Flow Control (Speed Control) Valves

In hydraulics and pneumatics, valves that regulate the amount of fluid going to the actuators are called flow control valves.

Operating System of the Flow Control Valve

By controlling the amount of liquid/air passing through a given cross-section per unit time, the speed of the liquid/air — and therefore the speed of pneumatic actuators — is controlled as well. For this reason, flow control valves are also called speed control valves.

All on/off valves and taps are also, at the same time, a type of flow control valve.

Adjustable Flow Control

Flow control valves can restrict fluid flow steplessly, adjusted by a screw or lever.

One-Way Flow Control

Flow control valves with a check valve restrict flow in one direction while allowing free flow in the reverse direction.

Speed Control Application

These valves are frequently used to precisely adjust the speed of movement of hydraulic cylinders.

Types of Flow Control Valves

One-way flow control valves. (Check valves)
Two-way (adjustable) flow control valves.
Deceleration valve
Adjustable flow control valves with a check valve

One-Way Flow Control Valves (Check Valves)

Their construction is very simple and basic. As their name suggests, they allow fluid to pass in one direction. There are ball-type and conical-disc (poppet) type versions.

To review the topic where we cover check valves in detail:
See: WHAT IS A CHECK VALVE. HOW DOES IT WORK?

Two-Way (Adjustable) Flow Control Valves

Also called a speed regulating valve.
By narrowing or widening the cross-section through which the pressurized fluid passes, the amount of fluid passing per unit time can be adjusted. This way, the speed of movement of the actuators is also adjusted. The desired setting level is locked in place. They’re used for adjusting the speed of a cylinder’s piston rod. They cannot be fully closed.

adjustable flow control valve — Speed regulating valve

The adjustment screw is closed down or opened up to let the desired amount of fluid coming from the pump (P) pass through. (Picture above)

Deceleration Valve

Deceleration valves are used to bring the piston speed under control during certain specific periods of the actuator’s stroke. The valve is controlled by a cam, and depending on the shape of the cam, it increases and decreases the actuator’s speed. A normally-open valve reduces flow when the cam releases the piston, and a normally-closed valve increases the flow through the valve as the piston is progressively released (A and B in the figure above).

Adjustable Flow Control Valves with a Check Valve

Positions of Flow Control Valves in the Hydraulic Circuit

1. Meter-in control of fluid going to the hydraulic cylinder: a double-acting cylinder is controlled by placing the flow control valve between the pump and the cylinder.

2. Meter-out control of fluid leaving the hydraulic cylinder: control of the fluid leaving the cylinder is done by fitting a flow control valve immediately after the cylinder.

3. Bleed-off control of fluid going to the cylinder, part of which returns to the oil reservoir: this is the control done when, before entering the cylinder, part of the fluid passes through a flow control valve and returns to the reservoir.

Video Explanation About Flow Control (Speed Control) Valves

Related Questions

The valve limits the flow rate by restricting how much fluid can pass through toward the cylinder per unit time. Since less fluid arrives per unit time, the cylinder moves more slowly.

These valves are designed to slow down the cylinder’s movement in one direction (for example, extending) while allowing its return stroke to be fast. The check valve mechanism makes these different speeds possible by letting fluid pass freely in the reverse direction.