In a fine chemical plant, a toluene leak in a solvent reception tank (300 litres)connecting a dryer (3 000 litres) caught fire while the facility was being cleaned with toluene. The solvent (whose temperature was close to room temperature) present in the reception tank and pipes (including the liquid seal) leaked from the cover joint and caught fire. The ensuing flash opened the doors of the premises. The internal contingency plan was triggered. A dozen employees who sustained light burns were evacuated. The person who suffered the most injuries (3 days stoppage of work) was closest to the reception tank at the time of the incident. The accident took place during the first production cycle. The drain pump of a tank failed to start following an electrical defect in a terminal board (poorly secured lug). This led to the excessive filling of the tank that gave in to the hydrostatic pressure (cover not airtight). The unit was newly installed and had several faults in the design: reception tank without retention unit and undersized compared to the centrifuge volume which meant that the pump had to be started several times, non-redundant level alarm, plastic making up the tanks and pipes not adapted to the dielectric properties of toluene, tank made of fragile plastic material, poorly secured cover, etc. During a visit, the inspection authorities of classified facilities observed anomalies in the pipe of the installation: Time / operation log book pre-filled by operator until 10.00 am where as the accident took place at 8.00 am, only seven bolts to secure the cover of the reception tank instead of eight, the eighth bolt was replaced with a clamp; only four bolts were mentioned in the original plans. Various measures were taken: some portions of the pipes were changed, dryer’s drain cones maintained under pressure and instrumented, explosive atmosphere detection improved of, overflowing during automatic delivery of solvents prevented via the tank storage area, safety mobile valve on the reactor power supply bypassed. The accident is illustrative of organisational errors and design faults.

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