.772
.755
.740
.725
.711
1550 [106.9]
.972
.930
.892
.861
.835
.812
.792
.773
.756
.740
.726
.712
1600 [110.3]
.973
.934
.894
.863
.836
.813
.792
.774
.756
.740
.726
.712
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
29
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Steam – Superheat Correction
Superheat Correction Factor (KSH) for Superheated Steam
Relieving
Pressure
psia [bara]
Total Steam Temperature °F [°C]
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200
[204] [232] [260] [288] [316] [343] [371] [399] [427] [454] [482] [510] [538] [566] [593] [621] [649]
1650 [113.8]
.973
.936
.895
.863
.836
.812
.791
.772
.755
.739
.724
.710
1700 [117.2]
.973
.938
.895
.863
.835
.811
.790
.771
.754
.738
.723
.709
1750 [120.7]
.974
.940
.896
.862
.835
.810
.789
.770
.752
.736
.721
.707
1800 [124.1]
.975
.942
.897
.862
.834
.810
.788
.768
.751
.735
.720
.705
1850 [127.6]
.976
.944
.897
.862
.833
.809
.787
.767
.749
.733
.718
.704
1900 [131.0]
.977
.946
.898
.862
.832
.807
.785
.766
.748
.731
.716
.702
1950 [134.5]
.979
.949
.898
.861
.832
.806
.784
.764
.746
.729
.714
.700
2000 [137.9]
.982
.952
.899
.861
.831
.805
.782
.762
.744
.728
.712
.698
2050 [141.4]
.985
.954
.899
.860
.830
.804
.781
.761
.742
.726
.710
.696
2100 [144.8]
.988
2150 [148.3]
.956
.900
.860
.828
.802
.779
.759
.740
.724
.708
.694
.956
.900
.859
.827
.801
.778
.757
.738
.722
.706
.692
2200 [151.7]
.955
.901
.859
.826
.799
.776
.755
.736
.720
.704
.690
2250 [155.2]
.954
.901
.858
.825
.797
.774
.753
.734
.717
.702
.687
2300 [158.6]
.953
.901
.857
.823
.795
.772
.751
.732
.715
.699
.685
2350 [162.1]
.952
.902
.856
.822
.794
.769
.748
.729
.712
.697
.682
2400 [165.5]
.952
.902
.855
.820
.791
.767
.746
.727
.710
.694
.679
2450 [169.0]
.951
.902
.854
.818
.789
.765
.743
.724
.707
.691
.677
2500 [172.4]
.951
.902
.852
.816
.787
.762
.740
.721
.704
.688
.674
2550 [175.9]
.951
.902
.851
.814
.784
.759
.738
.718
.701
.685
.671
2600 [179.3]
.951
.903
.849
.812
.782
.756
.735
.715
.698
.682
.664
2650 [182.8]
.952
.903
.848
.809
.779
.754
.731
.712
.695
.679
.664
2700 [186.2]
.952
.903
.846
.807
.776
.750
.728
.708
.691
.675
.661
2750 [189.7]
.953
.903
.844
.804
.773
.747
.724
.705
.687
.671
.657
2800 [193.1]
.956
.903
.842
.801
.769
.743
.721
.701
.684
.668
.653
2850 [196.6]
.959
.902
.839
.798
.766
.739
.717
.697
.679
.663
.649
2900 [200.0]
.963
.902
.836
.794
.762
.735
.713
.693
.675
.659
.645
2950 [203.4]
.902
.834
.790
.758
.731
.708
.688
.671
.655
.640
3000 [206.9]
.901
.831
.786
.753
.726
.704
.684
.666
.650
.635
3050 [210.3]
.899
.827
.782
.749
.722
.699
.679
.661
.645
.630
3100 [213.8]
.896
.823
.777
.744
.716
.693
.673
.656
.640
.625
3150 [217.2]
.894
.819
.772
.738
.711
.688
.668
.650
.634
.620
3200 [220.7]
.889
.815
.767
.733
.705
.682
.662
.644
.628
.614
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
30
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Liquid Flow
ASME VIII Liquids (Set Pressure ≥ 15 psig [1.03 barg])
U.S. Volumetric Flow
(gpm @ 10% overpressure)
Formula 5
–––
W√ G
A = –––––––––––––––––––––
––––––––––
38 K KvKw √1.10 P - P2
Metric Volumetric Flow
[m3/h @ 10% overpressure]
Formula 5M
–––
0.19631 W √ G
A = ––––––––––––––––––
–––––––––
K KvKw √1.10 P - P2
Liquids (Non ASME Certified)
U.S. Volumetric Flow (gpm)
Formula 6
–––
W√ G
A = –––––––––––––––––––
–––––
38 K KpKvKw √ P - P2
Metric Volumetric Flow [m3/h]
Formula 6M
–––
0.19631 W √ G
A = ––––––––––––––––
–––––
K KpKvKw √ P - P2
Reynolds Number Calculation
U.S. Volumetric Flow (gpm)
Formula 7
12,700 W
R = –––––––––
––
U √A
Metric Volumetric Flow [m3/h]
Formula 7M
31,313 WG
R = –––––––––––
––
µ √A
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
31
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Liquid Flow Viscosity Correction
(English)
Example 7
When a relief valve is sized for viscous liquid service, it is suggested that it be sized
first as for nonviscous-type application in
order to obtain a preliminary required discharged area, A. From manufacturers’
standard orifice sizes, the next larger orifice size should be used in determining
the Reynold’s number, R, from the following relationship:
12,700 W
R = ––––––––––
––
µ √ A1
Where:
W = required flow rate at the flowing temperature, in U.S. gallons per minute.
A1 = effective discharge area, in
square inches
U = viscosity at the flowing temperature,
in Saybolt Universal seconds.
After the value of R is determined, the
factor Kv is obtained from page 33. Kv is
applied to correct the ‘preliminary required discharge area.’ If the corrected
area exceeds the ‘chosen standard orifice
area,’ the above calculations should be
repeated using the next larger standard
orifice size.
Example:
Viscosity - SSU .......10,000 SSU @ 100°F
Required Capacity ......................300 GPM
Set Pressure.................................100 psig
Constant Back Pressure.................15 psig
Allowable Overpressure......................10%
Specific Gravity......................1.0 @ 100°F
Relieving Temperature .....................100°F
Step 1
–––
W√ G
A = –––––––––––––––––––––
––––––––––
38 K KvKw √1.10 P - P2
–––
300 √ 1.0
A = –––––––––––––––––––––
––––––––
38 (.776)(1) √1.10 - 15
A = 1.043
Preliminary Required Discharge Area
A1, Select Standard Orifice Area = 1.287 ‘J ’ Orifice
Step 2
12,700 x 300
R = –––––––––––––––
––––––
10,000 √ 1.287
R=
335.8
Step 3
R=
335.8 correction factor from chart
Kv =
0.815
Step 4
Corrected ‘Preliminary Required
A
Discharge Area’ = ––––
Kv
=
1.043
––––––
.815
= 1.279 in2
If corrected ‘Preliminary Required
Discharge Area’ is greater than selected
standard orifice area, select next orifice
size and repeat steps 2, 3, and 4. In this
example, the corrected orifice area is still
within the ‘J’ orifice and therefore is the
correct selection.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
32
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Liquid Flow
Curve to Evaluate Liquid Viscosity Correction Factor Kv
100,000
50,000
40,000
30,000
20,000
Reynolds Number, R
10,000
5,000
4,000
3,000
2,000
1,000
500
400
300
200
100
50
40
30
20
▲
0.20
▲
0.30
▲
0.40
▲
0.50
▲
0.60
▲
0.70
▲
0.80
▲
0.90
▲
1.00
Liquid Viscosity Correction Factor, KV
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
33
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Liquid Flow (English Units)
Examples for Liquid Applications
Solution:
Example 8 - ASME VIII Liquids
Use Formula 5
–––
69 √ G
A = –––––––––––––––––––
––––––––
38 K KvKw √1.1 P - P2
W
= 69
G
= 1.115
P
= 26
P2
= 4
Given: Ethylene Glycol, with a required
flow rate of 69 GPM, set at 26
psig, 10% overpressure, built-up
back pressure of 4 psig.
Find:
KV = 1
KW = 1
The required orifice area and the
orifice area to be selected.
––––––
.3865
69 √ 1.115
A = –––––––––––––––––––––––
––––––––– = –––––
38 K x 1 x 1 x √1.1(26) - 4
K
For Direct Spring D Series: K = .776
For POSRV: K = .670
For AGCO D Series: A = .3865 = 0.498, Select 11/2 G 21/2 (0.503 in2)
.776
For AGCO 400 Series POSRV: A = .3865 = 0.576, Select 11/2 H3 (0.785 in2)
.67
Solution:
Example 9
ASME
API
K for D Series = .700
K for D Series = .776
K for 400 Series = .650
K for 400 Series = .670
Compare the ASME vs API sizing coefficients for the data used in example 8.
This example illustrates two important
points to consider in valve sizing.
For D Series:
A=
1. Either ASME or API coefficients may be
used, but they may not be mixed. An
error results if the ASME area is used
with the API coefficient, and vice versa.
.3865
= .552, Select 11/2 G 21/2 (0.558 in2) = same orifice selection
.700
For 400 Series:
A=
.3865
= .594, Select 11/2 G 3 (0.599 in2) = smaller orifice may be selected
.650
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
34
2. Consider the selection of the 400
Series Pilot Operated PRV. Using averaged API coefficients actually would
result in specifying a larger orifice than
using the ASME actual data. When a
calculated orifice (using API data) is
very close to an orifice area selection,
a check using ASME actual data may
result in a smaller orifice.
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Liquid Flow [Metric Units]
Examples for Liquid Applications
Example 10
Solution:
Given: Water with a required flow rate
of 50.0 m3/h, set at 10.0 barg,
10% overpressure, built-up
back pressure of 2.0 barg.
Use formula 5M and the physical properties found on pages 51-63.
Find:
The required orifice area for a
Type 81P balanced pressure relief
valve and the orifice area selected.
P
G
Kp
Kw
= 10 barg
= 1.00
= 1.00
= 1.00
p 2 = 2 barg
K = 0.720
Kv = 1.00
–––––
0.19631 x 50 x √ 1.00
2
A[cm2] = ––––––––––––––––––––––––––––––––––
––––––––– = 4.54 cm
0.720 x 1.00 x 1.00 x 1.00 x √1.1(10) - 2
From page 11, the next available orifice, greater than this is 8.303 cm2, corresponding to
a ‘J’ orifice.
Example 11
Solution:
Given: Same as example 10.
The same data is used as in example 10, except use a nozzle coefficient K = 0.776 (from
page 8), in formula 5M. The values of Kp, Kv and Kw = 1.00 for this application.
Find:
The appropriate size valve for a
D Series pressure relief valve,
suitable for liquid service.
A[cm2]
–––––
0.19631 x 50 x √ 1.00
2
= ––––––––––––––––––––––––––––––
––––– = 4.216 cm
.776 x 1.00 x 1.00 x 1.00 x √11 - 2
From page 10, the next available larger area is 5.065 cm2, corresponding to an ‘H’ orifice.
Example 12
Solution:
Given: A liquid with a required flow rate
of 72 m3/h, set at 6.5 barg, 10%
overpressure, a relative density of
0.95, viscosity of 450 centipoise, a
back pressure of 0.75 barg.
Use formula 5M and make any adjustment for the effect of viscosity if necessary.
Find:
The required valve size for a
Series 400 pilot operated pressure
relief valve. Use API coefficients.
P = 6.5 barg
K = 0.650
Kw = 1.00
p2 = 0.75 barg
Kp = 1.00
Kv = 1.00 for initial sizing calculation, then
evaluated in subsequent calculation as explained on page 28.
–––––
0.19631 x 72 x √ 0.95
2
A[cm2] = –––––––––––––––––––––––––––––––––––––
––––––––––– = x 8.127 cm
0.670 x 1.00 x 1.00 x 1.00 x √1.1(6.5) - .75
From page 13, the next larger, available orifice area is 8.30 cm2.
This preliminary orifice area is then used to determine a value for Kv. Calculate R from
formula 7M on page 31.
31,313 x 72 x 0.95
R = –––––––––––––––––
= 1652
–––––
450 √ 8.30
From page 33, Kv = 0.925
8.127
Atrial = –––––– = 8.78 cm2
0.915
This is larger than the preliminary orifice A therefore the next larger orifice must be selected
and re-evaluated. The new preliminary orifice is 11.86 cm2. Calculate a new R.
31,313 x 72 x 0.95
R = ––––––––––––––––
= 1382
–––––
450 √ 11.86
From page 33, Kv = 0.925
8.127
Atrial = –––––– = 8.88 cm2 which confirms the selection of a type 423 3K4 size.
0.925
This result is smaller than our last preliminary orifice area of 11.86 cm2, which therefore is
satisfactory for the application. Orifice designation ‘K’ is the appropriate choice.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
35
Anderson Greenwood Pressure Relief Valves
Technical Manual
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
36
Anderson Greenwood Pressure Relief Valves
Technical Manual
Subsonic Flow API 2000 and Open Discharge Valves
Without Kb Factor
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
37
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Subsonic Flow per API RP 520
Note
Gas Flow - Direct Spring Valves with ASME K coefficient1
(Set Pressure < 15 psig [1.03 barg])
U.S. Weight Flow (lb/h)
Formula 8
A(in2)
W
= –––––––
735 F2K
Metric Weight Flow [kg/h]
Formula 8M
––––––––––––
ZT
––––––––––––
MP1(P1 - P2)
√
U.S. Volumetric Flow (scfm)
Formula 9
A(in2)
F2 =
––––
V √MTZ
= ––––––––––––––––––––––
––––––––––
4645.2 F2K √ P1(P1 - P2)
A[cm2]
––––
W √ TZ
= ––––––––––––––––––––––
––––––––––––
2087 F2K √ MP1(P1 - P2)
Metric Volumetric Flow [Nm3/h]
Formula 9M
A[cm2]
–––––
V √ MTZ
= ––––––––––––––––––––––
–––––––––––
4892 F2K √ P1 (P1 - P2)
–––––––––––––––––––––––
2
(k - 1)
(––) 1 - r k
k
––– r k ––––––––
k-1
1-r
√(
)
[
]
k = ratio of specific heats
r=
P2
P1
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
38
1. Applicable for conventional valves set at
pressures below 15 psig [1.03 barg], or
when the ratio of back pressure to inlet
pressure (P2/P1) exceeds the critical pressure ratio (PCF/P1). For balanced bellows
valves that operate in the subsonic flow
region, the sonic flow equations should be
used with a back pressure correction factor
(Kb) particular to this application.
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Subsonic Flow per API RP 520
Examples for Gas Applications
Solution:
Example 13 (English Units)
Given: Methane, with a required flow
rate of 1500 scfm, set at 19 psig,
flows into a header where the
back pressure is 9 psig. The gas
temperature is 120°F.
Find:
The required orifice area.
Using formula 9 from page 38:
––––
W √MTZ
A = ––––––––––––––––––––––
––––––––––
4645.2 F2K √ P1(P1 - P2)
V = 1500
P1 = 19 (3 + 14.7) = 36.7
P2 = 9 + 14.7 = 23.7
K = 0.971 (AGCO D Series)
r
M = 16.04
k
= 1.31
T
= 120 + 460 = 580°R
Z
= 1.00
= P2/P1 = 23.7/36.7 = 0.6457
F2 =
F2 =
––––––––––––––––––––––––––––––––––––
2
.31
(–––) 1 - .6457 (1.31)
1.31
–––– 0.6457 1.31 ––––––––––––
.31
1 -.6547
√(
√
[
)
]
–––––––––––––––––––––––––––
1 - .9016
4.2258 x .5128 ––––––––
.3543
[
]
F2 = .7757
A =
–––––––––––––
1500 √ 16.04 x 580 x 1
2
–––––––––––––––––––––––––––––––––––
––––––––––––––– = 1.893 in
4645.2 x .7757 x .971 √ 36.7 (36.7 - 23.7)
Example 14 (Metric Units)
Solution:
Given: Air, at .78 barg and -15°C, with a
required flow rate of 195 Nm3/h,
requires a pressure relief valve for
protection. The valve is to be installed at 2,000 meters above sea
level.
Using formula 9M from page 38:
A =
Find:
At 2000 M above sea level, the barometric
pressure is 0.793 bara.
The required valve size. Also,
determine the error using the standard sonic formula for the same
conditions given.
V = 195
M = 29
––––
V √MTZ
–––––––––––––––––––––
––––––––––
4892 F2K √ P1(P1 - P2)
T
= -15 + 273 = 258
Z
= 1
K = 0.971
P1 = .78 + .2069 + .793 = 1.779 bara
P2 = 0.793
= P2/P1 = .793/1.779 = .5227
–––––––––––––––––––––––––––––
2
.4
(–– ) 1 - r (1.4 )
1.4
F2 =
––– .5227 1.4 –––––––
.4
1-r
r
F2 =
√(
√
[
)
]
––––––––––––––––––––––––
1 - .8308
3.5 x .3958 ––––––––
1 - .5227
[
]
F2 = .7007
A =
–––––––––––
195 √ 29 x 258 x 1
2
––––––––––––––––––––––––––––––––––––
––––––––––––––––– = 3.826 cm
4892 x .7007 x .971 √ 1.779 (1.779 - .793)
Therefore, the correct valve size would be 11/2H3 (5.064 cm2). Had the standard sonic
sizing formula been used, the orifice calculation would have been as follows:
––––
––––––––––
V √MTZ
195 √29 x 258 x 1
A = –––––––––––––––
A = –––––––––––––––––––––––––––– = 1.603 cm2
17.02 CKdP1Kb
17.02 x 356 x 971 x 1.779 x 1.00
The resultant error would be the selection of an undersized valve (11/2 F2, with 1.98 cm2).
This would create a condition where the pressure relief valve could not control the design
overpressure transients.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
39
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing1 – Subsonic Flow per API RP 2000
Pilot Operated PRV Types 91, 93, 94, 95, 9200 and 9300
(Set Pressure < 15 psig [1.03 barg])
U.S. Weight Flow (lb/h)
Formula 10
A(in2)
1. A computer sizing program is available.
Consult your local representative.
Metric Weight Flow [kg/h]
Formula 10M
–––
W√ TZ
= –––––––––––––––
–––
735 KdP1F √ M
A[cm2]
U.S. Volumetric Flow (SCFM)
Formula 11
A(in2)
Note
–––––
V√ MTZ
= –––––––––––
4645 KdP1F
–––
W√ TZ
= –––––––––––––––
–––´
558 KdP1F √ M
Metric Volumetric Flow [Nm3/h]
Formula 11M
A[cm2]
–––––
V√ MTZ
= ––––––––––––
12510 KdP1F
where:
F =
–––––––––––––––––––––––––––––––
2
P2 k + 1
k
P 2 ––
––––
–––– k –
––– ––––
k
k-1
P1
P1
√
[(
)
( )
]
Coefficients of Discharge
For Type 9200 Kd = 0.756 (P1)0.0517
US units. See page 42.
For Type 9200, Kd = 0.8681 (P1)0.0517
Metric units. See page 42.
For Type 9300 Kd = 0.650 (P2/P1)-0.349
See page 42.
For Type 9200 Vacuum Kd = 0.667.
For Type 9300 Vacuum Kd = 0.55.
For Types 91, 94, 95 Kd = 0.678 (P2/P1)-0.285
For Type 93 Kd = 0.700 (P2/P1)-0.265
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
40
Anderson Greenwood Pressure Relief Valves
Technical Manual
Sizing - Series 90 and 9000
.100
.990
.995
1.000
Flow Correction Factor F (For use in subsonic sizing page 39)
.095
.090
.550
1.90
.085
.525
1.70
1.60
1.50
1.40
.080
.075
.065
.060
thru 1.90
.450
1.10
1.00
.425
.400
.375
k=
1.9
0
.055
.350
0
.050
.325
k=
1.0
.045
.040
.300
.035
.275
.030
.250
.225
.200
thru 1.90
.175
k = 1.00
.150
.125
Absolute Pressure Ratio
.400
.450
.500
.550
.600
.650
.700
.750
.800
.850
.900
.950
.100
1.000
.990
F
.475
1.30
1.20
k = 1.00
.070
.500
( )
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
P2
P1
41
F
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Subsonic Flow
Type 9200 Valve Coefficient (Kd) vs. Relief Pressure
Notes (Type 9200 only)
.90
1. P = set pressure + overpressure - inlet piping loss + atmospheric pressure (psia).
Valve Coefficient (Kd )
.85
2. P = set pressure + overpressure - inlet piping loss + atmospheric pressure (barg).
.80
.75
English Units = Kd = 0.756 (P) .0517 1
Metric Units = Kd = 0.756 (P x 14.50)
.70
.0517 2
.65
.60
0
.5
0
1
1.5
.05
2
1
2.5
3
.15
3.5
2
4
4.5
.25
5 psig
.3
.35 barg
Flowing Pressure (P)
Type 9300 Valve Coefficient (Kd) vs. Absolute Pressure Ratio
Valve Coefficient (Kd )
.90
.85
Kd = 0.650
.80
( )
P2
-.349
P1
.75
.70
.65
.60
.50
.55
.60
.65
.70
.75
.80
Absolute Pressure Ratio
.85
.90
.95
1.00
( )
P2
P1
Types 91 and 94 Valve Coefficient (Kd) vs. Absolute Pressure Ratio
.85
.83
Valve Coefficient (Kd)
.81
Kd = .678
.79
( )
P2
-.285
P1
.77
.75
.73
.71
.69
.67
.65
.50
.55
.60
.65
.70
.75
Absolute Pressure Ratio
.80
.85
.90
.95
1.00
( )
P2
P1
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
42
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Subsonic Flow
Type 93 Valve Coefficient (Kd) vs. Absolute Pressure Ratio
.85
.83
Valve Coefficient (Kd)
.81
Kd = .700
.79
( )
P2
-.265
P1
.77
.75
.73
.71
.69
.67
.65
.50
.55
.60
.65
.70
.75
.80
Absolute Pressure Ratio
.85
.90
.95
1.00
( )
P2
P1
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
43
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Subsonic Flow (English)
Examples for Gas Applications
Example 15
Solution:
Find: Using the same conditions as stated in Example 13, size for a Type
9300 pilot operated pressure relief
valve.
Using formula 11 from page 40:
––––
V √ MTZ
A = ––––––––––––
4645 K d P1F
P
___2 =
P1
0.6458
______________
√
F=
k
____
k-1
[(
2
___
P2
___
P1
k
k +1
____
P2
___
P1
) ( )
–
k
]
_____________
√
F=
1.27
___
.31
[
2
___
1.31
2.27
____
1.31
(.6458) – (.6458)
]
F = 0.4616
Kd = 0.650
K = 0.7572
–––––––––––––
1500 √ 16.04 x 580 x 1
A = –––––––––––––––––––––
(4645) (.7572) (36.7) (.4616)
A = 2.4282 in2
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
44
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Special Applications
Thermal Relief, Fire and
Special Water
Example:
Step 2
From equation (14)
Detailed requirements for fire sizing of pressure relief devices are
contained in API RP520 Part I. A
summary of sizing equations is
given below.
What is the total heat input, in BTU/h,
to a vertical distillation column 8 feet in
diameter by 50 feet long with flat ends,
mounted 4 feet above ground and
insulated to provide 6 BTU/h x ft x °F
conductance with a 1600°F temperature
difference? 2
Heat absorption (Q) into a vessel is determined by equation (13).
Step 1
Where: P = relieving pressure =
Q = 21,000 FA 0.82
(Set Pressure x 1.10) + 14.7
6
F = –––––
13.33
(70 – 14.7)
Set Pressure = ––––––––– 50 psig
1.10
(13) Q = 21,000 FA 0.82
Where:
= 0.45
A = wetted surface area of the vessel, in
square feet.
A=
F = an insulation factor. F = 1.0 for an
uninsulated vessel corresponding to a
heat conductance of 13.33 BTU/h x ft 2 x
°F with a 1600°F temperature difference.
Where: h equals 25 ft max. minus the
height above the ground.
F = Actual Conductance (BTU/h x ft 2 x °F)
13.33
For horizontal pressure vessels, use total
area in square feet. For vertical vessels,
use the area up to 25 feet above ground.
For spherical vessels, use height above
ground of maximum diameter or 25 feet,
whichever is greater.
Once the heat input (Q) is determined – in
BTU/h from equation (13) – gas flow rate
must be determined from the latent heat
of the fluid medium. The rate of change
from liquid to vapor, or vaporization rate,
is a function of both the fluid’s physical/
chemical properties and the relieving
pressure value. The vapor mass flow rate,
lbs/hr, (Wp) is derived from equation (14).
( ––π4 ) D
2
+ (h x πD)
Q
1,738,800
Wp = ––– = ––––––––– = 14,490 lbs/h
L
120
Step 3
P = 70 psia
Determine required orifice area (A) as
follows:
Step 4
A =
A=
–––––– ) 8
( 3.1416
4
2
+ (25 - 4) 3.1416 x 8
A = 50.27 ft 2 + 527.79 ft 2
A = 578.06 ft 2
Wp
–––––––
CKdPFp
√
T
––––––––––––
1 x (400 + 460)
–––––––––––
60
√
14,490
A = ––––––––––––––––
315 x 0.971 x (70) x 1
Q = 21,000 (0.45) (578.06)0.82
Q = 21,000 (0.45) (184)
––––
Z
––
A = 2.562 in2
Q = 1,738,800 BTU/h
Step 5
Example:
Select orifice just in excess of 2.562 in2,
orifice L at 2.853 in2.
If the vessel contains a liquid with a latent
heat of 120 BTU/lb at 70 psia, 400°F and
molecular weight of 60, what is the required valve capacity and set pressure?
Q
(14) Wp = ––– (lbs/h)
L
Where:
Wp = the flow rate in lbs/h
Notes
Q = the maximum heat input in BTU/h
from equation (13).
1. Thermal properties of the specific fluid
should be obtained from appropriate
sources.
L = minimum latent heat of vaporization1,
BTU/lb, at the absolute relieving
pressure (psia).
2. For vessels with other than flat ends, use the
appropriate equations for surface area of the
ends.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
45
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Special Applications
Valve Sizing for Saturated High
Temperature Liquids which Flash
to Vapor at Relief Conditions.
From the required flow rate, derive the
vapor flow and liquid flow from equations
as follows:
As a hot liquid suddenly increases in
volume, such as in flow through a pressure relief valve, part of it expands to
vapor or ‘flashes.’ Under these conditions
the required flow area for the pressure relief valve is greater than that required for
liquid alone. Since enthalpy, or total energy, in the fluid remains constant, and
since fluid properties1 are available at saturated liquid and saturated vapor
conditions, the amount of liquid which
flashes to vapor can be calculated using
equation (15).
Vapor flow:
H1 - H2
(15) % of Flash = –––––––
HFg
x (100%)
Where:
H1 is the maximum enthalpy at the relieving absolute pressure;
H2 is the enthalpy of saturated liquid at
sonic flow conditions occurring in the
nozzle; and HFg is the latent heat of
vaporization, or the difference in enthalpy
between vapor and liquid states. See
Enthalpy graph on page 46.
The set pressure (P1) is the accumulated
absolute pressure plus the overpressure.
The sonic flow pressure, also called the
critical pressure, is obtained by using the
fluid’s specific heat ratio (k)1 as a term in
the following equation.
Pcp = P1
( )
2
–––––
k+1
k
––––
k-1
If k is not known, Pcp
P1
= ––––
2
% Flash
(16) Wp = ––––––– x Reg. Capacity2 (lbs/h)
100
Determine As and Aw required area for
steam and water, respectively.
Wp
As = –––––––––––
51.5 KP1Ksh
2731
As = ––––––––––––––––––– = 0.188 in2
51.5 x 0.971 x 289.7 x 1
Liquid flow:
(Required Capacity - Wp)
(17) W = ––––––––––––––––––––– gpm
500 x G
G is the specific gravity of the liquid.
–––
W√ G
Aw = –––––––––––––––––––––
–––––––––––
38 K Kv Kw √1.1 P1 - P2
Combine the required flow area values for
vapor and liquid and use that value in the
area equations on pages 7 and 8. Select
the valve orifice area which just exceeds
the required combined area.
–––––
384√ 0.892
Aw = –––––––––––––––––––––––––––
–––––––––––
38 x .776 x 1 x 1 x √1.1 (250) - 0
Example of sizing or flashing service
conditions:
Aw = .7416 in2
Set Pressure P
= 250 psig
Required Capacity W
= 74,000 lbs/h
Thus, total required area, A, is:
Temperature T
= 380°F
A = As + Aw = 0.188 + 0.742 = 0.930 in2
Accumulation
= 10%
Select orifice 1.287 in2, orifice J .
P1= 250 x 1.1 + 14.7
= 289.7 psia
Pcp = 289.7 x 0.58
= 168 psia
H1 (380°F liquid)
= 353.6 BTU/lb
H2 (sat. liquid @ 168 psia) = 340.2 BTU/lb
HFg (latent heat @ 168 psia) = 855.6 BTU/lb
G (specific gravity) @ 168 psia = .892
W - liquid capacity
Notes
H1 - H2
% of Flash = –––––––– x (100%)
HFg
1. Thermal properties of the specific fluid
should be obtained form appropriate
sources.
353.6 - 340.2
––––––––––– x (100%) = 1.57%
855.6
2. The required capacity is given for the
application by process requirements.
WP = 0.0157 x 174000 = 2731 lbs/h, steam
WG = 174000 - 2731 = 171269 lbs/h, water
lbs/h, water
171269
WG = –––––––––– = –––––––– = 384 gpm
500 x G
500 x 0.892
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
46
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Special Applications
Reference Specifications
Special Water Sizing Enthalpy Graph
Critical Point
T1
P1
H1
T2
P2
Hpg
Sa
tur
Liq ated
uid
d
te
ra
tu
Sa ap
V
P – Pressure, PSIA
H2
or
H (Enthalpy), BTU/Lb.
Notes
Standards – Sources
ANSI
American National Standards
Institute
Terminology for pressure relief devices:
ANSI B95. 1-1977
API
American Petroleum Institute
ASME
American Society of Mechanical
Engineers
Sample pressure relief valve specification
sheet:
API–STD-526
NFPA
National Fire Protection
Association
Guide for operating differentials:
ASME Section VIII, APP. M
Fire Sizing:
API-RP-520, Part I
NFPA No. 58
Overpressure Boilers:
Pressure Vessels:
ASME Section I, Par. PG-72
ASME Section VIII, Par. UG - 125
Installation Boiler:
Pressure Vessels:
ASME Section I, Par. PG-71
ASME Section VIII, Par. UG-135
And Appendix M.
API-RP-520, Part II
Commercial Seat Tightness:
API-STD-527
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
47
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Sizing – Reaction Forces
Reaction Forces – Vapors and Gases
The discharge from a pressure relief valve
exerts a reaction force on the valve or
outlet piping. If the discharge piping is
unsupported, this force is transmitted to
the valve inlet and associated piping. The
following formula or chart may be used
to determine the reaction force. It is assumed that critical flow of the gas or vapor
is obtained at the valve outlet. Under conditions of sub-critical flow, the reaction
force will be less than that calculated.
The chart is based on a value of k = 1.4.
This will provide a conservative value for
the reaction force for most applications.
However, if more accurate results are
desired, the reaction forces can be determined by the following formula (18):
–––––––––
kT
–––––––
(k
+ 1)M + Ao x P2
W
(18) F = –––––––––––––––
366
√
(
)
F = reaction force at the point of discharge to the atmosphere, in
pounds (newtons)
W = flow of any gas or vapor, in pounds
per hour (kilograms per second)
k
= ratio of specific heats (Cp/Cv)
Cp = specific heat at constant pressure
Cv = specific heat at constant volume
T = temperature at inlet, in degrees
Rankine (degrees Fahrenheit + 460)
M = molecular weight of the process fluid
Ao = area of the outlet at the point of discharge, in square inches (square
millimeters)
P2 = static pressure at the point of discharge, in pounds per square inch
gauge (bar gauge)
Reference: API RP 520, Part II
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
48
Anderson Greenwood Pressure Relief Valves
Technical Manual
Conversion Factors
Notes
This table may be used in two ways:
1. Multiply the unit under column A by the
figure under column B; the result is the
unit under column C.
2. Divide the unit under column C by the figure
under column B; the result is the unit under
column A.
Equivalents and Conversion Factors
A
Multiply
B
By
Atmospheres
14.697
Pounds per in2
Atmospheres
1.033
Kilograms per cm2
Atmospheres
29.92
Inches of mercury
Atmospheres
760
Millimeters of mercury
Atmospheres
407
Inches of water
Atmospheres
33.90
Barrels (petroleum)
Barrels per day
Bars-G
42
0.0292
14.5
C
To Obtain
Feet of water
Gallons
Gallons per minute
Pounds per in2
Centimeters
0.3937
Inches
Centimeters
0.03281
Feet
Centimeters
0.01
Meters
Centimeters
0.01094
Yards
Cubic centimeters
0.06102
Cubic inches
Cubic feet
7.48055
Gallons
Cubic feet
0.17812
Barrels
Cubic feet per second
448.833
Gallons per minute
Cubic inches
16.39
Cubic centimeters
Cubic inches
0.004329
Gallons
Cubic meters
264.17
Gallons
Cubic meters per hour
4.4
Gallons per minute
Feet
0.3048
Meters
Feet
0.3333
Yards
Feet
30.48
Centimeters
Feet of water
0.882
Inches of mercury
Feet of water
0.433
Pounds per in2
Gallons (U.S.)
3785
Cubic centimeters
Gallons (U.S.)
0.13368
Gallons (U.S.)
231
Cubic inches
Gallons (Imperial)
277.4
Cubic inches
Gallons (U.S.)
0.833
Gallons (Imperial)
Gallons (U.S.)
3.785
Liters
Gallons of water
8.328
Pounds (at 70°F)
Gallons of liquid per minute
500 x Sp. Gr.
Gallons per minute
0.002228
Horsepower (boiler)
34.5
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
Cubic feet
Pounds per hr. liquid (at 70°F)
Cubic feet per second
Pounds water per hr. evaporation
49
Anderson Greenwood Pressure Relief Valves
Technical Manual
Conversion Factors
Notes
Equivalents and Conversion Factors
A
Multiply
B
By
Horsepower (boiler)
33479
BTU per hour
Inches
2.54
Centimeters
Inches
0.0833
Feet
Inches
0.0254
Meters
Inches
0.02778
Yards
Inches of mercury
1.133
Feet of water
Inches of mercury
0.4912
Pounds per in2
Inches of mercury
0.0345
Kilograms per cm2
Inches of water
0.03613
Pounds per in2
Inches of water
0.07355
Inches of mercury
Kilograms
2.205
Kilograms
0.001102
132.3
Pounds per hour
14.22
Pounds per in2
Kilograms per cm2
0.9678
Atmospheres
Kilograms per cm2
28.96
Inches of mercury
Kilopascals
.145
Pounds per in2
1000
0.2642
Cubic centimeters
Gallons
Liters per hour
0.0044
Gallons per minute
Meters
3.281
Feet
Meters
1.0936
Meters
100
Meters
39.37
Megapascals
Metric Ton
145
1000
Pounds
0.0005
Yards
Centimeters
Inches
Pounds per in2
Kilogram
Short tons (2000 lbs.)
Pounds
0.4536
Kilograms
Pounds
0.000454
Metric tons
Pounds
16
Pounds per hour
Pounds per hour liquid
6.32/M.W.
0.002/Sq. Gr.
Ounces
Cubic feet per minute
Gallons per minute liquid (at 70°F)
Pounds per in2
27.684
Inches of water
in2
2.307
Feet of water
Pounds per in2
2.036
Inches of mercury
in2
0.0703
Kilograms per cm2
Pounds per in2
51.71
Millimeters of mercury
Pounds per
Pounds per
2. Divide the unit under column C by the figure
under column B; the result is the unit under
column A.
Short tons (2000 lbs.)
Kilograms per cm2
Liters
1. Multiply the unit under column A by the
figure under column B; the result is the
unit under column C.
Pounds
Kilograms per minute
Liters
This table may be used in two ways:
C
To Obtain
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
50
Anderson Greenwood Pressure Relief Valves
Technical Manual
Conversion Factors
Equivalents and Conversion Factors
A
Multiply
Pounds per in2
B
By
C
To Obtain
0.7037
Meters of water
Specific Gravity (of gas or vapors)
28.97
Molecular wt. (of gas or vapors)
Square centimeters
0.1550
Square inches
Square inches
6.452
Square centimeters
Tons (short ton, 2000 lbs)
907.2
Kilograms
Tons (short ton, 2000 lbs.)
1.102
Metric tons
Tons (metric) per day
91.8
Pounds per hour
Water (cubic feet)
62.3
Pounds (at 70°F)
Yards
0.9144
Meters
Yards
91.44
Centimeters
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
51
Anderson Greenwood Pressure Relief Valves
Technical Manual
Conversion Factors
Pressure Conversions1
Given
To Find
(To find desired value, multiply ‘Given’ value by factor below)
mm Hg
in wc
oz
kPa
in Hg
psig
mm wc
mb
–––
0.0980
0.735
0.0394
0.0227
0.00980
0.00290
10.21
––––
0.750
0.4019
0.2320
0.1000
mm Hg
(mm Mercury)
(32°F or 0°C)
13.61
1.333
––––
0.5358
0.3094
in wc
(in. water column)
(60°F or 15.6°C)
25.40
2.488
1.866
––––
oz (oz/in2)
43.99
4.309
3.232
kPa (kilopascal)
102.1
10.00
in Hg (in. Mercury)
(60°F or 15.6°C)
344.7
mm wc
(mm water column)
(60°F or 15.6°C)
mb (millibars)
kg/cm2
bars
0.001421
1
10010
1
10207
0.0296
0.01450
0.00102
0.00100
0.1333
0.03948
0.01934
0.00136
0.00133
0.5775
0.2488
0.0737
0.03609
0.00254
0.00249
1.732
––––
0.4309
0.1276
0.0625
or 1/16
0.00439
0.00431
7.501
4.019
2.321
––––
0.2961
0.1450
0.0102
0.0100
33.77
25.33
13.57
7.836
3.377
––––
0.4898
0.0344
0.0338
2
psig (lbs/in2)
703.8
68.95
51.72
27.71
16.00
6.895
2.042
––––
0.0703
0.0689
kg/cm2 (kg/cm2)
10010
980.7
735.6
394.1
227.6
98.07
29.04
14.22
––––
0.9807
bars
10207
1000
750.1
401.9
232.1
100.0
29.61
14.50
1.020
––––
3
Notes
1. When pressure is stated in liquid column
height, conversions are valid only for listed
temperature.
2. Also expressed as torr.
3. Also expressed as kp/cm2 and kgf/cm2.
4. Normal Temperature and Pressure, (NTP)
conditions, are at sea level, equal to 1.013
bars (absolute) or 1.033 kg/cm2 a (kilograms
force per square centimeter absolute) at
base temperature of 32°F [0°C]. This differs
slightly from Metric Standard conditions,
(MSC), which uses 15°C for the base temperature.
Inch-Pound Standard Conditions are at sea level,
equal to 14.7 psia (pounds force per square
inch absolute), rounded from 14.696 psia, at a
base temperature of 60°F [15.6°C].
Temperature conversion:
If °F is known, to find °C: °C = (°F/1.8)-17.78
If °C is known, to find °F: °F = (°C+17.78)1.8
Example: Temperature is -20°C, find °F:
F = (-20+17.78)1.8 = -2.22 x 1.8 = -4°F
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
52
Anderson Greenwood Pressure Relief Valves
Technical Manual
Conversion Factors
Notes
M = molecular weight of gas.
Gas Flow Conversions
Given
To Find
(To find desired value, multiply ‘Given’ value by factor below)
scfm
scfh
lb/h
kg/h
Nm3/h
Nm3/min
scfm1
––––
60
M
6.32
M
13.93
1.608
0.0268
scfh1
0.01677
––––
M
379.2
M
836.1
0.0268
0.000447
lb/h2
6.32
M
379.2
M
––––
0.4536
10.17
M
0.1695
M
kg/h3
13.93
M
836.1
M
2.205
––––
22.40
M
0.3733
M
Nm3/h4
0.6216
37.30
M
10.17
M
22.40
––––
0.01667
Nm3/min4
37.30
2238
5.901 M
2.676 M
60
––––
1. Volumetric flow (per time unit of hour or
minute as shown) in standard cubic feet
per minute at 14.7 psia, 60°F.
2. Weight flow in pounds per hour.
3. Weight flow in kilograms per hour.
4. Volumetric flow (per time unit of hour or
minute as shown) at 1.013 bars absolute,
0°C. This represents the commercial standard, known as the Normal Temperature
and Pressure (NTP).
Conversions from volumetric to volumetric
or to weight flow (and vice versa) may
only be done when the volumetric flow is
expressed in the standard conditions
shown above. If flows are expressed at
temperature or pressure bases that differ
from those listed above, they must first be
converted to the standard base.
If flow is expressed in actual volume, such
as cfm (cubic feet per minute) or acfm (actual cfm) as is often done for compressors,
where the flow is described as displacement or swept volume, the flow may be
converted to scfm as follows (or from flow
expressed in m3/h to Nm3/h).
Inch-Pound Units
14.7 + p
520
scfm = (cfm or acfm) x ––––––– x ––––––
14.7
460 + t
Where:
p = gauge pressure of gas in psig
t = temperature of gas in °F
cfm or acfm = displacement or swept volume in cubic feet or actual cubic feet per minute
Metric Units
1.013 + p
273
Nm3/h = m3/h x –––––––– x ––––––
1.013
460 + 1
Where:
p = gauge pressure of gas in barg
t = temperature of gas in °C
m3/h = displacement or swept volume in cubic meters/hour
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
53
Anderson Greenwood Pressure Relief Valves
Technical Manual
Conversion Factors
Note
Liquid Flow Conversions
Given
l/h
liters/hour
To Find
(To find desired value, multiply ‘Given’ value by factor below)
l/h
gpm (US)
gpm(Imp)
barrels/day
m3/h
––––
0.00440
0.003666
0.1510
0.0010
0.8327
34.29
0.2271
gpm (US)
US gallons per
227.1
––––
––––
272.8
1.201
––––
41.18
0.2728
6.624
0.02917
0.02429
––––
0.006624
1000
4.403
3.666
151.0
––––
3.6 x 106
15.850
13.200
543.400
3600
1
G
1
227.1G
1
272.8G
0.151
G
1
1000G
minute
gpm (Imp)
Imperial gallons
per minute
barrels/day
(petroleum)
(42 US gallons)
m3/h
cubic meters per hour
m3/s
cubic meters per second
kg/h
kilograms per hour
lb/h
pounds per hour
1
1
1
1
1
2.205G
500.8G
601.5G
14.61G
2205G
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
54
G = relative density of liquid at its relieving
temperature to that of water at 68°F [20°C],
where Gwater = 1.00.
Anderson Greenwood Pressure Relief Valves
Technical Manual
Conversion Factors
Viscosity Units and Their
Conversion
When a correction for the effects of
viscosity in the liquid orifice sizing
formula is needed, the value of viscosity,
expressed in centipoise, is required. Since
most liquid data for viscosity uses other
expressions, a convenient method for
conversion is presented below.
The viscosity, µ (Greek mu), in centipoise,
is correctly known as absolute or dynamic
viscosity. This is related to the kinematic
viscosity expression, ν (Greek nu), in centistokes as follows:
µ (absolute viscosity, centipoise) =
ν (kinematic viscosity, centistokes) x
ρ (density, grams/cm3)
The liquid sizing formula uses the relative
density, G, where G = ρliquid / ρwater and
where the density of water is accepted (for
this manual) as 1g/cm3. The value of G
then becomes the density in g/cm3.
Substituting G for ρ (Greek rho) in the formula above, gives:
µ = ν x G (22),
where:
µ = absolute viscosity, centipoise
ν = kinematic viscosity, centistokes
G = relative density (water = 1.00)
Most other viscosity units in common
usage are also kinematic units and can be
related to the kinematic viscosity in centistokes, via the accompanying table. To use
this table, obtain the viscosity from data
furnished. Convert this to ν, in centistokes,
then convert to absolute viscosity µ, in
centipoise.
The conversions are approximate but
satisfactory for viscosity correction in
liquid safety valve sizing.
Viscosity Conversion Table
Seconds
Viscosity
Centistokes
ν
Seconds
Saybolt
Universal
ssu
Seconds
Saybolt
Furol
ssf
Seconds
Redwood1
(standard)
Seconds
Redwood2
(Admiralty)
1.00
31
29.0
2.56
35
32.1
4.30
40
36.2
5.10
7.40
50
44.3
5.83
10.3
60
52.3
6.77
13.1
70
12.95
60.9
7.60
15.7
80
13.70
69.2
8.44
18.2
90
14.4
77.6
9.30
20.6
100
15.24
85.6
10.12
32.1
150
19.30
128.0
14.48
43.2
200
23.5
170.0
18.90
54.0
250
28.0
212.0
23.45
65.0
300
32.5
254.0
28.0
87.60
400
41.9
338.0
37.1
110.0
500
51.6
423.0
46.2
132.0
600
61.4
508.0
55.4
154.0
700
71.1
592.0
64.6
176.0
800
81.0
677.0
73.8
198.0
900
91.0
462.0
83.0
220.0
1000
100.7
896.0
92.1
330.0
1500
150.0
1270.0
138.2
440.0
2000
200.0
1690.0
184.2
550.0
2500
250.0
2120.0
230.0
660.0
3000
300.0
2540.0
276.0
880.0
4000
400.0
3380.0
368.0
1100.0
5000
500.0
4230.0
461.0
1320.0
6000
600.0
5080.0
553.0
1540.0
7000
700.0
5920.0
645.0
1760.0
8000
800.0
6770.0
737.0
1980.0
9000
900.0
7620.0
829.0
2200.0
10000
1000.0
8460.0
921.0
3300.0
15000
1500.0
13700.0
4400.0
20000
2000.0
18400.0
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
55
Anderson Greenwood Pressure Relief Valves
Technical Manual
Fluid Data
Curve to Evaluate Gas Constant C and Gas Specific Heat Ratio k
400
390
380
k
C = 520
k+1
k-1
( (
2
k+1
Gas Constant, C
370
360
350
340
330
320
310
▲
1.00
▲
1.10
▲
1.20
▲
1.30
▲
1.40
▲
1.50
▲
1.60
▲
1.70
▲
1.80
▲
1.90
▲
2.00
Gas Specific Heat Ratio, k
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
56
Anderson Greenwood Pressure Relief Valves
Technical Manual
Fluid Data
PCF
Curve to Evaluate Critical Pressure Ratio
P1
0.610
0.600
PCF
0.590
P1
=
(k +2 1)
k
k-1
0.580
0.570
PCF
P1
0.550
Critical Pressure Ratio,
0.560
0.540
0.530
0.520
0.510
0.500
0.490
0.480
0.470
0.460
0.450
0.440
▲
▲
▲
▲
▲
▲
▲
▲
▲
▲
▲
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.70
1.80
1.90
2.00
Gas Specific Heat Ratio, k
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
57
Anderson Greenwood Pressure Relief Valves
Technical Manual
Fluid Data
The specific heat ratios listed herein have
been obtained from numerous sources. They
may vary from values available to the reader.
Exercise caution when selecting the specific
heat ratio. Please note that the values for C
and PCF/P1 are derived from the listed k.
Physical Properties for Selected Gases
Gas
Empirical
Formula
Molecular
Weight
M
Specific
Heat
Ratio
k
Gas
Constant
C
Critical
Pressure
Ratio
PCF/P1
C3H6O
58.08
1.12
329
0.581
C2H2
26.04
1.26
343
0.553
—
28.97
1.40
356
0.528
NH3
17.03
1.31
348
0.544
Ar
39.95
1.67
378
0.487
Benzene (Benzol or Benzole)
C6H6
78.11
1.12
329
0.581
Boron Trifluoride
BF3
67.82
1.2
337
0.564
Butadiene-1,3 (Divinyl)
C4H6
54.09
1.12
329
0.581
Butane (Normal Butane)
C4H10
58.12
1.09
326
0.587
Butylene (1-Butene)
C4H8
56.11
1.11
328
0.583
Carbon Dioxide
CO2
44.01
1.29
346
0.548
Carbon Disulfide (C. Bisulfide)
CS2
76.13
1.21
338
0.563
Acetone
Acetylene (Ethyne)
Air
Ammonia, Anhydrous
Argon
Carbon Monoxide
Carbon Tetrachloride
Chlorine
CO
28.01
1.40
356
0.528
CCI4
153.82
1.11
328
0.583
Cl2
70.91
1.36
353
0.535
Chloromethane (Methyl Chloride)
CH3Cl
50.49
1.28
345
0.549
Cyclohexane
C6H12
84.16
1.09
326
0.587
Cyclopropane (Trimethylene)
C3H6
42.08
1.11
328
0.583
C10H22
142.29
1.04
320
0.598
C4H10O3
106.17
1.07
323
0.591
C2H6O
46.07
1.11
328
0.583
Dowtherm A
—
165.00
1.05
321
0.595
Dowtherm E
—
147.00
1.00
315
0.607
C2H6
30.07
1.19
336
0.566
C2H6O
46.07
1.13
330
0.578
C2H4
28.05
1.24
341
0.557
Decane-n
Diethylene Glycol (DEG)
Diethyl Ether (Methyl Ether)
Ethane
Ethyl Alcohol (Ethanol)
Ethylene (Ethene)
Ethylene Glycol
C2H6O2
62.07
1.09
326
0.587
Ethylene Oxide
C2H4O
44.05
1.21
338
0.563
Fluorocarbons:
12, Dichlorodifluoromethane
CCI2F2
120.93
1.14
331
0.576
13, Chlorotrifluoromethane
CCIF3
104.47
1.17
334
0.570
13B1, Bromotrifluoromethane
CBrF3
148.93
1.14
331
0.576
22, Chlorodifluoromethane
CHCIF2
86.48
1.18
335
0.568
115, Chloropentafluoroethane
C2CIF5
154.48
1.08
324
0.589
C3H8O3
92.10
1.06
322
0.593
Glycerine (Glycerin or Glycerol)
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
58
Anderson Greenwood Pressure Relief Valves
Technical Manual
Fluid Data
Physical Properties for Selected Gases, continued
Gas
Empirical
Formula
Molecular
Weight
M
Specific
Heat
Ratio
k
Gas
Constant
C
Critical
Pressure
Ratio
PCF/P1
Helium
He
4.00
1.67
378
0.487
Heptane
C7H16
100.21
1.05
321
0.595
Hexane
C6H14
86.18
1.06
322
0.593
H2
2.02
1.41
357
0.527
Hydrogen Chloride, Anhydrous
HCl
36.46
1.41
357
0.527
Hydrogen Sulfide
H2S
34.08
1.32
349
0.542
Isobutane (2-Methylpropane)
C4H10
58.12
1.10
327
0.585
Isobutane (2-Methyl-1,3butadiene)
C5H8
68.12
1.09
326
0.587
Hydrogen
Isopropyl Alcohol (Isopropanol)
Krypton
C3H8O
60.10
1.09
326
0.587
Kr
83.80
1.71
380
0.481
CH4
16.04
1.31
348
0.544
Methyl Alcohol (Methanol)
CH4O
32.04
1.20
337
0.564
Methylanmines, Anhydrous:
Monomethylamine (Methylamine)
CH5N
31.06
1.02
317
0.602
Dimethylamine
C2H7N
45.08
1.15
332
0.574
Triethylamine
C3H9N
59.11
1.18
335
0.568
Methane
Methyl Mercapton (Methylamine)
CH4S
48.11
1.20
337
0.564
Naphthalene (Naphthaline)
C10H8
128.17
1.07
323
0.591
Natural Gas (Relative Density = 0.60)
—
17.40
1.27
344
0.551
Neon
Ne
20.18
1.64
375
0.491
Nitrogen
N2
28.01
1.40
356
0.528
N2O
44.01
1.30
347
0.546
Octane
Nitrous Oxide
C8H18
114.23
1.05
321
0.595
Oxygen
O2
32.00
1.40
356
0.528
Pentane
C5H12
72.15
1.07
323
0.591
Propadiene (Allene)
C3H4
40.07
1.69
379
0.484
Propane
C3H8
44.10
1.13
330
0.578
Propylene (Propene)
C3H6
42.08
1.15
332
0.574
Propylene Oxide
C3H6O
58.08
1.13
330
0.578
Styrene
C8H8
104.15
1.07
323
0.591
Sulfur Dioxide
SO2
64.06
1.28
345
0.549
Sulfur Hexafluoride
SF6
146.05
1.09
326
0.587
Steam
H2O
18.02
1.31
348
0.544
Toluene (Toluol or Methylbenzene)
Triethylene Glycol (TEG)
Vinyl Chloride Monomer (VCM)
Xenon
Xylene (p-Xylene)
C7H8
92.14
1.09
326
0.587
C6H14O4
150.18
1.04
320
0.598
C2H3Cl
62.50
1.19
336
0.566
Xe
131.30
1.65
376
0.490
C8H10
106.17
1.07
323
0.591
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
59
Anderson Greenwood Pressure Relief Valves
Technical Manual
Fluid Data
Physical Properties for Selected Liquids
Fluid
Acetaldehyde
Empirical
Formula
Relative
Density G:
Water = 1
Fluid
Temperature
˚C
˚F
C2H4
0.779
20
68
Acetic Acid
C2H4O2
1.051
20
68
Acetone
C3H6O
0.792
20
68
NH3
0.666
20
68
—
0.88-0.94
15.6
60
60
Ammonia, Anhydrous
Automotive Crankcase and Gear Oils:
SAE-5W Through SAE 150
Beer
—
1.01
15.6
Benzene (Benzol)
C6H6
0.880
20
68
Boron Trifluoride
BF3
1.57
-100
-148
Butadiene-1,3
C4H6
0.622
20
68
Butane-n (Normal Butane)
C4H10
0.579
20
68
Butylene (1-Butene)
C4H8
0.600
20
68
Carbon Dioxide
CO2
1.03
-20
-4
Carbon Disulphide (C. Bisulphide)
CS2
1.27
20
68
Carbon Tetrachloride
CCl4
1.60
20
68
Chlorine
Cl2
1.42
20
68
CH3Cl
0.921
20
68
32.6 Deg API
—
0.862
15.6
60
35.6 Deg API
—
0.847
15.6
60
40 Deg API
—
0.825
15.6
60
48 Deg API
—
0.79
15.6
60
C6H12
0.780
20
68
C3H6
0.621
20
68
C10H22
0.731
20
68
Chloromethane (Methyl Chloride)
Crude Oils:
Cyclohexane
Cyclopropane (Trimethylene)
Decane-n
Diesel Fuel Oils
Diethylene Glycol (DEG)
Dimethyl Ether (Methyl Ether)
0.82-0.95
15.6
60
C4H10O3
—
1.12
20
68
C2H6O
0.663
20
68
Dowtherm A
—
0.998
20
68
Dowtherm E
—
1.087
20
68
C2H6
0.336
20
68
Ethane
Ethyl Alcohol (Ethanol)
C2H6O
0.79
20
68
C2H4
0.569
-104
-155
Ethylene Glycol
C2H6O2
1.115
20
68
Ethylene Oxide
C2H4O
0.901
20
68
CCl2F2
1.34
20
68
Ethylene (Ethene)
Fluorocarbons:
R12, Dichlorodifluoromethane
R13, Chlorotrifluoromethane
CClF3
0.916
20
68
R13B1, Bromtrifluoromethane
CBrF3
1.58
20
68
R22, Chlorodifluoromethane
CHClF2
1.21
20
68
R115, Chloropentafluoroethane
C2ClF5
1.31
20
68
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
60
Anderson Greenwood Pressure Relief Valves
Technical Manual
Fluid Data
Physical Properties for Selected Liquids, continued
Fluid
Fuel Oils, Nos. 1, 2, 3, 5 and 6
Gasolines
Empirical
Formula
Relative
Density G:
Water = 1
Fluid
Temperature
˚C
˚F
—
0.82-0.95
15.6
60
—
0.68-0.74
15.6
60
C3H8O3
1.26
20
68
Heptane
C7H16
0.685
20
68
Hexane
C6H14
0.660
20
68
Hydrochloric Acid
HCl
1.64
15.6
60
Hydrogen Sulphide
H2S
0.78
20
68
C4H10
0.558
20
68
Glycerine (Glycerin or Glycerol)
Isobutane (2-Methylpropane)
Isoprene (2-Methyl-1,3-Butadiene)
Isopropyl Alcohol (Isopropanol)
Jet Fuel (average)
Kerosene
Methyl Alcohol (Methanol)
C5H8
0.682
20
68
C3H8O
0.786
20
68
—
0.82
15.6
60
0.78-0.82
15.6
60
CH4O
—
0.792
20
68
Methylamines, Anhydrous:
Monomethylamine (Methylamine)
CH5N
0.663
20
68
Dimethylamine
C2H7N
0.656
20
68
Trimethylamine
C3H9N
0.634
20
68
Methyl Mercapton (Methanethiol)
CH4S
0.870
20
68
Nitric Acid
HNO3
1.5
15.6
60
N2O
1.23
-88.5
-127
Octane
C8H18
0.703
20
68
Pentane
C5H12
0.627
20
68
Propadiene (Allene)
C3H4
0.659
-34.4
-30
Propane
C3H8
0.501
20
68
68
Nitrous Oxide
Propylene (Propene)
C3H6
0.514
20
C3H6O
0.830
20
68
Styrene
C8H8
0.908
20
68
Sulfur Dioxide
SO2
1.43
20
68
Sulphur Hexafluoride
SF6
1.37
20
68
Propylene Oxide
Sulphur Acid:
H2SO4
95-100%
—
1.839
20
68
60%
—
1.50
20
68
20%
Toluene (Toluol or Methylbenzene)
Triethylene Glycol (TEG)
Vinyl Chloride Monomer (VCM)
Water, fresh
Water, sea
Xylene (p-Xylene)
—
1.14
20
68
C7H8
0.868
20
68
C6H12O4
1.126
20
68
C2H3Cl
0.985
-20
-4
H2O
1.00
20
68
—
1.03
20
68
C8H10
0.862
20
68
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
61
Anderson Greenwood Pressure Relief Valves
Technical Manual
ANSI Flange Standards
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
62
Anderson Greenwood Pressure Relief Valves
Technical Manual
Pressure and Temperature Ratings
WCB
Temperature ˚F [˚C]
800
[427]
600
[316]
600
400
[204]
30 0
15 0
200
[93]
0
200
[13.8]
400
[27.6]
600
[41.3]
800
[55.1]
1000
[69.0]
1200
[82.7]
1400
[96.5]
1600
[110.2]
5600
[385.8]
6400
[441.0]
Pressure - psig [barg]
1000
[538]
Temperature ˚F [˚C]
800
[427]
600
[316]
2500
1500
400
[204]
900
200
[93]
0
800
[55.1]
1600
[110.2]
2400
[165.4]
3200
[220.5]
4000
4800
[275.6] [330.7]
Pressure - psig [barg]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
63
Anderson Greenwood Pressure Relief Valves
Technical Manual
Pressure and Temperature Ratings
WC6
1000
[538]
Temperature ˚F [˚C]
800
[427]
600
[316]
600
30 0
400
[204]
15 0
200
[93]
0
200
[13.8]
400
[27.6]
600
[41.3]
800
[55.1]
1000
[69.0]
1200
[82.7]
1400
[96.5]
1600
[110.2]
5600
[385.8]
6400
[441.0]
Pressure - psig [barg]
1000
[538]
Temperature ˚F [˚C]
800
[427]
600
[316]
2500
1500
400
[204]
900
200
[93]
0
800
[55.1]
1600
[110.2]
2400
[165.4]
3200
[220.5]
4000
4800
[275.6] [330.7]
Pressure - psig [barg]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
64
Anderson Greenwood Pressure Relief Valves
Technical Manual
Pressure and Temperature Ratings
Monel
1000
[538]
Temperature ˚F [˚C]
800
[427]
600
600
[316]
30 0
400
[204]
15 0
200
[93]
0
200
[13.8]
400
[27.6]
600
[41.3]
800
[55.1]
1000
[69.0]
1200
[82.7]
1400
[96.5]
1600
[110.2]
4000
4800
[275.6] [330.7]
5600
[385.8]
6400
[441.0]
Pressure - psig [barg]
1000
[538]
Temperature ˚F [˚C]
800
[427]
600
[316]
2500
400
[204]
1500
900
200
[93]
0
800
[55.1]
1600
[110.2]
2400
[165.4]
3200
[220.5]
Pressure - psig [barg]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
65
Anderson Greenwood Pressure Relief Valves
Technical Manual
Pressure and Temperature Ratings
Hastelloy
1000
[538]
Temperature ˚F [˚C]
800
[427]
600
600
[316]
30 0
400
[204]
15 0
200
[93]
0
200
[13.8]
400
[27.6]
600
[41.3]
800
[55.1]
1000
[69.0]
1200
[82.7]
1400
[96.5]
1600
[110.2]
5600
[385.8]
6400
[441.0]
Pressure - psig [barg]
1000
[538]
Temperature ˚F [˚C]
800
[427]
600
[316]
2500
1500
400
[204]
900
200
[93]
0
800
[55.1]
1600
[110.2]
2400
[165.4]
3200
[220.5]
4000
4800
[275.6] [330.7]
Pressure - psig [barg]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
66
Anderson Greenwood Pressure Relief Valves
Technical Manual
Pressure and Temperature Ratings
CF8M
1200
[649]
Temperature ˚F [˚C]
1000
[538]
800
[427]
600
600
[316]
30 0
400
[204]
15 0
200
[93]
0
200
[13.8]
400
[27.6]
600
[41.3]
800
[55.1]
1000
[69.0]
1200
[82.7]
1400
[96.5]
1600
[110.2]
4000
4800
[275.6] [330.7]
5600
[385.8]
6400
[441.0]
Pressure - psig [barg]
1200
[649]
Temperature ˚F [˚C]
1000
[538]
800
[427]
2500
600
[316]
1500
400
[204]
900
200
[93]
0
800
[55.1]
1600
[110.2]
2400
[165.4]
3200
[220.5]
Pressure - psig [barg]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
67
Anderson Greenwood Pressure Relief Valves
Technical Manual
Pressure and Temperature Ratings
WC9
1200
[649]
Temperature ˚F [˚C]
1000
[538]
800
[427]
600
600
[316]
30 0
400
[204]
15 0
200
[93]
0
200
[13.8]
400
[27.6]
600
[41.3]
800
[55.1]
1000
[69.0]
1200
[82.7]
1400
[96.5]
1600
[110.2]
4000
4800
[275.6] [330.7]
5600
[385.8]
6400
[441.0]
Pressure - psig [barg]
1200
[649]
Temperature ˚F [˚C]
1000
[538]
800
[427]
2500
600
[316]
1500
400
[204]
900
200
[93]
0
800
[55.1]
1600
[110.2]
2400
[165.4]
3200
[220.5]
Pressure - psig [barg]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
68
Anderson Greenwood Pressure Relief Valves
Technical Manual
ANSI Flange Standards
Types of Flanges
All flange faces and ratings conform to
ANSI B16.5-1977. Steel, full nozzle valve
inlet flange thickness is equal to or
greater than ANSI minimum thickness.
