Eroding Valve Potentially Caused Husky Refinery Explosion

Investigators say it's similar to one that occurred in Torrance, California at Exxon Mobile's refinery.

SUPERIOR, Wis.- The potential cause behind the Husky Energy refinery explosion in Superior is believed to be found during an ongoing investigation by the U.S. Chemical Safety Board.

Investigators tell us it appears the explosion could have happened due to an eroded piece of equipment.  Click here for a play-by-play animated video of before, during and after the explosion.

“You get erosion of the valve so portions over time get worn away by this catalyst interaction with the surface,” CSB lead investigator Mark Wingard said.

That valve is in an area known as the Fluid Catalytic Cracking Unit. It plays an important role in keeping hydrocarbons and oxygen separate.

But investigators believe it deteriorated over time.

Debris from the explosion flew above 200 feet hitting a storage tank, spilling more than 15,000 gallons of hot asphalt.

Through an ongoing investigation, the CSB believes the blast happened during a routine shut down for periodic maintenance and inspection. The CSB has found that startups and shutdowns are times of enhanced risk because there are nonroutine operations occurring.

Thirty-six people sought medical attention, 11 were refinery and contract workers who sustained OSHA recordable injuries.

Husky refinery released the following statement in part:

“The safety of our employees and the community remains our top priority and we will continue to work collaboratively with the CSB and other investigating agencies. The lessons learned will assist with our decisions as we begin the process of rebuilding the superior refinery.”

We asked CSB investigators the last time the slide valve was inspected, but officials said they did not know the answer Thursday. This is just the beginning of the investigation. Husky Energy in Superior is still closed and expected to fully open for normal operations in up to two years.