Steam Trap Operation
& Maintenance
Joel Lemke, C.E.M.
Emerson Process Management
18 May 2016
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Emerson Confidential
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Local History: “Rosemount Eng. Co.”
Day One: Frank Werner,
Vern Heath, and Robert
Keppel establish
Rosemount Engineering
Co. with $8,000
1956
1961
Rosemount
instruments in
space with NASA
Mercury capsule
and Alan Shepard
Rosemount
1151 Pressure
Transmitter
debuts
1969
Space shuttle
Columbia maiden
voyage with 300
Rosemount
sensors on board
Rosemount
instruments on
the moon
1976
1981
The World Leader in Pressure,
Temperature, Flow and Level
Instrumentation
Emerson Electric
Company acquires
Rosemount
Rosemount 1151
inducted into
Smithsonian Institute
Emerson Confidential
Slide 3
1992
Topics

Steam Basics & Terminology

Steam Trap Function & Types

Effects of Steam Trap Failure

Trap Testing & Intervals
Emerson Confidential
Slide 4
Steam Loses Energy as it is Distributed

Maximum heat transfer efficiency is when the
steam is in the vapor state

Steam loses heat to the surroundings as it flows
(even though the pipe is insulated)

Saturated steam reverts back to water as it loses
energy – condensate
STEAM
Emerson Confidential
Slide 5
Steam Traps
steam pipe
air
CO2

As steam travels through piping, heat is
lost to ambient

Some steam condenses to water &
collects in low points

If not removed, this leads to:
–
–
–
steam

Steam traps remove this condensate
while minimizing steam loss

Secondary purpose: vent air, CO2 &
other “non-condensibles”
condensate
steam trap line
Emerson Confidential
Slide 6
Inefficient heat transfer
Corrosion
Safety & equipment damage concerns
from water hammer
Steam
Trap
To condensate return
General Steam Trap Operation
Outlet Orifice
Steam and
Condensate In
Emerson Confidential
Slide 7
Condensate Out
Condensate
Detection
Common to all steam traps





Self-acting valve that cycles open & closed
Drains condensate while preventing steam loss
Help vent air, CO2 and other gases
Passive; no external power (uses steam pressure)
Drains condensate through internal orifice
– Orifice size selected for a particular “condensate load” (expected
amount of water since last trap location)

High failure rate: expected service life ~4-8 years if
properly installed – can fail ‘open’ or ‘closed’
Emerson Confidential
Slide 8
Steam Trap Sizing

Like an orifice – relate flow to differential pressure
– Flow rate = condensate load
• Apply safety factor of 2-3 to estimated load and size for that
load
– ∆P = steam pressure – condensate return pressure
Emerson Confidential
Slide 9
𝑄𝑄𝑚𝑚~ ∆𝑃𝑃
Topics

Steam Basics & Terminology

Steam Trap Function & Types

Effects of Steam Trap Failure

Trap Testing & Intervals
Emerson Confidential
Slide 10
Steam Trap Applications
1.
2.
3.
Process – at steam heating processes (heat
exchangers, unit heaters, coils, vessels, etc.)
Drip – every ~200 feet on steam distribution lines and
before valves, pipe ends & changes in direction
Tracer – small steam lines wrapped around process
lines to maintain temperature, usu. so it can be pumped
Emerson Confidential
Slide 11
Steam Trap Operating Principles
Velocity
difference
between
condensate &
steam
Buoyancy
difference
between
condensate &
steam
Temperature difference
between condensate &
steam
Emerson Confidential
Slide 14
Mechanical
Thermostatic
Thermodynamic
Steam Trap Operating Principles
Velocity:
1. Thermodynamic
Disc
Buoyancy:
1. Inverted
Bucket
2. Float &
Thermostatic
Temperature:
1. Bi-metallic
2.
Bellows
Emerson Confidential
Slide 15
Mechanical
Thermostatic
Thermodynamic
Mechanical
Float & Thermostatic

Operation
–
–
2 separate mechanisms for condensate and air
removal
Float rises with increasing condensate level,
opening discharge valve
•
–

Thermostatic element on top vents air & noncondensables
Inlet - above
Applications
–
–

Continuous discharge (usually does not cycle)
Heavy and/or variable condensate load
Process applications
Strengths & Weaknesses
–
–
–
Great for variable condensate loads
Excellent air venting
Water hammer can crush float, causing failedclosed condition
Emerson Confidential
Slide 16
Rectangular,
bolted cover
in a vertical
plane
Round,
eggshaped
Outlet - below
Mechanical
Inverted Bucket Steam Traps

