The early-2014 rupture of a natural gas pipeline south of Winnipeg, Man., resulted from a fracture at a crack that formed in the pipe wall during construction but remained stable more than 50 years, according to the Transportation Safety Board of Canada (OGJ, Feb. 3, 2014, Newsletter).
A TSB statement said the crack probably resulted from “inadequate welding procedure and poor welding quality.” It noted there was no requirement for radiographic inspections of every weld when TransCanada PipeLines Ltd. Line 400-1 was laid.
Incremental stresses caused the fracture at a mainline valve near Otterburne, TSB said in its investigation report. They resulted from factors such as weakened soil support due to years of pipeline maintenance, record-low temperatures, recent work at and around the valve site that might have driven frost deeper into the ground, and thermal contraction that might have occurred when the pipeline cooled due to the absence of gas flow for 20 days before the rupture and brief fire.
The incident caused no injuries or environmental damage. TransCanada returned the pipeline to service after performing investigations and tests.