Table of Contents
What is Mist Collection?
Manufacturing companies have been using some form of mist collection system since the beginning of the industrial revolution. Beginning with an open window and evolving into the media based and electronic solutions available today.
Machinists and metal manufacturers now install industrial mist collectors for the vast production, maintenance, health & safety benefits they provide. The more notable benefits are:
What is Mist?
To best understand mist collection, first you should understand mist. The true definition of mist is, “a cloud of tiny droplets suspended in the atmosphere that limits visibility”.
Across industries, mist is made up of oil or other coolants that are byproducts of metal working. Industrial hygienists consider mist as being a liquid particle 20 microns or smaller.
So how small is 20 microns? table salt is 125 microns, a human hair is 70 microns in diameter and anything below 50 microns is undetectable by the human eye. Because the particulate is so small it is an aerosol meaning that it suspends in the air and travels easily.
What is Smoke?
What is Oil Mist?
What is a Mist Collector?
Media Based Collectors
Media based collectors consist of a physical filter material. Whether it be metal, paper, synthetic, or some other material a physical barrier is involved. There are a variety of designs offering single stage and multi-stage solutions to best fit your needs.
Common types of media filters are drum, vee and cartridge. This is because they are typically of simple design, maintenance is equally simple. Media based collectors are an excellent choice for oil & coolant mist as well as light smoke.
Electrostatic Precipitators (ESP)
Electrostatic Precipitators are an electronic form mist and smoke collection. The system draws contaminated air across an arrangement of ionizers and collection plates. The ionizer section places a positive charge to anything coming across it and is then introduced to a series of negatively charged plates.
The combination acts like a dust / mist / smoke magnet. The true benefit to this method is that it does not care about particle sizes, it will place the positive charge to anything conductive that crosses its path and collect it accordingly. The filters used are permanent filters and are cleaned and reused. Maintenance of this method is typically a bit more labor intensive to keep the system operating at a high level. Electrostatic Precipitators are an excellent choice for oil based mist and smoke.
Please feel free to contact R. Williamson & Associates to have a sales engineer guide you through the selection process and avoid costly inefficiencies.
Methods of Capturing Mist
When the equipment does not allow for source capture another solution is ambient collection. A collector would be hung in the general space around a mist generating piece of equipment. The air moving through the collector would then draw a vacuum and remove the mist from the air.
Why you need a mist collector
By removing the mist and smoke from your facility you gain an increased indoor air quality providing a safe and healthy work environment (OSHA.gov source). Additionally you remove the oil from the building surfaces reducing the risk of accidents and damage to other expensive equipment. Mist collection is truly spending a dime to get a dollar. The benefits of a mist and smoke collector will provide you with a return on investment throughout its life.
Equipment that Generates Mist
Metal Cutting Operations
Metal applications such as turning are comprised of lathes, turning centers and screw machines. When the manufactured part rotates an oil or water-soluble coolant is sprayed on it. Not only does this lubricate the part being manufactured, but it also keeps it from overheating, removes debris and reduces defects. Turning mist is 20 microns or less.
Some turning mills run hot and produce smoke when using oil. Therefore a smoke rated filter is recommended.
Metal grinding mainly consists of surface, profile, centerless, and cylindrical grinding. Grinding metal generates heat and dust. Therefore water-soluble coolants keep it cool, provide lubrication and flushing the debris and dust. Metal grinding produces mist larger than 2 microns.
Heading & Stamping
Using metal to repeatedly hit another piece of metal using immense pressure results in a lot of heat, mist and smoke. Therefore a mist collector and other filters are necessary for heating and stamping metal operations. The typical size is .07 to 2 microns of oily mist and smoke.
Heat treating, quenching, and annealing use a combination of heat and cool metal parts to reach the desired material asset. Water, brine and oil, are typically used to reduce the temperature of the metal parts. When cooling metal smoke, steam, metal scale and mist are emitted.
To collect these various mists, several filtration systems are necessary to manage solids or metal scales. The mist and smoke need a seperate filter. The water, brine and oil emit 0.8 to 5 microns of mist. Smoke is .07 to 1 micron. The metal scale and fumes are .5 to 2 microns.
Drawing operations produce heat and typically use water-soluble, soap-based, wax-based or straight oil. The water-based lubricant generates mist. The mist collectors require a decent holding capacity for solids. Prefilters are recommended to remove the soaps and wax, which reduce the life cycle of the primary filter. The water-soluble mist is 1 to 20 microns. Oil is .5 to 2 microns and smoke is .07 to 1 micron.
Washing parts require steam, water mist & water vapor to remove lubricants, oils and greases. A substantial amount of water vapor and steam. Unfortunately, mist collectors cannot filter vapors, therefore a separate filter & media is required to collect that.
There are some part washing applications that use a rust inhibitor to prevent rust. These applications require a filter with depth-loading features. Not having one will reduce the life of the filter. The water mist from the vapor, steam and dropels emit up to 10 microns. The rust inhibitors emit 1 to 5 microns.
CNC Mist Collectors
Mist Collector Installation Options
A machine mounted mist collector is the most common type of installation. The mist collector is installed right on to the machine that is generating the mist.
Ducted Single Machine Center
Ducted Group Systems
Ambient Mist Filtration System
Indoors vs Outdoors
Typically mist collectors are installed indoors. However, if you are considering installing it outdoors you should factor in some variables such as:
Mist Collection Hooding Designs
There are some mist-collectors that require a hood. The design of the hood is important and depends on application it is being use for in order to properly filter the mist.
Mist Collector Media Filters
HEPA & DOP Filters
A HEPA filter is commonly used as the final filter. HEPA is an acronym for High Efficiency Particle Air and is 99.97% @ 0.3 micron particle size (EPA Source).
95% DOP Filter is also used as a final filter. DOP stands for Dioctyl Phthalate. It is 95% efficient @ 0.3 microns. Larger particles can be more than 99% effective.
Both of these filters are very efficient and are the standard filters used to meet federal, state, local, corporate and union air standards. You can check out our complete line of filters here.
AGET's dust & mist collectors are designed to run continuously with infrequent shutdowns for filter reconditioning and routine maintenance.
Tri-Dim Mist Collection
Tri-Dim offers a complete line of HVAC related services from simple filter changing service to mist & fume collection systems.
Clean air specialists since 1947, Trion provides indoor air quality solutions for kitchen, commercial and industrial markets.
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