The Joint Foundry Explosion Investigation Team report, released Oct. 6, was compiled by the Occupational Safety and Health Administration (OSHA), the Massachusetts State Fire Marshall Office and the Springfield Arson and Bomb Squad. It follows the company's Aug. 24 settlement with OSHA that resulted in 40 violations and a $148,500 fine.
The report and citations found that inadequate housekeeping, ventilation, maintenance practices and equipment were causal factors. Two of the violations were related to the fire and explosion at the plant that produces small- and medium-sized ferrous castings.
The fire, which began in one of the shell mold stations in the shell mold building, was pulled into the exhaust ventilation system, the report concluded. The system's interior ductwork was heavily loaded with deposits of phenol formaldehyde resin, an explosive organic dust.
Ignition of the dust caused a turbulent fire and explosion that traveled through the ductwork and shook down explosive concentrations of combustible resin dust that had collected on surfaces throughout the building. When the fire exploded out from the ductwork, it ignited the airborne concentrations of combustible dust and caused a catastrophic dust explosion, which lifted the building's roof and blew out its walls.
The report notes that, although it was not possible to conclusively determine the initiating event that caused the explosion, a number of scenarios developed from physical and testimonial evidence. The two most probable scenarios:
- Heavy deposits of resin dust were found in the flexible exhaust ducts serving the ovens in the small molding stations. Open ends of the ducts were placed adjacent to the ovens. Jarring of the ducts caused dust to fall onto the oven and be ignited.
- Fuel flowed to an oven that was not lit because fuel trains to the ovens in the shell molding stations were found to be in bad condition. The unburned gas was ignited by the pilot or other ignition source.
"It is hoped that the release of this report on the findings of the joint investigation will allow other foundry facilities to assess their situations and apply lessons learned here in time to prevent a similar tragedy," said Ronald E. Morin, OSHA area director in Springfield.
Copies of the 56-page report are available by contacting the OSHA Springfield office at (413) 785-0123 or the U.S. Department of Labor's Regional Public Affairs Office at (617) 565-2072.