Electrostatic Ignitions

Toluene – An Underestimated Fire Hazard

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Shortly before the plastic drum was full, ignition of the toluene vapours occurred which led to a fire. As in the course of time the plastic drum burnt down, the entire toluene was set free causing a conflagration. A devastating widespread fire was the result but the worker could get himself to safety in time.

(Picture: Elstatik)

Gallery

Cause of Fire

The electric charge carried with the toluene accumulated in the plastic drum as it could not be drained off to earth, a possibility that had existed with the earthed metal drum. When the thus highly charged liquid level approached the filling nozzle a brush discharge occurred and its energy was just sufficient to ignite a stoichiometric vapour/air-mixture. As the accident took place at room temperature, optimal ignition conditions were given.

Recommendation:In explosion endangered areas no plastic packaging materials should be present.

2. Flowing of Toluene Through an Isolating Hose

Contaminated toluene had to be filled into an earthed metal container at a printing ink manufacturer. In general, this took place in aspects of electrostatic safety measures as explained in case history 1.

During the action the worker noticed a leaking point at the hose coupling, liquid dripped out. For such a case a supplementary hose was planned but it could not be found. However, in a similar plant – but for water – a like hose was found, but made of isolating PVC. Quickly it was replaced against the leaking conductive hose and now the action could continue.

But when the filling nozzle approached the rim of the metal container weak sparks were to be noticed and immediately a tongue of flame came up. Luckily the container withstood the flames and the fire soon could be suffocated by extinguishing foam.

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