Pipe corrosion caused 2011 oil refinery explosion

REGINA (Canadian OH&S News)

A single small crack in the more than one million feet of pipe covering almost 640 acres of a Saskatchewan oil refinery was all it took to create a major explosion that injured 52 workers last year.

An investigation into the October 2011 explosion at the Co-operative Refineries Limited (CCRL) crude oil refinery in Regina [COHSN, Oct. 17, 2011] found that a six-inch diameter line that was carrying hydrogen gas, hydrogen sulphide and diesel gas suffered a catastrophic failure, and the intensity of the explosion caused four other hydrogen sulphide lines to breach, compounding the incident.

“In the highly unlikely event that something like that happens, once you have that hydrocarbon with certain mixtures, there’s not much you can do other than have your emergency systems in order,” said Bud Van Iderstine, senior vice-president of refinery operations at CCRL.

The province’s Ministry of Labour Relations and Workplace Safety oh&s investigation is still ongoing, and the source of the ignition that caused the gas to explode has yet to be determined.

“In a situation like that, with diesel hydrocarbon mixed with hydrogen and that temperature, the ignition was inevitable,” said Vic Huard, CCRL’s vice-president of corporate affairs, noting that the static created from the velocity at which the gas was escaping from the pipe could have caused the ignition.

The investigation found the 7.5-inch rupture was caused by corrosion and uniform wall thinning along the upper half of the pipe from the pressure of the gas and high operating temperatures. The walls of the pipe were much thinner than the pipes it was connected to, and previous inspections of the pipe were within the acceptable limits, a news release noted, adding that changes to the refining process in 2008 could have caused the higher-than-usual corrosion rate.

“Our monitoring and follow up inspection detected those changes and as a result we then replaced a section of pipe. Our inspection protocols and judgment led us to believe we had identified all problem areas and made the necessary pipe replacement,” said Scott Banda, CEO of Federated Co-operatives Limited, which owns CCRL. “Unfortunately that was not the case.”

The pipe that burst was last inspected in 2010 as part of a maintenance turn-around, said Huard, noting that since the incident, the company has done a full visual and X-ray inspection of the 94,000 inspection points for all the pipes in the complex.

Only one 20-foot section of pipe needed to be replaced, Van Iderstine said.

All piping in the area that was damaged by the fire has been replaced, a news release noted, as well as 80 per cent of the piping in the diesel processing area, where the explosion occurred and which was under renovation at the time.

“We accept the responsibility for what happened on Oct. 6,” said Huard. “Clearly we can do better.”

The company also noted 19 actions taken in response to the event, including written procedures that outline how pipe wall thickness monitoring locations are determined and the actions and additional inspection that must be done if high corrosion rates are detected.

Regarding the company’s emergency response protocol, Van Iderstine said there have not been any major changes since the incident.

“Our emergency response that day was particularly good. We have had tremendous feedback from our own employees, from the fire commission from the contractors in our plant thanking us and congratulating us on what we did that day,” he said.

There were a total of 52 injuries in the explosion, with three hospitalizations. Workers at the refinery were given a week off after the incident to deal with any emotional issues they may have experienced.

“In an industrial complex the size of the refinery, we can never say with 100 per cent certainty that this type of incident will never happen again. What we can promise is to always strive for continuous improvement in all aspects of our operations including personnel and public safety and equipment and process integrity,” said Banda.

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