The raised face thickness is also equal to
or greater than ANSI standard, and inlet
thickness ‘D’ dimension should be used
for calculating length of stud for inlet bolting on the various available flange faces.
Refer to the next two following pages for
ANSI dimensions for raised face and ring
joint.
The drilling of inlet and outlet flanges
straddle the centerlines of the valves.
For ring joint outlet face and other available similar faces with projections or
depressions, the centerline of inlet to face
of outlet dimension is increased by the
amount of the projection or depression
over the ANSI total flange thickness.
For outlets furnished with heavier than
standard flanges, the centerline of inlet
to face of outlet dimension increases by
the difference in the ANSI total flange
thickness.
Raised Face
Ring Joint
Large Tongue
Large Groove
Small Male
Small Female
Small Tongue
Small Groove
Large Female
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
69
Anderson Greenwood Pressure Relief Valves
Technical Manual
ANSI Flange Standards
Semi-Nozzle
Full
Nozzle
Body
Body
ASA
Raised
Face
D
E
Inlet Iron Semi-Nozzle ANSI B16.1
Inlet Iron Full Nozzle ANSI B16.5
Specifications
Pipe
Size
in [mm]
Diam. of
Flange
in
[mm]
Min. Thk.
of Flange
in [mm]
Diam. of
Raised Face
in
[mm]
Diam. of
Bolt Circle
in
[mm]
Number
of Bolts
in [mm]
Diam. of
Bolts
in [mm]
4
[102]
1/2
[13]
[102]
5/8
[16]
[16]
125 lb. Iron Flange
11/2
[40]
2
5
[50]
6
[127]
9/16
[152]
5/8
[17]
[19]
21/2
[65]
7
[178]
11/16
3
[80]
7 1/2
[191]
3/4
[229]
15/16
4
[100]
9
[14]
—
3 7/8
—
4 3/4
—
—
5 1/2
[140]
4
[102]
5/8
—
—
6
[152]
4
[102]
5/8
[16]
—
7 1/2
[203]
5/8
[16]
[19]
—
[16]
—
[24]
—
[98]
[121]
4
[178]
8
6
[150]
11
[279]
1
[25]
—
—
9 1/2
[241]
8
[203]
3/4
8
[200]
13 1/2
[343]
11/8
[29]
—
—
11 3/4
[298]
8
[203]
3/4
[19]
4 1/2
[114]
4
[102]
3/4
[19]
250 lb. Iron Flange
11/2
[40]
6 1/8
[156]
13/16
[21]
3 9/16
[90]
2
[50]
6 1/2
[165]
7/8
[22]
4 3/16
[106]
5
[127]
8
[203]
5/8
[16]
21/2
[65]
7 1/2
[191]
1
[25]
4 15/16
[125]
5 7/8
[149]
8
[203]
3/4
[19]
[80]
8 1/4
[210]
11/8
[29]
5 11/16
[144]
6 5/8
[203]
3/4
[19]
[19]
3
[168]
8
4
[100]
10
[254]
11/4
[32]
6 15/16
[176]
7 7/8
[200]
8
[203]
3/4
6
[150]
12 1/2
[318]
17/16
[37]
9 11/16
[246]
10 5/8
[270]
12 [305]
3/4
[19]
8
[200]
15
[381]
15/8
[41]
11 15/16
[303]
13
[330]
12 [305]
7/8
[22]
Pipe
Size
in [mm]
Diam. of
Flange
Min. Thk.
of Flange
in
in [mm]
[mm]
Diam. of
Raised
Face
in [mm]
Diam. of
Bolt
Circle
in [mm]
Number
of
Bolts
in [mm]
Diam. of
Bolts
in [mm]
D-Dim
Thk.
D Series
in [mm]
E-Dim
Thk.
D Series
in [mm]
[102]
1/2
[13]
1 3/16
[30]
1/2
[13]
[102]
1/2
[13]
1 5/16
[33]
11/16
[17]
[35]
11/16
[17]
150 lb. Steel Flange
1
11/2
[25]
[40]
4 1/4 [108]
5
7/16
[11]
2
[127]
9/16
[14]
2 7/8
[51]
3 1/8
[73]
3 7/8
[92]
4 3/4
[79]
[98]
4
4
2
[50]
6
[152]
5/ 8
[16]
3 5/8
[121]
4
[102]
5/8
[16]
1 3/8
21/2
[65]
7
[178]
11/16
[17]
4 1/8 [105]
5 1/2 [140]
4
[102]
5/8
[16]
—
—
3
[80]
7 1/2 [191]
3/ 4
[19]
5
[127]
6
4
[102]
5/8
[16]
1 1/2
[38]
11/16
[17]
9
15/16
[24]
6 3/16
[157]
7 1/2
[203]
5/8
[16]
1 11/16
[43]
11/16
[17]
8 1/2
[216]
9 1/2
[48]
13/16
[21]
[51]
13/16
[21]
4
[100]
[229]
[152]
[178]
8
6
[150]
11
1
[25]
[241]
8
[203]
3/4
[19]
1 7/8
8
[200]
13 1/2 [343]
11/8
[29]
10 5/8 [270]
11 3/4 [298]
8
[203]
3/4
[19]
2
16
13/16
[30]
12 3/4
14 1/4
[305]
7/8
[22]
—
10
[250]
[279]
[406]
[324]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
[362]
12
70
—
—
—
—
—
Anderson Greenwood Pressure Relief Valves
Technical Manual
ANSI Flange Standards
Specifications
Pipe
Size
in [mm]
Diam. of
Flange
Min. Thk.
of Flange
in
in [mm]
[mm]
Diam. of
Raised
Face
in [mm]
Diam. of
Bolt
Circle
in [mm]
Number
of
Bolts
in [mm]
Diam. of
Bolts
D-Dim
D Series
E-Dim
D Series
in [mm]
in
in [mm]
[mm]
300 lb. Steel Flange
1
11/2
[25]
4 7/8 [124]
11/16
[40]
6 1/8
[156]
13/16
[165]
7/8
[17]
2
[21]
2 7/8
[51]
3 1/2
[73]
4 1/2
[89]
4
[114]
4
[102]
5/8
[102]
3/4
[16]
1 7/16
[37]
1/2
[13]
[19]
1 5/8
[41]
11/16
[17]
[17]
2
[50]
6 1/2
[22]
3 5/8
[127]
8
[203]
5/8
[16]
1 3/4
[44]
11/16
21/2
[65]
7 1/2 [191]
1
[25]
4 1/8 [105]
5 7/8 [149]
8
[203]
3/4
[19]
1 7/8
[48]
11/16
[17]
3
[80]
8 1/4 [210]
1 1/8
[29]
5
[127]
6 5/8 [168]
8
[203]
3/4
[19]
2
[51]
11/16
[17]
1 1/4
[32]
6 3/16
[157]
7 7/8
[19]
2 1/16
[52]
11/16
[17]
[37]
8 1/2 [216]
[19]
2 5/16
[59]
13/16
[19]
[64]
13/16
[19]
4
[100]
10
6
[150]
12 1/2 [318]
1 7/16
15
1 5/8
8
[200]
[254]
[381]
[92]
5
[200]
8
[203]
3/4
10 5/8 [270]
12
[305]
3/4
[22]
2 1/2
[41]
10 5/8
[270]
[17]
2
[51]
3 1/2
[22]
2 7/8
[73]
4 1/2
[114]
[25]
3 5/8
[92]
5
[127]
[105]
5 7/8
[149]
[127]
6 5/8 [168]
[157]
8 1/2
13
[330]
12
[305]
7/8
[89]
4
[102]
5/8
[16]
1 7/16
[37]
1/2
[13]
4
[102]
3/4
[19]
1 5/8
[41]
11/16
[17]
8
[203]
5/8
[16]
1 3/4
[44]
11/16
[17]
8
[203]
3/4
[19]
1 7/8
[48]
11/16
[17]
8
[203]
3/4
[19]
2
[51]
11/16
[17]
7/8
[22]
2 1/4
[57]
11/16
[17]
[25]
2 3/4
[70]
13/16
[19]
[25]
2
[51]
11/16
[17]
[22]
2 1/4
[57]
11/16
[17]
[25]
2 3/8
[60]
11/16
[17]
[22]
2 1/4
[57]
11/16
[17]
[64]
11/16
[17]
600 lb. Steel Flange
[25]
4 7/8 [124]
11/16
11/2
[40]
6 1/8
7/8
2
[50]
6 1/2 [165]
1
21/2
[65]
7 1/2
[191]
1 1/8
[29]
4 1/8
3
[80]
8 1/4 [210]
1 1/4
[32]
5
1
4
[100]
10 3/4
6
[150]
14
[156]
[273]
1 1/2
[38]
6 3/16
[356]
1 7/8
[48]
8 1/2 [216]
8
[203]
11 1/2 [292]
[216]
12
[305]
1
1
900 lb. Steel Flange
11/2
[40]
7
[178]
1 1/4
[32]
2 7/8
[73]
4 7/8 [124]
4
[102]
2
[50]
8 1/2 [216]
1 1/2
[38]
3 5/8
[92]
6 1/2 [165]
8
[203]
21/2
[65]
9 5/8
[244]
1 5/8
[41]
4 1/8
[105]
7 1/2
[191]
8
[203]
3
[80]
9 1/2 [241]
1 1/2
[38]
5
[127]
7 1/2 [191]
8
[203]
7/8
[292]
1 3/4
[44]
6 3/16
[157]
9 1/4
[29]
2 1/2
[25]
2
[51]
11/16
[17]
[22]
2 5/16
[59]
11/16
[17]
[17]
4
[100]
11 1/2
7/8
1
[235]
8
[203]
11/8
1
1500 lb. Steel Flange
11/2
[40]
7
[178]
1 1/4
[32]
2 7/8
[73]
4 7/8 [124]
4
[102]
2
[50]
8 1/2 [216]
1 1/2
[38]
3 5/8
[92]
6 1/2 [165]
8
[203]
7/8
3
[80]
4
[100]
10 1/2
[267]
1 7/8
[48]
5
[203]
8
[203]
11/8
[29]
2 5/8
[67]
11/16
12 1/4 [311]
2 1/8
[54]
6 3/16 [157]
9 1/2 [241]
8
[203]
11/4 [32]
2 7/8
[73]
11/16
[17]
1 3/4
[44]
2 7/8
[73]
5 3/4 [146]
4
[102]
11/8 [29]
2 1/2
[64]
11/16
[17]
2
[51]
3 5/8
[92]
6 3/4 [171]
8
[203]
1
2 13/16 [71]
11/16
[17]
[127]
8
2500 lb. Steel Flange
11/2
[40]
8
2
[50]
9 1/4 [235]
[203]
[25]
Note
1. Inlet Thickness = Flange Thickness plus
Raised Face Thickness.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
71
Anderson Greenwood Pressure Relief Valves
Technical Manual
ANSI Flange Standards
Specifications
Pipe
Size
in [mm]
Diam. of
Flange
in
[mm]
Min. Thk.
of Flange
in [mm]
Diam. of
Raised Face
in
[mm]
Diam. of
Bolt Circle
in
[mm]
Number
of Bolts
in [mm]
Diam. of
Bolts
in [mm]
150 lb. Bronze Flange, ANSI B16.24
1/ 2
[15]
3 1/2
[89]
5/16
[8]
—
—
2 3/8
[60]
4 [102]
1/2
[13]
3/ 4
[20]
3 7/8
[98]
11/32
[9]
—
—
2 3/4
[70]
4 [102]
1/2
[13]
—
3 1/8
4 [102]
1/2
[13]
[89]
4 [102]
1/2
[13]
[98]
4 [102]
1/2
[13]
4 [102]
5/8
[16]
[16]
[25]
4 1/4
[108]
3/8
11/ 4
[32]
4 5/8
[117]
13/32
[10]
—
—
3 1/2
11/2
[40]
5
[127]
7/16
[11]
—
—
3 7/8
[152]
1/2
—
4 3/4
1
2
[50]
6
[10]
[13]
—
—
[79]
[121]
21/2
[65]
7
[178]
9/16
[14]
—
—
5 1/2
[140]
4 [102]
5/8
3
[80]
7 1/2
[191]
5/8
[16]
—
—
6
[152]
8 [203]
5/8
[16]
4
[100]
9
[229]
11/16
[17]
—
—
7 1/2
[191]
8 [203]
5/8
[16]
[254]
3/4
—
8 1/2
8 [203]
3/4
[19]
[21]
—
—
9 1/2
[241]
8 [203]
3/4
[19]
[24]
—
—
11 3/4
[298]
12 [305]
3/4
[19]
[25]
—
—
14 1/4
[362]
12 [305]
7/8
[22]
1/2
[13]
—
—
2 5/8
[67]
4 [102]
1/2
[13]
5
[125]
10
6
[150]
11
[279]
13/16
8
[200]
13 1/2
[343]
15/16
10
[250]
16
[406]
1
[19]
—
[216]
300 lb. Bronze Flange, ANSI B16.24
1/ 2
[15]
3 3/4
[95]
3/ 4
[20]
4 5/8
[117]
17/32
[13]
—
—
3 1/4
[83]
4 [102]
5/8
[16]
[25]
4 7/8
[124]
19/32
[15]
—
—
3 1/2
[89]
4 [102]
5/8
[16]
—
3 7/8
4 [102]
5/8
[16]
[19]
1
1 1/ 4
[32]
5 1/4
[133]
5/8
11/2
[40]
6 1/8
[156]
11/16
[17]
—
—
4 1/2
[114]
4 [102]
3/4
2
[50]
6 1/2
[165]
3/4
[19]
—
—
5
[127]
8 [203]
5/8
[16]
21/2
[65]
7 1/2
[191]
13/16
[21]
—
—
5 7/8
[149]
8 [203]
3/4
[19]
[80]
8 1/4
[210]
29/32
—
6 5/8
8 [203]
3/4
[19]
[200]
8 [203]
3/4
[19]
[235]
8 [203]
3/4
[19]
[19]
3
[16]
[23]
—
—
4
[100]
10
[254]
11/16
5
[125]
11
[279]
11/8
6
[150]
12 1/2
[318]
13/16
[30]
—
—
10 5/8
8
[200]
15
[381]
13/8
[35]
—
—
13
[98]
[168]
[27]
—
—
7 7/8
[29]
—
—
9 1/4
[270]
12 [305]
3/4
[330]
12 [305]
7/8 [22]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
72
Anderson Greenwood Pressure Relief Valves
Technical Manual
ANSI Flange Standards
Note
Use 1500 psig in sizes 1 to 21/2 for 900 lbs.
pressure. The depth of groove is added to minimum thickness of the flange increasing the
center line of inlet to face of outlet. Ring Joint
inlet Face and other flange facings have the
same dimension from center line of outlet to
face of inlet as raised inlet flange. Diameter of
raised face is stamped with groove number. All
dimensions conform to ANSI B16.5-1977.
± 1/64 -0 E
23° ± 1/2°
F
R
± .008
K
P ± .005
Minimum
Ring Joint Facings
Nominal Pipe Size
ANSI Flange Class
Groove
Groove Dimensions
Diameter of Raised Face ‘K’
Pitch
ANSI Flange Class
Number Dia.
Depth Width Radius
300
150
300
600
900
1500 2500
P
E
F
R
150
600
900
1500 2500
in[mm] in[mm] in[mm] in[mm] in[mm] in[mm]
in[mm] in[mm] in [mm] in[mm] in [mm] in [mm] in [mm] in [mm] in[mm]
1 [25]
1 [25]
1 [25]
1 [25]
11/2 [40]
1 1/2 [40]
11/2 [40]
3/4 [20]
11/2 [40]
2 [50]
2 [50]
11/2 [40]
2 [50]
2 [50]
21/2 [65]
2 1/2 [65] 2 1/2 [65]
2 [50]
2 1/2 [65]
3 [80]
3 [80]
3 [80]
3 [80]
3 [80]
4 [100]
4 [100] 4 [100] 4 [100]
4 [100]
6 [150]
6 [150] 6 [150]
8 [200]
8 [200]
10 [250]
R-15
1 7/8
[48]
1/4
[6]
11/32
[9]
1/32
[1] 21/2 [64]
R-16
2
[51]
1/4
[6]
11/32
[9]
1/32
[1]
R-19
2 9/16 [65]
1/4
[6]
11/32
[9]
1/32
[1] 3 1/4 [83]
R-20
2 11/16
[68]
1/4
[6]
11/32
[9]
1/32
[1]
R-22
3 1/4
[83]
1/4
[6]
11/32
[9]
1/32
[1] 4 [102]
R-23
3 1/4
[83]
5/16
[8]
15/32 [12]
1/32
[1]
R-24
3 /4
[95]
5/16
1/32
[1]
3
[8]
15/32 [12]
23/4 [70]
213/16 [71] 27/8 [73]
39/16 [90]
35/8 [92]
41/4 [108]
[1]
R-25
4
[102]
1/4
[6]
11/32
[9]
1/32
R-26
4
[102]
5/16
[8]
15/32 [12]
1/32
[1]
R-27
4 1/4 [108]
5/16
[8]
15/32 [12]
1/32
[1]
R-29
4 1/2
[114]
1/4
[6]
11/32
[9]
1/32
[1]
R-31
4 7/8
[124]
5/16
[8]
15/32 [12]
1/32
[1]
R-35
5 3/8 [137]
5/16
[8]
15/32 [12]
1/32
[1]
R-36
5 7/8 [149]
1/4
[6]
11/32
[9]
1/32
[1] 63/4 [171]
R-37
5 7/8
[149]
5/16
[8]
15/32 [12]
1/32
[1]
R-39
6 3/8 [162]
5/16
[8]
15/32 [12]
1/32
[1]
R-43
7 5/8 [194]
1/4
[6]
11/32
[9]
1/32
[1] 85/8 [219]
R-45
8 5/16
5/16
[8]
15/32 [12]
1/32
[1]
R-48
9 3/4 [248]
1/4
[6]
11/32
[9]
1/32
[1] 103/4 [273]
R-49 10 5/8 [270]
5/16
[8]
15/32 [12]
1/32
[1]
R-52 12
1
[211]
[305]
/4 [6]
/32 [9]
11
1
41/2 [114]
47/8
43/4
[124]
[121]
51/4 [133]
5 [127]
53/8 [137]
51/4
[133]
53/4 [146] 61/8 [156]
65/8 [168]
67/8 [175] 71/8 [181]
75/8 [194]
91/2 [241] 91/2 [241]
117/8 [302]
/32 [1] 13 [330]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
73
Anderson Greenwood Pressure Relief Valves
Technical Manual
ANSI Flange Standards
Raised Facing and Ring Joint Facing
Temperature
°F [°C]
150
in [mm]
300
in [mm]
275 [19.0]
720 [49.7]
SS (A351 Gr CF8M)
100
[38]
ANSI Flange Class
600
900
in [mm]
in [mm]
1500
in [mm]
2500
in [mm]
Maximum Pressure psig [barg]
1440
[99.3]
2160 [149.0]
3600
[248.3]
6000
[413.8]
200
[93]
240 [16.6]
620 [42.8]
1240
[85.5]
1860 [128.3]
3095
[213.4]
5160
[355.9]
300
[149]
215 [14.8]
560 [38.6]
1120
[77.2]
1680 [115.9]
2795
[192.8]
4660
[321.4]
1540 [106.2]
2570
[177.2]
4280
[295.2]
390
[164.8]
3980
[274.5]
400
[204]
195 [13.4]
515 [35.5]
1030
[71.0]
500
[260]
170 [11.7]
480 [33.1]
955
[65.9]
435
[99.0]
600
[316]
140
[9.7]
450 [31.0]
905
[62.4]
1355
[93.4]
2255
[155.5]
3760
[259.3]
700
[371]
110
[7.6]
430 [29.7]
865
[59.7]
1295
[89.3]
2160
[149.0]
3600
[248.3]
800
[427]
80
[5.5]
415 [28.6]
830
[57.2]
1245
[85.9]
2075
[143.1]
3460
[238.6]
900
[482]
50
[3.4]
395 [27.2]
790
[54.5]
1180
[81.4]
1970
[135.9]
3280
[226.2]
1000
[538]
20
[1.4]
365 [25.2]
725
[50.0]
1090
[75.2]
1820
[125.5]
3030
[209.0]
1100
[593]
—
—
325 [22.4]
645
[44.5]
965
[66.6]
1610
[111.0]
2685
[185.2]
1200
[649]
—
—
205 [14.1]
410
[28.3]
620
[42.8]
1030
[71.0]
1715
[118.3]
Monel® (A494 Gr M-35-2)
100
[38]
230 [15.9]
600 [41.4]
1200
[82.8]
1800 [124.1]
3000
[206.9]
5000
[344.8]
200
[93]
200 [13.8]
530 [36.6]
1055
[72.8]
1585 [109.3]
2640
[182.1]
4400
[303.4]
300
[149]
190 [13.1]
495 [34.1]
990
[68.3]
1485 [102.4]
2470
[170.3]
4120
[284.1]
400
[204]
185 [12.8]
480 [33.1]
955
[65.9]
1435
[99.0]
2390
[164.8]
3980
[274.5]
500
[260]
170 [11.7]
475 [32.8]
950
[65.5]
1435
[99.0]
2375
[163.8]
3960
[273.1]
600
[316]
140
[9.7]
475 [32.8]
950
[65.5]
1435
[99.0]
2375
[163.8]
3960
[273.1]
700
[371]
110
[7.6]
475 [32.8]
950
[65.5]
1435
[99.0]
2375
[163.8]
3960
[273.1]
750
[399]
95
[6.6]
470 [32.4]
935
[64.5]
1405
[96.9]
2340
[161.4]
3900
[269.0]
Hastelloy® C (A494 CW-N12MW)
100
[38]
290 [20.0]
750 [51.7]
1500 [103.4]
2250 [155.2]
3750
[258.6]
6250
[431.0]
200
[93]
260 [17.9]
750 [51.7]
1500 [103.4]
2250 [155.2]
3750
[258.6]
6250
[431.0]
300
[149]
230 [15.9]
730 [50.3]
1455 [100.3]
2185 [150.7]
3640
[251.0]
6070
[418.6]
400
[204]
200 [13.8]
705 [48.6]
1410
[97.2]
2115 [145.9]
3530
[243.4]
5880
[405.5]
500
[260]
170 [11.7]
665 [45.9]
1230
[84.8]
1915 [132.1]
3325
[229.3]
5540
[382.1]
600
[316]
140
[9.7]
605 [41.7]
1210
[83.4]
1815 [125.2]
3025
[208.6]
5040
[347.6]
700
[371]
110
[7.6]
570 [39.3]
1135
[78.3]
1705 [117.6]
2840
[195.9]
4730
[326.2]
750
[399]
95
[6.6]
530 [36.6]
1065
[73.4]
1595 [110.0]
2660
[183.4]
4430
[305.5]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
74
Anderson Greenwood Pressure Relief Valves
Technical Manual
ANSI Flange Standards
Raised Facing and Ring Joint Facing
Temperature
°F [°C]
150
in [mm]
300
in [mm]
285 [19.7]
740 [51.0]
ANSI Flange Class
600
900
in [mm]
in [mm]
CS (A216 Grade WCB)
100
[38]
in
1500
[mm]
in
2500
[mm]
3705
[255.5]
6170
[425.5]
Maximum Pressure psig [barg]
1480 [102.1]
2220 [153.1]
200
[93]
260 [17.9]
675 [46.6]
1350
[93.1]
2025 [139.7]
3375
[232.8]
5625
[387.9]
300
[149]
230 [15.9]
655 [45.2]
1315
[90.7]
1970 [135.9]
3280
[226.2]
5470
[377.2]
400
[204]
200 [13.8]
635 [43.8]
1270
[87.6]
1900 [131.0]
3170
[218.6]
5280
[364.1]
500
[260]
170 [11.7]
600 [41.4]
1200
[82.8]
1795 [123.8]
2995
[206.6]
4990
[344.1]
600
[316]
140
[9.7]
550 [37.9]
1095
[75.5]
1640 [113.1]
2735
[188.6]
4560
[314.5]
650
[343]
125
[8.6]
535 [36.9]
1075
[74.1]
1610 [111.0]
2685
[185.2]
4475
[308.6]
700
[371]
110
[7.6]
535 [36.9]
1065
[73.4]
1600 [110.3]
2665
[183.8]
4440
[306.2]
750
[399]
95
[6.6]
505 [34.8]
1010
[69.7]
1510 [104.1]
2520
[173.8]
4200
[289.7]
800
[427]
80
[5.5]
410 [28.3]
825
[56.9]
1235
2060
[142.1]
3430
[236.6]
[85.2]
Raised Facing and Ring Joint Facing
Temperature
°F [°C]
150
in [mm]
300
in [mm]
400
in [mm]
Chrome-Moly Steel (A217 Grade WC6)
100
ANSI Flange Class
600
900
in [mm]
in [mm]
in
1500
[mm]
2500
in [mm]
Maximum Pressure psig [barg]
[38]
290
[20.0]
750
[51.7]
1000
[69.0]
1500
[103.4]
2250 [155.2]
3750
[258.6]
6250 [431.0]
200
[93]
260
[17.9]
710
[49.0]
950
[65.5]
1425
[98.3]
2135 [147.2]
3560
[245.5]
5930 [409.0]
300
[149]
230
[15.9]
675
[46.6]
895
[61.7]
1345
[92.8]
2020 [139.3]
3365
[232.1]
5605 [386.6]
400
[204]
200
[13.8]
660
[45.5]
880
[60.7]
1315
[90.7]
1975 [136.2]
3290
[226.9]
5485 [378.3]
500
[260]
170
[11.7]
640
[44.1]
855
[59.0]
1285
[88.6]
1925 [132.8]
3210
[221.4]
5350 [369.0]
600
[316]
140
[9.7]
605
[41.7]
805
[55.5]
1210
[83.4]
1815 [125.2]
3025
[208.6]
5040 [347.6]
650
[343]
125
[8.6]
590
[40.7]
785
[54.1]
1175
[81.0]
1765 [121.7]
2940
[202.8]
4905 [338.3]
700
[371]
110
[7.6]
570
[39.3]
755
[52.1]
1135
[78.3]
1705 [117.6]
2840
[195.9]
4730 [326.2]
750
[399]
95
[6.6]
530
[36.6]
710
[49.0]
1065
[73.4]
1595 [110.0]
2660
[183.4]
4430 [305.5]
800
[427]
80
[5.5]
510
[35.2]
675
[46.6]
1015
[70.0]
1525 [105.2]
2540
[175.2]
4230 [291.7]
850
[454]
65
[4.5]
485
[33.4]
650
[44.8]
975
[67.2]
1460 [100.7]
2435
[167.9]
4060 [280.0]
900
[482]
50
[3.4]
450
[31.0]
600
[41.4]
900
[62.1]
1350
[93.1]
2245
[154.8]
3745 [258.3]
950
[510]
35
[2.4]
380
[26.2]
505
[34.8]
755
[52.1]
1130
[77.9]
1885
[130.0]
3145 [216.9]
1000
[538]
20
[1.4]
225
[15.5]
300
[20.7]
445
[30.7]
670
[46.2]
1115
[76.9]
1860 [128.3]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
75
Anderson Greenwood Pressure Relief Valves
Technical Manual
ANSI Flange Standards
Bronze Flange Ratings ANSI B16.24 1971
Temperature
°F
[°C]
ANSI Flange Class
150
300
in [mm]
in [mm]
Bronze (B62)
Maximum Pressure psig [barg]
0 to 150 [-18 to +66]
175
225 [15.5]
500 [34.5]
[79]
220 [15.2]
480 [33.1]
200
[93]
210 [14.5]
465 [32.1]
225
[107]
205 [14.1]
445 [30.7]
250
[121]
195 [13.4]
425 [29.3]
275
[135]
190 [13.1]
410 [28.3]
300
[149]
180 [12.4]
390 [26.9]
350
[177]
165 [11.4]
350 [24.1]
400
[204]
406
[208]
422
[217]
—
—
150 [10.3]
—
—
315 [21.7]
—
—
300 [20.7]
Iron Flange Ratings ANSI B16.1
Temperature
°F
[°C]
ANSI Flange Class
150
300
in [mm]
in [mm]
Iron (A126)
Maximum Pressure psig [barg]
0 to 150 [-18 to +66]
175 [12.1]
400 [27.6]
200
[93]
165 [11.4]
370 [25.5]
225
[107]
155 [10.7]
355 [24.5]
250
[121]
150 [10.3]
340 [23.4]
275
[135]
145 [10.0]
325 [22.4]
300
[149]
140
[9.7]
310 [21.4]
350
[177]
130
[9.0]
295 [20.3]
375
[191]
125
[8.6]
280 [19.3]
400
[208]
—
—
265 [18.3]
—
—
250 [17.2]
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
76
Anderson Greenwood Pressure Relief Valves
Technical Manual
Valve Installations
Valve Installation Precautions
1. No intervening stop valve is permitted
between the system and/or piping and
its protective relieving valve or valves,
except per ASME SEC. VIII UG-135 (E).
2. No intervening stop valve is permitted
between the protective relieving valve
and discharge port, except per ASME
SEC. VIII UG-135 (E).
3. No valve discharge media is permitted
to strike other piping, or other equipment, when discharge is to atmosphere.
Also, discharge media must be aimed
away from personnel platforms and all
traffic areas.
4. All set pressure adjustments must be
verified as falling within the design
range for that valve spring. Consult
factory. State laws dictate that valve
seals be broken only by persons
authorized to do so by ASME and
Anderson Greenwood and Co. Otherwise, valve warranties are void and
laws breached. Consult factory.
5. When discharging more than one
valve into a common header, excessive back pressure must be avoided.
See ASME SEC. VIII Appx. M-8
6. The capacity of the relieving valve will
always be increased or decreased
proportionally with increase or decrease of set pressure.
7. Test Gags Must Be Removed. Failure
to do so renders the valve inoperable
and, due to overpressure, may damage either the relieving valve or the
system, or both.
8. Bonnet vents on all bellows or balanced pressure relief valves must be
left open – the shipping plugs must be
removed.
9. Pressure relief valves should be
mounted in a vertical position. Installing
a pressure relief valve in other than
a vertical position will adversely affect
operation in varying degrees as a
result of consequent misalignment
of moving parts. Also, warranties may
be voided. Upside-down mounted
valves should be provided with ample
drainage of accumulated liquids from
all sections of the valve.
10. Prior to all installations, inlet connections – flanged or threaded – must be
cleared of foreign matter. Any dirt
entering the valve may damage valve
seats. Use only wrench flats when
securing threaded valves.
11. Should leakage be detected from a
newly installed valve, first assume the
cause to be from shipping and handling or installation procedures. Apply
pressure to the inlet side equal to 75%
of operating pressure so that the lift
lever can be manually activated, thus
operating the valve. For valves without
lift levers, system pressure may be
allowed to rise to the point of valve
operation. In most instances, the valve
will properly reseat and the leakage
will stop.
15. Minimum differential between operating pressure and set pressure: 5 psig
to 70 psig; set 10% from 71 to 1000
psig; 7% over 1000 psig. See ASME
SEC. VIII Appx. M-M11C.
16. ASME-type pressure valves must be
equipped with lift levers for all air,
steam and hot water (above 140°F
[60°C]) service.
17. Upon installation or after repair, the
proper valve set pressure must be verified. Also, pressure gauges should be
calibrated periodically, insuring proper
system readout.
18. Any water leg between the valve
and gauge must be compensated for.
Otherwise, incorrect pressure readout
will result.
19. Pressure relief valves left on-line
during extended shutdowns should be
inspected and tested before resuming
service. Certain conditions or acts
which often occur during long, unattended idle periods, such as corrosion,
fouling or tampering, may prevent the
device from performing properly. Where
a change in operating conditions follows a shutdown, the inspection
interval must be reviewed.
12. Absolute tightness at seat surfaces is
difficult to achieve. Valve manufacturers
adhere to a commercial seat tightness
standard – API Standard 527.
13. Chatter may result when improper
piping at valve inlet or outlet exists,
or oversizing the valve.
14. Temperature and corrosion effects on
valve materials are very important to
any pressure relief valve application.
Disregard of these critical considerations may damage or cause malfunction
of the pressure relief valve.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
77
Anderson Greenwood Pressure Relief Valves
Technical Manual
Following is an Excerpt from ASME Code Section I,
Section IV, and Section VIII (1995 Addenda)
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
78
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section I, Power Boilers - (1995 Addenda)
Safety Valves and Safety Relief
Valves1
PG-67
Boiler Safety Valve Requirements
steaming capacity as determined by the
Manufacturer and shall be based on the
capacity of all the fuel burning equipment
as limited by other boiler functions.
A93
A93
PG-67.1 Each boiler shall have at least
one safety valve or safety relief valve and
if it has more than 500 sq ft of bare tube
water-heating surface, or if an electric
boiler has a power input more than 1100
kW, it shall have two or more safety
valves or safety relief valves. For a boiler
with combined bare tube and extended
water-heating surface exceeding 500 sq
ft, two or more safety valves or safety relief valves are required only if the design
steam generating capacity of the boiler
exceeds 4000 lb/hr. Organic fluid vaporizer generators require special
consideration as given in Part PVG.
PG-67.2.2 The minimum required relieving capacity for a waste heat boiler shall
be determined by the Manufacturer. When
auxiliary firing is to be used in combination
with waste heat recovery, the maximum
output as determined by the boiler
Manufacturer shall include the effect of
such firing in the total required capacity.
When auxiliary firing is to be used in place
of waste heat recovery, the minimum required relieving capacity shall be based
on auxiliary firing or waste heat recovery,
whichever is higher.
A93
PG-67.2 The safety valve or safety relief
valve capacity for each boiler (except as
noted in PG-67.4) shall be such that the
safety valve, or valves, will discharge all
the steam that can be generated by the
boiler without allowing the pressure to rise
more than 6% above the highest pressure
at which any valve is set and in no case to
more than 6% above the maximum allowable working pressure.
A93
PG-67.2.3 The minimum required
relieving capacity for electric boilers shall
be in accordance with PEB-15.
A93
PG-67.2.4 The minimum required
relieving capacity in lb/hr for a high-temperature water boiler shall be determined
by dividing the maximum output in Btu/hr
at the boiler nozzle, produced by the highest heating valve fuel for which the boiler
is designed, by 1000.
A93
A93
PG-67.2.1 The minimum required relieving capacity of the safety valves or safety
relief valves for all types of boilers shall
not be less than the maximum designed
PG-67.2.5 The minimum required relieving capacity for organic fluid vaporizers
shall be in accordance with PVG-12.
A93
PG-67.2.6 Any economizer which may be
shut off from the boiler, thereby permitting
the economizer to become a fired pressure vessel, shall have one or more safety
relief valves with a total discharge capacity, in lbs/hr, calculated from the maximum
expected heat absorption in Btu/hr, as determined by the Manufacturer, divided by
1000. This absorption shall be stated in
the stamping (PG-106.4).
PG-67.3 One or more safety valves on
the boiler proper shall be set at or below
the maximum allowable working pressure
(except as noted in PG-67.4). If additional
valves are used the highest pressure setting shall not exceed the maximum
allowable working pressure by more than
3%. The complete range of pressure settings of all the saturated-steam safety
valves on a boiler shall not exceed 10% of
the highest pressure to which any valve is
set. Pressure setting of safety relief valves
on high-temperature water boilers2 may
exceed this 10% range.
PG-67.4 For a forced-flow steam generator with no fixed steam and waterline,
equipped with automatic controls and protective interlocks responsive to steam
pressure, safety valves may be provided
in accordance with the above paragraphs
or the following protection against overpressure shall be provided:
Notes
1. Safety Valve: An automatic pressure relieving device actuated by the static pressure
upstream of the valve and characterized by
full opening pop action. It is used for gas or
vapor service.
Relief Valve: An automatic pressure relieving device actuated by the static pressure
upstream of the valve which opens further
with the increase in pressure over the opening pressure. It is used primarily for liquid
service.
Safety Relief Valve: An automatic pressureactuated relieving device suitable for use
either as a safety valve or relief valve, depending on application.
Unless otherwise defined, the definitions relating to pressure relief devices in Appendix
I of ASME/ANSI PTC 25.3, Safety and
Relief Valves, shall apply.
2. Safety relief valves in hot water service are
more susceptible to damage and subsequent leakage, than safety valves relieving
steam. It is recommended that the maximum
allowable working pressure of the boiler and
the safety relief valve setting for high-temperature water boilers be selected
substantially higher than the desired operating pressure so as to minimize the times the
safety relief valve must lift.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
79
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section I, Power Boilers - (1995 Addenda)
PG-67.4.1 One or more power-actuated
pressure relieving valves3 shall be provided
in direct communication with the boiler when
the boiler is under pressure and shall receive a control impulse to open when the
maximum allowable working pressure at the
superheater outlet, as shown in the master
stamping (PG-106.3), is exceeded. The total
combined relieving capacity of the poweractuated relieving valves shall be not less
than 10% of the maximum design steaming
capacity of the boiler under any operating
condition as determined by the Manufacturer.
The valve or valves shall be located in the
pressure part system where they will relieve
the overpressure.
An isolating stop valve of the outsidescrew-and-yoke type may be installed
between the power-actuated pressure
relieving valve and the boiler to permit
repairs provided an alternate poweractuated pressure relieving valve of the
same capacity is so installed as to be
in direct communication with the boiler
in accordance with the requirements of
this paragraph.
Power-actuated pressure relieving valves
discharging to intermediate pressure and
incorporated into bypass and/or startup
circuits by the boiler Manufacturer need
not be capacity certified. Instead, they
shall be marked by the valve manufacturer
with a capacity rating at a set of specified
inlet pressure and temperature conditions.
Power-actuated pressure relieving valves
discharging directly to atmosphere shall
be capacity certified. This capacity certification shall be conducted in accordance
with the provisions of PG-69.3. The valves
shall be marked in accordance with the
provisions of PG.69.4 and PG-69.5.
PG-67.4.2 Spring-loaded safety valves
shall be provided, having a total combined
relieving capacity, including that of the
power-actuated pressure relieving capacity installed under PG-67.4.1, of not less
than 100% of the maximum designed
steaming capacity of the boiler, as determined by the Manufacturer, except the
alternate provisions of PG-67.4.3 are satisfied. In this total, no credit in excess of
30% of the total required relieving capacity shall be allowed for the power-actuated
pressure relieving valves actually installed. Any or all of the spring-loaded
safety valves may be set above the maximum allowable working pressure of the
parts to which they are connected, but the
set pressures shall be such that when all
of these valves (together with the poweractuated pressure relieving valves) are in
operation the pressure will not rise more
than 20% above the maximum allowable
working pressure of any part of the boiler,
except for the steam piping between the
boiler and the prime mover.
PG-67.4.3 The total installed capacity of
spring-loaded safety valves may be less
than the requirements of PG-67.4.2 provided all of the following conditions are met.
PG-67.4.3.1 The boiler shall be of no less
steaming capacity than 1,000,000 lb/hr
and installed in a unit system for power
generation (i.e., a single boiler supplying a
single turbine-generator unit).
PG-67.4.3.2 The boiler shall be provided
with automatic devices, responsive to variations in steam pressure, which include no
less than all the following:
PG-67.4.3.2.1 A control capable of maintaining steam pressure at the desired
operating level and of modulating firing
rates and feedwater flow in proportion to a
variable steam output; and
PG-67.4.3.2.2 A control which overrides
PG-67.4.3.2.1 by reducing the fuel rate
and feedwater flow when the steam pressure exceeds the maximum allowable
working pressure as shown in the master
stamping (PG-106.3) by 10%; and
PG-67.4.3.2.3 A direct-acting overpressure-trip-actuating mechanism, using an
independent pressure sensing device, that
will stop the flow of fuel and feedwater to
the boiler, at a pressure higher than the
set pressure of PG-67.4.3.2.2, but less
than 20% above the maximum allowable
working pressure as shown in the master
stamping (PG-106.3).
PG-67.4.3.3 There shall be not less than
two spring-loaded safety valves and the
total rated relieving capacity of the springloaded safety valves shall be not less than
10% of the maximum designed steaming
capacity of the boiler as determined by the
Manufacturer. These spring-loaded safety
valves may be set above the maximum allowable working pressure of the parts to
which they are connected but shall be set
such that the valves will lift at a pressure
no higher than 20% above the maximum
allowable working pressure as shown in
the master stamping (PG-106.3).
PG-67.4.3.4 At least two of these springloaded safety valves shall be equipped with
a device that directly transmits the valve
stem lift action to controls that will stop the
flow of fuel and feedwater to the boiler.
The control circuitry to accomplish this
shall be arrange in a ‘fail-safe’ manner.4
Notes
3. The power-actuated pressure relieving valve
is one of whose movements to open or close
are fully controlled by a source of power
(electricity, air, steam, or hydraulic). The
valve may discharge to atmosphere or to a
container at lower pressure. The discharge
capacity may be affected by the downstream
conditions, and such effects shall be taken
into account . If the power-actuated pressure
relieving valves are also positioned in response other control signals, the control
impulse to prevent overpressure shall be responsive only to pressure and shall override
any other control function.
4. ‘Fail-safe’ shall mean a circuitry arranged as
either of the following:
(1) Energize to trip: There shall be at least
two separate and independent trip circuits served by two power sources, to
initiate and perform the trip action. One
power source shall be a continuously
charged dc battery. The second source
shall be an ac-to-dc converter connected
to the dc system to charge the battery
and capable of performing the trip action. The trip circuits shall be
continuously monitored for availability.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
80
It is not mandatory to duplicate the
mechanism that actually stops the flow of
fuel and feedwater.
(2) De-energize to trip: If the circuits are
arranged in such a way that a continuous supply of power is required to keep
the circuits closed and operating and
such that any interruption of power
supply will actuate the trip mechanism,
then a single trip circuit and single power
supply will be enough to meet the
requirements of this subparagraph.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section I, Power Boilers - (1995 Addenda)
PG-67.4.3.5 The power supply for all controls and devices required by PG-67.4.3
shall include at least one source contained
within the same plant as the boiler and
which is arranged to actuate the controls
and devices continuously in the event of
failure or interruption of any other power
sources.
PG-67.4.4 When stop valves are
installed in the water-steam flow path between any two sections of a forced-flow
steam generator with no fixed steam and
waterline:
PG-67.4.4.1 The power-actuated pressure relieving valve(s) required by
PG-67.4.1 shall also receive a control impulse to open when the maximum
allowable working pressure of the component, having the lowest pressure level
upstream to the stop valve, is exceeded;
and
PG-67.4.4.2 The spring-loaded safety
valves shall be located to provide the
pressure protection requirements in PG67.4.2 or PG-67.4.3.
PG-67.4.5 A reliable pressure-recording
device shall always be in service and
records kept to provide evidence of conformity to the above requirements.
PG-67.5 All safety valves or safety relief
valves shall be so constructed that the
failure of any part cannot obstruct the free
and full discharge of steam and water
from the valve. Safety valves shall be of
the direct spring-loaded pop type, with
seat inclined at any angle between 45
degrees and 90 degrees, inclusive, to the
center line of the spindle. The coefficient
of discharge of safety valves shall be
determined by actual steam flow measurements at a pressure not more than
3% above the pressure at which the valve
is set to blow and when adjusted for blowdown in accordance with PG-72. The
valves shall be credited with capacities as
determined by the provisions of PG-69.2
Safety valves or safety relief valves may
be used which give any opening up to the
full discharge capacity of the area of the
opening of the inlet of the valve (see PG69.5), provided the movement of the
steam safety valve is such as not to induce lifting of water in the boiler.
Deadweight or weighted lever safety
valves or safety relief valves shall not be
used.
For high-temperature water boilers safety
relief valves shall be used. Such valves
shall have a closed bonnet. For purposes
of selection the capacity rating of such
safety relief valves shall be expressed in
terms of actual steam flow determined on
the same basis as for safety valves. In addition the safety relief valves shall be
capable of satisfactory operation when relieving water at the saturation temperature
corresponding to the pressure at which
the valve is set to blow.
PG-67.6 A safety valve or safety relief
valve over 3-inch in size, used for pressures greater than 15 psig, shall have a
flanged inlet connection or weld-end inlet
connection. The dimensions of flanges
subjected to boiler pressure shall conform
to the applicable American National
Standards as given in PG-42. The facing
shall be similar to those illustrated in the
Standard.
PG-67.7 Safety valves or safety relief
valves may have bronze parts complying
with either SB-61 or SB-62, provided the
maximum allowable stresses and temperatures do not exceed the values given in
Table 1B of Section II, Part D, and shall
be marked to indicate the class of material
used. Such valves shall not be used on
superheaters delivering steam at a temperature over 450°F and 306°F respectively,
and shall not be used for high-temperature
water boilers.
PG-68 Superheater Safety Valve
Requirements
PG-68.1 Except as permitted in PG58.3.1, every attached superheater shall
have one or more safety valves in the
steam flow path between the superheater
outlet and first stop valve. The location
shall be suitable for the service intended
and shall provide the overpressure protection required. The pressure drop upstream
of each safety valve shall be considered in
the determination of set pressure and relieving capacity of that valve. If the
superheater outlet header has a full, free
steam passage from end to end and is so
constructed that steam is supplied to it at
practically equal intervals throughout its
length so that there is a uniform flow of
steam through the superheater tubes and
the header, the safety valve, or valves,
may be located anywhere in the length of
the header.
PG-68.2 The discharge capacity of the
safety valve, or valves, on an attached
superheater may be included in determining the number and size of the safety
valves for the boiler, provided there are
no intervening valves between the superheater safety valve and the boiler, and
provided the discharge capacity of the
safety valve, or valves, on the boiler, as
distinct from the superheater is at least
75% of the aggregate valve capacity
required.
PG-68.3 Every independently fired superheater which may be shut off from the
boiler and permit the superheater to become a fired pressure vessel shall have
one or more safety valves having a discharge capacity equal to 6 lb of steam per
hour per square foot of superheater surface measured on the side exposed to the
hot gases. In the case of electrically heated superheaters, the safety valve capacity
shall be based upon 31/2 lb/hr/kW input.
The number of safety valves installed
shall be such that the total capacity is at
least equal to that required.
PG-68.4 Every reheater shall have one or
more safety valves, such that the total relieving capacity is at least equal to the
maximum steam flow for which the reheater is designed. At least one valve
shall be located in the stamp flow path between the reheater outlet and the first stop
valve. The location shall be suitable for
the service intended and shall provide the
overpressure protection required. The
pressure drop upstream of each safety
valve shall be considered in the determination of set pressure and relieving
capacity of that valve. The relieving capacity of that valve shall be not less than
15% of the required total. The capacity of
reheater safety valves shall not be included in the required relieving capacity for
the boiler and superheater.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
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ASME Code Section I, Power Boilers - (1995 Addenda)
PG-68.5 A soot blower connection may
be attached to the same outlet from the
superheater or reheater that is used for
the safety valve connection.
PG-68.6 Every safety valve used on a
superheater or reheater discharging
superheated steam at a temperature over
450°F shall have a casing, including the
base, body, and bonnet and spindle, of
steel, steel alloy, or equivalent heat-resisting material.
The valve shall have a flanged inlet connection, or a weld-end inlet connection.
It shall have the seat and disk of suitable
heat erosive and corrosive resisting material, and the spring fully exposed outside
of the valve casing so that it shall be protected from contact with the escaping
steam.
PG-69 Certification of Capacity of
Safety and Safety Relief Valves
PG-69.1 Before the Code symbol is applied to any safety or safety relief valve,
the valve manufacturer shall have the relieving capacity of his valves certified in
accordance with the provisions of this
paragraph.
PG-69.1.1 Capacity certification tests
shall be conducted using dry saturated
steam. The limits for test purposes shall
be 98% minimum quality and 20°F maximum superheat. Correction from within
these limits may be made to the dry saturated condition.
PG-69.1.2 Tests shall be conducted at a
place which meets the requirements of
Appendix A-312.
A92
PG-69.1.3 Capacity test data reports for
each valve design and size, signed by the
manufacturer and Authorized Observer
witnessing the tests, together with drawings showing the valve construction, shall
be submitted to the ASME designee for
review and acceptance.5
measured capacity
absolute flow rating pressure, psia
PG-69.1.4 Capacity certification tests
shall be conducted at a pressure which
does not exceed the set pressure by 3%
or 2 psi, whichever is greater. Safety and
safety relief valves shall be adjusted so
that the blowdown does not exceed 4%
of the set pressure. For valves set at or
below 100 psi, the blowdown shall be adjusted so as not to exceed 4 psi. Safety
valves used on forced-flow steam generators with no fixed steam and waterline,
and safety relief valves used on high-temperature water boilers shall be adjusted
so that the blowdown does not exceed
10% of the set pressure. The reseating
pressure shall be noted and recorded.
If all slopes derived from the testing do
not fall within ±5% of the average slope,
the Authorized Observer shall require two
additional valves to be tested as replacements for each valve having a slope
outside this range, with a limit of four additional valves. Failure of any slope to fall
within ±5% of the new average slope, excluding the replaced valve(s), shall be
cause to refuse certification of that particular valve design.
PG-69.2 Relieving capacities shall be
determined using one of the following
methods.
The rated relieving capacity to be
stamped on the valve shall be determined
as follows:
PG-69.2.1 Three Valve Method.
A capacity certification test is required on
a set of three valves for each combination
of size, design and pressure setting. The
capacity of each valve of the set shall fall
within a range of ±5% of the average capacity. If one of the three valves tested
falls outside this range, it shall be replaced by two valves, and a new average
shall be calculated based on all four
valves, excluding the replaced valve.
Failure of any of the four capacities to fall
within a range of ±5% of the new average
shall be cause to refuse certification of
that particular valve design.
rated relieving capacity
= 0.90 x average slope x (1.03 x set
pressure + 14.7)
The rated relieving capacity for each combination of design, size, and test pressure
shall be 90% of the average capacity.
PG-69.2.2 Four Valve Method.
Four valves of each combination of valve
inlet size and orifice size shall be tested.
These four valves shall be set at pressures
covering the range for which the valves will
be used or the range available at the certified test facility where tests are conducted.
The slope of the actual measured capacity versus the absolute flow rating pressure
for each test point shall be calculated and
averaged:
Slope =
All values derived from the testing must
fall within ±5% of the average slope.
or
= 0.90 x average slope x (set pressure
+ 2 psi + 14.7)
whichever is greater.
PG-69.2.3 Coefficient of Discharge
Method.
A coefficient of discharge for the design,
K, may be established for a specific valve
design according to the following procedure.
A. For each design, the safety or safety
relief valve manufacturer shall submit for
test at least three valves for each of three
different sizes (a total of nine valves).
Each valve of a given size shall be set
at a different pressure, covering the range
of pressures for which the valve will be
used or the range available at the facility
where the tests are conducted.
B. Tests shall be made on each safety
or safety relief valve to determine its lift at
capacity, popping, and blowdown pressures, and actual relieving capacity.
Notes
5. Valve capacities are published in ‘Pressure
Relief Device Certifications.’ This publication may be obtained from the National
Board of Boiler and Pressure Vessel
Inspectors, 1055 Crupper Ave., Columbus,
OH 43229.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
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ASME Code Section I, Power Boilers - (1995 Addenda)
An individual coefficient, KD, shall be
established for each valve as follows:
KD =
Actual flow
Theoretical flow
=
Individual coefficient of discharge
Where actual flow is determined by test
and theoretical flow, WT is calculated by
one of the following equations:
For 45 degree seat
WT = 51.45 x πDLP x 0.707
For flat seat
WT = 51.45 x πDLP
WT = theoretical flow, defined by the same
equation used to determine KD, lb/hr
K = coefficient of discharge for the design
The coefficient of discharge for the design, K, shall not be greater than 0.975.
The coefficient shall not be applied to
valves whose beta ratio (ratio of valve
throat to inlet diameter) lies outside the
range of 0.15 to 0.75, unless tests have
demonstrated that the individual coefficient of discharge, KD, for valves at the
extreme ends of a larger range, is within
±5% of the coefficient, K.
For nozzle
WT = 51.45 AP
where:
WT = theoretical flow, lb/hr
A = nozzle throat area, in2
P = (1.03 x set pressure + 14.7), or
= (set pressure + 2 + 14.7),
whichever is greater, psia
L = lift pressure at P, in.
D = seat diameter, in.
The coefficient of discharge for the design,
K, shall be the average of the nine individual
coefficients, KD. All individual coefficients
of discharge, KD, shall fall within a range
of ±5% of the coefficient, K. If a valve fails
to meet this requirement, the Authorized
Observer shall require two additional
valves to be tested as replacements for
each valve having an individual coefficient, KD, outside the ±5% range, with a
limit of four additional valves. Failure of
a coefficient, KD, to fall within ±5% of the
new average value, excluding the replaced valve(s), shall be cause to refuse
certification of that particular valve design.
The rated relieving capacity of all sizes
and set pressures of a given design, for
which K has been established under the
provision of this paragraph, shall be determined by the equation:
For designs where the lift is used to determine the flow area, all valves shall have the
same nominal lift to seat diameter ratio (L/D).
For pressures over 1500 psig and up to
3200 psig, the value of W shall be multiplied by the correction factor:
0.1906P - 1000
0.2292P - 1061
PG-69.3 If a manufacturer wishes to apply the Code symbol to a power-actuated
pressure relieving valve under PG-67.4.1,
one valve of each combination of inlet
pipe size and orifice size to be used with
that inlet pipe size shall be tested. The
valve shall be capacity tested at four different pressures approximately covering
the range of the certified test facility on
which the tests are conducted. The capacities, as determined by these four tests,
shall be plotted against the absolute flow
test pressure and a line drawn through
these four test points. All points must lie
within ±5% in capacity value of the plotted
line and must pass through 0-0. From the
plotted line, the slope of the line dW/dP
shall be determined and a factor of
(0.90/51.45) x (dW/dP) shall be applied to
capacity computations in the supercritical
region at elevated pressures by means of
the isentropic flow equation.6
W = WT x K x 0.9
where:
W = rated relieving capacity, lb/hr
0.90
dW
W = 1135.8 ––––––– x –––
51.45
dP
––––––
P
–––
ν
√
Notes
6. The constant 1135.8 is based on a γ factor
of 1.30 which is accurate for superheated
steam at temperature above approximately
800°F. In interest of accuracy, other meth-
where:
W = capacity, lb of steam/hr
P = absolute inlet pressure, psia
ν = inlet specific volume, cu ft/lb
dW/dP = rate of change of measured
capacity with respect to absolute
pressure
A92
PG-69.4 Power-actuated pressure
relieving valves, having capacities certified in accordance with the provision of
PG-69.3 and computed in accordance
with the formula contained therein, shall
be marked as required by PG-110 with the
computed capacity, corresponding to 3%
above the full load operating pressure and
temperature conditions at the valve inlet
when the valve is operated by the controller, and they shall also be stamped
with the set pressure of the controller.
When the valve is marked as required by
this paragraph, it shall be the guarantee
by the manufacturer that the valve also
conforms to the details of construction
herein specified.
A92
PG-69.6 When changes are made in the
design of a safety or safety relief valve in
such a manner as to affect the flow path,
lift, or performance characteristics of the
valve, new tests in accordance with this
Section shall be performed.
PG-70 Capacity of Safety Valves
A93
PG-70.1 Subject to the minimum number
required by PG-67.1, the number of safety
valves or safety relief valves required shall
be determined on the basis of the maximum designed steaming capacity, as
determined by the boiler Manufacturer,
and the relieving capacity marked on the
valves by the manufacturer.
In many cases a greater relieving capacity
of safety valves or safety relief valves will
have to be provided than the minimum
specified by this rule, and in every case
the requirements of PG-67.2 shall be met.
ods of capacity computations must be used
at temperatures below 800°F at supercritical
pressures.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
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Anderson Greenwood Pressure Relief Valves
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ASME Code Section I, Power Boilers - (1995 Addenda)
PG-71 Mounting
PG-71.1 When two or more safety valves
are used on a boiler, they may be mounted either separately or as twin valves
made by placing individual valves on
Y-bases, or duplex valves having two
valves in the same body casing. Twin
valves made by placing individual valves
on Y-bases, or duplex valves having two
valves in the same body, shall be of
approximately equal capacity.
to be carried clear from running boards
or platforms. Ample provision for gravity
drain shall be made in the discharge pipe
at or near each safety valve or safety
relief valve, and where water of condensation may collect. Each valve shall have
an open gravity drain through the casing
below the level of the valve seat. For
iron- and steel-bodied valves exceeding
21/2-inch size, the drain hole shall be
tapped not less than 3/8-inch pipe size.
When not more than two valves of different sizes are mounted singly the relieving
capacity of the smaller valve shall be not
less than 50% of that of the larger valve.
Discharge piping from safety relief valves
on high-temperature water boilers shall be
provided with adequate provisions for water drainage as well as the steam venting.
PG-71.2 The safety valve or safety relief
valve or valves shall be connected to the
boiler independent of any other connection, and attached as close as possible to
the boiler or the normal steam flow path,
without any unnecessary intervening pipe
or fitting. Such intervening pipe or fitting
shall be not longer than the face-to-face
dimension of the corresponding tee fitting
of the same diameter and pressure under
the applicable American National
Standard listed in PG-42 and shall also
comply with PG-8 and PG-39. Every safety valve or safety relief valve shall be
connected so as to stand in an upright
position, with spindle vertical. On hightemperature water boilers of the
watertube forced-circulation type, the
valve shall be located at the boiler outlet.
The installation of cast iron bodied safety
relief valves for high-temperature water
boilers is prohibited.
PG-71.3 The opening or connection between the boiler and the safety relief valve
shall have at least the area of the valve inlet. No valve of any description shall be
placed between the required safety valve
or safety relief valve or valves and the
boiler, nor on the discharge pipe between
the safety valve or safety relief valve and
the atmosphere. When a discharge pipe is
used, the cross-sectional area shall be not
less than the full area of the valve outlet
or of the total of the areas of the valve
outlets, discharging thereinto. It shall be
as short and straight as possible and so
arranged as to avoid undue stresses on
the valve or valves.
All safety valve or safety relief valve discharges shall be so located or piped as
PG-71.4 If a muffler is used on a safety
valve or safety relief valve, it shall have
sufficient outlet area to prevent back
pressure from interfering with the proper
operation and discharge capacity of the
valve. The muffler plates or other devices
shall be so constructed as to avoid a
possibility of restriction of the steam passages due to deposit. Mufflers shall not
be used on high-temperature water boiler
safety relief valves.
When a safety valve or safety relief valve
is exposed to outdoor elements which may
affect operation of the valve, it is permissible to shield the valve with a satisfactory
cover. The shield or cover shall be properly vented and arranged to permit servicing
and normal operation of the valve.
PG-71.5 When a boiler is fitted with two
or more safety relief valves on one connection, this connection to the boiler shall
have a cross-sectional area not less than
the combined areas of inlet connections of
all the safety valves or safety relief valves
with which it connects and shall also meet
the requirements of PG-71.3.
