The Differences Between Valve Functions

Valves have different functions and positions that suit a variety of applications. The number of ports determines a valve’s role in a pneumatic system.

2-Way Valves

A 2-way valve has an inlet and outlet and a mechanism to control fluid or gas flow. That type of valve can be air piloted, manually operated or solenoid powered. They have on and off positions and operate as normally open or normally closed.

3-Way Valves

A 3-way valve configuration has two positions and three ports, specifically an inlet, outlet and exhaust. The outlet is the common port that’s open to the inlet in one position and to the exhaust in the second. Its function varies depending on application requirements. A 3-way valve can provide directional control in a normally closed or normally open position or operate with a diverter or selector function.

4-Way Valves

This valve is typically used for directional control in pneumatic applications, managing double-acting cylinders and actuators. They can have two or three positions and four or five ports, including one pressure port, two-cylinder ports and one or two exhaust ports. They can be operated manually, piloted by a remote air signal or with an electrical current. In medical applications, 4-way valves are used in oxygen concentration, medical surfaces and left ventricle assistance devices.

What is Normally Closed or Normally Open?

A normally closed valve blocks the flow of fluid or gas through a valve until it’s actuated. For example, a normally closed solenoid valve remains closed at rest and only activates the plunger to open the orifice when the coil is energized.

A normally open valve allows media flow through the valve until the actuator is energized, shutting the orifice. A normally open valve can operate using solenoid, pneumatic, manual and remote actuation.

Find a Wide Variety of Valve Types at Humphrey Products

Our expert team can help you find the right 2-way, 3-way or 4-way valve to suit your application. Review our product catalog and contact us to request a quote.