compressed air treatment

Choose the right filters for your compressed air system

Protect system components and maintain product quality

Compressed air systems contain contaminants that increase operating costs by:

  • contaminating product
  • damaging air-operated equipment
  • clogging air lines and restricting airflow to equipment

Particulate filters should be used primarily to remove rust, scale, dirt, and other solid particles one micron and larger. These operate with two stages: a first stage of coarse media collects larger particles and a second stage of finer media separates smaller particles as well as water and oil aerosols. Particulate filters are very versatile and can be used with either lubricated or non-lubricated compressors. In lubricated systems, this filter will remove oil aerosols and can be used to protect filters having finer media from heavier particulate and liquid loading. In non-lubricated systems air line filters can be used upstream of heated or heatless desiccant dryers and downstream of heatless desiccant dryers to capture desiccant fines.

Coalescing oil removal filters remove oil aerosols that contaminate end products, ruin paint jobs, and gum up air tools. In a typical 100 psig air system, 72% by weight of oil aerosols are less than five microns and 50% are below one micron. These droplets will pass right through a mechanical separator and cannot be completely removed by an air line filter. A good coalescing oil removal filter has a liquid oil removal rate of over 99.999%. Air is directed through a maze of submicronic glass fibers where the oil aerosols are coalesced into larger droplets and continuously removed.

Oil vapor adsorbers are final stage filters which adsorb oil vapor by passing the compressed air through two levels of activated carbon. They eliminate smell and taste by removing oil vapors as well as any other gaseous hydrocarbons normally adsorbed by activated carbon. They should be installed after the oil removal filter because liquid oil aerosols will prematurely saturate the activated carbon and significantly reduce adsorptive capacity.

High temperature after-filters are primarily designed as after-filters for heated desiccant dryers, but can be used wherever large amounts of solid particles are present in dry air. They can hold a large number of desiccant fines without plugging. Large dust particles settle in the bottom of the filter housing due to reduced velocity and a sharp shift in direction. Medium-size particles are collected on the surface of a layer of glass fiber cloth, while fines one micron and smaller are collected on beds of in-depth fiber glass media.

Moisture separators are important for removing bulk liquids and are typically installed after the aftercooler, where up to 80% of the total moisture is removed.

Filtered centrifugal separator

The Kaeser Filtered Centrifugal Separator uses centrifugal separation and mechanical filtration to remove bulk liquids from a compressed air system.

Particulate filter

Available in models from 20 scfm to 21,250 scfm, the Kaeser Particulate Filter removes liquid aerosols, rust, scale, dirt, and other solid particles one micron and larger.

Coalescing oil removal filter

Used within its rated design conditions, the coalescing Kaeser Oil Removal Filter eliminates the oil aerosols contained in a compressed air system. Its unique, continuously stabilized filter medium plus outer foam sleeve ensure 99.999+% efficiency for the life of the cartridge.

Oil vapor removal filter

Oil vapor removal filters are final stage filters which adsorb oil vapors and other gaseous hydrocarbons in compressed air. In Kaeser Oil Vapor Removal Filters compressed air passes through two levels of activated charcoal to remove gaseous oil contamination and related odors.

General compressed air treatment sizing considerations

Component Sizing consideration
Compressed air pressure Compressed air temperature Compressed air dew point Ambient air temperature Air quality level required at inlet
Filters Capacity increases as pressure increases Capacity does not change Capacity does not change Capacity does not change Separators: no requirement
Particulate: MAY require pre-filtration
Oil coalescing: SHOULD have pre-filtration
Oil vapor: MUST have pre-filtration
Aftercoolers Capacity does not change Capacity decreases as temperature increases Capacity decreases as temperature increases Discharge air temperature increases as ambient air temperature increases No requirement
Refrigerated dryers Capacity increases as pressure increases Capacity decreases as ambient air temperature increases Pre-filtration may be necessary to protect extended surface heat exchangers. Check with dryer manufacturer.
Heatless regenerative desiccant air dryers Capacity does not change Capacity does not change Capacity does not change Inlet air must be free of oil aerosols and particulates larger than 3 micron. (Also requires 1 micron after-filter)
Heat reactivated desiccant dryers Capacity decreases as temperature increases Capacity decreases dramatically as dew point increases Inlet air must be free of oil aerosols and particulates larger than 3 micron. (Also requires 1 micro high temp after-filter)
Membrane dryers Capacity does not change Capacity decreases as dew point increases Inlet air must be free of oil aerosols and particulates larger than 0.01 micron.
Nitrogen generators Capacity does not change Inlet air MUST be free of oil aerosols, oil vapor and particulates larger than 0.01 micron
Breathing air purifiers Should be no requirements as a breathing air purifier should include all necessary components, BUT CHECK WITH MANUFACTURER
Deliquescent dryers Capacity decreases as dew point increases No requirement
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