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Notice

Pipeline Safety: Girth Weld Quality Issues Due to Improper Transitioning, Misalignment, and Welding Practices of Large Diameter Line Pipe

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Information about this document as published in the Federal Register.

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AGENCY:

Pipeline and Hazardous Materials Safety Administration (PHMSA); DOT.

ACTION:

Notice; issuance of advisory bulletin.

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.

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FOR FURTHER INFORMATION CONTACT:

Alan Mayberry by phone at 202-366-5124 or by e-mail at alan.mayberry@dot.gov.

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SUPPLEMENTARY INFORMATION:

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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 §§ 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 §§ 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, § 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 § 5.3—Hub Design, § 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 § 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 Start Printed Page 14245practices 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 §§ 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 §§ 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 §§ 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.

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Authority: 49 U.S.C. chapter 601 and 49 CFR 1.53.

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Issued in Washington, DC, on March 18, 2010.

Jeffrey D. Wiese,

Associate Administrator for Pipeline Safety.

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[FR Doc. 2010-6528 Filed 3-23-10; 8:45 am]

BILLING CODE 4910-60-P