Pipeline
Safety: Girth Weld Quality Issues Due to Improper Transitioning, Misalignment, and Welding
Practices of Large Diameter Line Pipe
AGENCY: Pipeline and Hazardous Materials Safety Administration
(PHMSA); DOT.
ACTION: Notice; issuance of advisory bulletin.
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SUMMARY: PHMSA is issuing an advisory bulletin to notify owners
and operators of recently constructed large diameter natural gas pipeline and
hazardous liquid pipeline systems of the potential for girth weld failures due
to welding quality issues. Misalignment during welding of large diameter line
pipe may cause in-service leaks and ruptures at pressures well below 72 percent
specified minimum yield strength (SMYS). PHMSA has reviewed several recent projects
constructed in 2008 and 2009 with 20-inch or greater diameter, grade X70 and
higher line pipe. Metallurgical testing results of failed girth welds in pipe
wall thickness transitions have found pipe segments with line pipe weld misalignment,
improper bevel and wall thickness transitions, and other improper welding
practices that occurred during construction. A number of the failures were located in
pipeline segments with concentrated external loading due to support and
backfill issues. Owners and operators of recently constructed large diameter
pipelines should evaluate these lines for potential girth weld failures due to misalignment
and other issues by reviewing construction and operating records and conducting
engineering reviews as necessary.
I. Background
The Federal pipeline safety regulations in 49 CFR Parts 192 and
195 require operators of natural gas transmission, distribution, and hazardous
liquids pipeline systems to construct their pipelines using pipe, fittings, and
bends manufactured in accordance with 49 CFR Sec. Sec. 192.7, 192.53, 192.55, 192.143, 192.144,
192.149, 195.3, 195.101, 195.112, and 195.118 and incorporated standards and
listed design specifications. This involves reviewing the manufacturing procedure
specification details for weld end conditions for the line pipe, fitting, bend,
or other appurtenance from the manufacturer to ensure weld end conditions are
acceptable for girth welding.
During the 2008 and 2009 pipeline construction periods, several
newly constructed large diameter, 20-inch or greater, high strength (API 5L X70
and X80) natural gas and hazardous liquid pipelines experienced field
hydrostatic test failures, in-service leaks, or in-service failures of line
pipe girth welds. Post-incident metallurgical and mechanical tests and
inspections of the line pipe, fittings, bends, and other appurtenances
indicated pipe with weld misalignment, improper bevels of transitions, improper
back welds, and improper support of the pipe and appurtenances. In some cases,
pipe end conditions did not meet the design and construction requirements of
the applicable standards including:
·
American Petroleum Institute (API),
Specification for Line Pipe--5L, (API 5L), 43rd (including Table 8--Tolerance
for Diameter at Pipe Ends and Table 9--Tolerances for Wall Thickness) or 44th
editions for the specified pipe grade;
·
API 1104, 19th and 20th editions, Welding of
Pipelines and Related Facilities;
·
American Society of Mechanical Engineers (ASME)
B31.8, Gas Transmission and Distribution Piping Systems or ASME B31.4 Pipeline Transportation
Systems for Liquid Hydrocarbons and Other Liquids; and
·
Manufacturers Standardization Society of the Valve
and Fittings Industry, Inc. (MSS) MSS-SP-44-1996 Steel Pipeline Flanges and MSS
MSS-SP-75-2004 Specification for High-Test, Wrought, Butt-Welding Fittings.
Post-incident findings were that in some cases the pipe and induction
bend girth weld bevels were not properly transitioned and aligned during
welding. In some cases, the girth weld pipe ends did not meet API 5L pipe end
diameter and diameter out-of-roundness specifications. Many of the problematic
girth welds did not meet API 1104 misalignment and allowable ``high-low''
criteria. Some girth welds that failed
in-service had non-destructive testing (NDT) quality control problems. NDT
procedures, including radiographic film and radiation source selection, were
not properly optimized for weld defect detection and repairs. This was
particularly the case where there were large variations in wall thickness at
transitions. In some situations, NDT procedures were not completed in
accordance with established API 1104 and operator procedures.
Many of the integrity issues with transition girth welds were present
on pipelines being constructed in hilly terrain and high stress concentration
locations such as at crossings, streams, and sloping hillsides with unstable
soils. These girth welds had high stress concentrations in the girth weld
transitions due to the combination of large variations in wall thickness and
improper internal bevels with inadequate pipe support, poor backfill practices
and soil movement due to construction activities.
II. Advisory Bulletin ADB-10-03
To: Owners and Operators of Hazardous Liquid and Natural
Gas Pipeline Systems.
Subject: Girth Weld Quality Issues Due to Improper
Transitioning, Misalignment, and Welding Practices of Large Diameter Line Pipe.
Advisory: Owners
and operators of recently constructed large diameter pipelines should evaluate
these lines for potential girth weld failures due to misalignment and other
issues by reviewing construction and operating records and conducting
engineering reviews as necessary.
The assessments should cover all large diameter, 20-inch or
greater, high strength line pipe transitions and cut factory bends or induction
bends installed during 2008 and 2009, and should include material specifications,
field construction procedures, caliper tool results, deformation tool results,
welding procedures including back welding, NDT records, and any failures or
leaks during hydrostatic testing or in-service operations to identify systemic
problems with pipe girth weld geometry/out-of-roundness, diameter tolerance,
and wall thickness variations that may be defective.
