Thermal expansion on elbow joint led to October 2013 pipeline rupture near Fort McMurray, Alberta

GATINEAU, QC, Nov. 3, 2015 /CNW Telbec/ - The Transportation Safety Board of Canada (TSB) today released its investigation report (P13H0107) into the 17 October 2013 rupture of a TransCanada PipeLines Limited pipeline after less than five years of service. The rupture of the 36-inch natural gas pipeline occurred at the North Central Corridor Loop of the Buffalo Creek West Section, located southwest of Fort McMurray, Alberta. An estimated 16.5 million cubic metres of natural gas was released. The rupture did not result in a fire, there were no injuries and no evacuation was required.

The investigation determined that a fracture initiated at an elbow joint and propagated through the wall thickness, resulting in the pipeline rupture. Thermal expansion had developed in the pipeline, causing increased stress at the elbow joint. This increased stress had occurred over a 50-day period when the pipeline was being operated at an increased discharge temperature to meet downstream customer demand.

The investigation determined that the elbow's internal pressure rating had been overstated as the calculation had used a wall thickness based on information from the manufacturing design drawings, instead of from a direct measurement. Additionally, the stress analysis had used a lower maximum operating temperature that did not fully address the potential operating envelope. These issues were not identified by TransCanada's quality assurance process.

Following the occurrence, the National Energy Board initiated an investigation to verify compliance with its regulations, and subsequently issued two Inspection Officer Orders to TransCanada. For its part, TransCanada performed a number of safety actions, including excavating, examining and reinforcing 16 elbows. TransCanada has also begun developing a parametric model which will be used to assess its pipelines for the threat of thermal expansion. Further, it has enhanced its third-party inspection requirements and auditing protocols to ensure that pipeline elbows and other fittings comply with the required standards and specifications.

The TSB is an independent agency that investigates marine, pipeline, railway and aviation transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.

The TSB is online at www.tsb.gc.ca. Keep up to date through RSS, Twitter (@TSBCanada), YouTube, Flickr and our blog.

SOURCE Transportation Safety Board of Canada

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