Paper No.
02101
2002
CORROSION
Brittle Fracture of an Underground Gas Gathering Pipeline at ERW
Weld Groove Defects under Hydrogen Charging Conditions and Wet
COz/HzS Corrosion
David E. Hendrix
The Hendrix Group Inc.
Steve O'Toole
Dynegy Midstream Services
Richard A. Mueller
Dynegy Midstream Services
Dr. Ronald E. Frishmuth
Consulting Engineer
Abstract
This paper discusses the laboratory failure analysis investigation of a 10" underground gas gathering
pipeline that ruptured while attempting to remove a hydrate blockage. Failure occurred as a
macroscopically brittle fracture along longitudinal groove defects associated with an ERW weld.
Laboratory investigation of the failure included ERW defect length and depth measurements, charpy
impact toughness testing, wall thickness profiles along the fracture, metallographic examinations at ERW
groove defects, microhardness measurements and mechanical property testing. Remaining strength and
critical flaw size analyses were conducted using several fracture mechanics programs and the results
compared with one another. Fracture mechanics analysis results supported the role of absorbed hydrogen
due to corrosion in causing failure at internal pressures below that predicted based on overload.
Keywords:
API 5L pipe, corrosion, brittle fracture, hydrogen charging, API 579, ASME B31G,
ASME B31.8, wet CO2 corrosion.
Copyright
2002 by NACE International. Requests for permission to publish this manuscript in any form, in part or in whole must be in writing to NACE International,
Publications Division, 1440 South Creek Drive, Houston, Texas 77084-4906. The material presented and the views expressed in this paper are solely those of the
author(s) and not necessarily endorsed by the Association. Printed in U.S.A.
1
BACKGROUND INFORMATION
An underground pipe associated with a gas-gathering pipeline failed resulting in an approximately eightfoot long rupture. The pipe was transporting wet natural gas containing CO2 and H2S. Just before failure
attempts were being made to remove a hydrate blockage. Details associated with the failed pipeline are
shown below:
Pipe
Specification
A P I 5 L 2 X-42 or Gr. B
Pipe O. D.
10.75" (273 mm)
Pressure
385 psig (2.65 MPa)
Temperature.
.~ 42°F (5°C)
H2S
6000 ppm
CO2
1.1 wt. %
Water cut
~67 %
Inhibition
none
LABORATORY FAILURE ANALYSIS PROCEDURES
Laboratory investigative procedures included: (1) visual observations, (2) scale/deposit analysis using
energy dispersive spectrometry (EDS), (3) scanning electron microscopy (SEM), (4) metallographic
analysis, (5) fracture mechanics analysis, (6) hardness testing, (7) chemical analysis, (8) tensile testing,
(9) charpy impact testing, (10) thickness measurements and, (11) bend testing.
OBSERVATIONS
Visual observations. Figure 1 shows the as-received pipe sample. It contained an approximately eightfoot long, wide-mouth rupture along its length at what was reported to be the two o'clock position. Crack
propagation was longitudinal and straight with no sine wave pattern or multiple fracture origins. The
fracture was macroscopically brittle except at the arrested ends where it deviated in an acute spiral as a
shear fracture (Figure 2). The pipe internal surface (I. D.) exhibited internal blisters and "pockmarked"
general corrosion (Figure 3). Internal deposits/scale emitted a strong sulfur odor. No mesa corrosion was
observed. Detailed examination of the I. D. at the fracture suggested that it followed what appeared to be
an ERW weld seam (Figure 4). The O. D. did not exhibit any remarkable features, including denting,
buckling, mechanical damage or localized or general corrosion.
Y
2
Figures 6 and 7 show representative close-ups of the pipe sample fracture, illustrating the flat,
macroscopically brittle fracture features and groove-like flaws. Figure 7 shows a typical "thumbnail"
fracture initiation site.
SEM observations. Figure 8 shows a scanning electron microscopic (SEM) view of the pipe sample
fracture in a visually brittle looking area. The SEM analysis results showed that the pipe fracture in a
macroscopically brittle area contained both ductile areas as microvoid coalescence dimples and brittle
features as quasi-cleavage facets. Secondary cleavage cracks have emanated off the main fracture.