The reviews should ensure that pipelines were constructed in compliance
with the Federal pipeline safety regulations in 49 CFR Parts 192 and 195.
Operators of natural gas transmission, distribution, and hazardous liquids
pipeline systems are required to use pipe and fittings manufactured in
accordance with 49 CFR Sec. Sec. 192.7, 192.53,
192.55, 192.143, 192.144, 192.149, 195.3, 195.101, 195.112, and 195.118 and
incorporated standards and listed design specifications.
With respect to the construction process, pipe, fittings,
factory bends, and induction bends must be made in accordance with the applicable
standards to ensure that weld end dimension tolerances are met for the pipe end
diameter and diameter out-of-roundness. API 1104 specifies girth weld
misalignment and allowable ``high-low'' criteria. API 1104--19th edition,
Sec. 7.2, Alignment, specifies for pipe
ends of the same nominal thickness that the offset should not exceed \1/8\ inch
(3mm) and when there is greater misalignment, it shall be uniformly distributed
around the circumference of the pipe, fitting, bend, and other appurtenance.
ASME B31.4, Figure 434.8.6(a)-(2), Acceptable Butt Welded Joint Design for
Unequal Wall Thickness and ASME B31.8, Figure I5, Acceptable Design for Unequal
Wall Thickness, give guidance for wall thickness variations and weld bevels
designs for transitions. API 5L, 43rd edition in Table 8--Tolerance for
Diameter at Pipe Ends and Table 9--Tolerances for Wall Thickness, specifies tolerances
for pipe wall thickness and pipe end conditions for diameter and diameter
out-of-roundness. MSS-SP-44-1996 specifies weld end tolerances in Sec. 5.3--Hub Design, Sec. 5.4--Welding End, Figure 1--Acceptable
Designs for Unequal Wall Thickness, and Figures 2 and 3; and MSS-75-2004
specifies weld end tolerances in Sec. 13.3
and Figures 1, 2, and 3 and Table 3--Tolerances.
Pipeline owners and operators should closely review the manufacturing
procedure specifications for the production, rolling, and bending of the steel
pipe, fittings, bends, and other appurtenances to make sure that pipe end
conditions (diameter and out of roundness tolerances) and transition bevels are
suitable for girth welding. Pipeline owners and operators should request or
specify manufacturing procedure specification details for weld end conditions
for the line pipe, fitting, bend, or other appurtenance from the manufacturer
to ensure weld end conditions are acceptable for girth welding.
To ensure the integrity of the pipeline, field personnel that
weld line pipe, fittings, bends, and other appurtenances must be qualified, follow
qualified procedures, and operators must document the work performed. Operators
should verify that field practices are conforming to API 5L, API 1104, ASME
B31.4 or ASME B31.8 and operator procedures for weld bevel, pipe alignment,
back welding, and transitions.
If any bends are cut, the operator must have procedures
to ensure that the pipe or bend cut ends are acceptable for welding in
accordance with the listed specifications. Procedures, inspection, and
documentation must be in place to ensure that when pipe, fittings, bends, and
other appurtenances are welded, the field girth welds are made and
non-destructively tested in accordance with 49 CFR Sec. Sec. 192.241, 192.243, 192.245, 195.228, 195.230,
and 195.234. NDT procedures including film type and radiation source selection
should be optimized for weld defect detection and repairs completed in
accordance with established welding procedures. When there is a variation in
wall thickness between line pipe and a segmented fitting, bend, or other
appurtenance, consideration should be given to the installation of a segment of
intermediate wall thickness pipe. Additionally, efforts should be taken to
ensure pipe girth weld alignment is optimized by utilizing experienced and
trained welders, suitable pipe and detailed procedures.
Each material component of a pipeline such as line pipe,
fittings, bends, and other appurtenances must be able to withstand operating pressures
and other anticipated external loadings without impairment of its
serviceability in accordance with 49 CFR Sec. Sec. 192.143 and 195.110. In order to ensure
pipeline integrity, the operator must take all practicable steps to protect
each transmission line from abnormal loads while backfilling and other work
continues along the right-of-way and to minimize loads in accordance with 49
CFR Sec. Sec. 192.317, 192.319,
195.246(a), and 195.252. Operators should give special attention to girth welds
with variations in wall thickness when located in pipeline segments where
significant pipe support and backfill settlement issues after installation may
be present, specifically in hilly terrain and high stress concentration
locations such as at crossings, streams, and sloping hill sides with unstable
soils.
Even if no girth weld concerns are identified by reviewing construction
records, if an operator has any knowledge, findings or operating history that
leads it to believe that its newly constructed, high material grade, large
diameter, line pipe segments contain these type girth weld transitions, the
operator should conduct engineering reviews as described above with those
operating pipelines to ensure that material, engineering design, and field
construction procedures were in compliance with 49 CFR Parts 192 and 195.
Failure to conduct engineering reviews and to remediate findings may compromise
the safe operation of the pipeline.
Authority: 49 U.S.C.
chapter 601 and 49 CFR 1.53.
Issued in Washington, DC, on March 18, 2010.
Jeffrey D. Wiese,
Associate Administrator for Pipeline Safety.
[FR Doc. 2010-6528 Filed 3-23-10; 8:45 am]
BILLING CODE 4910-60-P