CSB releases final report on fatal bp-Husky Toledo refinery explosion

Artem Blinov - Shutterstock

THE US Chemical Safety Board (CSB) has issued its final report identifying the “critical” safety issues leading to an explosion that caused the death of two brothers at a former bp-owned refinery in Oregon, Ohio.

More than 10,400 kg of naphtha was released at the US refinery in September 2022, which the CSB says caused around US$597m in property damage.

A mishandling of the refinery’s fuel system and an overflow of liquids contributed to the naphtha spill.

Steve Owens, the CSB chairperson, said: “Nearly everything that could go wrong did go wrong during this incident.

“The tragic loss of life resulting from this fire underscores the importance of putting in place the tools that employees need to perform tasks safely, such as stop work authority, and having adequate policies, procedures, and safeguards in place to effectively manage highly stressful abnormal situations, including alarm floods.”

The refinery, which processes around 160,000 bbl/d of crude oil, including gasoline, diesel, and jet fuel, was owned by bp and Husky Energy.

The refinery was acquired from bp by the Ohio Refining Company, a subsidiary of Cenovus Energy, in 2023. 

What happened

The CSB identified the cause of the explosion as the two brothers, an outside operator and trainee operator at the refinery, opening valves and removing a flange on the fuel gas mix drum, used to prevent operational problems in fuel-using systems. This released flammable liquid naphtha directly to the ground.

The naphtha created a vapour cloud that ignited when it found an ignition source, causing the death of the two operators.

The CSB concluded that “a series of cascading events” led up to and contributed to the incident.

On the day before the explosion, water began to accumulate in the refinery’s Crude 1 overhead accumulator drum, causing an overflow of liquid into other processing machinery.

Due to the overflow, naphtha had to be moved from the main crude accumulator drum to other storage facilities.

During one of these transitions, naphtha leaked into the fuel gas mix drum. It was then that the operators began to release the liquid from the drum.

Along with the mismanagement of the overflow and the inefficiencies of the refinery’s safety precautions, CSB said that the alarm flood of 3,712 alarms overwhelmed board operators and subsequently led to a delay in managing the naphtha spill. bp were also found to be aware of the risk that condensed liquids overflowing into a fuel gas mix drum could cause complications resulting in an explosion.

Learning from incidents

The CSB has issued seven safety recommendations to the Ohio Refining Company, and to the American Petroleum Institute (API), and the International Society of Automation (ISA), which include developing new safety standards and policies for fuel processing.

For the new owner, the CSB has called for the company to revise its safeguards in process hazard analyses for high-level overflow scenarios. It has also recommended that workers are given training and authority to stop work when they perceive a situation as being unsafe.

The board has called for the API to revise its technical publications on process hazards associated with fuel gas mix drums, and for ISA to revise its guidance on alarm systems.