Bend Test Results. Based on SEM examination results, which confirmed brittle fracture at the ERW
weld, we conducted bend tests to verify the room temperature ERW weld ductility of the pipe sample.
Bend tests were conducted to place the weld in tension at both the O. D. and I.D. Both samples passed
API 5L maximum deflection requirements, confirming the inherent ductility of the weld.
Metallographic observations. Figures 9 and 10 illustrate the pipe sample microstructure associated with
the weld and fracture. Figure 9 shows the pipe sample microstructure at an ERW groove-like flaw ahead
of the fracture. Several features in Figure 9 are of interest. The tip of the flaw is sharp, suggesting that an
appropriate fitness-for-service approach would be to treat the groove-like flaw as a crack, instead of a
rounded groove, per API 579, Fitness-For-Service 1. Also, at this higher magnification, the crack tip does
not appear to follow any obvious segregated foreign material or non-metallic inclusions. The sides of the
crack suggest that it may have originated as a "cold weld" instead of initiating as preferential weld
corrosion. It does not appear to have initiated during the pipe rupture. Microhardness measurements
taken next to the flaw using a Vickers indenter with a 3 kg load showed that the hardness of the ERW
weld was approximately HV 209. The base metal hardness, in comparison, averaged approximately HV
206. Figure 10 shows the pipe microstructure at a macroscopically brittle area. The subsurface crack is
probably similar to that shown in Figure 8.
I. D. Deposit/Scale Analysis Results. Figure 11 shows EDS elemental analysis results of deposits
removed from the pipe sample I. D. The deposits contained appreciable silicon, chlorine, copper, calcium
and sulfur, in addition to base metal elements. The chlorine and calcium probably originated from the
water in the pipeline. The sulfur probably originated from HzS known to be in the gas stream.
Chemical analysis results. Table 1 shows chemical analysis results of the pipe sample. The results
showed that the sample met API 5L, Specification For Line Pipe 2, Gr. B and X-42 chemical composition
requirements.
Tensile test results. Table 2 details tensile property results for the pipe sample. The results show that
the pipe met the yield, tensile and elongation requirements for both API 5L 2, Grs. B and X-42.
Charpy impact test results. Table 3 shows charpy impact test results for the pipe sample. The charpy
specimens were machined in the longitudinal orientation as the remaining sample thickness precluded
testing transverse samples. The ambient temperature and 32°F (0°C) charpy values show adequate
ductility. The relative lack of restraint of the subsize specimens, as compared with full size specimens,
probably does not permit an accurate discrimination of actual toughness differences between the two
temperatures. The lack of 100% shear suggests that the upper shelf energy of the pipe sample is probably
above room temperature.
DISCUSSION
Failure cause. The available evidence, analyses and tests showed that the pipe sample failed due to
brittle fracture at a groove-like flaw associated with an ERW weld seam. The pipe I. D. had thinned
3
considerably due to general corrosion. Based on the stream analysis and the appearance of the corrosion,
most of the I. D. corrosion was most probably due to wet CO2.
The open, fish mouth rupture suggested that the pipe failed at an appreciable internal pressure. However,
the exact operating pressure at the time of failure was not known. The pipe had historically operated at
pressures up to 750 psig (5.7 MPa); however, internal pressures before the failure were reported to be
385-450 psig (2.6-3.1MPa). The best pipe internal pressure estimate at failure was thought to be 385 psig
(2.6 MPa), based on the shutdown pressure setting of the compressor used in the attempt to remove the
hydrate blockage with upstream pressure.
Hoop stress calculations showed that the pipe should not have failed due to over pressure, given the
remaining wall thickness at the fracture. Based on an internal pressure of 385 psig (2.6MPa) and an
average remaining wall thickness at the brittle fracture of 0.157" (3.98 mm), the resultant calculated hoop
stress was approximately 13,200 psi (91 MPa) (17% of the actual yield strength and 31% of SMYS).
Calculation using the pipe sample's actual yield strength of 78,000 psi (537 MPa) suggested that a
uniform wall thickness of 0.02" should have been sufficient to contain an internal pressure of 385 psig
(2.6 MPa), not considering the groove-like flaw.
