Compressed Air Filters
Filters
ARO-Flo Compressed Air Filters: Particulate and Coalescing
Compressed air leaves the compressor carrying water, oil and dirt, and the piping adds rust and scale on the way. An air filter for compressed air sits in the air line, not on the compressor intake, and takes those solid and liquid contaminants out before they reach valves, cylinders and air tools. This page carries 52 ARO filters across the four ARO-Flo series, with NPT ports from 1/8" to 1": 5 micron particulate filters for general protection and 0.3 micron coalescing filters for removing oil aerosols, with polycarbonate or metal bowls and manual or automatic drains.
Compressed Air Filter Types: Particulate or Coalescing
The two types do different jobs, and many air lines need both. The particulate filter always comes first.
| Filter type | What it removes | Where it goes | On this page |
|---|---|---|---|
Solid particles and liquid water, with a 5 micron element |
First stage at each point of use, ahead of the regulator and lubricator |
35 filters, 1/8" to 1", all four series |
|
Oil aerosols and fine particles down to 0.3 microns |
Directly after a 5 micron particulate filter, where oil carryover would cause problems |
17 filters, 1/4" to 1", all four series |
Protect the coalescing element
ARO recommends a 5 micron general-purpose filter upstream of every coalescing filter. It stops dirt and bulk water from loading up the fine coalescing element, which keeps its pressure drop low and its service life long.
Size by Flow: Four ARO-Flo Series
When selecting filters for compressed air systems, pick the series by the air your equipment uses in SCFM, not by the pipe thread alone. Air line piping should then match the filter's port size. Ratings below are at 90 psi inlet pressure with a 10 psi pressure drop.
ARO-Flo 1000
1/8" and 1/4" ports
38 SCFM at 1/8", 49 SCFM at 1/4"
Miniature size for single tools and small valves
ARO-Flo 1500
1/4" and 3/8" ports
73 SCFM at 1/4", 107 SCFM at 3/8"
Compact size for branch lines and individual machines
ARO-Flo 2000
3/8", 1/2" and 3/4" ports
156 SCFM at 3/8", 197 SCFM at 1/2", 216 SCFM at 3/4"
Standard size for groups of equipment
ARO-Flo 3000
3/4" and 1" ports
288 SCFM at 3/4", 353 SCFM at 1"
Heavy-duty size, metal bowls only
Choose the Bowl and Drain
The bowl collects the liquid the filter removes. Its material sets the pressure and temperature limits, and the drain decides who empties it.
- Polycarbonate bowl Transparent, with a protective guard, so the liquid level is easy to see. Rated to 150 psi and 23°F to 125°F. Available in the 1000, 1500 and 2000 Series.
- Metal bowl Rated to 250 psi and 23°F to 175°F. The bowl to choose for a high pressure compressed air filter, and wherever polycarbonate could meet incompatible substances.
- Metal bowl with sight glass The metal bowl ratings, plus a window to check the liquid level. Install it facing the operator.
- Manual drain Open the drain often enough to keep liquid below the baffle. If it rises higher, liquid can be carried downstream.
- Automatic drain Empties collected liquid without an operator. The 1/8" NPT drain connection takes flexible tubing of at least 1/8" inside diameter, and the drain can still be operated by hand by pressing the needle inside the outlet.
Polycarbonate and chemicals
Polycarbonate bowls must not be exposed to synthetic oils, compressor oils with ester-based additives, solvents, ketones, thinners, certain alcohols, paints or their fumes. Where any of these could be present, choose a metal bowl.
Reading an ARO-Flo filter part number
In F35342-311, the fourth digit is the series (1 = 1000, 2 = 1500, 3 = 2000, 4 = 3000) and the fifth is the port size (1 = 1/8" up to 6 = 1"). After the dash: the element (3 = 0.3 micron coalescing, 4 = 5 micron), the bowl (0 = polycarbonate with guard, 1 = metal with sight glass, 2 = metal) and the drain (0 = manual, 1 = automatic). So F35342-311 is a 2000 Series 1/2" coalescing filter with a sight glass metal bowl and automatic drain.
Installation and Maintenance
ARO's maintenance instructions for ARO-Flo filters come down to a few rules:
- Install the filter as close as possible to the equipment it protects, with the bowl pointing down
- Follow the flow arrow on the body, and place the filter upstream of the regulator and lubricator
- As a main line filter, install it as close as possible to the air supply
- Replace the element when the pressure drop reaches 10 psi
- Wash bowls only with soap and warm water
- Depressurize before servicing. The locking bowls are designed to resist removal under pressure
Frequently Asked Questions
What micron rating do I need for a compressed air filter?
For general protection of tools, valves and cylinders, a 5 micron particulate filter is the standard choice, and it is what ARO-Flo filters ship with. Where oil aerosols would cause problems, add a 0.3 micron coalescing filter after the 5 micron stage. ARO also offers 40 micron elements as a separate purchase for coarser filtration. On this page, 35 filters are 5 micron particulate and 17 are 0.3 micron coalescing.
When should I replace the filter element?
ARO's maintenance instructions say to replace the element when the pressure drop across the filter reaches 10 psi, or when the optional service life indicator shows about half red and half green. If a clean element still shows a high pressure drop, the filter is probably running above its rated flow and a larger size is needed. Always depressurize the unit before removing the bowl.
Should I choose a polycarbonate or a metal filter bowl?
A polycarbonate bowl with guard lets you see the liquid level and is rated to 150 psi and 23°F to 125°F. A metal bowl is rated to 250 psi and 23°F to 175°F, and is the right choice where polycarbonate could meet incompatible substances, such as synthetic oils, compressor oils with ester-based additives or solvents. Metal bowls with a sight glass give the higher ratings and still show the liquid level.
Why does a coalescing filter need a particulate filter in front of it?
A coalescing element is designed to capture very fine oil aerosols, down to 0.3 microns. If dirt and bulk water reach it first, it loads up quickly and its pressure drop rises. ARO recommends installing a 5 micron general-purpose filter upstream of every coalescing filter for maximum element life and efficiency.
How much air can an ARO-Flo filter handle?
Rated flow depends on the series and port size: 38 to 49 SCFM in the 1000 Series, 73 to 107 SCFM in the 1500 Series, 156 to 216 SCFM in the 2000 Series and 288 to 353 SCFM in the 3000 Series, at 90 psi inlet pressure with a 10 psi drop. Choose a filter whose rating covers the air the equipment downstream actually uses, with some margin.
Clean Air Starts Here
Every other component in the air line depends on the filter in front of it. Regulators hold pressure more reliably, lubricators meter oil more evenly, and valves and cylinders last longer when the air reaching them is clean and dry.
Order the ARO filters above, and complete the line with ARO-Flo air pressure regulators and air line lubricators. To save space, a piggyback filter regulator combines the filter and regulator in one body, and FRL combination units come pre-assembled. Filters selected for specific applications are also on the industry pages for car wash, food & beverage, packaging and general manufacturing.
Need help choosing a filter?
Talk to ARO about flow, filtration level or bowl selection. Monday to Friday, 08:00 am to 5:00 pm CST.