June 27, 2024

CSB: “Nearly Everything That Could Go Wrong Did Go Wrong” Before Fatal Refinery Fire

On June 24, the U.S. Chemical Safety and Hazard Investigation Board published its final report (PDF) on the naphtha release and fire that lead to the deaths of two BP employees at the BP-Husky Toledo Refinery in Oregon, Ohio, on Sept. 20, 2022. According to CSB’s press release, board operators responding to a process upset in the naphtha hydrotreater unit on the day of the incident made decisions that caused liquid naphtha to overfill a pressurized vessel, which normally contained only vapor. When board operators drained the vessel, its contents created a vapor cloud that ignited, causing a flash fire. This “cascading” sequence of events led CSB Chairperson Steve Owens to state, “Nearly everything that could go wrong did go wrong during this incident.”

The report details how the refinery’s procedures contributed to several safety issues. For example, although the refinery had conducted process hazard analyses that identified risks such as overflow events, it did not have safeguards in place to prevent liquid naphtha overflowing from a tower into a vapor bypass line leading to the pressurized vessel. The refinery relied on operators to respond to process upsets but had not considered hazards that could arise if the vessel filled with liquid. Operators were not provided with procedures for addressing liquid in the drum.

The refinery also did not effectively manage “abnormal situations,” which CSB defines as process disturbances that basic process control systems cannot cope with. Abnormal situations are stressful to operators and can escalate into serious incidents. The refinery had experienced abnormal situations in several units, starting with water accumulating in the naphtha processes on the night of Sept. 19, almost 24 hours before the fire.

These abnormal situations included an “alarm flood.” According to the report, people can respond to no more than 10 alarms in 10 minutes. Board operators at the refinery experienced more than 3,700 alarms in the 12 hours before the incident, and as many as 281 alarms in one 10-minute period. “Such a situation is virtually impossible to manage for extended periods without missing critical alarms or errors occurring,” the report states.

CSB found that the refinery had not learned from an incident that led to naphtha filling the pressure vessel in 2019 or from the fatal explosions at another BP refinery in Texas City, Texas, in 2005. If BP had effectively recognized and acted on the warning signs, the report states, “the company could have provided more effective safeguards to prevent the overflow of multiple vessels during a refinery upset such as the September 20, 2022, incident.”

The report does not include recommendations made to BP, as the company no longer operates the refinery in question. However, CSB issued a range of recommendations to the refinery’s current operator, Ohio Refining Company LLC, which include clearly providing employees with the authority to stop work they perceive to be unsafe and training them on how to exercise this authority in abnormal situations. CSB also recommended that the American Petroleum Institute and the International Society of Automation develop guidance on preventing pressure vessel overflow and managing alarm systems, respectively.

The fire on Sept. 20, 2022, was the largest fatal incident at a BP-operated petroleum refinery in the U.S. since the Texas City explosions and fires in 2005, which resulted in the deaths of 15 workers and injuries to 180 other people.

More information can be found in CSB’s press release.