PHMSA Finds Last Year's Leidy Pipeline Rupture Caused by Corrosion
September 23, 2016
The rupture that knocked out full-service on a part of Williams' Leidy Line in Northeast Pennsylvania in June 2015 was caused by corrosion, according to a report from the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA).
The report, released over the summer, said the cause of the failure on Leidy line B near Unityville, PA, was "near-neutral stress corrosion cracking of the pipe." Shielding and coating failure, in addition to "cyclic pressures during bidirectional flow" were also identified as leading causes, PHMSA said.
Leidy delivers Marcellus Shale natural gas from Northeast Pennsylvania to the Transcontinental Gas Pipe Line. A bidirectional system consisting of multiple pipes, the Leidy Line is capable of moving 3.5 Bcf/d. The failure occurred on a 24-inch diameter section of the line where it runs parallel to two others on June 9, 2015 (see Daily GPI, June 23, 2015; June 11, 2015). At the time, residents in the area reported hearing a loud roaring sound when the pipeline failed. About 150 people were evacuated by first responders as a precaution.
PHMSA said 96.4 MMcf of natural gas was released in the rupture. No injuries were reported and the incident caused "minimal environmental damage," the report said. Volumes on the system were not significantly affected. The company was able to reroute gas and make deliveries through the A and C lines, which were returned to normal operating pressures just a few days later.
PHMSA's investigation revealed that on the morning of the incident, Williams personnel repositioned valves on line B to allow gas to flow west to Leidy Storage. A review of records showed pressure slowly increased throughout the day. But the agency said operating pressure at the time of failure was 1,141 psi, which was below the 1,200 psi maximum allowable operating pressure.
The line was installed in 1963 and had no history of corrosion. A portion of the Texas Eastern pipeline, known as the Penn-Jersey system, exploded and caught fire in April in Westmoreland County, PA, causing significant property damage and severely burning one resident (see Daily GPI, April 29). In a preliminary investigation of that incident, PHMSA said corrosion was the likely cause (see Daily GPI, May 4). Spectra Energy later said that a failed tape coating likely contributed to the corrosion (see Daily GPI, Sept. 14).
Section of Leidy Line Remains Out of Service After Rupture
June 23, 2015
A section of Williams' Leidy Line in northeast Pennsylvania that ruptured earlier this month remains out of service, and the company does not yet know when repairs will be completed, a spokesman said.
The line ruptured June 9 in Lycoming County, prompting the evacuation of more than 100 residents and forcing Williams to reroute natural gas in the area (see Daily GPI, June 11). No injuries were reported, and the evacuation order was lifted hours later.
The U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) issued a Corrective Action Order on June 12, authorizing the company to return the line to full service, spokesman Chris Stockton said. But he added Monday that "the timeline for complete restoration of service on the line has not been determined at this time."
Leidy delivers Marcellus Shale natural gas from northeast Pennsylvania to the Transcontinental Gas Pipeline (Transco). A bidirectional system consisting of multiple pipes, the Leidy Line is capable of moving 3.5 Bcf/d. Both Williams and PHMSA are continuing to investigate the cause of the failure.
Volumes on the system have not been curtailed, with no impact to natural gas receipts or deliveries. Stockton said the rupture occurred on a 14-mile segment of Leidy's B line. The company is rerouting gas and making deliveries through the A and C lines, which run parallel to the isolated segment, he said.
Last week, the failed pipe section was shipped to an independent metallurgist to help determine the cause of the failure. Stockton said it would likely "take several months before the root cause analysis is complete and the exact cause determined."