An explosion followed by fire occurred at 3.20 am in a SEVESO plant’s lubricant additive manufacturing facility located in a harbour-based industrial zone. The unit, experiencing an operational shutdown for the last 3 days, appeared to be empty of all additives at the time of the accident. The establishment’s internal contingency plan was initiated. The company’s firefighters brought the fire under control before the external rescue services arrived. The situation was brought under control at 4.30 am and the internal contingency plan was called off at 8.15 am.
The explosion was due to a lock-out defect associated with the simultaneous presence of a combustible, an oxidant and a heat source: 200 kg of enriched mineral oil-based product remained, left over from the last fabrication run in the esterification reactor’s outflow cone. The possible decomposition of the oil, or even the synthesis of peroxides above 150 °C for several hours was considered: tests were conducted by a third party company. Oxygen was present in the reactor following a ventilation operation by the personnel in order to service the reactor of the parallel line. The heating system used by the reactors of both lines were started to test the boiler, without by-passing the reactor that had been shut-down. The empty tank was thus heated for more than 24 hours: the internal temperature reached 150 °C for several hours and 200 °C for 2 hours. The reactor parameters (T, P and level) were indicated in the control room, but during the accident, as the unit was shutdown, no one was monitoring the instruments.
Property damage was limited to the production unit (6.5 M euros); the associated storage facilities were not damaged. However, the activities of the site’s other units were shut down and would resume subject to prefectoral authorisation (operating losses estimated at 4.5 M euros). No atmospheric or water pollution was detected; the quality of the water in a nearby canal was checked every 30 minutes. The barriers of a nearby bridge were lowered accidentally 4 hours after the accident and remained down for 30 minutes. An official statement was issued to inform the administrations, communities and local media outlets, and the industries in the zone.
Corrective measures included the implementation of a heating control system with alarm at 210 °C and automatic shut-down when agitation is stopped, an increase in the frequency of parameter measurements, review of the heating procedures, and monitoring of parameters in the control room even during shut-downs