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APPOMATTOX — Outside corrosion caused the rupture and subsequent explosion in September of a natural gas pipeline just north of the town of Appomattox.
The analysis of Williams Gas Company’s pipeline showed that the thinning wasn’t fully captured by the tools used to examine the pipes in service, said John Batchelder, a pipeline integrity expert with the company.
“In the life of this pipeline, the coating became compromised,” he said. “The rocks in this ditch make it very difficult to protect this area.”
The in-line inspection tool, run on the pipeline earlier this year, showed that the pipe, as it crossed Virginia 26 just north of the town, showed some corrosion, but not enough to mark it for immediate repair. Its neighboring two pipelines had repairs in the same area recently.
“The initial results did not identify the corrosion as being as deep as it was,” Batchelder said. “This area has a unique signature of corrosion. It stretched the limits of the technology. We will take the learning we get from this and we will apply it throughout the industry.”
The new information into the cause of the explosion came days after the company applied to the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration to reinstate the line.
Larry Hjalmarson, vice president of operations, said if Williams’ application to run gas again in that line is approved, the company will start flowing gas at 640 pounds per square inch — 20 percent less than its capacity of 800 psi. It will run at that pressure through the winter before the company returns to PHMSA for approval to increase it to 800 psi.
Last month, Williams brought the A line back into full service and hopes to increase the pressure on the C line next spring.
About 2,500 feet of the B line’s pipe has been replaced since it exploded, said Rob Shoaf, pipeline integrity team leader with Williams. About 65 miles of pipe were inspected and some 49 sites along that span were excavated. The pipe was pressure tested with water earlier this month at 1,000 psi, the standard for new pipelines, Shoaf said.
“We feel very confident that this pipeline is safe and ready to return to service,” Shoaf said.
Hjalmarson said the earliest that Williams will receive approval to reinstate the B line will be Friday.
That pipeline failed just before 8 a.m. on Sept. 14. The natural gas it released blew into a fireball that scorched an area 1,125 feet in diameter, leveled two homes and injured five people, according to preliminary findings in the federal investigation. Some 100 homes were damaged in the blast, according to Hjalmarson.
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