A metal tube ruptured within a reactor charge furnace during a unit start-up, releasing hot renewable diesel and hydrogen and resulting in a fire that seriously injured an employee at the Marathon Martinez Renewables facility in Martinez, California. The employee suffered third-degree burns to most of his face and body, the U.S. Chemical Safety and Hazard Investigation Board (CSB) announced in a February 21 update on its investigation.

The facility’s furnace preheats renewable feedstock, recycled renewable diesel, and hydrogen before subsequent processing.

The CSB’s update on its investigation into the November 19, 2023, fire at the Martinez facility details several key events in the incident timeline. These include:

• Activities occurring on the night shift of November 18 when Marathon was in the process of starting up the hydrodeoxygenation (HDO) unit.
• Within the hour leading up to the incident, Marathon operations staff were attending to furnace temperature control issues and high-temperature alarms inside the furnace.
• To reduce temperatures within the furnace, Marathon operations staff increased the flow of material through the furnace and directed a field operator to turn off two of the furnace burners.
• Around 12:21 a.m., just after the field operator had completed his actions at the furnace, a tube ruptured within the furnace, resulting in the fire that severely burned the field operator.

The CSB will continue to gather facts and analyze several key areas, including metallurgical testing and failure mode analysis. The agency also will conduct internal furnace component inspections and thoroughly review relevant facility, corporate, and industry standards.

 “The CSB is continuing to investigate this terrible incident to determine its cause, but we are issuing this update now to keep the public informed of the status of our investigation,” CSB Chairperson Steve Owens said in a board statement.

“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. These situations can present a unique set of safety hazards that must be carefully managed and controlled.”

Lead investigator Melike Yersiz said, “Our team still has a lot of investigative work to do. Ultimately, our goal is to identify probable causes of this incident and develop safety recommendations to prevent a similar event from occurring.”

The CSB investigates industrial accidents, explosions, and fires. Board members are appointed by the president subject to Senate confirmation.

The board has no enforcement authority and doesn’t issue citations or impose fines but makes safety recommendations to companies, industry and standards-setting organizations, labor groups, and regulatory agencies like the Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA). The CSB currently has 11 open recommendations for OSHA.

Last year, the CSB cleared much of its backlog of investigations, releasing final reports on incidents that included fatal dust explosions and fires at a Cambria, Wisconsin, dry corn milling facility; a fatal hydrogen chloride (HCl) release at a facility in Charleston, Tennessee; and tank farm fire at a bulk liquid storage terminal in Deer Park, Texas.