In an aluminium transformation plant, at around 6 am a technician noticed flames coming out of a double-jacket mixer containing 1 t of paste made from 20% white-spirit and 55% fatty acid and aluminium powder. He activated the fire alarm box which triggered the siren. After shutting down all of the installations, the staff gathered together. The 1st emergency response team estimated the situation wearing SCBA, as thick smoke had spread into the building. Two first aiders fought the flames using powder extinguishers, another pair placed fire blankets and sand in the hopper. The external emergency services brought the fire under control by covering the paste with extinguishing powder and sand and cooling the mixer (device T° in the upper section at 110 °C) using the double-jacket water circulation system. Monitoring of the temperature of the water and walls was set up. The fire spread to an electrical cableway overhanging the installation and firefighters wearing SCBA extinguished it using powder extinguishers after dismantling the siding. The emergency response system was lifted at the beginning of the afternoon after cooling of the paste (40 to 50 °C) recorded with a thermal imaging camera. The firefighters carried out a further check the next morning (T° = 20 °C) which eliminated any risk of re-ignition.
The mixer and workshop operation was interrupted for over 3 months. The electrical system was significantly damaged. The roof was destroyed over 10 m²; as this was an old asbestos-cement roof, a removal plan was mandatory with decontamination of the entire structure and all of the equipment. The media went to the scene.
The aluminium paste would be self-igniting in the mixer due to its extreme fineness, a very low level of lubricant (0.02% instead of 0.5 at 1%), inadequate air circulation in the shredder, a higher than normal non-volatile proportion of the powder cake and the unsuitable position of the mixer’s hatches. The spread of fire to the electrical installations could be explained by their age and the cables’ proximity to the mixer.
Following the accident, the operator planned the implementation of preventive measures for shredding, temperature control, formulation (oleic acid content increased and non-volatile content reduced), filtering, mixing (procedure for closing and earthing the hatches, packing the cakes in drums, product temperature readings, safety guideline in the event of a rise in temperature, studying the installation of a probe in the mixer with data recording), electricity (change all of the cabling), training, accident enquiry, organisation and feedback.