An electrostatic precipitator mist collector (like the Trion Mini Mist Eliminator) has an  ionizing section to charge the incoming particles, and collector plates that are oppositely charged, to collect those particles.  When the oil mist and smoke are drawn into the unit, the collector plates act like powerful magnets, removing oil mist particles from the air.  Because there are no woven media filters to become clogged with oil, airflow can pass through the filtration elements unimpeded, maintaining a consistent capture rate.

Centrifugal oil mist eliminators work by using a high-speed spinning drum that tosses heavy oil droplets into an outer collection chamber that employs hoses to drain the oil back to the machine.  A centrifugal separator is effective on metalworking fluids only.  A high quality HEPA after-filter is required to collect fine oil mist and smoke.

Drawbacks of Centrifugal Mist Eliminators:

• Drum spinning at high speeds (3,400 RPM) cause dramatic vibration and noise
• Media filter replacements are costly
• Centrifugal mist eliminators require an electrician to handle power and controls
• Mounting hardware is always required
• Due to constant vibration, many expensive part replacements are required for items like motor mounts, drums, drum pads, flange adaptors and stands
• Demands an exhaustive maintenance schedule

Benefits of the Electrostatic Mini Mist Eliminator:

• Electrostatic collector plates are easily washed off, eliminating expensive filter replacements
• Quiet and unobtrusive – performance without interference in your production process
• No electrician needed for set-up; unit simply plugs into a standard outlet
• Easy installation – the Mini M.E. easily bolts onto your machine
• Helps save you $$$ – the Mini M.E. is very energy efficient and virtually maintenance free

A few months ago, I received a call from a prominent automobile steering column manufacturer in regard to a machining process that was spraying enough oil-based mist to pose a potential health hazard to the machine operator as well as contaminate the surrounding areas. As we were discussing the application over the phone, it seemed as if it was going to take quite a bit of airflow to address this issue.

This application was taking place in a semi-enclosure, meaning that there were fixed openings all over the enclosure…the bottom and top were totally open, and there was an access window for the machine tool operator. I began to size for the fixed openings (100 cfm per sq. ft. of opening), but based on my experience with mist collection, this just seemed like far too much airflow for the amount of coolant overspray.  Fully enclosing the process is ideal for mist collection.  If not possible, the next option is using ducted source capture hoods.

Do you have a similar coolant mist problem?

Though it is contrary to our regular practice, I set up an on-site inspection since I happened to be passing through that area anyway. Generally on-site inspections are unnecessary.  We have had a 100% success rate for specifying equipment over the phone or internet.  This practice keeps our price to the absolute minimum and saves our customers money.

Once at the location, I asked the shop foreman if he could enclose the process at all. He replied that it may be possible, but not likely.  So we moved on to considering ducting the equipment. We don’t have to enclose this process if ducting capture hoods is feasible within the area. I asked him if he’d like to save some money by fabricating his own capture hoods and performing a slight modification to the semi-enclosure. Since the facility had the capabilities, he was happy to make a couple of sheet metal hoods.

What we decided to do was this: He could mount the mist collector above the top opening, attach a source capture plenum (for ducting), and run (2) 6" flex hoses down into the enclosure. From there, he would attach the hoods and position the hoses directly in front of the spray nozzles. After we both agreed that this would be the optimal solution, he requested pricing information on the spot.

I called one of my colleagues, Rod Yarbrough, and asked him to fax over a copy of the price sheet for this equipment. The foreman and I shook hands, and I headed back to the office. By the time I arrived back in my office, there was a purchase order waiting for me. I called my new customer to let him know that I received the PO, and we would process the order immediately.

The next week, I received a phone call from my customer… this installation worked so well that he wanted to order another mist collector immediately!

I was very satisfied with the way that everything went off without a hitch, and that we were given the opportunity to brainstorm this application. Not only did the extra care pay off by allowing me to provide my contact with a highly effective piece of air pollution control equipment while keeping the equipment cost at a minimum, but it gave him confidence and trust in my pollution control company, and the industrial equipment we provide.

More success stories to come, as we continually strive to fit our clientele with the best service and mist collection equipment available!

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Electrostatic mist collectors are an attractive option for many machining applications, as they offer low cost and few if any replacement filters that need to be purchased on an ongoing basis. The main filter in an electrostatic mist collector is a washable electronic cell. The technology works by bringing the dirty air in through an impinger, or series of impingers, which remove 80-90% of the mist, particularly the larger droplet. Next, the air is drawn through an ionizing section, which charges the particles of remaining mist in the air.  Those charged particles will then pass through the electronic cell which carries an opposite charge, causing the particles to be collected, like paper clips to a magnet. The charged mist particles are attracted to the electronic cells where they accumulate and drip back down to be recaptured or drained away.  This process is about 95% efficient and offers a low cost, low maintenance option. Various post filter options are available, including carbon for odor control, and HEPA, if there are more stringent filtration requirements.

Most electrostatic mist collectors offer a few key benefits over other mist collection technologies: They do not experience the wear that centrifugal mist eliminators do, which reduces down time as electrostatic mist collectors only have one moving part – centrifugals need to have bushings and bearings replaced periodically and require much more preventative maintenance.  Media based mist eliminators require costly filter replacements, where as electrostatic models do not.

There are several different sizes of electrostatic mist collectors, the smallest being machine mount, and unlike other types of mist collectors, electrostatic units are virtually vibration free, which is key when machining to tight tolerances.  Centrifugal systems have far too much vibration for most machine mount applications, and would require additional expense to have the unit mounted on a stand or other custom installation options.

Media based systems are a great choice for cast metals and other dense ferrous metals, but the flaw with media based systems are that they lose airflow as their filters load, to compensate for this pressure drop, you will need to buy a larger more expensive machine. The expense does not stop there, regular and costly filter replacements are required for the equipment to function properly, failure to replace filters can cause the motor to burn out prematurely.

We like to use electrostatic mist eliminators whenever we can, as it offers the best performance and value for most applications.  We invite you to comment on this post, feel free to ask questions or add information, simply click on the link below that says "comments."

Most screw machines are very easily accommodated by a low cfm mist collector attached directly to the enclosure.  Some circumstances will deem that the mist eliminator should be ducted into a port on the machine, or a more powerful mist collector can be used to service multiple machines.

There are certain types of applications that require different filtration methods. For example, if you have extensive production hours or long cycle times, ESP may be more beneficial to use rather than replaceable media, which can increase machine downtime if the filters are constantly getting plugged and soaked.

This should be a pretty good start for this category; feel free to post comments, experiences, etc… After all, this is a blog!

Some plants may choose to exhaust their contaminants, usually if the contamination is a nuisance which permeates the air and forms a cloudy, foggy environment.  Exhaust is an effective method to rid the shop air of the visible fog, but it’s also blowing out all that precious heat and air conditioning, helping to keep that electric bill nice and hefty.  More importantly, exhausting your contaminated air is polluting the environment, ruining other people’s air as well as your own…a lose-lose situation.  Another point to bear in mind is that your workers are inhaling this contaminated air as it’s coming off of the process, where it is a lot more concentrated, therefore more dangerous to the operator.  So, exhausting the ambient air doesn’t really solve the immediate problem, only the nuisance afterthought, and there comes a time when employee safety must be embraced.

Each day, more and more machine shops are putting measures into place to clean up their shop environment, whether it is due to OSHA regulations, employee health concerns, or aesthetic cleanliness.  Whatever the reason may be, these shops are on the right track, and it’s only a matter of time before everyone realizes that this is a situation in which it’s okay to follow the crowd…