US chemical safety agency concludes that a series of errors led to the fatal accident at the BP Husky refinery

An accidental emergency release of more than 10,000 kg of liquid naphtha resulted in the deaths of two workers at a BP Husky refinery in September 2022, according to a final report by the US Chemical Safety and Hazard Investigation Board (CSB). The investigation found that the naphtha created a vapor cloud that ignited at the Oregon, Ohio refinery, killing the employees, who were brothers.

The report, released on June 24, describes a series of overlapping events that contributed to the release and fire. It reports an “alarm surge” in which more than 3,700 alarms were triggered in the 12 hours before the incident, overwhelming BP operators and leading to delays and errors in responding to critical alarms. The CSB also found that the refinery failed to implement a shutdown or issue a stop-work order to prevent the accident.

On the day of the incident, a process malfunction in the plant’s naphtha hydrotreater caused several refinery units to shut down. Operational decisions caused liquid naphtha to flow into and fill a pressure vessel that normally only contains vaporous gases. BP workers were instructed to quickly empty the vessel, so they dumped the contents on the ground. The naphtha vaporized and caught fire. The CSB report concluded that employees may have believed the liquid was an amine-water solution and not naphtha.

The report made several recommendations, including: better implementation of safety improvements. BP’s process hazard analyses correctly identified the vessel’s potential risks, including the management of spill events. But the safety precautions implemented by refinery managers, such as safety instruments and emergency pressure relief valves, proved inadequate.

In addition, the CSB found that BP had not learned enough lessons from previous similar incidents. An incident at the refinery in 2019, the report said, also involved the overfilled pressure vessel.