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Mist collection is the process of collecting mist and vapors that are produced in machine tooling during a process where coolant (either soluble or neat oil) is being applied to the material being machined. During the machining process, mist is created as the coolant is being applied to keep the part cool and/or lubricated.
This mist that is created can be captured by a unit called a mist collector. The purpose of a mist collector is to create an air pattern inside the machine tool to help draw the mist out of the cabin so when the door is opened (or during the machining process), the mist does not escape onto the operator or into the air and/or shop area.


A motor rotates an internal drum at a high constant speed, creating a vacuum which draws mist particles into the center of the drum. The mist particles then collide with the rotating drum’s vanes and are forced together with other particles, causing them to coalesce and form larger, droplet-sized particles. As the particles grow into droplets, they pass through the perforations in the rotating drum and centrifugal force causes them to be thrown onto the inner wall of the housing. The particles are then forced, under pressure, up the walls of the housing to the oil return channel, where they are subsequently drained back to the machine’s coolant tank. Clean, oil-free air blows past the motor and is returned to the shop.


  • Lathes (single and multi-spindle)
  • Sharpeners and grinders which are equipped with cabin protection enclosures
  • CNC machine tools
  • Grinding machinery
  • Turning machinery
  • Milling machines
  • Drilling operations
  • Complex machining centers


  • Provides a cleaner work environment for maximum productivity
  • Reduces risk of mist related hazards
  • Stops employees from breathing in harmful mist (less potential illnesses and health claims)
  • Lower plant maintenance costs
  • Cleaner plant and equipment
  • Prevents mist from settling on shop floors which prevents slip and falls
  • OSHA requirements for cleaner shop environment
  • Cost savings on replacing polluted coolant
  • Cleaner coolant allows for longer tool life
  • General employee satisfaction with their working environment


Mist collectors can be installed in either a horizontal or vertical orientation, depending on the space available. They can also be installed either directly on the machine tool enclosure or in the immediate proximity of the machine tool by means of the appropriate support frame (wall or floor bracket). The extreme versatility of these filters means they can easily be mounted on the machine tool in any situation. On turning machines (single and multi-spindle) it is important that the suction pipe of the air filter is placed far from the spindle and from areas where there is strong presence of metal swarfs, solid particulate, and cooling fluids. This is to avoid deposits of particles inside the centrifuge. For machines located in close proximity to one another, one filter unit can be piped to filter more than one machine at a time. Their easy installation allows them to be moved from machine to machine to meet filtration demand.


It is recommended that you contact your appropriate Flodraulic or RHM contact person for specific sizing information as sizing can differ from application to application. However, as a general rule of thumb, the following formula can be used to obtain a rough idea of mist collector size:
  • Filter Size (cfm) = Internal Enclosure Volume (cu.ft.) x 5
  • Example: Machine envelope measuring 5 feet wide x 3 feet deep x 5 feet high. Multiplying 5’ x 3’ x 5’ gives you an enclosure volume of 75 cubic feet. Multiplying 75 cu.ft. x 5 tells you roughly that a 375 cfm (cubic feet per minute) mist collector will be required.


One of the main attractions of the mist collector, besides a cleaner environment, is its lack of required maintenance. The only part of a mist collector that requires regular field maintenance are the specially designed drum pads. Drum pads are quick and easy filter changes that the workers have minimal contact with. Life span of drum pads depends upon machine hours and duty cycles and it can be predicted with a differential pressure gauge


Mist collectors are becoming more and more common in today’s working environment, especially by those companies that are striving for a more “green work place”. Some OSHA regulations require mist collection to meet their guidelines. Mist collectors can be added to any machining process where coolant is being used in the tooling process. These units are easily installed and can be moved easily from one machine to another, as needed. Mist collectors add great value and a more comfortable working environment to any machine tool facility, no matter its size.

Note: “Tech Tips” offered by Flodraulic Group or its companies are presented as a convenience to those who may wish to use them and are not presented as an alternative to formal fluid power education or professional system design assistance.

Experts in fluid power, electrical and mechanical technologies.