Brittle fracture considerations. Eliminating over pressure and low ductility as the root cause for the pipe
failure, led to consideration of brittle fracture as influencing the rupture. It was considered unusual for the
pipe to have experienced a low energy (brittle) fracture given its low carbon content, low hardness, low
remaining thickness and good charpy impact results. That the rupture followed the path of a groove-like
flaw associated with an ERW weld seam suggested that the groove might have influenced rupture. The
role of H2S in the failure was also considered, as H2S damage had been observed as I. D. blisters.
However, H2S sulfide stress cracking (SSC) was discounted, based on the pipe and ERW weld low
hardness.
To investigate the potential influence of longitudinal groove-like flaws contributing to the failure, a
"fitness-for-service" assessment was conducted. Several assessment methodologies were employed and
measured against each other for consistency of results and for their usefulness in explaining the pipe
failure. Remaining strength calculations were conducted, based on modifications to ANSI B31 G, Manual
for Determining the Remaining Strength of Corroded Pipelines 3, and classical fracture mechanics (FM)
analysis was performed, using two sources: (1) NG- 18 Report No. 208, Fracture Control Technology for
Natural Gas Pipelines 4 and, (2) FractureGraphic (1), a commercial fracture mechanics analysis software
program. Default lower bound toughness values for hydrogen charged carbon steel, as reported in API
5791, Appendix F, were used in the fracture mechanics analysis calculations. The different fitness-forservice methods used to determine the influence of the ERW weld flaw and material toughness were
compared with each other and with the known failed pipe material and mechanical properties.
Pipeline fractures have been known to propagate for several thousand feet, depending on the internal
pressure, the velocity of the propagating crack and the material toughness. The pipe crack propagated
approximately eight feet before arresting in shear fracture at each end. Several accepted and codified
methods have been developed for estimating the minimum charpy impact value to arrest a ductile crack,
5
4
including B31.8, Gas Transmission and Distribution Piping Systems and PRC NG-18 Report No. 208.
Figure 12 graphically details calculated NG-18 Report No. 208 4 minimum impact energies necessary to
arrest a ductile propagating crack, based on the pipe's hoop stress at failure as a percentage of the
specified minimum yield stress (SMYS) and average corroded thickness at the rupture. The various
formulas result in a large variation in required toughness; however, the pipe's tested charpy impact
1
FractureGraphic, Structural Reliability Technology, Boulder, CO.
4
4
toughness values were significantly greater than that required by the most conservative formula and
correlates well with the observed crack arrest observations.
As an input into the B31.G 3 remaining strength calculations and fracture mechanics analysis, detailed
dimensional measurements associated with the fracture were made. Thickness measurements along the
fracture were taken at one-inch intervals and groove lengths and depths were measured. Figure 13 shows
the pipe fracture sections with lines at the fracture locating the grooves. Figure 14 shows a graphical
display of the pipe thickness along the fracture with ductile vs. brittle fracture and groove lengths and
locations overlaid on the graph. Statistical analysis was conducted using the measurements to obtain a
uniform corroded remaining thickness at the fracture. The average corroded thickness along the fracture
length was 0.157" (3.98 mm), while the average thickness in the brittle sections where the fracture was
thought to have initiated was approximately 0.137" (3.48 mm). To arrive at an effective flaw length for
the FM calculations, the guidelines in API 579, Fitness-for-Service, were used to arrive at an effective
continuous flaw length based on discontinuous but proximate interacting flaws. In the fitness-for-service
analysis we used an effective continuous flaw length of approximately 20" (508 mm).
ANSI B31G 3 calculations.
Table 4 shows predicted burst pressures for the pipe, based on the software
program KAPA ©(2), which calculates predicted burst pressures based on the original B31 G, Remaining
Strength of Corroded Pipelines, equations, as well as later refinements to reduce conservatism in B31 G,
developed during a program conducted by Batelle Institute for The Pipeline Research Council in the late
1980's. The program (footnote 2) also calculates predicted burst pressures, based on a crack-like flaw,
given full size charpy impact data as an input. Table 4 suggests, that regardless of the calculation method,
the pipe should not have ruptured at the reported internal pressures and remaining measured wall
thicknesses.