PG-71.6 Safety valves may be attached
to drums or headers by welding provided
the welding is done in accordance with
Code requirements.
PG-71.7 Every boiler shall have proper
outlet connections for the required safety
valve, or safety relief valve, or valves, in-
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
84
dependent of any other outside steam
connection, the area of opening to be at
least equal to the aggregate areas of inlet
connections of all of the safety valves or
safety relief valves to be attached thereto.
An internal collecting pipe, splash plate, or
pan may be used, provided the total area
for inlet of steam thereto is not less than
twice the aggregate areas of the inlet connections of the attached safety valves.
The holes in such collecting pipes shall be
at least 1/4-inch in diameter and the least
dimension in any other form of opening for
inlet of steam shall be 1/4-inch.
Such dimensional limitations to operation
for steam need not apply to steam scrubbers or driers provided the net free steam
inlet area of the scrubber or drier is at
least 10 times the total area of the boiler
outlets for the safety valves.
PG-71.8 If safety valves are attached
to a separate steam drum or dome, the
opening between the boiler proper and
the steam drum or dome shall be not less
than required by PG-71.7.
PG-72 Operation
PG-72.1 Safety valves shall be designed
and constructed to operate without chattering and to attain full lift at a pressure no
greater than 3% above their set pressure.
After blowing down, all valves shall close
at a pressure not lower than 96% of their
set pressure, except that all drum valves
installed on a single boiler may be set to
reseat at a pressure not lower than 96% of
the set pressure of the lowest set drum
valve. The minimum blowdown for springloaded safety or safety relief valves shall be
2% of the set pressure, except that for boilers whose maximum allowable working
pressure is less than 100 psi, the valves
may be set to reseat between 2 and 4 psi
below their set pressure.
Safety valves used on forced-flow steam
generators with no fixed steam and waterline, and safety relief valves used on
high-temperature water boilers may be
set and adjusted to close after blowing
down not more than 10% of the set pressure. The valves for these special uses
must be so adjusted and marked by the
manufacturer.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section I, Power Boilers - (1995 Addenda)
PG-72.2 The popping point tolerance
plus or minus shall not exceed the following: 2 psi for pressures up to and
including 70 psi, 3% for pressures over 70
psi up to and including 300 psi, 10 psi for
pressures over 300 psi up to and including 1000 psi, and 1% for pressures over
1000 psi.
PG-72.3 The spring in a safety valve or
safety relief valve shall not be reset for any
pressure more than 5% above or below that
for which the valve is marked unless the
new setting is within the spring design range
established by the manufacturer or is determined to be acceptable to the manufacturer.
If the set pressure is to be adjusted within
the limits specified above, the adjustment
shall be performed by the manufacturer, his
authorized representative, or an assembler.
An additional valve data tag identifying the
new set pressure, capacity, and date shall
be furnished and installed, and the valved
shall be resealed.
PG-72.4 If the set pressure of a valve is
changed so as to require a new spring,
the spring shall be acceptable to the manufacturer. The spring installation and valve
adjustment shall be performed by the
manufacturer, his authorized representative, or an assembler. A new nameplate as
described in PG-110 shall be furnished
and installed, and the valve shall be resealed.
PG-73 Minimum Requirements for
Safety and Safety Relief Valves
PG-73.1 Mechanical Requirements
PG-73.1.1 The design shall incorporate
guiding arrangements necessary to insure
consistent operation and tightness.
PG-73.1.2 The spring shall be
designed so that the full lift spring compression shall be no greater than 80%
of the nominal solid deflection. The permanent set of the spring (defined as the
difference between the free height and
height measured 10 min after the spring
has been compressed solid three additional times after presetting at room
temperature) shall not exceed 0.5% of the
free height.
PG-73.1.3 To provide a means for verifying whether it is free, each safety valve
or safety relief valve shall have a substantial lifting device, which when
activated will release the seating force on
the disk when the valve is subject to
pressure of at least 75% of the set pressure. The lifting device shall be such that
it cannot lock or hold the valve disk in lifted position when the exterior lifting force
is released. Disks of safety relief valves
used on high-temperature water boilers
shall not be lifted while the temperature
of the water exceeds 200°F. If it is desired to lift the valve disk to assure that it
is free, this shall be done when the valve
is subjected to a pressure of at least 75%
of the set pressure. For high-temperature
water boilers, the lifting mechanism shall
be sealed against leakage.
stalled in such a manner as to prevent
changing the adjustment without breaking
the seal and, in addition, shall serve as a
means of identifying the manufacturer, his
authorized representative, or the assembler making the adjustment.
PG-73.1.4 The seat of a safety valve
shall be fastened to the body of the valve
in such a way that there is no possibility of
the seat lifting.
PG-73.2.3 Materials used in bodies and
bonnets or yokes shall be listed in Section
II, Parts A and B, and identified in Tables
1A and 1B of Section II, Part D, as permitted for Section I construction. Materials
used in nozzles, disks, and other parts contained within the external structure of the
safety or safety relief valves shall be one of
the following categories:
PG-73.1.5 A body drain below seat level
shall be provided in the valve and this
drain shall not be plugged during or after
field installation. For valves exceeding
21/2-inch pipe size, the drain hole or holes
shall be tapped not less than 3/8-inch pipe
size. For valves of 21/2-inch pipe size or
smaller, the drain hole shall not be less
than 1/4-inch in diameter.
PG-73.1.6 In the design of the body of
the valve, consideration shall be given to
minimizing the effects of water deposits.
PG-73.1.7 Valves having screwed
inlet or outlet connections shall be provided with wrenching surfaces to allow for
normal installation without damaging operating parts.
A92
PG-73.1.8 Means shall be provided in the
design of all valves for use under this
Section, for sealing all external adjustments. Seals shall be installed by the
manufacturer, his authorized representative, or an assembler at the time of the
initial adjustment. After spring replacement and/or subsequent adjustment, the
valve shall be resealed. Seals shall be in-
PG-73.2 Material Selections
PG-73.2.1 Cast iron seats and disks are
not permitted.
PG-73.2.2 Adjacent sliding surfaces such
as guides and disks or disk holders shall
both be of corrosion resistant material.
Springs of corrosion resistant material or
having a corrosion resistant coating are
required. The seats and disks of safety
valves or safety relief valves shall be of
suitable material to resist corrosion by the
lading fluid.7
1. listed in ASME Section II;
2. listed in ASTM Specifications;8
3. controlled by the manufacturer of the
safety or safety relief valve by a specification insuring control of chemical and
physical properties and quality at least
equivalent to ASTM Standards.8
Notes
7. The degree of corrosion resistance, appropriate to the intended service, shall be a
matter of agreement between the manufacturer and purchaser.
8. It shall be the manufacturer’s responsibility
to insure that the allowable stressed at temperature meet the requirements of Section
II, Part D, Appendix 1, Nonmandatory Basis
for Establishing Stress Values in Table 1A
and 1B.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
85
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section I, Power Boilers - (1995 Addenda)
PG-73.3 Inspection of Manufacturing
and/or Assembly
A92/A93
PG-73.3.1 A manufacturer shall demonstrate to the satisfaction of an ASME
designee that his manufacturing, production, and test facilities and quality control
procedures will insure close agreement
between the performance of random production samples and the performance of
those valves submitted for capacity certification.
A93
4. Failure of any of the replacement valves
to meet the capacity or the performance
requirements of this Section shall be
cause for revocation within 60 days of
the authorization to use the Code symbol on that particular type of valve.
During this period, the Manufacturer or
assembler shall demonstrate the cause
of such deficiency and the action taken
to guard against future occurrence, and
the requirements of PG-73.3.3 above
shall apply.
A93
PG-73.3.2 Manufacturing, assembly,
inspection, and test operations including
capacity, are subject to inspections at any
time by an ASME designee.
PG-73.3.4 Use of the Code Symbol
Stamp by an assembler indicates the use
of original unmodified parts in strict accordance with the instructions of the
manufacturer of the valve.
A92/A93
A93
PG-73.3.3 A Manufacturer or assembler
may be granted permission to apply the V
Code Symbol to production pressure relief
valves capacity-certified in accordance
with PG-69, provided the following tests
are successfully completed. This permission shall expire on the fifth anniversary of
the date it is initially granted. This permission may be extended for 5 year periods if
the following tests are successfully repeated within the 6 month period before
expiration.
PG-73.3.5 In addition to the requirements
of PG-110, the same plate marking shall
include the name of the Manufacturer and
the assembler. The Code Symbol Stamp
shall be that of the assembler.9
1. Two sample production pressure relief
valves of a size and capacity within the
capability of an ASME accepted laboratory shall be selected by an ASME
designee.
2. Operational and capacity tests shall be
conducted in the presence of an ASME
designee at an ASME accepted laboratory. The valve manufacturer or
assembler shall be notified of the time
of the test and may have representatives present to witness the test.
3. Should any valve fail to relieve at or
above its certified capacity or should it
fail to meet performance requirements
of this Section, the test shall be repeated at the rate of two replacement
valves, selected in accordance with
PG-73.3.3(1), for each valve that failed.
PG-73.4 Testing by Manufacturers or
Assemblers
PG-73.4.1 Valves exceeding 1-inch inlet
size or 300 psig set pressure shall meet
the following requirements. Primary pressure containing cast and welded parts of
pressure relief valves shall be tested at a
pressure at 1.5 times the design pressure
of the parts. These tests shall be conducted after all machining operations to the
parts have been completed. There shall
be no visible signs of leakage.
Closed bonnet pressure relief valves designed for discharge to a closed system
shall be tested with a minimum of 30 psig
air or other gas in the secondary pressure
zone. There shall be no visible signs of
leakage.
PG-73.4.2 Every valve shall be tested
with steam by the manufacturer or assembler to demonstrate the popping point,
blowdown, tightness, and pressure containing integrity. Valves beyond the
capability of production test facilities may
be shop tested with air, provided required
field tests and applicable adjustments are
made.
PG-73.4.3 A seat tightness test shall be
conducted at maximum expected operating pressure, but at a pressure not
exceeding the reseating pressure of the
valve. When being tested, a valve exhibiting no visible signs of leakage shall be
considered adequately tight.
A92
PG-73.4.4 A manufacturer or assembler
shall have a documented program for the
application, calibration, and maintenance
of test gauges.
PG-73.4.5 Testing time on steam valves
shall be sufficient to assure that test results are repeatable and representative of
field performance.
A92
PG-73.4.6 Test fixtures and test drums,
where applicable, shall be of adequate
size and capacity to assure that the observed set pressure is consistent with the
stamped set pressure within the tolerance
required by PG-72.2.
PG-73.5 Design Requirements
At the time of submission of valves for
capacity certification or testing in accordance with PG-69, the ASME designee
has the authority to review design for conformity with the requirements of this
Section and to reject or require modification of designs which do not conform, prior
to capacity testing.
Notes
9. Within the requirements of PG-73.3 and PG73.4, a manufacturer is defined as a person
or organization who is completely responsible for design, material selection, capacity
certification, manufacture of all component
parts, assembly, testing, sealing, and shipping of safety and safety relief valves
certified under this Section.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
86
An assembler is defined a person or organization who purchases or receives from a
manufacturer the necessary component
parts or valves and assembles, adjusts,
tests, seals, and ships safety or safety relief
valves certified under this Section at a geographical location other than and using
facilities other than those used by the manufacturer.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section I, Power Boilers - (1995 Addenda)
PFT-44 Opening Between Boiler
and Safety Valve
The opening or connection between the
boiler and the safety valve shall have at
least the area of the valve inlet. In the
case of firetube boilers, the openings in
the boilers for safety valves or safety relief
valves shall be not less than given in
Table PFT-44, except firetube boilers used
for waste heat purposes only, not
equipped for direct firing, need not meet
the requirements of Table PFT-44 provid-
ed the rated steaming capacity is stamped
on the boiler and safety valves or safety
relief valves of the required relieving capacity are supplied such that the
provisions of PG-67.2 are satisfied.
After the boiler Manufacturer provides for
the opening required by the Code, a bushing may be inserted in the opening in the
shell to suit a safety valve that will have
the capacity to relieve all the steam that
can be generated in the boiler and which
will meet the Code requirements.
No valve of any description shall be
placed between the required safety valve
or safety relief valve or valves and the
boiler, or on the discharge pipe between
the safety valve or safety relief valve and
the atmosphere. When a discharge pipe is
used, the cross-sectional area shall be not
less than the full area of the valve outlet or
of the total of the areas of the valve outlets discharging thereinto and shall be as
short and straight as possible and so
arranged as to avoid undue stresses on
the valve or valves.
Table PFT-44
Minimum Total Areas of Openings (in2) in Firetube Boilers for Safety Valve Connections 1, 2
Gauge
Press.
psi 100
Boiler Heating Surface, sq. ft.
200
300
400
500
600
800
1000
1200
1400
1600
1800
2000
2500
3000
V
16
3.174
6.348
9.522
12.696
15.869
19.043
25.392
31.739
38.086
44.435
50.783
57.130
63.478
79.347
95.216 13.330
25
2.500
5.000
7.499
10.000
12.498
15.000
20.000
24.996
30.000
35.000
40.000
44.992
49.992
62.489
74.987 10.498
50
1.584
3.168
4.752
6.338
7.920
9.504
12.677
15.839
19.007
22.175
25.354
28.510
31.678
39.599
47.517
6.655
75
1.166
2.331
3.497
4.663
5.828
6.995
9.326
11.657
13.989
16.320
18.652
20.983
23.314
29.143
34.972
4.896
100
0.924
1.849
2.773
3.697
4.621
5.546
7.394
9.243
11.092
12.940
14.789
16.637
18.486
23.106
27.729
3.882
125
0.767
1.533
2.300
3.067
3.834
4.600
6.134
7.667
9.201
10.734
12.267
13.800
15.334
19.166
23.000
3.220
150
0.655
1.311
1.966
2.621
3.276
3.932
5.242
6.553
7.863
9.174
10.484
11.795
13.106
16.382
19.658
2.752
175
0.572
1.145
1.718
2.289
2.862
3.435
4.579
5.725
6.870
8.015
9.158
10.305
11.450
14.312
17.175
2.404
200
0.508
1.016
1.525
2.033
2.541
3.049
4.066
5.082
6.099
7.115
8.132
9.148
10.164
12.706
15.247
2.1345
225
0.457
0.913
1.370
1.827
2.284
2.740
3.654
4.567
5.481
6.394
7.308
8.221
9.134
11.417
13.702
1.9183
250
0.415
0.830
1.244
1.659
2.074
2.489
3.318
4.148
4.978
5.807
6.637
7.466
8.296
10.370
12.444
1.7422
Nominal Pipe
Size, Inch
1/2
3/4
1
Internal
Diameter
Internal
Area, in2
0.622
0.304
2
2.067
0.824
0.533
21/2
1.049
0.864
3
31/2
11/4
1.380
1.495
11/2
1.610
2.036
Nominal Pipe Internal
Size, inch Diameter
Internal
Area, in2
Nominal Pipe
Size, inch
Internal
Diameter
Internal
Area, in2
3.355
4
4.026
12.730
2.469
4.788
5
5.047
20.006
3.068
7.393
6
6.065
28.891
3.548
9.886
8
8.071
51.161
Notes
1. Based on formula A = HV/420
where
A = total area of openings, in 2
H = boiler heating surface, ft 2
V = specific volume of steam in cu. ft/lb at
maximum allowable working pressure.
2. Number and size of openings shall provide
for not less than the area given.
Intermediate values may be interpolated.
With flanged openings, use internal area for
determining diameter.
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designs and specifications without notice.
87
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section I, Miniature Boilers - (1995 Addenda)
PMB-15 Safety Valves
Each miniature boiler shall be equipped
with a sealed spring loaded safety valve
of not less than NPS 1/2.
without allowing the pressure to rise more
than 6% above the maximum allowable
working pressure.
The minimum relieving capacity of the
safety valve shall be determined in accordance with PG-70. In addition to these
requirements, the safety valve shall have
sufficient capacity to discharge all the
steam that can be generated by the boiler
All other provisions for safety valves in
this Section shall be complied with.
ASME Code Section I, Electric Boilers - (1995 Addenda)
PEB-15 Safety Valves
PEB-15.1 Each electric boiler shall have
at least one safety valve or safety
relief valve, and if it has a power input
more than 1100 kW, it shall have two or
more safety valves or safety relief valves.
PEB-15.2 The minimum safety valve or
safety relief valve relieving capacity for
electric boilers shall be 31/2 lb/hr/kW input.
ASME Code Section I, Organic Vapor Generator - (1995 Addenda)
PVG-12.1 Safety valves shall be of a totally enclosed type so designed that
vapors escaping beyond the valve seat
shall not discharge into the atmosphere,
except through an escape pipe that will
carry such vapors to a safe point of discharge outside of the building. A suitable
condenser that will condense all the vapors discharged from the safety valve
may be used in lieu of piping the vapors to
the atmosphere. The safety valve shall not
have a lifting lever. The vaporizer shall be
designed in accordance with the rules in
this Code for a working pressure of at
least 40 psi above the operating pressure
at which it will be used. Valve body drains
are not mandatory.
Figure PVG-12
Constant C For Vapor Related to Ratio of Specific Heats (k = Cp/Cv)
400
390
380
Constant, C
PVG-12 Safety Valves
PVG-12.3.1 The cross-sectional area of
the connection to a vaporizer shall be not
less than the required relief area of the
rupture disk.
PVG-12.3.2 Every rupture disk shall
have a specified bursting pressure at a
specified temperature, shall be marked
with a lot number, and shall be guaranteed by its manufacturer to burst within
360
350
Flow Formula Calculations
340
PVG-12.2 Safety valves shall be disconnected from the vaporizer at least once
yearly, when they shall be inspected, repaired if necessary, tested, and then
replaced on the vaporizer.
PVG-12.3 In order to minimize the loss
by leakage of material through the safety
valve, a rupture disk may be installed between the safety valve and the vaporizer
provided the following requirements are
met.
370
W = K (CAP
330
C = 520
k
M/T)
( k +2 1 (
k+1
k-1
320
▲
1.0
▲
1.2
▲
1.6
▲
1.4
▲
1.8
▲
2.0
k
5% (plus or minus) of its specified bursting pressure.
PVG-12.3.3 The specified bursting
pressure at the coincident operating temperature shall be determined by bursting
two or more specimens from a lot of the
same material and of the same size as
those to be used. The tests shall be made
in a holder of the same form and pressure
area dimensions as that with which the
disk is to be used.
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designs and specifications without notice.
88
PVG-12.3.4 A rupture disk may be
installed between a safety valve and the
vaporizer provided:
PVG-12.3.4.1 The maximum pressure of
the range for which the disk is designed to
rupture does not exceed the opening
pressure for which the safety valve is set
or the maximum allowable working pressure of the vessel.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section I, Organic Vapor Generator (1995 Addenda)
PVG-12.3.4.2 The opening provided
through the rupture disk, after breakage, is
sufficient to permit a flow equal to the capacity of the attached valve and there is
no chance of interference with the proper
functioning of the valve; but in no case
shall this area be less than the inlet area
of the valve.
PVG-12.3.4.3 The space between a rupture disk and the valve should be provided
with a pressure gauge, try cock, free vent,
or a suitable telltale indicator. This
arrangement permits the detection of disk
rupture or leakage.1
PVG-12.4 Safety valve discharge capacity
shall be determined from the formula:
W = (0.90)CKAP
––––
√ M/T
where:
W = flow of vapor, lb/hr
C = constant for vapor which is a function
of the ratio of Specific Heats
k = Cp /Cv (see Fig. PVG-12) Note:
Where k is not known, k = 1.001.
K = average coefficient of discharge
PVG-12.5 Safety valves for organic fluid
vaporizers shall be tested and certified under PG-69, and they shall be stamped
with the rated relieving capacity in pounds
per hour at coincident temperature as
determined in PVG-12.4 The fluid identification shall be stamped on the nameplate.
PVG-12.6 The required minimum safety
valve relieving capacity shall be determined from the formula:
W = C x H x 0.75
h
where:
h = latent heat of heat transfer fluid at
relieving pressure, BTU/lb
W = weight of organic fluid vapor
generated per hour, lb
C = maximum total weight or volume
of fuel burned per hour, lb or cu ft
H = heat of combustion of fuel, BTU/lb
or BTU/cu ft (see A-17)
The sum of the safety valve capacities
marked on the valves shall be equal to
or greater than W.
A = discharge area of safety valve, in2
P = (set pressure x 1.03) + Atmosphere
Pressure, psia
M = molecular weight
T = absolute temperature at inlet, °F + 460
Note
1. Users are warned that a rupture disc will
not burst at its designed pressure if back
pressure builds up in the space between
the disc and the safety valve which will occur should leakage develop in the rupture
disc due to corrosion or other cause.
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designs and specifications without notice.
89
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section I,
Mandatory Appendix A - (1995 Addenda)
Safety Valves for Power Boilers
A93
A-44
The safety valve capacity of each boiler
shall be such that the safety valve or
valves will discharge all the steam that
can be generated by the boiler without allowing the pressure to rise more than 6%
above the maximum allowable working
pressure, or more than 6% above the highest pressure to which any valve is set.
The minimum safety valve or safety relief
valve relieving capacity for other than
electric boilers, waste heat boilers, organic
fluid vaporizers, and forced-flow steam
generators with no fixed steam and waterline, when provided in accordance with
PG-67.4.3, shall be determined on the basis of the pounds of steam generated per
hour per square foot of boiler heating surface and waterwall heating surface, as
given in Table A-44.
The minimum safety valve or safety relief
valve relieving capacity for electric boilers
shall be 31/2 lb/hr/kW input.
In many cases, a greater relieving capacity
of safety valves or safety relief valves will
have to be provided than the minimum
specified in Table A-44, in order to meet the
requirements of the first paragraph of A-44.
A-45
allowable working pressure. The remaining
valves may be set within a range of 3%
above the maximum allowable working
pressure, but the range of setting of all of
the saturated steam valves on a boiler
shall not exceed 10% of the highest pressure to which any saturated steam valve
is set.
When boilers of different maximum allowable working pressures with minimum
safety valve settings varying more than
6% are so connected that steam can flow
toward the lower pressure units, the latter
shall be protected by additional safety
valve capacity, if necessary, on the lower
pressure side of the system. The additional
safety valve capacity shall be based upon
the maximum amount of steam which can
flow into the lower pressure system. The
additional safety valves shall have at least
one valve set at a pressure not to exceed
the lowest allowable pressure and the other valves shall be set within a range not to
exceed 3% above that pressure.
A-46.1 By making an accumulation test,
that is, by shutting off all other steam-discharge outlets from the boiler and forcing
the fires to the maximum. The safety valve
equipment shall be sufficient to prevent an
excess pressure beyond that specified in
PG-67.2. This method should not be used
on a boiler with a superheater or reheater
or on a high-temperature water boiler.
A-46.2 By measuring the maximum
amount of fuel that can be burned and
computing the corresponding evaporative
capacity upon the basis of the heating value of the fuel (see A-12 through A-17).
A93
A-46.3 By determining the maximum
evaporative capacity by measuring the
feedwater. The sum of the safety valve
capacities marked on the valves shall be
equal to or greater than the maximum
evaporative capacity of the boiler. This
method shall not be used on high-temperature water boilers.
A93
A93
A-46
A-48
If the safety valve or safety relief valve
capacity cannot be determined or if it is
desirable to verify the computations, the
capacity may be checked in one of the
three following ways, and if found insufficient, additional capacity shall be provided.
When operating conditions are changed,
or additional heating surface such as water screens or waterwalls is connected to
the boiler circulation, the safety valve or
safety relief valve capacity shall be increased, if necessary, to meet the new
conditions and be in accordance with PG67.2. The additional valves required on
account of changed conditions may be
One or more safety valves on every boiler
shall be set at or below the maximum
Table A-44
Note
When a boiler is fired only by a gas having a
heat value not in excess of 200 BTU/cu ft, the
minimum safety valve or safety relief valve relieving capacity may be based on the values
given for hand-fired boilers above.
Minimum Pounds of Steam Per Hour Per Square Foot of Surface
Firetube Boilers
Watertube Boilers
Boiler heating surface:
Hand fired
5
6
Stoker fired
7
8
Oil, gas or pulverized fuel fired
8
10
Hand fired
8
8
Stoker fired
10
12
Oil, gas, or pulverized fuel fired
14
16
Waterwall heating surface
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designs and specifications without notice.
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Anderson Greenwood Pressure Relief Valves
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ASME Code Section I,
Mandatory Appendix A - (1995 Addenda)
installed on the piping between the boiler
and the main stop valve except when the
boiler is equipped with a superheater or
other piece of apparatus. In the latter case
they may be installed on the piping between the boiler drum and the inlet to the
superheater or other apparatus, provided
that the piping between the boiler and
safety valve (or valves) connection has a
cross-sectional area of at least three times
the combined areas of the inlet connections to the safety valves applied to it.
A-49
No valve of any description shall be place
between the safety valve and the boiler, or
on the discharge pipe between the safety
valve and the atmosphere. When a discharge pipe is used, it shall be not less
than the full size of the valve, and the dis-
charge pipe shall be fitted with an open
drain to prevent water lodging in the upper
part of the safety valve or in the pipe. If a
muffler is used on a safety valve it shall
have sufficient outlet area to prevent back
pressure from interfering with the proper
operation and discharge capacity of the
valve. The muffler plates or other devices
shall be so constructed as to avoid any possibility of restriction of the steam passages
due to deposit. When an elbow is placed on
a safety valve discharge pipe, it shall be located close to the safety valve outlet or the
pipe shall be securely anchored and supported. All safety valve discharges shall be
so located or piped as to be carried clear
from running boards or working platforms
used in controlling the main stop valves of
boilers or steam headers.
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designs and specifications without notice.
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Anderson Greenwood Pressure Relief Valves
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ASME Code Section IV – Heating Boiler Code (1995 Addenda)
Pressure Relieving Devices
HG-400 Pressure Relieving Valve
Requirements
HG-400.1 Safety Valve Requirements
for Steam Boilers
A. Each steam boiler shall have one or
more officially rated safety valves that
are identified with the V or HV Symbol
of the spring pop type adjusted and
sealed to discharge at a pressure not to
exceed 15 psi. Seals shall be attached
in a manner to prevent the valve from
being taken apart without breaking the
seal. The safety valves shall be
arranged so that they cannot be reset
to relieve at a higher pressure than the
maximum allowable working pressure
of the boiler. Drain holes are not required for valves 3/4-inch and smaller,
when the seating surface of the valve is
above the lowest portion of the inside
diameter of the discharge piping. Means
shall be provided for complete drainage
of the discharge piping.
B. No safety valve for a steam boiler shall
be smaller than 1/2-inch. No safety
valve shall be larger than 41/2-inch. The
inlet opening shall have an inside diameter equal to, or greater than, the seat
diameter.
C. The minimum relieving capacity of valve
or valves shall be governed by the capacity marking on the boiler called for in
HG-530.
D. The minimum valve capacity in pounds
per hour shall be the greater of that determined by dividing the maximum BTU
output at the boiler nozzle obtained by
the firing of any fuel for which the unit
is installed by 1000, or shall be determined on the basis of the pounds of
steam generated per hour per square
foot of boiler heating surface as given
in Table HG-400.1. For cast iron boilers
constructed to the requirements of Part
HC, the minimum valve capacity shall
be determined by the maximum output
method. In many cases a greater relieving capacity of valves will have to
be provided than the minimum specified by these rules. In every case, the
requirement of HG-400.1(E) shall be
met.
E. The safety valve capacity for each
steam boiler shall be such that with the
fuel burning equipment installed, and
operated at maximum capacity, the
pressure cannot rise more than 5 psi
above the maximum allowable working
pressure.
F. When operating conditions are
changed, or additional boiler heating
surface is installed, the valve capacity
shall be increased, if necessary, to
meet the new conditions and be in accordance with HG-400.1(E). The
additional valves required, on account
of changed conditions, may be installed
on the outlet piping provided there is no
intervening valve.
HG-400.2 Safety Relief Valve
Requirements for Hot Water Boilers
A. Each hot water heating or supply boiler
shall have at least one officially rated
safety relief valve, of the automatic re-
seating type, identified with the V or HV
Symbol, and set to relieve at or below
the maximum allowable working pressure of the boiler. Safety relief valves
officially rated as to capacity shall have
pop action when tested by steam.
When more than one safety relief valve
is used on either hot water heating or
hot water supply boilers, the additional
valve or valves shall be officially rated
and may have a set pressure within a
range not to exceed 6 psi above the
maximum allowable working pressure
of the boiler up to and including 60 psi,
and 5% for those having a maximum
allowable working pressure exceeding
60 psi. Safety relief valves shall be
spring loaded. Safety relief valves shall
be set and sealed so that they cannot
be reset without breaking the seal.
B. No materials liable to fail due to
deterioration or vulcanization when
subjected to saturated steam temperature corresponding to capacity test
pressure shall be used for any part.
C. No safety relief valve shall be smaller
than 3/4-inch nor larger than 41/2-inch
standard pipe size except that boilers
having a heat input not greater than
15,000 BTU/hr may be equipped with a
rated safety relief valve of 1/2-inch standard pipe size. The inlet opening shall
have an inside diameter approximately
equal to, or greater than, the seat diameter. In no case shall the minimum
opening through any part of the valve
be less than 1/4-inch in diameter or its
equivalent area.
Table HG-400.1
Notes
1. When a boiler is fired only by a gas having
a heat value not in excess of 200 BTU/cu ft,
the minimum safety valve or safety relief
valve relieving capacity may be based on
the values given for hand fired boilers
above.
2. The minimum safety valve or safety relief
valve relieving capacity for electric boilers
shall be 31/2 lb/hr/kW input.
3. For heating surface determination, see
HG-403.
Minimum Pounds of Steam Per Hour Per Square Foot of Heating Surface
Firetube Boilers
Watertube Boilers
Boiler heating surface
Hand fired
5
6
Stoker fired
7
8
Oil, gas or pulverized fuel fired
8
10
Waterwall heating surface
Hand fired
8
8
Stoker fired
10
12
Oil, gas, or pulverized fuel fired
14
16
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Anderson Greenwood Pressure Relief Valves
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ASME Code Section IV – Heating Boiler Code (1995 Addenda)
D. The required steam relieving capacity,
in pounds per hour, of the pressure relieving device or devices on a boiler
shall be the greater of that determined
by dividing the maximum output in BTU
at the boiler nozzle obtained by the firing of any fuel for which the unit is
installed by 1000, or shall be determined on the basis of pounds of steam
generated per hour per square foot of
boiler heating surface as given in Table
HG-400.1. For cast iron boilers constructed to the requirements of Part
HC, the minimum valve capacity shall
be determined by the maximum output
method. In many cases a greater relieving capacity of valves will have to
be provided than the minimum specified by these rules. In every case, the
requirements of HG-400.2(F) shall
be met.
E. When operating conditions are
changed, or additional boiler heating
surface is installed, the valve capacity
shall be increased, if necessary, to
meet the new conditions and shall be in
accordance with HG-400.2(F). The additional valves required, on account of
changed conditions, may be installed
on the outlet piping provided there is no
intervening valve.
F. Safety relief valve capacity for each
boiler with a single safety relief valve
shall be such that, with the fuel burning
equipment installed and operated at
maximum capacity, the pressure cannot
rise more than 10% above the maximum allowable working pressure. When
more than one safety relief valve is
used, the overpressure shall be limited
to 10% above the set pressure of the
highest set valve allowed by HG400.2(A).
HG-400.3 Safety and Safety Relief
Valves for Tanks and Heat Exchangers
A. Steam to Hot Water Supply. When a
hot water supply is heated indirectly by
steam in a coil or pipe within the service limitations set forth in HG-101, the
pressure of the steam used shall not
exceed the safe working pressure of
the hot water tank, and a safety relief
valve at least 1-inch in diameter, set to
relieve at or below the maximum allowable working pressure of the tank, shall
be applied on the tank.
B. High Temperature Water to Water Heat
Exchanger. 1 When high temperature
water is circulated through the coils or
tubes of a heat exchanger to warm water for space heating or hot water
supply, within the service limitations set
forth in HG-101, the heat exchanger
shall be equipped with one or more officially rated safety relief valves that are
identified with the V or HV Symbol, set
to relieve at or below the maximum allowable working pressure of the heat
exchanger, and of sufficient rated capacity to prevent the heat exchanger
pressure from rising more than 10%
above the maximum allowable working
pressure of the vessel.
C. High Temperature Water to Steam Heat
Exchanger.1 When high temperature
water is circulated through the coils or
tubes of a heat exchanger to generate
low pressure steam, within the service
limitations set forth in HG-101, the heat
exchanger shall be equipped with one
or more officially rated safety valves
that are identified with the V or HV
Symbol, set to relieve at a pressure not
to exceed 15 psi, and of sufficient rated
capacity to prevent the heat exchanger
pressure from rising more than 5 psi
above the maximum allowable working
pressure of the vessel. For heat exchangers requiring steam pressures
greater than 15 psi, refer to Section I or
Section VIII, Division 1.
HG-401 Minimum Requirements for
Safety and Safety Relief Valves
HG-401.1 Mechanical Requirements
A. Bottom guided designs are not permitted on hot water valves.
B. Synthetic disk inserts of O-ring or
other types if used shall be compatible
with the maximum design temperature
established for the valve.
C. O-rings or other packing devices when
used on the stems of hot water safety
relief valves shall be so arranged as not
to affect their operation or capacity.
D. The design shall incorporate guiding
arrangements necessary to insure consistent operation and tightness.
Excessive lengths of guiding surfaces
should be avoided.
E. Steam valves shall have a controlled
blowdown of 2 psi to 4 psi and this
blowdown need not be adjustable.
F. The spring shall be designed so that the
full lift spring compression shall be no
grater than 80% of the nominal solid deflection. The permanent set of the spring
(defined as the difference between the
free height and height measured 10 min
after the spring has been compressed
solid three additional times after pre-setting at room temperature) shall not
exceed 0.5% of the free height.
G. There shall be a lifting device and a
mechanical connection between the
lifting device and the disk capable of
lifting the disk from the seat a distance
of at least 1/16-inch with no pressure on
the boiler.
A-92
H. A body drain below seat level shall be
provided by the Manufacturer for all
safety valves and safety relief valves,
except that the body drain may be
omitted when the valve seat is above
the bottom of the inside diameter of the
discharge piping. For valves exceeding
NPS 21/2 the drain hole or holes shall
be tapped not less than NPS 3/8. For
valves NPS 21/2 or smaller, the drain
hole shall not be less than 1/4-inch in
diameter. Body drain connections shall
not be plugged during or after field installation. In hot water relief valves of
the diaphragm type, the space above
the diaphragm shall be vented to prevent a buildup of pressure above the
diaphragm. Hot water relief valves of
the diaphragm type shall be so designed that failure or deterioration of the
diaphragm material will not impair the
ability of the valve to relieve at the rated
capacity.
I. In the design of the body of the valve
consideration shall be given to minimizing the effects of water deposits.
J. Valves shall be provided with wrenching
surfaces to allow for normal installation
without damaging operating parts.
Note
1. Suggested installation practices for the
secondary side of heat exchangers.
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designs and specifications without notice.
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ASME Code Section IV – Heating Boiler Code (1995 Addenda)
K. The set pressure tolerances, plus or minus, of steam safety valves shall not
exceed 2 psi, and for safety relief
valves shall not exceed 3 psi for pressures up to and including 60 psi and
5% for pressures above 60 psi.
HG-401.2 Material Selection
A. Cast iron seats and disks are not permitted.
B. Adjacent sliding surfaces such as
guides and disks shall both be of corrosion resistant material.
C. Springs of corrosion resistant material
or having a corrosion resistant coating
are required.
D. Material for seats and disks should be
such as to provide a reasonable degree
of resistance to steam cutting.
E. Material for valve bodies and bonnets
or their corresponding metallic pressure
containing parts shall be listed in
Section II, except that in cases where a
manufacturer desires to make use of
materials other than those listed in
Section II, he shall establish and maintain specifications requiring equivalent
control of chemical and physical properties and quality.
A-93
HG-401.3 Manufacture and Inspection
A. A Manufacturer shall demonstrate to
the satisfaction of an ASME designee
that his manufacturing, production, and
testing facilities and quality control procedures will insure close agreement
between the performance of random
production samples and the performance of those valves submitted for
capacity certification.
B. Manufacturing, inspection, and test operations including capacity are subject
to inspection at any time by an ASME
designee.
C. A Manufacturer may be granted permission to apply the HV Code Symbol
to production pressure relief valves capacity certified in accordance with
HG-402.3 provided the following tests
are successfully completed. This permission shall expire on the fifth
anniversary of the date it is initially
granted. The permission may be extended for 5 year periods if the
following tests are successfully repeated within the 6 month period before
expiration.
1. Two sample production pressure relief
valves of a size and capacity within the
capability of an ASME accepted laboratory shall be selected by an ASME
designee.
2. Operational and capacity tests shall be
conducted in the presence of an ASME
designee at an ASME accepted laboratory. The valve Manufacturer shall be
notified of the time of the test and may
have representatives present to witness the test.
3. Should the valve fail to relieve at or
above its certified capacity or should it
fail to meet performance requirements
of this Section, the test shall be repeated at the rate of two replacement
valves, selected in accordance with
HG-401.3(C)(1), for each valve that
failed.
4. Failure of any of the replacement
valves to meet the capacity or the performance requirements of this Section
shall be cause for revocation within 60
days of the authorization to use the
Code Symbol on that particular type
of valve. During this period, the
Manufacturer shall demonstrate the
cause of such deficiency and the action
taken to guard against future occurrence, and the requirements of
HG-401.3(C) above shall apply.
C. Testing time on steam valves shall be
sufficient, depending on size and design, to insure that test results are
repeatable and representative of field
performance.
D. Test fixtures and test drums shall be of
adequate size and capacity to assure
representative pop action and accuracy
of blowdown adjustment.
E. A tightness test shall be conducted at
maximum expected operating pressure,
but not at a pressure exceeding the reseating pressure of the valve.
HG-401.5 Design Requirements. At the
time of the submission of valves for capacity certification, or testing in
accordance with this Section, the ASME
Designee has the authority to review the
design for conformity with the requirements of this Section, and to reject or
require modification of designs which do
not conform, prior to capacity testing.
HG-402 Discharge Capacities of
Safety and Safety Relief Valves
HG-402.1 Valve Markings. Each safety or
safety relief valve shall be plainly marked
with the required data by the Manufacturer
in such a way that the markings will not be
obliterated in service. The markings shall
be stamped, etched, impressed, or cast
on the valve or on a nameplate which
shall be securely fastened to the valve.
The markings shall include the following:
A. the name or an acceptable abbreviation of the Manufacturer;
HG-401.4 Manufacturer’s Testing
B. Manufacturer’s design or type number;
A. Every steam valve shall be tested to
demonstrate its popping point, blowdown, and tightness. Every hot water
valve shall be tested to demonstrate its
opening point and tightness. Steam
valves shall be tested on steam or air
and hot water valves on water, steam, or
air. When the blowdown is nonadjustable, the blowdown test may be
performed on a sampling basis.
C. NPS size _____ inch (the nominal pipe
size of the valve inlet);
B. A Manufacturer shall have a well-established program for the application,
calibration, and maintenance of test
gauges.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
94
D. set pressure ________psi;
E. capacity _________lb/hr, or
capacity_________ BTU/hr
in accordance with HG-402.3;
F. year built or, alternatively, a coding may
be marked on the valves such that the
valve Manufacturer can identify the year
the valve was assembled and tested;
G. ASME Symbol as shown in Figure HG402.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section IV – Heating Boiler Code (1995 Addenda)
shall be set at a different pressure.
However, safety valves for steam boilers shall have all nine valves set at 15
psig. A coefficient shall be established
for each test as follows:
KD =
HG-402.3 Determination of Capacity to
Be Stamped on Valves. The Manufacturer
of the valves that are to be stamped with
the Code symbol shall submit valves for
testing to a place where adequate equipment and personnel are available to
conduct pressure and relieving-capacity
tests which shall be made in the presence
of and certified by an authorized observer.
The place, personnel, and authorized observer shall be approved by the Boiler and
Pressure Vessel Committee. The valves
shall be tested in one of the following
three methods.
A. Coefficient Method.1 Tests shall be
made to determine the lift, popping,
and blowdown pressures, and the capacity of at least three valves each of
three representative sizes (a total of
nine valves). Each valve of a given size
=
Coefficient of
discharge
The average coefficient of the tests required shall be taken as the coefficient
K of the design, and the stamped capacity for all sizes and pressures of the
design shall not exceed the value determined from the following formulas:
Figure HG-402
Official Symbol For Stamp to Denote The
American Society of Mechanical
Engineers’ Standard
HG-402.2 Authorization to Use ASME
Stamp. Each safety valve to which the
Code Symbol (Figure HG-402) is to be applied shall be produced by a Manufacturer
and/or Assembler who is in possession of
a valid Certificate of Authorization. (See
HG-540)
Actual steam flow
Theoretical steam flow
For 45 degree seat,
W = (51.45 π DLP x 0.707K ) 0.90
For flat seat,
W = (51.45 π DLPK ) 0.90
For nozzle,
W = (51.45 APK ) 0.90
Where:
W = weight of steam/hr, lb
D
= seat diameter, inch
L
= lift, inch
P
= absolute pressure, psi (accumulated)
KD = coefficient of discharge for a
single test
K
= average coefficient of discharge
A
= nozzle-throat area, in2
the tests. The capacities shall be based
on these four tests as follows.
1. The slope (dW/dP ) of the actual measured relieving capacity versus the flow
pressure for each test point shall be
calculated and averaged:
Slope = dW/dP = measured capacity/
absolute flow pressure (psia)
All values derived from the testing
must fall within ± 5% of the average
value:
Minimum slope = average slope x 0.95
Maximum slope = average slope x 1.05
If slope values derived from the test do
not fall between the minimum and maximum slope values, the authorized
observer shall require that additional
valves be tested at the rate of two for
each value beyond the maximum and
minimum values with a limit of four additional valves.
2. The relieving capacity to be stamped
on the valve shall not exceed 90% of
the average slope times the absolute
flow pressure:
W ≤ average slope [(stamped set
pressure x 1.10) + 14.7] 0.90
B. Slope Method. If a Manufacturer wishes to apply the Code Symbol to a
design of pressure relief valves, four
valves of each combination of pipe and
orifice size shall be tested. These four
valves shall be set at pressures that
cover the approximate range of pressures for which the valve will be used,
or that cover the range available at the
certified test facility that shall conduct
C. Three-Value Method. If a Manufacturer
wishes to apply the Code Symbol to
steam safety valves or safety relief
valves of one or more sizes of a design
set at one pressure, he shall submit
three valves of each size of each design set at one pressure for testing and
the stamped capacity of each size shall
not exceed 90% of the average capacity of the three valves tested.2
side the acceptable limits, as determined by
the new average coefficient, a valve of the
Manufacturer’s choice must be replaced by
two valves of the same size and pressure
as the rejected valve. A new average coefficient, including the replacement valves,
shall be calculated. If any valve, excluding
the two replaced valves, now falls outside
the acceptable limits, the tests shall be considered unsatisfactory.
2. The discharge capacity as determined by
the test of each valve tested shall not vary
by more than ±5% of the average capacity
of the three valves tested. If one of the three
valve tests falls outside of the limits, it may
be replaced by two valves and a new average calculated based on all four valves,
excluding the replaced valve.
Notes
1. The maximum and minimum coefficient determined by the tests of a valve design shall
not vary more than ±5% from the average. If
one or more tests are outside the acceptable limits, one valve of the Manufacturer’s
choice shall be replaced with another valve
of the same size and pressure setting or by
a modification of the original valve.
Following this test a new average coefficient
shall be calculated, excluding the replaced
valve test. If one or more tests are now out-
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
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Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section IV – Heating Boiler Code (1995 Addenda)
HG-402.4 Pressures at Which Capacity
Tests Shall Be Conducted. Safety valves
for steam boilers shall be tested for capacity at 5 psi over the set pressure for which
the valve is set to operate. Capacity certification tests of safety relief valves for hot
water heating and hot water supply boilers
shall be conducted at 110% of the pressure for which the valve is set to operate.
HG-402.5 Opening Tests of PressureTemperature Relief Valves. For the
purpose of determining the set (opening)
pressure, the test medium shall be room
temperature water. The actual set pressure is defined as the pressure at the
valve inlet when the flow rate through the
valve is 40 cm3/min. Capacity tests shall
be conducted with steam (see HG-402.7)
at a pressure 10% above the actual water set pressure. For production capacity
check tests, the rated capacity shall be
based on the actual water set pressure.
HG-402.6 Capacity Tests of PressureTemperature Relief Valves. For the
purpose of determining the capacity of
pressure-temperature relief valves, dummy elements of the same size and shape
as the regularly applied thermal element
shall be substituted and the relieving
capacity shall be based on the pressure
element only. Valves selected to meet the
requirements of production testing, HG401.3, shall have their temperature
elements deactivated by the Manufacturer
prior to or at the time of capacity testing.
HG-402.7 Fluid Medium for Capacity
Tests. The tests shall be made with dry
saturated steam. For test purposes the
limits of 98% minimum quality and 20°F
maximum superheat shall apply. Correction
from within these limits may be made to
the dry saturated condition. The relieving
capacity shall be measured by condensing
the steam or with a calibrated steam
flowmeter.
A. To determine the discharge capacity of
safety relief valves in terms of BTU, the
relieving capacity in pounds for steam
per hour W is multiplied by 1000.
A92
HG-402.8 Where and by Whom
Capacity Tests Shall Be Conducted.
A. Tests shall be conducted at a place
where the testing facilities, methods,
procedures, and person supervising the
tests (Authorized Observer) meet the
applicable requirements of ASME/ANSI
PTC 25.3. The tests shall be made under the supervision of and certified by
an Authorized Observer. The testing facilities, methods, procedures, and
qualifications of the Authorized
Observer shall be subject to the acceptance of ASME on recommendation of
an ASME Designee. Acceptance of the
testing facility is subject to review within
each 5 year period.
2. Valve capacities are published in ‘Pressure
Relief Device Certifications.’ This publication may be obtained from The National
Board of Boiler and Pressure Vessel
Inspectors, 1055 Crupper Avenue,
Columbus, Ohio, 43229.
HG-405 Thermal Elements for
Pressure-Temperature Relief Valves
The thermal elements for pressure-temperature relief valves shall be so designed
and constructed that they will not fail in
any manner which could obstruct flow
passages or reduce capacities of the
valves when the elements are subjected
to steam temperatures.4
HG-512 Safety and Safety Relief
Valve Accumulation Tests
If the safety valve or safety relief valve
capacity cannot be computed or if it is desirable to prove the computations, it may
be checked in any one of the following
ways and, if found insufficient, additional
capacity shall be provided:
B. Capacity test data reports for each
valve model, type, and size, signed by
the Manufacturer and the Authorized
Observer witnessing the tests, shall be
submitted to the ASME Designee for
review and acceptance.1,2
A. by making an accumulation test, that is,
by shutting off all discharge outlets
from the boiler and forcing the fires to
the maximum, the safety valve equipment shall be sufficient to prevent an
excess pressure beyond that specified
in HG-400.1(F) and HG-400.2(F);
HG-402.9 Test Record Data Sheet.
A data sheet for each valve shall be filled
out and signed by the authorized observer
witnessing the test. Such data sheet will
be the manufacturer’s authority to build
and stamp valves of corresponding design
B. by measuring the maximum amount of
fuel that can be burned, and computing
the corresponding evaporative capacity
upon the basis of the heating value of
the fuel. (See B-100, B-101, and B102.)
Notes
1. When changes are made in the design, capacity certification tests shall be repeated.
and construction. When changes are made
in the design of a safety or safety relief
valve in such a manner as to affect the
flow path, lift, or performance characteristics of the valve, new tests in accordance
with this Section shall be performed.3
3. See HG-512 for safety and safety relief
valve accumulation test requirements. See
HG-701 for safety and safety relief valve installation requirements.
4. Since the temperature elements are designed for temperatures up to only 250°F,
they will fail when subjected to steam pressures with corresponding saturation
temperatures in excess of 250°F.
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designs and specifications without notice.
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Anderson Greenwood Pressure Relief Valves
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ASME Code Section IV –
Heating Boiler Code (1995 Addenda)
Installation Requirements
A92
HG-700 Installation Requirements,
All boilers
HG-701.6 Safety and Safety Relief
Valve Discharge Piping
A. A discharge pipe shall be used. Its internal cross-sectional area shall be not
less than the full area of the valve outlet or of the total of the valve outlets
discharging thereinto and shall be as
short and straight as possible and so
arranged as to avoid undue stress on
the valve or valves. A union may be installed in the discharge piping close to
the valve outlet. When an elbow is
placed on a safety or safety relief valve
discharge pipe, it shall be located close
to the valve outlet downstream of the
union.
HG-701 Mounting Safety and
Safety Relief Valves
HG-701.1 Permissible Mounting. Safety
valves and safety relief valves shall be located in the top or side1 of the boiler. They
shall be connected directly to a tapped or
flanged opening in the boiler, to a fitting
connected to the boiler by a short nipple,
to a Y-base, or to a valveless header connecting steam or water outlets on the
same boiler. Coil or header type boilers
shall have the safety valve or safety relief
valve located on the steam or hot water
outlet end. Safety valves and safety relief
valves shall be installed with their spindles
vertical. The opening or connection between the boiler and any safety valve or
safety relief valve shall have at least the
area of the valve inlet.
HG-701.2 Requirements for Common
Connections for Two or More Valves
A. When a boiler is fitted with two or more
safety valves on one connection, this
connection shall have a cross-sectional
area not less than the combined areas
of inlet connections of all the safety
valves with which it connects.
B. When a Y-base is used, the inlet area
shall be not less than the combined
outlet areas. When the size of the boiler requires a safety valve or safety
relief valve larger than 41/2-inch in diameter, two or more valves having the
required combined capacity shall be
used. When two or more valves are
used on a boiler, they may be single,
directly attached, or mounted on a
Y-base.
HG-701.3 Threaded Connections. A
threaded connection may be used for attaching a valve.
B. The discharge from safety or safety relief valves shall be so arranged that
there will be no danger of scalding attendants. The safety or safety relief
valve discharge shall be piped away
from the boiler to the point of discharge, and there shall be provisions
made for properly draining the piping.
The size and arrangement of discharge
piping shall be independent of other
discharge piping and shall be such that
any pressure that may exist or develop
will not reduce the relieving capacity of
the relieving devices below that required to protect the boiler.
Note
1. The top or side of the boiler shall mean the
highest practicable part of the boiler proper
but in no case shall the safety valve be located below the normal operating level and in
no case shall the safety relief valve be located below the water level.
HG-701.4 Prohibited Mountings. Safety
and safety relief valves shall not be connected to an internal pipe in the boiler.
HG-701.5 Use of Shutoff Valves
Prohibited. No shutoff of any description
shall be place between the safety or
safety relief valve and the boiler, or on
discharge pipes between such valves and
the atmosphere.
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designs and specifications without notice.
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Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section VIII – Division I (1995 Addenda)
Pressure Relief Devices
UG-125 General
A. All vessels within the Scope of this
Division, irrespective of size or pressure, shall be provided1 with protective
devices in accordance with the requirements of UG-125 through UG-136.
Unless otherwise defined in this
Division, the definitions relating to pressure relief devices in Appendix I of
ASME/ANSI PTC 25.3 Safety and
Relief Valves shall apply.
B. An unfired steam boiler, as defined in
U-1(G), shall be equipped with pressure relief devices required by Section I
insofar as they are applicable to the
service of the particular installation.
C. All pressure vessels other than unfired
steam boilers shall be protected by a
pressure relieving device that shall prevent the pressure from rising more than
10% or 3 psi, whichever is greater,
above the maximum allowable working
pressure except as permitted in (1) and
(2) below. (See UG-134 for pressure
settings.)
1. When multiple pressure relieving devices
are provided and set in accordance with
UG-134(A), they shall prevent the pressure from rising more than 16% or 4 psi,
whichever is greater, above the maximum allowable working pressure.
2. Where an additional hazard can be
created by exposure of a pressure vessel to fire or other unexpected sources
of external heat, supplemental pressure relieving devices shall be installed
to protect against excessive pressure.
Such supplemental pressure relieving
devices shall be capable of preventing
the pressure from rising more than
21% above the maximum allowable
working pressure. The same pressure
relieving devices may be used to satisfy
the capacity requirements of (C) or
(C)(1) above and this paragraph provided the pressure setting requirements of
UG-134(A) are met.
3. Pressure relief devices, intended primarily for protection against exposure of a
pressure vessel to fire or other unexpected sources of external heat installed
on vessels having no permanent supply
connection and used for storage at ambient temperatures of nonrefrigerated
liquefied compressed gases,2 are excluded from the requirements of (C)(1)
and (C)(2) above, provided:
(a) the relief devices are capable of preventing the pressure from rising more
than 20% above the maximum allowable
working pressure of the vessels;
(b) the set pressure of these devices
shall not exceed the maximum allowable
pressure of the vessels;
(c) the vessels have sufficient ullage to
avoid a liquid full condition;
(d)the maximum allowable working pressure of the vessels on which these
devices are installed is greater than the
vapor pressure of the stored liquefied
compressed gas at the maximum anticipated temperature3 that the gas will
reach under atmospheric conditions; and
(e) pressure relief valves used to satisfy
these provisions also comply with the requirements of UG-129(A)(5),
UG-131(C)(2), and UG-134(D)(2).
D. Pressure relieving devices shall be constructed, located, and installed so that
they are readily accessible for inspection and repair and so that they cannot
be readily rendered inoperative (see
Appendix M), and should be selected
on the basis of their intended service.
E. Pressure relief valves or nonreclosing
pressure relief devices4 may be used
as protective devices. Nonreclosing
pressure relief devices may be used
either alone or, if applicable, in combination with safety or safety relief valves
on vessels.5
F. Vessels that are to operate completely
filled with liquid shall be equipped with
liquid relief valves, unless otherwise
protected against overpressure.
G. The protective devices required in (A)
above need not be installed directly on
a pressure vessel when the source of
pressure is external to the vessel and
is under such positive control that the
pressure in the vessel cannot exceed
the maximum allowable working pressure at the operating temperature except
as permitted in (C) above (see UG-98).6
H. Safety and safety relief valves for
steam service shall meet the requirements of UG-131(B).
UG-126 Pressure Relief Valves 7
A. Safety, safety relief, and relief valves
shall be of the direct spring loaded type.
Notes
1. Safety devices need not be provided by the
vessel manufacturer, but overpressure protection shall be provided prior to placing the
vessel in service.
2. For the purpose of these rules, gases are
considered to be substances having a vapor
pressure greater than 40 psia at 100°F.
3. Normally this temperature should not be
less than 115°F.
4. A pressure relief valve is a pressure relief
device which is designed to reclose and
prevent the further flow of fluid after normal
conditions have been restored. A nonreclosing pressure relief device is a pressure relief
device designed to remain open after
operation.
5. Use of nonreclosing devices of some types
may be advisable on vessels containing
substances that may render a safety or
safety relief valve inoperative, where a loss
of valuable material by leakage should be
avoided, or where contamination of the atmosphere by leakage of noxious fluids must
be avoided. The use of rupture disc devices
may also be advisable when very rapid
rates of pressure rise may be encountered.
6. Pressure reducing valves and similar mechanical or electrical control instruments,
except for pilot operated valves as permitted in UG-126(B), are not considered as
sufficiently positive in action to prevent excess pressures from being developed.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
98
7. A safety valve is a pressure relief valve
actuated by inlet static pressure and characterized by rapid opening or pop action. A
relief valve is a pressure relief valve actuated by inlet static pressure which opens in
proportion to the increase in pressure over
the opening pressure. A safety relief valve is
a pressure relief valve characterized by
rapid opening or pop action, or by opening
in proportion to the increase in pressure
over the opening pressure, depending on
application. A pilot operated pressure relief
valve is a pressure relief valve in which the
major relieving device is combined with and
is controlled by a self-actuated auxiliary
pressure relief valve.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section VIII – Division I (1995 Addenda)
B. Pilot operated pressure relief valves
may be used, provided that the pilot is
self-actuated and the main valve will
open automatically at not over the set
pressure and will discharge its full rated
capacity if some essential part of the
pilot should fail.
C. The spring in a safety valve or safety
relief valve shall not be set for any
pressure more than 5% above or below
that for which the valve is marked, unless the setting is within the spring
design range established by the valve
manufacturer or is determined to be acceptable to the manufacturer. The initial
adjustment shall be performed by the
manufacturer, his authorized representative, or an assembler, and a valve
data tag shall be provided that identifies
the set pressure capacity and date. The
valve shall be sealed with a seal identifying the manufacturer, his authorized
representative, or the assembler performing the adjustment.
D. The set pressure tolerance, plus or minus, of pressure relief valves shall not
exceed 2 psi for pressures up to and including 70 psi and 3% for pressures
above 70 psi.
UG-127 Nonreclosing Pressure
Relief Devices
A. Rupture Disk Devices 8
1. General
(a) Every rupture disk shall have stamped
burst pressure established by rules of
(A)(1)(b) below with a manufacturing
design range9 at a specified disk temperature10 and shall be marked with a
lot number. The burst pressure tolerance
at the specific disk temperature shall not
exceed ±2 psi for stamped burst pressure up to and including 40 psi and ±5%
for stamped burst pressure above 40
psi.
(b) The stamped bursting pressure within the manufacturing design range at the
coincident disk temperature shall be derived by one of the following methods.
All the tests of disks for a given lot shall
be made in a holder of the same form
and dimensions as that with which the
disk is to be used.
(1) At least two sample rupture disks
from each lot of rupture disks, made
from the same materials and of the
same size as those to be used, shall be
burst to verify that the stamped bursting
pressure falls within the manufacturing
design range at the coincident disk temperature. At least one disk shall be
burst at room temperature. The
stamped rating at specified disk temperature shall be the average of the bursts
at coincident disk temperature.
(2) At least four sample rupture disks,
but not less than 5%, from each lot of
rupture disks, made from the same material and of the same size as those to
be used, shall be burst at four different
temperatures, distributed over the applicable temperature range for which
the disk will be used. These data shall
be used to establish a curve of bursting
pressure versus temperature for the lot
of disks. The stamped rating at the coincident disk temperature shall be
interpolated from this curve.
(3) For prebulged, solid metal disks or
graphite disks only, a curve of percentage
ratio at temperatures other than ambient
may be establish as in (2) above, using
one size of disk for each lot of material.
At least four bursts at four different temperatures shall be used to establish the
above curve over the applicable temperature range. At least two disks from each
lot of disks, made from this lot of material
and of the same size as those to be
used, shall be burst at ambient temperature to establish the room temperature
rating of the lot of disks.
The percent change of bursting pressure taken from the above curve shall
be used to establish the stamped rating
at the coincident disk temperature for
the lot of disks.
2. Capacity Rating
(a) The calculated capacity rating of a
rupture disk device shall not exceed a
value based on the applicable theoretical
formula (UG-131) for the various media
multiplied by K = coefficient = 0.62. The
area A (square inches) in the theoretical
formula shall be the minimum net area
existing after disk burst.11,12
(b) In lieu of the method of capacity rating in (a) above, a Manufacturer may
have the capacity of a given rupture disk
Notes
8. A rupture disc device is a nonreclosing
pressure relief device actuated by inlet static pressure and designed to function by the
bursting of a pressure containing disc. A
rupture disc is the pressure containing and
pressure sensitive element of a rupture disc
device. A rupture disc holder is the structure
which encloses and clamps the rupture disc
in position. Rupture discs may be designed
in several configurations, such as plain flat,
prebulged or reverse buckling, and may be
made of either ductile or brittle material;
rupture disc material is not required to conform to an ASME specification. The material
of the rupture disc holder shall be listed in
Section II and be permitted for use in this
Division.
9. The manufacturing design range is a range
of pressure within which the average burst
pressure of test discs must fall to be acceptable for a particular requirement as agreed
upon between the rupture disc Manufacturer
and the user or his agent. The disc shall be
marked at the average burst pressure of all
test discs.
10. The specified disc temperature supplied to
the rupture disc Manufacturer shall be the
temperature of the disc when the disc is expected to burst.
11. The minimum net flow area is the calculated
net area after a complete burst of the disc
with appropriate allowance for any structural
members which may reduce the net flow
area through the rupture disc device. The
net flow area for sizing purposes shall not
exceed the nominal pipe size area of the
rupture disc device.
12. When rupture disc devices are used, it is
recommended that the design pressure of
the vessel be sufficiently above the intended operating pressure to provide sufficient
margin between operating pressure and
rupture disc due to fatigue or creep.
Application of rupture disc devices to liquid
service should be carefully evaluated to assure that the design of the rupture disc
device and the dynamic energy of the system on which it is installed will result in
sufficient opening of the rupture disc.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
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device design determined for the KD
coefficient in general accordance with
the procedures of UG-131, as applicable.
3. Application of Rupture Disks
(a) A rupture disk device may be used as
the sole pressure relieving device on a vessel.
