Directional Control Valves: Ports and 'Ways'

2 Port Valves

2 port, 2 position valves have a single path through the valve which can be opened or closed. Actuation is typically via an electric solenoid, but air pilot and manual actuation are also somewhat common. 2 port, 2 position valves provide a simple on/off function, and are used to connect, switch, or isolate discrete systems. While primarily intended for pipeline applications (instead of pneumatic) AutomationDirect offers a variety of 2 port pipeline valves.

3 Port Valves

With 3 port valves, the air path is either from the pressure port(1) to the actuator port(2), OR from the actuator port(2) to the exhaust port(3). 3 port valves are often used with spring return cylinders, so that the spring action returns the cylinder to the retracted position when the valve is in the exhaust position. 3 port valves can be electrically driven in both directions with 'double solenoids' (requiring separate control signals), but it's more common to have a single solenoid with spring return (and operate in sync with a single control signal).

4 Port Valves

4 port valves offer the ability to extend and retract a cylinder using pneumatic force in both directions. When connected to a double acting cylinder, a 4 port valve allows air pressure from one port to extend the cylinder, while allowing air from a second port to exhaust, and visa-versa. Two position versions are used when simply extending and retracting are desired, while three position valves allow for special operations. The Center Closed version is the most common, and allows "inching" operations. Other options include center exhaust, and center preasure.

5 Port Valves

5 port valves offer similar functionality to 4 port valves but have separate exhaust ports for each actuator port (this is generally due to the mechanical layout of the valve, and an effort to keep the valves simple and to reduce cost). If speed controls are used on the exhaust ports of the valve the speed of the cylinder motion may be individually controlled for the extension and retraction strokes.

5 port valves are available in 2 position and 3 position models (learn more). The 2 position models are available with double solenoids or single solenoids (with spring return). The 3 position models have double solenoids.