Operation
–
–
–

Applications
–
–

Condensate enters, flows under the
bucket, and fills the trap body,
completely submerging the bucket
Condensate discharges through open
valve
Steam enters bucket, making it buoyant
and closing the valve
Heavy but steady condensate load
Drip or Process with not much air
Round,
bolted
cover
Strengths & Weaknesses
–
Inlet
Resistant to dirt, which settles at the
bottom
– “Loss of prime” – fails open
– Mediocre removal of non-condensables
Emerson Confidential
Slide 17
Tall,
cylindrical
shape
Thermostatic
Bimetallic Steam Traps

Operation
–
–
–

Applications
–
–

Element composed of bonded dissimilar metals
Steam increases element temperature, causing trap
to close
Sub-cooled condensate causes element to contract,
opening the valve
High-pressure applications to 6020 psi
High air venting requirements
Square bolted cover
Strengths & Weaknesses
–
Fully-open on start-up – good venting of condensate
& non-condensables
– Can install horizontally or vertically
– Corrosion can interfere with opening & closing
– Hysteresis – fails open
Very slow cycling (condensate back-up)
Emerson–Confidential
Slide 18
Outlet
Inlet
May have
integral strainer
Thermostatic
Bellows

Operation
–
–
–

Applications
–
–

Element composed of liquid-filled bellows; liquid boils
near steam temperature
Steam causes liquid to boil, bellows to expand, and
trap to close
Sub-cooled condensate causes element to contract,
opening the valve
Light condensate loads
High air venting requirements
Strengths & Weaknesses
–
Fully-open on start-up – good venting of condensate &
non-condensibles
– Can install horizontally or vertically
– Small and lightweight
– Susceptible to water hammer
Emerson Confidential
Slide 19 –
Slow-cycling (condensate back-up)
Thermodynamic
Thermodynamic Disc Steam Traps

Operation
–
–
–
–

Applications
–

Condensate enters & pushes the disc up,
allowing venting through the trap
Steam enters at high velocity (lower pressure),
causing static pressure above the disk to force it
onto its seat, closing the trap
Static pressure over a larger area overcomes
the inlet pressure
As steam condenses, pressure above the disk
drops & the trap cycles.
High temperature/pressure
Large hex-nut cover
Strengths & Weaknesses
Smallest overall
– Small & lightweight
size, fits in palm
– Tight shut-off when new
of your hand
– Short operating life
Emerson Confidential
Rapid cycling on light loads – “machine gunning”
Slide 20 –
Inlet
Outlet
May have
integral strainer
Topics

Steam Basics & Terminology

Steam Trap Function & Types

Effects of Steam Trap Failure

Trap Testing & Intervals
Emerson Confidential
Slide 22
Steam Trap Function
steam pipe

Traps help remove air
– air in steam lowers its temperature
•
air
CO2
– Quality, scrap, rework issues

steam
80# steam w/ 5% air ~ 4 degrees F cooler
Traps remove “non-condensibles”
(like CO2)
– CO2 reacts with water to form
carbonic acid
– accelerated corrosion
– Reduced heat transfer
condensate
Emerson Confidential
Slide 23
– Scale, dirt, plugging, leaks, early
component failure
Steam traps ensure a
reliable steam system
Results of Steam Trap Failing Closed

Stream traps remove condensate
from piping preventing:
Steam Blast Jolts Midtown, Killing One
– Erosion and corrosion of piping
reducing the lifespan of plant
equipment
– Inefficient heat transfer across heat
exchangers, distillers, reactors and
crackers

If this steam is not removed not only
is there inefficient heat transfer, but:
– Safety hazard: Water in steam
causing erosion/corrosion of plant
equipment
– Safety hazard: Water flashing to
steam and causing pressure surges
Emerson Confidential
Slide 24
“State investigators have focused on a steam trap about
10 feet from the blast site, which should have removed
cooled water droplets from the pipe.” New York Post
The mayor said the explosion appeared to have been
caused by cold water that reached the pipe. “Cold water
apparently causes these to explode,” he said. The New
York Times
Click to read more: New York Post
The New York Times
Other Condensate Issues in the
Distribution System




Erosion & Corrosion
– CO2 and water create carbonic acid
– Scale, plugging, premature component
failure
Efficiencies
– Liquid forms insulating barrier between
steam and pipe wall
• 1/100” water = Iron ½” thick
Poor temperature control
– 80# steam w/ 5% air ~ 4 degrees F cooler
Freezing damage to steam coils, heat
exchangers & other equipment
Emerson Confidential
Slide 25
Water Hammer
Erosion from water droplet
impingement on blades
Insulation
20% of traps cause 80% of trap issues
Steam Loss upon Failure

$60,000

$50,000
$40,000

$30,000
275
225
$20,000
175
$10,000
125
$0
1/32
1/16
75
3/32
1/8
5/32
3/16
Internal Orifice Size
7/32
1/4
25
9/32
The higher the steam pressure
and bigger the steam trap line;
the more energy is lost
The average inspection period for
steam traps is annual
“Average-quality traps may have
just a 4-year life expectancy
(which implies a 25% failure
rate), while higher-quality steam
traps may have an 8-yr life
expectancy (12.5% average
failure rate).”
–
Emerson Confidential
Slide 26
Risko, J., Understanding Steam Traps, Chemical
Engineering Progress, Feb 2011
Steam loss rises exponentially with
operating pressure and line size
Trap failures are “cumulative”

