Where combustible dust is a concern, there is only one sure sign that your safety protocols are working: zero safety incidents. But even a perfect past safety record is no guarantee that you will never have an incident in the future. Keeping your facility and your workers safe requires constant monitoring of the environment for unsafe conditions. Even a small detail could make the difference. While we cannot cover everything in this article, we will examine six areas that should be on your list of unsafe dust collection conditions.
What are the Signs of an Unsafe Dust Collection System?
One of the most telltale signs of an unsafe dust collector environment is a dust leak. Failure to maintain a clean, dust-free environment is a big red flag that your dust collection system is not operating safely.
A dust leak from any piece of equipment—and not just from dust collection equipment itself—is a hazard. Dust leaks can spring from mixers, ductwork, grinders, screw conveyors, or almost any kind of machinery or manufacturing equipment. And any dust that collects because of those leaks is a fire hazard, susceptible to not only sparks but also from disruptions or vibrations that could send the dust airborne. Whatever the catalyst, this flying dust can create a flash fire or an explosion. Although poor housekeeping is the most common issue, it is also the most noticeable and can be easily addressed.
Lack of bonding and grounding
For any kind of material that is sensitive to sparks, including combustible dust, bonding and grounding are critical. Static buildup from equipment or machinery can create sparks that can ignite a dust cloud inside a piece of equipment or inside ductwork, for example. Bonding simply means taking two pieces of equipment and tying them together with a wire so that they are at the same potential. In other words, if a piece of equipment has a slight positive charge, that positive charge is carried over to bleed off any charges. Grounding means physically putting a stake in the ground and wiring the equipment to this grounding stake so that any charge or static electricity has a place to escape to prevent a spark that could potentially ignite dust.
If equipment sits on an insulated pad, for example, the equipment must not only be bonded together, it must also be grounded. Bonding and grounding go hand-in-hand. Since gasket material and paint are insulators and there is not always metal-to-metal contact between equipment, bonding ties things together, and then grounding directs any charges into the ground.
A lack of proper bonding and grounding is an important sign of an unsafe dust collection condition. If you have dust that is sensitive to static buildup and/or spark or ignition under low spark energy, you must have bonding and grounding.
Although this may seem obvious, any equipment that is making a squeaking noise, because it is not properly lubricated or needs new bearings, is another sign of an unsafe condition. This could be a fan or a piece of takeaway equipment, for example, or anything that could create a heat source, including the friction caused by metal rubbing against metal. This creates an unsafe condition because heat and/or metal sparks can ignite combustible dust. For this reason, certain pieces of equipment are often made of nonmetal materials, stainless steel or aluminum, to minimize heat or sparks caused by friction. Always be aware of any unusual machinery noises.
It is important to make sure that dust is being properly discharged on a constant basis and does not build up on the inside of equipment or ductwork. This can occur if there are internal ledges inside the dust collector equipment. If you have a dust collector that has internal ledges, or places where dust can build up, can create an unsafe condition. For example, if an access door has a flat bottom, the dust can build up on the door ledge. And wherever there is a buildup of dust there is the potential, in some cases, for self-ignition.
Coal dust, for example, is notorious for self-ignition. A pile of coal dust can set itself on fire solely from the friction between the particles as it settles due to gravity. This alone can cause enough heat and friction to ignite fine coal dust particles. If that smoldering fire or a single spark is uncovered and put it into a piece of equipment, it can gain oxygen, ignite and cause an explosion or fire.
Internal ledges where dust can collect and potentially ignite should be eliminated as an important unsafe condition that should be part of your inspections. Be sure the duct velocities are monitored and maintained above the duct carrying velocity.
A little-known factor that can contribute to unsafe conditions is a lack of airflow. If a fan is not pulling enough air volume, creating enough operating pressure, and conveying velocity to keep dust in the airstream, gravity can cause dust to settle in the ductwork. This creates piles of dust inside the ductwork, and that dust is prone to ignition.
Inadequate suppression system
Another unsafe issue from the standpoint of combustible dust is the lack of explosion protection equipment. Without properly designed explosion vents or suppression systems, or other means to mitigate an internal explosion—along with isolation valves to keep the explosion from moving from one piece of equipment to another—you have a situation that must be addressed.
Dust collectors have a long life, in general, and many systems were installed prior to the emphasis on combustible dust systems that are recommended today. If an inspection of your dust collector system reveals a lack of, or inadequate, fire and explosion suppression or venting, this is an unsafe condition.
These are just a few signs of an unsafe dust collector system. There are many more, and it is not possible to fully explore this topic in a single article. Sly recommends that you should not try to address these unsafe conditions on your own. Always seek professional expertise.
Sly, Inc. has been helping companies safely collect dust for over 100 years. We can help you evaluate your dust collector system and customize a solution to resolve any unsafe conditions that may exist in your operation.
Contact us today for a consultation.