Flow control valves are a critical yet low-cost component found in many pneumatic circuits. These valves restrict the flow of air through the system, creating a one-way adjustable gate to provide velocity and motion control for cylinders and other types of actuators.

A defining characteristic of a flow control valve is that it only restricts flow in one direction, typically in the exhaust path, while allowing full flow in the other direction.

These components come in many form factors that can be installed in various points throughout a pneumatic circuit. They are most commonly found, however, installed directly into the port of a pneumatic actuator. When they are installed in the ports of an actuator, they serve two functions; tube fitting and flow control valve.

Selecting the Right Pneumatic Flow Control Valve

The main rule of thumb to remember for selecting a flow control valve is this: “When in doubt, meter out. It’s a sin to meter in.”

Flow controls perform best when they are installed as close as possible to the actuator port. If they are installed in-line with the tubing or at the directional valve's exhaust port, they do not have as much opportunity to control the exhaust flow and are simply not as effective in doing their job.

When a flow control valve is used on the compressed air side of a circuit (metering in), the controlled actuator can perform erratically due to the air pressure increasing and decreasing throughout the stroke as the air volume gets larger within the actuator. You will see this result in a cylinder moving with a jerky or jittery motion instead of a smooth extension and retraction.

Four Critical Factors When Choosing A Pneumatic Flow Control Valve

Form factor and fitting type:
• right angle body with male threads for installation into cylinder ports
• push connect secondary port for tubing
• secondary threaded port for pipe fitting or additional tube fittings

Inline configuration:
• integrated push-connect tube fittings
• threaded for installation of additional fittings

Size:
• Port Thread – first you need to determine the port size of the actuator you will be installing into.
• Tubing size – What size tubing will be used with your flow control valve.

Adjustment Type:

• Knob adjustments allow for easily accessible tool-less adjustment.
• Recessed slotted stem adjustments require a screwdriver to adjust, which can prevent unauthorized adjustments.
• Fixed orifice flow controls are non-adjustable valves which are sometimes used when controlled flow should not ever be adjusted

Flow Direction (although it’s a sin to meter in, sometimes it just can’t be done any other way):
• Meter In – controls the flow of exhausting air
• Meter Out – controls the flow of compressed inlet air

Not all pneumatic flow controls are created equal. High-quality flow controls sold by TSI Solutions allow for fine thread adjustment providing a wide range of precise control. You can shop our extensive selection of flow control valves online. If you still feel like you need assistance selecting the best valve for your application, give us a call today to speak with a pneumatic specialist at (844) 957-1690.