Crack caused 2024 pipeline explosion near Edson

A pipeline explosion on April 16, 2024, created a roughly 450-square metre crater. (Source: Transportation Safety Board of Canada)

A pipeline rupture and explosion near Edson in 2024 was caused by a pre-existing crack in the pipeline, a Transportation Safety Board (TSB) of Canada investigation has revealed.

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The crack in the 36-inch (914 mm) sweet natural gas pipeline owned by NOVA Gas Transmission Ltd.and operated by TC Energy 36.5 kilometres northwest of Edson was first detected in 2022 by an in-line inspection.

However, it was classified as non-reportable by service provider Baker Hughes and therefore not included in operator TC Energy’s inspection analysis process or risk assessment, according to TSB’s findings, released on Thursday.

On April 16, 2024, the pipeline’s operating pressure increased to a level that caused the crack to rupture.

No one was hurt but nearly six million cubic metres of natural gas were released.

While TSB acknowledged in-line inspections are invaluable to pipeline management, it concluded there is an element of risk because “the process relies heavily on human interpretation.”

“As such, the variability of human performance introduces the possibility that a pipeline crack may not be identified, resulting in a missed opportunity to manage it,” TSB said on Thursday.

In-line inspections are done by a device that moves through a pipeline, detecting potential issues, or “features.”

In 2022, the technology identified a “potential feature of interest” at the site of the 2024 rupture. Quality control later labelled the anomaly as a “crack field” with an estimated depth of 3.2 millimetres. A review committee of four analysts unanimously agreed to downgrade the “crack field” classification to the non-reportable “metal loss” feature classification because the data did not suggest a crack.

The committee review is supposed to be one of multiple layers of quality control in the inspection process.

This is the only time where a misidentified feature has led to a pipeline failure since the Baker Hughes inspection process has been in place, TSB also reported.

The pipeline has since been operating under pressure restrictions.

Baker Hughes now requires committee reviews to record their rationale for changes in feature classification.