(b) A rupture disk device may be installed
between a pressure relief valve13 and the
vessel provided:
(1) the combination of the spring loaded
safety or safety relief valve and the rupture disk device is ample in capacity to
meet the requirements of UG-133(A)
and (B);
(2) the stamped capacity of a spring
loaded safety or safety relief valve (nozzle type) when installed with a rupture
disk device between the inlet of the
valve and the vessel shall be multiplied
by a factor of 0.90 of the rated relieving
capacity of the valve alone, or alternatively, the capacity of such a
combination shall be established in accordance with (3) below;
(3) the capacity of the combination of
the rupture disk device and the spring
loaded safety or safety relief valve may
be established in accordance with the
appropriate paragraphs of UG-132,
Certification of Capacity of Safety and
Safety Relief Valves in Combination with
nonreclosing Pressure Relief Devices;
(4) the space between a rupture disk device and a safety or safety relief valve
shall be provided with a pressure gauge,
a try cock, free vent, or suitable telltale
indicator. This arrangement permits detection of disk rupture or leakage.14
(5) the opening12 provided through the
rupture disk, after burst, is sufficient to
permit a flow equal to the capacity of the
valve [(2) and (3) above], and there is no
chance of interference with proper functioning of the valve; but in no case shall
this area be less than the area of the inlet of the valve unless the capacity and
functioning of the specific combination of
rupture disk and valve have been established by test in accordance with UG-132.
(c) A rupture disk device may be installed
on the outlet side15 of a spring loaded
safety relief valve which is opened by direct action of the pressure in the vessel
provided:
(1) the valve is so designed that it will not
fail to open at its proper pressure setting
regardless of any back pressure that can
accumulate between the valve disk and
the rupture disk. The space between the
value disk and the rupture disk shall be
vented or drained to prevent accumulation of pressure due to a small amount of
leakage from the valve.16
stamped bursting pressure of the rupture disk at the coincident operating
temperature plus any pressure in the
outlet piping exceed the maximum allowable working pressure of the vessel
or the set pressure of the safety or safety relief valve.
(4) the opening provided through the
rupture disk device after breakage is
sufficient to permit a flow equal to the
rated capacity of the attached safety or
safety relief valve without exceeding the
allowable overpressure;
(5) any piping beyond the rupture disk
cannot be obstructed by the rupture disk
or fragment;
(6) the contents of the vessel are clean
fluids, free from gumming or clogging
matter, so that accumulation in the
space between the valve inlet and the
rupture disk (or in any other outlet that
may be provided) will not clog the outlet;
(7) the bonnet of the safety relief valve
shall be vented to prevent accumulation
of pressure.
B. Breaking Pin Device 17
(2) the valve is ample in capacity to
meet the requirements of UG-133(A)
and (B);
1. Breaking pin devices shall not be used
as single devices but only in combination between the safety or safety relief
valve and the vessel.
(3) the stamped bursting pressure of the
rupture disk at the coincident disk temperature plus any pressure in the outlet
piping shall not exceed the design pressure of the outlet portion of the safety or
safety relief valve and any pipe or fitting
between the valve and the rupture disk
device. However, in no case shall the
2. The space between a breaking pin device and a safety or safety relief valve
shall be provided with a pressure
gauge, a try cock, a free vent, or suitable telltale indicator. This arrangement
permits detection of breaking pin device
operation or leakage.
Notes
13. Use of a rupture disc device in combination
with a safety relief valve shall be carefully
evaluated to ensure that the media being
handled and the valve operational characteristics will result in pop action of the valve
coincident with the bursting of the rupture
disc.
14. Users are warned that a rupture disc will not
burst at its design pressure if back pressure
builds up in the space between the disc and
the safety or safety relief valve which will
occur should leakage develop in the rupture
disc due to corrosion or other cause.
15. This use of a rupture disc device in series
with the safety or safety relief valve is per-
mitted to minimize the loss by leakage
through the valve of valuable or of noxious
or otherwise hazardous materials, and
where a rupture disc alone or disc located
on the inlet side of the valve is impracticable, or to prevent corrosive gases from a
common discharge line from reaching the
valve internals.
16. Users are warned that an ordinary spring
loaded safety relief valve will not open at its
set pressure if back pressure builds up in
the space between the valve and rupture
disc. A specially designed valve is required,
such as a diaphragm valve or a valve
equipped with a bellows above the disc.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
100
17. A breaking pin device is a nonreclosing
pressure relief device actuated by inlet static pressure and designed to function by the
breakage of a load-carrying section of a pin
which supports a pressure containing member. A breaking pin is the load-carrying
element of a breaking pin device. A breaking
pin housing is the structure which encloses
the breaking pin mechanism. The material
of the housing shall be listed in Section II
and be permitted for use in this Division.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section VIII – Division I (1995 Addenda)
2. Manufacturer’s design or type number;
3. Each breaking pin device shall have a
rated pressure and temperature at
which the pin will break. The breaking
pin shall be identified to a lot number
and shall be guaranteed by the
Manufacturer to break when the rated
pressure, within the following tolerances, is applied to the device:
Rated Pressure, psi
Minimum Maximum
Tolerance, Plus
or Minus, psi
30
150
5
151
275
10
276
375
15
4. The rated pressure of the breaking pin
plus the tolerance in psi shall not exceed 105% of the maximum allowable
working pressure of the vessel to which
it is applied.
5. The rated pressure at the coincident
operating temperature18 shall be verified by breaking two or more sample
breaking pins from each lot of the same
material and the same size as those to
be used. The lot size shall not exceed
25. The test shall be made in a device
of the same form and pressure dimensions as that in which the breaking pin
is to be used.
C. Spring Loaded Nonreclosing
Pressure Relief Device
1. A spring loaded nonreclosing pressure
relief device, pressure actuated by
means which permit the spring loaded
portion of the device to open at the
specified set pressure and remain open
until manually reset, may be used provided the design of the spring loaded
nonreclosing device will achieve full
opening at or below its set pressure.
Such a device may not be used in combination with any other pressure relief
device. The tolerance on opening point
shall not exceed ±5%.
3. NPS size _______ (the nominal pipe
size of the valve inlet);
4. set pressure ________ psi;
5. certified capacity (as applicable);
Figure UG-129 Official Symbol for Stamp
to denote the American Society of
Mechanical Engineers’ Standard
2. The calculated capacity rating of a spring
loaded nonreclosing pressure relief device shall not exceed a value based on
the applicable theoretical formula (see
UG-131) for the various media, multiplied
by: K = coefficient = 0.62.
The area A (square inches) in the theoretical formula shall be the flow area
through the minimum opening of the
nonreclosing pressure relief device.
3. In lieu of the method of capacity rating
(2) above, a Manufacturer may have
the capacity of a spring loaded nonreclosing pressure relief device design
certified in general accordance with the
procedures of UG-131, as applicable.
UG-128 Liquid Relief Valve
Any liquid relief valve used shall be at
least NPS 1/2.
UG-129 Marking
A. Safety, Safety Relief, Liquid Relief, and
Pilot Operated Pressure Relief Valves.
Each safety, safety relief, liquid relief
and pilot operated valve NPS 1/2 and
larger shall be plainly marked by the
manufacturer or assembler with the required data in such a way that the
marking may be placed on the valve or
on a plate or plates that satisfy the requirements of UG-119:
1. the name, or an acceptable abbreviation,
of Manufacturer and the Assembler;
(a) lb/hr of saturated steam at an overpressure of 10% or 3 psi, whichever is
greater for valves certified on steam
complying with UG-131(B); or
(b) gal/min of water at 70°F at an overpressure of 10% or 3 psi, whichever is
greater for valves certified on water; or
(c) SCFM (standard cubic feet per
minute at 60°F and 14.7 psia), or lb/min,
of air at an overpressure of 10% or 3
psi, whichever is greater. Valves that are
capacity certified in accordance with
UG-131(C)(2) shall be marked ‘at 20%
overpressure.’
(d) In addition to one of the fluids specified above, the Manufacturer may
indicate the capacity in other fluids (see
Appendix 11).
6. year built, or alternatively, a coding may
be marked on the valve such that the
valve Manufacturer or Assembler can
identify the year the valve was assembled or tested;
7. ASME Symbol as shown in Fig. UG129. The pilot of a pilot operated
pressure relief valve shall be plainly
marked by the Manufacturer or
Assembler showing the name of the
Manufacturer; the Manufacturer’s design or the type number, the set
pressure in pounds per square inch,
and the year built, or alternately a coding that the Manufacturer can use to
identify the year built.
On valves smaller than NPS 1/2, the
markings may be made on a metal tag attached by wire or adhesive meeting the
requirements of UG-119 or other means
suitable for the service conditions.
Notes
18. The specified temperature supplied to the
breaking pin manufacturer shall be the temperature of the breaking pin when an
emergency condition exists and the pin is
expected to break.
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designs and specifications without notice.
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ASME Code Section VIII – Division I (1995 Addenda)
B. Safety and safety relief valves certified
for a steam discharging capacity under
the provisions of Section I and bearing
the official Code Symbol Stamp of
Section I for safety valves may be used
on pressure vessels. The rated capacity in term of other fluids shall be
determined by the method of conversion given in Appendix 11. [See
UG-131(H).]
C. Pressure Relief Valves in Combination
With Rupture Disk Devices. Pressure
relief valves in combination with rupture
disk devices shall be marked with the
capacity as established in accordance
with UG-127(A)(3)(b)(2) (using 0.90 factor) or the combination capacity factor
established by test in accordance with
UG-132(A) or (B), in addition to the
marking of UG-129(A) and (F) below.
The marking may be placed on the
valve or rupture disk device or on a
plate or plates that satisfy the requirements of UG-119 or rupture disk device.
The marking shall include the following:
1. name of Manufacturer of valve;
2. design or type number of valve;
3. name of Manufacturer of rupture disk
device;
4. design or type number of rupture disk
device;
5. capacity or combination capacity
factor;
6. name of organization responsible for
this marking. This shall be either the
vessel user, vessel Manufacturer,
rupture disk Manufacturer, or pressure relief valve Manufacturer.
D. Pressure Relief Valves in Combination
With Breaking Pin Devices. Pressure
relief valves in combination with breaking pin devices shall be marked in
accordance with (A) above. In addition,
the rated pressure shall be marked on
the breaking pin and the breaking pin
housing.
E. Rupture Disk Devices. Every rupture
disk shall be plainly marked by the
Manufacturer in such a way that the
marking will not be obliterated in service. The rupture disk marking may be
placed on the flange of the disk or on a
metal tab that satisfies the requirements of UG-119. The marking shall
include the following:
1. the name or identifying trademark of
the Manufacturer;
2. Manufacturer’s design or type
number;
3. lot number;
4. disk material;
5. size ________ (NPS designator
at valve inlet);
6. stamped bursting pressure _____
psi;
7. coincident disk temperature _____°F;
8. capacity _______ lb of saturated
steam/hr, or _______ cu ft of air/min
(60°F and 14.7 psia).19
Items (1), (2), and (5) above shall also be
marked on the rupture disk holder.
F. Spring Loaded nonreclosing Pressure
Relief Devices. Spring loaded
nonreclosing pressure relief devices
shall be marked in accordance with (A)
above except that the Code Symbol
Stamp is to be applied only when the
capacity has been established and certified in accordance with UG-127(C)(3)
and all other requirements of UG-130
have been met.
UG-130 Use of Code Symbol Stamp
Each pressure relief valve 20 to which the
Code Symbol (see Fig. UG-129) will be
applied shall have been fabricated or assembled by a Manufacturer or Assembler
holding a valid Certificate of Authorization
(UG-117) and capacity certified in accordance with the requirements of this
Division.
Notes
19. In addition, the Manufacturer may indicate
the capacity in other fluids (see Appendix
11).
20. Vacuum relief valves are not covered by
Code Symbol Stamp requirements.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
102
UG-131 Certification of Capacity of
Pressure Relief Valves
A. Before the Code Symbol is applied
to any pressure relief valve, the valve
Manufacturer shall have the capacity of
his valves certified in accordance with
provisions of this paragraph.
B. 1. Capacity certification tests for pressure relief valves for compressible
fluids shall be conducted on dry saturated steam, or air, or natural gas.
When dry saturated steam is used, the
limits for test purposes shall be 98%
minimum quality and 20°F maximum
superheat. Correction from within these
limits may be made to the dry saturated
condition. Valves for steam service may
be rated as above, but at least one
valve of each series shall be tested on
steam to demonstrate the steam capacity and performance.
2. Capacity certification tests for pressure relief valves for incompressible
fluids shall be conducted on water at a
temperature between 40°F and 125°F.
C. 1. Capacity certification tests shall be
conducted at a pressure which does
not exceed the pressure for which the
pressure relief valve is set to operate
by more than 10% or 3 psi, whichever
is greater, except as provided in (C)(2)
below. Minimum pressure for capacity
certification tests shall be at least 3 psi
above set pressure. The reseating
pressure shall be noted and recorded.
2. Capacity certification tests of pressure relief valves for use in accordance
with UG-125(C)(3) may be conducted
at a pressure not to exceed 120% of
the stamped set pressure of the valve.
3. (a) Pressure relief valves for compressible fluids having an adjustable
blowdown construction shall be adjusted
prior to testing so that the blowdown
does not exceed 5% of the set pressure
or 3 psi, whichever is greater.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section VIII – Division I (1995 Addenda)
(b) The blowdown of pressure relief
valves for incompressible fluids and
pressure relief valves for compressible
fluids having nonadjustable blowdown
shall be noted and recorded.
4. Capacity certification of pilot operated pressure relief valves may be based
on tests without the pilot valve installed,
provided prior to capacity tests it has
been demonstrated by test to the satisfaction of the Authorized Observer that
the pilot valve will cause the main valve
to open fully at a pressure which does
not exceed the set pressure by more
than 10% or 3 psi, whichever is greater,
and that the pilot valve in combination
with the main valve will meet all the requirements of this Division.
D. 1. A capacity certification test is required on a set of three valves for each
combination of size, design, and pressure setting. The stamped capacity
rating for each combination of design,
size, and test pressure shall not exceed 90% of the average capacity of
the three valves tested. The capacity
for each set of three valves shall fall
within a range of ±5% of the average
capacity. Failure to meet this requirement shall be cause to refuse certification
of that particular safety valve design.
2. If a Manufacturer wishes to apply the
Code Symbol to a design of pressure
relief valves, four valves of each combination of pipe size and orifice size shall
be tested. These four valves shall be
set at pressures which cover the approximate range of pressures for which
the valve will be used or covering the
range available at the certified test facility that shall conduct the tests. The
capacities based on these four tests
shall be as follows:
(a) For compressible fluids, the slope
W/P of the actual measured capacity
versus the flow pressure for each test
point shall be calculated and averaged:
W
measured capacity
slope = ––– = ––––––––––––––––––––––
P
absolute flow pressure, psia
All values derived from the testing must
fall within ±5% of the average value:
minimum slope = 0.95 x average slope
maximum slope = 1.05 x average slope
If the values derived from the testing
do not fall between the minimum and
maximum slope values, the Authorized
Observer shall require that additional
valves be tested at the rate of two for
each valve beyond the maximum and
minimum values with a limit of four additional valves.
The relieving capacity to be stamped
on the valve shall not exceed 90% of
the average slope times the absolute
accumulation pressure:
rated slope = 0.90 x average slope
stamped capacity ≤ rated slope (1.10 x
set pressure + 14.7)
or (set pressure + 3 psi + 14.7),
whichever is greater
For valves certified in accordance with
(C)(2) above,
stamped capacity ≤ rated slope (1.20 x
set pressure + 14.7)
or (set pressure + 3 psi + 14.7),
whichever is greater
nus discharge pressure) test pressure
and a straight line drawn through these
four points. If the four points do not establish a straight line, two additional
valves shall be tested for each unsatisfactory point, with a limit of two
unsatisfactory points. Any point that departs from the straight line by more than
5% should be considered an unsatisfactory point. The relieving capacity
shall be determined from this line. The
certified capacity shall not exceed 90%
of the capacity taken from the line.
E. Instead of individual capacity certification as provided in (D) above, a
coefficient of discharge K may be
established for specific safety valve
design according to the following
procedure.
1. For each design, the pressure relief
valve manufacturer shall submit for test
at least three valves for each of three
different sizes (a total of nine valves) together with detailed drawings showing
the valve construction. Each valve of a
given size shall be set at a different
pressure.
2. Tests shall be made on each pressure or relief valve to determine its
capacity-lift, popping and blowdown
pressures, and actual capacity in terms
of the fluid used in the test. A coefficient
KD shall be established for each test run
as follows:
KD =
Actual flow
Theoretical flow
coefficient
= of discharge
(b) For incompressible fluids, the capacities shall be plotted on log-log
paper against the differential (inlet mi-
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designs and specifications without notice.
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ASME Code Section VIII – Division I (1995 Addenda)
where actual flow is determined quantitatively by test, and theoretical flow is
calculated by the appropriate formula
which follows:
For tests with dry saturated steam,21
WT = 51.5 AP
For tests with air,
WT = 356 AP
–––––
M
–––
T
√
For tests with natural gas,
–––––
M
WT = CAP
–––
ZT
√
For tests with water,
–––––––––
WT = 2407A √ (P-Pd)w
where:
WT = theoretical flow, lb/hr
A = actual discharge area through
the valve at developed lift, in2
P = (set pressure x 1.10) plus
atmosphere, psia, or set pressure plus atmospheric pressure
plus 3 psi, whichever is greater
Pd = pressure at discharge from
valve, psia
M = molecular weight
T = absolute temperature at inlet,
°F + 460°F
C = constant for gas or vapor based
on the ratio of specific heats
k = Cp /Cv (see Fig.11-1, pg.99)
Z = compressibility factor corresponding to P and T
w = specific weight of water at valve
inlet conditions
The average of the coefficients KD of
the nine tests required shall be multiplied by 0.90, and this product shall be
taken as the coefficient K of that design. The coefficient of the design shall
not be greater than 0.878 (the product
of 0.9 x 0.975).22
To convert lb/hr of water to gal/min of
water, multiply the capacity in lb/hr by
1/500.
3. The official relieving capacity of all
sizes and pressures of given design, for
which K has been established under
the provisions of (E)(2) above, that are
manufactured subsequently shall not
exceed the value calculated by the appropriate formula in (E)(2) above
multiplied by the coefficient K (see
Appendix 11).
4. The coefficient shall not be applied to
valves whose beta ratio (ratio of valve
throat to inlet diameter) lies outside the
range of 0.15 to 0.75, unless tests have
demonstrated that the individual coefficient of discharge KD for valves at the
extreme ends of a larger range is within
±5% of the average coefficient K. For
designs where the lift is used to determine the flow area, all valves shall have
the same nominal lift-to-seat diameter
ratio (L/D).
F. Tests shall be conducted at a place
where the testing facilities, methods,
procedures, and person supervising
the tests (Authorized Observer) meet
the applicable requirements of
ASME/ANSI PTC 25.3. The tests shall
be made under the supervision of and
certified by an Authorized Observer.
The testing facilities, methods, procedures, and qualifications of the
Authorized Observer shall be subject to
the acceptance of the ASME on recommendation of an ASME Designee.
Acceptance of the testing facility is subject to review within each 5 year period.
review and acceptance.23 Where
changes are made in the design, capacity certification tests shall be
repeated.
H. For absolute pressures up to 1500
psia, it is permissible to rate safety
valves under PG-69.1.2 of Section I
with capacity ratings at a flow pressure
of 103% of the set pressure, for use on
pressure vessels, without further test.
In such instances, the capacity rating of
the valve may be increased to allow for
the flow pressure permitted in (C)(1)
and (C)(3) above, namely, 110% of the
set pressure, by the multiplier:
1.10p + 14.7
1.03p + 14.7
where:
p = set pressure, psi
Such valves shall be marked in accordance with UG-129. This multiplier shall
not be used as a divisor to transform
test ratings from a higher to a lower
flow.
For steam pressures above 1500 psi,
the above multiplier is not acceptable.
For steam valves with relieving pressures between 1500 psi and 3200 psi,
the capacity shall be determined by using the equation for steam and the
correction factor for high pressure
steam in (E)(2) above with the permitted absolute relieving pressure (1.10p +
14.7) and the coefficient K for that valve
design.
I. Rating of nozzle type pressure relief
valves, i.e., coefficient KD, greater than
0.90 and nozzle construction, for saturated water shall be according to 11-2.
G. Capacity test data reports for each
valve model, type, and size, signed by
the manufacturer and the Authorized
Observer witnessing the tests shall be
submitted to the ASME Designee for
J. When changes are made in the design
of a pressure relief valve in such a manner as to affect the flow path, lift, or
performance characteristics of the
valve, new tests in accordance with this
Division shall be performed.
22. All experimentally determined coefficients
KD shall fall within a range of ±5% of the
average KD found. Failure to meet this
requirement shall be cause to refuse certification of that particular valve design.
23. Valve capacities are published in ‘Pressure
Relief Device Certification.’ This publication
may be obtained from the National Board of
Boiler and Pressure Vessel Inspectors, 1055
Crupper Avenue, Columbus, Ohio 43229.
Notes
21. For dry saturated steam pressures over
1500 psig and up to 3200 psig, the
value of WT, calculated by the above equation, shall be corrected by being multiplied
by the following factors:
(
)
0.1906P –1000
0.2292P –1061
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designs and specifications without notice.
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UG-132 Certification of Capacity of
Safety Relief Valves in Combination
with Nonreclosing Pressure Relief
Devices
A. Capacity of Safety or Safety Relief
Valves in Combination With a Rupture
Disk Device at the Inlet
1. For each combination of safety or
safety relief valve design and rupture
disk device design, the safety valve
manufacturer or the rupture disk device
manufacturer may have the capacity of
the combination certified as prescribed
in (3) and (4) below.
2. Capacity certification tests shall be
conducted on saturated steam, air or
natural gas. When saturated steam is
used, corrections for moisture content
of the steam shall be made.
3. The valve manufacturer or the rupture disk device manufacturer may
submit for tests the smallest rupture
disk device size with the equivalent size
of safety or safety relief valve that is intended to be used as a combination
device. The safety or safety relief valve
to be tested shall have the largest orifice used in the particular inlet size.
4. Tests may be performed in accordance with the following subparagraphs.
The rupture disk device and safety or
safety relief valve combination to be
tested shall be arranged to duplicate
the combination assembly design.
(a) The test shall embody the minimum burst pressure of the rupture disk
device design which is to be used in
combination with safety or safety relief
valve design. The stamped bursting
pressure shall be between 90% and
100% of the stamped set pressure of
the valve.
(b) The test procedure to be used
shall be as follows.
The safety or safety relief valve (one
valve) shall be tested for capacity as an
individual valve, without the rupture disk
device at a pressure 10% above the
valve set pressure.
The rupture disk device shall then be
installed ahead of the safety or safety
relief valve and the disk burst to operate the valve. The capacity test shall be
performed on the combination at 10%
above the valve set pressure duplicating the individual safety or safety relief
valve capacity test.
(c) Tests shall be repeated with two
additional rupture disks of the same
nominal rating for a total of three rupture disks to be tested with the single
valve. The results of the test capacity
shall fall within a range of 10% of the
average capacity of the three tests.
Failure to meet this requirement shall
be cause to require retest for determination of cause of the discrepancies.
(d) From the results of the tests, a
Combination Capacity Factor shall be
determined. The Combination Capacity
Factor is the ratio of the average capacity determined by the combination tests
to the capacity determined on the individual valve.
The Combination Capacity Factor shall
be used as a multiplier to make appropriate changes in the ASME rated
relieving capacity of the safety or safety
relief valve in all sizes of the design.
The value of the Combination Capacity
Factor shall not be greater than one.
The Combination Capacity Factor shall
apply only to combinations of the same
design of safety or safety relief valve
and the same design of rupture disk device as those tested.
(e) The test laboratory shall submit the
test results to the ASME Designee for
acceptance of the Combination
Capacity Factor.
B. Optional Testing of Rupture Disk
Devices and Safety or Safety Relief
Valves
1. If desired, a valve manufacturer or a
rupture disk manufacturer may conduct
tests in the same manner as outlined in
(A)(4)(c) and (A)(4)(d) above using the
next two larger sizes of the design of
rupture disk device and safety or safety
relief valve to determine a Combination
Capacity Factor applicable to larger
sizes. If a greater Combination
Capacity Factor is established and can
be certified, it may be used for all larger
sizes of the combination, but shall not
be greater than one.
2. If desired, additional tests may be
conducted at higher pressures in accordance with (A)(4)(c) and (A)(4)(d)
above to establish a maximum
Combination Capacity Factor to be
used at all pressures higher than the
highest tested, but shall not be greater
than one.
C. Capacity of Breaking Pin Devices in
Combination With Safety Relief Valves
1. Breaking pin devices in combination
with safety relief valves shall be capacity tested in compliance with UG-131(D)
or UG-131(E) as a combination.
2. Capacity certification and Code
Symbol stamping shall be based on the
capacity established in accordance with
these paragraphs.
UG-133 Determination of Pressure
Relieving Requirements
A. Except as permitted in (B) below, the
aggregate capacity of the pressure relieving devices connected to any vessel
or system of vessels for the release of
a liquid, air, steam, or other vapor shall
be sufficient to carry off the maximum
quantity that can be generated or supplied to the attached equipment without
permitting a rise in pressure within the
vessel of more than 16% above the
maximum allowable working pressure
when the pressure relieving devices
are blowing.
B. Protective devices as permitted in UG125(C)(2), as protection against
excessive pressure caused by exposure to fire or other sources of external
heat, shall have a relieving capacity
sufficient to prevent the pressure from
rising more than 21% above the maximum allowable working pressure of the
vessel when all pressure relieving devices are blowing.
C. Vessels connected together by a system of adequate piping not containing
valves which can isolate any vessel
may be considered as one unit in figuring the required relieving capacity of
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
105
Anderson Greenwood Pressure Relief Valves
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ASME Code Section VIII – Division I (1995 Addenda)
pressure relieving safety devices to be
furnished.
D. Heat exchangers and similar vessels
shall be protected with a relieving device
of sufficient capacity to avoid overpressure in case of an internal failure.
E. The official rated capacity of a pressure
relieving safety device shall be that
which is stamped on the device and
guaranteed by the manufacturer.
F. The rated pressure relieving capacity of
a pressure relief valve for other than
steam or air shall be determined by the
method of conversion given in Appendix
11.
G. To prorate the relieving capacity at any
relieving pressure greater than 1.10p,
as permitted under UG-125, a multiplier
may be applied to the official relieving
capacity of a pressure relieving device
as follows:
P + 14.7
1.10p + 14.7
where:
P = relieving pressure, psi
p = set pressure, psi
For steam pressures above 1500 psi,
the above multiplier is not acceptable.
For steam valves with relieving pressures greater than 1500 psi and less
than or equal to 3200 psi, the capacity
at relieving pressures greater than
1.10p shall be determined using the
equation for steam and the correction
factor for high pressure steam in UG131 (E)(2) with the permitted absolute
relieving pressure and the coefficient K
for that valve design.
UG-134 Pressure Setting of
Pressure Relief Devices
A. When a single pressure relieving device is used, it shall be set to operate 24
at a pressure not exceeding the maximum allowable working pressure of the
vessel. When the required capacity is
provided in more than one pressure relieving device, only one device need be
set at or below the maximum allowable
working pressure, and the additional
devices may be set to open at higher
pressures but in no case at a pressure
higher than 105% of the maximum allowable working pressure, except as
provided in (B) below.
B. Protective devices permitted in UG125(C)(2) as protection against
excessive pressure caused by exposure to fire or other sources of external
heat shall be set to operate at a pressure not in excess of 110% of the
maximum allowable working pressure
of the vessel. If such a device is used
to meet the requirements of both UG125(C) and UG-125(C)(2), it shall be
set to operate at not over the maximum
allowable working pressure.
C. The pressure at which any device is set
to operate shall include the effects of
static head and constant back pressure.
D. 1. The set pressure tolerance for pressure relief valves shall not exceed
±2 psi for pressures up to and including
70 psi and ±3% for pressures above 70
psi, except as covered in (D)(2) below.
2.The set pressure tolerance of pressure
relief valves which comply with UG125(C)(3) shall be within -0%, +10%.
UG-135 Installation
A. Pressure relief devices for vapor application shall be connected to the vessel
in the vapor space above any contained
liquid or to piping connected to the vapor space in the vessel which is to be
protected.
B. The opening through all pipe and fittings between a pressure vessel and its
pressure relieving device shall have at
least the area of the pressure relieving
device inlet, and the flow characteristics
of this upstream system shall be such
that the pressure drop will not reduce
the relieving capacity below that required or adversely affect the proper
operation of the pressure relieving device. The opening in the vessel wall
shall be designed to provide direct and
unobstructed flow between the vessel
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
106
and its pressure relieving device. (See
Appendix M.)
C. When two or more required pressure
relieving devices are placed on one
connection, the inlet internal cross-sectional area of this connection shall be
either sized to avoid restricting flow to
the pressure relief devices or made at
least equal to the combined inlet areas
of the safety devices connected to it.
The flow characteristics of the upstream system shall satisfy the
requirements of (B) above. (See
Appendix M.)
D. Pressure relief devices for liquid service applications shall be connected
below the normal liquid level.
E. There shall be no intervening stop
valves between the vessel and its protective device or devices, or between
the protective device or devices and the
point of discharge, except:
1. when these stop valves are so constructed or positively controlled that the
closing of the maximum number of
block valves possible at one time will
not reduce the pressure relieving capacity provided by the unaffected
relieving devices below the required relieving capacity; or
2. under conditions set forth in Appendix M.
F. The safety devices on all vessels shall
be so installed that their proper functioning will not be hindered by the
nature of the vessel’s contents.
G. Discharge lines from pressure relieving
safety devices shall be designed to facilitate drainage or shall be fitted with
drains to prevent liquid from lodging in
the discharge side of the safety device,
and such lines shall lead to a safe place
of discharge. The size of the discharge
lines shall be such that any pressure
that may exist or develop will not reduce the relieving capacity of the
Notes
24. Set to operate means the set pressure of a
pressure relief valve or a spring loaded nonreclosing device; the bursting pressure of a
rupture disc device; or, the breaking pressure of a breaking pin device.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section VIII – Division I (1995 Addenda)
relieving devices below that required to
properly protect the vessel. [See UG136(A)(8) and Appendix M.]
UG-136 Minimum Requirements
for Pressure Relief Valves
A. Mechanical Requirements
1. The design shall incorporate guiding
arrangements necessary to ensure consistent operation and tightness.
2. The spring shall be designed so that
the full lift spring compression shall be
no greater than 80% of the nominal solid deflection. The permanent set of the
spring (defined as the difference between the free height and height
measured 10 min after the spring has
been compressed solid three additional
times after presetting at room temperature) shall not exceed 0.5% of the free
height.
3. Each pressure relief valve on air, water over 140°F, or steam service shall
have a substantial lifting device which
when activated will release the seating
force on the disk when the valve is subjected to a pressure of at least 75% of
the set pressure of the valve. Pilot operated pressure relief valves used on
these services shall be provided with either a lifting device as described above
or means for connecting and applying
pressure to the pilot adequate to verify
that the moving parts critical to proper
operation are free to move.
4. The seat of a pressure relief valve
shall be fastened to the body of the
valve in such a way that there is no
possibility of the seat lifting.
5. In the design of the body of the
valve, consideration shall be given to
minimizing the effects of deposits.
6. Valves having screwed inlet or outlet
connections shall be provided with
wrenching surfaces to allow for normal
installation without damaging operating
parts.
7. Means shall be provided in the
design of all valves for use under this
Division for sealing all initial adjustments which can be made without
disassembly of the valve. Seals shall be
installed by the manufacturer or assembler at the time of initial adjustment.
Seals shall be installed in a manner to
prevent changing the adjustment without breaking the seal. For valves larger
than NPS 1/2, the seal shall serve as a
means of identifying the manufacturer
or assembler making the initial adjustment.
8. If the design of a pressure relief
valve is such that liquid can collect on
the discharge side of the disk, the valve
shall be equipped with a drain at the
lowest point where liquid can collect (for
installation, see UG-135).
9. For pressure relief valves of the diaphragm type, the space above the
diaphragm shall be vented to prevent a
buildup of pressure above the diaphragm. Pressure relief valves of the
diaphragm type shall be designed so
that failure or deterioration of the diaphragm material will not impair the
ability of the valve to relieve at the rated
capacity.
B. Material Selections
1. Cast iron seats and disks are not
permitted.
2. Adjacent sliding surfaces such as
guides and disks or disk holders shall
both be of corrosion resistant material.
Springs of corrosion resistant material
or having a corrosion resistant coating
are required. The seats and disks of
pressure relief valves shall be of suitable material to resist corrosion by the
fluid to be contained.25
3. Materials used in bodies and bonnets
or yokes shall be listed in Section Il and
this Division. Carbon and low alloy steel
bodies, bonnets, yokes and bolting
(UG-20) subject to in-service temperatures colder than -20°F shall meet the
requirements of UCS-66, unless exempted by the following.
(a) The coincident Ratio defined in
Fig. UCS-66.1 is 0.4 or less
(b) The material(s) is exempted from
impact testing per Fig. UCS-66.
4. Materials used in nozzles, disks, and
other parts contained within the external structure of the pressure relief
valves shall be one of the following categories:
(a) listed in Section II;
(b) listed in ASTM Specifications;
(c) controlled by the manufacturer of
the pressure relief valve by a specification insuring control of chemical and
physical properties and quality at least
equivalent to ASTM Standards.
C. Inspection of Manufacturing and/or
Assembly of Pressure Relief Valves
1. A Manufacturer or assembler shall
demonstrate to the satisfaction of a
designated representative of the ASME
that his manufacturing, production, and
testing facilities and quality control procedures will insure close agreement
between the performance of random
production samples and the performance of those valves submitted for
Capacity Certification.
2. Manufacturing, assembly, inspection,
and test operations including capacity
are subject to inspections at any time
by an ASME designee.
3. The following schedule of tests ap-
Notes
25. The degree of corrosion resistance, appropriate to the intended service, shall be a
matter of agreement between the manufacturer and the purchaser.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
107
Anderson Greenwood Pressure Relief Valves
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ASME Code Section VIII – Division I (1995 Addenda)
plies to production pressure relief
valves certified under this Division, produced, assembled, tested, sealed, and
shipped by the Manufacturer and having a normal scope of size and capacity
within the capability of ASME accepted
laboratories. Production valves for capacity and operational testing shall be
selected by a designated representative
of the ASME and the testing shall be
carried out in the presence of a representative of the same organization at
an ASME accepted laboratory in accordance with the following.
(a) Initial capacity certification shall be
valid for 1-year during which time two
production valves shall be tested for
|operation and stamped capacity verification. Should any of these valves fail
to relieve at or above its stamped
capacity, or should it fail to meet performance requirements, the test shall be
repeated at the rate of two valves for
each valve that failed. Initial capacity
verification may be extended for 1-year
intervals until the valve is in production.
Valves having an adjustable blowdown
construction shall be adjusted by the
Manufacturer following successful testing for operation but prior to flow testing
so that the blowdown does not exceed
7% of the set pressure or 3 psi,
whichever is greater. This adjustment
may be made on the flow test facility.
(b) Thereafter, two valves shall be
tested within each 5-year period of
time. The valve manufacturer shall be
notified of the time of the test and may
have a witness present during the test.
Should any of these valves fail to relieve at or above its stamped capacity
or should it fail to meet performance requirements of this Division, the test
shall be repeated at the rate of two
valves for each valve that failed. Valves
having an adjustable blowdown construction shall be adjusted by the
manufacturer following successful test-
ing for operation but prior to flow testing
so that the blowdown does not exceed
7% of the set pressure or 3 psi, whichever is greater. This adjustment may be
made on the flow test facility. These
valves shall be furnished by the manufacturer or assembler. Failure of any of
these valves to meet the stamped capacity or the performance requirements
of this Division shall be cause for revocation within 60 days of the authorization to
use the Code Symbol on that particular
type of valve. During this period, the
manufacturer shall demonstrate the
cause of such deficiency and the action
taken to guard against future occurrence, and the requirements of (C)(3)(a)
above shall apply.
4. An assembler may be granted permission to use a Code Symbol Stamp
after demonstrating to the satisfaction
of a designated representative of the
ASME that his quality control procedures will insure that the assembled
valves meet the requirements of this
Division, including the following.
(a) Initially, two valves of each type or
series to which the Code stamp is to be
applied and which have been assembled, tested, and sealed by the
assembler shall be selected by a designated representative of the ASME and
tested for operation and stamped capacity verification. Should any valve fail
to relieve at or above its stamped capacity, or should it fail to meet
performance requirements, the test
shall be repeated at the rate of two
valves for each valve that failed. Valves
having an adjustable blowdown construction shall be adjusted by the
assembler following successful testing
for operation but prior to flow testing so
that the blowdown does not exceed 7%
of the set pressure or 3 psi, whichever
is greater. This adjustment may be
made on the flow test facility.
(b) Thereafter, within each 5-year period of time, two valves of each type or
series shall be selected by a designated representative of the ASME and
tested for operation and stamped capacity verification. The assembler shall
be notified of the time of the test and
may have a witness present during the
test. Should any valve fail to relieve at
or above its stamped capacity or should
it fail to meet performance requirements
of this Division, the test shall be repeated at the rate of two valves for each
valve that failed. Valves having an adjustable blowdown construction shall be
adjusted by the manufacturer following
successful testing for operation but prior to flow testing so that the blowdown
does not exceed 7% of the set pressure
or 3 psi, whichever is greater. This adjustment may be made on the flow test
facility. These valves shall be furnished
by the assembler. Failure of any valve
to meet the performance requirements
of this Division shall be cause for revocation within 60 days of the assembler’s
authorization to use the Code Symbol
on that particular type or series of
valve. During this period, the assembler
shall demonstrate the cause of such
deficiency and the action taken to guard
against future occurrence.
(c) All tests shall be carried out in the
presence of a designated representative of the ASME at an ASME accepted
laboratory.
(d) Use of the Code Symbol Stamp
by an assembler indicates the use of
original, unmodified parts in strict accordance with the instructions of the
manufacturer of the valve.
(e) In addition to the requirements of
UG-129, the nameplate marking shall
include the name of the manufacturer
and the assembler. The Code Symbol
Stamp shall be that of the assembler.26
Notes
26. Within the requirements of UG-136(C) and
UG-136(D): A manufacturer is defined as a
person or organization who is completely
responsible for design material selection
capacity certification, manufacture of all
component parts, assembly, testing, sealing, and shipping of pressure relief valves
certified under this Division. An assembler is
defined as a person or organization who
purchases or receives from a manufacturer
the necessary component parts or valves
and assembles, adjusts, tests, seals, and
ships pressure relief valves certified under
this Division, at a geographical location
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
108
other than and using facilities other than
those used by the manufacturer. An assembler may be organizationally independent of
a manufacturer or may be wholly or partly
owned by a manufacturer.
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section VIII – Division I (1995 Addenda)
D. Production Testing by Manufacturers
and Assemblers
1. Each pressure relief valve to which
the Code Symbol Stamp is to be applied
shall be subjected to the following tests
by the manufacturer or assembler. A
manufacturer or assembler shall have a
documented program for the application,
calibration, and maintenance of gauges
and instruments used during these
tests.
2. The primary pressure parts of each
valve exceeding NPS 1 inlet size or 300
psig set pressure where the materials
used are either cast or welded shall be
tested at a pressure of at least 1.5 times
the design pressure of the parts. These
tests shall be conducted after all machining operations on the parts have
been completed. There shall be no visible sign of leakage.
3. The secondary pressure zone of each
closed bonnet valve exceeding NPS 1
inlet size when such valves are designed for discharge to a closed system
shall be tested with air or other gas at a
pressure of at least 30 psig. There shall
be no visible sign of leakage.
4. Each valve shall be tested to demonstrate its popping or set pressure. Valves
marked for steam service or having special internal parts for steam service shall
be tested with steam, except that valves
beyond the capability of the production
steam test facility either because of size
or set pressure may be tested on air.
Necessary corrections for differentials in
popping pressure between steam and air
shall be established by the manufacturer
and applied to the popping point on air.
Valves marked for gas or vapor may be
tested with air. Valves marked for liquid
service shall be tested with water or other suitable liquid. Test fixtures and test
drums where applicable shall be of adequate size and capacity to ensure that
valve action is consistent with the
stamped set pressure within the tolerances required by UG-134(E).
5. A seat tightness test shall be conducted at a maximum expected operating
pressure, but at a pressure not exceeding the reseating pressure of the valve.
When testing with either water or steam,
a valve exhibiting no visible signs of
leakage shall be considered adequately
tight. Leakage tests conducted with air
shall be in accordance with industry accepted standards.
6. Testing time on steam valves shall be
sufficient, depending on size and design, to insure that test results are
repeatable and representative of field
performance.
E. Design Requirements. At the time of
the submission of valves for capacity
certification, or testing in accordance
with (C)(3) above, the ASME Designee
has the authority to review the design
for conformity with the requirements of
UG-136(A) and UG-136(B) and to reject or require modification of designs
which do not conform, prior to capacity
testing.
F. Welding and Other Requirements. All
welding, brazing, heat treatment, and
nondestructive examination used in the
construction of bodies, bonnets, and
yokes shall be performed in accordance
with the applicable requirements of this
Division.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
109
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section VIII – Division I (1995 Addenda)
Capacity Conversions For Safety Valves
11.1
The capacity of a safety or relief valve in
terms of a gas or vapor other than the
medium for which the valve was officially
rated shall be determined by application of
the following formulas:1
For steam,
Ws = 51.5KAP
For air,
Wa = CKAP
–––––
M
–––
T
√
C = 356
M = 28.97
T = 520 when Wa is the rated capacity
For any gas or vapor,
W = CKAP
These formulas may also be used when
the required flow of any gas or vapor is
known and it is necessary to compute the
rated capacity of steam or air.
For hydrocarbon vapors, where the actual
value of k is not known, the conservative
value, k = 1.001 has been commonly used
and the formula becomes
–––––
M
–––
W = 315 KAP
T
When desired, as in the case of light hydrocarbons, the compressibility factor Z
may be included in the formulas for gases
and vapors as follows:
√
√
Wa = rated capacity, converted to lb/hr
of air at 60°F, inlet temperature
W = flow of any gas or vapor, lb/hr
C = constant for gas or vapor which
is a function of the ratio of specific
heats, k = Cp /Cv (see Fig. 11-1)
K = coefficient of discharge
[see UG-131(D) and (E)]
A = actual discharge area of the safety
valve, in2
P = (set pressure x 1.10) plus atmospheric pressure, psia
M = molecular weight
W = CKAP
Example 1
√
KA =
Ws
= 4750 lb/hr
Example 2
Given: It is required to relieve 5000 lb/hr
of propane from a pressure vessel
through a safety valve set to relieve at a
pressure of Ps, psi, and with an inlet temperature of 125°F.
Solution:
Problem: What is the relieving capacity of
that valve in terms of air at 100°F for the
same pressure setting?
Solution:
Ws = 51.5KAP
3020 = 51.5KAP
KAP =
3020
For propane,
W = CKAP
–––––
M
–––
T
√
The value of C is not definitely known.
Use the conservative value, C = 315.
––––––––––––
44.09
––––––––
5000 = 315AP
460 + 125
KAP = 57.7
√
For steam,
For steam,
= 58.5
Ws = 51.5 KAP = (51.5)(57.7)
51.5
= 2970 lb/hr set to relieve at Ps, psi
Notes
Official Rating in Steam:
√
√
√
Problem: What total capacity in pounds of
steam per hour in safety valves must be
furnished?
–––––
M
–––
ZT
Given: A safety valve bears a certified capacity rating of 3020 lb/hr of steam for a
pressure setting of 200 psi.
T = absolute temperature at inlet
(°F + 460)
1. Knowing the official rating capacity of a
safety valve which is stamped on the valve,
it is possible to determine the overall value
of KA in either of the following formulas in
cases where the value of these individual
terms is not known:
–––––
M
–––
T
–––––––––
28.97
––––––––
= 356 KAP
460 + 100
–––––––
28.97
= (356) (58.5)
––––––
560
Wa = CKAP
Molecular weights of some of the common
gases and vapors are given in Table 11-1.
–––––
M
–––
T
where:
Ws = rated capacity, lb/hr of steam
For air,
Official Rating in Air:
Wa
KA = ––––
CP
–––––
T
–––
M
√
This value for KA is then substituted in the
above formulas to determine the capacity of the
safety valve in terms of the new gas or vapor.
51.5P
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
110
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section VIII – Division I (1995 Addenda)
Capacity Conversions For Safety Valves
Constant
C
k
1.00
315
1.38
354
1.02
318
1.40
356
Constant
C
1.04
320
1.42
358
1.06
322
1.44
359
1.08
324
1.46
361
1.10
327
1.48
363
1.12
329
1.50
364
1.14
331
1.52
366
1.16
333
1.54
368
1.18
335
1.56
369
1.20
337
1.58
371
1.22
339
1.60
372
1.24
341
1.62
374
1.26
343
1.64
376
1.28
345
1.66
377
1.30
347
1.68
379
1.32
349
1.70
380
1.34
351
2.00
400
1.36
352
2.20
412
Figure 11-1
Constant C for Gas or Vapor Related to Ratio of
Specific Heats (k = Cp/Cv)
400
390
380
Constant, C
k
370
360
350
Flow Formula Calculations
340
W = K (CAP
330
C = 520
k
M/T)
( k +2 1 (
k+1
k-1
320
▲
1.2
▲
1.0
▲
1.6
▲
1.4
▲
1.8
▲
2.0
k
Notes
2. Before converting the capacity of a safety
valve from any gas to steam, the requirements of UG-131(B) must be met.
Example 3
Example 4
Given: It is required to relieve 1000 lb/hr of
ammonia from a pressure vessel at 150°F.
Given: A safety valve bearing a certified
rating of 10,000 cu ft/min of air at 60°F
and 14.7 psia (atmospheric pressure).
Problem: What is the required total capacity in pounds of steam per hour at the
same pressure setting?
Solution:
Solution:
For ammonia,
W = CKAP
Problem: What is the flow capacity of this
safety valve in pounds of saturated steam
per hour for the same pressure setting?
–––––
M
–––
T
√
Manufacturer and user agree to use
k = 1.33; from Fig. 11-1, C = 350.
––––––––––
17.03
–––––––––
1000 = 350 CKAP
460 + 150
√
KAP = 17.10
For steam,
For air: Weight of dry air at 60°F and
14.7 psia is 0.0766 lb/cu ft.
Wa = 10,000 x 0.0766 x 60 = 45,960 lb/hr
45,960 = 356 KAP
KAP = 546
––––––––
28.97
–––––––
460 + 60
√
For steam,2
Ws = 51.5 KAP = (51.5)(546)
= 28,200 lb/hr
Ws = 51.5 KAP = 51.5 x 17.10
= 880 lb/hr
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
111
Anderson Greenwood Pressure Relief Valves
Technical Manual
ASME Code Section VIII – Division I (1995 Addenda)
Table 11-1
11.2
Molecular Weights of Gases and Vapors
Air
28.97
Freon 22
86.48
Acetylene
26.04
Freon 114
170.90
Ammonia
17.03
Hydrogen
Butane
58.12
Hydrogen Sulfide
34.08
2.02
Carbon Dioxide
44.01
Methane
16.04
Chlorine
70.91
Methyl Chloride
50.48
Ethane
30.07
Nitrogen
28.02
Ethylene
28.05
Oxygen
32.00
Freon 11
137.371
Propane
44.09
Freon 12
120.9
Sulfur Dioxide
64.06
Figure 11-2
Flow Capacity Curve for Rating Nozzle Type Safety Valves on Saturated
Water (Based on 10% Overpressure)
B. To determine the saturated water
capacity of a valve currently rated
under UG-131 and meeting the requirements of (A) above, refer to Fig. 11-2.
Enter the graph at the set pressure of
the valve, move vertically upward to the
saturated water line and read horizontally the relieving capacity. This capacity is
the theoretical, isentropic value arrived
at by assuming equilibrium flow and
calculated values for the critical pressure ratio.
Notes
3. The manufacturer, user, and inspector are
all cautioned that for the following rating to
apply, the valve shall be continuously subjected to saturated water. If, after initial relief
the flow media changes to quality steam,
the valve shall be rated as per dry saturated
steam. Valves installed on vessels or lines
containing steam-water mixture shall be
rated on dry saturated steam.
24
Flow capacity x 10-4 (lb/hr/in2)
A. Since it is realized that the saturated
water capacity is configuration sensitive, the following applies only to those
safety valves that have a nozzle type
construction (throat to inlet diameter ratio of 0.25
to 0.80 with a continuously contoured
change and have exhibited a coefficient
KD in excess of 0.90). No saturated water rating shall apply to other types of
construction.3
20
16
Saturated water
12
8
4
0
▲
0
▲
400
▲
800
▲
1200
▲
1600
▲
2000
▲
2400
▲
2800
▲
3200
Set pressure, psig
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
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Appendix M Installation and Operation – ASME VIII Division I - (1995 Addenda)
M-1
Introduction
A. The rules in this Appendix are for general information only, because they pertain
to the installation and operation of pressure vessels, which are the prerogative
and responsibility of the law enforcement authorities in those states and
municipalities which have made provision for the enforcement of Section VIII.
B. It is permissible to use any departures
suggested herein from provisions in the
mandatory parts of this Division when
granted by the authority having legal
jurisdiction over the installation of pressure vessels.
M-2
Corrosion
A. Vessels subject to external corrosion
shall be so installed that there is sufficient access to all parts of the exterior
to permit proper inspection of the exterior, unless adequate protection against
corrosion is provided or unless the vessel is of such size and is so connected
that it may readily be removed from its
permanent location for inspection.
B. Vessels having manholes, handholes,
or cover plates to permit inspection of
the interior shall be so installed that
these openings are accessible.
C. In vertical cylindrical vessels subject to
corrosion, to insure complete drainage,
the bottom head, if dished, should
preferably be concave to pressure.
M-3
Marking on the Vessel
The marking required by this Division shall
be so located that it will be accessible after
installation and when installed shall not be
covered with insulation or other material that
is not readily removable [see UG-116(J)].
M-4
Pressure Relieving Safety Devices
The general provisions for the installation
of pressure relieving devices are fully covered in UG-135. The following paragraphs
contain details in arrangement of stop
valves for shutoff control of safety pres-
sure relief devices which are sometimes
necessary to the continuous operation of
processing equipment of such a complex
nature that the shutdown of any part of it
is not feasible. There are also rules with
regard to the design of inlet and discharge
piping to and from safety and relief valves,
which can only be general in nature because the design engineer must fit the
arrangement and proportions of such a
system to the particular requirements in
the operation of the equipment involved.
M-5
Stop Valves Between Pressure
Relieving Device and Vessel
A. A vessel, in which pressure can be
generated because of service conditions, may have a full-area stop valve
between it and its pressure relieving
device for inspection and repair purposes only. When such a stop valve is
provided, it shall be so arranged that it
can be locked or sealed open, and it
shall not be closed except by an authorized person who shall remain stationed
there during that period of the vessel’s
operation within which the valve remains closed, and who shall again lock
or seal the stop valve in the open position before leaving the station.
B. A vessel or system [see UG-133(C)] for
which the pressure originates from an
outside source exclusively may have
individual pressure relieving devices on
each vessel, or connected to any point
on the connecting piping, or on any one
of the vessels to be protected. Under
such an arrangement, there may be a
stop valve between any vessel and the
pressure relieving devices, and this
stop valve need not be locked open,
provided it also closes off that vessel
from the source of pressure.
M-6
Stop Valves on the Discharge Side
of a Pressure Relieving Device
[See UG-135(E)]
A full-area stop valve may be placed on
the discharge side of a pressure relieving
device when its discharge is connected to
a common header with other discharge
lines from other pressure relieving devices
on nearby vessels that are in operation,
so that this stop valve when closed will
prevent a discharge from any connected
operating vessels from backing up beyond
the valve so closed. Such a stop valve
shall be so arranged that it can be locked
or sealed in either the open or closed position, and it shall be locked or sealed in
either position only by an authorized person. When it is to be closed while the
vessel is in operation, an authorized person shall be present, and he shall remain
stationed there; he shall again lock or seal
the stop valve in the open position before
leaving the station. Under no condition
should this valve be closed while the vessel is in operation except when a stop
valve on the inlet side of the safety relieving device is installed and is first closed.
M-7
Inlet Pressure Drop for High Lift,
Top Guided Safety, Safety Relief,
and Pilot Operated Pressure Relief
Valves in Compressible Fluid
Service
A. The nominal pipe size of all piping,
valves and fittings, and vessel components between a pressure vessel and
its safety, safety relief, or pilot operated
pressure relief valves shall be at least
as large as the nominal size of the device inlet, and the flow characteristics
of the upstream system shall be such
that the cumulative total of all nonrecoverable inlet losses shall not exceed
3% of the valve set pressure. The inlet
pressure losses will be based on the
valve nameplate capacity corrected for
the characteristics of the flowing fluid.
B. When two or more required safety, safety relief, or pilot operated pressure relief
valves are placed on one connection,
the inlet internal cross-sectional area of
this connection shall be either sized to
avoid restricting flow to the pressure relief valves or made at least equal to the
combined inlet areas of the safety
valves connected to it. The flow characteristics of the upstream system shall
meet the requirements of (A) above with
all valves relieving simultaneously.
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designs and specifications without notice.
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Appendix M Installation and Operation – ASME VIII Division I - (1995 Addenda)
M-8
Discharge Lines from Safety Devices
A. Where it is feasible, the use of a short
discharge pipe or vertical riser, connected through long-radius elbows from each
individual device, blowing directly to the
atmosphere, is recommended. Such discharge pipes shall be at least of the
same size as the valve outlet. Where the
nature of the discharge permits, telescopic (sometimes called ‘broken’)
discharge lines, whereby condensed vapor in the discharge line, or rain, is
collected in a drip pan and piped to a
drain, are recommended.1
B. When discharge lines are long, or
where outlets of two or more valves
having set pressures within a comparable range are connected into a
common line, the effect of the back
pressure that may be developed therein when certain valves operate must
be considered [see UG-135(G)]. The
sizing of any section of a common-discharge header downstream from each
of the two or more pressure relieving
devices that may reasonably be expected to discharge simultaneously
shall be based on the total of their outlet areas, with due allowance for the
pressure drop in all downstream sections. Use of specially designed valves
suitable for use on high or variable
back pressure service should be
considered.
C. The flow characteristics of the discharge
system of high lift, top guided safety, safety relief, or pilot operated pressure relief
valves in compressible fluid service shall
be such that the static pressure developed at the discharge flange of a
conventional direct spring loaded valve
will not exceed 10% of the set pressure
when flowing at stamp capacity. Other
valve types exhibit various degrees of
tolerance to back pressure and the manufacturer’s recommendation should be
followed.
D. All discharge lines shall be run as direct as is practicable to the point of
final release for disposal. For the
longer lines, due consideration shall be
given to the advantage of long-radius
elbows, avoidance of closeup fittings,
and the minimizing of excessive line
strains by expansion joints and wellknown means of support to minimize
line-sway and vibration under operating
conditions.
E. Provisions should be made in all
cases for adequate drainage of discharge lines.2
M-9
Pressure Drop, Nonreclosing
Pressure Relief Devices
Piping, valves and fittings, and vessel
components comprising part of a nonreclosing device pressure relieving system shall be sized to prevent the vessel
pressure from rising above the allowable
overpressure.
M-10
General Advisory Information on
the Characteristics of Safety Relief
Valves Discharging into a Common
Header
Because of the wide variety of types and
kinds of safety relief valves, it is not considered advisable to attempt a description
in this Appendix of the effects produced
by discharging them into a common
header. Several different types of valves
may conceivably be connected into the
same discharge header and the effect of
back pressure on each type may be radically different. Data compiled by the
manufacturers of each type of valve
used should be consulted for information
Notes
1. This construction has the further advantage
of not transmitting discharge-pipe strains to
the valve. In these types of installation, the
back pressure effect will be negligible, and
no undue influence upon normal valve operation can result.
2. It is recognized that no simple rule can be
applied generally to fit the many installation
requirements, which vary from simple short
lines that discharge directly to the atmosphere to the extensive manifold discharge
piping systems where the quantity and rate
of the product to be disposed of requires
piping to a distant safe place.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
114
relative to its performance under the conditions anticipated.
M-11
Pressure Differentials for Pressure
Relief Valves
Due to the variety of service conditions
and the various designs of safety and
safety relief valves, only general guidance
can be given regarding the differential between the set pressure of the valve (see
UG-134) and the operating pressure of
the vessel. Operating difficulty will be minimized by providing an adequate
differential for the application. The following is general advisory information on the
characteristics of the intended service and
of the safety or safety relief valves that
may bear on the proper pressure differential selection for a given application.
These considerations should be reviewed
early in the system design since they may
dictate the MAWP of the system.
A. Consideration of the Process
Characteristics in the Establishment of
the Operating Margin to Be Provided.
To minimize operational problems, it is
imperative that the user consider not
only normal operating conditions of fluids, pressures, and temperatures, but
also start-up and shutdown conditions,
process upsets, anticipated ambient
conditions, instrument response times,
pressure surges due to quick closing
valves, etc. When such conditions are
not considered, the pressure relieving
device may become, in effect, a pressure controller, a duty for which it is not
designed. Additional consideration
should be given to hazard and pollution
associated with the release of the fluid.
Larger differentials may be appropriate
for fluids which are toxic, corrosive, or
exceptionally valuable.
Anderson Greenwood Pressure Relief Valves
Technical Manual
Appendix M Installation and Operation – ASME VIII Division I - (1995 Addenda)
B. Consideration of Safety Relief Valve
Characteristics. The blowdown characteristic and capability is the first
consideration in selecting a compatible
valve and operating margin. After a
self-actuated release of pressure, the
valve must be capable of reclosing
above the normal operating pressure.
For example, if the valve is set at 100
psig with a 7% blowdown, it will close
at 93 psig. The operating pressure
must be maintained below 93 psig in
order to prevent leakage or flow from a
partially open valve. Users should exercise caution regarding the blowdown
adjustment of large spring-loaded
valves. Test facilities, whether owned
by Manufacturers, repair houses, or
users, may not have sufficient capacity
to accurately verify the blowdown setting. The settings cannot be considered
accurate unless made in the field on
the actual installation.
Pilot-operated valves represent a special case from the standpoints of both
blowdown and tightness. The pilot portion of some pilot-operating valves can
be set at blowdowns as short as 2%.
This characteristic is not, however, reflected in the operation of the main
valve in all cases. The main valve can
vary considerably from the pilot depending on the location of the two
components in the system. If the pilot is
installed remotely from the main valve,
significant time and pressure lags can
occur, but reseating of the pilot assures
reseating of the main valve. The pressure drop in the connecting piping
between the pilot and the main valve
must not be excessive; otherwise, the
operation of the main valve will be adversely affected.
The tightness of the main valve portion
of these combinations is considerably
improved above that of conventional
valves by pressure loading the main
disk or by the use of soft seats or both.
Despite the apparent advantages of pilot-operated valves, users should be
aware that they should not be employed in abrasive or dirty service, in
applications, where coking, polymerization, or corrosion of the wetted pilot
parts can occur, or where freezing or
condensation of the lading fluid at ambient temperatures is possible. For all
applications, the valve Manufacturer
should be consulted prior to selecting a
valve of this type.
Tightness capability is another factor affecting valve selection, whether spring
loaded or pilot operated. It varies
somewhat depending on whether metal
or resilient seats are specified, and
also on such factors as corrosion or
temperature. The required tightness
and test method should be specified to
comply at a pressure no lower than the
normal operating pressure of the
process. A recommended procedure
and acceptance standard is given in
ANSI B146.1. It should also be remembered that any degree of tightness
obtained should not be considered permanent. Service operation of a valve
almost invariably reduces the degree of
tightness.
Application of special designs such as
O-rings or resilient seats should be reviewed with the valve Manufacturer.
The anticipated behavior of the valves
includes allowance for a plus-or-minus
tolerance on set pressure which varies
with the pressure level. Installation
conditions, such as back pressure,
variations, and vibrations, influence
selection of special types and an increase in differential pressure.
C. General Recommendations. The
following pressure differentials are recommended unless the safety or safety
relief valve has been designed or tested in a specific or similar service and a
smaller differential has been recommended by the Manufacturer.
A minimum difference of 5 psi is recommended for set pressures to 70 psi. In
this category, the set pressure tolerance is ±2 psi [UG-134(D)(1)], and the
differential to the leak test pressure is
10% or 5 psi, whichever is greater.
A minimum differential of 10% is recommended for set pressures from 71 psi
to 1000 psi. In this category, the set
pressure tolerance is ±3% and the dif-
ferential to the leak test pressure is 10%.
A minimum differential of 7% is recommended for set pressures above 1000
psi. In this category, the set pressure
tolerance is ±3% and the differential to
the leak test pressure should be 5%.
Valves having small seat sizes will require additional maintenance when the
pressure differential approaches these
recommendations.
M-12
Installation of Safety and Safety
Relief Valves
Spring loaded safety and safety relief
valves normally should be installed in the
upright position with the spindle vertical.
