Pneumatic Needle & Flow Control Valves
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Pneumatic Needle Valves, Flow Control Valves and Check Valves
Needle valves, flow control valves and check valves decide how fast things move in a pneumatic system and which way the air is allowed to go. This page carries the full ARO In-Line Composite range, part numbers 104104, in three valve types: the pneumatic needle valve to meter air precisely, the compressed air flow control valve to set the speed of air cylinders, and the check valve to stop air flowing back. All 15 valves fit straight into the air line, with NPT ports from 1/8" to 3/4", flow ratings from 18 to 100 SCFM and a 200 psi maximum inlet pressure.
Needle Valve, Flow Control Valve or Check Valve?
The three types look alike but control air in different ways. A flow control valve is sometimes called an air flow regulator valve, but it sets how much air passes, not the pressure; that is the job of a regulator. Choose the type by what the air needs to do, then the size by the flow it has to pass.
| Valve type | How it controls air | Typical use | On this page |
|---|---|---|---|
An adjustable restriction that increases or decreases airflow in both directions |
Metering a small, steady flow, such as the air that sets the speed of a diaphragm pump |
1/8" to 3/4", plus a 1/4" version with stainless steel needle and inserts |
|
Adjustable flow in one direction and free flow in the other, like a needle valve with a built-in check valve |
Setting the extend and retract speed of pneumatic cylinders and actuators |
1/8" to 3/4" |
|
Lets air through in one direction and blocks it from flowing back |
Holding downstream pressure and preventing backflow toward the supply |
1/8" to 1/2" |
Sizes and Flow Ratings
At each port size, all three valve types carry the same flow rating, so valves on one machine can be sized the same way. Pick the size whose SCFM rating covers the air the cylinder, tool or pump downstream actually draws, not just the size that matches the pipe thread.
| Port (NPT) | Max flow | Needle valve | Flow control valve | Check valve |
|---|---|---|---|---|
1/8" |
18 SCFM |
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1/4" |
28 SCFM |
104104-N02 |
||
3/8" |
58 SCFM |
|||
1/2" |
90 SCFM |
|||
3/4" |
100 SCFM |
Not offered |
Built for Repeatable Settings
For air flow valve control on a production line, the hard part is rarely setting the flow once. It is getting exactly the same setting back after maintenance or a changeover, and making sure nobody moves it in between. The needle and flow control valves are designed around that.
- A four-stage tapered needle gives infinite adjustment across the range rather than fixed steps
- A color-coded micrometer and calibrated adjustment knob give reference points, so a setting can be recorded and repeated
- A red locking ring holds the setting once it is made, and tamper-resistant wire is supplied in the package
- Threaded bodies allow remote panel mounting, putting the adjustment where operators can reach it
- Composite bodies on every valve are lightweight, tough and corrosion resistant
- The 104104-NS2 uses a stainless steel needle and inserts, with the same 28 SCFM and 200 psi ratings as the standard 1/4" valve
Controlling Pneumatic Cylinder Speed
Flow control valves are most often used to set how fast a pneumatic cylinder extends and retracts. Because each adjustable flow control valve throttles air in one direction and lets it pass freely in the other, one valve per cylinder port gives independent control of each stroke. On double-acting cylinders, the usual arrangement is meter-out: the valve restricts the air leaving the cylinder, so the piston moves against a cushion of exhaust air and runs more smoothly than when the incoming air is throttled.
Set the pressure first, then the speed
Cylinder speed also depends on supply pressure. Set and lock the pressure at the regulator before adjusting the flow control valves, so a later pressure change does not undo the speed setting.
Needle Valves and Check Valves for Diaphragm Pumps
The same valves are used on the air side of air operated double diaphragm pumps, where the air supply sets how fast the pump cycles.
- Speed control Needle valve flow control is a common way to set the air supplied to a diaphragm pump, and with it the pump's speed. ARO lists the 1/4" air needle valve 104104-N02 and its stainless needle version 104104-NS2 for all its 1/4" to 1" diaphragm pumps.
- Flooded inlet When a 1/2" ARO pump is fed from a flooded (forced-feed) inlet, ARO's pump manuals recommend a check valve at the pump's air inlet.
- Clean air first Fit the valve in the line after the filter and regulator. ARO's 1/2" pump manuals call for air filtered to remove particles larger than 50 microns, which a 5 micron piggyback filter regulator covers in one unit.
Frequently Asked Questions
What is the difference between a needle valve and a flow control valve?
A needle valve is an adjustable restriction: turning the knob increases or decreases airflow through the valve in both directions. A flow control valve adds a check function, so it throttles air in one direction and lets it flow freely in the other. That makes the flow control valve the usual choice for setting cylinder speed, and the needle valve the usual choice for metering a steady flow, for example the air feeding a diaphragm pump. Both types are available here from 1/8" to 3/4" NPT.
How do I control the speed of a pneumatic cylinder?
Fit a flow control valve in each cylinder port so that it restricts the air leaving the cylinder, an arrangement known as meter-out, then adjust each valve to set the extend and retract speeds independently. Set the supply pressure at the regulator first, because a later pressure change also changes the speed. Once the speed is right, the red locking ring holds the setting.
Can I use a needle valve to control an air operated diaphragm pump?
Yes. Throttling the air supply to an air operated double diaphragm pump slows its cycle rate and reduces the flow it delivers. ARO lists the 1/4" needle valves 104104-N02 and 104104-NS2 for all its 1/4" to 1" diaphragm pumps. The pump's air should also be filtered: ARO's 1/2" pump manuals call for a filter that removes particles larger than 50 microns.
What does a check valve do in a compressed air line?
A check valve lets air pass in one direction and closes against flow in the other. It holds pressure downstream when the supply drops and stops air flowing back toward the source. ARO also recommends a check valve at the air inlet of its 1/2" diaphragm pumps when they run with a flooded inlet. The In-Line Composite check valves here run from 1/8" (18 SCFM) to 1/2" (90 SCFM).
What pressure and flow can these valves handle?
Every valve on this page is rated for a maximum inlet pressure of 200 psi. Flow depends on the port size, not on the valve type: 18 SCFM at 1/8", 28 SCFM at 1/4", 58 SCFM at 3/8", 90 SCFM at 1/2" and 100 SCFM at 3/4". Choose a size whose rating covers the air drawn by the cylinder, tool or pump downstream.
Are these high pressure needle valves?
They are built for compressed air, with a maximum inlet pressure of 200 psi on every valve, which is above the pressure most plant air systems run at. They are not high pressure needle valves in the hydraulic or instrumentation sense, where ratings run into the thousands of psi. The stainless steel 104104-NS2 carries the same 200 psi rating as the standard valves, so if your application needs a high pressure needle valve above 200 psi, choose a valve rated for that service instead.
Complete the Air Line
Needle, flow control and check valves fine-tune air that has already been cleaned and set to pressure. They work best at the end of a properly sized air preparation line, where every valve sees steady, filtered air.
Order the valves above, and browse the ARO-Flo filters, regulators, piggyback filter regulators and FRL combination units that go upstream of them. For pump installations, see the diaphragm pumps and pump parts and kits. Industry selections for general manufacturing, packaging and car wash include these valves too.
Need help sizing a valve?
Talk to ARO about flow ratings, cylinder speed control or pump air supply. Monday to Friday, 08:00 am to 5:00 pm CST.