Food Engineering

New regs on tap for combustible dust explosions

June 1, 2008




Thirteen workers were killed and more than 60 seriously injured in a catastrophic dust explosion at Imperial Sugar in Port Wentworth, GA on February 7, 2008. While the dangers of combustible dust explosions have been known for many years, the only applicable OSHA legislation is geared toward grain dust and dates back to 1987. Thus, the Chemical Safety Board (CSB) criticized OSHA for not having the tools to conduct ongoing inspections for potential dust explosions in any environment other than grain.

Recently passed House Bill H.R. 5522, Worker Protection Against Combustible Dust Explosions and Fires Act of 2008, seeks to expand coverage beyond grain dust to all combustible dusts. The bill states that 25% of all combustible dust explosions have occurred at food industry facilities.

The bill points out that OSHA has not initiated rulemaking in response to CSB’s recommendations, and there is no OSHA standard that “comprehensively addresses combustible dust explosion hazards in general industry.” While this bill still has to pass Senate scrutiny and obtain the President’s approval, it would require hazard assessments, written programs to define methods for inspecting and controlling dust, engineering controls, housekeeping, employee participation and written safety and health information plus adequate training to minimize the potential for dust explosions across all applicable industries.

According Gary Q. Johnson, Workplace Exposure Solutions principal consultant and expert in ventilation and dust explosions, OSHA, in response to CSB, has released its “Combustible Dust National Emphasis Program.” OSHA has also begun several audits of plants to check for proper safety procedures to mitigate potential dust explosions. As a result, OSHA has issued more than 200 citations for non-compliance. In addition, 22 states including Georgia now have their own jurisdiction and track manufacturers where hazardous dust is involved.

Not every powder has the same explosive power, says Johnson. For example, cornstarch has a Kst (bar-m/sec) value of 202, whereas sugar has a Kst of 138, meaning cornstarch provides more explosive force than sugar. Kst defines the value of a pressure wave from a resulting explosion. As most likely happened at the sugar plant, secondary explosions caused by poor housekeeping often do more damage than the primary explosion.