During maintenance work performed inside a multi-product depot, a fire broke out around 10 am on a cylindrical tank 16 m high, 16 m in diameter and of 3,200 m³, dedicated to styrene storage. At the time, the tank was emptied and degassed, while manholes were kept open. Polymerised styrene residue was observed during a preliminary control, and the largest agglomerates were removed. The tank was subjected to maintenance and compliance works before re-strapping. An external company was performing grinding work on the roof of the tank when the styrene “stalactites” caught on fire from the sparks produced by these works. Plant management was notified by the external company about the outbreak of fire, before proceeding with the evacuation, collection and headcount of the external contractors’ staff. The operator decided to fill the cooling crowns fitted on the tank and its neighbouring tank, and then attempted to extinguish the fire with a hose. A smoke plume began to exit through the openings of the tank and prevented intervention in the immediate vicinity of the fire. After several unsuccessful attempts to extinguish the fire, the fire department arrived at 10:35 am equipped with self-breathing apparatuses and extinguished the fire from the tank bottom. Even though the other facilities were not threatened, the operator activated the IOP at 11 am as a precautionary measure. Hoisted onto the roof of the tank, fire-fighters cut the envelope to allow smoke to evacuate, passed hoses inside the tank and brought the situation under control. The fire was confined to the styrene residue, which remained beneath the drop panel of a gauge well after the tank had been emptied.

Property damage was limited to heating a cross-section of the tank wall. No operating losses were incurred. The Classified Facilities Inspectorate was informed of the incident late in the morning and noted that the effects from ignition of these residues along with the difficulties encountered in extinguishing them had been underestimated by the operator, who had controlled the tank prior to initiating the works. The operator had given the instruction to proceed with the removal of all debris, even minor quantities, before any work on the tank.

Inadequate cleaning of the tank before works start-up was the cause of this accident. The Inspectorate had requested the Prefect to issue a supplementary order requiring the emptying and a thorough cleaning of the tanks prior to any hot works.