NG-18 Report No. 2084 calculations. The PipeLine Research Council sponsored another program in the
early 1990's to develop a more classical fracture mechanics approach to control of fracture initiation and
fracture propagation. Fracture initiation and propagation control was based on a fracture analysis diagram
approach similar to that developed by the U.S. Navy, correlating charpy impact test results with drop
weight tear test (DWTT) results. The program resulted in the development of several software modules
to facilitate fracture analysis calculations. We used two modules, Plawl and Plaw2, to calculate the
limiting flaw size for the failed pipe. The two modules were based on two approaches to fracture, (1)
limiting toughness (PTFlaw2) and plastic instability (PTFlawl).
Figures 15 and 16 detail the analysis results using PTFlaw 1 and PTFlaw2. The curves show the critical
flaw length for a range of d/t ratios, based on the pipe dimensions, yield strength and in the case of
PTFlaw2, full size charpy impact energies. The curves show that the pipe should not have failed at the
internal pressures reported at the time of failure and with the tested charpy impact test results at infinite
flaw lengths.
Fracture mechanics analysis results. Figures 17 and 18 show the fracture mechanics (footnote 1)
analysis results. The analysis was conducted using a parametric correlation between various flaw d/t
ratios vs. operating pressures under hydrogen charged and uncharged conditions. The flaw depth was
assumed to be a constant 0.07" (1.78 mm) at various lengths. Default lower bound Kc values for
hydrogen-charged carbon steel were taken from API 579 ~, App. G. The upper shelf Kc value was taken
as 100 ksi-sq(in.) and the 15-ft-lb.(20-Joule) transition temperature was set at 15°F (-9C). The pipe was
considered to have been hydrotested and an estimated secondary stress of 15 ksi (105 MPa) was used to
account for residual weld stresses.
2
Kiefner & Associates Inc. Pipe Assessment, Worthington, OH.
3
5
Observing the tabular and graphical output for the uncharged condition, the results show that flaw lengths
up to 20" (508 mm) (the limiting flaw length considered) did not result in failure at operating pressures as
high as 450 psig (3.15 MPa). In comparison, using hydrogen-charged fracture toughness properties,
failure was predicted for a minimum 14" (355 mm) flaw length at 450 psig (31.5 MPa). The longest
measured groove-like flaw in the brittle fracture area was approximately seventeen inches.
CONCLUSIONS
°
Laboratory analysis of the 10" pipe sample showed that failure was due to brittle fracture.
Fracture occurred at a groove-like flaw associated with an ERW weld seam.
,
H2S in the line is thought to have contributed to failure by lowering the fracture toughness
properties of the pipe material.
,
,
The different fracture control methodologies used to assess the pipe fitness-for-service generally
agreed with each other and corroborated the influence of hydrogen lowering the fracture
toughness of the pipe as contributing to the pipe failure.
ACKNOWLEDGMENTS
I would like to greatly acknowledge the contributions of my co-authors in making this paper possible,
including Steve O'toole and Richard Mueller at Dynegy who gave the freedom to pursue a root cause
analysis and who helped with pipe data gathering and Ronald Frishmuth who conducted the fracture
mechanics analysis.
REFERENCES
API 579, Fitness-For-Service, American Petroleum Institute, Washington, D.C.
,
,
,
,
API 5L, Specification for Line Pipe, American Petroleum Institute, Washington, D.C.
ANSI B31G- 1991, Manual for Determining the Remaining Strength of Corroded Pipelines,
American Society for Mechanical Engineers, New York, NY
PRC NG-18 Report No. 208, Fracture Control Technology for Natural Gas Pipelines, Pipeline
Research Council of the American Gas Association.
ASME B31.8, Gas Transmission and Distribution Pipelines, American Society for Mechanical
Engineers, New York, NY.
6
Figure 1 -
As-received failed gas gathering pipe sample. The straight,
brittle looking fracture measured 97.5" (2.47 m) from arrest to
arrest point.
Figure 2 -
Acute angle arrest fracture at one end of the pipe sample.
