On Feb 4th, 2009, on the first anniversary of the dust explosion that took place at the Imperial Sugar factory, the US Chemical Safety Board released a video message. In the video (see below) the CSB chairman John Bresland asks federal regulators and businesses to increase efforts at preventing combustible dust fires and explosions.
For those who remember, the incident was one of the worst dust explosions ever, with 14 fatalities.
Just a few days ago, a coal dust explosion rocked the Oak Creek We Energies power plant. It took place in a silo and injured 6 contract workers. Fortunately there were no fatalities. One of the workers described a loud explosion and a ball of fire came rolling down at them inside the 65 foot high silo, making them scramble to safety, reports the Journal Sentinel of Milwaukee.
What is the cause of so many dust explosions? The CSB completed a major study of such combustible dust hazards and has urged the Occupational Safety and Health Administration (OSHA) to develop a comprehensive regulatory standard designed to prevent dust explosions. OSHA has not issued a standard but has developed a program to increase enforcement of existing regulatory provisions.
One of the causes of these dust explosions is a possible electrical ignition source, due to using non-dust ignitionproof motors, switches and other non-protected electrical and instrument equipment in hazardous areas. Most industry people think of hazardous areas as those that contain flammable solvents and vapors, but fail to remember that hazardous areas also cover dust prone areas. These include grain silos, coal processing and storage plants and yes, even sugar factories. (Under the North American codes, these are classified as Class II hazardous areas and under the IEC codes, these areas are classified as Zone 21 and Zone 22)
Once a dust explosion takes place, it causes severe damage and the only way to safeguard lives and machinery, is by prevention. Use of explosion protected equipment that is certified for use in dust hazardous areas is a must.
(You can learn more about hazardous areas and dust explosion protection in Abhisam Software‘s e-learning program on Hazardous Area Instrumentation).
Comments are welcome, as usual.