El Paso Natural Gas Co. provided an update Tuesday on the investigation into a rupture and explosion on its pipeline that occurred Nov. 5 in the Texas Panhandle in the Prairie West subdivision of the town of Bushland.

Three people were hospitalized with burns after the 24-inch diameter line exploded early in the morning (see Daily GPI, Nov. 6).

The company said it has been working with the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) to determine the cause. El Paso transported the damaged pipeline elements to an independent metallurgical lab in Texas called Stress Engineering Services Inc.

Stress Engineering conducted a metallurgical analysis to determine the mechanism of the failure that led to the rupture. The main focus was a component known as a “branch” or “tap” connection, which attaches to the main pipeline and enables local deliveries of gas. Stress Engineering has issued its final report. Key findings from the report that were provided to El Paso and PHMSA said there was no:

“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. Here, the lamination was about 0.8 of an inch long and 0.25 of an inch wide. Stress Engineering determined that the existence of the lamination feature was not a defect under PHMSA regulations, El Paso said.

“We don’t know yet what caused the upward force on the branch connection,” the pipeline said. “However, we will use this analysis from Stress Engineering, along with other scientific inquiry, to aid us in our continuing work to learn what led up to the failure as well as to determine appropriate actions to take in the future.”

Information about the incident and the company’s investigation is at www.elpaso.com/bushlandinfo.

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