Tesoro Denies Plant Blast in Washington Due to Poor Maintenance

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The U.S. Chemical Safety Board said Tesoro Corp. had not adequately maintained a heat exchanger at its Anacortes, Washington, refinery, that exploded on April 2, 2010, causing the death of seven workers.

Microscopic cracks had formed in the walls of the exchanger in a common phenomenon seen in metal where hydrogen is present under high temperature called high-temperature hydrogen attack, said Board Chairman Rafael Moure-Eraso in a video statement issued Friday on the board’s preliminary findings.

“This led to a violent rupture of the exchanger followed by an intense fire as large volumes of naphtha and hydrogen were released,” Moure-Eraso said in the statement.

A Tesoro spokesman said the company did not agree with the assessment about maintenance at the refinery from the board, an independent federal agency charged with determining causes of serious chemical accidents in the United States. The board does not regulate the industry or issue fines or citations.

Tesoro spokesman Mike Marcy said the heat exchanger “was maintained and inspected in accordance with regulations and industry standards.”

In October, the Washington state Department of Labor & Industries fined Tesoro $2.38 million for safety violations in the blast including a failure to maintain and test the heat exchanger at the refinery.

“Our position has been that had Tesoro conducted the appropriate and required testing, they would have found the cracking that led to the rupture,” said Hector Castro, spokesman for Washington Department of Labor & Industries.

Tesoro is appealing the fine before the Washington state Board of Industrial Insurance Appeals.

The United Steelworkers union, which represents hourly workers at the refinery, said the explosion was preventable.

“The industry has known that to prevent such an incident from happening any type of equipment in contact with high temperature hydrogen has to be maintained and inspected more so than in other processes,” USW spokeswoman Lynne Baker said in a statement. “This was a preventable accident.”

The Washington state investigation found the heat exchanger, which warmed and cooled naphtha going to and from a hydrotreater, was last inspected in 1998. Tesoro put off a scheduled inspection of the unit in 2008.

Tesoro also faces a criminal probe of the explosion by the U.S. Environmental Protection Agency and lawsuits by relatives of the seven workers who died due to explosion.