Where space or piping configuration preclude such an installation, the valve may
be installed in other than the vertical position provided that:
A. the valve design is satisfactory for such
position;
B. the media is such that material will not
accumulate at the inlet of the valve; and
C. drainage of the discharge side of the
valve body and discharge piping is adequate.
M-13
Reaction Forces and Externally
Applied Loads
A. Reaction Thrust. The discharge of a
pressure relief valve imposes reactive
flow forces on the valve and associated
piping. The design of the installation
may require computation of the bending moments and stresses in the piping
and vessel nozzle. There are momentum effects and pressure effects at
steady state flow as well as transient
dynamic loads caused by opening.
B. External Loads. Mechanical forces may
be applied to the valve by discharge
piping as a result of thermal expansion,
movement away from anchors, and
weight of any unsupported piping. The
resultant bending moments on a closed
pressure relief valve may cause valve
leakage and excessive stress in inlet
piping. The design of the installation
should consider these possibilities.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
115
Anderson Greenwood Pressure Relief Valves
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Appendix M Installation and Operation – ASME VIII Division I - (1995 Addenda)
M-14
Sizing of Pressure Relief Devices
for Fire Conditions
A. Excessive pressure may develop in
pressure vessels by vaporization of the
liquid contents and/or expansion of vapor content due to heat influx from the
surroundings, particularly from a fire.
Pressure relief systems for fire conditions are usually intended to release
only the quantity of product necessary
to lower the pressure to a predetermined safe level, without releasing an
excessive quantity. This control is especially important in situations where
release of the contents generates a
hazard because of flammability or toxicity. Under fire conditions,
consideration must also be given to the
possibility that the safe pressure level
for the vessel will be reduced due to
heating of the vessel material, with a
corresponding loss of strength.
B. Several formulas have evolved over the
years for calculating the pressure relief
capacity required under fire conditions.
The major differences involve heat flux
rates. There is no single formula yet
developed which takes into account all
of the many factors which could be
considered in making this determina-
tion. When fire conditions are a consideration in the design of a pressure
vessel, the following references which
provide recommendations for specific
installations may be used:
API RP 520, Recommended Practice
for the Design and Installation of
Pressure-Relieving Systems in
Refineries, Part I– Design, 1976,
American Petroleum Institute,
Washington, DC
API Standard 2000, Venting Atmospheric and Low Pressure Storage Tanks
(nonrefrigerated and refrigerated),
1973, American Petroleum Institute,
Washington, DC
AAR Standard M-1002, Specifications
for Tank Cars, 1978, Association of
American Railroads, Washington, DC
Safety Relief Device Standards: S-1.1,
Cylinders for Compressed Gases; S-1.2,
Cargo and Portable Tanks; and S-1.3,
Compressed Gas Storage Containers.
Compressed Gas Association, New York
NFPA Code Nos. 30, 59, and 59A, National
Fire Protection Association, Boston, MA
Pressure-Relieving Systems for Marine
Cargo Bulk Liquid Containers, 1973,
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
116
National Academy of Sciences,
Washington, DC
Bulletin E-2, How to Size Safety Relief
Devices, Phillips Petroleum Company,
Bartlesville, OK
A Study of Available Fire Test Data as
Related to Tank Car Safety Device
Relieving Capacity Formulas, 1971,
Phillips Petroleum Company,
Bartlesville, OK
M-15
Pressure Indicating Device
If a pressure indicating device is provided
to determine the vessel pressure at or
near the set pressure of the relief device,
one should be selected that spans the set
pressure of the relief device and is graduated with an upper limit that is neither less
than 1.25 times the set pressure of the relief device nor more than twice the
maximum allowable working pressure of
the vessel. Additional devices may be installed if desired.
Anderson Greenwood Pressure Relief Valves
Technical Manual
Following is an Excerpt from API - RP 520
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designs and specifications without notice.
117
Anderson Greenwood Pressure Relief Valves
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API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
Section 2 – Pressure Relief Devices
2.2.4 Pressure Relief Valves
2.1 General
2.2.4.1 Conventional Pressure
Relief Valves
Conventional pressure relief valves are
used when the discharge is through a
short tail pipe that vents to the atmosphere
or through a low-pressure manifold system
that carries the discharged fluid of one or
more valves to a remote location for disposal. Normally, the spring force is the
differential between the set pressure and
atmospheric pressure. The set pressure
will therefore be increased by superimposed back pressure unless the spring
force is adjusted accordingly. Built-up
back pressure may also affect valve
performance; therefore, the impact of
downstream pressure when one or more
valves discharge into a common manifold
should be determined by referring to the
appropriate manufacturer’s catalog.
This section describes the basic principles, operational characteristics,
applications, and selection of pressure
relief devices used independently or in
combination. These devices include
spring-loaded and pilot-operated pressure
relief valves, rupture disk devices, and
other pressure relief devices. These devices are described in the text and
illustrated in Figures 2-17.
2.2 Spring-Loaded Pressure Relief
Valves
2.2.1 Safety Valves
Safety valves are spring-loaded pressure
relief devices designed to provide full
opening with minimum overpressure. Static
pressure retained in the huddling chamber
and the kinetic energy of the gas or vapor
are utilized to overcome the spring force on
the disc as it lifts, resulting in pop action.
The closing pressure will be at a point below the set pressure and will be reached
after the blowdown phase is completed.
2.2.2 Relief Valves
Relief valves are spring-loaded pressure
relief devices designed for use in liquid
service. At set pressure, the inlet pressure
force overcomes the spring force and the
disc begins to lift off the seat. As inlet
pressure increases, the disk lift increases
to allow an increase in the flow. The closing pressure will be at a point below the
set pressure and will be reached after the
blowdown phase is completed. Relief
valve capacities are usually rated at 10
or 25% overpressure, depending on the
application.
2.2.3 Safety Relief Valves
Safety relief valves are spring-loaded pressure relief devices that provide the
characteristics of a safety valve when used
in gas or vapor service and the characteristics of a relief valve when used in liquid
service. Safety relief valves are generally
provided with bonnets that enclose the
spring and provide a pressure-tight housing for use in conventional or balanced
types, depending on the effect of back
pressure on their performance.
The interaction of the forces within the
valve and the effects of back pressure on
the opening are illustrated in Figure 18.
Available conventional pressure relief
valves have disks that have a greater disk
area, AD, than the nozzle seat area, AN.
If the spring bonnet is vented to the atmosphere, the back pressure acts with
the vessel pressure to overcome the
spring force. This condition makes the
opening pressure less than it is when the
valve is set with atmospheric pressure on
its discharge; however, if the spring bonnet is vented to the valve discharge
instead of to the atmosphere, the back
pressure acts with the spring force to increase the opening pressure. Variation in
the superimposed back pressure will directly affect the opening pressure and
should be evaluated in system design.
Conventional pressure relief valves, as
normally installed, show unsatisfactory
performance when excessive built-up
back pressure develops from the flow
through valve and piping as a result of the
same unbalanced forces that affect the
set pressure. Performance data observed
during the investigation of the built-up
back pressure problem are shown in
Figure 19. The information is plotted as
the ratio of the valve capacity at any given
built-up back pressure to the valve capacity without built-up back pressure versus
the ratio of the built-up back pressure to
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
118
the valve set pressure. The capacity curve
is the result of the balance of forces acting
on the disk. As long as the built-up back
pressure is less than the overpressure after the valve opens, the valve will remain
open and perform satisfactorily under
flowing conditions, and it will have flow
characteristics that are basically similar to
those in a theoretical nozzle performance.
If, however, the built-up back pressure is
increased at a greater rate than the overpressure, the balance of forces will tend to
close the valve, which can become unstable and cause the flow to fall off rapidly.
This instability is caused by a dynamic
pressure imbalance or a harmonic resonance. The valve may start to flutter or
chatter.
Flutter refers to the abnormally rapid
reciprocating motion of the movable parts
of a pressure relief valve in which the disk
does not contact the seat. Chatter refers
to the motion that causes the disk to contact the seat and damage the valve and
associated piping. The allowable built-up
back pressure must therefore be considered for each amount of overpressure
used.
Conventional pressure relief valves
should typically not be used when the
built-up back pressure is greater than
10% of the set pressure at 10% overpressure. A higher maximum allowable built-up
back pressure may be used for overpressure greater than 10%. The combined
effect of the superimposed and built-up
back pressures on the performance characteristics of the valves must be
considered when more than one pressure
relief valve discharges into a common
manifold at the same time.
The theoretical performance for a nozzle
is plotted in Figure 20. The curve represents the maximum theoretical flow
attainable for any ideal gas that has the
specific heat ratio of K = 1.3. The theoretical nozzle maintains flow capacity up to
the critical flow pressure and then gradually diminishes to zero.
The theoretical rate of flow through the
nozzle depends on the absolute upstream
pressure and is independent of the downstream pressure when the back pressure
is less than the critical flow pressure;
Anderson Greenwood Pressure Relief Valves
Technical Manual
API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of
Pressure Relieving Devices in Refineries
1. This figure conforms with the requirements
of Section VIII of the ASME Boiler and
Pressure Vessel Code.
2. The pressure conditions shown are for
pressure relief valves installed on a pressure vessel.
3. Allowable set-pressure tolerances will be
in accordance with the applicable codes.
4. The maximum allowable working pressure
is equal to or greater than the design pressure for a coincident design temperature.
5. The operating pressure may be higher or
lower than 90.
6. Section VIII, Division 1, Appendix M, of the
ASME Code should be referred to for guidance on blowdown and pressure
differentials.
Figure 1 – Pressure-Level Relationships for Pressure Relief Valves
Pressure Vessel Requirements
Vessel
Pressure
Maximum allowable
accumulated
pressure (fire
exposure only)
121
Maximum allowable
accumulated pressure for
multiple-valve installation
(other than fire exposure)
116
Maximum allowable
accumulated pressure for
single-valve installation
(other than fire exposure)
110
Maximum allowable
accumulated
pressure for
design pressure
Typical Characteristics of
Pressure Relief Valves
Maximum relieving
pressure for fire sizing
120
Multiple valves maximum
relieving pressure for
process sizing
115
Single valve maximum relieving
pressure for process sizing
Percent of maximum allowable working pressure (gauge)
Notes
Maximum allowable set pressure
for supplemental valves (fire
exposure)
Overpressure (maximum)
Maximum allowable set
pressure for additional
valves (process)
105
100
Simmer
(typical)
95
Maximum allowable set
pressure for single valve
Start to open
Blowdown (typical)
(see Note 6)
Closing pressure
for a single valve
Maximum expected
operating pressure
(See Notes 5 and 6)
90
Leak test pressure
(typical)
85
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designs and specifications without notice.
119
Anderson Greenwood Pressure Relief Valves
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API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of
Pressure Relieving Devices in Refineries
Cap
Cap
Stem
(spindle)
Stem
(spindle)
Adjusting
Screw
Adjusting
Screw
Spring
Spring
Bonnet
Bonnet
Note
1. For corrosion isolation, an unbalancedbellows safety relief valve is available.
Vent
Bellows
Seating
Surface
Disk
Seating
Surface
Disk
Adjusting
Ring
Body
Adjusting
Ring
Body
Nozzle
Nozzle
Figure 2 – Conventional Safety
Relief Valve With a Single Adjusting Ring for Blowdown Control
Figure 3 – Balanced-Bellows Safety
Relief Valve1
Cap
Stem
(spindle)
Adjusting
Screw
Stem
(spindle)
Adjusting
Screw
Bonnet
Cap
Spring
Spring
Bonnet
Vent
Balanced
Piston
Bellows
Seating
Surface
Disk
Adjusting
Ring
Body
Seating
Surface
Disk
Base,
Body
Nozzle
Figure 4 – Balanced-Bellows
Safety Relief Valve With an
Auxiliary Balanced Piston
Figure 5 – Thermal Relief
(Liquid Relief Valve)
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120
Anderson Greenwood Pressure Relief Valves
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API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
however, when the back pressure is increased beyond the critical flow pressure,
the flow is reduced. (See 4.3 for information about the sizing of pressure relief
valves for critical and subcritical flow.)
2.2.4.2 Balanced Pressure Relief Valves
The design of balanced pressure relief
valves incorporates means for reducing
the effect of back pressure on the set
pressure and for minimizing the effect of
built-up back pressure on performance
characteristics such as opening and closing pressure, lift, and relieving capacity
(see Section 4). Balanced valves are of
two basic types: the piston and the bellows (see Figure 21).
Several variations of the piston valve are
manufactured. The guide on the piston is
vented so that the back pressure on
opposing faces of the valve disk is cancelled. The top face of the piston has an
area, Ap, the same as the nozzle seat
area, AN, and is subjected to atmospheric
pressure by venting the spring bonnet.
The vented gas from the bonnets of balanced piston valves should be disposed of
safely and with minimum restrictions.
Figure 6 – Pop Action Pilot Operated Valve (Flowing Type)
Spindle
Relief Seat
Pilot
Exhaust
Spacer Rod
Pilot-to-Dome Connection
Piston
Optional Pilot
Filter
Reseat Seat
Backflow Preventor
Piston
Seat
Outlet
Remote Pressure
Pickup (optional)
Main Valve
Inlet
Figure 7 – Pop Action Pilot Operated Valve (Nonflowing Type)
The effective bellows area, AB, of bellows
valves is the same as the nozzle seat
area, AN. The arrangement of the bellows
in the valve prevents the back pressure
from acting on the top side of the disk
within the effective bellows area, AB. The
disk area, AD, extending beyond the bellows and the opposing nozzle seat area
cancel the effect of the back pressure on
the valve disk so that there are no unbalanced forces under any downstream
pressure variations. The bellows additionally serves to isolate the disk guide,
spring, and other top works parts from the
lading fluid. This feature may be important
if the lading fluid is corrosive or may foul
the pressure relief valve. Because of
physical size limitations, balanced bellows
are not available in certain valve designs
and sizes. If balanced bellows are not
available, unbalanced bellows valves may
be specified when corrosion isolation
alone is intended.
The balanced pressure relief valve makes
possible higher pressures in the relief discharge manifolds. Both balanced valves
shown in Figure 21 should have bonnet
vents large enough to ensure that no
Set Pressure
Adjusting Screw
Seating
Surface
Spindle
Pilot
Exhaust
Pilot Supply
Line
External
Blowdown
Adjustment
Optional
Pilot
Piston
Outlet
Seat
Internal
Pressure
Pickup
Main
Valve
Inlet
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Figure 8 – Modulating Pilot Operated Valve (Flowing Type)
Sense Diaphragm
Sensitivity Adjustment
Sense Chamber
Spindle
Pilot Supply Line
Piston
appreciable back pressure exists during
flow conditions. If the valve is located
where atmospheric venting (usually not a
large amount) would present a hazard,
the vent should be piped to a safe location
that is independent of the valve discharge
system.
2.2.4.3 Valve Characteristics
Figure 22 shows the disk travel from the
set pressure, A, to the maximum relieving
pressure, B, during the overpressure incident and to the closing pressure, C,
during the blowdown.
Seat
Optional Pilot Filter
Outlet
2.3 Pilot Operated Pressure Relief
Valves
The two basic types of pilot operated
pressure relief valves are the piston type
and the diaphragm type.
Seat
Internal Pressure Pickup
Main Valve
Inlet
The piston type valve consists of the main
valve, which encloses a floating piston,
and an external pilot valve (see Figures 69). The piston is designed to have a larger
effective area on the top than on the bottom. Up to the set pressure, the top and
bottom areas are exposed to the same inlet operating pressure. Because of the
larger effective area on the top of the piston, the net force holds the piston tightly to
the main valve seat. As the operating pressure increases, the net seating force
increases and tends to make the valve
tighter. At the set point, the pilot vents the
pressure from the top of the piston; the resulting net force unseats the piston, and
process flow is established through the
main valve. After the overpressure incident, the pilot will close the vent from the
top of the piston, thereby re-establishing
pressure, and the net force will cause the
piston to reseat.
Figure 9 – Pilot Operated Relief Valve With A Non-flowing Modulating
Pilot Valve
Vent Valve
Filter
Test Connection
Inlet Valve
Seat
Piston
Outlet
The diaphragm type pilot operated relief
valve is similar to the piston type except
that the piston is replaced by a flexible
diaphragm and disk. The diaphragm provides the unbalance function of the piston.
The disk, which normally closes the main
valve inlet, is integral with a flexible diaphragm (see Figure 10). The external
pilot valve serves the same function to
sense process pressure, vent the top of
Internal Pressure Pickup
Main Valve
Inlet
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The pilots may be either a flowing or nonflowing type. The flowing type allows
process fluid to flow through the pilot
when the main valve is open; the nonflowing type does not. The user should consult
the manufacturer to determine the advantages and disadvantages of either type.
A backflow preventor is required when the
possibility exists of developing a pressure
on the discharge side of the valve that exceeds the inlet pressure of the valve. The
differential area will cause the piston to lift,
and flow in the valve will be reversed (see
Figure 7).
Pilot-operated relief valves are available
for use in liquid and vapor services. Since
the main valve and pilot contain nonmetallic components, process temperature and
fluid compatibility can limit their use. In addition, fluid characteristics such as
susceptibility to polymerization or fouling,
viscosity, the presence of solids, and corrosiveness may affect pilot reliability. The
manufacturer should be consulted to ensure that the proposed application is
compatible with available valves.
2.4 Rupture Disk Devices
The remainder of Section 2 provides definitions, descriptions, and operational
characteristics of rupture disk devices.
Specific terms and uses are covered within the applicable sections of text and
accompanying illustrations (see Figures
11-17).
Set Spring
Adjustment Spring
Sense Diaphragm
Boost Diaphragm
Sense Cavity
Spindle Seat Diaphragm
Boost Cavity
Pilot Exhaust
Optional Pilot Filter
Variable Orifice
Outlet
Main Valve Diaphragm
Main Valve Seat
Dome
Inlet
Internal Pressure Pickup
Figure 18 – Typical Effects of Superimposed Back Pressure on the
Opening Pressure of Conventional Pressure Relief Valves
Spring Bonnet Vented To Atmosphere
Spring Bonnet Vented To Valve
Discharge
SpringBonnet
Vented
Spring-Bonnet
Spring Fs
The pilot valve that operates the main
valve can be either a pop action or modulating action pilot. Figure 23 shows the
action of the pop pilot; it shows that pilot
operation causes the main valve to lift fully. Figure 24 shows the action of the
modulating pilot; it shows that pilot operation opens the main valve only enough to
satisfy the required relieving capacity.
Figure 10 – Low-Pressure Pilot Operated Valve (Diaphragm Type)
Spring Fs
the diaphragm at set pressure, and reload
the diaphragm once the process pressure
returns to normal. As with the piston valve,
the seating force increases proportionally
with the operating pressure because of
the differential exposed area of the
diaphragm.
Disk
Guide
PB
PB
PB
PB
PB
Disk
Disk
PB
Piston Vent
PB
PB
PV
PV
Ap = AN
Back Pressure Decreases Set Pressure
Back Pressure Increases Set Pressure
PVAN = FS-PB (AD-AN)
PVAN = FS+PBAN
AD>AN
AD = disk area.
AN = nozzle seat area.
FS = spring force.
PV = vessel pressure in pounds per square inch gauge.
PB = superimposed back pressure, in pounds per square in gauge.
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Figure 20 – Theoretical Performance for a Nozzle Discharging a Gas That
Has a Specific Heat Ratio of 1.3
100
Figure 19 – Typical Effects of Builtup Back Pressure on the Capacity
of Conventional Pressure Relief
Valves
90
70
Percent (C1/C2) x 100
Theoretical nozzle flow
60
50
40
30
20
10
0
▲
▲
▲
▲
▲
▲
0
10
20
30
40
50
Percent =
▲
▲
▲
▲
▲
60
70
80
90
100
PB
PS + PO
Conventional pressure relief valve with spring bonnet vented to valve discharge
Valve
(stable)
90
80
70
60
50
40
30
P´
PS
x 100
P´ less than
overpressure
Balanced Disk and Vented
Bellows Type
SpringBonnet Vent
Fs
Fs
SpringBonnet Vent
PB
Piston
Piston Vent
PB
PB
Bellows Vent
PB
Disk
Disk
PB
Vent
PB
PV
AB = effective bellows area
AD = disk area
AN = nozzle seat area
AP = piston area (top)
FS = spring force
PV = vessel gauge pressure
Vented
Bellows
Ap = AN
PV
AB = AN
PB = superimposed back pressure in pounds
per square inch gauge
PS = set pressure, in pounds per square inch
gauge
Note: In this figure, P V = PS; (P V)(AN) = FS
(typical); and PS = FS/AN.
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designs and specifications without notice.
P´greater than
overpressure
C1 = capacity with back pressure
C2 = capacity with zero back pressure
P´ = built-up back pressure
PS = set pressure
Figure 21 – Typical Effects of Back Pressure on the Set Pressure of
Balanced Pressure Relief Valves
Balanced Disk and Vented Piston Type
Valve
(flutter chatter)
100
Percent (C1/C2) x 100
C1 = capacity with back
pressure
C2 = capacity with zero
back pressure
PB = back pressure, in
pounds per square
inch absolute
PS = set pressure, in
pounds per square
inch absolute
PO = overpressure, in
pounds per square
inch
80
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Pressure Relieving Devices in Refineries
Figure 22 – Typical Relationship
Between Lift of Disk in a Pressure
Relief Valve and Vessel Pressure
100
Lift of disk, percent
0
Closing
100
Lift of disk, percent
B
Figure 23 – Typical Relationship
Between Lift of Disk in a PopAction Pilot Operated Relief Valve
and Vessel Pressure
Blowdown
Set
pressure
0
Overpressure
Closing
Blowdown
Overpressure
Maximum
relieving
pressure
Set
pressure
Maximum
relieving
pressure
Figure 24 – Typical Relationship
Between Lift of Disk in a
Modulating-Action Pilot Operated
Relief Valve and Vessel Pressure
Lift of disk, percent
100
0
Closing
Blowdown
Set
pressure
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Overpressure
Maximum
relieving
pressure
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4.1 Determination of Relief
Requirements
To establish the size of a pressure relief
device for any application, the designer
must first determine the conditions for
which overpressure protection may be
required. Reasonable care should be
exercised in establishing the various
contingencies that could result in overpressure.
The contingencies that may cause overpressure must be evaluated in terms of
the pressures generated and the rates at
which fluids must be relieved. The
process flow diagram, material balance,
piping and instrument diagrams, equipment specification sheets, and design
basis for the facility are needed to calculate the individual relieving rates for each
pressure relieving device. Process equipment vendor data is also helpful if
available.
Appendix D provides relieving flow rates
for fire conditions. Table 1 lists a number
of common operational conditions for
which overpressure protection may be required. This list is by no means complete;
each plant may have unique features that
must be considered in addition to those
listed in Table 1. (See API Recommended
Practice 521 for a detailed discussion of
relief requirements.)
Pressure relief valves may be sized using
the equations presented in 4.3 through 4.5
as appropriate for vapors, gases, or liquids. These equations are used to
calculate the effective nozzle area necessary to achieve a required flow rate
through the valve. A valve is then chosen
for the application that has an effective
area equal to or greater than the calculated required effective area.
The effective areas and assumed discharge coefficient, Kd = 0.975, are
generally different from actual orifice
areas and discharge coefficients that are
used to determine certified valve capacities. However, effective areas calculated
using the equations in 4.3 through 4.5 will
result in the selection of valves with certified capacities that equal or exceed the
required capacities.
The effective-area concept allows for the
selection of valve size independent of the
manufacturer. Standard effective orifice
areas and corresponding letter designations may be found in API Standard 526.
4.2 Relieving Pressure
4.2.1 General
Relieving pressure, shown in P1 in the
various sizing equations, is the inlet pressure of the relief device at relieving
conditions. The relieving pressure is the
total of set pressure plus overpressure
plus atmospheric pressure. The examples
cited in this section for the determination
of relieving pressure refer to pressure relief valves; however, they are also
applicable to rupture disk devices. (See
Figures 1 and 25 for pressure-level relationships for these types of devices.)
Notes
1. The discussion in this section generally
cites the ASME Code as the applicable
code. Unless stated otherwise, citations
refer only to Section VIII of the ASME
Code.The designer should be aware of
revisions to the ASME Code. If pertinent
revisions occur, the discussion in this section should be adjusted accordingly by
the designer. Adjustments may also be required by the designer if other (non-ASME)
codes apply.
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126
The allowable overpressure is established
from the accumulation permitted by the
applicable code. The allowable overpressure may vary for different applications
depending on the relationship of the set
pressure to the maximum allowable working pressure of the vessel or system that
is protected. Allowable overpressure is the
same as allowable accumulation only
when the set pressure is equal to the
maximum allowable working pressure.1
Sections 4.2.2 through 4.2.4 discuss methods of determining the relieving pressure
for pressure relief valves in gas and vapor
service. Standard atmospheric pressure
(14.7 pounds per square inch absolute) is
used for gauge/absolute pressure conversion in these sections. For design,
barometric pressure corresponding to site
elevation should be used.
Relieving pressure for pressure relief
valves in liquid service is determined in a
manner similar to that used for vapor service except that the relieving pressure is
expressed in gauge rather than absolute
units. In the case of ASME-application
liquid service valves (that is, for the protection of a liquid-full vessel), maximum
accumulated pressure is limited to 110%
of the maximum allowable working pressure for operating contingencies – the
same constraint as for vapor service. In
the case of non-ASME-application liquid
service valves (that is, for protection of
piping without vessels included), 25%
overpressure is generally specified.
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Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
Table 2 summarizes the maximum accumulation and set pressure for pressure
relief valves specified in accordance with
the ASME Code.
Table 4 shows an example determination
of relieving pressure for a multiple-valve
installation in which the set pressure of
the first valve is equal to the maximum allowable working pressure of the vessel,
and the set pressure of the additional
valve is 105% of the vessel’s maximum allowable working pressure.
4.2.2 Operating Contingencies
4.2.2.1 Single-Valve Installation
In accordance with the requirements of
the ASME Code, accumulated pressure
shall be limited to 110% of the maximum
allowable working pressure in vessels that
are protected by a single pressure relief
valve sized for operating (nonfire) contingencies. The set pressure of the valve
shall not exceed the maximum allowable
working pressure.2
4.2.3 Fire Contingencies
4.2.3.1 General
In accordance with the requirements of the
ASME Code, accumulated pressure shall
be limited to 121% of the maximum allowable working pressure in vessels that are
protected by valves sized for fire contingencies. This applies to single-, multiple-,
and supplemental-valve installations.
Table 3 shows an example determination
of relieving pressure for a single valve
whose set pressure is less than or equal
to the vessel’s maximum allowable working pressure.
Single or multiple valves sized for fire may
also be utilized for relieving requirements
attributed to secondary operating (nonfire)
contingencies, if applicable, provided that
the constraint of 110% (of the maximum
allowable working pressure) accumulated
pressure for nonfire contingencies is observed.
4.2.2.2 Multiple-Valve Installation
A multiple-valve installation requires the
combined capacity of two or more pressure relief valves to alleviate a given
overpressure contingency.
4.2.3.2 Single-Valve Installation
Where a vessel is protected by a single
valve sized for fire, the set pressure shall
not exceed the maximum allowable working pressure.
In accordance with the requirements of
the ASME Code, accumulated pressure
shall be limited to 116% of the maximum
allowable working pressure in vessels that
are protected by multiple valves sized for
operating (nonfire) contingencies. The set
pressure of the first valve shall not exceed
the maximum allowable working pressure.
The set pressure of the additional valve or
valves shall not exceed 105% of the maximum allowable working pressure.3
Table 5 shows an example determination
of relieving pressure for a single valve
whose set pressure is less than or equal
to the vessel’s maximum allowable working pressure.
4.2.3.3 Multiple-Valve Installation
A multiple-valve installation requires the
combined capacity of two or more valves
to alleviate overpressure from a fire. The
set pressure of the first valve to open shall
not exceed the maximum allowable working pressure. The set pressure of the last
valve to open shall not exceed 105% of
the maximum allowable working pressure.
Table 6 shows an example determination
of relieving pressure for a multiple-valve
installation in which the set pressure of
the first valve is equal to the vessel’s
maximum allowable working pressure,
and the set pressure of the additional
valve is 105% of the vessel’s maximum
allowable working pressure.
4.2.3.4 Supplemental-Valve Installation
A supplemental-valve installation provides
relieving capacity for an additional hazard
created by exposure to fire or other unexpected sources of external heat. The set
pressure of a supplemental valve for fire
shall not exceed 110% of the maximum allowable working pressure.
Supplemental valves are used only in
addition to valves sized for operating
(nonfire) contingencies.
Table 7 shows an example determination of
relieving pressure for a supplemental-valve
installation in which the set pressure of the
first (nonfire) valve does not exceed the
vessel’s maximum allowable working pressure (see 4.2.1 for determination of
relieving pressure), and the set pressure of
the supplemental valve in 110% of the vessel’s maximum allowable working pressure.
Table 2
Set Pressure and Accumulation Limits for Pressure Relief Valves4
Contingency
Single-Valve Installations
Multiple-Valve Installations
Set
Pressure
(percent)
Maximum
Accumulated
Pressure
(percent)
Set
Pressure
(percent)
Maximum
Accumulated
Pressure
(percent)
100
110
100
116
–
–
105
116
100
121
100
121
Additional valve(s)
–
–
105
121
Supplemental valve
–
–
110
121
Nonfire only
First Valve
Additional Valve(s)
Notes
2. Allowable accumulation is 3 pounds per
square inch when the maximum allowable
working pressure is between 15 and 30
pounds per square inch gauge.
3. Allowable accumulation is 4 pounds per
square inch when the maximum allowable
working pressure is between 15 and 25
pounds per square inch gauge.
4. All values are percentages of the maximum
allowable working pressure.
Fire only
First Valve
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Table 3
Table 4
Example Determination of
Relieving Pressure for a Single
Valve (Operating Contingencies)
Characteristic
Value
Characteristic
Valve Set Pressure Less Than MAWP
Table 5
Example Determination of
Relieving Pressure for a MultipleValve Installation (Operating
Contingencies)
Value
Example Determination of
Relieving Pressure for a Single
Valve (Fire Contingencies)
Characteristic
Value
Valve Set Pressure Less Than MAWP
Protected vessel MAWP, psig
100
First Valve (Set Pressure Equal to MAWP)
Protected vessel MAWP, psig
100
Maximum accumulated pressure, psig
110
Protected vessel MAWP, psig
100
Maximum accumulated pressure, psig
121
116
Valve set pressure, psig
90
100
Allowable overpressure, psi
31
Allowable overpressure, psi
16
Relieving pressure, P1, psia
135.7
Relieving pressure, P1, psia
130.7
Valve set pressure, psig
90
Maximum accumulated pressure, psig
Allowable overpressure, psig
20
Valve set pressure, psig
Relieving pressure, P1, psia
124.7
Valve Set Equal to MAWP
Protected vessel MAWP, psig
100
Maximum accumulated pressure, psig
110
Valve set pressure, psig
100
Allowable overpressure, psi
10
Relieving pressure, P1, psia
124.7
Additional Valve (Set Pressure Equal to
105% of MAWP)
Protected vessel MAWP, psig
100
Maximum accumulated pressure, psig
116
Valve set pressure, psig
105
Allowable overpressure, psi
11
Relieving pressure, P1, psia
130.7
Table 7
Table 6
Example Determination of
Relieving Pressure for a MultipleValve Installation (Fire
Contingencies)
Example Determination of
Relieving Pressure for a
Supplemental Valve (Fire
Contingencies)
Characteristic
Value
Characteristic
Protected vessel MAWP, psig
100
Supplemental Valve (Set Pressure Equal to
110% of MAWP)
Maximum accumulated pressure, psig
121
Valve set pressure, psig
100
First Valve (Set Pressure Equal to MAWP)
Allowable overpressure, psig
21
Relieving pressure, P1, psia
135.7
Additional Valve (Set Pressure Equal to
105% of MAWP)
Protected vessel MAWP, psig
100
Maximum accumulated pressure, psig
121
Valve set pressure, psig
105
Allowable overpressure, psig
16
Relieving pressure, P1, psia
135.7
Protected vessel MAWP, psig
Value
100
Maximum accumulated pressure, psig
121
Valve set pressure, psig
110
Allowable overpressure, psig
11
Relieving pressure, P1, psia
135.7
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Valve Set Pressure Equal to MAWP
Protected vessel MAWP, psig
100
Maximum accumulated pressure, psig
116
Valve set pressure, psig
100
Allowable overpressure, psi
21
Relieving pressure, P1, psia
135.7
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4.2.4 Steam Service
Where:
Where:
Valves for pressure vessels in steam service, excluding boilers designed in
accordance with Section I of the ASME
Code, should be specified as discussed
above, depending on the contingency.
Pcf = critical flow throat pressure, in
pounds per square inch absolute.
A = required effective discharge area of
the valve, in square inches (see
1.2.2).
4.3 Sizing for Gas or Vapor Relief
4.3.1 Critical Flow Behavior
If a compressible gas is expanded across
a nozzle, an orifice, or the end of a pipe,
its velocity and specific volume increase
with decreasing downstream pressure.
For a given set of upstream conditions
(using the example of a nozzle), the mass
rate of flow through the nozzle will increase until a limiting velocity is reached
in the throat. It can be shown that the limiting velocity is the velocity of sound in the
flowing media at that location. The flow
rate that corresponds to the limiting velocity is known as the critical flow rate.
The absolute pressure ratio of the pressure in the throat at sonic velocity (Pcf) to
the inlet pressure (P1) is called the critical
pressure ratio. Pcf is known as the critical
flow pressure.
Under critical flow conditions, the actual
pressure in the throat cannot fall below
the critical flow pressure even if a much
lower pressure exists downstream. At critical flow, the expansion from throat
pressure to downstream pressure takes
place irreversibly with the energy dissipated in turbulence into the surrounding fluid.
The critical flow pressure in absolute units
may be estimated using the ideal gas relationship in Equation 1:
Pcf
––– =
P1
[ ]
2
––––
k+1
k
(k - 1)
(1)
P1 = upstream relieving pressure, in
pounds per square inch absolute.
k=
ratio of specific heats for any ideal
gas.
The sizing equations for pressure relief
valves in vapor or gas service fall into two
general categories depending on whether
the flow is critical or subcritical. If the pressure downstream of the throat is less than
or equal to the critical flow pressure, Pcf,
then critical flow will occur, and the procedures in 4.3.2 should be applied. If the
downstream pressure exceeds the critical
flow pressure, Pcf, then subcritical flow will
occur, and the procedures in 4.3.3 should
be applied. (See Table 8 for typical critical
flow pressure ratio values.)
4.3.2 Sizing for Critical Flow
4.3.2.1 General
Pressure relief valves in gas or vapor
service that operate under critical flow
conditions (see 4.3.1) may be sized using
Equations 2 – 4. Each of the equations
may be used to calculate the effective
discharge area, A, required to achieve
a required flow rate through a pressure
relief valve. A valve that has an effective
discharge area equal to or greater than
the calculated value of A is then chosen
for the application.
W
A = ––––––––
CKdP1Kb
––––––
TZ
–––
M
√
(2)
–––––
V √ TZM
A = ––––––––––––
6.32 CKdP1Kb
(3)
–––––
V √ TZG
A = –––––––––––––
1.175 CKdP1Kb
(4)
W = required flow through the valve, in
pounds per hour.
C = coefficient determined from an expression of the ratio of the specific
heats of the gas or vapor at standard
conditions. This can be obtained from
Figure 26 or Table 9.
Kd = effective coefficient of discharge =
0.975 for use in Equations 2 – 4.
P1 = upstream relieving pressure, in
pounds per square inch absolute.
This is the set pressure plus the allowable overpressure (see 4.2) plus
atmospheric pressure.
Kb = capacity correction factor due to back
pressure. This can be obtained from
the manufacturer’s literature or
estimated from Figure 27. The backpressure correction factor applies to
balanced-bellows valves only.5
T = relieving temperature of the inlet gas
or vapor, in degrees Rankine (degrees Fahrenheit + 460).
Z = compressibility factor for the deviation
of the actual gas from a perfect gas, a
ratio evaluated at inlet conditions.
M = molecular weight of the gas or vapor.
Various handbooks carry tables of
molecular weights of materials, but
the composition of flowing gas or vapor is seldom the same as that listed
in tables. This value should be obtained from the process data. Table 8
lists values for some common fluids.
V = required flow through the valve, in
standard cubic feet per minute at
14.7 pounds per square inch absolute and 60°F.
G = specific gravity of gas referred to air
= 1.00 for air at 14.7 pounds per
square inch absolute and 60°F.
Notes
5. See 4.3.3 for applications that involve superimposed back pressure of a magnitude
that will cause subcritical flow.
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The value of the coefficient C can be evaluated from the expression of the ratio of
the specific heats of the gas or vapor as
shown in Figure 26.
Figure 26 - Curve for Evaluating Coefficient C in the Flow Equation From
the Specific Heat Ratio Assuming Ideal Gas Behavior
400
The ratio of specific heats of any ideal gas
and possibly the ratio of specific heats of
a diatomic actual gas can be found in any
acceptable reference work.
380
Coefficient, C
Table 9 complements Figure 26 where
k = Cp/Cv. When k cannot be determined,
it is suggested that C = 315.
While ideal gas law behavior is generally
acceptable for the majority of refinery applications, Appendix E should be referred
to for unusual situations in which deviation
from ideal behavior is significant.
360
C = 520
k
k+1
k+2
( (
2
k+1
340
4.3.2.2 Example
In this example, the following relief
requirements are given:
320
▲
1.0
a. Required hydrocarbon vapor flow, W,
caused by an operational upset, of
53,500 pounds per hour.
▲
1.2
▲
1.4
▲
1.6
▲
1.8
▲
2.0
Specific heat ratio, k = CP/CV
b. Molecular weight of hydrocarbon
vapor [a mixture of butane (C4) and
pentane (C5)], M, of 65.
c. Relief temperature, T, of 627°R
(167°F).
d. Relief valve set at 75 pounds per
square inch gauge, the design pressure
of the equipment.
e. Back pressure of 0 pounds per square
inch gauge.
In this example, the following data are
derived:
a. Permitted accumulation of 10%.
b. Relieving pressure, P1, of 75 x 1.1 +
14.7 = 97.2 pounds per square inch
absolute.
c. Calculated compressibility, Z, of 0.84.
(If a calculated compressibility is not
available, Z = 1.0 should be used.)
The size of a single pressure relief valve
is derived from Equation 2 as follows:
d. Critical back pressure (from Table 8) of
97.2 x 0.59 = 57.3 pounds per square
inch absolute (42.6 pounds per square
inch gauge).6
53,500
A = –––––––––––––––
326 x 0.975 x 97.2
e. Cp/Cv = k (from Table 8) of 1.09. From
Table 9, C = 326.
f. Capacity correction due to back pressure, Kb, of 1.0.
√
in2
See API Standard 526, which also provides a purchase specification sheet for
flanged steel safety relief valves (see
Figure 28).
Select a ‘P’ letter orifice size (6.38 in2).
Notes
6. Since the back pressure (0 pounds per
square inch gauge) is less than the critical
back pressure (42.6 pounds per square
inch gauge), the relief valve setting is based
on the critical flow equation (see Equation 2
and 4.3.1 and 4.3.2).
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
= 4.93
––––––––––
627 x 0.84
–––––––––
65
130
Anderson Greenwood Pressure Relief Valves
Technical Manual
API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
Table 8
Properties of Gases
Gas
Molecular
Weight
Methane
16.04
Specific
Critical Flow
Specific
Critical Constants
Condensation Flammability References
Heat Ratio
Pressure
Gravity at Pressure Temperature Temperature
Limits
Ratio at
at 60°F
(psia)
(°F)
1 Atmosphere (volume
(k = Cp/Cv)
at 60°F
at 60°F
and 1
(°F)
percent
and 1
and 1
Atmosphere
in air
Atmosphere Atmosphere
mixture)
1.31
0.54
0.300
667
-117
-259
5.0-15.0
1
Ethane
30.07
1.19
0.57
0.356
708
90
-127
2.9-13.0
1
Ethylene
28.05
1.25
0.56
0.139
731
49
-155
2.7-36.0
1
Propane
44.10
1.13
0.58
0.507
615
206
-44
2.0-9.5
1
Proylene
42.08
1.15
0.57
0.518
672
198
-54
2.0-10.6
2, 3
Isobutane
58.12
1.10
0.59
0.563
528
274
11
1.8-8.5
1
n-Butane
58.12
1.09
0.59
0.584
549
306
31
1.5-9.0
1
1-Butane
56.11
1.11
0.58
0.600
586
296
21
1.6-9.3
2, 3
Isopentane
72.15
–
–
0.625
490
369
82
1.3-8.0
1
n-Pentane
72.15
–
–
0.631
488
386
97
1.4-8.3
1
1-Pentane
70.13
–
–
0.646
510
377
86
1.5-8.7
1
n-Hexane
86.18
–
–
0.664
437
454
156
1.1-7.7
1
Benzene
78.11
–
–
0.882
710
552
176
1.4-7.1
2, 3
n-Heptane
100.20
–
–
0.688
397
513
209
1.0-7.0
1
Toluene
92.14
–
–
0.874
596
606
231
1.2-7.1
2, 3
n-Octane
114.23
–
–
0.707
361
564
258
0.8-6.5
1
n-Nonane
128.26
–
–
0.722
332
611
303
0.7-5.6
1
n-Decane
142.28
–
–
0.734
305
653
345
0.7-5.4
1
Air
28.96
1.40
0.53
0.875
547
-221
-318
–
2, 3
Ammonia
17.03
1.31
0.54
0.616
1636
271
-28
16.0-25.0
2, 3
Carbon dioxide
44.01
1.29
0.55
0.818
1071
88
-109
–
2, 3
2.02
1.41
0.53
–
190
-400
-423
4.0-75.0
2, 3
Hydrogen sulfide
34.08
1.32
0.54
0.801
1300
213
-77
4.3-45.5
2, 3
Sulfur dioxide
64.06
1.27
0.55
1.394
1143
316
14
–
2, 3
Steam
18.02
–
–
1.000
3199
705
212
–
2, 3
Hydrogen
Estimated
References
1. “Physical Constants of Hydrocarbons C1 to
C10,” ASTM Special Technical Publication
No. 109A, Philadelphia, Pa., 1963.
2. “International – Critical Tables,” McGraw-Hill
Book Co., Inc., New York.
3. “Engineering Data Book,” Gas Processors
Suppliers Association, 1977.
4. API Technical Data Book–Petroleum
Refining, Fifth edition.
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designs and specifications without notice.
131
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API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
4.3.3 Sizing for Subcritical Flow:
Gas or Vapor Other Than Steam
4.3.3.1 General
When the ratio of back pressure to inlet
pressure exceeds the critical pressure
ratio Pcf/P1, the flow through the pressure
relief valve is subcritical (see 4.3.1).
Equations 5 – 7 may be used to calculate
the required effective discharge area for a
conventional relief valve that has its spring
setting adjusted to compensate for superimposed back pressure and for sizing a
pilot-operated relief valve.7
W
A = ––––––––
735 F2Kd
–––––––––––––
ZT
––––––––––––
MP1 (P1 - P2)
√
V
A = –––––––––––
4645.2 F2Kd
V
A = –––––––––––
863.63 F2Kd
Where:
(5)
W = required flow through the valve, in
pounds per hour.
–––––––––––
ZTM
––––––––––
P1 (P1 - P2)
(6)
–––––––––––
ZTG
––––––––––
P1 (P1 - P2)
(7)
√
√
F2 = coefficient of subcritical flow (see
Figure 28 for values)
=
–––––––––––––––––––––––
k
1 - r (k-1)k
–––– (r)2/k –––––––
k-1
1-r
√(
)
[
]
k = ratio of the specific heats.
r = ratio of back pressure to upstream
relieving pressure, P2/P1.
Table 9
Values of Coefficient C
k
C
k
C
k
C
k
C
1.01
317a
1.31
348
1.61
373
1.91
395
1.02
318
1.32
349
1.62
374
1.92
395
1.03
319
1.33
350
1.63
375
1.93
396
1.04
320
1.34
351
1.64
376
1.94
397
1.05
321
1.35
352
1.65
376
1.95
397
1.06
322
1.36
353
1.66
377
1.96
398
1.07
323
1.37
353
1.67
378
1.97
398
1.08
325
1.38
354
1.68
379
1.98
399
1.09
326
1.39
355
1.69
379
1.99
400
1.10
327
1.40
356
1.70
380
2.00
400
1.11
328
1.41
357
1.71
381
–
–
1.12
329
1.42
358
1.72
382
–
–
1.13
330
1.43
359
1.73
382
–
–
1.14
331
1.44
360
1.74
383
–
–
1.15
332
1.45
360
1.75
384
–
–
1.16
333
1.46
361
1.76
384
–
–
1.17
334
1.47
362
1.77
385
–
–
1.18
335
1.48
363
1.78
386
–
–
1.19
336
1.49
364
1.79
386
–
–
1.20
337
1.50
365
1.80
387
–
–
1.21
338
1.51
365
1.81
388
–
–
1.22
339
1.52
366
1.82
389
–
–
1.24
341
1.54
368
1.84
390
–
–
1.25
342
1.55
369
1.85
391
–
–
1.26
343
1.56
369
1.86
391
–
–
1.27
344
1.57
370
1.87
392
–
–
1.28
345
1.58
371
1.88
393
–
–
1.29
346
1.59
372
1.89
393
–
–
130
347
1.60
373
1.90
394
–
–
a Interpolated
A = required effective discharge area of
the valve, in square inches (see 1.2.2).
value, since C becomes indeterminate as k approaches 1.00.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
132
Kd = effective coefficient of discharge
= 0.975 for use in Equations 5 –7.
Z = compressibility factor for the deviation of the actual gas from a perfect
gas, a factor evaluated at relieving inlet conditions.
T = relieving temperature of the inlet gas
or vapor, in degrees Rankine (degrees Fahrenheit + 460).
M = molecular weight of the gas or vapor.
Various handbooks carry tables of
molecular weights of materials, but
the composition of the flowing gas or
vapor is seldom the same as that listed in the tables. This value should be
obtained from the process data. Table
8 lists values for some common fluids.
P1 = upstream relieving pressure, in
pounds per square inch absolute.
This is the set pressure plus the allowable overpressure (see 4.2) plus
atmospheric pressure, in pounds per
square inch absolute.
P2 = back pressure, in pounds per square
inch absolute.
V = required flow through the valve, in
standard cubic feet per minute at
14.7 pounds per square inch absolute and 60°F.
G = specific gravity of gas referred to air
= 1.00 for air at 14.7 pounds per
square inch absolute and 60°F.
Note
7. Balanced-bellows relief valves that operate
in the subcritical region should be sized using Equations 2-4. The back pressure
correction factor for this application should
be obtained from the valve manufacturer.
Anderson Greenwood Pressure Relief Valves
Technical Manual
API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
Figure 27 – Back Pressure Sizing Factor, Kb, for Balanced-Bellows Pressure Relief Valves (Vapors and Gases)
1.00
20%
overp
ressu
Kb = C1/C2
0.90
re
C1 = capacity with back
pressure.
C2 = rated capacity with
zero back pressure.
PB = back pressure, in
pounds per square
inch gauge.
PS = set pressure, in
pounds per square
inch gauge.
10
%
0.80
ov
er
pr
0.70
es
su
re
0.60
0.50
▲
0
▲
5
▲
10
▲
15
▲
20
▲
25
▲
35
▲
30
▲
45
▲
40
▲
50
Percent of gauge back pressure = PB/PS x 100
Note
make is known, the manufacturer should be consulted for the correction factor. These curves are
for set pressures of 50 pounds per square inch
gauge and above. They are limited to back pressure below critical flow pressure for a given set
pressure. For subcritical flow back pressures
below 50 pounds per square inch gauge, the
manufacturer must be consulted for values of Kb.
Figure 28 – Values of F2 for Subcritical Flow
1.0
0.9
F2
The curves above represent a compromise of the
values recommended by a number of relief valve
manufacturers and may be used when the make
of the valve or the actual critical flow pressure
point for the vapor or gas is unknown. When the
0.8
0.7
0.6
▲
0.4
k=
1.8
k=
1.6
k=
▲
0.5
1.4
k=
1.2
k=
1.0
▲
0.6
Critical flow line
▲
0.7
▲
0.8
▲
0.9
▲
1.0
r = P2/P1
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designs and specifications without notice.
133
Anderson Greenwood Pressure Relief Valves
Technical Manual
API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
See API standard 526, which also provides a purchase specification sheet for
flanged steel safety relief valves.
Select a ‘P’ letter orifice size (6.38 in2).
e. Constant back pressure of 55 pounds
per square inch gauge. The spring setting of the valve should be adjusted
according to the amount of constant
back pressure obtained.
4.3.4 Alternate Sizing Procedure
for Subcritical Flow
In this example, the following data are
derived:
4.3.4.1 General
Critical flow Equations may be used to
calculate the required discharge area of a
pressure relief valve used in subcritical
service. The area obtained using this sizing procedure is identical to the area
obtained using the subcritical flow equations. (The capacity correction factor due
to back pressure is derived by setting the
subcritical flow equation equal to the critical flow equation and algebraically solving
for Kb.) This alternate sizing procedure allows the designer to use the familiar
critical flow equation to calculate the same
area obtained with the subcritical flow
equation. A graphical presentation of the
capacity correction factor, Kb, is given in
Figure 30 on page 129. It should be noted
that this correction factor is used only for
the sizing of conventional (nonbalanced)
relief valves that have their spring settings
adjusted to compensate for the superimposed back pressure. The correction factor
should not be used to size balanced-type
valves.
a. Permitted accumulation of 10 percent.
b. Relieving pressure, P1, of 75 x 1.1 + 14.7
= 97.2 pounds per square inch absolute.
c. Calculated compressibility, Z, of 0.84. (If
a calculated compressibility is not available, Z = 1.0 should be used.)
d. Critical back pressure (from Table 8) of
97.2 x 0.59 = 57.3 pounds per square
inch absolute (42.6 pounds per square
inch gauge).8
4.4 Sizing for Steam Relief
4.4.1 General
Pressure relief valves in steam service
may be sized using Equation 8.
W
A = ––––––––––––––
51.5 P1KdKNKSH
(8)
Where:
A = required effective discharge area,
in square inches.
W = required flow rate, in pounds per
hour.
e. Built-up back pressure of 0.10 x 75 =
7.5 pounds per square inch.
P1 = upstream relieving pressure, in
pounds per square inch absolute.
This is the set pressure plus the
allowable overpressure plus atmospheric pressure, in pounds per
square inch absolute.
f. Total back pressure of 55 + 7.5 + 14.7 =
77.2 pounds per square inch absolute.
Kd = effective coefficient of discharge
= 0.975 for use in Equation 8.
g. Cp/Cv = k of 1.09.
KN = correction factor for Napier equation
(see Reference 1)
h. P2/P1 = 77.2 / 97.2 = 0.794.
i. Back pressure correction factor, Kb, of
0.88 (from Figure 30 on page 129).
= 1 where P1 ≤ 1515 pounds per
square inch absolute
j. Coefficient determined from an expression of the ratio of the specific heats of
the gas or vapor at standard conditions,
C, of 326.
= (0.1906P1 – 1000) /(0.2292P1 – 1061)
where P1 > 1515 pounds per square
inch absolute and ≤ 3215 pounds
per square inch absolute.
4.3.4.2 Example
In this example, the following relief requirements are given:
The size of the relief valve is derived from
Equation 2 as follows: 9
a. Required hydrocarbon vapor flow, W,
caused by an operational upset, of
53,500 pounds per hour.
53,500
A = ––––––––––––––––––
326(0.975)(97.2)(0.88)
KSH = superheat steam correction factor.
This can be obtained from Table 10
on page 127. For saturated steam
at any pressure, KSH = 1.0.
b. Molecular weight of hydrocarbon vapor
[a mixture of butane (C4) and pentane
(C5), M, of 65.
–––––––––
627(0.84)
––––––––
65
√
W = saturated steam at 153,500 pounds
per hour at 1600 pounds per square
inch gauge set pressure with 10%
accumulation.
c. Relief temperature, T, of 627°R (167°F).
d. Relief valve set at 75 pounds per
square inch gauge, the design pressure
of the equipment.
Notes
8. Since the back pressure (55 pounds per
square inch gauge) is greater than the critical
back pressure (42.6 pounds per square inch
gauge), the sizing of the relief valve is based
on subcritical flow. The back pressure correction factor, Kb, should be determined using
the critical flow formulas (see Equations 2–4).
4.4.2 Example
In this example, the following relief requirements are given:
= 5.60 in2
9. This area requirement is the same as that obtained using the subcritical flow equation (see
Equation 5).
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
134
Anderson Greenwood Pressure Relief Valves
Technical Manual
API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
Table 10
Superheat Correction Factors, KSH
Set Pressure
(pounds per
in2 gauge)
Temperature (degrees Fahrenheit)
300
400
500
600
700
800
900
1000
1100
1200
15
1.00
0.98
0.93
0.88
0.84
0.80
0.77
0.74
0.72
0.70
20
1.00
0.98
0.93
0.88
0.84
0.80
0.77
0.74
0.72
0.70
40
1.00
0.99
0.93
0.88
0.84
0.81
0.77
0.74
0.72
0.70
60
1.00
0.99
0.93
0.88
0.84
0.81
0.77
0.75
0.72
0.70
80
1.00
0.99
0.93
0.88
0.84
0.81
0.77
0.75
0.72
0.70
100
1.00
0.99
0.94
0.89
0.84
0.81
0.77
0.75
0.72
0.70
120
1.00
0.99
0.94
0.89
0.84
0.81
0.78
0.75
0.72
0.70
140
1.00
0.99
0.94
0.89
0.85
0.81
0.78
0.75
0.72
0.70
160
1.00
0.99
0.94
0.89
0.85
0.81
0.78
0.75
0.72
0.70
180
1.00
0.99
0.94
0.89
0.85
0.81
0.78
0.75
0.72
0.70
200
1.00
0.99
0.95
0.89
0.85
0.81
0.78
0.75
0.72
0.70
220
1.00
0.99
0.95
0.89
0.85
0.81
0.78
0.75
0.72
0.70
240
–
1.00
0.95
0.90
0.85
0.81
0.78
0.75
0.72
0.70
260
–
1.00
0.95
0.90
0.85
0.81
0.78
0.75
0.72
0.70
280
–
1.00
0.96
0.90
0.85
0.81
0.78
0.75
0.72
0.70
300
–
1.00
0.96
0.90
0.85
0.81
0.78
0.75
0.72
0.70
350
–
1.00
0.96
0.90
0.86
0.82
0.78
0.75
0.72
0.70
400
–
1.00
0.96
0.91
0.86
0.82
0.78
0.75
0.72
0.70
500
–
1.00
0.96
0.92
0.86
0.82
0.78
0.75
0.73
0.70
600
–
1.00
0.97
0.92
0.87
0.82
0.79
0.75
0.73
0.70
800
–
–
1.00
0.95
0.88
0.83
0.79
0.76
0.73
0.70
1000
–
–
1.00
0.96
0.89
0.84
0.78
0.76
0.73
0.71
1250
–
–
1.00
0.97
0.91
0.85
0.80
0.77
0.74
0.71
1500
–
–
–
1.00
0.93
0.86
0.81
0.77
0.74
0.71
1750
–
–
–
1.00
0.94
0.86
0.81
0.77
0.73
0.70
2000
–
–
–
1.00
0.95
0.86
0.80
0.76
0.72
0.69
2500
–
–
–
1.00
0.95
0.85
0.78
0.73
0.69
0.66
3000
–
–
–
–
1.00
0.82
0.74
0.69
0.65
0.62
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
135
Anderson Greenwood Pressure Relief Valves
Technical Manual
API - RP 520 Part I (July 1991) - Sizing, Selection
Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
Figure 29 - Constant Back Pressure Sizing Factor, Kb, For Conventional
Safety Relief Valves (Vapors and Gases Only)
100
90
C1 = capacity with back pressure.
735F2 l - r
C
70
Kb = C1/C2 =
80
40
C2 = rated capacity with zero back pressure.
k = 1.1
k = 1.3
k = 1.5
k = 1.7
60
Exchange
50
30
20
10
0
▲
0
▲
10
▲
20
▲
30
▲
40
▲
50
Percent of absolute back pressure
Set overpressure (MAWP)
= 100 pounds per square inch gauge.
Overpressure
= 10 pounds per square inch.
Superimposed back pressure
(constant)
= 70 pounds per square inch gauge.
Spring set
= 30 pounds per square inch.
Built-up back pressure
= 10 pounds per square inch
Percent absolute back pressure
=
(70 + 10 + 14.7)
▲
60
▲
70
▲
80
▲
90
▲
100
PB
= x 100 = r x 100
PS + PO
Note
This chart is typical and suitable for use only
when the make of the valve or the actual critical
flow pressure point for the vapor or gas is unknown; otherwise, the valve manufacturer
should be consulted for specific data. This correction factor should be used only in the sizing
of conventional (nonbalanced) pressure relief
valves that have their spring setting adjusted
to compensate for the superimposed back
pressure. It should not be used to size balanced-type valves.
x 100 = 76
(100 + 10 + 17.7)
Kb (follow dotted line)
= 0.89 (from the curve).
Capacity with back pressure
= 0.89 (rated capacity without back
pressure).
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136
P8 = back pressure, in pounds per square inch
absolute.
PS = set pressure, in pounds per square inch
absolute.
PO = overpressure, in pounds per square inch.
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Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
In this example, the following data are
derived:
Figure 30 – Capacity Correction Factor, Kw, Due to Back Pressure on
Balanced-Bellows Pressure Relief Valves in Liquid Service
a. Relieving pressure, P1, of 1600 x 1.1 +
14.7 = 1774.7 pounds per square inch
absolute.
1.00
0.90
KW = correction factor due
to back pressure.
0.80
0.70
PB = back pressure, in
pounds per square inch
gauge.
d. Superheat steam correction factor, KSH,
of 1.0.
0.60
PS = set pressure, in pounds
per square inch gauge.
The size of the relief valve is derived from
equation 8 as follows:
0.50
▲
0
c. Correction factor for Napier equation,
KN, of [0.1906(1774.7) - 1000] /
[0.2293(1774.7) - 1061] = 1.01.
KW
b. Effective coefficient of discharge, Kd, of
0.975.
▲
10
▲
20
▲
30
▲
50
▲
40
Percent of gauge = (P /P ) x 100
B
S
back pressure
153,500
A = ––––––––––––––––––––––––
51.5(1774.7)(0.975)(1.01)(1)
= 1.705 in2
Note
See API Standard 526, which also provides a purchase specification sheet for
flanged steel safety relief valves.
Select a ‘K’ orifice valve (1.838 in2), that
is, a 3K6 safety valve.
The curve above represents values recommended by various manufacturers. This curve
may be used when the manufacturer is not
known. Otherwise, the manufacturer should be
consulted for the applicable correction factor.
4.5 Sizing for Liquid Relief: Relief
Valves Requiring Liquid Capacity
Certification
4.5.1 General
Figure 31 – Capacity Correction Factor, Kv, Due to Viscosity
Q
A = –––––––––
38KdKwKv
––––––––
G
–––––––
P1 - P2
√
(9)
Where:
A = required effective discharge area, in
square inches.
1.0
0.9
KV = viscosity correction factor
Section VIII, Division I, of the ASME Code
requires that capacity certification be obtained for pressure relief valves designed
for liquid service. The procedure for obtaining capacity certification includes
determining the coefficient of discharge for
the design of liquid relief valves at 10%
overpressure. Valves that require a capacity in accordance with the ASME Code
may be sized using Equation 9.
0.8
0.7
0.6
0.5
0.4
Q = flow rate, in U.S. gallons per minute.
Kd = effective coefficient of discharge that
should be obtained from the valve
manufacturer. For a preliminary
sizing estimation, a discharge
coefficient of 0.65 can be used.
0.3
▲
10
▲
20
▲ ▲ ▲
40 50 100
▲
200
▲
400
▲
▲
1000 2000
▲
▲
▲
20,000
▲
100,000
R = Reynolds number
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Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
Kw = correction factor due to back
pressure. If the back pressure is
atmospheric, Kw = 1. Balancedbellows valves in back pressure service will require the correction factor
determined in Figure 31 on page
129. Conventional valves require no
special correction.
Kv = correction factor due to viscosity as
determined from page 28.
G = specific gravity of the liquid at the
flowing temperature referred to
water = 1.0 at 70°F.
P1 = upstream relieving pressure, in
pounds per square inch gauge. This
is the set pressure plus allowable
overpressure.
P2 = total back pressure, in pounds per
square inch gauge.
When a relief valve is sized for viscous liquid service, it should first be sized as it
was for nonviscous-type application so
that a preliminary required discharge area,
A, can be obtained. From manufacturers’
standard orifice sizes, the next larger orifice size should be used in determining
the Reynold’s number, R, from either of
the following relationships:
Q(2800G)
R = –––––––––
µ √––
A
(10)
U = viscosity at the flowing temperature, in
Saybolt Universal seconds.
