Report: Worn Valve Caused Explosion at Superior Refinery

August 02, 2018 06:40 PM

The explosion at the Husky Refinery in Superior, Wis. on April 26 was determined to stem from a worn valve that converts oil to gasoline. The possible cause was part of a U.S. Chemical Safety Board factual update released Thursday as part of the board's ongoing investigation. 

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"Disassembly and evaluation of the spent catalyst slide valve revealed internal wear that could have allowed catalyst flow through the valve even when the valve was in the closed position," the CSB stated. 

RELATED: Superior Refinery Explosion Caused $27M in Damage, $53M in Expenses; 2020 Restart

The blast happened in the refinery's fluid catalytic cracking unit, which was being shut down for routine maintenance on the day of the explosion. The unit converts hydrocarbons in petroleum into gasoline. During the maintenance shutdown, conditions existed that could have allowed air to flow backward through a worn valve and into an area containing flammable hydrocarbons, the report found. Mixing air with hydrocarbons can cause an explosion.

The explosion happened while workers were on a scheduled break, and many were in blast-resistant buildings or away from the blast area, according to the report.

The report said 36 people sought medical attention after the explosion, including 11 refinery and contract workers. A large part of Superior was evacuated.

On July 26, Husky Energy announced they are not expected to resume normal operations until 2020. The Calgary, Alberta-based company said it has incurred about $53 million in expenses related to the incident. The company also said the incident caused $27 million in damage, which is covered by insurance. 

The Associated Press contributed to this report.

Credits

Tommy Wiita

Copyright 2018 - KSTP-TV, LLC A Hubbard Broadcasting Company

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