Between 1903 and 2010, 190 dust explosions were recorded in the ARIA database of the Bureau d’Analyse des Risques et Pollutions Industriels (BARPI).
There have also been numerous dust explosions due to the accumulation of electrostatic charges on equipment.
The assessment of ATEX caused by the presence of dust and electricity remains a major challenge in improving workplace safety.
Dust explosions in the presence of static electricity: how do they form?
It’s hard to imagine that mere dust could cause an explosion. But it’s true.
Because of their physico-chemical characteristics, dusts can cause this kind of phenomenon.
In this case, the formation of an ATEX atmosphere requires :
- A source of dust or powdery products in suspension.
- A source of ignition: often hot surfaces or the accumulation of an electrostatic charge causing sparks.
But several conditions must be met to cause an explosion:
- Explosive range: the explosion of a dust cloud depends on factors such as particle size, dust humidity, pressure, temperature and concentration of inert gases.
- Particle size: the lower the weight and size of the dust, the greater the risk of violent explosion. The probability of an explosion becomes low for dusts larger than 500 μm.
- Ignition source: in the case of electric/electrostatic sparks, this must be greater than the minimum ignition energy (MIE) of the dust, which is generally between 0.1 and 100 joules.
What industries are affected by dust explosions?
Every sector of activity has its own specific characteristics when it comes to dust-related ATEX risks. Which industries are most affected? What equipment is conducive to the formation of electrostatic charges?
Sectors of activity
Dust cloud explosions caused by static electricity affect all branches of industry.
In fact, dusty ATEX requires only the presence of products in the form of fine particles of oxidizable matter, such as food, vegetable, metal and industrial dusts.
According to a comparative study published by INRS in 2010 , the most affected sectors are still wood and food processing.
Sources of ignition
According to the same study, most sources of ignition are mechanical sparks (electrical or electrostatic) linked to ambient static electricity.
But open-flame fires and hot-spot work are also dangerous sources.
The equipment
The equipment most affected would be silos and hoppers, as well as dust collection systems.
The use of these dust-laden air filtration devices may give rise to the risk of dust explosions.
How to prevent dust cloud explosions caused by static electricity?
Here’s everything you need to do to prevent the risks associated with explosive dust atmospheres in your plant.
Securing the workspace
By carrying out an electrostatic risk assessment and an ATEX zone assessment at your facility.
The aim? To prevent the formation of dust clouds, but also to protect equipment that can accumulate charges, thanks to high-performance earthing systems (in compliance with NFPA 77 – IEC 60079-32-1 standards).
Raising awareness among staff
To ensure a safe working environment for your employees, it is essential to draw up strict protocols for the use of equipment, as well as prevention plans for all identified ATEX zones.
Last but not least, don’t neglect to wear the right PPE and get training in the various risks present on your industrial site.
Other recommendations
Furthermore, it is essential to take into account the danger of dust deposits whose suspension cannot be controlled.
In fact, the presence of this dust can cause an explosion to spread from close to close by lifting the dust deposited on various surfaces.
These are known as secondary explosions, and are generally more destructive than the initial explosion.
Do you want to avoid the risk of dust cloud explosions?
ADF Systèmes makes it a point of honor to help you choose the products and solutions best suited to your industrial safety and risk management needs.
To find out more about ESD risks, download our guide to earthing.
