At around 11:05 a.m., a furnace at a foundry exploded during a steel melting operation, flinging metal into the shop and filling it with a thick cloud of dust. The three employees present evacuated the shop. Two suffered burns from hot metal projected by the blast. After the dust settled, employees put out the flames with fire extinguishers. Firefighters evacuated the injured and secured the area. Six people were furloughed for four days. The plant suffered €56,000 in material damage and €450,000 in operating losses.

In 2017, the old furnaces had been replaced by a new generation of induction furnaces fitted with reinforced safety devices and magnetic screens. The melting platform was rebuilt to offer better ergonomics and was fitted with suitable handling equipment. Ten days before the accident, the furnace had been relined with an aluminous refractory containing spinel. The refractory had been fired (sintering) one week before the accident. This type of refractory is designed for 80 melting operations. Twenty-three had been carried out that week.

At 10:50 a.m., the furnace registered a ‘furnace flow meter, switch lock’ fault. The operator cancelled the fault and then reset the circuit breaker without informing the maintenance department. The furnace registered the fault again. The first explosion occurred when the circuit breaker was again reset and melting was resumed by another technician. Two other explosions followed. The analysis of the event found that crust had formed on the load above the molten metal. This crust prevented the raw materials subsequently loaded from descending into the molten metal inside the crucible. Overloading may have contributed to the formation of this crust. The crust caused the metal to overheat and prematurely weaken the refractory. The metal then pierced through the refractory and reached the cooling circuit. On contact with the molten metal, the water vaporised, causing different flow rate measurements in the circuit. With the heat off and attempts made to reset the circuit breaker, the water condensed back to the liquid phase. Even though the fault had been cancelled, molten metal remained in the furnace and eventually pierced the cooling water system. Contact between the water and the molten metal caused the explosion.

The operator enhanced the training of his employees and added a knowledge assessment. New instructions are displayed at the workstation: in the event of a fault, the platform must be immediately evacuated and the maintenance department alerted. In addition to being displayed, faults are accompanied by a buzzer.