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Posted February 8
Industrial Air Filtration FAQ
Question: What types of industrial ventilation/filtration systems are available? Which one is the best solution for my workplace?
Answer: There are two main types of industrial ventilation systems that remove and control airborne contaminants. Source capture and Ambient Air Cleaning are the two recommended methods to filter dust, smoke and fume from indoor work environments. A source capture system, also known as local exhaust, can be configured in two different ways. A ducted system will use “air intake” devices such as backdraft hoods, capture arms, booth enclosures, downdraft tables or other pickup hoods to convey particulate into a ductwork system, which terminates at a central dust, fume or mist collector. The second capture-at-source method is to use self-contained air filtration equipment, such as mobile fume extractors, portable downdraft tables, welding booths or wall mounted collectors to capture, filter and recirculate air without the need to install ductwork.
An ambient air cleaning system, also known as dilution or general ventilation, reduces the concentration level of particulate within a work area by exchanging the air several times per hour. Air cleaners need to be strategically positioned in a concentric arrangement to ensure adequate movement of air throughout the facility and to prevent dirty air from stagnating.
Whenever feasible, self-contained source capture systems are the most effective solution to extract and filter airborne contaminants due to these key advantages:
- Lower equipment and installation costs (No costly ductwork and mechanical contractors)
- Protects the worker’s breathing zone (No respirators required)
- Less ductwork maintenance (No duct cleaning)
- Flexibility to easily reposition unit (No ductwork relocation)
- Lower energy costs (Unit can be turned on only when in use versus a central system)
- No costly air makeup system (Lower electrical cost)
Ambient air cleaning systems are necessary whenever it’s not possible to implement a source capture system due to impediments such as overhead cranes, very large parts and facilities with no available floor space. Some of their advantages include:
- Does not require workers to operate near the air cleaner
- Does not require repositioning a pickup hood to maintain a close distance to the source
- Wall mounted or chain hung units conserve floor space for other production equipment
Question: What type of dust collection system do I need to collect combustible dust? What are the advantages of a dry versus a wet dust collection system?
Answer: There are many different types of combustible dusts with different Kst and Pmax values, which describe the explosivity of a dust sample. It is important that companies undergo testing to determine the deflagration rate of their particular dust. Some of the most common dusts in the manufacturing sector include combustible metal dusts such as aluminum, titanium and magnesium fines. Once a spark comes into contact with an airborne combustible dust cloud, an ignition can cause a filter fire or a severe explosion in a confined space, damaging equipment and harming workers in the area. To avoid a dust explosion or fire, it is vital that the correct dust collection system be selected for your application. The dust explosion pentagon includes all the elements necessary for an explosion:
A dry dust collection system has no inherent protection against combustible dust. The cartridge filters inside the unit can catch on fire and the dust collector itself can present an explosion hazard. In order to reduce these risks, a cartridge dust collector can be equipped with fire detection and suppression systems to prevent dust fires.
Costly Accessories Required Include:
- Explosion Vent / Rupture Panel (Vent an explosion away from the facility)
- Locating the dust collectors outdoors
- Fire retardant filter media (Causes filter media to smoulder instead of burn, will not prevent combustible dust from igniting on the filters)
- Spark Arrestor (Prevents sparks from reaching and entering the collector)
- Remote solenoid Enclosure (Electrical safety)
- Non-Sparking blower wheel
- Abort Damper (Channel explosion away from collector)
- Sprinkler System (To extinguish fires)
Because of the many NFPA codes (61, 484, 652, 654, 664) which ensure that dry dust collectors are safe to collect combustible dust, installing a new collector with fire protection systems can be prohibitively expensive. However, there is another cost effective solution which does not require the same type of options. A wet dust collector operates using water as the filter media instead of using a solid media filter. Once combustible dust comes into contact with cascading water, the dust is immediately rendered inert and cannot catch fire. There is no need for fire detection and suppression systems. The main difference between the systems is that wet dust collectors allow you to comply with NFPA guidelines while avoiding the expense of installing suppression and detection systems.Whenever combustible dust is present, a wet dust collector provides a cost effective and safe means to collect combustible particulate.