One-Way Flow Control: Meter-Out vs Meter-In

How does a one-way flow control valve work?

The valve combines an adjustable restrictor with a check valve. In one flow direction the air is throttled, in the opposite direction it passes freely through the check valve. So it limits speed in one direction only, without blocking full flow on the return stroke. For a double-acting cylinder you usually fit two valves, one at each cylinder port.

Why is meter-out usually the right choice?

With meter-out control the air leaving the cylinder is throttled while the inlet air flows in freely. This builds a back pressure on the exhaust side that acts as an air cushion and guides the piston smoothly. It prevents the dreaded lurching (stick-slip) and gives even motion even under changing loads. For almost all double-acting cylinders this is the standard solution.

Meter-in control instead limits the incoming air. The cylinder starts hesitantly and tends to jump under load because no stabilising air cushion forms. Meter-in makes sense almost only with single-acting cylinders, very small volumes or when a defined slow start is required.

How do I select and mount the valve correctly?

The one-way flow control valve sits best directly at the cylinder port, often as a push-in fitting. That keeps the air volume between restrictor and piston small so control stays precise. Port size follows the cylinder bore and tube diameter. Set both valves of a cylinder separately so extend and retract each get the right speed.

• Mount the valve directly at the cylinder, not at the directional valve.
• Check the metering direction: for meter-out the valve throttles the cylinder exhaust.
• Open the needle slowly until the target speed is reached, then lock it.
• Adjust both stroke directions independently.
• With oil-mist lubrication choose media-resistant seals.

Frequently asked questions