7
Figure 3 -
i ilil ~ ;
I. D. of pipe sample showing uniform corrosion and blistered
areas.
/
....
Figure 4 -
........
,, . . . .
"! ~ . ~ . ~ . ~
Saw cut section of pipe at fracture termination showing the
fracture following a groove-like indication thought to be the
ERW weld seam.
8
: ,
;~;&::,~.ii,!~!.~ ~
Figure 5 -
Pipe O. D. showing cut lines for separating and identifying the
fracture for close up examination.
Figure 6 -
Typical fracture surface showing crack initiation from an I.D.
groove.
9
Figure 7 -
"Thumbnail fracture initiation site.
Figure 8 -
Representative SEM image of the pipe fracture surface. The
fracture includes both brittle and ductile features.
10
Figure 9 -
Pipe microstructure at the groove ahead of the crack arrest
front. The shape of the groove tip suggests that it may have
been pre existing, as compared with being formed during
corrosion. The groove was not following a line of segregated
material. 260X, 2% nital etch.
Figure 10 - Pipe microstructure at a brittle fracture location. The near
surface cracking corresponds to the secondary fracture
surface cracking in Figure 8. 260X, 2% nital etch.
11
'4
Figure 11
EDS Elemental Analysis of I. D. Scale/Deposits in a 10.75" (273 mm) O. D. Pipe Sample
!
i
...........
1
~,,,,...
,°°..,
: ............
.................
°
.....
, ..........
.
........................
: ................
, .......
~........................
........................
: ........................
:,..
~. . . . . . . . . . . . . . . . . . . . . . . .
: ..................
: ........................
~ ......
t
.....
° .....
; ........................
i
.....................
: ...................
,,.,...o,
: ...................
, ....
....
!
...........
i
i
1........................
..............
, .........
°. ....
1......
i!
!
i
°
s
...........
; ...........
°. . . .
3
!
i
°.°°
............. t: ....... '........................ !........................ i........................ i......
'
!
F ...... ~.......... L'
E g
. . . . .
......................................[2.....................i........................g......
,...:
....
...................... U ................ C
i
[
U
,.,,:..
0. 000
VF .S
Wt.
%
F
0.014
0.895
3.098
0.997
2.743
10.480
3.820
A1-K
0.003
0.957
2.439
0.997
2.327
1.02
0.420
Si-K
0.033
0.929
1.912
0.997
1.770
9.240
5.800
S -K
0.054
0.935
1.442
0.994
1.340
10.010
7.170
C1 -K
0.030
0.974
1.347
0.993
1.325
5.040
3.990
K -K
0.008
0.941
1.180
0.979
1.110
0.970
0.85
Ca-K
0.038
0.944
1.131
0.975
1.043
4.380
3.92
Fe-K
0.440
1.030
1.014
0.995
1.038
54.89
48.490
Cu-K
0.047
1.041
1.080
1.000
1.144
3.770
5.350
Total =
100.00%
0 -K
12
• !i~,~:, ~,
%
240
A
K-ratio
Atom
10.
Z
Element
ZAF
--. 1 0 2 4
[~
mm~
o~ul
t~
DD-
t~
oj~
o~n~
rJ~
c~
o
O0
c~
13
0
0
~k
0
c~
~k
o
o
0
c~
0
Lr~
o
o
0
0
~k
oo
c~
c~
II
Table 2
Tensile Test Results of a 10.75" (273 mm) O. D. API 5L Pipe Sample
Specimen No.
Width (in/mm)
Thick (in/mm) Y.S. (psi/MPa.)
T.S. (psi/MPa)
% Elongation
% ROA
01-0124-14
0.761/19.3
0.122/3.1
78,300/540
83,900/578
17.4
66.2
API 5L Gr. B
NA
NA
35,000/241
60,000/413
14.4 min.
NA
42,000/289
60,000/413
14.4 min.
NA
API 5L X-42
14
Table 3
Charpy Impact Test Results of a 10.75" (273 mm) O. D. API 5L Pipe Sample
Specimen No.
Temp (°F/°C)
Size (mm)
Notch Loc
Orientation
Sample 1
Sample 2
Sample 3
75/24
75/24
75/24
10 x 5
10 x 5
10 x 5
Base Metal
Base Metal
Base Metal
Long.
Long.
Long.
Sample 4
Sample 5
Sample 6
32/0
32/0
32/0
10 x 3.3
10 x 3.3
10 x 3.3
Base Metal
Base Metal
Base Metal
Long.
Long.
Long.
Ft-lbs/J.
Converted
% Shear
Lat. Exp.
27/37
25/34
27/37
54/73
50/68
54/73
80
80
80
68
64
64
17/23
19/26
17/23
51/69
57/77
51/69
80
90
90
61
59
60
Notes:
Per B31.8, para. 841.1, the min. required charpy energy value to arrest a ductile fracture = 9
ft-lbs. (12 Joules), based on an internal pressure o f ~ 4 5 0 psig (3MPa) and a thickness of
0.13" (3.3 mm) at the fracture.
Figure 12
Ductile Fracture Arrest Energy Curves
(From PRC D F A R R E S T Software)
35-
30
:!
10" Pipe Value
A
i'~,i,'li'~i'~iJi~' )~~' i~~2~i,'i~'i)'li~i!f~
~,i~i'
!ii!ii;'iii~:~' !i~' i,'~i
iiiii~iiiiiiiiiiiiiiiiiiiii!ii!i
~"
iii~' #' ,i~ii!i!i!i!i~' !'~i',i'iili!
~
L ~ ~
',i!iii',~iii~i~',ii~
,./j
,J-
~ ~
iiiiiiiii!iiiii!iiiiiiii
i~ii~~i'i!i~i!i!i!i~i
ii!iiiiii!i!!i!!iiiii
:::,'i'i~:'i'~:~;!:::i
~':i'i!:,:i'i::i:ui=:i:=~:
:~i'i~:ii'i:i:ii
i'!i:~:~i!',ii',i'i,~!',i!:~if!!ii!ii!i',',!',':!',':ii':i!',i',ii!i',i',i':',i;:ii;,~i,;,ii"i,i:,iiiiii',:,ii",!!i;i';i~,',~~;.:, ',~i!:i i:~i?,!i'',~iiii~i:;i!!i~,iii!ii'.i!:ii::i:ii!ii i~ii;'i:,~:~",':i~;:~i',!i~,~'~i~:',i!iiii!!i'~i!'i~!i!!:.i!!!iii::iiii!~ii'';i~ii~':iiiiii:~ii~:!;,,ii:~iiii',iii!iiiii';~i::i~';i',i!','~;~',iii~~.i!i~,!":i!~':i':',i!',i ii",!iWii?,i~"~i"i i:i::'~:~::~
~=~}'}'i;i'i'[~i
0i00
20.00
40 00
60.00
80.00
1:00.00
%SMYS
-Jr BMI ~
AISI -=- BGC -e- MANN - ~ CSM ~
JAPAN
15
f
.~i~,~ii~i,i~,~ii'i~ii;ii,!~ii
~¸~~,~ ;~,~~;~~ ~ ~
~i;? ~I! ; ;
Figure 13 -
Pipe fracture sections positioned to show the ductile vs.
brittle fracture and the location of observed ERW groove
(lines at fracture).
0.24
0.22
0.2
0, J 4
"
0,08
" , .....: ' , , , ' '
/-"\['"
,':,:;,,
Measurements
indicates a ERW ~-0ove
each tick mat'k = 1"
Figure 14 =
Graph showing the thickness profile along the fracture, ductile (d) fracture
vs. brittle (b) fracture and lengths of the ERW weld groove ( ....... ).
