Air Pressure Regulators
Filters
ARO-Flo Compressed Air Regulators: Relieving and Non-Relieving
Plant air arrives at whatever pressure the compressor delivers, and that pressure rises and falls with demand. An air pressure regulator turns it into a steady, set pressure for the equipment downstream. Too little and tools and cylinders lose force, too much and parts wear faster and air is wasted. Also called a compressed air pressure reducer or compressed air regulator valve, it balances a control spring against a diaphragm to open and close an internal valve, holding the outlet at your setting as demand changes.
Every ARO regulator on this page belongs to the ARO-Flo line: 40 models across four series, from 1/8" to 1" NPT, in relieving and non-relieving designs, with 0-30, 0-60 and 0-140 psi ranges and the option of a built-in gauge.
Relieving or Non-Relieving Regulator?
The difference shows when you turn the pressure setting down, or when something downstream pushes pressure above the setting.
| Type | When pressure needs to come down | Choose it for | On this page |
|---|---|---|---|
Vents the excess air from the downstream side, so the line drops to the new setting straight away |
Most applications, and anywhere the pressure is adjusted often |
29 models, 1/8" to 1" |
|
Does not vent. Downstream pressure only falls as the equipment uses air |
Applications where venting downstream overpressure is undesirable |
11 models, 1/8" to 1" |
Pressure Range and Gauge
The range is set by the regulator's control spring. The last three digits of the part number show the range, the gauge and the relief type.
- 0-140 psi, with gauge Part numbers ending -600 (relieving) or -620 (non-relieving). A flush-mount gauge with settable pointers marks the working range, so anyone can see at a glance when the pressure is out of limits.
- 0-140 psi, no gauge Part numbers ending -100 or -120. A 1/8" gauge port is standard if you want to add a gauge later.
- 0-60 psi Part numbers ending -200 (relieving) or -220 (non-relieving), for lower-pressure equipment where finer adjustment helps.
- 0-30 psi Part numbers ending -400 (relieving) or -420 (non-relieving), for low-pressure applications.
Reading an ARO-Flo regulator part number
In R37341-620, 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"). So R37341-620 is a 2000 Series 1/2" non-relieving regulator, 0-140 psi, with gauge.
Flow Ratings by Series
Size the regulator by the air flow the equipment draws, not only by the pipe thread. Ratings are at 100 psi inlet and 90 psi set pressure.
| Series | Port | Rated flow | Part numbers |
|---|---|---|---|
ARO-Flo 1000 |
1/8" |
45 SCFM |
R37111-xxx |
ARO-Flo 1000 |
1/4" |
59 SCFM |
R37121-xxx |
ARO-Flo 1500 |
1/4" |
86 SCFM |
R37221-xxx |
ARO-Flo 1500 |
3/8" |
113 SCFM |
R37231-xxx |
ARO-Flo 2000 |
3/8" |
179 SCFM |
R37331-xxx |
ARO-Flo 2000 |
1/2" and 3/4" |
210 SCFM |
R37341-xxx, R37351-xxx |
ARO-Flo 3000 |
3/4" and 1" |
290 SCFM |
R37451-xxx, R37461-xxx |
Tested against the competition
In ARO's head-to-head test at 100 psi inlet and 90 psi set pressure, the smallest 1/4" ARO-Flo regulator, the 1000 Series R37121-620, flowed 59 cfm, on average 38 percent more than four competing 1/4" regulators. More flow through the regulator means less pressure lost before the air reaches the tool.
Choosing a Pressure Regulator for Air Compressor Systems
Many compressors come with an air compressor air pressure regulator at the tank outlet, but that single setting feeds everything connected downstream. Fitting an air regulator for air compressor lines at each point of use lets every tool, cylinder or machine run at the pressure it needs, however the tank pressure rises and falls. When choosing an air compressor pressure regulator for this job, check four things.
- Inlet pressure Every ARO-Flo model accepts up to 250 psi at the inlet. Make sure the compressor's maximum tank pressure stays below that.