After the value of R is determined, the factor Kv is obtained from page 28. Kv is
applied to correct the preliminary required
discharge area. If the corrected area exceeds the standard chosen orifice area,
the above calculations should be repeated
using the next larger standard orifice size.
In this example, the following relief
requirements are given:
Where:
Q = flow rate at the flowing temperature,
in U.S. gallons per minute.
G = specific gravity of the liquid at flowing
temperature referred to water
= 1.00 at 70°F.
µ = absolute viscosity at the flowing temperature, in centipoises.
a. Required crude-oil flow caused by
blocked discharge, Q, of 1800 gallons per
minute.
b. Specific gravity, G, of 0.90 (viscosity at
the flowing temperature is 2000 Saybolt
Universal seconds.)
c. Relief valve set at 250 pounds per
square inch gauge, the design pressure of
the equipment.
d. Back pressure variable from 0 to 50
pounds per square inch gauge.
In this example, the following data are
derived:
c. Back pressure of (50/250) x 100 = 20%.
A balanced-bellows valve is indicated,
since back pressure is variable. (From
Figure 31, Kw = 0.97.)
The manufacturer’s effective coefficient of
discharge K = 0.75.
Sizing first for no viscosity correction, (Kv
= 1.0), the size of the relief valve is derived from Equation 9 as follows:
Notes
10. Equation 11 is not recommended for
viscosities less than 100 Saybolt Universal
seconds.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
= 4.118
in2
See Equation 11. An area of 4.34 in2
(‘N’ orifice) should be used.
12,700 x 1800
R = ––––––––––––
= 5487
––––
2000 √ 4.34
From page 28, Kv = 0.965.
=
4.118
––––––
0.965
= 4.267 in2
b. Relieving pressure, P1, of 1.10 x 250 =
275 pounds per square inch gauge.
(11)10
––––––––
0.90
–––––––
(275-50)
√
1800
A = –––––––––––––––––––
38.0 x 0.75 x 0.97 x 1.0
AR
A = ––––
Kv
4.5.2 Example
a. Overpressure of 10%.
or
12,700Q
R = ––––––––
––
U √A
A = effective discharge area, in square
inches (from manufacturers’ standard
orifice areas).
138
Where:
AR = required area without viscosity
correction.
See API Standard 526, which also provides a purchase specification sheet for
flanged steel safety relief valves.
Select an ‘N’ orifice pressure relief valve
(4.34 square inches), that is, a 4N6 pressure relief valve.
4.6 Sizing for Liquid Relief: Relief
Valves Not Requiring Capacity
Certification
Before the ASME Code made provisions
for capacity certification, valves were
generally sized for liquid service using
Equation 12. This method assumes a
coefficient of discharge, Kd = 0.62, and
25 percent overpressure. An additional capacity correction factor, KP, was obtained
from Figure 33 for relieving pressures other than 25 percent overpressure. This
sizing method may be used where capacity certification is not required.
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Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
––––––––––
G
––––––––
125p - pb
√
Q
A = ––––––––––––
38 KdKwKvKp
(12)
Where:
A = required effective discharge area, in
square inches.
Q = flow rate, in U.S. gallons per minute.
Kd = effective coefficient of discharge that
should be obtained from the valve
manufacturer. For a preliminary
sizing estimation, a discharge coefficient of 0.62 can be used.
Kw = correction factor due to back
pressure. If back pressure is
atmospheric, Kw = 1. Balancedbellows valves in back-pressure
service will require the correction
factor determined from Figure 31.
Conventional valves require no
special correction.
Kv = correction factor due to viscosity as
determined from page 28.
Kp = correction factor due to overpressure. At 25% overpressure, Kp = 1.0.
For overpressures other than 25%,
Kp is determined from Figure 32.
G = specific gravity of the liquid at the
flowing temperature referred to water.
= 1.0 at 70°F.
p = set pressure, in pounds per square
inch gauge.
p b = total back pressure, in pounds per
square inch gauge.
4.7 Sizing for Two-Phase
Liquid/Vapor Relief
A pressure relief valve handling a liquid at
vapor-liquid equilibrium or a homogeneous mixed-phase fluid will produce
flashing with vapor generation as the fluid
moves through the valve. The vapor generation must be taken into account, since
it may reduce the effective mass flow capacity of the valve.
Calculations for determining properties
and handling liquid/vapor phases are
available; see Section 5 for emerging
technical literature that can be used to
size relieving devices.
For information about saturated water, see
specifically Section VIII, Appendix 11, of
the ASME Code.
4.8 Sizing for Rupture Disk Devices
A reasonable, conservative method of
sizing for two-phase liquid/vapor relief is
as follows:
Rupture disk devices may be used alone
or in combination with a pressure relief
valve in gas or vapor service or in liquid
service. The sizing of a rupture disk device used alone is based on the equations
applicable for pressure relief valves using
for all fluids an effective coefficient of discharge Kd = 0.62.
a. Determine the amount of liquid that
flashes by an isenthalpic (adiabatic)
expansion from the relieving condition
either to the critical downstream pressure for the flashed vapor or to the back
pressure, whichever is greater.
b. Calculate individually the orifice area
required to pass the flashed vapor
component, using Equations 2 – 7 as
appropriate, according to service, type
of valve, and whether the back pressure is greater or less than the critical
downstream pressure.
c. Calculate individually the orifice area
required to pass the unflashed liquid
component using Equation 9. The pressure drop (P1 – P2) is the inlet relieving
pressure minus the back pressure.
d. Add the individual areas calculated for
the vapor and liquid components to
obtain the total orifice area, A, that is
required.
e. Select a pressure relief valve that has
an effective discharge area equal to or
greater than the total calculated orifice
area. The designer should recheck the
back pressure that will exist for the
specific relief valve selected, with its
particular discharge installation, by
examining the vapor generation downstream of the pressure relief valve
nozzle. Where appropriate, corrections
can be applied to the particular orifice
areas previously calculated. Furthermore, selecting a balanced pressure
relief valve is often desirable to minimize the effect of flashed vapor on the
valve capacity.
The designer should also investigate the
effect of any auto-refrigeration that may
arise from the flashing of liquid. Materials
of construction must be adequate for the
outlet temperatures involved; in addition,
the installation must preclude the possibility of flow blockage occurring from hydrate
or possibly solid formation.
4.8.1 Rupture Disk Devices Used
Independently
The required discharge area, A in square
inches, is calculated using the appropriate
equation for the flowing medium (see
Equations 2– 7 for gas or vapor, Equation
8 for steam, and Equation 9 for liquid).
The rupture disk device selected should
be the nominal pipe size whose area is
equal to or greater than the required discharge area calculated by the appropriate
equation.
For rupture disk devices that have a structural member (for example, a knife blade
or vacuum support) that reduces the effective discharge area after bursting, the
projected area of the structural member is
deducted from the flow area of the pipe to
determine the net discharge area of the
burst rupture disk.
Users should be aware of the following
limitations in using Kd = 0.62 to determine
the capacity of a given size of rupture
disk, or conversely, the required area for
a given flow quantity:
a. The rupture disk device is used in a
size and pressure range that the manufacturer has determined will give a
satisfactory opening for the style of rupture disk in the particular fluid service.
b. The rupture disk device is installed in a
short piping system that does not add
significantly to the flow resistance of the
burst rupture disk device.
If a rupture disk device discharges into a
vent system or a closed relief system, it
will usually not contribute significantly to
the pressure loss obtained in the discharge piping. The sizing of the inlet and
discharge piping becomes a line sizing
problem that uses the relieving rate and
the maximum allowable inlet pressure defined by the code. In general, a pressure
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Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
Figure 32 – Capacity Correction Factors Due to Overpressure for Relief
and Safety-Relief Valves in Liquid Service
The curve in Fig. 32 shows that up to and including 25 percent overpressure, capacity is
affected by the change in lift, the change in orifice discharge coefficient, and the change in
overpressure. Above 25 percent, capacity is affected only by the change in overpressure.
Valves operating at low overpressures tend to
chatter; therefore, overpressures of less than 10
percent should be avoided.
1.10
0.90
Correction factor, Kp
Notes
0.70
0.50
0.30
0.10
▲
▲
▲
▲
▲
10
20
30
40
50
Percent overpressure
loss through the rupture disk device of approximately 75 pipe diameters may be
used. The manufacturer should be consulted if more accurate values are
required. This problem is similar to the line
sizing of a process line except that the effect of volumetric expansion on the
pressure loss must be considered. This
will include an acceleration effect (the
vapor is exiting the discharge piping at a
higher velocity) as well as the effect of
changing density. If the vent line subsequently discharges into headers of varying
sizes, critical flow restrictions must be
considered.
4.8.2 Rupture Disk Devices Used in
Combination With Pressure Relief
Valves
An important application of a rupture disk
device is at the inlet of a pressure relief
valve. The sizing of the pressure relief
valve/rupture disk device combination requires that the pressure relief valve first
be sized to meet the required relieving capacity. The certified and published
capacity of the pressure relief valve used
alone is then multiplied by the combination capacity factor, K c, to determine the
capacity of that combination. (See 2.6.2
for further information on the combination
capacity factor.)
The nominal size of the rupture disk device installed at the inlet of the pressure
relief valve must be equal to or greater
than the nominal size of the inlet connection of the valve to permit sufficient flow
capacity and valve performance.
The design of the piping from the protected vessel to the inlet of the pressure relief
valve is crucial to the proper functioning of
the valve. Users should consult applicable
engineering codes for guidance on inlet
piping design. Unless the pressure relief
device is installed directly on the vessel, a
good practice is to analyze the frictional
pressure loss from the vessel to the valve
inlet at the rated relieving capacity to comply with recommended limits. An inlet pipe
sized larger than necessary for the inlet to
the pressure relief valve is often required;
this may dictate a rupture disk device to
match the pipe size.
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Excerpts from API - 520 Part I Sizing, Selection, and Installation of
Pressure Relieving Devices in Refineries
References
1. N.E. Sylvander and D.L. Katz,
“Investigation of Pressure Relieving
Systems,” Engineering Research
Bulletin No. 31, University of Michigan,
Ann Arbor, April 1948.
2. Recommended Practice for the Design
and Construction of Pressure
Relieving Systems for Process
Equipment and Pressure Storage in
Refineries (tentative), American
Petroleum Institute, August 1954.
3. F.J. Heller, “Safety Relief Valve Sizing:
API Versus CGA Requirements Plus a
New Concept for Tank Cars,” 1983
Proceedings–Refining Department,
Volume 62, American Petroleum
Institute, Washington, D.C., pp. 123-135.
4. H.R. Wharton, “Digest of Steels for
High Temperature Service,” Timken
Steel, 1946.
5. J.J. Duggan, C.H. Gilmour, and P.F.
Fisher, “Requirements for Relief of
Overpressure in Vessels Exposed to
Fire,” Transactions of the ASME, 1944,
Volume 66, pp. 1-53.
6. I. Heitner, T. Trautmauis and M.
Morrissey, “Relieving Requirements for
Gas Filled Vessels Exposed to Fire,”
1983 Proceedings–Refining
Department, Volume 62, American
Petroleum Institute, Washington, D.C.,
pp. 112-122.
7. J. O. Francis and W.E. Shackelton, “A
Calculation of Relieving Requirements
of the Critical Region,” 1985
Proceedings–Refining Department,
Volume 64, American Petroleum
Institute, Washington D.C., pp. 179-182.
8. H.G. Fisher, “DIERS Research
Program on Emergency Relief
Systems,” Chemical Engineering
Progress, August 1985, pp. 33-36.
9. H.K. Fauske and J.C. Leung, “New
Experimental Technique for
Characterizing Runaway Chemical
Reactions,” Chemical Engineering
Progress, August 1985, pp. 39-46.
10. M.A. Grolmes and J.C. Leung, “Code
Method for Evaluating Integrated
Relief Phenomena,” Chemical
Engineering Progress, August 1985,
pp. 47-52.
11. H.K. Fauske, “Emergency Relief
System Design,” Chemical
Engineering Progress, August 1985,
pp. 53-56.
12. M.A. Grolmes, J.C. Leung, and H.K.
Fauske, “Large-Scale Experiments of
Emergency Relief Systems,” Chemical
Engineering Progress, August 1985,
pp. 57-62.
13. Publication 999 (English Edition),
Technical Data Book–Petroleum
Refining, American Petroleum
Institute, Washington, D.C.
14. O. Cox, Jr. and M.L. Weirick, “Sizing
Safety Valve Inlet Lines,” Chemical
Engineering Progress, November
1980.
15. B.A. Van Boskirk, “Sensitivity of Relief
Valves to Inlet and Outlet Line
Lengths,” Chemical Engineering,
August 1982.
16. C.E. Lapple, “Isothermal and Adiabatic
Flow of Compressible Fluids,”
Transactions of the American Institute
of Chemical Engineers, 1943, Volume
39, pp. 385-432.
17. H.Y. Mak, “New Method Speeds
Pressure-Relief Manifold Design,” Oil
and Gas Journal, November 20, 1978.
18. P. Kandell, “Program Sizes Pipe and
Flare Manifolds for Compressible
Flow,” Chemical Engineering, June 29,
1981.
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Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
D.1 Background
The problem of estimating fire-relief
requirements for storage tanks was first
recognized in 1928 when the National Fire
Protection Association (NFPA) requested
API to recommend that a table of minimum emergency relief capacities for a
series of tank capacities be included in the
NFPA Suggested Ordinance Regulating
the Use, Handling, Storage and Sale of
Flammable Liquids and the Products
Thereof.
It was later recognized that tank capacities did not provide the best basis for
estimating the amount of vapor to be
handled. Since the heat was absorbed
almost entirely by radiation, the area
exposed — not the volume of the tank contents — seemed to be the important factor.
Many of the tanks were large and could
never be expected to be entirely surrounded by fire; the assumption was therefore
made that the larger the area of the container, the less the likelihood that the tank
would be fully exposed to radiation. In other words, the larger the surface area of
the tank shells, the lower the average unit
heat absorption rate from a fire.
By 1948 several different equations [1]1
were in general use, prompting the API
Subcommittee on Pressure-Relieving
Systems to develop an equation for determining the heat absorbed from open fires
using the test data available at the time.
The resultant equation has remained in
general use since its publication in 1954
[2], and its development is documented in
a paper presented by F.J. Heller in 1983
[3].
Table D-1 contains data from 16 fire tests
and one actual fire. Data from these tests
were considered in the development of
Equations D-1 and D-2.
These data result from tests in which
means were provided to measure the
total heat absorbed by a vessel by (a)
computing the heat required to bring the
liquid contents to the boiling range and
(b) measuring the amount of liquid contents evaporated in a given time. The unit
heat absorption rates in Table D-1 are
average rates on the wetted surface.
Examinations of detailed reports on these
tests indicate that the setup for Tests 4, 5,
and 8 was arranged to provide continuous
and complete flame envelopment of the
small vessels; under these conditions,
maximum average heat input rates of 30,
400-32, 500 British thermal units per hour
per square foot were realized. The environmental conditions set up for tests 1, 3,
6, 7, 9, and 10 allowed the flame to be
subjected to air currents and wind. All other factors were conducive to maintaining
maximum heat input, a condition that
should not exist in a refinery. Under these
conditions, the maximum average heat input rates varied greatly. Test 2 differed
from Test 1 in that drainage away from the
equipment was provided. The maximum
heat input rate is reduced by 60% when
drainage is provided; this fact was incorporated in the development of Equations
D-1 and D-2. Test 11 gives an indication of
the effect of a large area on average heat
input during an actual fire.
The test reports mentioned in some cases
that the tests were delayed until the arrival
of a calm day so that the wind would not
blow the flames away from the vessel.
Copious supplies of fuel were available. In
most cases, the fuel was maintained by
dikes in a pool beneath the vessel and
was not allowed to drain away as it normally would. In the Rubber Reserve
Corporation tests, a 2-inch gasoline line,
running full, was required to keep the fuel
supplied during the test. Without these
special adverse conditions, the maximum
heat absorption values obtained in these
tests are extremely unlikely to occur in an
actual refinery fire.
D.2 Nature of an Open Fire
The nature of an open fire of flammable
fluid, as related to test data, is important.
Note
1. Numbers in brackets correspond to references in Section 5.
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142
This kind of fire differs from the fire in the
firebox of a boiler or still, where the fuel
and air are mixed by means other than the
convection currents caused by the heated
gases. The flame will accordingly have a
core of flammable vapor, either unmixed
with air or insufficiently mixed to burn.
Combustion occurs on the exterior envelope of this core. Because the actual
combustion zone is on the rich side, a
considerable amount of black smoke is
generated. This envelope of soot may
serve to mask a considerable portion of
the flame.
Hot gases from the combustion rise, and
the air that supports the combustion flows
in at the bottom. The flame mass is quite
turbulent; as masses of the burning vapor
tumble and billow, the smoky mantle is
displaced and the bright flame can be
seen intermittently. This flame is not a
blazing white, as it would be in a furnace;
it is red or orange, indicating a lower temperature than that of a furnace flame.
Flames of this type tend to rise because of
their temperature; however, they can also
be blown aside by the wind and may be
blown so far from a vessel that the heating
effect on the vessel is small.
D.3 Effect of Fire on the Unwetted
Surface of a Vessel
D.3.1 General
Unwetted wall vessels are those in which
the internal walls are exposed to a single
fluid, vapor, or gas or are internally insulated regardless of the contained fluids.
These include vessels that contain separate liquid and vapor phases under normal
conditions but become single phase
(above the critical) at relieving conditions.
Vessels may be designed to have internal
insulation. A vessel should be considered
internally insulated when the internal wall
can become insulated by the deposition of
coke or other materials as a result of the
contained fluids.
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Excerpts from API - 520 Part I Sizing, Selection, and Installation of Pressure Relieving Devices in Refineries
Table D-1
Comparison of Heat-Absorption Rates in Fire Tests
Test
Source
Type
of Exposure
1
Hottell, average
of 36 tests
6-inch thick
metal stack
Hottell, average
6-inch thick
of 13 tests
metal stack
Standard Oil Co.
of California
Heating water
in drum
Standard Oil Co.
Heating water
of California
in tank
Underwriters
Laboratories, Inc.
Water flowing
over plate
2
3
4
5
6
7
8
9
10
11a
Rubber Reserve
Heating water
Corp.Test No.17
in tank
Rubber Reserve
Corp.Test No.17
Generating
steam in tank
Rubber Reserve
Corp.Test No.17
Water flowing in
3/4-inch
standard pipe
API Project
Test No.1
Heating water
in tank
API Project
Heating water
Test No. 2
in tank
Report to API on 38 ft.
butane sphere
Plant fire
Fuel
Gasoline
Gasoline
Vessel Total Wetted
Total
Capacity Area Area Heat Input
(barrel) (ft2)
(ft2)
(BTU/Hr)
Conning
Tower
Conning
Tower
Naphtha
2.6
Naphtha
33
Gasoline
Temperature BTU/Hr/Ft2 Refer.
of
Wetted
Surface (°F)
296
123
3,760,000
30,500
1
296
123
2,139,000
17,400
2
26
416,000
16,000
3
206
105
3,370,000
70-212
32,000
3
24
24
780,000
76
32,500
4
300
23,200
5
Gasoline
119
568
400
9,280,000
Gasoline
199
568
400
8,400,000
21,000
5
9.0
9.0
274,000
30,400
5
Gasoline
Kerosene
0.88
16.2
6.1
95,800
300
15,700
6
Kerosene
0.88
16.2
6.1
102,500
320
16,800
6
Butane
5,000
4,363
4,363
23,560,000
5,400
7
12
Lauderback
Chemical waste
100
100
3,210,000
32,100
8
13
NFPA (Tulsa)
Cutback jet fuel
238
773
303
8,736,000
23,000
9
14
Union Carbide (1938)
Propane
71.4
242
132
2,300,000
17,400
10
15
Union Carbide (1938)
Propane
71.4
242
176
4,993,000
28,400
10
16
Fetterly
7.7
83
57.8
1,350,000
23,300
11
aThis
represents an actual fire
Liquefied petroleum
Wood saturated
gas container
with kerosene
References
1. H.C. Hottell, Private communication to API
Subcommittee on Pressure-Relieving
Systems, January 1948.
2. H.C. Hottell, Private communication to API
Subcommittee on Pressure-Relieving
Systems, December 1950.
3. F.L. Maker Private communication to API
Subcommittee on Pressure-Relieving
Systems regarding 1925 tests, December
22,1950.
4. “Opacity of Water to Radiant Heat Energy,”
Research Bulletin 3, Underwriters
Laboratory, Inc., 1938.
5. Safety Memorandum 89, Rubber Reserve
Corporation, Washington, D.C., May 1944.
6. University of Michigan, Unpublished tests
made for API Subcommittee on PressureRelieving Systems, June 1947.
7. Anonymous report to API Subcommittee on
Pressure-Relieving Systems regarding a fire
(not a test), June 1941.
8. J.J. Duggan, C.H. Gilmour, and P.F. Fisher,
“Requirements for Relief of Overpressure
on Vessels Exposed to Fire,” Transactions
of the ASME, 1944, Volume 66, pp. 1-53.
9. “Large Scale Fire Exposure Tests to
Evaluate ‘Unox’ Foam for Fire Exposure
Protection,” Fire Research Laboratory
Report No. FRL-62, Process Safety
Department, Carbide and Carbon
Chemicals Co., a Division of Union Carbide
and Carbon Corporation, Dec. 8, 1954.
10. Lauderback.
11. National Fire Protection Association.
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D.3.2 Characteristics
A characteristic of a vessel with an unwetted internal wall is that heat flow from the
wall to the contained fluid is low as a result of the resistance of the contained fluid
or any internal insulating material. Heat input from an open fire to the bare outside
surface of an unwetted vessel may, in
time, be sufficient to heat the vessel wall
to a temperature high enough to rupture
the vessel. Figures D-1 and D-2 indicate
how quickly an unwetted vessel wall might
be heated to rupture conditions. Figure
D-1 illustrates the rise in temperature that
occurs with time in the unwetted plates of
various thicknesses exposed to open fire;
for example, an unwetted steel plate
1-inch thick would take about 12 minutes
to reach approximately 1100°F and about
17 minutes to reach 1300°F when the
plate is exposed to an open fire.
Figure D-2 shows the effect of overheating ASTM A 515, Grade 70 steel [4]. The
figure indicates that at a stress of 15,000
pounds per square inch, an unwetted
steel vessel would rupture in about 7
hours at 1100°F and about 21/2 minutes
at 1300°F.
D.4 Effect of Fire on the Wetted
Surface of a Vessel
The surface area wetted by a vessel’s
internal liquid contents is effective in generating vapor when the area is exposed to
fire. To determine vapor generation, only
that portion of the vessel that is wetted by
its internal liquid and is equal to or less
than 25 feet above the source of flame
needs to be recognized. The term source
of flame usually refers to ground grade but
could be at any level at which a substantial spill or pool fire could be sustained.
Various classes of vessels are operated
only partially full. Table D-2 gives recommended portions of liquid inventory for
use in calculations. Portions higher than
25 feet are normally excluded.
gree to which the vessel is enveloped by
the flames (a function of vessel size and
shape), and fireproofing measures. The
following equivalent formulas are used to
evaluate these conditions where there are
prompt fire-fighting efforts and drainage of
flammable materials away from the vessel:
q = 21,000FA-0.18
(D-1)
21,000FA0.82
(D-2)
Q=
Where adequate drainage and fire-fighting
equipment do not exist, Equation D-2 becomes the following [3]:
Q = 34,500FA0.82
(D-1)
Where:
q = average unit heat absorption, in British
thermal units per hour per square foot
of wetted surface.
Q = total heat absorption (input) to the
wetted surface, in British thermal units
per hour.
F = environment factor. (Values for various
types of insulation are shown in Table
D-3.)
A = total wetted surface, in square feet
(see D.4). (The expression A-0.18, or
1/A0.18, is the area exposure factor or
ratio. This ratio recognizes the fact
that large vessels are less likely than
small ones to be completely exposed
to the flame of an open fire.)
D.5.2 Heat Absorption Across the
Unwetted Surface of a Vessel
D.5.2.1 Simple Equations
See D.3 for a discussion of the effect of
fire on the unwetted surface of a vessel.
The discharge areas for pressure relief
valves on gas-containing vessels exposed
to open fires can be determined using the
following formula:
F´A´
A = –––––
–––
√P1
(D-3)
D.5.1 Heat Absorption Across the
Wetted Surface of a Vessel
F´ can be determined from the following
relationship. The recommended minimum
value of F´ is 0.01; when the minimum
value is unknown, F´ = 0.045 should be
used.
The amount of heat absorbed by a vessel
exposed to open fire is markedly affected
by the type of fuel feeding the fire, the de-
0.1406
F´ = ––––––
CKD
D-5 Heat Absorption Equations
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(Tω – T1)1.25
–––––––––––
T10.6506
(D-4)
144
Where:
A = effective discharge area of the valve,
in square inches.
A´ = exposed surface area of the vessel,
in square feet.
P1 = upstream relieving pressure, in
pounds per square inch absolute.
This is the set pressure plus the
allowable overpressure plus the
atmospheric pressure.
C = coefficient determined by the ratio of
the specific heats of the gas at standard conditions. This can be obtained
from Figure 26 or Table 9.
KD = coefficient of discharge (obtainable
from the valve manufacturer). The
maximum allowable KD established
by ASME is 0.975.
Tω = vessel wall temperature, in degrees
Rankine.
T1 = gas temperature, absolute, in degrees Rankine, at the upstream
pressure, determined from the following relationship:
P1
T1 = ––– Tη
Pη
Where:
Pη = normal operating gas pressure, in
pounds per square inch absolute.
Tη = normal operating gas temperature, in
degrees Rankine.
The recommended maximum vessel wall
temperature for the usual carbon steel
plate materials is 1100°F. Where vessels
are fabricated from alloy metals, the value
for Tω should be changed to a more appropriate recommended maximum.
D.5.2.2 Rearrangement of Simple
Equations
The relief load can be calculated directly
in pounds per hour by rearranging Equation
2 and substituting Equations D-3 and D-4,
which results in the following equation:
W = 0.1406
√MP1
T –T )
(A´ (––––––––––
)(D-5)
T
ω
1
1.25
1.1506
1
Where:
M = molecular weight of the gas.
Z and Kb in Equation 2 are assumed to
equal 1.
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Pressure Relieving Devices in Refineries
Figure D-1 – Average Rate of Heating Steel Plates Exposed to Open
Gasoline Fire on One Side
Plate 1/8-inch thick (as computed)
Plate temperature, degrees Fahrenheit (averaged over 24 square feet)
1600
Plate 1/2-inch thick (as computed)
Plate 1/8-inch thick
(as observed)
1400
1200
Plate 1/2-inch thick (as computed)
1000
800
600
400
200
0
▲
0
▲
4
▲
8
▲
12
▲
16
▲
20
▲
24
Minutes after start of fire
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Rupture stress (pounds per square inch x 1000)
Figure D-2 – Effect of Overheating Steel (ASTM A 515, Grade 70)
100
900°F
1000°F
1100°F
1200°F
1300°F
10
1400°
F
Oxida
tion e
ffect
1.0
0.1
▲
▲
▲
▲
▲
▲
0.01
0.1
1.0
10
100
1000
Time for rupture (hours at indicated temperature)
D.5.2.3 Discussion of Simple Equations
The derivation of Equations D-3 and D-5
[5] is based on the physical properties of
air and the perfect gas laws. The derivation assumes that the vessel is uninsulated
and has no mass, that the vessel wall
temperature will not reach rupture stress,
and that there is no change in fluid temperature. These assumptions should be
reviewed to ensure that they are appropriate for any particular situation.
D.5.2.4 More Rigorous Calculations
When the assumptions in D.5.2.3 are not
appropriate, more rigorous methods of
calculation may be warranted. In such
cases, the necessary physical properties
of the containing fluid may need to be obtained from the actual data or estimated
from equations of state. The effects of
vessel mass and insulation may need to
be considered. The pressure-relieving rate
is based on an unsteady state. As the fire
continues, the vessel wall temperature
and the contained gas temperature and
pressure increase with time. The pressure
relief valve will open at the set pressure,
or if the pressure is set too high, the vessel will rupture. With the loss of fluid on
relief, the temperatures will further increase at the relief pressure. If the fire is
of sufficient duration, the temperature will
increase until vessel rupture occurs.
Procedures are available for estimating
the changes in average vessel wall and
contained fluid temperatures that occur
with time and the maximum relieving rate
at the set pressure [6, 7]. The procedures
require successive iteration.
D.5.2.5 Additional Protective Measures
The determination may be made that a
pressure relief valve will not provide sufficient protection for an unwetted wall
vessel, and vessel rupture could occur before or too soon after initial relief. Where a
pressure relief valve alone is not adequate, additional protective measures
should be considered, including insulation
(D.8.3.1), water sprays (D.8.3.3), and depressuring (D.8.2) to avoid vessel rupture.
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Where calculations indicate that rupture
would not occur prior to relief, a rupture
disk device could also be considered.
The design should allow sufficient time for
operator action and initiation of fire-fighting procedures before possible vessel
rupture. Operator action may include depressuring, using water sprays, and
employing firewater monitors.
D.6 Fluids To Be Relieved
A vessel may contain liquids or vapors or
fluids of both phases. The liquid phase
may be subcritical at operating temperature and pressure and may pass into the
critical or supercritical range during the
duration of a fire as the temperature and
pressure in the vessel increase.
The quantity and composition of the fluid
to be relieved during a fire depend on the
total heat input rate to the vessel under
this contingency and on the duration of
the fire.
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Table D-2
Wetted Surface Area of A Vessel Based on Fire Heat Absorbed
Class of Vessel
Portion of Liquid Inventory
Remarks
Liquid-full, such as treaters
All up to the height of 25 feet
—
Surge drums, knockout drums, process vessels
Normal operating level up to the height of 25 feet
—
Fractionating columns
Normal level in bottom plus liquid holdup from
all trays; total wetted surface up to
the height of 25 feet
Level in reboiler is to be
included if the reboiler is
an integral part of the column
Average inventory level up to
For tanks of 15 psig operating pressure
the height of 25 feet
or less; see API Standard 2000
Up to the maximum horizontal diameter
or up to the height of 25 feet,
whichever is greater
—
Working storage
Spheres and spheroids
The total heat input rate to the vessel may
be computed by means of one of the
formulas in Section D.5 using the appropriate values for wetted or exposed
surfaces and for the environment factor.
The latent-heat and molecular-weight
values used in calculating the rate of vaporization should pertain to the conditions
that are capable of generating the maximum vapor rate.
the vessel and from the latent heat of liquid contained in the vessel becomes
invalid near the critical point of the fluid,
where the latent heat approaches zero
and the sensible heat dominates.
Once the total heat input rate to the vessel
is known, the quantity and composition of
the fluid to be relieved can be calculated,
provided that enough information is available on the composition of the fluid
contained in the vessel.
The vapor and liquid composition may
change as vapors are released from the
system. As a result, temperature and latent-heat values could change, thus
affecting the required size of the pressure
relief device. On occasion, a multicomponent liquid may be heated at a pressure
and temperature that exceed the criticals
for one or more of the individual components. For example, vapors that are
physically or chemically bound in solution
may be liberated from the liquid upon heating. This is not a standard latent-heating
effect but is more properly termed degassing or dissolution. Vapor generation is
determined by the rate of change in equilibrium caused by increasing temperature.
When no accurate latent-heat value is
available for these hydrocarbons near the
critical point, a minimum value of 50
British thermal units per pound is sometimes acceptable as an approximation.
If the fluid contained in the vessel is not
completely specified, assumptions must
be made to obtain a realistic relief flow
rate for the relief device. These assumptions may include the following:
a. An estimation of the latent heat of
boiling liquid and the appropriate molecular weight of the fraction vaporized.
b. An estimation of the thermal expansion
coefficient if the relieving fluid is a liquid
below its boiling temperature, a gas, or
a supercritical fluid.
D.6.1 Vapor
For pressure and temperature conditions
below the critical point, the rate of vapor
formation—a measure of the rate of vapor
relief required—is equal to the total rate
of heat absorption divided by the latent
heat of vaporization. The vapor to be relieved is the vapor that is in equilibrium
with the liquid under conditions that exist
when the valve is relieving at its accumulated pressure.
For these and other multicomponent mixtures that have a wide boiling range, a
time-dependent model may have to be developed where the total heat input to the
vessel not only causes vaporization but
also raises the temperature of the remaining liquid, keeping it at its boiling point.
Reference 7 gives an example of a timedependent model used to calculate relief
requirements for a vessel exposed to fire
that contains fluids near the critical range
or above.
The recommended practice of finding a
relief vapor flow rate from the heat input to
When pressure-relieving conditions are
above the critical point, the rate of vapor
discharge depends only on the rate at
which the fluid will expand as a result of
the heat input.
D.6.2 Liquid
The hydraulic expansion formula given in
Appendix C may be used to compute the
initial liquid-relieving rate in a liquid-filled
system when the liquid is still below its
boiling point. However, this rate is valid for
a very limited time, after which vapor generation will become the determining
contributor in the sizing of the pressure
relief device.
There is an interim time period between
the liquid expansion and the boiling vapor
relief in which mixtures of both phases
need to be relieved simultaneously, either
as flashing, bubble, slug, froth, or mist
flow until sufficient vapor space is available
inside the vessel for phase separation.
This mixed-phase condition is usually neglected, but for some vessels, particularly
overfilled steam drums or polymerization
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reactors, the limiting relieving contingency
may be the factor that would determine
the size of the relieving device. (See D.6.3
for information about mixed-phase flow.)
Should a pressure relief device be located
in the liquid zone of a vessel exposed to
fire conditions, the pressure relief device
must be able to pass a volume of liquid
equivalent to the displacement caused by
vapor generated by the fire.
D.6.3 Mixed Phase
As stated in D.6.2, mixed-phase flow may
sometimes be the limiting relieving contingency and thus will determine the size of
the pressure relief device. This is particularly true for reactors during runaway
reactions that may be caused by lack of
cooling or excess heat input (for example,
under fire).
The Design Institute for Emergency Relief
Systems recently concluded an intensive
research program to develop methods for
the design of emergency relief systems to
handle runaway reactions. The interested
reader is advised to study some introductory publications [8-12] on this subject in
Chemical Engineering Progress, August
1985.
D.7 Data on Latent Heat of
Vaporization of Hydrocarbons
Different hydrocarbon liquids have different latent heats of vaporization even
though hydrocarbons as a group behave
similarly to one another. The latent heat of
vaporization of a pure single-component
liquid decreases as the temperature at vaporization increases and the latent heat
becomes zero at the critical temperature
and pressure for that liquid.
Figure D-3 shows the vapor pressures
and latent heats of the pure single-component paraffin-hydrocarbon liquids. This
chart is directly applicable to such liquids
and applies as an approximation to paraffin-hydrocarbon mixtures composed of
two components whose molecular weights
vary no more than propane to butane and
butane to pentane.
The chart may also be applicable to isomer
hydrocarbons, aromatic or cyclic compounds, or paraffin-hydrocarbon mixtures
of components that have slightly divergent
molecular weights. The equilibrium temperature should be calculated. Using the
relationship for the calculated temperature
versus vapor pressure, the latent heat can
then be obtained from Figure D-3. The
molecular-weight relationship as shown by
the chart is not to be used in such cases;
the molecular weight of the vapor should
be determined from the vapor-liquid equilibrium calculation.
For cases that involve mixtures of components that have a wide boiling range or
widely divergent molecular weights, a rigorous series of equilibrium calculations
may be required to estimate vapor generation rates, as discussed in D.6.1.
Other recognized sources [13] of latentheat data or methods of calculating latent
heat of vaporization should be used where
Figure D-3 does not apply.
D.8 Protecting Vessels Against Fire
Exposure
The measures described in D.8.1 through
D.8.3 for protecting vessels against fire
exposure are contingent on proper
drainage away from the vessel so that
pools of fuel cannot accumulate beneath
them.
Improper drainage under fire conditions
will limit the effectiveness of any of these
measures in reducing the intensity of heat
absorption by the vessels.
Table D-3
Notes
Environment Factor
Type of Equipment
Bare vessel
Factor F1
1.0
vessel2
Insulated
(These arbitrary insulation conductance
values are shown as examples and are in British thermal
units per hour per square foot per degree Fahrenheit):
4
0.3
2
0.15
1
0.075
0.67
0.05
0.5
0.0376
0.4
0.03
0.33
0.026
Water-application facilities, on bare vessel3
1.0
Depressurizing and emptying facilities4
1.0
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148
1. These are suggested values for the conditions assumed in D.5.1. When these conditions
do not exist, engineering judgment should be
exercised either in selecting a higher factor or in
providing means of protecting vessels from fire
exposure as suggested in D.8.
2. Insulation shall resist dislodgement by firehose streams. For the examples, a temperature
difference of 1600°F was used. These conductance values are based on insulation having
thermal conductivity of 4 BTU/hr-Ft2-°F per inch
at 1600°F and correspond to various thicknesses of insulation between 1 and 12 inches.
3. See D.8.3.3.
4. See D.8.2.
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D.8.1 Effectiveness of Pressure
Relief Devices as Related to Fire
Exposure
The effect of fire exposure on the unwetted surface of vessels is described in
D.3. A pressure relief device does not
prevent weakening and failure of a vessel that becomes locally overheated and
overstressed at an unwetted surface. It
will only prevent the internal pressure
from rising beyond the allowable accumulation pressure. A vessel may be
protected against such failure by (a) depressurizing the vessel and (b) limiting
the heat input.
D.8.2 Depressuring Systems
Controlled depressuring of the vessel reduces internal pressure and stress in the
vessel walls. It also guards against the potential addition of fuel to the fire should the
vessel rupture. The design of depressuring systems should recognize the
following factors:
a. Manual controls near the vessel may be
inaccessible during an emergency.
b. Unless anticipated, automatic controls
could fail in a direction that would prevent depressuring (for example, valves
that fail closed).
c. Early initiation of depressuring is desirable to limit vessel stress to acceptable
levels commensurate with the vessel
wall temperature that results from a fire.
d. Safe disposal of vented streams must
be provided.
e. No credit is recommended when
safety valves are being sized for fire
exposure.
Further information on depressuring is provided in API Recommended Practice 521.
D.8.3 Methods of Limiting Heat
Input From Fire
D.8.3.1 External Insulation
Limiting the heat input from fires by external insulation reduces both the rise of the
vessel wall temperature and the generation of vapor inside the vessel. Insulation
may also reduce the problem of disposing
of the vapors and the expense of providing
an exceptionally large relieving system to
conduct the effluent to a point of disposal.
The insulation must be fire resistant and
protected from dislodgement by fire-hose
streams (see API Recommended Practice
521).
Where insulation or fireproofing is applied,
the heat absorption can be computed by
assuming that the outside temperature of
the insulation jacket or other outer covering
has reached an equilibrium temperature of
1660°F. With this temperature and the operating temperature for the inside of the
vessel, together with the thickness and
conductivity of the fire-protection coating,
the average heat transfer rate to the contents can be computed. It must be kept in
mind that the thermal conductivity of the
insulation increases with the temperature,
and a mean value should be used.
D.8.3.2 Earth-Covered Storage
Covering a pressure vessel with earth is
another effective method of limiting heat
input. The reduction of heat absorption
due to the earth cover can be calculated
as suggested in D.8.3.1.
D.8.3.3 Cooling the Surface of a
Vessel With Water
Under ideal conditions, water films covering the metal surface can absorb most
incident radiation. The reliability of water
application depends on many factors.
Freezing weather, high winds, clogged
systems, undependable water supply, and
vessel surface conditions can prevent uniform water coverage. Because of these
uncertainties, no reduction in environment
factor (see Table D-3) is recommended;
however, as stated previously, properly
applied water can be very effective.
D.8.3.4 Limiting Fire Areas With
Diversion Walls
Diversion walls can be provided to deflect
vessel spills from other vessels.
For insulated vessels, the environment
factor for insulation becomes the following:
k (1660 – Tf)
F = ––––––––––––
21,000t
Where:
k = thermal conductivity of insulation, in
British thermal units per hour per
square foot per degree Fahrenheit per
inch at mean temperature.
Tf = temperature of vessel contents at
relieving conditions, in degrees
Fahrenheit.
t = thickness of insulation, in inches.
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Section 1 – General
1.1 Scope
This recommended practice is intended to
cover methods of installation for pressure
relief devices for equipment that has a
maximum allowable working pressure
(MAWP) of 15 pounds per square inch
gauge (psig) (1.03 barg) or greater.
Pressure relief valves or rupture disks may
be used independently or in combination
with each other to provide the required
protection against excessive pressure accumulation. As used in this recommended
practice, the term pressure relief valve includes safety relief valves used in either
compressible or incompressible fluid service, and relief valves used in
incompressible fluid service. This recommended practice covers gas, vapor,
steam, and incompressible service; it does
not cover special applications that require
unusual installation considerations.
1.2 Definition of Terms
The terminology for pressure relief devices that is used in this recommended
practice is in general agreement with the
definitions given in ASME PTC 25.
Section 2 – Inlet Piping
2.1 General Requirements
For general requirements for inlet piping,
see Figures 1 and 2.
2.1.1 Flow and Stress Considerations
Inlet piping to the pressure relief device
should provide for proper system performance. This requires design consideration
of the flow-induced pressure drop in the
inlet piping. Excessive pressure losses in
the piping system between the protected
vessel and a pressure relief device will adversely affect the system-relieving
capacity and can cause valve instability. In
addition, the effect of stresses derived
from both pressure relief device operation
and externally applied loads must be considered. For more complete piping design
guidelines, see ASME B31.3.
2.1.2 Vibration Considerations
Most vibrations that occur in inlet piping
systems are random and complex. These
vibrations may cause leakage at the seat
of a pressure relief valve, premature
opening, or premature fatigue failure of
certain valve parts, inlet and outlet piping,
or both. Vibration in inlet piping to a rupture disk may adversely affect the burst
pressure and life of the rupture disk.
Figure 1 – Typical Pressure Relief
Valve Installation: Atmospheric
(Open) Discharge
Detrimental effects of vibrations on the
pressure relief device can be reduced by
minimizing the cause of vibrations, by additional piping support, by use of either
pilot-operated relief valves or soft-seated
pressure relief valves, or by providing
greater pressure differentials between the
operating pressure and the set pressure.
Weather cap may be required
2.2 Pressure-Drop Limitations and
Piping Configurations
For pressure-drop limitations and piping
configurations, see Figures 1-4.
2.2.1 Pressure Loss at the Valve Inlet
Excessive pressure loss at the inlet of a
pressure relief valve can cause rapid
opening and closing of the valve, or chattering. Chattering will result in lowered
capacity and damage to the seating surfaces. The pressure loss that affects valve
performance is caused by non-recoverable entrance losses (turbulent
dissipation) and by friction within the inlet
piping to the pressure relief valve.
Chattering has sometimes occurred due
to acceleration of liquids in long inlet lines.
2.2.2 Size and Length of Inlet Piping
When a pressure relief valve is installed
on a line directly connected to a vessel,
the total non-recoverable pressure loss
between the protected equipment and the
pressure relief valve should not exceed 3
percent of the set pressure of the valve
except as permitted in 2.2.3.1 for pilot-operated pressure relief valves. When a
pressure relief valve is installed on a
process line, the 3 percent limit should be
applied to the sum of the loss in the normally non-flowing pressure relief valve
inlet pipe and the incremental pressure
loss in the process line caused by the flow
through the pressure relief valve. The
pressure loss should be calculated using
the rated capacity of the pressure relief
valve. Pressure losses can be reduced
materially by rounding the entrance to the
inlet piping, by reducing the inlet line
length, or by enlarging the inlet piping.
Keeping the pressure loss below 3 percent becomes progressively more difficult
as the orifice size of a pressure relief
valve increases.
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150
Long-radius elbow
Pressure
relief valve
Body drain
(See Note 1)
Nonrecoverable
losses
not more
than 3
percent
of set
pressure
Normal pipe
diameter no less
than valve inlet size
Support to
resist weight
and reaction
forces
Vessel
Low-point drain
(See Note 2)
Notes
1. See Section 6.
2. Orient low-point drain – or weep hole –
away from relief valve, structural steel, and
operating area.
Figure 2 – Typical Pressure Relief
Valve Installation: Closed System
Discharge
Bonnet vent
piping for
bellows type
pressure relief
valves, if
required
(See Note 1)
To closed system
(self-draining)
Flanged spool
piece, if
required to
elevate PRV
Nonrecoverable
pressure losses
not more than 3
percent of set
pressure
Nominal pipe
diameter no
less than
valve inlet
size
Vessel
Note
1. See Section 5.
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Excerpts from API - 520 Part II Installation
Figure 3 – Typical Pressure Relief
Valve Mounted on Process Line
See 2.2.2 for
pressure-loss
limitation
Vessel
The nominal size of the inlet piping must
be the same as or larger than the nominal
size of the pressure relief valve inlet
flange connection as shown in Figure 2.
An engineering analysis of the valve performance at higher inlet losses may permit
increasing the allowable pressure loss
above 3 percent.
Pressure
Relief
Valve
Note
1. See 2.2.2 for pressure-loss limitation.
Figure 4 – Typical Pressure Relief
Valve Mounted on Long Inlet Pipe
Pressure Relief
Valve
Discharge
Piping
Inlet piping sized
so that pressure
drop from vessel
to pressure relief
valve inlet flange
does not exceed
3% of valve set
pressure
2.2.3.2 Installation Guidelines
Remote sensing lines should measure
static pressure where the velocity is low.
Otherwise, the pilot will sense an artificially low pressure due to the effect of
velocity.
Ensure that the pilot sensing point is within the system protected by the main valve.
When a rupture disk device is used in
combination with a pressure relief valve,
the pressure-drop calculation must include
the additional pressure drop developed by
the disk (see 2.6 for additional information
on rupture disk devices).
For flowing pilots, remote sensing lines
shall be sized to limit the pressure loss to
3 percent of the set pressure based on
the maximum flow rate of the pilot at 110
percent of set pressure. Consult the manufacturer for recommendations.
2.2.3 Remote Sensing for Pilot
Operated Pressure Relief Valves
Remote sensing for pilot-operated pressure relief valves can be utilized when
there is excessive inlet pipe pressure loss
or when the main valve must be located at
a pressure source different from the pilot
sensing point because of service limitations of the main valve (see Figure 5).
For non-flowing pilots, remote sensing
lines with a flow area of 0.070 square
inches (45 square millimeters) is sufficient
since no system medium flows through
this type of pilot when the main valve is
open and relieving.
2.2.3.1 Inlet Pipe Loss
Remote sensing permits the pilot to sense
the true system pressure upstream of the
piping loss. Remote sensing may eliminate uncontrolled valve cycling or
chattering for a pop action pressure relief
valve and will permit a modulating action
pressure relief valve to achieve full lift at
the required overpressure. However, high
inlet pressure losses may induce pressure
pulsations in the inlet piping that can
cause uncontrolled main valve cycling.
Some valves incorporate design features
to prevent uncontrolled cycling
Although remote sensing may eliminate
valve chatter or permit a modulating valve
to achieve full lift at the required overpressure, the relieving capacity will be reduced
by any pressure drop in the inlet pipe.
Consider using pipe for remote sensing
lines to ensure mechanical integrity.
If a block valve is installed in the remote
sensing line, the guidelines in Section 4
should be followed. A closed block valve in
a remote sense line renders the pressure
relief valve inoperative.
2.2.4 Configuration of Inlet Piping for
Pressure Relief Valves
Avoid the installation of a pressure relief
valve at the end of a long horizontal inlet
pipe through which there is normally no
flow. Foreign matter may accumulate, or
liquid may be trapped, creating interference with the valve’s operation or requiring
more frequent valve maintenance.
The inlet piping system to relief valves
should be free-draining from the pressure
relief device to prevent accumulation of
liquid or foreign matter in the piping.
Vessel
Note
1. Inlet piping sized so that nonrecoverable
pressure losses form vessel to pressure
relief valve inlet flange do not exceed 3 percent of valve set pressure.
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Excerpts from API - 520 Part II Installation
2.3 Inlet Stresses That Originate
From Static Loads in the Discharge
Piping
ing moments will cause excessive stresses on any of the components in the
system.
Improper design or construction of the discharge piping from a pressure relief
device can set up stresses that will be
transferred to the pressure relief device
and its inlet piping. These stresses may
cause a pressure relief valve to leak or
malfunction or may change the burst pressure of a rupture disk. The pressure relief
device manufacturer should be consulted
about permissible loads and moments.
The magnitude of the reaction force will
differ substantially depending on whether
the installation is open or closed discharge. When an elbow is installed in the
discharge system to direct the fluid up into
a vent pipe, the location of the elbow and
any supports is an important consideration
in the analysis of the bending moments.
2.3.1 Thermal Stresses
Fluid flowing from the discharge of a pressure-relieving device may cause a change
in the temperature of the discharge piping.
A change in temperature may also be
caused by prolonged exposure to the sun
or to heat radiated from nearby equipment. Any change in the temperature of
the discharge piping will cause a change
in the length of the piping and may cause
stresses that will be transmitted to the
pressure relief device and its inlet piping.
The pressure relief device should be isolated from piping stresses through proper
support, anchoring, or flexibility of the discharge piping.
2.3.2 Mechanical Stresses
Discharge piping should be independently
supported and carefully aligned.
Discharge piping that is supported by only
the pressure relief device will induce
stresses in the pressure relief device and
the inlet piping. Forced alignment of the
discharge piping will also induce such
stresses.
2.4.1 Determining Reaction Forces in
an Open Discharge System
The following formula is based on a condition of critical steady-state flow of a
compressible fluid that discharges to the
atmosphere through an elbow and a vertical discharge pipe. The reaction force (F)
includes the effects of both momentum
and static pressure; thus, for any gas, vapor, or steam,
-------------------kT
–––––––
(k + 1)M
√
[Metric Units]
F = 129 W
Main Valve
Pilot
Integral
pressure
sensing
Optional
remote
pressure
sensing
Vessel
Note
1. See 2.2.3.
English Units
W
F = ––––
366
Figure 5 – Typical Pilot-Operated
Pressure Relief Valve Installation
+ (AP)
-------------------kT
––––––– + 0.1 (AP)
(k + 1)M
√
Figure 6 – Typical Pressure Relief
Valve Installation With Vent Pipe
F
Ao
(crosssection
area)
Vent Pipe
Where:
F = reaction force at the point of discharge to the atmosphere, in pounds
[newtons].
W = flow of any gas or vapor, in pounds
per hour [kilograms per second].
Long-radius
Elbow
Pressure
Relief
Valve
k = ratio of specific heats (Cp/Cv).
2.4 Inlet Stresses That Originate
From Discharge Reaction Forces
Cp = specific heat at constant pressure.
The discharge of a pressure relief device
will impose a reaction force as a result of
the flowing fluid (see Figure 6). This force
will be transmitted into the pressure relief
device and also into the mounting nozzle
and adjacent supporting vessel shell unless designed otherwise. The precise
magnitude of the loading and resulting
stresses will depend on the reaction force
and the configuration of the piping system.
The designer is responsible for analyzing
the discharge system to determine if the
reaction forces and the associated bend-
T = temperature at inlet, in degrees
Rankine [in degrees Kelvin].
Free support
to resist weight
and reaction
forces.
Cv = specific heat at constant volume.
Vessel
M = molecular weight of the process
fluid.
A = area of the outlet at the point of discharge, in square inches [square
millimeters].
P = static pressure within the outlet at
the point of discharge, in pounds per
square inch gauge [bar gauge].
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152
Notes
1. The support should be located as close as
possible to the centerline of the vent pipe.
2. F = reaction force
A = cross-sectional area.
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Excerpts from API - 520 Part II Installation
Figure 7 – Typical Rupture Disk
Assembly Installed in Combination
With a Pressure Relief Valve
2.4.2 Determining Reaction Forces in a
Closed-Discharge System
Pressure relief devices that relieve under
steady-state flow conditions into a closed
system usually do not create large forces
and bending moments on the exhaust system. Only at points of sudden expansion
will there be any significant reaction forces
to be calculated. Closed-discharge systems, however, do not lend themselves to
simplified analytic techniques. A complex
time-history analysis of the piping system
may be required to obtain the true values
of the reaction forces and associated moments.
2.5 Isolation Valves in Inlet Piping
Pressure
Gauge
Isolation valves located in the inlet piping
to pressure relief devices shall be in accordance with the guidelines in Section 4.
2.6 Rupture Disk Devices in
Combination with Pressure Relief
Valves
A rupture disk device may be used as the
sole pressure relief device, or it may be installed between a pressure relief valve
and the vessel or on the downstream side
of a pressure relief valve (see Figure 7).
Bleed Valve
Rupture disk
(See Note 1)
Excess Flow Valve (optional)
Figure 8 – Installation Avoiding
Process Laterals Connected to
Pressure Relief Valve Inlet Piping
Aviod process laterals
(See Note 1)
Pressure Relief
Valve
Vessel
For ASME Boiler and Pressure Vessel
Code applications, the capacity of a pressure relief valve used in combination with
a rupture disk mounted as shown in
Figure 7 must be derated by 10 percent
unless that particular combination has a
capacity factor derived from testing as listed in the National Board of Boiler and
Pressure Vessel Inspectors’ publication,
Pressure Relief Device Certifications.
When a rupture disk device is used between the pressure relief valve and the
protected vessel, a pressure indicator,
bleed valve, free vent, or suitable telltale
indicator should be provided to permit detection of disk rupture or leakage. The
user is cautioned that any pressure
buildup between the rupture disk and the
pressure relief valve will increase the vessel pressure at which the rupture disk will
burst.
Only non-fragmenting rupture disk devices
may be used beneath a pressure relief
valve.
Rupture disks are not available in all sizes
at lower pressures; therefore, for these
low-pressure applications the available
rupture disk may have to be larger than
the nominal size of the inlet piping and
pressure relief valve.
Refer to API Recommended Practice 520,
Part I, paragraphs 2.5 (Rupture DisksGeneral) and 2.6 (Rupture Disks in
Combination with Pressure Relief Valves)
for additional information.
2.7 Process Laterals Connected to
Inlet Piping of Pressure Relief
Valves
Process laterals should generally not be
connected to the inlet piping of pressure
relief valves. Exceptions should be analyzed carefully to ensure that the allowable
pressure drop at the inlet of the pressure
relief valve is not exceeded under simultaneous conditions of rated flow through the
pressure relief valve and maximum possible flow through the process lateral (see
Figure 8).
2.8 Turbulence in Pressure Relief
Device Inlets
See 7.3 for information regarding the effects of turbulence on pressure relief
valves.
Section 3 – Discharge Piping From
Pressure Relief Devices
3.1 General Requirements
For general requirements for discharge
piping, see Figures 1, 2, 6, and 9.
The discharge piping installation must provide for proper pressure relief device
performance and adequate drainage (freedraining systems are preferred - see
Section 6). Consideration should be given
to the type of discharge system used, the
back pressure on the pressure relief device, and the set-pressure relationship of
the pressure relief devices in the system.
Auto-refrigeration during discharge can
cool the outlet of the pressure relief device
and the discharge piping to the point that
brittle fracture can occur. Materials must
be selected which are compatible with the
expected temperature.
Note
1. See 2.7.
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3.2 Safe Disposal of Relieving
Fluids
3.6 Isolation Valves in the
Discharge Piping
For a comprehensive source of information about the safe disposal of various
relieving fluids, see API Recommended
Practice 521.
Isolation valves located in the discharge
piping system shall be in accordance with
the guidelines in Section 4.
3.3 Back Pressure Limitations and
Sizing of Pipe
Section 4 – Isolation (stop) Valves
in Pressure Relief Piping
When discharge piping for pressure relief
valves is designed, consider the combined
effect of superimposed and built-up back
pressure on the operating characteristics
of the pressure relief valves. The discharge piping system should be designed
so that the back pressure does not exceed an acceptable value for any
pressure relief valve in the system.
4.1 General
When rupture disks are used as the sole
relieving device and discharge into a
closed system, the effect of the superimposed back pressure on the bursting
pressure for the disk must be considered.
The rated capacity of the pressure relief
valve shall be used to size the discharge
line from the pressure relief valve to the
relief header. Additional information on
sizing of discharge piping systems for vapor or gas service is covered in API
Recommended Practice 521.
3.4 Considerations for PilotOperated Pressure Relief Valves
Superimposed back pressure that exceeds the inlet pressure of a
pilot-operated pressure relief valve can
cause the main valve to open, allowing
reverse flow through the main valve. For
example, backflow can occur if several
pressure relief valves have their outlets
manifolded into a common discharge
header, and one or more of these valves
is discharging while another is connected
to a system with a lower inlet pressure. An
accessory should be specified that will
prevent such backflow.
3.5 Stresses that Originate from
Discharge Piping
The effects of stresses that originate from
discharge piping are discussed in 2.3.1
and 2.3.2.
Block valves may be used to isolate a
pressure relief device from the equipment
it protects or from its downstream disposal
system. Since improper use of block valve
may render a pressure relief device inoperative, the design, installation, and
management of these isolation block
valves should be carefully evaluated to
ensure that plant safety is not compromised.
Figure 9 – Typical Pressure Relief
Valve Installation with an Isolation
Valve
Isolation valve with
provision for car sealing or
locking open (not required
for atmosheric discharge)
(See Note 1)
To closed
system or
atmoshperic
piping
Typical
blinding
points
Bleed valve
installed on
valve body
(See Note 3)
Bleed valve
Isolation valve
with provision
for car sealing
or locking open
Nonrecoverable
pressure
losses not mor
than 3 percent
of set pressure
Flanged spool
piece, if
required to
elevate PRV
4.2 Application
If a pressure relief device has a service
history of leakage, plugging, or other
severe problems which affect its performance, isolation and sparing of the relief
device may be provided. This design strategy permits the pressure relief device to
be inspected, maintained, or repaired
without shutting down the process unit.
However, there are potential hazards associated with the use of isolation valves.
The ASME Boiler and Pressure Vessel
Code, Section VIII, Appendix M, discusses
proper application of these valves and the
administrative controls which must be in
place when isolation block valves are
used. Local jurisdictions may have other
requirements.
Additional examples of isolation valve installations are given in 4.4.
4.3 Isolation Valve Requirements
In addition to previously noted inlet and
outlet pressure drop restrictions, all isolation valves located in relief system piping
shall meet the following requirements:
a. Valves shall be full bore.
b. Valves shall be suitable for the line service classification.
c. Valves shall have the capability of being
locked or carsealed open.
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154
Bonnet vent piping
for bellows type
pressure relief
valves, if required
(See Note 2)
Vessel
d. When gate valves are used, they
should be installed with stems oriented
horizontally or, if this is not feasible, the
stem could be oriented downward to a
maximum of 45° from the horizontal to
keep the gate from falling off and blocking the flow.
Consider painting the isolation valves a
special color or providing other identification.
When isolation valves are installed in
pressure relief valve discharge piping, a
means to prevent pressure buildup between the pressure relief valve and the
isolation valve should be provided (for example, a bleeder valve). Also, the
installation of bleed valves should be considered to enable the system to be
depressured prior to performing maintenance on the system as shown in Figures
9 through 12.
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Excerpts from API - 520 Part II Installation
Figure 10 – Typical Pressure Relief
Valve Installation Arrangement for
100 Percent Spare Relieving
Capacity
To closed (isolation valving
required) or atmosheric
discharge system
Nonrecoverable
pressure
losses not
more than 3
percent of set
pressure
Typical
bleed
valve
Vessel
Consider the installation of an additional
relief device, so that 100 percent design
relieving capacity is available while any
relief device is out of service. Examples of
this type of installation are shown in
Figures 10 and 11. Consider storing the
spare valve until needed to preserve its integrity and allow bench testing just prior to
installation.
When spare relief devices are provided, a
mechanical interlock or interlocking procedure shall be provided which manages
proper opening and closing sequences of
the isolation valves to ensure that overpressure protection of the vessel or
equipment is not compromised. Typically
the inlet isolation valves for spare relief
valves are closed.
Three-way isolation valves are acceptable
provided the installation meets the size
and inlet pressure drop requirements.
4.4 Examples of Isolation Valve
Installations
An isolation valve downstream of a pressure relief device may be installed at
battery limits of process units. This is illustrated in Figure 12. The purpose of battery
limit isolation valves is to allow process
units to be removed from service for maintenance while other process units
discharging into the main plant flare header remain in service.
Similarly, relief system isolation valves
may be used for equipment such as compressors, salt dryers, or coalescers, which
are spared and need to be shut down for
maintenance while spare equipment remains online (see Figure 13).
4.5 Management Procedures
Related to Isolation Valves
Strict management procedures should be
in place that will prohibit the inadvertent
closing of isolation valves in relief piping.
These procedures should require that the
opening and closing of the valves be done
by an authorized person.
An updated list should be kept of all isolation valve located in relief piping which
could isolate relief valves. Documentation
of the required position and reason for the
lock or seal should be provided.
Periodic inspections of isolation valves located in relief piping should be made
which verify the position of valves and the
condition of the locking or sealing device.
