The U.S. Chemical Safety Board says the Feb. 18, 2015, explosion at the ExxonMobil refinery in Torrance, CA, was caused by “multiple process safety management deficiencies.” The CSB also contends the situation easily could’ve been much worse.
Two workers were injured when an explosion occurred in the refinery’s electrostatic precipitator (ESP), a piece of equipment used to control air pollution.
The investigation is ongoing, but the CSB has provided a progress report as the first anniversary of the incident approaches. The CSB says ExxonMobil determined it needed to deviate from several existing procedures to bring an idled piece of equipment back on line. This required a variance – a written temporary deviation from normal operating procedures. The CSB says ExxonMobil used a variance created in 2012, despite the fact that several things at the plant had changed in the intervening three years.
The events that led to the explosion unfolded over several days, according to the CSB:
- On Feb. 12, 2015, problems with equipment called an expander caused the refinery’s fluid catalytic cracking unit to be idled
- Because the unit was shut down, steam was forced into a reactor to prevent hydrocarbons from flowing back from the main distillation column
- On the morning of the explosion (Feb. 18), the steam was escaping, preventing maintenance work
- An outside supervisor then reduced the amount of steam being forced into the reactor so that work could continue
- As the steam pressure dropped, the hydrocarbons flowed back into the reactor and into the ESP
- The hydrocarbons met an ignition source in the ESP and exploded.
CSB investigators also found large pieces of debris from the explosion were thrown into other areas of the refinery. One of those pieces of debris narrowly missed a tank containing tens of thousands of pounds of modified hydrofluoric acid (HF).
If the tank ruptured, the release of HF to the neighboring residential community could have been catastrophic, according to the CSB.
HF can cause severe damage to the respiratory system, skin and bones and is potentially fatal. About 333,000 residents live within a three-mile radius of the ExxonMobil plant.
ExxonMobil has disputed the threat to the community.
The CSB also says the oil company hasn’t been completely cooperative with its investigation.