Process safety management deficiencies led to an explosion at ExxonMobil’s Torrance, California, refinery that injured two workers and spewed ash and debris into the nearby community, federal investigators said today. The U.S. Chemical Safety Board said the circumstances that led to the February 2015 incident were similar to those observed in its investigation of the 2012 fire at Chevron’s Richmond, California, refinery.
The explosion was triggered by a buildup of hydrocarbons inside the refinery’s electrostatic precipitator (ESP). The conditions that caused the blast began six days prior, when the refinery’s FCCU was idled due to problems with an expander. The FCCU shutdown resulted in a release of steam into a reactor that later leaked from an open flange on the expander. A supervisor later reduced the amount of steam so that work could continue on the expander. Unbeknownst to the workers, hydrocarbons were leaking into the main distillation column. When steam pressure dropped, the hydrocarbons leaked back into the reactor, ultimately making their way to an ignition source in the ESP.
CSB said ExxonMobil failed to conduct a management of change review before implementing a variance that was needed to bring the FCCU back on line. The board said the variance was outdated given that conditions within the FCCU had changed in the three years since the variance was created.
CSB also found ExxonMobil performed inadequate process hazard analyses that would have identified more effective safeguards against the flow of hydrocarbons.
The board said the explosion came dangerously close to triggering a release of hydrofluoric (HF) acid. A large piece of debris hit scaffolding in the refinery’s alkylation unit, narrowly missing a tank that contained tens of thousands of pounds of modified HF.
The refinery has been running at reduced capacity since the incident, and its lower output has contributed to higher-than-average gasoline prices in California. ExxonMobil is in the process of selling the refinery to PBF Energy.
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