A fatal explosion and fire at Hayes Lemmerz International's Huntington aluminium wheel plant was caused by the ignition of fine powdered aluminium in a dust collection system in which hazards were neither identified nor adequately addressed.
That's the conclusion of the final report into the incident by the US Chemical Safety and Hazard Investigation Board (CSB).
The explosion, which occurred around 8:30 pm on October 29, 2003, caused fatal burns to a mechanic working near an aluminium melt furnace, severely injured a second mechanic nearby, and caused lesser burns to a third worker. Four other workers suffered minor injuries.
CSB investigators determined that the dust that exploded originated in a scrap system at the facility. A high concentration of aluminium dust, when suspended in air, is highly combustible.
The CSB determined the dust was a by-product of the process in which aluminium chips and scraps - which are created as the wheel castings are machined - are dried prior to being sent to a furnace for re-melting. Dust from the scraps is conveyed into a dust collector outside the building.
The CSB determined that an explosion in the collector sent a pressure wave through the system ductwork and back into the building. A fireball then erupted inside the building, which lofted and ignited further aluminium dust that had accumulated on rafters and equipment.
The Board found the company did not address why the chip drying system was releasing excess dust, and did not identify or address the dangers of aluminium dust ignition, despite having a history of small dust fires inside the factory. The CSB also determined that Hayes Lemmerz did not ensure the dust collector system it ordered was designed in accordance with guidance in a prominent fire code published by the US National Fire Protection Association.
The Board issued formal recommendations to the company, urging among other things that it develop and implement a means of handling and processing aluminium chips that minimises the risk of dust explosions, and implement regular training on such hazards.