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Pipeline failure inquiry - Mill Woods area, Canada. March 1976

Accident summary

The Rimbley pipeline system in Alberta, Canada transports liquid propane, butane and condensate products in an 8-inch pipeline. On the day of the incident the operating pumps were pumping against a closed valve. The line failed at a pressure of approximately 8000 kPa, which is below the 8372 kPa maximum operating pressure for the pipeline.

Liquid propane erupted violently and formed a pond of boiling propane. The propane quickly formed a ground level flammable gas cloud, which rolled across topsoil until it reached a road where it was ignited by a passing truck. Liquid propane entered a nearby storm sewer catchment basin. The propane spread into adjacent sewer lines. Explosive mixtures were detected over a wide area within the sewer system.

No injuries were recorded, however the incident instigated a large-scale evacuation of 19,000 people while efforts were made to eliminate the explosive danger.

A combination of water flushing, ventilation and nitrogen gas blanketing successfully eliminated the danger about 23 hours after the original fracture. Maintenance crews plugged the pipeline either side of the fracture to stop the flow of leaking gas.

Failings in technical measures

References

‘Pipeline Failure Inquiry - Mill Woods Area’, Energy Resources Conservation Board, Alberta, Canada, 1980.

Alberta Energy Resources Conservation Board, ‘Pipeline failure inquiry : Mill Woods area, Edmonton : Post-inquiry progress review’, Published: Calgary : Energy Resources Conservation Board, 1980. 

Alberta Energy Resources Conservation Board, ‘Pipeline failure inquiry : Mill Woods area, Edmonton : Decision report’, Published: Calgary : Energy Resources Conservation Board, May 1973. 

2010-02-11