- Flow Size by the air the equipment downstream consumes, using the ratings above. A regulator with too little flow capacity drops pressure at the tool, even when the compressor keeps up.
- Port size Match the regulator to the air line, from 1/8" to 1" NPT.
- Air quality Air leaving the compressor carries water and dirt, so fit a filter ahead of the regulator to protect its valve and diaphragm.
Built for Daily Adjustment
- Pull the knob to adjust, turn clockwise to raise pressure, and push down to lock the setting
- A panel nut is standard on every individual regulator for mounting through a control panel
- Mounts with the knob up or down to suit the installation
- An optional tamper-resistant kit locks in a specific pressure
- Aluminum body, steel control springs and nitrile seals, rated from 23°F to 140°F
- Covered by a 24-month warranty against defects in material and workmanship
Installing a Regulator
- Position After the filter and before the lubricator, as close as possible to the equipment, with air flowing in the direction of the arrow.
- Piping Match the air line to the regulator's port size, and use thread sealant on male threads only so none enters the regulator.
- First start-up Before turning the air on, turn the knob counterclockwise until the spring is released. Then raise the pressure gradually, so the equipment is never over-pressurized.
Frequently Asked Questions
How do I lower the pressure on a non-relieving regulator?
A non-relieving regulator does not vent air from the downstream side, so turning the knob down alone will not lower the line pressure. ARO's procedure is to turn the setting below the pressure you want, release air downstream by opening or operating the equipment, then turn the setting back up to the target. On a relieving regulator, the excess air vents and the line settles at the new setting by itself.
Which pressure range should I order?
Choose the lowest range that covers your working pressure with some margin. 0-140 psi is the standard range and suits most plant equipment. 0-60 psi and 0-30 psi models spread the knob's travel over fewer psi, which makes small adjustments easier on low-pressure equipment. ARO advises against setting a regulator outside its specified spring range.
Do ARO-Flo regulators come with a pressure gauge?
Models ending in -600 (relieving) and -620 (non-relieving) have a flush-mount gauge reading 0 to 140 psi, with adjustable pointers to mark the upper and lower limits of the working range. All other models have a 1/8" gauge port, so a separate gauge can be fitted if needed. On this page, 14 of the 40 regulators come with a gauge.
Where should a regulator go in the air line?
After the filter and before the lubricator, as close as possible to the equipment it supplies, with air flowing in the direction of the arrow on the body. If the line carries water or dirt, the filter upstream protects the regulator's valve and diaphragm. The regulator can be mounted with the knob up or down.
Can I use an ARO regulator with my air compressor?
Yes. Any ARO-Flo model can serve as the air pressure regulator for air compressor systems, from a single shop compressor to a plant air network. Install it downstream of the compressor tank, after a filter and as close as possible to the equipment. Check that the compressor's maximum tank pressure stays below the regulator's 250 psi inlet rating, and choose a series whose rated flow covers what the equipment draws.
How much air can an ARO-Flo regulator flow?
Rated flow at 100 psi inlet and 90 psi set pressure runs from 45 SCFM for the 1/8" 1000 Series to 290 SCFM for the 3/4" and 1" 3000 Series. In ARO's comparison testing, the 1/4" 1000 Series R37121-620 flowed 59 cfm, on average 38 percent more than four competing 1/4" regulators tested under the same conditions.
Steady Pressure, Every Shift
A correctly sized air pressure regulator does more than set a number on a gauge. It keeps tools, cylinders and valves working the same way at the start of a shift as at peak demand, and avoids the wear and air waste of running everything at full line pressure.
Order the regulators above, and put a compressed air filter in front of each one. Add an air line lubricator where the equipment needs oil, or choose a piggyback filter regulator or FRL combination unit to get everything in one assembly. For cylinder speed control after the regulator, see the needle and flow control valves. Regulators chosen for specific applications are on the industry pages for car wash, packaging and general manufacturing.
Need help choosing a compressed air regulator?
Talk to ARO about flow, pressure range or relieving and non-relieving designs. Monday to Friday, 08:00 am to 5:00 pm CST.