Managing Risks of Dust Hazards

Did you know that most fine dust particles generated from organic and plastic materials can combust rapidly and lead to an explosion hazard when dispersed in air?

Once such Dust explosions were seemingly confined to industries such as coal mining, wood processing and grain storage.  However food, pharmaceutical, plastics and other manufacturers may also be at risk. These include industries handling foodstuffs (eg grains, starch, flour, rice, sugar and cereals), paper, wood, fertilisers, pharmaceutical powders, coal, toner, metal powders and plastic powders. The increase in diversity of manufactured products means many more industries are now at risk from dust explosion hazards.

 

How do they occur?

Dust explosions occur when fine solid particles in the air catch fire. The dispersion of combustible particles to form a dust cloud allows rapid combustion to take place because of increased oxygen concentration around the particles. Factors that will also determine whether types of dusts are less or more likely to cause an explosion include their shape (flatter particles have more exposure to oxygen), size, concentration in the air and moisture content. Likewise, certain processes are more prone to creating dust clouds.

To catch fire, the dust cloud must come into contact with an ignition source of sufficient energy to cause a spark or flame. The minimum energy required to ignite a particle depends on the characteristics of that dust material. Finer dust is easier to ignite and also burns faster. Static electrical charges, like the ones that occur when our bodies come in contact with a metal object, can create a spark that’s strong enough to light a dust cloud with a low minimum ignition energy such as aluminium or PMMA plastic.

Ignition sources can range from a naked flame to a hot surface, mechanically generated sparks (eg metal parts rubbing), electrically-generated sparks or electrostatic discharge (eg dust collector bags with material drawn across the surface). The minimum energy required to ignite a dust cloud increases if moisture is present in the air.

 

How can I manage this?

You need A thorough onsite risk assessment should be carried out at premises where significant dust is known to be present. Any processes that create dust clouds are conducive to explosions. Anything sawing or grinding wood or dropping fine material by gravity from hoppers into silos. Also processes that create elevated ambient temperatures, exposure to heat sources or elevated pressures also increase the likelihood of a dust explosion.

Certain process equipment that are prone to dust explosions include dust collectors, pneumatic conveyors, silos, sanders and grinders.

 

What are good reduction strategies I can use

If you have established that your business is at high risk of a dust explosion, then you should take steps to minimise the dangers such as: