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EXPLOSION SAFETY T


he airborne dust created by many manufacturing facilities that generate, handle, transport, process or store materials that cause or become combustible dust is no mere housekeeping problem. Once those particles have settled in difficult- to-reach places throughout a site, any subsequent disturbance can produce a potentially explosive dust cloud. The creation of a risk mitigation plan is therefore necessary for most facilities - including many that would not traditionally be considered ‘dangerous.’ Along with studying legislation requirements in your region, reducing the likelihood of an incident is the best possible step, beginning with ‘Is my dust actually combustible?’


This is not as straightforward as it might sound. Few people would smoke a cigarette while refueling their car, yet many would not think twice about lighting up while taking a break from working on home renovations that have produced an abundance of sawdust. Any fine material that can catch fire when mixed with air is a potential risk. Examples include most solid organic materials (sugar, flour, wood, etc.), metals, and more. In fact, even partly oxidised aluminium dust generated from plasma cutting can be considered explosive under certain circumstances – only a proper risk assessment can provide reassurance. Sending a sample of your dust to a qualified lab is a good place to start. If it is shown to be combustible, further tests will determine if it is explosive, how quickly that can happen, and how much force it can carry. This information will help direct the selection of equipment needed to mitigate the hazard.


AIRBORNE DUST AND EXPLOSION


SAFETY: AN INTRODUCTION TO COMBUSTIBLE DUST


By Koen Oostvogels, application development engineer at Donaldson


hand from view would be considered a risk - or, in more practical terms, a dust layer of just 0.5mm. But, rather like how propane gas is only dangerous between 1.8 - 8.4 per cent concentration volumes in the air - particle size is a key factor. Germany’s Occupational Safety & Health Institute documents outline the results of its testing of a variety of dust samples, including their particle size and concentration required to allow combustion. Sawdust, for example, is generally only a risk


when smaller than 63 microns - the finer the dust, the more reaction surface it has with oxygen - and in a concentration above 30g/m3


So, let’s say the smoker we mentioned earlier has been working in a 150m3


room, and


there’s a 0.5mm layer of dust on the 50m2 floor. That would result in 0.025m3


at a typical density of 600kg/m3


15kg, which, if it became airborne, would produce a dust concentration of 100 g/m3 creating an obvious danger.


of dust, and, , that equates to - .


THE EXPLOSION PENTAGON — RISK MANAGEMENT STRATEGIES


While managing any one or more of the well- known Fire Triangle’s elements of oxygen, heat and fuel can decrease the fire risk, explosion risk-management strategies must consider another two elements. Dust dispersion and dust confinement produce the Explosion Pentagon - and may require a separate strategy to address any remaining explosion risks. The Explosion Pentagon’s fuel element is the finely dispersed dust cloud. As a rule of thumb, a cloud dense enough to screen your


12 MAY/JUNE 2023 | INDUSTRIAL COMPLIANCE


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