Using Explosion-Proof Dust Removal Equipment
Combustible dust explosions can occur at your facility, and a dust collector with the wrong type of protection is often the main cause. Adding reliable explosion protection equipment to your collector can control an explosion to keep employees safe and minimize damage.
An explosion isolation valve installs over a standard vent to prevent the propagation of the overpressure and flame front generated in a deflagration. It works by utilizing metal fins to cool the pressure wave and extinguish the flames.
As materials break down and particulate falls off during handling, industrial processes often create combustible dusts. These dusts can be generated by food processing such as grain and flour, carbonaceous products such as coal and charcoal, metallic and nonmetallic inorganic materials including aluminum and plastics, among others.
Using explosion-proof equipment prevents these dusts from becoming more explosion-proof dustremoval equipment significant and prevents damage to the surrounding areas. It also reduces the chances of more serious injury to employees and avoids greater financial loss.
Venting is one of the most important safety features to look for in explosion-proof dust collectors. This feature can prevent a deflagration by directing the pressure wave from the dust collector through an area outside of the hazardous area. This system is usually installed in the inlet or outlet ducting and works with a valve that closes within milliseconds of detecting an explosion, effectively mitigating the pressure effects of the deflagration and protecting the dust collection vessel.
Alternatively, a chemical isolation system can be used when it is not feasible to vent the pressure effects of an explosion to the outdoors. These systems detect an explosion hazard and release a chemical agent to suppress the explosion and protect the ducting. They can be integrated into the inlet or outlet ducting and are usually comprised of an explosion pressure detector, flame detector, and a control panel.
2. Chemical Isolation
Many industrial processes generate combustible dust in high concentrations. This dust must be collected and stored safely to prevent fires and explosions. Most combustible dusts have the potential to explode if an ignition source enters a closed vessel such as a dust collector.
During the DHA, a certified NFPA inspector will evaluate the dust collection equipment housing and hopper as well as inlet and outlet ducting to determine whether your facility is at risk of an explosion. Inspectors will also consider the Kst and Pmax values of the dust. These values will be used to size your explosion venting or suppression system.
If the combustible dust has a low Kst value and is not likely to ignite when exposed to an ignition source, a simple passive venting system may be enough. However, if the dust is combustible or explosion-proof dustremoval equipment explosive (most Class ST1 and some Class ST2 and ST3 dusts), you will need an active system to protect your facility.
A chemical isolation system detects an explosion hazard and, within milliseconds, releases an agent to suppress the flame front and minimize pressure increase in interconnected process equipment. A fast-acting mechanical valve installs in either inlet or outlet ducting to create a barrier that isolates pressure and flame fronts from each other, eliminating the likelihood of upstream and downstream deflagrations.
3. Flameless Vent
Flammable and explosive dusts such as flour, coal powder, wood chips, cotton staple fibers and individual metal powders can explode when mixed with air. This explosion can generate temperatures up to 3000 degrees and flames can spread up to 200 feet in a blast wave that can be catastrophic if vented outside. The explosion vents on equipment must be rated to handle the blast pressure and energy that would otherwise be released, but it is crucial for safety to keep this pressure in the confined space of the dust collector.
This is where a flameless vent comes in. This device combines an explosion vent with a flame arrestor to prevent the upstream and downstream propagation of the deflagration from extending beyond the initial vessel. The mesh of the flame arrestor dissipates heat from the blast, reduces the fuel’s burning temperature and extinguishes the fireball, preventing the explosion pressure to be vented into process equipment or plant areas.
There are three different types of flameless vents: tube-style, box-style and a newer variation that’s certified for metal dusts, the Q-Rohr. The tube-style, also known as a quench tube, uses a cylindrical flame arrestor that pairs with an explosion vent for a smaller footprint that’s great for applications with elongated vessels like bucket elevators and conveyors. The box-style features a rectangular stainless steel mesh flame arrestor in a slimmer profile for use on dust collectors, storage bins and conveyors.
4. Passive Vent
Almost all industrial manufacturing processes generate combustible and explosive dust particles. Using the right equipment to safely extract these airborne contaminants from your shop significantly reduces the risk of serious accidents. But if those contaminants are not removed from your work area properly, they could return to the point of origin and cause a massive explosion or fireball.
The first step in selecting the proper industrial dust collector for your business is to determine the types of combustible and explosive dust that are generated by the process. Different types of dust require different safety precautions, and you will need to select a dust collection system that is certified to meet those standards.
For example, the Tiger-Vac CD-600EX and CD-1200EX stainless steel portable dust collectors are fully compliant with NFPA and 3rd party safety standards for use in zones 22 and 23. They meet OSHA standards and work double-duty as HEPA air cleaners by exhausting clean, breathable air back into the workspace.
A non-return flap, or explosion venting valve, is another simple and inexpensive method to protect your plant from explosions. When activated, the valve immediately closes a pipeline and prevents it from being used to transmit an explosion to other areas of a facility.
Other safety options include flameless venting, which is designed to be a safer alternative to traditional venting. It uses metal fins mounted on a directional vent to divert an explosion’s pressure wave and cool it quickly. However, you must be sure to leave enough space around the vent that an explosion can’t be redirected into an adjacent area like a walkway or equipment.