Accumulations of combustible dust within industrial facilities create the potential for severe dust explosions, concludes the U.S. Chemical Safety and Hazard Investigation Board, in a new report.
Perhaps the most serious hazard is the potential for secondary explosions, which occur when building vibrations or gases produced by a smaller explosion disperse dust on surfaces into the air. The dispersed dust cloud is subsequently ignited by the advancing flame front of the initial explosion or by other ignition sources.
Secondary explosions can be devastating because they tend to bring large amounts of dust into involvement. Three recent dust explosions are briefly described below:
Jahn Foundry, Springfield, Mass.: Powdered plastic resin used as a sand binding agent accumulated on surfaces in the mold fabrication room of a foundry. On February 25, 1999, the shock from an initial explosion in a dust extraction duct dispersed the accumulated resin into the air, setting up secondary explosions. Twelve employees were burned over 40 percent to 100 percent of their bodies; three of these victims later died. The explosion blew out walls of the building and lifted the roof.
Ford Motor Company, River Rouge Plant, Dearborn, Mich.: On February 1, 1999, a natural gas explosion in an idle power boiler at the River Rouge plant disturbed coal dust that had accumulated on surfaces in the facility. The result was a large secondary dust explosion. Six workers were killed, and 14 were seriously injured.
Rouse Polymerics International Inc., Vicksburg, Miss.: On May 16, 2002, a secondary dust explosion occurred at a Rouse recycling facility. Five workers were killed, and at least seven others were injured. The explosion was fueled by accumulated rubber dust generated from the grinding of scrap tires.