Mist Collector

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:

Table Of Contents

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?

Another byproduct of machining and oil-based coolant is smoke. Not the traditional smoke that you get with fire, but a nasty oil laden smoke that is lighter and travels further than mist alone. In our world smoke is treated as another form of mist. Smoke particulate measures 1 micron or less which makes for a very light and well traveled contaminant.

So if the particle sizes are undetectable by the human eye why can we see them? The initial concentrations of the particulate are so dense and slow moving that you can see them until the cloud dissipates. Additionally, the oil is reflective, capturing light and intensifying the appearance of the cloud.

What is Oil Mist?

Manufacturing operations for metal working require lubrication and a coolant to reduce friction and deterioration on expensive machinery. There are several variations of coolants and lubricants, and they all contain various minerals, contaminants and oil. These additives are necessary to protect the metal all while ensuring other unwarranted actions do not happen.

Machinery that requires the aforementioned fluids move very fast, which causes an oil mist that is dispelled into its current environment. The fluids also cause smoke.

The oil mist and smoke that is expelled during the operation of the machine reduces the lifetime of all machines in the area. Different machines produce different oil mists. Combining this with the regulation factor and current structure of the building, there isn’t one simple answer to say which oil mist collector is best for your operation. However, it is a necessary investment that will be returned.

What is a Mist Collector?

There are (3) acceptable methods of mist collection. Understanding how each mist collector functions will help determine which one is best for you.

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.

Centrifugal Separators

Centrifugal Separators utilize centrifugal force to separate the mist from an airstream. The contaminated air is drawn into the separator and introduced to a fast moving blade or cage. Once the mist has coalesced it is forced to the exterior walls of the housing pushed to a drain point.

Initial maintenance of this system is simple and infrequent but does increase over time. Centrifugal separators are an excellent choice for oil based coolant mists. This system will not capture smoke.

These (3) styles of collection offer a variety of designs with varying levels of efficiency. It is important that you choose a collector based on your application, byproduct and loading. This criteria will dictate the style and configuration of the collector you require.

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

Source Capture

Anyone with any sense will tell you that source capture should always be your first choice. This allows you to capture the mist at the source, before it has had a chance to contaminate any other spaces.

Equipment can be unit mounted, remote mounted, hooded or tapped directly into the machine allowing collection to take place where the mist is originated. Source capture allows you to accomplish more with less and should be used anytime that it is feasible.

Ambient Capture

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

A mist collector is used to save you money. Seriously, it has several important tasks that result in a significant return on investment.

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.

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

There are many industrial machines that generate mist. Once you understand what type of machine you’re working with, how much mist and at what size particles it produces then you’ll be able to get a better idea of what is the best mist collector for your application.

Metal Cutting Operations

Mills

Mills are typically used for drilling operations, such as boring, hobbing and honing. Mills use oil lubricants or water-soluble coolants that produce a mist 20 microns or less.

Turning

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

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.

Casting

When pouring molten metal into a die mold a lot of steam and fumes are generated. The fumes are necessary to control. The steam creates a lubricant that is half water and half paraffin wax. This steam becomes sludge like. Therefore, several filters are necessary for mist collecting metal casting. The water-soluble with wax is 2 to 50 microns. The metal fumes are much finer and less than 1 micron.

Heat Treating

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

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.

Part Washing

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

CNC machining is a very common application requiring mist collection. CNC machines are used for a variety of metal cutting operations including mills, drills, grinding, lathes, plasma cutters, wet jet cutters and more.

Additionally, because they are so versatile they are available in a variety of cabinet sizes and designs ranging from totally open to totally enclosed. One common factor across all of designs is that they are using some form of coolant and require mist extraction.

The most common is a totally enclosed machine that bellows out a plume of mist and smoke when the main access door is opened. The mist collector selection considers the type of CNC machine being used, the style and speed of the cutting head, the type of oil or coolant the machine is using and the size of the machine and the open spaces.

Knowing these details provides the information necessary to select a successful CNC mist collector.

Mist Collector Installation Options

Machine-Mounted Systems

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

The mist collector can be mounted on the floor, mounted on to another object such as a wall or beam, or hung from the ceiling.

Ducted Group Systems

Ducted Group Systems are a practical mist collection solution if there are several machines in a group or cell. A larger collector can service multiple machines utilizing the same type of coolant.

Ambient Mist Filtration System

When a plant, factory, warehouse, or any type of facility that produces mist that cannot be directly collected, an ambient mist filtration system is used. They are commonly used in combination with another mist filtration system to further purify the indoor air quality. They are a viable option when trying to meet federal, state or union air quality standards.

Installation Methods

When choosing a mist collector that best suits your needs, you should evaluate all factors to determine which system and technology to use.

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.

Hood Sizes

The hood size of the mist collector requires calculations by a skilled professional in order to collect as much mist as possible in an efficient manner.

Mist Collector Media Filters

Synthetic Filers

A commonly used material in media based mist collection is polyester. Polyester provides the most bang for the buck. Providing a moderate collection efficiency rate, high loading capacity with good drainage properties at a very reasonable cost. Another commonly used material in media based mist collection is fiberglass. Providing a high collection efficiency rate, moderate loading capacity and moderate drainage properties at a very reasonable cost. An upgraded synthetic media based filter option is a combination of polyester and fiberglass. This combination provides the best of both worlds offering high collection efficiency rates, high loading capacity and good drainage. These filters carry a higher cost than the other options but are well worth the investment.

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.

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