Common Types of Pneumatic Valves

Pneumatic valves are one of an array of components responsible for controlling the pressure, rate, and amount of air as it moves through a pneumatic system. Pneumatic systems, which depend on the force of compressed air to transmit power, can be found in countless industrial flow control applications, from pneumatically operated power tools to diesel engines. Based on other components within a given application and the type of pneumatic system used, one of several types of pneumatic control components valves may be found at the heart of the device.

The term “pneumatic valve” generally has two distinct contexts of use which require some explanation. In the first context, a pneumatic control valve is a device that is used to control or modulate the flow of air (or another inert gas) in a pneumatic system. They do so by controlling the air or gas at the source, regulating its passage as needed into tubing, pipes, or devices in an automated pneumatic system. The actuation component that causes the pneumatic valve to open or close might be accomplished in any of several ways, including manually, electrically via a solenoid valves or motorized actuator, or pneumatically. The key concept to note in this case is that it is pressurized air or gas that is being controlled and which is flowing through the valve ports in the pneumatic system.

Functional directional control valves, those that control the direction of air flow or inhibit flow all together, are a large class of pneumatic valves that houses multiple variants. These devices can be used in various ways in a hydraulic system, such as to connect or disconnect the main compressed air supply from the system or to advance or retract air compact cylinders that move as part of the machine or process for which the pneumatic actuator system has been created.

A directional three-way air control valve has three ports, each of which serves a different purpose. The first port is used to connect the valve to an actuator or another device. The second port is connected to an airflow. The third port is used as an exhaust exit. When the first and second ports are open and the third is closed, air moves through the valve to the device. When the first and third ports are open and the second port is closed, the actuator can vent exhaust.  Three-way valves are often connected to actuators in cylinders or used in pairs and connected to double-acting pin cylinders.

Four-Way Directional Control Pneumatic Valves

A four-way directional valve has four distinct ports, two of which connect to actuators, one that connects to a pressurized airflow, and one that serves as an exhaust pathway. They are among the most common types of valves found in pneumatic systems because the four distinct paths allow the valve to effectively reverse the motion of a motor or basic clamp cylinders. An additional port is sometimes added to a four-way valve, making it a five-ported four-way valve. A four-way valve with an additional port is often used to provide dual pressure, meaning the valve can apply one of two kinds of pressure and alternate between the two depending on what the application requires. Alternatively, the valve can use the other port as a secondary exhaust port.

Pneumatic valves can be spring offset or detented. In spring-offset valves (as described above), the valve will return to the starting state or condition when any actuation is removed. In detented valves, the valve will remain in the last activated position until it is switched again by the operator.