Dust Busters, Combustibles and Explosions

02/02/2010

They can seem like harmless substances - sugar, coal, wood dust, flour - however in certain conditions and across many industrial processes, dust from these - and other substances can become the fuel for an explosion. Many workers have died and hundreds have been injured over the past few decades as a result of dust explosions. Part of the problem is that dust explosion hazards are often unrecognized. Investigations of such accidents have shown that the material safety data sheets (MSDSs) did not adequately describe dust hazards for the substances involved in these explosions.

MSDSs must identify this hazard and disclose information on appropriate engineering controls to be used to prevent these explosions. Unfortunately the dust explosion hazard is not always declared, contributing to a general lack of awareness of this hazard amongst workers, and potentially putting them at risk for injury or even death.

Industries and substances at risk of dust explosions
A combustible dust explosion hazard may exist in a variety of industries, including:

• metal processing
• wood product manufacturing
• chemical manufacturing
• food and pharmaceutical production
• grain storage
• fabrication of rubber and plastic products
• coal-fired power plants

Combustible materials connected with dust explosions include dusts from coal, chemicals, wood, rubber, grain, sugar, flour, and metals. Most natural and synthetic organic materials, as well as some metals, can form combustible dust if they are processed in powdered form.

How dust can explode
For a dust explosion to occur, five conditions must be present at the same time. The five elements are referred to as the explosion pentagon, and include:

• combustible dust (fuel)
• ignition source (spark or heat)
• oxygen in air (oxidizer)
• dispersion of dust (into the air forming a dust cloud)
• confinement of the dust cloud (building or ceiling)

A dust cloud that is ignited within a confined or semi-confined vessel, area, or building, burns very rapidly and may explode. This could cause fires, additional explosions, flying debris, and the collapse of parts or all of the building. An initial explosion that occurs in processing equipment or in an area where there is an additional accumulation of dust, may shake excess dust loose, or damage a containment system (such as a duct or vessel). The additional dust released into the air, if ignited, can cause one or more secondary explosions that can be even more destructive than the first explosion.

Although suppliers cannot predict every possible use of their products, they can help prevent explosions and injuries by ensuring that MSDSs contain the complete hazard information workers need to work safety with substances and materials that could potentially combust and/or explode.

Further Information:

AplusA-online.de - Source: Canadian Centre for Occupational Health and Safety