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PHMSA Says Corrosion Possible Cause of Tetco NatGas Explosion

Federal regulators said the preliminary investigation of what caused a massive explosion and fire on the Texas Eastern (Tetco) pipeline in Southwest Pennsylvania shows evidence of corrosion at two areas on the affected pipe, one of which was at the point of failure.

The Pipeline and Hazardous Materials Safety Administration (PHMSA), which is leading the investigation, detailed the early findings in a corrective action order it issued to Spectra Energy Corp. subsidiary Texas Eastern Transmission LP. The agency said the cause of the failure is still unknown, but it said investigators had identified corrosion along two of the pipe's circumferential welds, including at the point of failure and on another piece excavated shortly after PHMSA arrived on scene.

The failed pipe section, the order said, is being transported to an independent metallurgist for examination and failure analysis.

"The pattern of corrosion indicates a possible flaw in the coating material applied to girth weld joints following construction welding procedures in the field at the time," PHMSA said in its order.

The blast and subsequent fire were reported at about 8:30 a.m. EDT last Friday on Tetco's Penn-Jersey Line in the M3 Zone, toppling trees, razing one house, damaging others and sending one resident to the hospital with burns (see Shale DailyApril 29). The blast occurred in an area where four pipelines run parallel to one another in Westmoreland County’s Salem Township, about 30 miles east of Pittsburgh. The one that ruptured, Spectra said, was a 30-inch line built in 1981.

Spectra said in an update on Wednesday an inline inspection in 2012 "revealed no areas requiring repair or remediation before the next inspection." The company said it would continue to support the ongoing investigation.

The corrective order requires Spectra to take several immediate actions to determine the cause of the incident and ensure the safety of the three nearby pipelines that could have been affected by the failure before they can be restarted. PHMSA said those pipelines remained shut down on Wednesday under its authority. The agency also said that it could amend its order to require additional action as the investigation continues and added that enforcement action, such as civil penalties or referral for a criminal investigation, are possible.

Flows beginning at the Delmont compressor -- the western boundary of the M3 zone -- have been cut to zero, with flows affected eastward. The outage has cut about 1 Bcf/d of natural gas flows on the system (see Shale DailyMay 2). Spectra had said that flows through Delmont would remain at zero through Tuesday (May 3), but said in an update the restriction had been extended to Saturday (May 6). 

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