Reducing the risk of dust explosions in the food industry

Dust explosions are a known and preventable danger. Installing certified dust ignition proof motors helps to mitigate the risks.

The dangers of dust explosions in food and beverage plants have been well publicized, but devastating accidents still take place far too often. Almost a quarter of all reported industrial dust explosions occur in the food and beverage industry. In early 2008, for example, an explosion of sugar dust at the Imperial Sugar Company’s plant in Georgia, USA resulted in the deaths of 14 people and left a further 38 injured.

What causes dust explosions? And what can be done to reduce the risks? A lot of common foodstuffs like grain and flour, sugar, starch, and cocoa powder are highly combustible when they are in the form of fine dust. In the right conditions, a hot surface or spark can be sufficient to ignite the dust and cause an explosion. In all, five factors are required for a dust explosion to occur:

• presence of combustible dust
• dispersion of dust particles in the air
• confinement (e.g. an enclosure or closed structure)
• oxygen to sustain the fire
• ignition source (such as a hot surface or spark)

It is the final factor in the list that concerns electrical equipment like motors. Equipment that is certified dust ignition proof will not provide an ignition source – it will not cause a dust explosion even if all the other factors are present.

Dust ignition proof certified motors are designed so that dust cannot enter the motor’s enclosure, and therefore cannot get into contact with hot surfaces inside. This is achieved by using special seals and joints. At the same time, the motor is engineered so the temperature of the external surface will not exceed the motor’s temperature class under normal running conditions.

The dust ignition proof motors we supply are certified as dust ignition proof according to ATEX and IECEx standards, and many other local certificates are available. The fact that these motors are specifically certified as dust ignition proof is an important point. We’ve heard of plants that have mistakenly installed motors with the wrong type of certification – such as flameproof motors meant for the oil and gas industry – in areas with dust hazards. This is a dangerous practice, because motors that do not have dust ignition proof certification do not provide sufficient protection against dust explosions.

We offer a full range of dust ignition proof motors in both cast iron and aluminum frames. An important advantage of the aluminum motors is that they have a very smooth surface which prevents dust from collecting on the motor. This makes the motors easy to clean, improving safety and reducing cleaning costs. These motors are also easier to mount because they have a lightweight frame and smaller footprint. They are complemented by cast iron frame motors that can deliver higher powers and offer additional speed and design solutions. Both the aluminum and cast iron certified dust ignition motors are available in IE2 and IE3 efficiency classes.

Investing in safety and peace of mind doesn’t have to come at a high cost, because certified motors only cost slightly more than regular motors. And if upgrading to dust ignition proof motors means getting a higher efficiency class, then savings in energy costs could make the payback time very short.

At ABB we have a long track record in helping customers in the oil and gas industry to meet rigorous safety requirements for their motors and generators. Installation of safer equipment has helped to realize a big reduction in the number of explosions in that industry. We hope we can play our own part in bringing about a similar improvement in the safety record of the food and beverage industries. Let’s put safety first!

Links:

• Presentation
• Leaflet about dust ignition proof aluminum motors
• Visit our web site for dust ignition proof motors