An explosion and subsequent fire occurred on the storage part of a modern refinery complex (capacity of 7.5 million tonnes per year) producing LPG, naphthas and petrols.

In the days prior to the accident, a defect (insufficient temperature and pressure settings) on the debutanizing column of the fluid catalytic cracking (FCC) unit prevented the extraction the light fractions of hydrocarbons which were consequently sent together with the petrol to the storage tank 2178 C. The gases accumulated in the tank, forming a pocket that spread outside the recipient until an ignition source set off a gas blast (UVCE) at 8:15 am. The explosion displaced the tank’s floating roof and started the combustion of the 2,400 m3 gasoline it contained. The fire then spread to the other gasoline tanks housed in the same area.

The external emergency plan was set-up : the internal emergency teams, backed by external fire fighting services (188 firemen – 36 vehicles, 11 ambulances, 4 helicopters…), used drenching systems (water sprays, monitors, etc.) and inerting systems (foam). The police stopped the traffic on nearby roads for 76 h; the population was informed and the environment was monitored.

In total, seven storage tankers (8,600 m3 of petrol) were affected, and it took over 48 hours to extinguish the fires. Nine plant workers were killed and 1 seriously injured, 9 fire-fighters were slightly injured and the storage area suffered serious material damage. The costs of material losses (tanks as well as broken windows and false roofs of several buildings) were evaluated at 50 M euros, the response and clean-up costs at 4 M euros.

The accident analysis revealed an incomplete risk analysis, inadequate working procedures in the FCC unit, high levels of gas stored in the tanker (which led to the displacement of the tanker’s floating roof) and a late detection which allowed the gases to accumulate.