CSB: Tube Rupture Resulted in Release, Fire at Renewable Fuels Facility

A fire that seriously injured one worker at a renewable fuels facility in California in 2023 occurred when a metal tube ruptured, releasing hot renewable diesel and hydrogen, the U.S. Chemical Safety and Hazard Investigation Board has found. CSB describes renewable diesel as “a biomass-based diesel made from plant oils and animal fats.” An investigation update published last week by the agency provides details about the events leading up to the incident, which took place at the Marathon-operated Martinez Renewables facility in Martinez, California. The incident happened during the startup of the hydrodeoxygenation unit, and the tube that ruptured was part of a reactor charge furnace, which is used to preheat renewable feedstock, recycled renewable diesel, and hydrogen before processing.

Investigators learned that, in the hour leading up to the fire, facility staff were attending to temperature control issues with the furnace, including high-temperature alarms. According to CSB’s report, Marathon operations staff attempted to reduce temperatures within the furnace by increasing the flow of material through it and directing a field operator to turn off two of the four furnace burners. The tube ruptured shortly after this task was completed, and the subsequent release and fire caused third-degree burns to most of the operator’s face and body.

In a news release, CSB Chairperson Steve Owens noted the similarities between this incident and others.

“Like here, many of the incidents that have been investigated by the CSB have occurred during start-ups when conditions at a facility can change quickly,” Owens said. “These situations can present a unique set of safety hazards that must be carefully managed and controlled.”

CSB’s investigation of the Martinez fire is ongoing. Investigators plan to focus on additional inspection of the furnace’s internal components as well as identification and control of potentially hazardous scenarios.

Learn more in CSB’s investigation update (PDF).