Blow-through failures raise condensate return pressure
– reduces capacity of all traps that are part of system
– more water hammer in condensate return

Traps fail closed – other traps need to drain more
condensate
Emerson Confidential
Slide 27
Topics

Steam Basics & Terminology

Steam Trap Function & Types

Effects of Steam Trap Failure

Trap Testing & Intervals
Emerson Confidential
Slide 28
Steam Trap Testing Methods
1.
2.
Visual: Confirm proper installation & identify external leaks
Thermal: IR gun for inlet & outlet temperatures
–
–
3.
Confirms flow through trap and in proper direction
Thermal-only: about half as effective as thermal + ultrasonic
Ultrasonic: Listen for proper cycling and detect blowthrough and plugged failures
–
Sound frequencies > 20 kHz
Emerson Confidential
Slide 29
Ultrasonic Testing of Steam Traps
Emerson Confidential
Slide 30
Value Can Be Assigned To Each Trap
Pressure
Orifice Diameter
0.100 inch
0.200 inch
0.300 inch



30 psig
75 psig
150 psig
250 psig
450 psig
$949
$3,797
$8,543
$1,905
$7,619
$17,142
$3,497
$13,989
$31,476
$5,621
$22,483
$50,586
$9,868
$39,470
$88,808
Larger, higher-pressure steam lines
Protect important plant equipment
Have a large impact on process control
Emerson
[File
NameConfidential
or Event]
Slide
32 Confidential
Emerson
Significant steam
loss may occur from
large or highpressure traps.
Adjust inspection
interval accordingly.
Automated Steam Trap Monitoring
Wireless Acoustic & Temperature Transmitter



Provides visibility to issues with critical steam traps
Detects failures in minutes so issues don’t wait until next survey
Complement to good steam trap inspections
Emerson Confidential
Slide 33
Automated Steam Trap Monitor Installation
Easily installed
Non-intrusive
 Mounted using stainless steel bands
 Can be placed in tight spots, harsh
environments and hazardous areas

Non-intrusive
Clamp on to pipe; no cutting
 No process downtime

Emerson Confidential
Slide 34
Mounts with supplied stainless steel bands
Interpretation of Acoustic &
Temperature Measurements




Steam trap state calculated using algorithms
within a software program
Based on acoustic noise level, temperature,
pressure and trap type
Trap states include: Good, Blowthru & Cold
Works with all trap vendors & types
250
200
150
100
50
0
250
200
150
100
50
0
Good Trap
Blowthru Trap
Cold Trap
250
200
150
100
50
0
Emerson Confidential
Slide 35
Know the
state of each
steam trap
Easily sort
to find failed
traps
Emerson Confidential
Slide 36
Differentiate between trap
and device failure
We can help identify critical traps with
fastest payback
Emerson Confidential
Slide 37
Service Contract Scope
Steam Trap Health Monitoring monthly service contract includes all
hardware necessary to monitor traps. Emerson installs and maintains
WirelessHART network and monitors steam trap health.
Gateway
Antenna
Cellular
Antenna
Enclosure Contents:
WirelessHART
Gateway
Cellular Modem
Power Supply
Steam Traps and WirelessHART Monitoring Devices
Emerson Confidential
Slide 39
Monitoring Service Architecture
Data is fed into a secure
cloud environment for
failure and performance
analysis
Hardware is installed
and commissioned on
site by Emerson
certified technicians
Emerson Confidential
Slide 40
Deliverable: Trap Failure & Energy Reporting
Emerson Confidential • 41
Emerson Confidential • Slide 41
Steam Trap Inspection Best Practices

Classify traps according to process criticality

Classify traps according to loss potential

Set inspection interval based on leak rate
– Inspect when steam loss = $2500?
• Determine correct dollar threshold based on your priorities

New monitoring technology facilitates real-time
detection of issues with critical traps
– Automates inspection in challenging locations
Emerson Confidential
Slide 42
US Pulp and Paper Company Reduces Energy
Loss with Wireless Acoustic Monitoring



Challenge: Unnecessary steam venting
identified as culprit of energy loss
Solution: Rosemount 708 Wireless
Acoustic Transmitters
Results:
– Data from acoustic sensors showed
frequency of unwanted steam venting
– Power plant operators made adjustments to
reduce temperature and avoid wasted
steam energy
Emerson Confidential
Slide 44
Steam Trap Operation
& Maintenance
Joel Lemke, C.E.M.
Emerson Process Management
18 May 2016