Your back-to-the-basics primer on filtering, lubricating, and regulating compressed air

Proper preparation of air that's leaving the compressor extends equipment life and optimizes performance

By Charles Werdehoff, IMI Norgren

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Filter/regulators combine the features of a filter and a regulator in a single compact body. Air passes through the filter section first, removing water and particles. This clean air is then regulated by the top regulator section. 


Most pneumatic equipment, even prelubricated components, will last longer if oil aerosol is continually added to the compressed air that powers them. Without lubrication, environmental factors such as extreme temperatures and excessive moisture and operational factors such as startup and operation friction reduce the service life of most working pneumatic devices. Used oil exiting the compressor is dirty and degraded, so it cannot function as a lubricant.

Aerosol lubricators automatically deliver a metered amount of oil into the air path of operating pneumatic equipment. Lubricators function by creating a pressure drop that causes oil to be siphoned into an adjustable dome. An operator can set the amount of oil to be delivered by observing the drip rate and using the dome adjustment.

Operating manuals for pneumatic equipment typically specify the amount of oil required to keep the device operating optimally. Lubricators should be adjusted to deliver the amount of oil specified at defined operating conditions and then be validated after the equipment is in operation. 

Fig 3 Micro fog lubricator

Figure 3. Micro-fog lubricator. Source: IMI Norgren

Oil-fog (also called direct-feed) lubricators are the most commonly used. These lubricators deliver 100% of the oil drops seen in the dome directly into the air stream. Oil particles traveling downstream are normally 2 microns or larger. Because of gravity, these particles will remain airborne only for a short distance – up to about 15 feet – and they normally will not travel up or follow intricate flow paths. As a result, oil-fog lubricators should be located in-line and near the tool they are lubricating. They are very efficient at delivering the right amount of oil directly to the cylinder, valve, or tool.

Micro-fog lubricators atomize the oil drip into particles smaller than 2 microns. Approximately 10% of the oil drip seen in the dome is transported into the airflow, and the rest of the oil is returned to the bowl for future use. Because the particles are small, they can travel long distances, vertically, and through intricate flow paths to multiple tools. Also, because only 10% of the oil is being delivered downstream, micro-fog lubricators are good for applications that require better adjustability of small amounts of direct lubrication. (Figure 3) 


A lubricator is used downstream from a filter and regulator that precondition the air. These can be stand-alone components or an integrated filter/regulator/lubricator (FRL). In many applications, a space-saving FRL combination will reduce installation complexity and cost and make maintenance easier. FRLs can be composed of filters with different filtration levels and with oil-fog or micro-fog lubricators. 

Pneumatic devices that push, pull, lift, position, or convey last longer and perform better when powered by compressed air that is clean, dry, pressure-regulated, and lubricated.

Charles Werdehoff is FRL product marketing manager for the Americas at IMI Norgren, where he has worked for more 35 years. In addition to air preparation experience, Werdehoff has extensive manufacturing experience. Contact him at

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