An explosion occurred around 1:45 pm inside a 28-tonne electric smelting furnace at a steel mill. The internal emergency plan was activated, energy supplies cut and 60 employees evacuated; the public safety and rescue office was notified. No one was hurt, but 8 employees endured emotional shock and had to be taken to hospital; 3 of them would be placed on leave from work for a few days. The emergency plan was lifted at 3:07 pm. Responders left the site around 4:30. The explosion sprayed bricks from the furnace vault over a 10- to 15-m radius; the mechanical arm holding the electrodes was damaged, and the roof above the furnace sustained slight deterioration (shifting of asbestos cement plates), yet without observing any liquid steel spatter. The appraisals conducted afterwards indicated no structural vulnerability. Most dust emitted during the explosion could be treated in the dust collector.
Production was shut down for 1 week to carry out the investigation (circuit sealing tests) and restore the furnace. No water circuit defect was found during the expert appraisal. Water/metal contact upon melting, due to the presence of residual humidity in the steel ingredients, was the cause suspected by the operator. During the explosion, a big-bag containing dust from the site (the dust was recycled internally), which had spent several weeks exposed to air, was placed in the furnace; the bag might have held enough water to trigger the deflagration.
Subsequent to the accident, the operator introduced an action plan that anticipated: revising and formalising a number of operating protocols; issuing a reminder of the guidelines for personnel (prohibition to walk in front of the furnace during smelting, risks related to hollow objects, presence of water in the reinforcements); strengthening preventive controls carried out on the furnace vault; updating the internal emergency plan; seeking alternative solutions to cooling the water of certain furnace mechanisms; and conducting a study in order to improve the water leak detection function.
