Commerce Report “It is clear that ERW pipe manufactured before about 1970 is particularly susceptible to failure,” the institute said in a 1989 report. It documented 172 seam failures in ERW pipelines carrying liquids over the previous 20 years. The research reported evidence that corrosion and metal fatigue caused by pressure changes from flowing liquids could worsen the pipe’s weld defects. Researchers recommended extra testing for ERW pipe and precautions such as installing cutoff valves to protect river crossings and populated areas. They also suggested companies consider replacing some of the pipe in sensitive areas. The Transportation Department advised pipeline companies in 1988 and 1989 to monitor ERW pipe more closely for corrosion and to either reduce the lines’ operating pressure or retest them to ensure they’re operating within safe limits. ‘Manufacturing Defect’ Previous tests of Exxon’s Pegasus pipeline that spilled 5,000 barrels of oil in Mayflower, Arkansas, earlier this year had discovered no problems, according to a May 10 PHMSA report. Conclusions drawn from another test just weeks prior to the rupture are not yet available. In a July statement, Exxon blamed the seam split on a “manufacturing defect,” after a study the company commissioned found small cracks that had worsened over time. In 2011 the Transportation Department began a $4.2 million study of ERW pipe failures and the adequacy of industry tests and possible alternatives. The study followed two high-profile pipeline disasters in 2010: a natural gas pipeline that exploded in San Bruno, California, killing eight people, and an Enbridge Inc. pipeline rupture that spilled 20,000 barrels of crude into a creek that feeds the Kalamazoo River outside Marshall, Michigan. Neither of the 2010 incidents involved ERW seam ruptures, but both involved pipes older than 40 years. The independent labs running the PHMSA study have produced preliminary reports confirming that inline “pigs” can’t always detect problems in older ERW pipe, and recommending a combination of pressure-testing and inline testing.
Posted on: Wed, 04 Sep 2013 03:42:29 +0000
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