HOUSTON (ICIS)--The US Chemical Safety Board tracked down the cause of a 2016 fire at an ExxonMobil refinery in Baton Rouge, Louisiana, it said on Monday.
The findings were part of a safety bulletin that the board released to help prevent similar accidents.
The fire happened while ExxonMobil was conducting maintenance at the plant, the CSB said. Workers inadvertently removed bolts that held a piece of pressure-containing equipment to a plug valve, the CSB said. When the workers tried to open the plug valve, it fell apart.
Hydrocarbons then escaped, forming a cloud of vapour that quickly ignited, the board said.
The fire could have been prevented had all of the older valves had been replaced by those with safer designs, the CSB said. At the unit, 97% of the valves had already been replaced by safer ones.
The CSB also found a culture at the refinery that was accepting of workers performing maintenance on malfunctioning plug-valve gearboxes without written procedures or adequate training, according to a statement by Mark Wingard, CSB investigator.
ExxonMobil said: "Safety is a core value at ExxonMobil, and nothing is more important than the safety and health of our employees, our contractors and the people who live and work near our operations."
The company conducted its own investigation of the fire and has taken steps to address any problems, it said.
"We learn from all incidents and will use this information to continually improve," ExxonMobil said. "We will continue to evaluate human factors associated with equipment design to mitigate identified hazards and will evaluate and update procedures and training."
The Baton Rouge refinery has a capacity of 502,500 bbl/day.
The fire injured four workers, the CSB said.
The CSB is an independent federal agency that conducts investigations on chemical accidents. The agency notes that its board does not issue citations or fines, but does make safety recommendations to companies, industry organisations, labour groups and regulatory agencies.
The safety bulletin can be found here.