U.S. Chemical Safety Board Report- 2018 Husky Superior Refinery Explosion and Asphalt Fire In Wisconsin

CSB Releases Final Report into 2018 Husky Superior Refinery Explosion and Asphalt Fire in Wisconsin

Washington D.C. December 29, 2022 – Today the U.S. Chemical Safety and Hazard Investigation Board (CSB) released its final report on the 2018 refinery explosion and fire at the Husky Superior Refinery in Superior, Wisconsin. The accident injured 36 workers, caused roughly $550 million in damage to the facility and released 39,000 pounds of flammable hydrocarbon vapor into the air. Over 2,500 residents of the City of Superior were evacuated from their homes, and the City of Duluth, Minnesota, issued a shelter in place order. 

At the time of the incident, the Superior Refinery was owned by Husky Energy, which had purchased the refinery less than six months earlier in November 2017 from Calumet Specialty Products, LP. In 2021, Husky Energy merged with Cenovus Energy.

The CSB’s final report details how the incident occurred while the refinery was shutting down its fluid catalytic cracking (FCC) unit to perform planned maintenance (called a “turnaround”), a common refining process. Two vessels in the FCC unit exploded, propelling metal fragments up to 1,200 feet away that punctured a nearby asphalt storage tank at the refinery, which ultimately spilled approximately 17,000 barrels of hot asphalt that ignited and caused multiple fires. .

The CSB’s final report notes that in addition to smoke from the fires at the refinery, the City of Superior evacuation was based on the potential risk of a release of highly toxic hydrofluoric acid (HF), which was stored and used at the refinery. Although no HF release occurred, the risk of an HF release was present because the HF storage tank was closer to the point of the explosion than the asphalt storage tank and could have been punctured by the debris from the explosion.

CSB Chairperson Steve Owens said, “Refineries with FCC units, including especially those with hydrofluoric acid alkylation units, should review our report thoroughly and ensure  that they have the necessary safeguards in place to  prevent a similar disaster from occurring at their facilities during shutdowns and startups.  This accident could have been avoided.”

The CSB’s report identifies 6 key safety issues, which include:

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