Compressed-air moisture (water) separators · Centrifugal bulk-liquid separators after the compressor and condensate separators in dryers, flow range, separation rate and pressure loss, working pressure, drain and housing
A moisture separator removes liquid water — and oil carried with it — from compressed air by spinning or redirecting the flow so droplets drop out into a bowl, where a drain discharges them. Settle three things before choosing one: where in the system it goes and the flow and pressure it must handle, the separation rate and pressure loss it achieves, and the drain, housing and connections that suit the installation.
Liquid-water separators for compressed air: centrifugal (cyclone) bulk-liquid separators installed after compressors or aftercoolers, and condensate separators built into refrigerated dryers. Coalescing and particulate filters, desiccant dryers, oil-water condensate treatment units and steam separators are outside this page except where compared; desiccant air dryers have their own page.
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01
Kaeser describes its KC centrifugal separators as removing condensed liquid immediately after the compressor's discharge point, for compressors that do not already have a built-in liquid separator, which improves the effectiveness of downstream dryers and filtration; they cover flow rates of 32–11,875 cfm at working pressures up to 232 psi, and can be combined with its filters and wall-mounted. [1]
Kaeser's refrigerated dryers remove moisture by cooling the compressed air and separating the condensed water; its larger dryers list generously sized plate-type heat exchangers and condensate separators for minimal pressure loss, and it states that a properly sized refrigerated dryer should provide a 40 °F (about 4 °C) pressure dew point. [2]
Editorial calculation: 32–11,875 cfm is about 0.9–336 m³/min, 232 psi is 16 bar and 1.45 psi is 0.1 bar; 40 °F is 4.4 °C. [1] [2]
Give the supplier the compressor type and whether it has a built-in separator, flow rate and its variation, working pressure, inlet temperature, location (after compressor, aftercooler or in dryer), required separation and allowable pressure loss, drain type and alarm, connection size, housing material, ambient conditions, and quantity.
02
Kaeser states that it measured the KC separator's swirl insert to ISO 12500-4, giving a separation rate up to 99%, stable over a broad output range, with pressure loss below 1.45 psi; the separators are fitted with an ECO-DRAIN 31 electronic condensate drain with test button and alarm contact, use a seawater-resistant aluminium enclosure with passivation coating on bowl-style models, are described as maintenance-free, and are offered in silicone-free variants. [1]
Quincy describes the filtration sequence as starting with a centrifugal separator that accelerates contaminants in a spinning motion so they collect at the bottom of the unit, before the air passes through a filter element; coalescing filters then handle particles below a micron, removing water, oil and aerosols but not vapours, and it cites ISO 8573-1:2010 as a leading compressed-air purity standard. [3]
Editorial calculation: a 99% separation rate passes 1% of the incoming liquid — if 10 L/h of condensate reaches the separator, about 0.1 L/h continues downstream to the dryer and filters. [1]
03
Two makers publish their centrifugal separator data against the same test method, which lets a buyer line the numbers up. Walker Filtration lists its Alpha Series water separator at 6 to 1500 SCFM capacities, 1/8 in to 3 in NPT connections, 232 psi maximum working pressure and 0.8 psig (typ.) pressure loss at rated capacity, with a normally open float-operated automatic drain valve. Walker states that the centrifugal module uses vanes and a vortex arrestor that stops re-entrainment, eliminates up to 99% bulk water, and that all its water separators are tested in compliance with ISO 12500-4:2009. [4]
Editorial calculation: 6–1500 SCFM is about 0.17–42.5 m³/min and 0.8 psi is about 0.055 bar. Both ranges top out at 232 psi (16 bar) and both claim up to 99% separation to ISO 12500-4, but the Kaeser figure is a pressure-loss ceiling (below 1.45 psi) while the Walker figure is marked (typ.) at rated capacity, so ask each supplier for the measured pressure drop at your own flow rate before comparing. [4] [1]
Drain type differs too: Kaeser fits an electronic ECO-DRAIN 31 with alarm contact, whereas Walker's listing names a float-operated automatic drain, with normally open or normally closed float drains and a manual drain offered as accessories. [1] [4]
| Published item | Kaeser KC | Walker Filtration Alpha Series |
|---|---|---|
| Flow range | 32–11,875 cfm. [1] | 6–1500 SCFM. [4] |
| Maximum working pressure | Up to 232 psi. [1] | 232 psi. [4] |
| Pressure loss | Below 1.45 psi. [1] | 0.8 psig (typ.) at rated capacity. [4] |
| Separation claim and test | Up to 99%, ISO 12500-4. [1] | Up to 99% bulk water, ISO 12500-4:2009. [4] |
| Drain | ECO-DRAIN 31 electronic drain. [1] | Float-operated automatic drain valve. [4] |
| Connections | Ask the supplier. | 1/8 in to 3 in NPT. [4] |
04
Ask each supplier for the separation rate and pressure loss with the test standard used, the flow and pressure range, the drain type and the housing material and connections. [1]
05
Kaeser's up-to-99% separation figure is a measurement of the swirl insert to ISO 12500-4; the other rows set the pressure rating, condensate removal and pipe fit. [1]
06
The values below are Kaeser KC figures except the connection row, which comes from Walker; the comparison table above sets both makers side by side. [1] [4]
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Operating Temperature | Inlet air and ambient. | °C. |
| Flow Capacity | 32–11,875 cfm. [1] | m³/min. |
| Separation Efficiency | Up to 99% (ISO 12500-4). [1] | % ; test. |
| Pressure Drop | Below 1.45 psi. [1] | bar at flow. |
| Connection Size | 1/8 in to 3 in NPT (Walker Alpha Series). [4] | Size; thread. |
| Body Material | Aluminium, passivated. [1] | Material. |
| Seal Material | Seals. | Compatibility. |
| Weight | Unit mass. | kg. |
| Dimensions (L×W×H) | Unit size. | mm. |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Location: [after compressor; aftercooler; dryer] Flow: [m³/min; cfm] Pressure: [bar; psi] Inlet temperature: [°C] Separation/Δp: [%; bar] Drain: [electronic; float; alarm] Connections/housing: [size; material] Quantity: [units]
1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.
Its website lists compressed-air water separators.
Product scope checked 2026-10-12
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Kaeser places centrifugal separators right after the compressor discharge, for compressors without a built-in separator. [1]
Kaeser lists up to 99% separation with under 1.45 psi pressure loss, measured to ISO 12500-4. [1]
Yes; Kaeser's refrigerated dryers cool the air and separate the condensed water in condensate separators. [2]
No; Quincy places the centrifugal separator first and the coalescing filter after it for sub-micron water and oil. [3]
Sources checked 2026-10-11. Kaeser's centrifugal separator and refrigerated dryer pages, Walker Filtration's Alpha Series water separator data and Quincy's filter guide are used to show what a compressed-air moisture separator specification covers; values for your order must come from the supplier's data sheet.
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