(Reuters) — The U.S. Chemical Safety Board (CSB) has wrapped up a two-year investigation of a Feb. 18, 2015, explosion at a Torrance, Cal., refinery then owned by Exxon Mobil Corp. It found that weaknesses in Exxon Mobil’s process safety management program led to the explosion, which caused minor injuries to four workers and spiked West Coast gasoline prices.
The blast occurred when volatile hydrocarbons flowed backwards in an idled gasoline-producing fluidic catalytic cracking unit (FCCU) to the electrostatic precipitator, which releases sparks as it collects catalyst particles from escaping through the unit’s exhaust stack.
“These weaknesses led to operation of the FCC unit without pre-established safe operating limits and criteria for unit shutdown, reliance on safeguards that could not be verified, the degradation of a safety-critical safeguard, and the re-use of a previous procedure deviation without a sufficient hazard analysis that confirmed that the assumed process conditions were still valid,” the CSB said in its report.
The board also found debris from the precipitator nearly struck alkylation unit settler tanks containing toxic hydrofluoric acid, which can be deadly at 30 parts per million. The CSB has asked a federal court to enforce subpoenas against Exxon so the board can read information the company withheld about steps taken to prevent hydrofluoric acid releases or to mitigate them.
“We are confident that we understand the cause of the Feb. 18 incident and have worked cooperatively with the Chemical Safety Board and staff to fully understand their findings and recommendations to improve the safety of our operations. In terms of safety, Exxon Mobil meets or exceeds accepted industry practices and has stringent safety measures in place to mitigate risks associated with the modified hydrofluoric acid alkylation process,” Exxon Mobil said in a statement.