16
Table 4
Remaining Strength of Corroded Pipelines Analysis
(See footnote 2)
Analysis Method
Corrosion or blunt
groove
Crack-like defect
Predicted Failure Pressure
(psi/MPa)
Eff. Area
Mod. B31G
1211/8.5
1426/9.9
B31G
1121/7.8
Converted Hoop Stress
(psi/MPa))
Eft. Area
Mod. B31G i B31G
41,459/290
48,820/342
38,378/268
28,689/201
838/5.9
Data Input:
Pipe Diameter:
Wall Thickness:
Yield Strength:
Max. Pressure:
Design Factor:
Toughness:
Corroded dimensions:
10.75" (273 mm)
0.157" 3.98 mm)
78,300 (540 MPa)
385 psig (2.65 MPa)
0.85
53 ft-lbs. (72 Joules)
0.07" (178 mm)deep and 20" (508 mm) long
17
Figure 15
PRC Flawl Critical Flaw Size Based on Toughness
PRC Flaw2
I
Toughness
Dependent
Critical
Flaw
Size
ksi
iliiiiiii iiiiiiiiii ii i :; !iii'i!ii!
iiiiiiiiiiii~!iii!iiii~i!i0a~ii!iiii ~
~ i ~ ~
;
; 0
%
Hoop_.Stress
;
i iiiiii
at Failure
...... I ..... I
0.3
:::::.... .......:::...............................................................
"0:,0
4_
"'
I .... [ ...... I ..... [
0.9
'
J
I
[ .... I
I
2.1
I ..... I
I
I[
.... l
~
]
....
3.2
i
I
J ..... I .... ] ..... [
4.4
I
5.5
I I
l"'J
6.7
t:
I'"']'
i
7:8
Flaw length (in.)
Figure 16
PRC Flawl Critical Flaw Size Based on Plastic Instability
PRC Flaw1
Plasti c In stabil ity Criti cal Flaw Size
(10.75" x 0,153" X 78 ksi Y.S.)
iiiii!iii!iiiiiii~iiiiiiiiiiiiiiiiiiiiiiiiiii~iiiiili!i
!iiiiiiiiiiiiiiiiiiiiiiiiiiiiii!!i!ii!ii:iiii!iii!iiiiiiiiiiiiii
iiiiiiliiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii!!ili!i!i!if!iiiiiiiiiiiiiiiiiiii!iiiiii!iii!iiiiiiiiiiiiiii
iiiii!!!!i!ii!iiiiiiiiilli!iiiii!!!;:::!ii!!iSiiiiiiiiiiiiiiiiiiiii!iiii:iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~:
!ii!iiiiiiiiiiiiiiiii:iiiiiiii
iiiiii!ii!!iiliiiiiiii iiiiiiiiililli!!!!!ii!iiiiiiiiiiiiiii!iiiiiiiii!iiii!iiiiiiiiiiiiiiiiiiiiii!il !ili!ii~iiiiiiiiiiii
;~i~ii;ii;i;;i;iiiii~iii;iii;iii~iii{!i!;i;ii!i!iii~iiiii!iii~i~!ii:i~!i!~;i!;i~!i~i!i;i;~;i;i;iii;i;;~;;i;ii~;i;i;iii;;i~iiiiiii~iiiiiii!
:!~i~:;::;::i~i~i~i::}~;~i
iiiEi{!i!i!!ri!!J!ii
iiiiiiiiji!}i
ili:'iiii:{:-iiiiiiiii
iiiii;iiiii!i;iiiiiiiiiii~iiiiiii!iil;iiiiiiiiiiiiiiiiiiiiiiiiiii
iiiiiiiiiiiiii
iiiiiiiiiiiiiiiiiiiiiiiii
i!{ii'~,',i!{~iii'~i',iiiii',iiii{',ii!:.i~,6~'
',!',!i',}~
=_ =
~ii~!i~i~ii~i~i~i~ii~i~i~ii~i~iiii~i!i~i~i~! !i~i!i!J~i~!~i
-~-~~
...........
y~y;~y;;y;-;
...........
K~;:Z:Z~
...........
...........
...:..::.-::.-:.
.:..........::
.:.
...........
...........
(~y([~~y~y~
...........
-:-:-:-.:-::-:-.-:-:
..........
