Combustible Dust: Even Food Can Explode|
When we think of industries where fires and explosions are a serious threat, the first thing that normally comes to mind is usually something involving gasoline or petrochemicals. And why not? After all, incidents involving explosions and fires in the petrochemical industries have resulted in some pretty sensational news headlines and just about anyone in the developed world is aware of how dangerous flammable chemicals can be. Unfortunately, despite great strides towards better regulation and safeguards, incidents still occur with some frequency and events such as the BP Oil Spill only serve to further cement the fact. Just as dangerous and yet much less well publicized or well know however are the fire and explosion dangers present within the food industry. Yes, you read this correctly. The food industry has many of the same issues with fires and explosions as the petrochemical industry. Although it might at first glance seem almost disingenuous, the sugar and flour on your local supermarket’s shelves once had the potential to cause explosions big enough to destroy an entire building. The corn meal in your kitchen cabinet could have easily acted as an explosive fuel before it made its way to market. Even the baking soda in the refrigerator could have blown the roof off of a processing plant. If this seems ridiculous or some sort of urban myth, read on and learn how something as innocuous as a bag of flower could burn down a warehouse.
First and foremost, familiarize yourself with the term “Combustible Dust”. This is the heart of the problem and the core explosion and fire danger in the food processing industry. Combustible dust, as the name implies, is dust that can be easily ignited and oxidized, or in other words, burns very easily. At first glance it would be easy to assume that this must mean things like sawdust or gunpowder residue and indeed these two do fit the combustible dust definition quite well. However, the mistake is in thinking that combustible dust must be made of things that we assume are easily burned in any form, not just as a dust. The fact is, just about any material if ground up small enough can burn very very easily. Not just burn, but actually explode under the right conditions. In order to understand why this is it is necessary to understand how things actually burn.
How readily something burns is largely a function of density, surface area, mass and heat. Since buring takes place at the surface of a material, the denser a material and the smaller its mass and surface area, the more difficult it is to burn. A lump of coal for instance is fairly dense and has a small surface area. As a result, it takes a substantial amount of heat to start the oxidization process and once started this process occurs fairly slowly. This is why coal has become popular as an energy source as it provides a fairly stable and steady source of heat energy once ignited. Now, if we grind that same lump of coal into a fine particle, we have greatly reduced its density and greatly increased its surface area without losing any of its mass. The result is that a great deal less heat energy is needed to ignite the coal and once ignited, the oxidization process happens extremely rapidly. Whereas the lump of coal takes a long time to ignite and burn, a cloud of coal dust exposed to something as small as an electrical spark can literally flash into flames, in effect causing an explosion.
What is really interesting here is that this is possible with just about any solid material. Aluminum, steel, wood, corn, wheat, oats, sugar and the like can all become extremely volatile when ground into fine particles and explode under the right conditions. To underscore the fact, OSHA estimates that 30,000 facilities are at risk from combustible dust explosions. As recently as 3 years ago sugar dust ignited at a Georgia plant, killing 14 workers. In recent years as incidents have occurred, more focus has been place on the dangers of combustible dust, enough so that major news outlets have run in-depth documentaries on the subject and contentious combustible dust litigation battled over in political circles. Even so, combustible dust simply is not something the public normally associates with food, which makes it even more dangerous as full awareness is difficult to instill in even those working within the food industry.
Part of how the problem is managed is through mechanical and engineering solutions that reduce the risks posed by working with materials that result in the production of combustible dust. One of the most effective ways that risk is reduced is by removing or limiting possible sources of ignition. Since combustible dusts can be extremely flammable, even the small sparks produced by light switches or heat from hot lamps can be enough to cause ignition. As a result, much of the same explosion proof electrical lighting equipment used in the petrochemical industry is equally effective in the food industry as well. A Larson Electronics Explosion Proof Fluorescent Fixture for instance is equally at home on an oil rig as well as in a sugar processing plant. This sort of lighting removes the potential for ignition by sealing off any possible contact with sparks or flames and operating at temperatures below what could possibly ignite flammable materials. Some explosion proof lighting is designed to allow hot gases to escape from the lights housing, but only after it has cooled enough to be incapable of causing ignition. Others are simply sealed entirely and do not produce enough current to cause a spark or flame and there are known respectively as explosion proof or intrinsically safe.
Regardless of how it is managed, combustible dust is impossible to remove from industries where processing of materials requires breaking it down either by grinding, chopping or other means. It can be managed, but this requires a great deal of awareness, vigilance and attention to detail as well as use of the proper equipment.