Section 5 – Bonnet or Pilot Vent
Piping
5.2 Balanced Bellows Valves
Balanced bellows valves are utilized in applications where it is necessary to
minimize the effect of back pressure on
the set pressure and relieving capacity.
This is done by balancing the effect of the
back pressure on the top and bottom
sides of the disk. This requires the spring
to operate at atmospheric pressure.
The bonnets of bellows valves must always be vented to ensure proper
functioning of the valve and to provide a
tell tale in the even of a bellows failure.
The vent must designed to avoid plugging
caused by ice, insects, or other obstructions. When the fluid is flammable, toxic,
or corrosive, the bonnet vent may need to
be piped to a safe location.
5.3 Balanced Piston Valves
Balanced piston valves are utilized in applications to minimize the effect of back
pressure, similar to the balanced bellows
valve. Proper operation depends on cancellation of the back pressure effect on
opposing faces of the valve disk and balance piston. Since the piston area is equal
to the nozzle seat area, the spring must
operate at atmospheric pressure.
Because of the flow of system media past
the piston, the bonnets of balanced piston
valves should always be vented to atmosphere at a safe location. The amount of
flow past the piston into the bonnet depends on the pressure differential
between the valve outlet and bonnet. In
an installation where superimposed back
pressure of built-up back pressure is high,
the flow past the piston could be substantial. This factor must be considered in the
design of the bonnet venting.
5.1 Conventional Valves
The two types of conventional valves are:
a. Open spring, often used in steam service.
b. Closed spring, where the bonnet enclosing the spring is vented internally to
the pressure relief valve discharge. The
bonnet normally has a tapped vent that
is closed off with a threaded plug.
5.4 Pilot-Operated Valves
The pilot is often vented to the atmosphere
under operating conditions, since the discharge during operation is small. When
vent discharge to the atmosphere is not
permissible, the pilot should be vented either to the discharge piping or through a
supplementary piping system to a safe location. When vent piping is designed, avoid
the possibility of back pressure on the pilot
unless the pilot is a balanced design.
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Section 6 – Drain Piping
6.1 Installation Conditions that
Require Drain Piping
Drain piping is normally not required on
pressure relief valves at the valve body
connection provided for this purpose. The
outlet piping to closed systems should be
self-draining to a liquid disposal point,
thereby eliminating the need for a drain
from the valve. Drainage must be provided when the discharge is not self-draining
and the valve is located where liquids
could accumulate at the valve outlet.
6.2 Safe Practice for Installation of
Drain Piping
Since drain piping becomes part of the entire venting system, precautions that apply
to the discharge system apply similarly to
the drain piping. The drain-piping installation must not adversely affect the valve
performance, and flammable, toxic, or corrosive fluids must be piped to a safe
location.
Section 7 – Pressure Relief Device
Location and Position
7.1 Inspection and Maintenance
For optimum performance, pressure relief
devices must be serviced and maintained
regularly. Details for the care and servicing of specific pressure relief devices are
provided in the manufacturer's maintenance bulletins and in API Recommended
Practice 576. Pressure relief devices
should be located for easy access, removal, and replacement so that servicing
can be properly handled. Sufficient working space should be provided around the
pressure relief device.
7.2 Proximity to Pressure Source
The pressure relief device should normally
be placed close to the protected equipment so that the inlet pressure losses to
the device are within the allowable limits.
For example, where protection of a pressure vessel is involved, mounting the
pressure relief device directly on a nozzle
on top of the vessel may be necessary.
However, on installations that have pressure fluctuations at the pressure source
(as with valves on a positive displacement
compressor discharge) that peak close to
the set pressure of the pressure relief
valve or burst pressure of a rupture disk,
the pressure relief device should be located farther from the source and in a more
stable pressure region. (See Section 2 for
information related to this subject.)
Figure 12 – Typical Flare Header
Block Valves
Battery
limit
7.3 Proximity to Other Equipment
Pressure relief devices should not be located where unstable flow patterns are
present (see Figure 14). The branch entrance where the relief device inlet piping
joins the main piping run should have a
well-rounded, smooth corner that minimizes turbulence and resistance to flow.
To main
flare header
Pressure relief
valve installation
(See Note 4)
When pressure relief branch connections
are mounted near equipment that can
cause unstable flow patterns, the branch
connection should be mounted downstream at a distance sufficient to avoid the
unstable flow. Examples of devices that
cause unstable flow are discussed in 7.3.1
through 7.3.3.
7.3.1 Reducing Stations
Pressure relief devices are often used to
protect piping downstream from pressure
reducing valves, where unstable flow usually occurs. Other valves and
appurtenances in the system may also
disturb the flow. This condition cannot be
evaluated readily, but unstable flow at
valve inlets tends to generate instability.
7.3.2 Orifice Plates and Flow Nozzles
Proximity to orifice plates and flow nozzles
may cause adverse operation of the pressure relief devices.
7.3.3 Other Valves and Fittings
Proximity to other fittings, such as elbows,
may create turbulent areas that could result in adverse performance of pressure
relief devices.
7.4 Mounting Position
Pressure relief valves should be mounted
in a vertical upright position. Installation of
a pressure relief valve in other than a vertical upright position may adversely affect
its operation. The valve manufacturer
should be consulted about any other
mounting position, since mounting a pressure relief valve in other positions may
cause a shift in the set pressure and a reduction in the degree of seat tightness.
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156
Process unit flare header
block valve (See Note 1)
Process unit relief header
(self draining)
Isolation blind point
(See Note 2)
Pressure
vessel A
Pressure
vessel B
Pressure relief valve
installation (See Note 3)
Notes
1.
2.
3.
4.
See 4.4.
See Figure 8.
See Figures 10 and 11.
See Figures 2 and 9.
Additionally, another position may permit
liquids to collect in the spring bonnet.
Solidification of these liquids around the
spring may interfere with the valve operation.
7.5 Test or Lifting Levers
Test or lifting levers should be provided on
pressure relief valves as required by the
applicable code. Where simple levers are
provided, they should hang downward,
and the lifting fork must not contact the lifting nuts on the valve spindle. Uploads
caused by the lifting-mechanism bearing
on the spindle will cause the valve to open
below the set pressure. The lifting mechanism should be checked to ensure that it
does not bind on the valve spindle.
Where it is necessary to have the test
lever in other than a vertical position, or
where the test lever is arranged fro remote
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Excerpts from API - 520 Part II Installation
Figure 13 – Typical Isolation Block Valves for Spare Compressor
Pulsation dampners
From spare
compressor
Isolation block valves (See Note 1)
Compressor relief headers
Isolation blind points
Bleed valve
1
First stage
2
Second stage
3
Process unit
flare header
Third stage
Note
1. See 4.4.
manual operation, the lever should be
counterbalanced so that the lifting mechanism, unless actuated, does not exert any
force on the valve spindle lifting nut.
In lieu of lifting levers for pilot-operated
pressure relief valves, means may be
specified for connecting and applying adequate pressure to the pilot to verify that
the moving parts critical to proper operation are free to move.
7.6 Heating Tracing and Insulation
For materials which are highly viscous,
could result in corrosion upon cooling,
or could potentially solidify in pressure
relief valves, adequate heat tracing or insulation should be provided for both inlet
and outlet piping. Ensure that the valve
nameplate and any discharge vent port are
not covered when the valve is insulated.
Section 8 – Bolting and Gasketing
8.1 Care in Installation
Before a pressure relief device is installed,
the flanges on the pressure relief valve or
rupture disk holder and the mounting noz-
zle should be thoroughly cleaned to remove any foreign material that may cause
leakage. Where pressure relief devices
are too heavy to be readily lifted by hand,
the use of proper handling devices will
avoid damage to the flange gasket facing.
Ring joint and tongue-and-groove facings
should be handled with extreme care so
that the mating sections are not damaged.
8.2 Proper Gasketing and Bolting
for Service Requirements
The gasket used must be dimensionally
correct for the specific flanges; they must
fully clear the pressure relief device inlet
and outlet openings.
Gaskets, flange facings, and bolting
should meet the service requirements for
the pressure and temperature involved.
This information can be obtained by referring to other national standards and to
manufacturers’ technical catalogs.
When a rupture disk device is installed in
the pressure relief system, the flange gasket material and bolting loads may be
critical. The disk manufacturer’s instructions should be followed for proper
performance.
Section 9 – Multiple Pressure
Relief Valves with Staggered
Settings
Normal practice is to size a single pressure relief valve to handle the maximum
relief from a piece of equipment. However,
for some systems, only a fraction of that
amount must be relieved through the
pressure relief valve during mild upsets. If
the fluid volume under a pressure relief
valve is insufficient to sustain the flow, the
valve operation will be cyclic and will result in poor performance. The valve's
ability to reseat tightly may be affected.
When capacity variations are frequently
encountered in normal operation, one alternate is the use of multiple, smaller
pressure relief valves with staggered settings. With this arrangement, the pressure
relief valve with the lowest setting will be
capable of handling minor upsets, and additional pressure relief valves will be put in
operation as the capacity requirement increases.
For inlet piping to multiple relief valves,
the piping which is common to multiple
valves must have a flow area which is at
least equal to the combined inlet areas of
the multiple pressure relief valves connected to it.
Refer to API Recommended Practice 520,
Part I, to determine set pressure of the
pressure relief valves based on maximum
allowable pressure accumulation for multiple valve installations.
An alternate to the use of multiple pressure relief valves with staggered settings
is the use of a modulating pilot-operated
relief valve.
Section 10 – Preinstallation
Handling and Inspection
10.1 Storage and Handling of
Pressure Relief Devices
Because cleanliness is essential to the
satisfactory operation and tightness of a
pressure relief valve, take precautions to
keep out all foreign materials. Valves
should be closed off properly at both inlet
and outlet flanges. Take particular care to
keep the valve inlet absolutely clean.
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API - RP 520 Part II (July 1991) - Valve Installation
Excerpts from API - 520 Part II Installation
Pressure relief valves should, when possible, be stored indoors on pallets away
from dirt and other forms of contamination.
Pressure relief devices should be handled
carefully and should not be subjected to
shocks, which can result in considerable
internal damage or misalignment. For
valves seat tightness may be adversely
affected. Ruptured disks should be stored
in the original shipping container.
10.2 Inspection and Testing of
Pressure Relief Valves
The condition of all pressure relief valves
should be visually inspected before installation. Consult the manufacturer’s
instruction manuals for details relating to
the specific valve. Ensure that all protective material on the valve flanges and any
extraneous materials inside the valve
body and nozzle are completely removed.
Bonnet shipping plugs must be removed
from balanced pressure relief valves. The
inlet surface must be cleaned, since foreign materials clinging to the inside of the
nozzle will be blown across the seats
when the valve is operated. Some of
these materials may damage the seats or
get trapped between the seats in such a
way that they cause leakage. Valves
should be tested before installation to confirm set pressure.
10.3 Inspection of Rupture Disk
Devices
All rupture disk devices should be thoroughly inspected before installation,
according to the manufacturer’s instruction manuals. The seating surfaces of the
rupture disk holder must be clean,
smooth, and undamaged.
Rupture disks should be checked for
physical damage to the seating surfaces
or the prebulged disk area. Damaged or
dented disk should not be used. Apply the
proper installation and torquing procedure
as recommended by the rupture disk device manufacturer.
Figure 14 – Typical Installation
Avoiding Unstable Flow Patterns at
Pressure Relief Valve Inlet
On reverse-buckling disk that have knifeblade assemblies, the knife blades must
be checked for physical damage and
sharpness. Nicked or dull blades must not
be used. Damaged rupture disk holders
must be replaced.
10.4 Inspection and Cleaning of
Systems Before Installation
Because foreign materials that pass into
and through pressure relief valves can
damage the valve, the systems on which
the valves are tested and finally installed
must also be inspected and cleaned. New
systems in particular are prone to contain
welding beads, pipe scale, and other foreign objects that inadvertently get trapped
during construction and will destroy the
seating surface when the valve opens.
The system should be thoroughly cleaned
before the pressure relief valve is installed.
Pressure relief devices should be removed or isolated before hydrotesting or
pneumatic pressure testing of the system,
either by blanking or closing an isolation
valve. If an isolation valve is used, the
flange at the pressure relief device should
be wedged open or a bleed valve provided so that inadvertent leaking through the
isolation valve does not damage the pressure relief device.
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158
Inlet
flanges
Inlet pipe
Rounded
entry branch
connection
Run Pipe
Flow
D
Note
1. D is typically not less than 10 pipe diameters
from any device that causes unstable flow.
Anderson Greenwood Pressure Relief Valves
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Following is an Excerpt from NACE MR0175-95,
API - RP 521, and API - RP 527
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159
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NACE MR0175-95 Excerpts on Valve Materials
Section 3: Ferrous Metals
Ferrous metals shall meet the requirements of this section if they are to be
exposed to sour environments (defined in
Paragraph 1.3).
3.1 General
The susceptibility to SSC of most ferrous
metals can be strongly affected by heat
treatment, cold work, or both. The following paragraphs describe heat treatments
for specific materials that have been found
to provide acceptable resistance to SSC.
3.2 Carbon and Low-Alloy Steels
3.2.1 All carbon and low-alloy steels are
acceptable at 22 HRC maximum hardness
provided they (1) contain less than 1%
nickel, (2) meet the criteria of Paragraphs
3.2.2, 3.3, and Section 5, and (3) are used
in one of the following heat-treat conditions:
(a) hot-rolled (carbon steels only);
(b) annealed;
(c) normalized;
(d) normalized and tempered;
(e) normalized, austenitized, quenched,
and tempered; or
(f) austenitized, quenched, and
tempered.
3.2.1.1 Forgings produced in accordance
with the requirements of ASTM A 105 are
acceptable, provided the hardness does
not exceed 187 HB maximum.
as described in NACE Standard TM0177
are accepted test specimens. Any of these
specimens may be used.
(2) A minimum of three specimens from
each of three different commercially prepared heats must be tested in the
(heat-treated) condition balloted for
MR0175 inclusion. The composition of
each heat and the heat treatment(s) used
shall be furnished as part of the ballot.
The candidate material’s composition
range and/or UNS number and its heattreated condition requested for inclusion in
MR0175 must be included with the ballot.
(3) The Rockwell hardness of each specimen must be determined and reported as
part of the ballot. The average hardness of
each specimen shall be the hardness of
that specimen. The minimum specimen
hardness obtained for a given heat/condition shall be the hardness of that heat/
condition for the purpose of balloting. The
maximum hardness requested for inclusion of the candidate material in MR0175
must be specified in the ballot and should
be supported by the data provided.
(4) Further, in order for the material/ condition to be considered for acceptance, it is
required that, for each of the commercial
heats tested, stress intensity values, etc.
(as applicable to the test method used), of
all tests shall also be reported as part of
the ballot item when submitted.
3.2.1.2 Acceptance criteria: Wrought carbon and low-alloy steels with a hardness
greater than HRC 22 that are not otherwise covered by this materials
requirement standard must meet the following minimum criteria for balloting prior
to inclusion in this document. These criteria are necessary but may not be sufficient
conditions for inclusion in all cases.
3.2.2 The metal must be thermally stress
relieved following any cold deforming by
rolling, cold forging, or another manufacturing process that results in a permanent,
outer fiber deformation greater than 5%.
Thermal stress relief shall be performed in
accordance with the ASME Code, Section
VIII, Division I, except that the minimum
stress relief temperature shall be 595°C
(1100°F). The component shall have a
hardness of 22 HRC maximum.
(1) The candidate steel must be tested in
accordance with the test procedures established in NACE Standard TM0177
(latest revision). The tensile bar, O-ring,
bent beam, and double cantilever beam
3.2.2.1 This requirement does not apply to
pipe grades listed in Table 3 or cold work
imparted by pressure testing per the applicable code. Cold-rotary straightened
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160
pipe is acceptable only where permitted in
API specifications. Cold-worked line pipe
fittings of ASTM A 53 Grade B, ASTM A
106 Grade B, API 5L Grade X-42, or
lower-strength grades with similar chemical compositions are acceptable with cold
strain equivalent to 15% or less, provided
the hardness in the strained area does not
exceed 190 HB.
3.2.3 Tubulars and tubular components
made of low-alloy steels in the Cr, Mo series (AISI 41XX and its modifications) are
acceptable at a 26 HRC maximum hardness, provided they are in the quenched
and tempered condition.
3.2.3.1 Careful attention to chemical composition and heat treatment is required to
ensure SSC resistance of these alloys at
greater than 22 HRC. Accordingly, it is
common practice, when using these alloys
at above 22 HRC, for the user to conduct
SSC tests (in accordance with Paragraph
1.6) to determine that the material is
equivalent in SSC performance to similar
materials that have given satisfactory service in sour environments.
3.2.3.2 If tubulars and tubular components
are cold straightened at or below 510°C
(950°F), they shall be stress relieved at a
minimum of 480°C (900°F).
3.3 Free Machining Steels
3.3.1. Free-machining steels shall not be
used.
3.4 Cast Iron
3.4.1 Gray, austenitic, and white cast irons
are not acceptable for use as a pressurecontaining member. These materials may
be used in internal components related to
API and other appropriate standards, provided their use has been approved by the
purchaser.
3.4.2 Ferritic ductile iron ASTM A 395
is acceptable for equipment when API,
ANSI, and/or other industry standards
approve its use.
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NACE MR0175-95 Excerpts on Valve Materials
3.5 Austenitic Stainless Steels1
3.5.1 Austenitic stainless steels with
chemical compositions as specified in
accordance with the standards listed in
Table 1, either cast or wrought, are acceptable at a hardness of 22 HRC
maximum in the annealed condition provided they are free of cold work designed
to enhance their mechanical properties.
3.5.2 Austenitic stainless steel UNS
S20910 is acceptable at 35 HRC maximum
hardness in the annealed or hot-rolled
(hot/cold-worked) condition, provided it is
free of subsequent cold work designed to
enhance its mechanical properties.
3.5.3 Austenitic stainless steel alloy UNS
N08020 is acceptable in the annealed or
cold-worked condition at a hardness level
of 32 HRC maximum.
3.5.5 Wrought austenitic stainless steel
UNS S31254 is acceptable in the annealed or cold-worked condition at a
hardness level of 35 HRC maximum.
3.5.6 Austenitic stainless steel UNS
N08367 is acceptable in the absence of
free elemental sulfur at 22 HRC or less at
temperatures below 150°C (302°F) when
the salinity does not exceed 5,000 mg/L
and the H2S partial pressure does not exceed 0.31 MPa (45 psia).
3.6 Ferritic Stainless Steels
3.6.1 Ferritic stainless steels are acceptable at a 22 HRC maximum hardness,
provided they are in the annealed condition and meet the criteria of Section 5.
Acceptable ferritic stainless steels are listed in Table 1.
3.7 Martensitic Stainless Steels 2
3.5.4 Cast CN7M meeting ASTM A 351, A
743, or A 744 is acceptable for nondownhole applications in the following
conditions (there are no industry standards that address these melting and
casting requirements):
(1) solution-annealed at 1121°C (2050°F)
minimum or solution-annealed at 1121°C
(2050°F) minimum and welded with AWS
E320LR or ER320LR;
(2) the castings must be produced from
argon-oxygen decarburization (AOD) refined heats or remelted AOD refined
heats. The use of scraps, such as turnings,
chips, and returned materials is prohibited
unless melting is followed by AOD refining;
(3) the CN7M composition listed in ASTM
A 351, A 743, or A 744 shall be further restricted to 0.03 percent maximum carbon,
1.00% maximum silicon, 3.0 to 3.5% copper, 0.015% maximum sulfur, 0.030%
maximum phosphorous, and 0.05 percent
maximum aluminum; and
3.7.1 Martensitic stainless steels, as listed
in Table 1, either cast or wrought, are acceptable at 22 HRC maximum hardness
provided they are heat treated per
Paragraph 3.7.1.1 and meet the criteria of
Section 5. Martensitic stainless steels that
are in accordance with this standard have
provided satisfactory field service in some
sour environments. These materials may,
however, exhibit threshold stress levels in
NACE Standard TM0177 that are lower
than those for other materials included in
this standard.
3.7.1.1 Heat-Treat Procedure (Three-Step
Process)
(1) Normalize or austenitize and quench.
(2) Temper at 620°C (1150°F) minimum;
then cool to ambient temperature.
(3) Temper at 620°C (1150°F) minimum,
but lower than the first tempering temperature, then cool to ambient temperature.
3.7.1.2 Subsequent to cold deformation
(see Paragraph 3.2.2) the material shall
be furnace stress relieved at 620°C
(1150°F) minimum to 22 HRC maximum
hardness.
3.7.2 Low-Carbon Martensitic Stainless
Steels
3.7.2.1 Cast and wrought low-carbon
martensitic stainless steels meeting the
chemistry requirements of ASTM A 487
Grade CA6NM and UNS S42400 are acceptable to HRC 23 maximum provided
they are heat treated per Paragraph
3.7.2.1.1.3
3.7.2.1.1 Heat-Treat Procedure (ThreeStep Process)
(1) Austenitize at 1010°C (1850°F) minimum and air or oil quench to ambient
temperature;
(2) Temper at 648° to 690°C (1200° to
1275°F) and air cool to ambient temperature;
(3) Temper at 593° to 620°C (1100° to
1150°F) and air cool to ambient temperature.
3.8 Precipitation-Gardening
Stainless Steels 1
3.8.1 Wrought UNS S17400 martensitic
precipitation-hardening stainless steel is
acceptable at 33 HRC maximum hardness
provided it has been heat treated in
accordance with Paragraph 3.8.1.1 or
Paragraph 3.8.1.2. Precipitation-hardening
martensitic stainless steels that are in accordance with this standard have provided
satisfactory field service in some sour
environments. These materials may, however, exhibit threshold stress levels in
NACE Standard TM0177 that are lower
than those of other materials included in
this standard.
(4) at a hardness level of 22 HRC
maximum.
Notes
1. These materials may be subject to chloride
SCC in certain environments.
2. Valve manufacturers generally do not use
these material for valve stems or other highly stressed components in sour service.
3. The hardness correlation tabulated in ASTM
E 140 does not apply to CA6NM or UNS
S42400. When hardness is measured in
Brinell units, the permissible BHN limit is
255 maximum, which has been empirically
determined to be equivalent to HR 23 for
these alloys.
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NACE MR0175-95 Excerpts on Valve Materials
3.8.1.1 Double Age at 620°C (1150°F).
(1) Solution anneal;
Section 4: Nonferrous Metal 4–6
(1) Solution anneal at 1040°C ± 14°C
(1900°F ± 25°F) and air cool, or suitable
liquid quench, to below 32°C (90°F).
(2) Precipitation harden at 620°C (1150°F)
minimum for 4 hours.
4.1 General.
(2) Harden at 620°C ± 14°C (1150°F ±
25°F) for 4 hours minimum and cool in air.
(3) Cool material to below 32°C (90°F) before the second precipitation-hardening
step.
(4) Harden at 620°C ± 14°C (1150°F ±
25°F) for 4 hours minimum at temperature
and cool in air.
3.8.1.2 Heat-Treat Procedure (Three-Step
Process)
(1) Solution anneal at 1040°C ± 14°C
(1900°F ± 25°F) and air cool, or suitable
liquid quench, to below 32°C (90°F).
(2) Harden at 760°C ± 14°C (1400°F ±
25°F) for 2 hours minimum at temperature
and cool in air to below 32°C (90°F) before second precipitation-hardening step.
(3) Precipitation harden at 620°C ± 14°C
(1150°F ± 25°F) for 4 hours minimum at
temperature and cool in air.
3.8.2 Austenitic precipitation-hardening
stainless steel with chemical composition
in accordance with UNS S66286 is acceptable at 35 HRC maximum hardness
provided it is in either the solution-annealed and aged or solution annealed and
double-aged condition.
3.8.3 Wrought UNS S45000 martensitic
precipitation-hardening stainless steel is
acceptable at 31 HRC maximum hardness
provided it has been heat treated per
Paragraph 3.8.3.1
3.9 Duplex Stainless Steels1
3.9.1 The wrought duplex (austenitic/ferritic) stainless steels listed in Table 1 are
acceptable 28 HRC maximum in the solution-annealed condition.
3.9.2 The cast duplex (austenitic/ferritic)
stainless steel Z6CNDU20.08M, NF A
320-55 French National Standard is acceptable at hardness levels of 17 HRC
maximum in the annealed and quenched
condition provided the ferrite content is
25 to 40%. The annealing shall be at a
temperature of 1150°C ± 10°C (2100°F
± 20°F) and shall be followed by a rapid
quench to avoid the precipitation of sigma
phase.
3.9.3 Wrought duplex stainless steel UNS
S32404 (0.1% to 0.2% nitrogen) is acceptable at 20 HRC maximum in the
solution-annealed condition.
3.9.4 Solution-annealed and cold-worked
UNS S31803 is acceptable for use at any
temperature up to 232°C (450°F) in sour
environments if the partial pressure of hydrogen sulfide does not exceed 0.002
MPa (0.3 psia), the yield strength
of the materials is not greater than 1100
MPa (160 ksi) and its hardness is not
greater than 36 HRC.
3.9.5 Wrought duplex stainless steel UNS
S32750 is acceptable at 32 maximum in
the solution-annealed condition in sour
environments up to 232°C (450°F) if the
H2S partial pressure does not exceed
0.010 MPa (1.5 psia).
3.8.3.1 Heat-Treat Procedure (Two-Step
Process)
Notes
4. These materials may be subject to SCC failure when highly stressed and exposed to
sour environments or some well-stimulating
acids either with or without inhibitors.
5. Some of the materials in the wrought condition may be susceptible to failure by
hydrogen embattlement when strengthened
by cold work and stressed in the transverse
direction.
6. Plastic deformation in service may increase
the SSC susceptibility of these alloys.
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162
Nonferrous metal referenced in this section and meeting the stated requirements
for both condition and hardness are acceptable for use in sour environments (defined
in Paragraph 1.3). See also Table 2.
4.1.1 Nickel-Copper Alloys
4.1.1.1 UNS N04400, ASTM A 494 Grades
M-35-1 and M-35-2, and UNS N04405 are
acceptable to 35 HRC maximum.
4.1.1.2 UNS N05500 is acceptable to 35
HRC maximum in each of the three following conditions: (1) hot-worked and
age-hardened; (2) solution-annealed; and
(3) solution-annealed and age-hardened.
4.1.2 Nickel-lron Chromium Alloys
4.1.2.1 UNS N08800 is acceptable to 35
HRC maximum.
4.1.3 Nickel-lron-Chromium-Molybdenum
Alloys
4.1.3.1 UNS N08825, UNS N06007, and
wrought UNS N06975 are acceptable to
35 HRC maximum; UNS N06950 is acceptable to 38 HRC maximum; and UNS
N06985 is acceptable to HRC 39 maximum.
4.1.3.2 UNS N09925 is acceptable in
each of the five following conditions: (1)
cold-worked to 35 HRC maximum; (2) solution-annealed to 35 HRC maximum; (3)
solution-annealed and aged to 38 HRC
maximum; (4) cold-worked and aged to 40
HRC maximum; and (5) hot-finished and
aged to 40 HRC maximum.
4.1.3.3 UNS N08024 to 32 HRC maximum.
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NACE MR0175-95 Excerpts on Valve Materials
4.1.3.4 UNS N08028 in the solution-annealed and cold-worked condition to 33
HRC maximum.
N06022 is acceptable in the solutionannealed or solution-annealed plus coldworked conditions to 40 HRC maximum.
4.1.3.5 Nickel-iron-chromium-molybdenum-tungsten alloy UNS N06030 is
acceptable in the solution-annealed or
solution-annealed plus cold-worked condition to a maximum hardness of HRC 41.
4.1.5.2.1 Alloy UNS N10276 is also acceptable in the cold-worked and unaged
condition at 45 HRC maximum when used
at a minimum temperature of 121°C
(250°F).
4.1.3.6 UNS N07048 is acceptable in the
solution annealed, solution-annealed and
aged, or direct-aged condition to HRC 4O
maximum.
4.1.5.3 Wrought UNS N07718 is acceptable in each of the five following
conditions: (1 ) solution-annealed to 35
HRC maximum; (2) hot-worked to 35 HRC
maximum; (3) hot-worked and aged to 35
HRC maximum; (4) solution-annealed and
aged to 40 HRC maximum; and (5) cast,
solution-annealed, and aged condition to
40 HRC maximum.
4.1.3.7 UNS N08535 is acceptable in the
solution-annealed and cold-worked condition to 35 HRC maximum.
4.1.3.8 Wrought UNS N08042 is acceptable in the solution-annealed or
solution-annealed plus cold-worked conditions to HRC 31 maximum when the
service environment does not contain elemental sulfur.
4.1.3.9 UNS N06952 is acceptable in the
solution-annealed or solution-annealed
plus cold-worked conditions to 35 HRC
maximum when the service environment
does not contain elemental sulfur.
4.1.4 Nickel-Chromium Alloys
4.1.4.1 UNS N06600 is acceptable to 35
HRC maximum.
4.1.4.2 UNS NO7750 is acceptable to 35
HRC maximum in each of the four following conditions: (1) solution-annealed and
aged; (2) solution-annealed; (3) hotworked; and (4) hot-worked and aged.
4.1.5 Nickel-Chromium-Molybdenum
Alloys
4.1.5.1 UNS N06002 and UNS N06625
are acceptable to 35 HRC maximum.
4.1.5.2 UNS N10002, UNS N10276, and
ASTM A494 Grade CW-12 MW are acceptable in the solution-annealed or
solution-annealed plus cold-worked conditions to 35 HRC maximum (except as
noted in Paragraph 4.1.5.2.1). Alloy UNS
4.1.5.4 UNS N07031 is acceptable in
each of the two following conditions: (1)
solution-annealed condition to 35 HRC
maximum; and (2) solution-annealed and
aged at 760° to 870°C (1400° to 1600°F)
for a maximum of 4 hours to 40 HRC
maximum.
4.1.5.5 UNS N06110 and wrought UNS
N06060 are acceptable in the annealed or
cold-worked conditions to 40 HRC maximum.
4.1.5.6 UNS N07716 and wrought UNS
N07725 are acceptable to 40 HRC maximum in the solution annealed and aged
condition.
4.1.5.7 UNS N07626, totally dense hot
compacted by a powder metallurgy
process, is acceptable in the solution-annealed (925°C [11700°F] minimum) plus
aged condition (525°C to 825°C [1000°F
to 1500°F]) or the direct-aged (525°C to
825°C [1000°F to 1500°F]) condition to a
maximum hardness of HRC 40 and a
maximum tensile strength of 1380 MPa
(200 ksi).
4.1.5.8 Cast CW2M meeting ASTM A 494
is acceptable for nondownhole applications in the following conditions (there are
no industry standards that currently ad-
dress these melting and casting requirements):
(1) solution-annealed at 1232 ± 14°C
(2250°F ± 25°F) or solution-annealed at
1232°C ± 14 °C (2250°F ± 25°F) and
welded with AWS ENiCrMo-7, ERNiCrMo7, ENiCrMo-10, or ERNiCrMo-10;
(2) the castings must be produced by argon-oxygen decarburization (AOD)
refined heats, remelted AOD refined
heats, or virgin remelt stock. The use of
scrap, such as turnings, chips, and returned material is prohibited unless
followed by AOD refining;
(3) the CW2M composition listed in ASTM
A 494 shall be further restricted to 0.015%
maximum sulfur and 0.05% maximum aluminum; and
(4) at a hardness level of 22 HRC maximum.
4.1.6 Cobalt-Nickel-ChromiumMolybdenum Alloys
4.1.6.1 Alloys UNS R30003, UNS
R30004, UNS R30035, and British
Standard, Aerospace Series HR3 are
acceptable at 35 HRC maximum except
when otherwise noted.
4.1.6.2 In addition, UNS R30035 is acceptable at 51 HRC maximum in the
cold-reduced and high-temperature aged
heat-treated condition in accordance with
one of the following aging treatments:
Minimum Time (hours)
Temperature
4
704°C (1300°F)
4
732°C (1350°F)
6
774°C (1425°F)
4
788°C (1450°F)
2
802°C (1475°F)
1
816°C (1500°F)
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4.1.6.3 Wrought UNS R31233 is
acceptable in the solution-annealed condition to 22 HRC maximum.
4.2.1.4.5 Wrought UNS L56403 is acceptable in the annealed condition to 36 HRC
maximum.
4.1.7 Cobalt- Nickel-Chromium-Tungsten
Alloy
codes. Welders using this procedure shall
be familiar with the procedure and shall
be capable of making welds that comply
with the procedure.
Section 5: Fabrication
5.3.1.1 Tubular products listed in Table 3
with specified minimum yield strength of
360 MPa (52 ksi) or less and pressure
vessel steels classified as P-No 1, Group
1 or 2, in Section 9 of the ASME Code
and listed in Table 3 meet the requirements of Paragraph 5.3.1 in the
as-welded condition. Welding procedure
qualifications, per AWS, API, ASME, or
other appropriate specifications shall be
performed on any welding procedure that
is used.
4.1.7.1 UNS R30605 to 35 HRC
maximum.
4 .2 Other Alloys
4.2.1 Materials described in this section
and listed in Table 2 are acceptable.
4.2.1.1 Aluminum-base alloys
4.2.1.2 Copper alloys 7
4.2.1.3 Commercially pure tantalum. UNS
R05200 is acceptable in the annealed and
gas tungsten arc-welded annealed conditions to 55 HRB maximum.
4.2.1.4 Titanium alloys. Specific guidelines must be followed for successful
applications of each titanium alloy specified in this standard. For example,
hydrogen embrittlement of titanium alloys
may occur if galvanically coupled to certain active metals (i.e., carbon steel) in
H2S-containing aqueous media at temperatures greater than 80°C (176°F). Some
titanium alloys may be susceptible to
crevice corrosion and/or SCC in chloride
environments. Hardness has not been
shown to correlate with susceptibility to
SSC. However, hardness has been included for alloys with high strength to
indicate the maximum testing levels
where failure has not occurred.
4.2.1.4.1 UNS R53400 is acceptable in the
annealed condition. Heat treatment shall
be annealing at 774°C ± 14°C (1425°F ±
25°F) for 2 hours followed by air cool.
Maximum hardness to be 92 HRB.
4.2.1.4.2 UNS R58640 is acceptable to 42
HRC maximum.
4.2.1.4.3 UNS R50400 is acceptable to
100 HRB maximum.
4.2.1.4.4 UNS R56260 is acceptable to 45
HRC maximum in each of the three following
conditions: (1) annealed; (2) solution-annealed; and (3) solution-annealed and aged.
5.1 General
Materials and fabrication processes shall
meet the requirements of this section if
the material is to be exposed to sour environments (defined in Paragraph 1.3).
5.2 Overlays
5.2.1 Overlays applied to carbon and lowalloy steel or to martensitic stainless
steels by thermal processes such as welding, silver brazing, or spray metallizing
systems are satisfactory for use in sour environments, provided the substrate does not
exceed the lower critical temperature during
application. In those cases in which the
lower critical temperatures are exceeded,
the component must be heat treated or
thermally stress relieved according to procedures that have been shown to return the
base metal to 22 HRC maximum.
5.2.2 Tungsten-carbide alloys and ceramics are satisfactory, subject to the
conditions of Paragraph 5.2.1.8
5.2.3 Joining of dissimilar materials, such
as cemented to alloy steels by silver brazing, is acceptable. The base metal after
brazing shall meet the requirements of
Paragraph 5.2.1.
5.2.4 The materials listed in Sections 3
and 4 are acceptable as weld overlays,
provided they meet the provisions of
Paragraph 5.2.1.
5.2.5 Overlays of cobalt-chromium-tungsten alloys or nickel-chromium-boron
hardfacing alloys are acceptable, subject
to the conditions of Paragraph 5.2.1.8
5.3 Welding
5.3.1 Welding procedures shall be used to
produce weldments that comply with the
hardness requirements specified for the
base metal in Sections 3 and 4. Welding
procedures shall be qualified per AWS,
API, ASME, or other appropriate industry
Notes
7. Copper-base alloys may undergo weight
loss corrosion in sour oilfield environments,
particularly if oxygen is present.
8. Denotes editorial revision.
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designs and specifications without notice.
164
5.3.1.2 Welding procedure qualifications
on carbon steels that use controls other
than thermal stress relieving to control the
hardness of the weldment shall also include a hardness traverse across the
weld, HAZ and base metal to ensure that
the procedure is capable of producing a
hardness of 22 HRC maximum in the condition in which it is used.
5.3.1.3 Low-alloy steel and martensitic
stainless steel weldments shall be stress
relieved at a minimum temperature of
620°C (1150°F) to produce a hardness of
22 HRC maximum.
5.3.2 Welding rods, electrodes, fluxes,
filler metals, and carbon and low-alloy
steel welding consumables with more
than 1% nickel are not allowed for welding
carbon and low-alloy steels as indicated in
Paragraph 3.2.1.
5.4 Identification Stamping
5.4.1 Identification stamping using lowstress (dot, vibratory, and round V)
stamps is acceptable.
5.5.2 Conventional sharp V stamping is
acceptable in low-stress areas, such as
the outside diameter of flanges. Sharp V
stamping is not permitted in high-stress
areas unless subsequently stress relieved
at 595°C (1100°F) minimum.
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NACE MR0175-95 Excerpts on Valve Materials
5.5 Threading
6.2.1.1 Class I and Class II Nuts and Bolts
Section 8: Special Components
5.5.1 Machine-Cut Threads
6.2.1.1.1 Acceptable nuts and bolting materials shall meet the requirements of
Sections 3 and 4.
8.1 General.
5.5.1.1 Machine-cut threading processes
are acceptable.
5.5.2 Cold-Formed (Rolled) Threads
5.5.2.1 Subsequent to cold forming
threads, the threaded component shall
meet the heat-treat conditions and hardness requirements given in either Section
3 or 4 for the parent alloy from which the
threaded component was fabricated.
5.6 Cold-Deformation Processes
5.6.1 Cold-deformation processes such as
burnishing that do not impart cold work
exceeding that incidental to normal machining operations, such as turning or
boring, rolling, threading, drilling, etc., are
acceptable.
5.6.2 Cold deformation by controlled shot
peening is permitted when applied to base
materials that meet the requirements of
this document and when limited to the use
of a maximum shot size of 230 (0.584 mm
nominal diameter) and a maximum of
0.356 mm A Almen intensity. The process
shall be controlled in accordance with
Military Specification MIL-S-13165-B,
latest revision.
Section 6: Bolting
6.1. General.
Materials shall meet the requirements of
this section if they are to be exposed to
sour environments (defined in Paragraph
1.3).
6.2 Exposed Bolting
6.2.1 Bolting that will be exposed directly
to sour environment or that will be buried,
insulated, equipped with flange protectors,
or otherwise denied direct atmospheric
exposure must be of either a Class I or
Class II material (see Paragraph 6.2.1.1).9
6.2.1.1.2 Bolting materials that meet the
specifications of ASTM A 193 Grade B7M,
550 MPa (80,000 psi) minimum yield
strength, and 22 HRC maximum are acceptable.
6.2.1.1.3 Nuts shall meet the specifications of ASTM A 194 Grade 2HM (22 HRC
maximum) or Paragraph 6.2.1.1.1.
6.3 Nonexposed Bolting
6.3.1 Class III Bolting
6.3.1.1 Bolting that is not directly exposed
to sour environments and is not to be
buried, insulated, equipped with flange
protectors, or otherwise denied direct atmospheric exposure may be furnished to
applicable standards such as ASTM A 193
Grade B7.
Section 7: Platings and Coatings
7.1 General
7.1.1. Materials shall meet the requirements of this section if they are to be
exposed to sour environments (defined in
Paragraph 1.3).
7.1.2 Metallic coatings (electroplated or
electroless), conversion coatings, and
plastic coatings or linings are not acceptable for preventing SSC of base metals.
The use of such coatings for other purposes is outside the scope of this standard.
7.2 Nitriding
7.2.1 Nitriding with a maximum case
depth of 0.15 mm (0.006 inch) is an
acceptable surface treatment when conducted at a temperature below the lower
critical temperature of the alloy system
being treated. Its use as a means of preventing SSC is not acceptable.
Materials for special components including instrumentation, control devices,
seals, bearings, and springs shall meet
the requirements of this section if they are
directly exposed to sour environments
during normal operation of the device.
Paragraph 1.3 provides guidelines to determine the applicability of this standard to
specific applications.
8.2 Bearings
8.2.1 Bearings directly exposed to sour
environments shall be made from materials in Sections 3 and 4.
8.2.2 Nickel-chromium-molybdenum-tungsten alloy UNS N10276 bearing pins, i.e.
core roll pins, are acceptable in the coldworked condition to 45 HRC maximum.
8.2.3 Bearings made from other materials
must be isolated from the sour environment in order to function properly, except
as noted in Paragraph 8.2.2.
8.3 Springs
8.3.1 Springs directly exposed to the sour
environment shall be made from materials
described in Sections 3 and 4.
8.3.2 Cobalt-nickel-chromium-molybdenum alloy UNS R30003 may be used for
springs in the cold-worked and age-hardened condition to 60 HRC maximum. UNS
R30035 may be used for springs in the
cold-worked and age-hardened condition
of 55 HRC maximum when aged for a
minimum of 4 hours at a temperature no
lower than 648°C (1200°F).
8.3.3 Nickel-chromium alloy UNS N07750
springs are acceptable in the cold-worked
and age-hardened condition to 50 HRC
maximum.
8.3.4 UNS N07090 may be used for springs
for compressor valves in the cold-worked
and age-hardened condition to 50 HRC
maximum.
Notes
9. Designers and users should be aware that
it may be necessary to derate the pressure
rating in some cases when using lowstrength bolts. For API 6A flanges using
Class II bolting, see API Standard 6A.
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8.4 Instrumentation and Control
Devices
the as-cast or solution-annealed condition
to 160 HB (83 HRB) maximum.
stainless steel with a given ferrite content
for each application.
8.4.1 Instrumentation and control device
components directly exposed to sour environments shall be made from materials in
Sections 3 through 8.
8.6 Snap Rings
8.9 Special Process Parts 11
8.6.1 Snap rings directly exposed to a
sour environment shall be made from applicable materials in Sections 3 and 4,
except as noted in Paragraph 8.6.2.
8.9.1 Cobalt-chromium-tungsten alloys,
whether cast, powder-metallurgy
processed, or thermomechanically
processed, are acceptable.
8.6.2 Precipitation-hardening stainless
steel alloy UNS S15700 snap rings originally in the RH950 solution-annealed and
aged condition are acceptable when further heat treated to a hardness of 30 to 32
HRC as follows:
8.9.2 Tungsten carbide alloys, whether
cast or cemented, are acceptable.
8.6.2.1 Heat-Treatment Procedure (3-Step
Process)
9.1.1 Materials shall meet the requirements of this section if they are to be
exposed to sour environments (defined in
Paragraph 1.3).
8.4.1.1 Paragraph 3.5.1 is not intended to
preclude the use of AISI Type 316 stainless steel compression fittings and
instrument tubing even though they won’t
satisfy the requirements stated in
Paragraph 3.5.1. 1
8.4.2 Diaphragms, Pressure-Measuring
Devices, and Pressure Seals.4–6
8.4.2.1 Diaphragms, pressure-measuring
devices, and pressure seals directly exposed to a sour environment shall be
made from materials in Sections 3 and 4.
8.4.2.2 Cobalt-nickel-chromium-molybdenum alloys UNS R30003 and UNS
R30004 for diaphragms, pressure-measuring devices, and pressure seals are
acceptable to 60 HRC maximum.
8.4.2.3 Cobalt-nickel-chromium-molybdenum-tungsten alloy UNS R30260
diaphragms, pressure-measuring devices,
and pressure seals are acceptable to 52
HRC maximum.
8.4.2.4 Pressure seals shall comply with
the requirements of Sections 3 and 4 and
Tables 1 and 2 or may be manufactured of
wrought cobalt-chromium-nickel-molybdenum alloy UNS R30159 to 53 HRC
maximum with the primary load-bearing or
pressure-containing direction parallel to
the longitudinal or rolling direction of
wrought products.
8.5 Seal Rings
8.5.1 Seal rings directly exposed to a sour
environment shall be made from materials
in Sections 3 and 4.
8.5.2 Austenitic stainless steel API compression seal rings made of centrifugally
cast ASTM A 351 Grade CF8 or CF8M
chemical compositions are acceptable in
(1) Temper at 620°C (1150°F) for 4 hours,
15 minutes. Cool to room temperature in
still air.
9.1 General
9.1.2 Valves and chokes shall be manufactured from materials in accordance with
Sections 3 through 8.
(2) Retemper at 620°C (1150°F) for 4
hours, 15 minutes. Cool to room temperature in still air.
9.2 Shafts, Stems, and Pins
(3) Temper at 560°C (1050°F) for 4 hours,
15 minutes. Cool to room temperature in
still air.
9.2.1 Shafts, stems, and pins shall be
manufactured from materials in accordance with Sections 3 through 8.
8.7 Bearing Pins
8.7.1 Bearing pins, e.g., core roll pins,
made from UNS N10276 in the coldworked condition with a maximum
hardness of 45 HRC, may be used.
9.2.2 Austenitic stainless steel UNS
S20910 is acceptable for valve shafts,
stems, and pins at a maximum hardness
level of 35 HRC in the cold-worked condition, provided this cold working is
preceded by an anneal.
8.8 Duplex Stainless Steel for
Wellhead Components10
9.3 Internal Valve and Pressure
Regulator Components
8.8.1 Cast duplex (austenitic/ferritic) stainless steel UNS J93345 is acceptable in
the solution-treated condition provided
that the hardness does not exceeded 223
HB. The material must be restricted to the
following products: valve components,
compressor components, casting and tubing heads (excluding mandrel hangers),
spools, side entry caps, tail pieces, hammer caps, and spider caps. Laboratory
tests have shown that duplex stainless
steels’ susceptibility to SSC is a function
of the percentage of ferrite. The user may
determine the acceptability of a duplex
9.3.1 Cast CB7Cu-1 in the H1150 DBL
condition per ASTM A 747 is acceptable
for non-pressure-containing, internal
valve, and pressure regulator components
at 310 HB maximum (30 HRC maximum)
providing it complies with Paragraph 1.2.
Precipitation-hardening martensitic stainless steels that are in accordance with this
standard have provided satisfactory field
service in some sour environments. These
materials may, however, exhibit threshold
stress levels in NACE Standard TM0177
that are lower than other materials included in this standard.
Notes
10. Aging over 260°C (500°F) may reduce temperature toughness and reduce resistance
to environmental cracking.
Section 9: Valves and Chokes
11. Some of these materials may be used in
wear-resistant applications and can be
brittle. Environmental cracking may occur
if these materials are subject to tension.
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Materials listed in this table should be used only under conditions noted in the text of this standard.
Table 1
Stainless Steels Acceptable for Direct Exposure to Sour Environments (see Paragraph 1.3)
Ferritic
Martensitic
PrecipitationHardening
Austenitic
AISI
AISI
ASTM
Duplex
(Austenitic /Ferritic)3
(Wrought Condition Only)
AISI
UNS S31803
1
405
410
A 453 Gr. 660
302
UNS S32550
430
501
A 638 Gr. 6601
304
UNS S32404
304L
305
308
309
310
316
316L
317
321
347
ASTM
ASTM
UNS S17400
ASTM
Cast Duplex
A 268
A 217 Gr. CA 15
UNS S45000
A 182
(Austenitic/Ferritic)
TP 405, TP 430,
A 268 Gr. TP 410
UNS S66286
A 193 2
Stainless steel
TP XM 27, TP XM 33
A 743 Gr. CA 15M
Gr. B8R, B8RA, B8,
Z6CNDU20.08M, NF A
A 487 CI CA 15M
B8M, B8MA
320-55 French National
A 487 CI CA 6NM
UNS S42400
A 194 2
Standard
Gr. 8R, 8RA, 8A, 8MA
A 320 2
Gr. B8, B8M
A 351
Gr. CF3, CF8, CF3M,
CF8M
B463
B473
UNS S20910
UNS N08020
UNS S31254
Notes
1. See Paragraph 3.8.2.
2. Carbide solution-treated.
3. Aging over 260°C (500°F) may reduce
low-temperature toughness and reduce
resistance to environmental cracking.
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NACE MR0175-95 Excerpts on Valve Materials
Materials listed in this table should be used only under conditions noted in the text of this standard.
Mechanical properties described in the specifications noted below are not necessarily in accordance with MR0175.
Table 2
Nonferrous Materials Acceptable for Direct Exposure to Sour Environments (see Paragraph 1.3)
Nickel-Copper Alloys
UNS1
N05500
UNS
N04400
Nickel-IronChromium Alloys
UNS
N08800
Nickel-Iron-ChromiumMolybdenum Alloys
UNS
UNS
N06007
N08825
Nickel-Chromium Alloys
UNS
N06600
Coatings, Overlays, and
Special Process Parts
UNS
N07750
SAE/AMS ASTM
SAE/AMS
ASTM
SAE/AMS
ASTM
ASTM
ASTM
SAE/
ASTM
SAE/AMS Co-Cr-W Alloys as in AWS
4676
B 127
4544
B 163
5766
B 366
B 163
B 163
AMS
B 637
5542
A5.13-80
B 163
4574
B 366
5871
B 581
B 366
B 166
5540
5582
Ni-Cr-B Alloys as in AWS
B 164
4575
B 407
B 582
B 423
B 167
5580
5598
A5.13-80
B 366
4730
B 408
B 619
B 424
B 366
5665
5667
Tungsten Carbide Alloys
B 564
4731
B 409
B 622
B 425
B 516
7232
5668
Ni-B Alloys as in AMS 4779
7233
B 514
B 626
B 704
B 517
5669
Ceramics
B 705
B 564
5670
B 515
B 564
5671
5698
5699
A 494
UNS N09925
Gr. M-35-1
UNS N08024
Gr. M-35-2
UNS N08028
UNS N07048
UNS N08535
UNS N08042
UNS N06952
UNS N04405
Note
1. Unified Numbering System for Metals and
alloys: ASTM E527 or SAE J1086.
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Table 2 – continued…Nickel-Chromium-Molybdenum
UNS N006625
UNS 10002
UNS N10276
UNS N07718
UNS N06002
ASTM
SAE/
ASTM
SAE/
ASTM
ASTM
SAE/
ASTM
SAE/
UNS N06030
B 336
AMS
A 597 Gr. 4
AMS
B 366
B 637
AMS
A 567
AMS
UNS N06975
B 443
5581
5388
B 574
B 670
5383
Gr. 5
5390
UNS N07725
B 444
5599
A 494
5389
B 575
5589
B 366
5536
UNS N06985
B 446
5666
Gr. Cw-12MW
5530
B 619
5590
B 435
5587
UNS N06110
B 564
5837
5750
B 622
5596
B 572
5788
UNS N07031
B 626
5597
B 619
5754
UNS N07716
5662
B 622
5798
UNS N06022
5663
B 626
5799
UNS N06060
B 704
B 705
5664
7237
5832
Table 2 – continued…
Cobalt-Nickel-ChromiumMolybdenum Alloys
UNS R30035
UNS R30003
Cobalt-Nickel-ChromiumTungsten Alloys
UNS R30605
Cobalt-Nickel-ChromiumTungsten Alloys
UNS R30260
Other Alloys
Aluminum
Tantalum
Titanium
Base
UNS R05200
Alloys
Alloys
UNS R03004
UNS R30159
UNS R31233
UNS R50400
Copper
UNS R53400
Alloys
UNS R58640
UNS R56260
UNS L56403
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API - RP 521 Noise
Excerpts from API - RP 521 Guide for Pressure-Relieving and Depressuring Systems
5.4.4.3 Noise
The noise level at 100 feet (30 meters) from
the point of discharge to the atmosphere can
be approximated by equation (9):
L100 (30) = L (from Fig. 12) + 10 log10 (1/2MC 2 ) (9)
Figure 12 – Noise Intensity at 100 Feet (30 Meters) From the Stack Tip
70
60
Figure 12 illustrates the noise intensity measured as the sound pressure level at 100
feet (30 meters) from the stack tip versus the
pressure ratio across the safety valve.
Sound Pressure Level at
50
100 feet [30 meters]
from stack tip minus
10 log [1/2 MC2]
40
The following symbols are used in the
procedure for calculating the noise level:
30
M = mass flow through the valve, in slugs
per second (kilograms per second).
20
▲
1.5
▲
2
C = speed of sound in the gas at the valve,
in feet per second (meters per second).
(
T = 560 degrees Rankine
)
kT
( ––––––––––––––
)
Molecular weight
[
0.5
= ratio of the specific heats in the gas.
r
= gas temperature, in degrees
Rankine (Kelvin).
PR = ratio of the upstream to the downstream pressure across the safety
valve (absolute).
An example of calculating, in English
units, the noise level at 100 feet from the
point of discharge to the atmosphere is
presented below:
1. Calculate 1/2MC 2 in watts. Divide the
weight flow (pounds per second) by 32 to
obtain M. Multiply 1/2MC 2 (foot-pounds per
second) by 1.36 to obtain 1/2MC 2 in watts.
= 1159 feet per second
1. 1/2MC 2 = (1/2)(1)(1159)2(1.36) = (9.1)(105).
3. From Figure 12, at PR = 3, the ordinate
= 54.
4. L100 at 100 feet = 54 + 60 = 114 decibels
1. Calculate 1/2MC 2 in watts.
In metric units, this translates to:
2. Calculate 10 log10(1/2MC 2).
3. In Figure 12, enter PR as the abscissa
and read the ordinate.
4. Add Items 2 and 3 to obtain the average sound pressure level at 30 meters,
L30, in decibels. Assume the following:
M = 14.6 kilograms per second
T = 311 kelvins
PR = 48/16 = 3
[
0.5
]
= 353 meters per second
1.
1/2MC 2
= (1/2)(14.6)(353)2 = (9.1)(105).
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designs and specifications without notice.
( )
Lp = L30 - 20 log10 –––r––
30
(10)
(10A)
Where:
Lp = sound pressure level at
distance r, in decibels.
r = distance from the sound source
(stack tip), in feet (meters).
Molecular weight= 29
(1.4) (311)
C = 91.2 –––––––––––––
29
( )
L100(30) = sound pressure level at 100 feet
(30 meters), in decibels.
k = 1.4
k = 1.4
Molecular weight = 29
By applying equation (10), the noise level
can be adjusted for distances that differ
from the 100-foot (30-meter) reference
boundary:
Lp = L100 - 20 log10 –––r–––100
4. Add Items 2 and 3 to obtain the average sound pressure level at 100 feet,
L100, in decibels. Assume the following:
M = 1 slug per second
= 32 pounds per second
Note: These calculations are based on
spherical spreading of the sound. If distances much larger than the height of the
vent above ground are of concern, add 3
decibels to the calculated result to correct
for hemispherical diffusion.
An example of calculating, in metric units,
the noise level at 30 meters from the point
of discharge to the atmosphere is presented below:
2. Calculate 10 log10(1/2MC 2)
3. In Figure 12, enter PR as the abscissa
and read the ordinate.
▲ ▲ ▲ ▲
7 8 9 10
4. L30 at 30 meters = 54 + 60 = 114 decibels.
]
2. 10 log10 ( 1/2MC 2 ) = 60
k
▲
6
3. From Figure 12, at PR = 3, the ordinate
= 54.
(1.4) (560)
C = 223 –––––––––––––
29
0.5
Where:
▲
5
2. 10 log10(1/2MC 2 ) = 60
PR = 48/16 = 3
0.5
kT
––––––––––––––
Molecular weight
In meters per second,
C = 9.12
▲
4
Pressure Ratio (PR)
Note: In feet per second,
C = 223
▲
3
170
For distances greater than 1000 feet (305
meters), some credit may be taken for
molecular noise absorption. When safety
valves prove to be excessively noisy during operation, the sound can be deadened
by the application of insulation around the
valve body and the downstream pipe up to
approximately five pipe diameters from the
valve.
Anderson Greenwood Pressure Relief Valves
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API - RP 527 Seat Tightness
Excerpts from API - RP 527 (July 1991) Seat Tightness of Pressure Relief Valves
Figure 1 – Apparatus to Test Seat
Tightness With Air
Flanged or threaded outlet
adapter for pressure relief
valve
Tube with outside
diameter of 5/16 inch
[7.9mm] and wall
thickness of 0.035
inch [0.89mm]
1/2
inch [12.7mm]
Water
Note
1.0 Scope
This standard describes methods of determining seat tightness of metal and soft
seated pressure relief valves, including
those of conventional, bellows and pilot
operated designs.
The maximum acceptable leakage rates
are defined for pressure relief valves with
set pressures from 15 psig (103 kPag) to
6,000 psig (41,379 kPag). If greater seat
tightness is required, the purchaser shall
specify it in the purchase order.
The test medium for determining the seat
tightness – air, steam or water – shall be
the same as that used for determining the
set pressure of the valve.
1. See Figure 2 for an example of a device to
relieve body pressure in case the valve accidentally pops.
For dual-service valves, the test medium –
air, steam, or water – shall be the same as
the primary relieving medium.
Figure 2 - Devise to Relieve Body
Pressure Caused by Accidental
Popping of the Valve
To ensure safety, the procedures outlined
in this standard shall be performed by persons experienced in the use and functions
of pressure relief valves.
Soft Rubber Gasket
Attached To Face Of
Detector To Prevent
Leakage
Cup-weld to
detector
C Clamp
Air Pressure
Outlet tube cut end
smooth and
square
Water level
control hole
maintain 1/2 inch
[12.7mm] from
bottom of tube
to bottom of
hole
1/2
inch
Membrane seals during
test and bursts
if valve
accidentally
opens
Safety Valve
2.0 Testing with Air
2.1 Test Apparatus
A test arrangement for determining seat
tightness with air is shown in Figure 1.
Leakage shall be measured using a tube
with an outside diameter of 5/16 inch (7.9
millimeters) and a wall thickness of 0.035
inch (0.89 millimeter). The tube end shall
be cut square and smooth. The tube opening shall be 1/2 inch (12.7 millimeters)
below the surface of the water. The tube
shall be perpendicular to the surface of
the water.
Arrangement shall be made to safely relieve or contain body pressure in case the
valve accidentally pops (see Figure 2).
2.2 Procedure
2.2.1 Test Medium
The test medium shall be air (or nitrogen)
near ambient temperature.
2.2.2 Test Configuration
The valve shall be vertically mounted on
the test stand, and the test apparatus shall
be attached to the valve outlet, as shown
in Figure 1. All openings–including but not
limited to caps, drain holes, vents, and
outlets–shall be closed.
2.2.3 Test Pressure
For a valve whose set pressure is greater
than 50 pounds per square inch gauge
(345 kilopascals gauge), the leakage rate
in bubbles per minute shall be determined
with the test pressure at the valve inlet
held at 90 percent of the set pressure. For
a valve set at 50 pounds per square inch
gauge (345 kilopascals gauge) or less, the
test pressure shall be held at 5 pounds
per square inch (34.5 kilopascals) less
than the set pressure.
2.2.4 Leakage Test
Before the leakage test, the set pressure
shall be demonstrated, and all valve body
joints and fittings should be checked with
a suitable solution to ensure that all joints
are tight.
Before the bubble count, the test pressure
shall be applied for at least 1 minute for a
valve whose nominal pipe size is 2 inches
(50 millimeters) or smaller; 2 minutes for a
valve whose nominal pipe size is 21/2, 3,
or 4 inches (65, 80, or 100 millimeters);
and 5 minutes for a valve whose nominal
pipe size is 6 inches (150 millimeters) or
larger. The valve shall then be observed
for leakage for a least 1 minute.
2.3 Acceptance Criteria
For a valve with a metal seat, the leakage
rate in bubbles per minute shall not exceed the appropriate value in Table 1. For
a soft-seated valve, there shall be no leakage for 1 minute (0 bubbles per minute).
3.0 Testing with Steam
3.1 Procedure
3.1.1 Test Medium
The test medium shall be saturated steam.
3.1.2 Test Configuration
The valve shall be vertically mounted on
the steam test stand.
3.1.3 Test Pressure
For a valve whose set pressure is greater
than 50 pounds per square inch gauge
(345 kilopascals gauge), the seat tightness
shall be determined with the test pressure
at the valve inlet held at 90 percent of the
set pressure. For a valve set at 50 pounds
per square inch gauge (345 kilopascals
gauge) or less, the test pressure shall be
held at 5 pounds per square inch (34.5
kilopascals) less than the set pressure.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
171
Anderson Greenwood Pressure Relief Valves
Technical Manual
API - RP 527 Seat Tightness
Excerpts from API - RP 527 (July 1991) Seat Tightness of Pressure Relief Valves
Table 1
Maximum Seat Leakage Rate for Metal Seated Pressure Relief Valves in Bubbles Per Minute
Set Pressure
(psig)
at
(60°F) [15.6°C]
Effective Orifice Sizes
0.307 inch and Smaller
Bubbles
Per
Minute
Effective Orifice Sizes
Larger than 0.307 inch
Approximate
Leakage Rate
per 24 Hours
Standard
Cubic
Feet
Bubbles
Per
Minute
Standard
Cubic
Meters
Approximate
Leakage Rate
per 24 Hours
Standard
Cubic
Feet
Standard
Cubic
Meters
15-1000 [.103-6.896 MPA]
40
0.60
0.017
20
0.30
0.0085
1500 [10.5 MPA]
60
0.90
0.026
30
0.45
0.013
2000 [13.0 MPA]
80
1.20
0.034
40
0.60
0.017
2500 [17.2 MPA]
100
1.50
0.043
50
0.75
0.021
3000 [20.7 MPA]
100
1.50
0.043
60
0.90
0.026
4000 [27.6 MPA]
100
1.50
0.043
80
1.20
0.034
5000 [38.5 MPA]
100
1.50
0.043
100
1.50
0.043
6000 [41.4 MPA]
100
1.50
0.043
100
1.50
0.043
3.1.4 Leakage Test
Before starting the seat tightness test, the
set pressure shall be demonstrated, and
the test pressure shall be held for least
three minutes. Any condensate in the
body bowl shall be removed before the
seat tightness test. Air (or nitrogen) may
be used to dry condensate.
