The Case of the Fatal Refinery Fumes

Refinery Explosion and FireThe Problem:

An explosion occurred in an oil refinery while mechanical contractors were arc welding and installing small air-line pipes inside a pipe rack.  The explosion caused the death of three workers.  Forensic investigations initially considered an explosive atmosphere at the welding ground attachment as the source of ignition.  Welding safety management procedures were disregarded at the time of the explosion.  Welding in a petroleum refinery environment is a hazardous and highly restrictive operation.

Schematic of Welding in Pipe Rack and TanksMy Assessment:

Combustible vapors escaped into the refinery atmosphere through the vent line of Tank 1, near the welders.  The welding sparks and molten spatter on a 1” line, fell through these vapors causing the fumes to be ignited and the fire to propagate into the tank through the vent line and the tank exploded.

The Consequences: 

After the explosion, the Hot Work permit was forged and there were attempts to cover up the safety violation that occurred.  The permit was incomplete and unsigned by the welder.  Refinery personnel were not familiar with their own process and did not know flammable vapors were emanating from the tank.  

The Lessons Learned: 

Ample precautions must always be taken to prevent explosions, fire and property damage in hazardous work areas.  Never assume owners, engineers, and operators understand their own plant processes and operations.  Hot Work permit procedures must always be followed when welding in a refinery and the workplace atmosphere must be continuously monitored with a gas detector.

Evidence was disturbed prior to forensic assessments.  The Forensic Engineers were not allowed to witness dismantling of the mutilated tanks.  The welding ground circuit did not create errant arcs like static electricity.  Welding arcs and sparks from the welder ignited unexpected, volatile fumes in the workplace.

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Welding Failures I Have Known, Interesting cautionary tales from Metals & Welding  expert, Dr Jesse A Grantham, PE