. . . . , ~ - ; - ~ - ~ ~ ~ - ' ~ ~ ' ~ ' ~ ' ~ ' ~ ' ~ t ~ ~ ~ ~ = ~~ ~ ~ ' ~
,~ .7,--.7.. .....,7,-
iiiiiUiii~iiOiiiii{iiiiiiiiiiii!i~iii~ii!i~i!!i~!!~ii~i~i~i~i{~ii~i~ii~ii~i~i~i~i~ii
ii i i i i i i i i~i~i i i i i i [i i i~i{i i i i i i~i i~i~~,i ii~~i~i~i~iii~iii~ii{~ii ~i
approximate
pipe h o o p s e s s
~iiiii!i%~i;i~i~i~i~i:i~i~!iii}ii!iji!iO
i~!i;i2~!{!~i
~iei!~i!a p p rox,
...................................................................
........................
•::.:. ............ .:::. : ...................
....................................................................
iiiiiiiiiiiiiiiiililil
...........
=_ =_ =_
iii!!iii~i~iii!!~i!i~i
8
!ii@i!!}i!!!ii!!i!i
iiiiiiiiiiiliiiiiiiili
. . . . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
i@iiiiiiiiii@i:i!
.
I
I
I
I
I
I
I
I
I
I
I
1
2
3
4
5
6
7
8
9
10
11
Critical Flaw Length
]-- TWC - * - . 2 d / t - = - . 4 d / t - = - . 5 d / t - ~
--]
J
18
.6 d / t -
.8 d/t /
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
12
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Figure 17
Fracture Analysis Results - Hydrogen Free Steel
1.0
-.=-
J__
0.9
0.8
m
0.7
cP
0.6
\
L_
0.5
0.4
0.3
0.2
0.1
0.0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Lr
Input
Outside Diameter (D):
Wall Thickness (t):
Flaw Length (2c):
Flaw Depth (a):
Internal Pressure
Default Sec. Stress (Sm):
Operating Temperature
Young's Modulus
Parent Metal Yield:
Parent Metal Tensile:
Estimated Kc:
15 ft-lb Transition Temp.
Upper Shelf Kc
Location
Inside
Inside
Inside
Inside
Inside
Inside
Inside
10.75" (273 mm)
0.135" (3.43 mm)
20" (508 mm)
0.07" (1.78 mm)
450 psi (3.15 MPa)
15,660 psi ( 109 MPa)
40F (4.4C)
30000 ksi (210,000 Mpa)
78,300 psi (548 MPa)
83,900 psi (587 MPa)
67.39 ksi-sq.(in.)
15F (-9C)
100 ksi-sq(in)
Output
Length (in./mm)
10/254
12/305
14/355
16/406
20/508
6/152
8/203
19
Depth (in.mm)
0.07/1.78
0.07/1.78
0.07/1.78
0.07/1.78
0.07/1.78
0.07/1.78
0.07/1.78
Pressure (psi/MPa)
385/2.7
385/2.7
385/2.7
385/2.7
385/2.7
450/3.2
450/3.2
Figure 18
Fracture Analysis Results - Hydrogen Charged Steel
1.2
1.0
0.8
0.6
\
0.4
0.2
0.0
0.0
0.2
0.6
0.4
0.8
1.0
1.2
Lr
Input
10.75" (273 mm)
0.135" (3.43 mm)
20" (508 mm)
0.07" (1.78 mm)
450 psi (3.15 MPa)
15,660 psi (109 MPa)
40F (4.4C)
30000 ksi (210,000 Mpa)
78,300 psi (548 MPa)
83,900 psi (587 MPa)
44.35 ksi-sq.(in.)
15F (-9C)
100 ksi-sq(in)
Outside Diameter (D):
Wall Thickness (t):
Flaw Length (2c):
Flaw Depth (a):
Internal Pressure
Default Sec. Stress (Sm):
Operating Temperature
Young's Modulus
Parent Metal Yield:
Parent Metal Tensile:
Estimated Kc:
15 ft-lb Transition Temp.
Upper Shelf Kc
Output
Location
Inside
Inside
Outside
Outside
Outside
Outside
Outside
Length (in/mm.)
10/254
12/305
14/355
16/406
20/508
6/152
8/203
Depth (in/mm.)
0.07/1.78
0.07/1.78
0.07/1.78
0.07/1.78
0.07/1.78
0.07/1.78
0.07/1.78
20
Pressure (psi/MPa)
385/2.7
385/2.7
385/2.7
385/2.7
385/2.7
450/3.2
450/3.2