After any condensate has been removed,
the inlet pressure shall be increased to the
test pressure. Tightness shall then be
checked visually using a black background. The valve shall then be observed
for leakage for at least one minute.
3.2 Acceptance Criteria
For both metal- and soft-seated valves,
there shall be no audible or visible leakage for one minute.
4.0 Testing with Water
4.1 Procedure
4.1.1 Test Medium
The test medium shall be water near ambient temperature.
4.1.2 Test Configuration
The valve shall be vertically mounted on
the water test stand.
4.1.3 Test Pressure
For a valve whose set pressure is greater
than 50 pounds per square inch gauge (345
kilopascals gauge) the seat tightness shall
be determined with the test pressure at the
valve inlet held at 90% of the set pressure.
For a valve set at 50 pounds per square
inch gauge (345 kilopascals gauge) or less,
the test pressure shall be held at 5 pounds
per square inch (34.5 kilopascals) less than
the set pressure.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
172
4.1.4 Leakage Test
Before starting the seat tightness test, the
set pressure shall be demonstrated and
the outlet body bowl shall be filled with
water, which shall be allowed to stabilize
with no visible flow from the valve outlet.
The inlet pressure shall then be increased
to the test pressure. The valve shall then
be observed for 1 minute at the test pressure.
4.2 Acceptance Criteria
For a metal-seated valve whose inlet has
a nominal pipe size of 1 inch or larger, the
leakage rate shall not exceed 10 cubic
centimeters per hour per inch of nominal
inlet size. For a metal-seated valve whose
inlet has a nominal pipe size of less than 1
inch, the leakage rate shall not exceed 10
cubic centimeters per hour. For soft-seated valves, there shall be no leakage for 1
minute.
Anderson Greenwood Pressure Relief Valves
Technical Manual
API - RP 527 Seat Tightness
Excerpts from API - RP 527 (July 1991) Seat Tightness of Pressure Relief
5.0 Testing with Air—Alternate
Method
5.1 Type of Valve to be Tested
Valves with open bonnets–bonnets which
cannot be readily sealed, as specified in
2.2.2–may be tested in accordance with
this section instead of Section 2.
This alternative method shall not be used
to test valves in which air bubbles can
travel to the open bonnet through any
passageway inside the valve guide without being observed at the valve outlet.
5.2 Procedure
5.2.1 Test Medium
The test medium shall be air (or nitrogen)
near ambient temperature.
5.2.2 Test Configuration
The valve shall be vertically mounted on
the air test stand. The valve outlet shall
be partially sealed with water to about
1/2-inch [12.7 mm] above the nozzle’s
seating surface.
5.2.4 Leakage Test
Before starting the seat tightness test, the
set pressure shall be demonstrated, and
the outlet body bowl shall be filled with
water to the level of the partial seal. The
inlet pressure shall then be increased to
the test pressure and held at this pressure
for one minute before the bubble count.
The valve shall then be observed for leakage for at least one minute.
Caution: When looking for leakage, the
observer shall use a mirror or some other
indirect means of observations so that the
observer’s face is not in line with the outlet
of the valve, in case the valve accidentally
pops.
5.3 Acceptance Criteria
For a valve with a metal seat, the leakage
rate in bubbles per minute shall not exceed 50 percent of the appropriate value
in Table 1. For a soft-seated valve, there
shall be no leakage for 1 minute (0 bubbles per minute).
5.2.3 Test Procedure
For a valve whose set pressure is greater
than 50 pounds per square inch gauge
[345 kPag], the leakage rate in bubbles
per minute shall be determined with the
test pressure at the valve inlet held at
90% of the set pressure. For a valve set
at 50 pounds per square inch gauge [345
kilopascals gauge] or less, the test pressure shall be held at 5 pounds per square
inch gauge [34.5 kilopascals] less than the
set pressure.
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
173
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 16 – Chemical Resistance Guide for Metals
erations) cannot be realistically duplicated
in a controlled laboratory environment.
The following table should be used only
as a guide for selecting materials for various applications. This table does not imply
a guarantee of corrosion resistance due to
the fact the complicating factors, (ie; agitation, impurities, aeration and velocity of
corrosives encountered in commercial op-
Symbol Guide:
C = Fair Resistance
N = Not Recommended
Blank spaces indicate insufficient data
A = Excellent Resistance
B = Good Resistance
Chemical Resistance Guide For Metals
Corrosive Media
Conditions
Gray Iron
Ductile Iron
CS
304
SS
316
SS
416
SS
Material Used
17-4 PH Stellite Inconel® Brass Bronze Copper Monel® Hastelloy® C
Acetaldehyde
C
B
B
A
N
B
A
N
N
N
A
A
Acetate Solvents (Crude)
N
N
A
A
B
A
A
C
B
B
A
A
Acetate Solvents (Pure)
N
C
A
A
Acetic Acid (Crude)
N
N
B
Acetic Acid (Pure)
N
N
A
Acetic Acid (30%)
N
Acetic Acid (Vapors)
N
B
Acetic Anhydride
C
N
Acetone
A
Acetylene
A
Air
Alcohols
A
A
N
B
B
A
N
A
B
A
N
N
B
N
N
B
A
N
B
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
B
A
A
B
A
A
B
A
A
Amines
B
A
A
C
A
Ammonia (Anhydrous)
B
B
A
A
B
B
Ammonia Solution
A
B
A
A
Ammonium Oxalate
N
C
B
A
Ammonium Persulphate
A
A
B
A
A
N
N
N
A
B
N
N
N
A
A
N
N
N
A
A
B
N
N
N
A
A
A
N
N
A
B
A
A
N
N
A
A
A
C
N
N
A
B
A
A
A
A
A
A
A
B
B
B
A
A
A
A
N
A
A
B
B
A
N
N
N
B
B
B
C
C
A
B
B
N
N
A
A
B
A
A
N
N
N
Ammonium Phosphate (Mono) N
N
A
A
B
A
A
N
N
N
Ammonium Phosphate (Di)
B
B
A
A
B
A
C
C
Ammonium Phosphate (Tri)
A
A
B
A
B
B
C
C
C
B
N
B
C
B
B
C
B
B
Ammonium Sulphate
N
C
N
B
B
N
B
N
N
N
B
Ammonium Sulfite
C
N
C
B
C
C
N
N
N
N
C
A
Amyl Acetate
C
C
A
A
B
A
C
N
N
A
B
Amyl Alcohol
C
B
B
A
B
B
N
N
N
N
N
N
B
B
N
N
N
A
N
N
N
B
N
B
B
B
N
N
N
C
B
B
B
B
A
Aniline
C
C
B
A
B
B
Aniline Dyes
C
C
A
A
B
A
Aniline Hydrochloride
N
N
N
C
N
Animal Oil (Lard)
A
A
A
A
A
Arsenic Acid
N
N
B
A
B
B
Asphalt
A
B
A
A
A
A
B
B
A
Barium Carbonate
B
B
A
A
A
B
B
B
B
B
Barium Chloride
C
C
C
B
C
C
C
C
A
A
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
174
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 16 – Chemical Resistance Guide for Metals
Chemical Resistance Guide For Metals
Corrosive Media
Conditions
Gray Iron
Ductile Iron
CS
304
SS
316
SS
Barium Hydroxide
C
C
A
A
Barium Nitrate
Barium Sulphate
C
C
A
C
C
B
Barium Sulphide
C
C
B
A
Barium Cyanide
B
416
SS
Material Used
17-4 PH Stellite Inconel® Brass Bronze Copper Monel® Hastelloy® C
A
Battery Acid
C
C
C
A
A
C
C
C
A
B
A
A
B
N
N
N
C
B
A
B
N
N
N
B
N
N
N
A
A
A
A
A
Beer (Food)
N
N
A
A
N
A
A
A
B
B
B
A
Beet Sugar Liquor
B
B
A
A
A
A
A
A
C
C
C
A
Black Sulphate Liquor
A
A
A
A
B
A
N
N
N
A
Blast Furnace Gas
A
A
A
A
A
A
A
A
Borax (Sodium Borate)
B
B
A
A
Bordeaux Mixture
A
A
A
A
Boric Acid
N
N
B
B
Bromine (Dry)
N
N
N
N
Bromine (Wet)
N
N
N
N
Butane
B
B
A
A
Butanol
A
A
A
A
Buttermilk
C
N
A
A
A
A
A
C
C
C
A
A
A
A
B
C
B
A
C
C
C
N
N
B
B
B
B
N
N
B
A
A
B
A
A
C
A
A
A
A
A
N
N
N
C
B
N
N
N
A
B
A
A
A
A
A
A
N
N
N
A
B
A
A
A
A
A
N
N
B
B
N
B
Butyl Acetate
C
C
B
A
A
B
Calcium Bisulphite
N
N
C
B
N
C
Calcium Carbonate
N
N
A
A
A
B
B
B
B
B
Calcium Chlorate
C
C
C
C
B
C
N
N
N
B
A
Calcium Chloride
C
C
C
B
B
C
B
B
B
A
A
A
Calcium Hydroxide
C
C
A
A
A
A
A
C
C
C
A
A
Calcium Hypochlorite
N
N
N
N
N
N
C
C
C
C
C
A
A
B
Calcium Sulphate
B
B
B
A
A
B
B
B
B
Cane Sugar Liquors
A
A
A
A
A
A
B
A
A
Carbolic Acid
N
N
A
A
A
A
C
C
C
B
A
Carbon Dioxide (Dry)
B
B
A
A
A
A
A
A
A
A
A
A
Carbon Dioxide (Wet)
C
C
A
A
A
A
A
C
C
C
C
B
Carbon Disulphide
B
B
A
A
B
A
A
C
N
N
B
B
Carbon Monoxide
A
B
A
A
A
B
B
B
Carbon Tetrachloride
N
C
C
C
B
C
A
A
A
N
N
N
B
A
C
C
C
A
A
A
A
N
N
N
Carbonated Beverages
N
N
A
A
Carbonic Acid
N
N
A
A
B
B
Castor Oil
A
A
A
A
B
Caustic Soda
B
C
A
B
Casein
A
A
B
A
B
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
175
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 16 – Chemical Resistance Guide for Metals
Chemical Resistance Guide For Metals
Corrosive Media
Conditions
CS
304
SS
316
SS
B
A
B
A
N
N
N
Caustic Potash
B
C
Cellulose Acetate
C
B
B
B
A
A
A
B
Cellulose Nitrate
B
B
B
B
B
B
B
B
Caustic Solutions
B
416
SS
Material Used
17-4 PH Stellite Inconel® Brass Bronze Copper Monel® Hastelloy® C
Gray Iron
Ductile Iron
China Wood Oil
C
C
A
A
A
B
B
B
Chloracetic Acid
N
N
N
C
N
N
N
N
A
Chlorbenzol
B
B
C
C
C
A
A
A
A
Chloramine
Chlorex
A
A
N
Chloric Acid
N
N
N
C
N
A
A
A
N
N
N
N
Chlorinated Solvents
C
C
A
A
A
C
N
N
N
Chlorinated Water
N
N
N
C
N
C
N
N
N
C
Chlorine (Dry)
C
B
B
B
B
B
A
B
B
B
A
B
Chlorine (Wet)
N
N
N
C
N
N
N
N
N
N
C
A
N
N
B
N
B
N
N
N
B
A
Citric Acid
N
N
B
A
C
B
C
B
B
B
A
Coconut Oil
A
A
A
A
N
A
N
N
N
Chlorosulfonic Acid
Cod Liver Oil
A
Coffee
A
A
A
N
A
N
N
N
A
Coke Oven Gas
A
A
A
A
A
A
C
C
C
B
Corn Oil
B
B
A
A
A
N
N
N
A
Cottonseed Oil
B
B
A
A
A
A
N
N
N
A
Creisike
B
B
A
A
A
A
C
B
B
A
Cresylic Acid
N
C
A
A
B
A
N
N
N
Crude Oil
A
A
A
A
B
A
C
C
C
A
A
A
A
Diethylamine
A
A
A
A
A
A
A
A
Dowtherm A or E
N
N
A
A
A
A
B
B
B
Ethylene Dichloride
N
C
C
C
Ethylene Glycol
B
A
A
A
A
A
B
A
Ethylene Oxide
B
C
A
A
Fatty Acids
N
N
B
A
Ferric Chloride
N
N
N
N
Ferric Nitrate
N
N
B
A
Ferric Sulphate
N
N
B
A
Ferrous Chloride
N
N
N
N
Ferrous Sulphate
N
N
B
A
Fish Oils
B
B
A
A
Flourine Gas
N
A
C
B
C
B
N
N
B
A
B
B
B
B
A
B
A
B
A
A
A
A
C
C
C
A
A
A
N
N
N
A
A
N
N
N
N
C
N
N
N
N
C
N
C
B
N
C
C
C
B
N
B
N
N
C
B
B
C
C
C
A
C
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
A
B
A
C
C
176
C
C
A
A
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 16 – Chemical Resistance Guide for Metals
Chemical Resistance Guide For Metals
Corrosive Media
Conditions
316
SS
CS
304
SS
Foamite (Acid)
N
N
C
Foamite (Alkaline)
A
A
A
A
Formaldehyde
N
C
A
A
B
A
Formic Acid
N
N
C
A
N
C
Freon
N
C
C
C
A
C
Fruit Juices
N
N
A
A
C
A
A
A
Fuel Oil
B
A
A
A
Gallic Acid
N
N
A
A
Gasoline (Natural)
A
A
A
A
Gasoline (Refined)
A
A
A
A
Gelatin
N
N
A
Glucose
B
B
A
Glycerine or Glycerol
A
A
Hydraulic Oil (Petro.)
B
B
Hydraulic Oil (Synthetic)
A
A
Hydrazine
416
SS
Material Used
17-4 PH Stellite Inconel® Brass Bronze Copper Monel® Hastelloy® C
Gray Iron
Ductile Iron
C
N
N
N
A
N
N
N
N
A
A
A
A
A
B
B
N
N
N
B
A
B
A
B
B
B
A
B
N
N
N
A
B
B
B
B
A
B
A
B
B
B
A
B
A
A
N
N
N
A
A
A
A
A
A
A
A
A
A
N
A
N
N
N
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
B
A
A
B
A
A
A
A
A
A
B
A
A
A
A
N
N
N
N
N
C
A
N
N
N
N
N
N
N
A
A
N
N
N
B
B
N
N
N
N
N
B
B
N
N
N
A
B
A
A
A
A
A
A
A
A
A
Hydrobromic Acid
N
N
Hydrochloric Acid
N
N
Hydrocyanic Acid
N
C
A
A
Hydroflouric Acid
N
N
N
N
Hydrofluosilic Acid
N
N
N
C
B
N
Hydrogen (Gas)
A
A
A
A
B
A
Hydrogen Chloride (Dry)
B
N
C
A
C
A
C
C
C
Hydrogen Chloride (Wet)
N
N
N
N
N
N
N
N
C
A
Hydrogen Fluoride (Dry)
C
N
C
C
N
A
C
B
B
A
B
N
N
B
Hydrogen Peroxide
N
N
B
B
A
B
B
N
C
C
B
A
Hydrogen Sulphide (Dry)
B
C
B
A
B
B
A
C
N
N
A
B
Hydrogen Sulphide (Wet)
B
C
B
A
C
B
A
C
N
N
B
A
Kerosene
B
A
A
A
A
A
A
A
A
A
A
B
Ketchup
N
N
A
A
A
C
Ketones
A
A
A
A
A
A
Lacquers and Solvents
C
C
A
A
A
A
Lactic Acid
N
N
B
B
C
B
Lard
A
A
A
Lactose
A
A
B
A
A
A
A
C
C
C
C
B
A
A
A
B
N
Lead Acetate
N
N
B
B
N
N
C
Lime-Sulfur
A
A
A
A
B
A
A
N
C
C
Linseed Oil
A
A
A
A
A
A
C
C
C
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
A
B
B
B
177
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 16 – Chemical Resistance Guide for Metals
Chemical Resistance Guide For Metals
Corrosive Media
Conditions
Material Used
17-4 PH Stellite Inconel® Brass Bronze Copper Monel® Hastelloy® C
Gray Iron
Ductile Iron
CS
304
SS
316
SS
416
SS
Lubricating Oil (Petro.)
A
A
A
A
A
A
A
A
A
B
Lubricating Oil (Synth.)
A
A
A
A
A
A
A
A
A
B
Magnesium Chloride
N
C
C
B
C
C
B
A
A
A
A
Magnesium Hydroxide
N
B
A
A
A
A
B
A
A
A
A
Magnesium Nitrate
N
N
N
N
N
B
Magnesium Sulphate
N
C
A
A
B
A
A
A
B
Magnesium Sulphite
N
N
Maleic Acid
N
C
A
B
A
A
A
A
B
A
C
A
Mercaptans
A
A
A
A
Mercuric Chloride
N
N
N
N
Mercuric Cyanide
N
N
B
Methane
B
A
A
C
C
C
B
B
N
N
N
N
N
N
N
N
N
B
B
B
B
N
N
N
N
B
A
A
A
A
A
B
A
Methanol
B
B
B
B
Methyl Chloride
C
C
B
B
A
C
B
N
B
B
B
B
B
B
A
A
B
A
B
B
B
B
B
A
Naphtha
B
A
A
A
A
A
Naphthalene
B
A
A
A
A
A
N
N
Nickel Chloride
N
N
N
C
Nickel Nitrate
N
N
B
B
A
B
B
C
A
A
A
A
B
B
B
B
B
B
N
C
C
B
A
C
C
C
B
B
A
B
Nickel Sulphate
N
N
B
Nitrating Acid
N
N
C
Nitric Acid (Crude)
N
N
C
B
B
C
N
N
N
N
N
B
Nitric Acid (Pure)
N
N
N
A
B
A
N
N
N
N
N
C
Nitrobenzene
B
A
A
A
A
B
B
B
B
B
Oxalic Acid
N
N
B
A
C
B
C
B
B
A
B
Oxygen
A
A
A
A
A
A
A
A
A
A
Palmitic Acid
C
C
B
A
B
B
C
B
B
B
B
Paraffin Oils
B
B
A
A
A
B
B
B
A
B
Petroleum (Sour Crude)
B
B
A
A
Petroleum (Sweet Crude)
A
A
A
A
B
A
B
C
B
B
C
N
N
N
A
C
N
N
A
A
A
A
C
N
N
A
A
A
A
A
A
A
A
B
A
A
A
A
B
Petroleum Oils (Refined)
A
A
A
A
Phenol
N
N
B
B
Phosphoric Acid
N
N
B
A
B
N
N
N
B
B
Potassium Bromide
N
N
C
A
C
A
C
C
C
B
A
Potassium Carbonate
B
C
A
A
A
A
C
C
C
A
B
Potassium Chlorate
B
B
A
A
A
A
B
B
B
B
B
Potassium Chloride
C
N
B
B
C
B
A
N
N
N
A
B
Potassium Cyanide
N
B
B
B
B
B
B
C
B
B
B
B
C
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
B
N
178
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 16 – Chemical Resistance Guide for Metals
Chemical Resistance Guide For Metals
Corrosive Media
Conditions
CS
304
SS
316
SS
Potassium Dichromate
C
C
A
A
Potassium Hydroxide
C
C
C
C
Potassium Hypochlorite
N
N
C
B
Potassium Nitrate
B
A
B
B
B
Potassium Sulphate
N
N
B
A
B
Producer Gas
A
A
A
A
Propane
A
B
A
A
A
A
Rosin
B
B
B
B
A
B
Salicylic Acid
N
N
B
A
Sea (Salt) Water
N
N
A
A
C
A
B
Shellac
N
N
A
A
Silver Bromide
N
N
C
B
C
C
N
Silver Chloride
N
N
N
N
N
C
Silver Nitrate
N
N
A
A
A
A
Sludge, Acid
C
C
C
Sewage
C
A
416
SS
Material Used
17-4 PH Stellite Inconel® Brass Bronze Copper Monel® Hastelloy® C
Gray Iron
Ductile Iron
A
B
N
N
N
B
B
C
B
N
N
N
A
B
C
N
N
N
N
B
B
A
A
A
B
B
B
B
A
A
A
A
A
C
C
C
A
A
A
A
A
B
A
B
B
B
A
B
B
B
B
B
A
B
C
B
B
A
B
B
B
B
A
B
B
A
A
A
N
N
N
B
B
N
N
N
N
A
N
N
N
B
A
A
A
B
Soap Solutions (Liquid)
B
A
A
A
C
A
C
C
C
A
Sodium Acetate
N
N
A
A
C
A
A
B
B
B
B
B
Sodium Aluminate
A
A
A
A
A
A
B
B
B
B
B
Sodium Bicarbonate
B
A
B
B
A
B
A
A
A
A
A
Sodium Bisulphate
N
N
B
A
A
B
N
N
N
A
A
Sodium Bisulphite
N
N
B
A
N
N
N
B
B
Sodium Carbonate
A
A
B
B
B
B
A
A
B
A
B
C
Sodium Chlorate
B
A
B
B
Sodium Chloride
C
C
C
B
C
A
Sodium Cyanide
C
C
C
B
Sodium Fluoride
N
N
C
A
B
B
B
B
N
C
B
C
Sodium Hydroxide
C
C
C
C
A
C
Sodium Hypochlorite
N
N
C
B
N
C
C
A
B
A
Sodium Nitrate
C
B
B
A
Sodium Nitrite
B
A
B
B
N
B
C
C
C
B
B
C
B
B
A
A
N
N
N
A
A
C
C
C
A
B
N
C
C
B
B
N
C
C
C
A
C
B
B
B
B
B
B
B
B
B
Sodium Perborate
C
C
A
A
A
A
A
C
B
B
B
B
Sodium Peroxide
C
C
A
A
A
A
A
C
B
B
B
B
Sodium Phosphate (Mono)
N
N
A
A
B
A
C
C
C
A
B
Sodium Phosphate (Di)
N
N
A
A
B
A
A
A
A
B
B
B
Sodium Phosphate (Tri)
C
C
A
A
B
A
A
C
C
C
Sodium Silicate
B
B
A
A
B
A
A
C
B
B
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
B
B
179
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 16 – Chemical Resistance Guide for Metals
Chemical Resistance Guide For Metals
Corrosive Media
Conditions
Material Used
17-4 PH Stellite Inconel® Brass Bronze Copper Monel® Hastelloy® C
Gray Iron
Ductile Iron
CS
304
SS
316
SS
416
SS
Sodium Sulphate
B
B
B
A
B
B
B
B
A
A
A
B
Sodium Sulphide
B
B
C
A
B
C
A
N
N
N
A
B
Sodium Sulphite
N
C
A
A
A
C
B
B
B
B
B
Sodium Thiosulphate
N
N
A
B
A
B
B
B
B
B
B
Stannic Chloride
N
N
N
N
N
N
N
N
N
C
B
Stannous Chloride
N
N
N
A
N
B
N
N
N
B
B
Steam, 212°F
A
A
A
A
B
A
A
A
B
B
B
A
A
Steam, 600° F
C
C
A
A
B
A
B
A
N
N
N
A
A
Sulfur
C
C
A
A
A
A
A
C
C
C
C
A
Sulfur Chloride
N
N
N
C
N
N
B
N
N
N
B
B
Sulfur Dioxide (Dry)
B
B
A
A
A
A
B
C
A
A
B
Sulfur Dioxide (Wet)
N
N
B
A
N
B
N
N
B
B
C
B
B
B
B
B
B
N
N
N
B
A
Sulfur Trioxide
B
B
B
B
B
B
Sulfuric Acid, 2% and Less
N
N
C
B
N
C
N
Sulfuric Acid, 2-40%
N
N
N
N
N
N
N
B
N
N
N
B
B
Sulfuric Acid, 40%
N
N
N
N
N
N
N
B
N
N
N
B
B
N
Sulfuric Acid, 93-100%
B
B
B
B
B
B
Sulfurous Acid
N
N
B
B
N
B
B
N
N
N
N
B
C
N
N
N
N
A
A
A
Tannic Acid
C
B
A
A
C
A
B
B
B
B
Tar
A
B
A
A
B
A
A
B
A
A
Tartaric Acid
N
N
B
A
C
B
A
Tung Oil
C
C
A
A
N
A
Turpentine
B
B
A
A
B
A
Varnish
C
C
A
A
A
A
B
A
A
A
A
Vegetable Oil
C
B
B
C
C
C
A
A
C
B
B
C
A
B
B
B
A
B
B
B
B
B
B
Water (Acid Mine)
N
N
B
B
A
B
B
A
N
N
N
A
Water (Boiler Feed)
B
B
A
A
A
A
A
A
C
C
C
A
Water (Distilled)
N
N
A
A
A
A
A
A
N
N
N
A
B
Water (Fresh)
A
A
A
A
A
A
A
A
C
B
B
A
A
Water (Salt)
N
N
N
C
N
N
A
B
C
B
B
A
Wine and Whiskey
N
N
A
A
N
A
A
A
B
B
B
C
A
Xylene (Xylol)
B
B
A
A
A
A
A
A
A
A
A
A
Zinc Chloride
N
N
N
C
N
N
B
N
B
B
B
B
Zinc Sulphate
N
N
A
A
B
A
B
C
B
B
A
B
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
180
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Acetaldehyde
Acetamide
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
X
X
Kel-F®
Vespel Urethane
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Acetic Acid
X
Acetic Anhydride
X
Acetone
X
X
X
X
X
X
X
Acetophenone
X
X
X
X
X
X
X
Acetyl Acetone
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Acetyl Chloride
Acetylene
X
X
X
Acetylene Tetrabromide
X
X
X
X
X
Acrylonitrile
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Alkyl Alcohol
X
X
X
X
X
X
Alkyl Amine
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Adipic Acid
X
Air
X
X
Alkazene
X
X
X
Alum Solution
Aluminum Acetate
X
X
Aluminum Chloride
X
X
X
X
X
X
X
X
X
X
Aluminum Fluoride
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Aluminum Nitrate
X
X
X
X
X
X
X
X
Aluminum Phosphate
X
X
X
X
X
X
X
X
Aluminum Potassium 10%
X
X
X
X
X
X
X
Aluminum Sulfate
X
X
X
X
X
X
X
X
X
Alum-NH3-Cr-K
X
X
X
X
X
X
X
X
X
X
Aluminum Hydroxide
Amines - Mixed
X
X
X
X
X
X
X
X
X
Ammonia Anhydrous
X
X
X
X
X
X
X
X
X
Ammonia Aqueous Liquid
X
X
X
X
X
X
X
X
Ammonia Gas
X
X
X
Ammonium Bifluoride
Ammonium Carbonate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Ammonium Chloride
X
X
X
X
X
X
X
X
Ammonium Hydroxide
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
181
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Ammonium Nitrate
X
X
Ammonium Nitrite
X
X
Ammonium Persulphate
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Ammonium Phosphate Tribasic
X
X
X
X
X
X
Ammonium Sulfate
X
X
X
X
X
Ammonium Sulfite
X
X
X
Amyl Borate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Amyl Alcohol
Vespel Urethane
X
Ammonium Phosphate Dibasic
Amyl Acetate
Kel-F®
Amyl Chloride
X
X
X
X
X
X
X
Amyl Chloro Naphthalene
X
X
X
X
X
X
X
Amyl Naphthalene
X
Aniline
X
Aniline Dyes
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Aniline Hydrochloride
X
X
X
X
X
X
X
X
X
Animal Fats
X
X
X
X
Ansul Ether
Antimony Trichloride
Apple Juice
X
X
Aqua Regia
Argon
X
X
X
Arochlor(s)
X
Arsenic Trichloride
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Aromatic Fuels
Arsenic Acid
X
X
X
X
Arsenous Acid
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Askarel
X
X
Asphalt
X
Astm Oil
Automatic Transmission Fluid
Barium Carbonate
X
X
X
X
X
X
X
Barium Chloride
X
X
X
X
X
X
X
X
X
X
X
Barium Hydroxide
X
X
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
182
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Barium Nitrate
Barium Sulfate
X
X
X
X
Kel-F®
Vespel Urethane
X
X
X
X
X
X
X
X
X
X
X
X
X
Barium Sulfide
X
X
X
X
X
X
X
X
Beer
X
X
X
X
X
X
X
X
X
X
X
X
Beet Juice
X
X
X
X
X
Beet Pulp
X
X
X
X
X
X
X
Beet Sugar Liquors
X
Bentonite
X
Benzaldehyde
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Benzene
Benzochloride
X
X
X
X
X
X
X
Benzoic Acid
X
X
X
X
X
X
X
Benzophenone
X
X
Benzyl Alcohol
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Benzyl Benzoate
X
X
X
X
X
X
X
Benzyl Chloride
X
X
X
X
X
X
X
Beryllium Sulfate
X
X
X
X
Bichloride of Mercury
X
X
X
X
X
X
Bittern
X
X
X
X
X
X
Black Liquor
X
X
X
X
X
X
Blast Furnace Gas
Bleach Liquor
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Bleach Solutions
Blood
X
X
Boiler Feed Water
Borax
X
Bordeaux Mixture
Boric Acid
X
Brake Fluid (Non Petroleum)
Brine
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Brine, Calcium
X
X
X
X
X
X
Brine, Cal. and Sodium Chloride
X
X
X
X
X
X
Brine, Cal. and Mag. Chloride
X
X
X
X
X
X
Brine, Seawater
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
183
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Kel-F®
Vespel Urethane
Bromine
X
X
X
X
X
X
X
Bromine Anhydrous
X
X
X
X
X
X
X
Bromine Trifluoride
X
X
X
X
X
X
X
Bromine Water
X
X
X
X
X
X
X
Bromobenzene
X
X
X
X
X
X
X
Bromochloro Trifluoroethan
X
X
X
X
X
X
X
Bunker Oil
X
X
X
X
X
X
X
X
X
Butadiene Monomer
X
X
X
X
X
X
X
X
X
Butane
X
X
X
X
X
X
X
X
Butane, 2,2-Dimethyl
X
X
X
X
X
X
X
X
Butane, 2,3-Dimethyl
X
Butanol (Butyl Alcohol)
X
X
Butene, 2-Ethyl
X
X
Butter
X
X
Buttermilk
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Butyl Acetate
Butyl Acetyl Ricinoleate
Butyl Acid
X
X
X
Butyl Acrylate
Butyl Alcohol
X
Butyl Amine or N-Butyl Amine
Butyl Carbitol
X
X
X
X
X
Butyl Cellosolve
X
X
X
Butyl Chloride
Butyl Oleate
Butyl Stearate
X
Butylene
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Calcium Bisulfide
Calcium Bisulfite
X
X
X
Calcium Carbonate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
184
X
X
X
Butyric Acid
Calcium Chlorate
X
X
X
X
X
X
X
Butyraldehyde
Calcium Acetate
X
X
X
X
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Calcium Chloride
X
X
Calcium Cyanide
X
X
Calcium Hydroxide
X
X
Calcium Hypochloride
X
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
Kel-F®
Vespel Urethane
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Calcium Hypochlorite
X
X
X
X
X
X
X
X
X
Calcium Nitrate
X
X
X
X
X
X
X
X
X
X
X
Calcium Phosphate
X
X
X
X
X
X
X
X
Calcium Silicate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Calcium Sulfate
X
Calcium Sulfide
X
Calgon
X
X
X
X
Caliche Liquor
X
X
X
X
Camphor
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cane Juice
Cane Sugar Liquors
X
Carbamate
Carbitol
X
Carbolic Acid Phenol
X
X
X
X
X
X
X
X
Carbon Bisulfide
Carbon Dioxide Dry
X
X
X
Carbon Dioxide Wet
X
X
Carbon Disulfide
Carbon Monoxide
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Carbon Tetrachloride Dry
X
X
X
X
X
X
X
Carbon Tetrachloride Wet
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Carbonate of Soda
Carbonic Acid
X
Casein
X
Castor Oil
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Catsup
X
X
X
X
Caustic Manganese
X
X
X
X
X
X
Caustic Potash (Aqueous)
X
X
X
X
X
X
Caustic Soda (Aqueous)
X
X
X
X
X
X
Caustic Sulphide
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
185
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Caustic (Chloride of Sodium)
Kel-F®
Vespel Urethane
X
X
X
X
X
X
Cellosolve
X
X
X
X
X
X
X
Cellosolve Acetate
X
X
X
X
X
X
X
Cellulube
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Chloride of Lime
X
X
X
X
X
Chloride of Zinc (Aqueous)
X
X
X
X
X
Cetene (Hexadecane)
X
Chloric Acid
X
Chlorinated Salt Brine
X
X
X
X
X
X
Chlorine, Dry
X
X
X
X
X
X
X
Chlorine, Wet
X
X
X
X
X
X
X
Chlorine Dioxide
X
X
X
X
X
X
X
Chlorine Trifluoride
X
Chloro 1-Nitro Ethane
X
X
X
X
X
X
X
X
X
X
X
X
Chloroacetic Acid
X
X
X
X
X
X
Chloroacetone
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Chlorobenzene
Chorobromo Methane
X
Chlorobutadiene
X
X
X
X
X
X
X
Chlorododecane
X
X
X
X
X
X
X
Chloroform
X
X
X
X
X
X
X
X
X
X
X
X
Chlorosulfonic Acid
Chlorosulfuric Acid
Chlorotoluene
Chlorox
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Chrome Alum
Chrome Plating Solutions
X
Chromic Acid
X
X
X
Chromic Oxide (Aqueous)
Citric Acid
X
X
Cobalt Chloride
X
X
Coca Cola Syrup
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cocoa Butter
Coconut Oil
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
186
X
X
X
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
Cod Liver Oil
BUNA-N EPR
X
X
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
Coffee Extracts Hot
Coke Oven Gas
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Kel-F®
Vespel Urethane
X
X
X
X
Cooking Oil
X
Copper Acetate
X
X
X
X
X
X
X
X
Copper Chloride
X
X
X
X
X
X
X
X
X
X
X
Copper Cyanide
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Copper Nitrate
Copper Sulfate
X
Corn Oil
X
Cottonseed Oil
X
Creosote
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cresol
X
X
X
X
X
X
X
Cresylic Acid
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Crude Oil Sour
Crude Oil Sweet
X
Cumene
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cyclohexane
X
X
X
X
X
X
X
X
Cyclohexanol
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cupric Chloride
Cutting Oil
Cyclohexanone
X
Decalin
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Decane
X
Denatured Alcohol
X
Detergent, Watered Solution
X
Developing Solutions
X
Dexron
X
X
Dextrin
X
X
X
Diacetone
X
X
X
X
X
X
X
Diacetone Alcohol
X
X
X
X
X
X
X
Dibenzyl Ether
X
Dibenzyl Sebacate
X
Dibromoethyl Benzene
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
187
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Kel-F®
Vespel Urethane
Dibutyl Amine
X
X
X
X
X
Dibutyl Ether
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Dibutyl Phthalate
X
Dibutyl Sebacate
X
X
Dichloroethane
Dichloro-Butane
X
X
Dichloro-Difluromethane
X
X
X
Dichloro-Ethyl Ether
X
X
X
Dichloro-Isopropyl Ether
X
Dichloro-Pentane
Dicylohexylamine
Diesel Oil
X
X
X
Diester Synthetic Lubricants
X
Diethanol-Amine
X
Diethyl Amine (DEA)
X
X
Diethyl Benzene
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Diethyl Carbonate
X
X
X
X
X
X
Diethyl Ether
X
X
X
X
X
X
X
Diethyl Sebacate
X
X
X
X
X
X
X
X
X
X
X
Diethylene Glycol
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Diethylene Triamine
Diisobutylene
X
X
Diisopropyl Benzene
X
Diisopropyl Ketone
X
Dimethyl Aniline
Dimethyl Formomide (DMF)
X
X
Dimethyl Phthalate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Dimethyl Terephthalate
X
X
X
X
X
X
Dinitrotoluene
X
X
X
X
X
X
Dioctyl Amine
X
X
X
X
X
X
Dioctyl Phthalate
X
X
X
X
X
X
X
X
Dioctyl Sebacate
X
X
X
X
X
X
X
X
Dioxane
X
X
X
X
X
X
X
Dioxolane
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
188
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Dipentane
Dipentene
X
Diphenyl
Diphenyl Oxides
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
Vespel Urethane
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Kel-F®
X
X
Dish Water
X
X
X
X
X
X
X
Dowtherm A
X
X
X
X
X
X
X
Dowtherm E
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Dye Wood Liquor
X
X
X
X
X
X
Enamel
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Disodium Phosphate
X
Dry Cleaning Fluids
Drying Oil
X
Epichlorohydrin
Epsom Salt
X
Essential Oils
X
Ethan (Methylmethane)
Ethane (Ethylene)
X
Ethanol
X
X
Ethanol Amine
X
Ethone
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Ethyl Acetate-Organic Ester
X
X
X
X
X
X
X
X
Ethyl Acetoacetate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Ethyl Acrylate
Ethyl Alcohol
X
Ethyl Benzene
Ethyl Benzoate
Ethyl Bromide
X
Ethyl Cellosolve
X
Ethyl Chloride
X
Ethyl Chlorocarbonate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Ethyl Chroroformate
Ethyl Ether
X
X
X
Ethyl Cellulose
Ethyl Cyclopentane
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
189
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Ethyl Formate
Ethyl Hexanol
X
X
X
X
X
Ethyl Mercaptan
Ethyl Oxalate
X
Ethyl Sulfate
X
Ethylene Chlorohydrin
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Vespel Urethane
X
Ethylene Chloride
Ethylene Diamine
X
Kel-F®
X
Ethyl Pentachlorobenzene
Ethyl Silicate
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Ethylene Dibromide
X
X
X
X
X
X
X
Ethylene Dichloride
X
X
X
X
X
X
X
Ethylene Glycol
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Ethylene Oxide
Ethylene Trichloride
Fatty Acids
X
Ferric Chloride
X
X
Ferric Chloride Boiling
X
X
X
X
X
X
X
Ferric Nitrate
X
X
X
X
X
X
X
X
X
X
X
Ferric Sulfate
X
X
X
X
X
X
X
X
X
X
X
Ferrous Chloride
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Ferrous Sulfate
X
Fish Oil
X
X
Florine Gas
X
X
Flue Gases
X
Fluorinated Cyclic Ethers
X
X
X
X
X
X
X
X
X
X
Fluorine Gas Dry
X
X
Fluorine (Liquid)
X
X
X
X
Fluorobenzene
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Fluoroboric Acid
X
Fluorocarbon Oils
Fluorolube
X
Fluorosilic Acid
X
Formaldehyde
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
190
X
X
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
Vespel Urethane
Formic Acid
X
X
X
X
X
X
Freon 11
X
X
X
X
X
X
X
X
Freon 112
X
X
X
X
X
X
X
X
Freon 113
X
X
X
X
X
X
X
X
Freon 114
X
X
X
X
X
X
X
X
Freon 114B2
X
X
X
X
X
X
Freon 115
X
X
X
X
X
X
Freon 12
X
X
X
X
X
X
X
X
X
X
X
Kel-F®
Freon 121
X
X
X
X
Freon 13
X
X
X
X
X
X
X
X
X
Freon 13B1
X
X
X
X
X
X
X
X
X
Freon 14
X
X
X
X
X
X
X
X
X
Freon 142b
X
X
X
X
X
X
Freon 152a
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Freon 22
X
X
X
X
X
X
X
X
Freon 31
X
X
X
X
X
X
X
X
X
X
Freon 21
Freon 218
Freon 32
X
Freon 502
X
X
X
X
X
X
X
X
X
X
X
Freon BF
X
Freon C316
X
X
X
X
X
X
X
X
X
X
X
Freon C318
X
X
Freon MF
X
X
X
X
X
X
X
X
X
X
X
Freon TA
X
X
Freon TC
X
X
Freon TF
X
Freon TMC
X
X
Freon T-P35
X
X
X
Freon T-WD602
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Fruit Juices
X
X
X
X
X
X
X
X
Fuel Oil
X
X
X
X
X
X
X
Fuel Oil Acidic
X
X
X
X
X
X
X
X
Fuel Oil #6
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
191
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
Fumaric Acid
BUNA-N EPR
X
X
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
Furan
Kel-F®
Vespel Urethane
X
X
X
X
X
X
X
X
X
X
X
X
Furfural
X
X
X
X
X
X
X
Furfuraldehyde
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Furfuran
Furfuryl Alcohol
X
Furyl Carbinol
Gallic Acid
X
X
X
X
Gas, Natural
X
X
X
X
X
Gas, Sour
X
X
X
X
X
Gas Odorizers
X
X
Gas Oil
X
X
X
X
X
X
X
X
X
X
X
X
X
Gasoline Aviation
X
X
X
X
X
X
Gasoline Leaded
X
X
X
X
X
X
Gasoline Refined
X
X
X
X
Gasoline Sour
X
X
X
X
Gasoline Unleaded
Gelatin
X
X
Glauber’s Salt
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Glucose
X
X
X
X
X
X
X
X
X
X
X
Glue
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Glue Sizing
Glycerine-Glycerol
X
X
X
X
Glycol Amine
Glycols
X
X
X
X
Glyoxal
Grape Juice
Graphite
X
X
Grease
Green Sulfate Liquor
X
X
Halothane
X
X
X
Halowax Oil
X
Helium
X
Heptane
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
X
192
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Hexamine
Kel-F®
X
X
X
Hexanol Tertiary
X
X
X
X
X
Hexyl Alcohol
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Hops
Hydraulic Oil, Petroleum Base
X
X
X
Hydraulic Oil, Synthetic Base
Hydrazine
X
Hydrazine Anhydrous
X
X
Hydrobromic Acid
Hydrocarbons
X
X
X
Hydrochloric Acid over 158°F
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Hydrocyanic Acid
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Hydrofluoric Acid Hot
X
Hydrofluoric Acid-Anhydrous
X
X
X
Hydrochloric Acid to 158°F
Hydrofluoric Acid Cold
Vespel Urethane
X
X
X
X
X
X
X
X
X
X
X
X
X
Hydrofluosilicic Acid
X
X
X
X
X
X
X
X
Hydrogen Gas
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Hydrogen Peroxide
Hydrogen Sulfide Dry
Hydrogen Sulfide (Wet) Cold
X
Hydrogen Sulfide (Wet) Hot
Hydroquinone
Hydyne
X
Hypochlorous Acid
X
X
Illuminating Gas
X
Ink, Newspaper
X
Iodine
X
X
Iodine Pentafluoride
Iodoform
X
Isobutane
X
Isobutyl Alcohol
X
Isobutyl N-Butyrate
Isododecane
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
193
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
Isooctane
BUNA-N EPR
X
Isophorone (Ketone)
Isopropanol
X
X
X
Isopropyl Acetate
Isopropyl Alcohol
X
X
X
X
X
X
Isopropyl Chloride
Isopropyl Ether
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
X
X
JP-3 to JP-10
Kel-F®
Vespel Urethane
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Kerosene
X
X
X
X
X
X
Ketchup
X
X
X
X
X
X
Ketones
X
X
X
X
X
X
Lacquer solvents
X
X
X
X
X
X
X
Lacquers
Lactic Acid
X
Lactones
Lard
X
X
X
X
X
Lead Acetate
X
X
Lead Nitrate
X
X
Lead Sulfamate
X
X
Lime Bleach
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Linoleic Acid
X
X
X
Linseed Oil
X
X
X
Liquid Petroleum Gas (LPG)
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Lithium Bromide
X
X
X
X
X
X
Lithium Chloride
X
X
X
X
X
X
X
X
X
X
X
X
Lubricating Oils
X
X
X
X
X
Ludox
X
X
X
X
X
Lye Solutions
X
X
X
X
Magnesium Bisulfate
X
X
X
X
X
Magnesium Bisulfide
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
194
X
X
X
Lime Water
Lindol
X
X
X
Lime Liquor
Lime Sulfur
X
X
X
Latex
Lavender Oil
X
X
X
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Magnesium Carbonate
X
Magnesium Chloride
X
X
X
X
Magnesium Hydroxide
X
X
X
X
Majamie Resins
X
Malathion
X
X
Maleic Acid
Maleic Anhydride
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Malic Acid
X
Manganese Carbonate
X
X
X
X
X
Manganese Chloride
Manganese Sulfate
Mayonnaise
X
X
Mea with Copper Sulfate
Mea (Mono Ethanol Amine)
X
Meat Juices
X
Menthol
X
Mercuric Chloride
X
X
X
X
Vespel Urethane
X
X
Magnesium Nitrate
Magnesium Sulfate
Kel-F®
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Mercury Salts
X
X
X
X
X
X
Mercury Vapors
X
X
X
X
X
X
X
X
X
X
X
X
Mercuric Cyanide
Mercurous Nitrate
Mercury
X
X
Mesityl Oxide (Ketone)
X
X
X
X
Methane
X
X
Methanol
X
X
Methyl Acetate
X
Methyl Acetoacetate
X
X
X
Methyl Acetone
Methyl Acrylate
Methyl Alcohol
X
X
X
X
Methyl Amine
Methyl Benzoate
Methyl Bromide
Methyl Butyl Ketone
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
195
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Methyl Carbonate
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
Methyl Cellosolve
X
Methyl Cellulose
Kel-F®
Vespel Urethane
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Methyl Chloride
X
X
X
X
X
X
X
Methyl Chloroformate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Methyl Chlorosilanes
Methyl Cyclopentane
Methyl Ether
X
X
X
X
Methyl Ethyl Ketone (MEK)
X
X
X
X
X
X
X
Methyl Formate
X
X
X
X
X
X
X
Methyl Isobutyl Ketone
X
X
X
X
X
X
Methyl Isopropyl Ketone
X
X
X
X
X
X
X
Methyl Mercaptan
X
X
X
X
X
X
X
X
X
X
X
X
X
Methyl Methacrylate
Methyl Oleate
X
X
X
X
X
X
X
Methyl Salicylate
X
X
X
X
X
X
X
Methylacrylic Acid
X
X
X
X
X
X
X
X
X
X
X
X
Methylene Chloride
Milk
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Molasses
X
X
X
X
Molybdic Acid
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Milk of Lime
Mine Water
Mineral Oils
X
X
Mono Bromobenzene
Mono Chlorobenzene
Mono Ethyl Ether
X
X
Mono Methyl Aniline
X
Mono Methyl Hydrazine (Hypergol)
X
X
X
X
Mono Vinyl Acetylene
X
X
X
X
Mopholine
Muriatic Acid
X
X
Mustard
Mustard Gas
Naphtha
X
X
X
X
Naphtha Crude
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X = General acceptability
Blank = Not acceptable or no available data
196
X
X
X
X
Note
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Naphthalene
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Kel-F®
X
X
X
X
X
X
X
X
X
X
X
X
Vespel Urethane
X
Naphthenic Acid
X
Natural Gas
X
X
X
X
X
X
X
Neatsfoot Oil
X
X
X
X
X
X
X
X
X
X
Neon
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Neville Acid
X
Nickel Acetate
X
Nickel Ammonium Sulfate
X
X
X
X
X
X
X
X
X
X
X
X
Nickel Chloride
X
X
X
Nickel Cobalt Sulfate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Nickel Nitrate
X
Nickel Salts
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Nickel Sulfate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Nicotine Sulfate
Nicotinic Acid
Niter Cake
X
X
X
Nitric Acid-Concentrated
X
X
X
Nitric Acid-Dilute
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Nitric Acid-Red Fuming
Nitrobenzene
Nitrobenzine
Nitroethane
Nitrogen
X
X
X
X
X
Nitrogen Tetroxide
X
Nitropropane
X
Nitrous Acid
X
X
Nitrous Gases
X
N-Butyl Acetate
X
N-Butyl Benzoate
X
N-Butyl Butyrate
N-Heptane
X
X
Nitromethane
Nitrous Oxide
X
X
X
X
N-Hexaldehyde
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
N-Hexane
X
X
X
X
X
X
X
X
X
X
N-Hexane-1
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
197
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
N-Methyl-2-Pyprolldone
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
N-Octane
X
N-Pentane
X
N-Propyl Acetone
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Octadecane
X
X
X
X
X
X
Octadene
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Octyl Alcohol
X
X
X
X
Olefin, Crude
Oleic Acid
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Oleum
Oleum Spirits
X
Olive Oil
X
X
Orthochloro Ethylbenzene
Ortho-Dichlorobenzene
Oxalic Acid
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Oxygen Cold
X
X
X
Oxygen (-200°F to +400°F)
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
O-Chloronaphthalene
X
X
X
X
X
X
X
O-Chlorphenol
X
X
X
X
X
X
X
O-Dlchlorobenzene
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Paint Thinner, Duco
Palm Oil
X
Palmitic Acid
X
X
X
X
X
Paraffin Liquid
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Pectin Liquor
X
X
X
X
X
X
Pentachloro Phenol
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Paraformaldehyde
X
Para-dichlorobenzene
Peanut Oil
Pentane
X
X
X
Perchloric Acid
X
X
X
X
Perchloroethylene
X
X
X
X
X
X
X
X
Petrolatum
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Petroleum Oil above 250° F
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
198
X
X
X
X
X
X
X
X
Ozone
X
X
Vespel Urethane
X
X
Octochloro Toluene
Kel-F®
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
Petroleum Oil below 250° F
BUNA-N EPR
X
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
Kel-F®
Vespel Urethane
X
X
X
X
X
X
Phenol
X
X
X
X
X
X
X
Phenyl Benzene
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Phenyl Ethyl Ether
Phenyl Hydrazine
X
Phorone
X
X
Phosphate Esters
Phosphoric Acid to 158°F
X
X
X
X
X
X
X
X
X
X
X
Phosphoric Anhydride
Phosphorous Trichloride
Phosphorus Pentoxide
X
X
X
Phosphorus Trichloride
X
X
X
Photographic Solutions
X
X
X
X
Phthalic Acid
X
X
X
X
Phthalic Anhydride
X
X
X
X
Pickling Solution
X
X
X
X
X
X
X
X
X
Picric Acid
X
X
X
X
X
X
X
Pine Oil
X
X
X
X
X
X
X
Pineapple Juice
X
X
X
X
X
Pinene
X
X
X
X
X
X
X
X
Piperidine
Plating Solutions - Chrome
Plating Solutions - Other
X
Polysulfide Liquor
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Poly Glycols
X
X
X
Potash
X
X
X
X
X
X
Potash Alum
X
X
X
X
X
X
Potash Sulfide
Potassium Acetate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Potassium Bicarbonate
X
X
X
X
X
X
Potassium Bichromate
X
X
X
X
X
X
X
X
Potassium Bisulfite
X
X
Potassium Bromide
X
X
X
X
X
X
X
X
Potassium Carbonate
X
X
X
X
X
X
Potassium Chlorate
X
X
X
X
X
X
X
X
X
X
X
Potassium Chloride
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
199
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Kel-F®
Vespel Urethane
Potassium Cupro Cyanide
X
X
X
X
X
X
X
X
X
X
Potassium Cyanide
X
X
X
X
X
X
X
X
X
X
X
X
X
Potassium Dichromate
X
X
X
X
X
X
X
Potassium Diphosphate
X
X
X
X
X
X
X
X
Potassium Ferricyanide
X
X
X
X
X
X
X
Potassium Ferrocyanide
X
X
X
X
X
X
X
Potassium Hydroxide
X
X
Potassium Hypochlorite
X
Potassium Iodide
X
Potassium Nitrate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Potassium Oxalate
X
X
X
Potassium Permanganate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Potassium Phosphate
Potassium Salts
X
X
X
X
Potassium Sulphate
X
X
X
X
X
X
X
X
X
Potassium Sulphite
X
X
X
X
X
X
X
X
X
X
X
X
Potassium (Molten)
X
Prestone
X
X
Producer Gas
X
X
X
X
X
Propane
X
X
X
X
X
Propane Propionitrile
X
X
X
X
X
X
X
X
Propyl Acetate
X
Propyl Alcohol
X
Propyl Bromide
X
Propyl Nitrate
X
X
X
X
X
Propylene
Propylene Glycol
X
X
Propylene Oxide
X
X
Pyridine
Pyrogallic Acid
Pyroligneous Acid
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Pyrrole
P-Cymene
X
X
X
X
X
X
X
X
Pulp Stock
Pyranol
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
200
X
X
X
X
Pydrauls
X
X
X
X
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
P-Dichlorobenzene
P-Tertiary Butyl Catechol
X
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Radiation
X
X
Rapeseed Oil
X
X
Red Oil
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Rosin
Rubber Solvents
Sal Ammoniac
X
Salad Oil
X
Salicylic Acid
Vespel Urethane
X
Quench Oil
RP-1 Fuel
Kel-F®
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Seawater, Saltwater
X
X
X
X
X
X
X
X
X
Sewage
X
X
X
X
X
X
X
X
X
X
Shellac
X
X
X
X
X
Silicate Ethers
X
X
X
X
X
X
X
X
Silicic Acid
X
X
X
X
X
X
X
X
Silicone Greases
X
X
X
X
X
X
X
X
X
Silicone Oils
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Salt Cake
Silver Bromide
Silver Chloride
X
Silver Cyanide
X
Silver Nitrate
X
X
X
X
X
Skydrol 500
X
Skydrol 7000
X
X
X
Soap Liquors
X
X
X
X
X
X
Soap Solutions
X
X
X
X
X
X
X
X
X
X
Soda Ash
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sodium Bisulfate
X
X
X
X
X
X
X
X
X
X
Sodium Bisulfite
X
X
X
X
X
X
X
X
X
X
Sodium
Sodium Acetate
X
Sodium Aluminate
Sodium Bicarbonate
Sodium Bichromate
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
201
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Sodium Borate
X
Sodium Bromide
X
Sodium Carbonate (Caustic)
X
Sodium Chlorate
X
Sodium Chloride
X
Sodium Chromate
X
X
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sodium Citrate
X
X
X
Sodium Cyanamide
X
X
X
X
X
X
X
X
X
X
Vespel Urethane
X
Sodium Cyanide
X
Kel-F®
X
X
Sodium Fluoride
X
X
Sodium Hydrosulfite
Sodium Hydroxide
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sodium Hypochlorate
X
X
X
X
X
X
X
X
X
X
Sodium Hypochlorite
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sodium Hyposulfite
X
Sodium Lactate
Sodium Metaphosphate
X
Sodium Metasilicate
X
X
Sodium Nitrate
X
X
Sodium Perborate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sodium Peroxide
X
X
X
X
X
X
X
X
X
Sodium Phosphate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sodium Plumbite
Sodium Silicate
Sodium Sulfate
X
X
X
X
X
X
X
X
X
X
Sodium Sulfide
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sodium Sulfite
X
Sodium Sulfite
X
X
X
X
X
Sodium Tetraborate
Sodium Thiosulfate
X
X
X
X
X
X
X
X
X
X
Sodium Trisulfate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Soybean Oil
X
X
X
X
X
X
X
X
Stannic Chloride
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sorbitol
Stannous Chloride
X
Starch
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
202
X
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Kel-F®
Steam over 300°F
X
X
X
X
X
X
Steam under 300°F
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Stearic Acid
X
Stoddard Solvent
X
X
X
X
Styrene
X
X
X
X
X
X
X
X
X
X
X
X
X
Sulfate Liquors
X
X
X
X
X
X
Sulfate of Hydrogen
X
X
X
X
X
X
Sulfate of Lime
X
X
X
X
X
X
Sulfate of Sodium
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sucrose Solutions
Sulfite Liquors
X
Vespel Urethane
X
X
X
X
X
X
X
Sulfite Pulp
Sulfur
X
X
X
X
X
X
X
Sulfur Chloride
X
X
X
X
X
X
X
Sulfur Dioxide
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sulfur Trioxide
X
X
X
X
X
X
X
X
X
Sulfur Trioxide, Dry
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sulfur Hexafluoride
X
X
Sulfuric Acid (20% Oleum)
Sulfuric Acid (Concentrated)
X
Sulfuric Acid (Dilute)
Sulfurous Acid
X
X
X
X
X
X
X
X
X
X
X
X
Sulphonated Fatty Alcohol
X
X
X
X
X
X
Sulphonated Vegetable Oils
X
X
X
X
X
X
Syrup
X
X
X
X
Tall Oil
X
X
X
X
X
X
X
Tallow
X
X
X
X
X
X
Tannic Acid
X
X
X
X
X
X
X
X
X
Tar, Bituminous
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Tartaric Acid
X
X
X
X
X
X
X
X
X
Terpineol
X
Tar, Pine
Tertahydrofuran
Tertiary Butyl Alcohol
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Tertiary Butyl Mercaptan
X
X
X
X
X
X
X
Tetrabromoethane
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
203
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
BUNA-N EPR
Tetrabromomethane
Tetrabutyl Titanate
X
X
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
Kel-F®
Vespel Urethane
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Tetrachloroethane
X
X
X
X
X
X
X
Tetrachloroethylene
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Tetraethyl Lead
X
Tetralin
Tetraphenyl
X
X
X
X
X
X
X
X
X
X
X
X
X
Thionyl Chloride
X
X
X
X
X
X
Titanium Tetrachloride
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Therminol VP-1,44,55,60,66
Toluene
Toluene Diisocyanate
X
Tomato Pulp
Transformer Oil
X
Transmission Fluid Type A
X
Triacetin
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Triaryl Phosphate
X
X
X
X
X
X
X
X
Triaryl Phosphate
X
X
X
X
X
X
X
X
Tributoxyl Ethyl Phosphate
X
Tributyl Mercaptan
Tributyl Phosphate
Trichloroacetic Acid
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Trichloroethane
Trichloroethylene
Tricresyl Phosphate
X
Triethanol Amine
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Triethyl Aluminum
X
X
X
X
Triethyl Borane
X
X
X
X
Trifluoroethane
X
X
X
X
Trinitrotoluene (TNT)
X
X
X
X
X
Trioctyl Phosphate
X
X
X
X
X
X
X
Tripoly Phosphate
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Trisodium Phosphate
Tung Oil (Chine Wood Oil)
X
X
Turbine Oil
X
X
Turpentine
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
204
X
X
Anderson Greenwood Pressure Relief Valves
Technical Manual
Section 17 – Chemical Resistance Guide for Elastomers and Thermoplastics
Chemical Resistance Guide For Elastomers and Thermoplastics
Fluid
Unsym. Dimethyl Hydrazine
BUNA-N EPR
X
Viton® Silicone Kalrez® Chemraz® Teflon® PEEK
X
Urea and Phenolic Resins
Uric Acid
Varnish
X
Vegetable Oil
X
Versilube
X
X
Vinegar
X
X
Vinyl Chloride
X
Vinyl Chloride Monomer (VCM)
Water
Waxes
X
Whiskey and Wines
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
White Pine Oil
X
X
Zinc Bromide
X
Zinc Chloride
X
Zinc Hydrosulfite
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Yeast
X
X
X
X
X
X
X
X
X
Xylidenes
X
X
X
X
Wood Vinegar
Zinc Acetate
X
X
X
Zeolites
X
X
X
Wood Pulp
Xylol
X
X
White Water, Paper Mill
X
X
X
X
X
Xylene
X
X
X
X
X
X
X
X
X
X
White Oil
Xenon
X
X
X
X
X
X
X
X
White Liquor
Wood Oil
X
X
X
X
X
X
X
X
X
Wagner 21B Fluid
X
X
X
Vinylidine Chloride
Vespel Urethane
X
X
X
Kel-F®
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Zinc Nitrate
X
X
X
X
X
X
Zinc Phosphate
X
X
X
X
X
X
Zinc Salts
X
X
X
X
X
X
X
X
X
X
Zinc Sulfate
X
X
X
X
X
X
X
X
X
X
Note
X = General acceptability
Blank = Not acceptable or no available data
© 1997 Anderson Greenwood reserves the right to change product
designs and specifications without notice.
205
Pressure Relief Valve
Technical Manual
Revised May 1998
Catalog: PRVTM-US.97
Anderson Greenwood
Anderson Greenwood
P.O. Box 944
Stafford, Texas 77497, USA
Tel: (281) 274-4400
Fax: (281) 240-1800
International Tel: +1 281 274-4400
International Fax: +1 281 240-1800
Corrie Way, Bredbury Industrial Estate,
Stockport, Cheshire SK6 2ST, UK
Tel: 0161 494 5363
Fax: 0161 494 5672
Telex: 668379
International Tel: +44 161 494 5363
International Fax: +44 161 494 5672
© 1997 Anderson Greenwood
Printed in USA