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.
This article will review the common types of pneumatic valves that are used in the industry and provide information on the configurations and key specifications associated with these devices. To learn more about other types of valves, see our related guide on the types of valves. For an understanding of pneumatic actuators, see our guide all about pneumatic actuators.
Pneumatic Valve Use Context
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.
In the second context, air is being used as the control mechanism on the valve, but the media that is flowing through the valve ports is something other than air, perhaps water, oil, or some other fluid. In this context, the pneumatic air valve is functioning to provide flow control in a valve, but the fluid being controlled is not air. The air is serving as the control media, being passed through a pneumatic actuator to open, close, or modulate flow as needed. These valves are therefore sometimes referred to as pneumatically-actuated valves.
To summarize, in the first context, air is being controlled but may or may not be driving the control mechanism of the valve. In the second context, something other than air is being controlled but the control mechanism is air. A distinction between these two general contexts will help with a further understanding of pneumatic valves and their uses. The types of pneumatic valves below are generally representative of the first context.
Types of Pneumatic Valves
Pneumatic valves, also called directional control valves, may be classified using several different approaches which include:
the number of entry and exit ports they possess
the number of flow paths or switching positions that are available
the mechanism that is used to open or close the ports
the position the valve is in when in the un-actuated state
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.