Seam Weld R&D Projects
Key Message: Recent failures in seam weld pipe have raised concerns within the pipeline industry, PHMSA, and National Transportation Safety Board (NTSB) over the integrity of such welded pipes. The NTSB determined that the probable cause of the November 2007, rupture of the liquid propane pipeline near Carmichael, Mississippi, was the failure of a weld that caused the pipe to fracture along the longitudinal seam weld, a portion of the upstream girth weld, and portions of the adjacent pipe joints. The Pipeline and Hazardous Materials Safety Administration’s (PMSA) Pipeline Safety R&D Program is evaluating potential applications to address the seam weld issues identified by NTSB.
Background: NTSB Recommendation (P-09-1): Safety and Performance of Electric Resistance Welded (ERW) Pipe called upon PHMSA to conduct a comprehensive study to identify actions that can be implemented by pipeline operators to eliminate catastrophic longitudinal seam failures in electronic resistance welded pipe. At a minimum, the study should include assessments of the effectiveness and effects of in-line inspection tools, hydrostatic pressure tests, and spike pressure tests; pipe materials strength characteristics and failure mechanisms; the effects of aging on ERW pipelines; operational factors; and data collection and predictive analysis.
Over the past several decades, U.S. Pipe manufacturing, construction and protection technological have implemented significant improvements. The following is an outline of those advancements.
- Electric arc welds were used to join pipe segments which was a great improvement over techniques employed previously
- Pre- 1930’s pipe were not protected with coatings or cathodic protection to inhibit rust
- 1935: ASME code B31.8 was issued, encompassing consensus standards for pipeline construction
- Beginning of wide use of cathodic protection (CP) for new construction
- of radiograph welds began
- Use Welder qualification and standards became general practice
- Hydrostatic testing began in the late 1940’s
- 1955 ASME B31.8 updated; became mandatory with the Pipeline Safety Act in 1968
- CP was applied to older pipelines
- Hydrostatic testing became widespread
- By the late 1960’s, improved low-carbon and alloy steel was used
- Transition from low frequency to high frequency electric resistance welds during 1965-1970
- Hydrostatic testing became mandatory with the Pipeline Safety Act in 1968.
Electric resistance welded (ERW) pipe is longitudinally welded pipe. A failure in the weld seam of this type of pipe can propagate for a distance along the pipe and can quickly release large quantities of product to the environment. Low-frequency (LF) ERW pipe installed prior to 1970 in particular can be susceptible to such failures. PHMSA issued advisory bulletins in 1988 and in 1989 on LF ERW pipe that was prone to failure, alerting industry of the need to have a monitoring and replacement program for LF ERW pipe. PHMSA conducted further studies in 2000 and 2003 on ERW pipe. Integrity management regulations have special provisions for evaluation of integrity threats for this type of pipe.
PHMSA ERW pipe related actions:
DOT/PHMSA Regulations: Related to Seam welds
- Gas - 49 CFR Part 192 – Subpart O – 192.917, 192.919, 192.921, 192.933, 192.937, and 192.939; New Pipe – 192.7 (reference to API 5L), Subpart B – all sections not listed, 192.113; Pipe - 192.103, 192.105, 192.107, 192.109, 192.111, 192.112, and 192.144
- Liquid – 49 CFR Part 195 – 195.3, 192.106, 195.114, 195.303, 195.452, and Appendix B
Program Accomplishments: In FY2004, the Pipeline Safety R&D Program completed a research project related to seam welds. A summary follows:
Assessment & Validation of TFI-Identified Anomalies Criteria for Repair and Available Repair Methods: Main Objective: The goal of this work was to develop a repair tool kit that will assist pipeline operators in determining available repair methods while defining anomalies in seam welds. The objectives were to (1) Compile and evaluate the unique properties of early generation pipeline welds seams. (2) Compile a catalog of defect types, and (3) develop methods for evaluating seam weld defects to determine whether pipeline integrity has been compromised.
Results: Following this methodology, the work provided an understanding of the types of defects and mechanical properties of early generation seam welds, and described methods of evaluation the severity of seam weld inspection technologies.
Seam weld defects are some of the integrity threats that are considered by pipeline operators in the development of integrity management plans. In particular, some early generation seam welds (e.g. prior to about 1970) can be more susceptible to failures because of poor mechanical properties (e.g. low toughness) that result in relatively small tolerable defect sizes (depth and length). For additional information go here.
Future Research plans:
REQUEST FOR FUTURE R&D: In FY2011, the Pipeline Safety R&D Program issued a Research Announcement (RA) #DTPH56-11-RA-000001 seeks research that will assist in the favorable closure of the NTSB recommendation. The work scope must develop a comprehensive project to understand the fracture/damage resistance and failure mechanisms in ERW pipe. The awardees team must provide real world samples with a statistically appropriate sample size representative of unflawed specimens, notched specimens, corroded specimens, and fatigued/pre-cracked specimens. The work scope must include how the effort may be relevant to ERW pipe, how results could impact consensus standards, and should include investigations relevant to both natural gas transmission and hazardous liquid pipelines.
In addition to a deliverable that addresses the NTSB report, PHMSA is interested in stimulating development and commercialization of new technology in this area. Other deliverables such as statistical review of seam weld failures in both natural gas transmission and hazardous liquid pipelines are also itemized in the solicitation. PHMSA data regarding these failures will be provided but gathering additional industry data will require coordination with industry trade organizations.
PIPELINE WELD SEAM INTEGRITY WORKSHOP: PHMSA Engineering and Research Office (PHP-80) are planning a 1-day workshop in mid-July 2011. The event objective is to provide an open forum for exchanging information on the challenges associated with pipeline longitudinal or spiral seam welds. This program will review pipe seam weld practices from past decades, and any integrity challenges in maintaining operating pipelines. Specifically the forum will facilitate individual, panel and working group discussions. The awardees team from the above solicitation will participate in this workshop as a deliverable task under the award documentation.