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Pipleine Blast Inquiry
SCC, Stress-Corrossion Cracking
Review board urges strengthening
of safety measures,
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Publisher: Oilweek Online
Author: Gordon Jaremko
Issue: August 4, 1997, page 12
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A protracted investigation into a spectacular rupture, explosion and fire on TransCanada Pipleines Ltd.'s natural gas route across southern Manitoba has ended in recommendations for stronger safety precautions. Action is needed in case of still more breaks due to the national pipeline plague called SCC, or stress-corrossion cracking, says the inquiry report by the Transportation Safety Board of Canada.
While accepting the National Energy Board's 1996 decision to put healing SCC largely in industry's hands as a management problem, the safety board says TransCanada's spectacular accident July 29, 1995, spotlighted needs for action in areas other than metal fatigue.
Recommendations include steps to "harden" emergency shutdown systems against blast and fire damage, and to review the design of the systems at compressor stations. The safety board also voiced "concern" that there are no safety standards for horizontal spacing between multiple lines within single pipeline rights-of-way, although there are rules for vertical separation at crossings.
The inquiry found that when a 42-inch line ruptured and exploded near Rapid City due to SCC, the operator on the spot at a compressor station was unable to reach the regional operations controller in command, 200 kilometres away in Winnipeg, before the inferno drove him away. The worker, suffering cuts and bruises, eventually borrowed a cell phone from a bystander to reach the command post. Then it took nearly two hours to make the system carry out computer commands to cut off the flow of gas to the damaged part of the system. A thorough review of all the emergency facilities is what is recommended.
About 45 minutes after the first rupture, a second line only seven metres away ruptured and burst into flames due to stress and heat from the initial break. The explosions blew open 10.5 metres of the first line and 8.5 metres of the second, leaving a crater 23 metres wide, 51 metres long and five metres deep. ...
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