Defects

El Paso Natural Gas Co. said there was no evidence of corrosion, weld defects, prior gas leakage or slow-developing cracks in the “branch” or “tap” connection of a pipeline that ruptured and exploded Nov. 5 in Bushland, TX. “Instead, we learned the rupture was the result of an upward force on the branch connection that put pressure on a small area on the carrier pipe that contained a ‘lamination.’ The force on the lamination caused a fracture to develop in the lamination near the weld of the branch connection to the carrier pipe, resulting in the rupture,” El Paso said. A lamination is a tiny area of separation within a pipe wall where the metal has not properly bonded to itself, and the lamination feature was not a defect under the regulations of the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration, the company said. Stress Engineering Services Inc. conducted the metallurgical analysis; “We don’t know yet what caused the upward force on the branch connection,” El Paso said. Information about the investigation is at www.elpaso.com/bushlandinfo.