Pneumatic valves are part of a wide range of components that are charged with controlling pressure, rate and the amount of air that moves through a pneumatic system. The force of the compressed air needed in order to transmit power usually dictates the kind application you’ll find a pneumatic system in – ranging from diesel engines to power tools. In a few cases, you can find several kinds of valves in one application.

In this week’s post, we’ll cover some of the basic types of pneumatic valves and what they do.

Three-way directional valves

Like the name implies, three-way directional valves possess three ports – each of which serve a different purpose. The first port connects valves to actuators or other devices. The second connects to an air-flow. The third is commonly used as the exit or exhaust. When the first two ports are open, the third is closed, allowing air to move through the valve to the device. Likewise, when the first and third are open, the second port is closed, allowing the device to vent exhaust. You’ll most likely find three way valves connected to actuators inside cylinders or they’re deployed in pairs and connected to double-acting cylinders.

Four-Way Directional Valves

Four way valves add another port to a three-way directional valve and work in pairs. Two valves connect to actuators while the others serve as the entrance and the exhaust. Four-way valves are likely the most common types of valves found in pneumatic systems because the four ports allow the valve to reverse the motion of a motor or cylinder, making them an extremely versatile component.

Spring offset

Spring offset valves are named for the way and manner in which the direction of air-flow is switched. So for example – in a two-way vale; the valve’s either open or shut. In order for those valves to assume a particular position, an actuator has to move a valve spool into position. In spring valves, a spring releases the spool to open and shut the valve.

Resting states and open vs closed

Spring valves come with a bit of a nuance – and that’s two-way directional spring offset valves. In those – there are only two positions that the valve can assume when the actuator isn’t active: either open or closed. When the valve is in the open state, air is able to move freely throughout the valve. When it’s closed, air flow is blocked.