At 7:40 am., an explosion occurred during welding works in a steelwork factory. Track-bound cylinders are used for the transport of the pig iron from the blast furnace to the steelworks. These are long steel cylinder containers that are bricked up on the inside with several layers of ceramic material and cast compound. Due to wear and tear the cylinders are relined with masonry work twice a year, the last operation having been done on the 07/05/2004. After the cast compound hardened over the weekend, the casting mould was to be lifted out of the cylinder using an overhead travelling crane. During the lift, one of the lifting eyes came lose from the wooden casting mould and the transverse bolt in the mould dropped down and consequently had to be repaired. The explosion occurred when the welding electrode came into contact with the bolt, as an explosive atmosphere (ATEX) of hydrogen had been created during the hardening process of the cast compound. One technician was killed, another sustained severe facial injuries and 2 suffered minor injuries. Material damages were limited, and no consequence was observed outside the plant.

The accident happened because of a lack of information from the supplier of the new compound to the user. Even if the suppler is formally not obliged to do so in its Safety Data Sheet, the supplier should have informed the company that hydrogen gas would be formed during the hardening process of the cast compound and that the cast compound should not be used in enclosed spaces due to the formation of hydrogen gas. The company would maybe have conducted a risk analysis and carried out a hot work permit before starting the welding works.

The operator performed a risk assessment on the casting cycle and took the following measures to prevent recurrence :

• The closed casting mould was replaced with an open one.
• The torpedo car will be ventilated during casting cycle.
• One person has been appointed as full time safety controller.
• The company “management of change” procedures were improved.