On a Sunday at 4:00 a.m., a fire broke out on the cooling system of an induction-coil melting furnace at a foundry. The furnace’s coils were cooled by a coolant containing an aluminium-lithium alloy. The furnace, which was being loaded at the time, contained 11 t of molten metal. The melt technician saw the furnace’s alarms go off and then heard a small explosion. He informed his supervisors and the foundry was evacuated. The foundry’s firefighters put the fire out with powder extinguishers. The propylene glycol (propane-1,2-diol) used as the coolant flowed into the furnace’s bund. The operator let the metal solidify in the furnace to avoid creating a hot spot by pouring the molten metal. The glycol in the bunding was pumped out.

The fire was caused by the molten metal boring through the furnace. Solidified metal may have become trapped between the primary concrete and the refractory when the refractory was last replaced, weakening the furnace. An optical coil protection system detection (OCP) was grouted into the concrete of the furnace. However, it did not activate until the accident had already started. It turns out that two of the six optical fibres in the system did not work. The flow of glycol could have been shut off from the furnace control room as soon as the problems were detected. However, the technicians had neither any instructions in this regard nor a system allowing them to see what was happening.

After the accident, the operator decided to equip its furnaces with the most robust model of OCP system. It also had a camera installed to allow the melt technician to see the underside of the furnace and wrote instructions defining the circumstances of this interruption.