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CSB issues investigation update into fire at Marathon Renewables facility

23 February 2024

The US Chemical Safety and Hazard Investigation Board (CSB) has released an update on the agency’s investigation into the November 2023 fire at the Martinez Renewables facility in Martinez, California which seriously injured a worker. The CSB’s investigation has found that a metal tube ruptured within a reactor charge furnace during a unit startup.

Image: CSB
Image: CSB

The furnace pre-heats renewable feedstock, recycled renewable diesel, and hydrogen before subsequent processing. The ruptured tube released hot renewable diesel and hydrogen, resulting in a fire on 19 November 2023that seriously injured one Marathon employee who suffered third-degree burns to most of his face and body.

CSB Chairperson Steve Owens said: “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. 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.”

The CSB’s update involves several key events in the incident timeline. These include activities occurring on the night shift of 18 November 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 00:21 local time, just after the field operator had completed this action at the furnace, a tube ruptured within the furnace, resulting in the fire that severely burned the field operator.

Investigator-in-Charge 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.”

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

Read the CSB’s investigation updated here: https://www.csb.gov/assets/1/6/Marathon_Martinez_Inv_Update_Final_Final.pdf


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