TC Energy: Bending stress, weld flaw caused Keystone oil spill

TC Energy Corp. (TRP.TO) said last week that the Dec. 7, 2022, leak from its 622,000-b/d Keystone crude oil pipeline was due to a combination of factors, including bending stress on the pipe and a weld flaw at a pipe-to-fitting girth weld completed during fabrication.

“Although welding inspection and testing were conducted within applicable codes and standards, the weld flaw led to a crack that propagated over time as a result of bending stress fatigue, eventually leading to an instantaneous rupture,” TC Energy said. “The cause of the bending stress remains under investigation as part of the broader third-party root cause failure analysis.”

Metallurgical analysis identified no issues with the strength or material properties of the pipe or manufactured fitting, according to the company, which added that the pipeline was operating within its operational design and within the pipeline design maximum operating pressure. Investigation by the US Pipeline and Hazardous Materials Safety Administration is ongoing.

The line was shut after spilling 12,937 bbl of oil in rural Washington County, Kansas. TC Energy expects repairs and remediation to cost $480 million.

The company is operating Keystone at reduced pressure while it continues its response and investigation. It began a controlled restart late last year (OGJ Online, Jan. 2, 2023). “Our team is progressing a remediation plan, including an analysis of other areas with potentially similar conditions, the use of additional in-line inspections, and further operational mitigations,” TC Energy said.