If you were asked to make a list of potentially combustible materials, chances are good that you wouldn’t think to include dust. It’s seemingly innocuous, and, in the average, day-to-day sense, is little more than a slight annoyance that we must wipe off our furniture, etc., from time to time.
However, “dust” is a common byproduct of a wide range of manufacturing processes, and can be generated from nearly any solid material—including highly flammable and combustible ones. In fact, dust combustion has been the cause of some of the worst industrial accidents in recent history.
An Ounce of Prevention…
…is worth a pound of cure, as they say, so it’s unsurprising that the best method of minimizing dust explosion risk is to reduce or eliminate dust. Without dust, there is no fuel to burn and, therefore, no risk of combustion. (You may consider “combustion” to be a synonym for “explosion,” and you’re not exactly wrong; however, many explosions are nothing more than tightly contained, quick burning fires—the tight quarters are what causes the explosive action, not the materials or the nature of the fire itself.)
It should be noted that a wide range of materials, even those that wouldn’t normally be considered a combustion risk in their solid, non-dust forms, can create combustible dust. Corn, for example, is not especially flammable straight off the cob, but when dried and dust-ified, it becomes highly combustible.
There’s no amount of effort and no special equipment that can prevent the creation of incidental dust. The very nature of many manufacturing and processing procedures makes dust all but inevitable, and heat from machinery, sparks, or other unavoidable occurrences can turn process dust into combustible dust. The key, then, is to prevent this dust from accumulating to potentially dangerous levels.
The best way to avoid dust accumulation is to clear the dust away as it is produced. High pressure vacuum or pneumatic conveyor systems (similar to the tubes at the bank drive-through) can be employed to essentially vacuum up the dust. These vacuum conveyors move both the materials being used in whatever your process is and the dust that process creates. Dust collectors built into the system capture dust for safe disposal. Additionally, pneumatic conveyors produce less friction, which in turn reduces the amount of dust that is created.
A more straightforward, but equally effective, dust control method is a mist or flood system. These relatively simple systems can spray water across the areas where dust amasses, either constantly or at timed intervals. The water and dust run to a floor drain where they can be collected; the dust can then be filtered out, and the water reused.