Two of the primary methods of removing oil mist and smoke from machine tools with mist eliminators are electrostatic precipitators (ESP) and centrifugal separators.  Although these 2 types are both designed for oil mist collection, the technologies employed are vastly different.

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

The major mist collector technologies are; electrostatic, media and centrifugal. A mist collector expert will know when to use a specific mist collector technology and what technologies to avoid for specific applications; for example, we usually will not use electrostatic mist collectors on machines that are machining cast iron - this is because the very fine ferrous dust gets into all parts of the machine and will eventually cause arcing and/or other electrical malfunctions.
 

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."