DMONTON — The Transportation Safety Board says external corrosion led to a natural gas pipeline rupture that caused an explosion near a small northwestern Alberta community.
In a statement on the results of its investigation into the April 2022 blast near Fox Creek, Alta., the agency says it found the corrosion had weakened the pipeline wall, leading to the rupture.
It says the escaped gas ignited, causing a fire that "self-extinguished" after the manual closing of valves upstream and downstream of the break.
No injuries or evacuations resulted from the explosion.
The board says the investigation found the cathodic protection system meant to prevent corrosion wasn't working as intended, and the external coating of the pipeline had degraded over time, exposing its surface to the environment.
It says factors that quickened the corrosion included proximity to another pipeline with a different operator, the characteristics of the soil, the degraded coating and an incomplete electrical bond in the cathodic protection system.
The board says the effectiveness of such systems, which use electrical currents to transfer corrosion away from the surface, may be compromised if pipeline operators aren't aware of similar infrastructure operated by others nearby, adding there is no centralized system for that information in Canada.
In the case of the rupture near Fox Creek, the Transportation Safety Board says the operator of the pipeline, NOVA Gas Transmission Ltd., replaced the damaged sections and took steps to permanently shut down the pipeline.
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