This case study investigates the factors resulting in an electrostatic ignition incident involving toluene, a prolific charge generator, filling a metal bucket via gravity fed 0.75” metal piping.

In this scenario, an operator opened a valve to draw toluene into a metal bucket with toluene from an overhead tank by gravity flow at approximately 5 gallons per minute. The operator hung a metal bucket with a wire bail and plastic handle over a globe valve. The plastic handle on the bail isolated the metal bucket from ground. On opening the valve, the operator backed away from the bucket allowing the toluene to flow as he had previously done several times. Within a few moments the toluene had ignited causing the operator to immediately leave the scene returning with a small fire extinguisher, which proved inadequate to put the fire out. The operator then left the scene returning with a larger fire extinguisher, however by the time he had returned the fire was out of control and he was unable to close the valve to prevent the flow of toluene to the bucket which was already over flowing.

The investigation into the incident outlined that the operator had opened the valve and backed away from the metal bucket. The operator stated “I was just standing there looking at it when it caught fire”. As a result, discharge from the operator could be ruled out as a cause of the incident and the scenario of a streaming current was considered.

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