How does a pneumatic valve work?

A pneumatic system works by means of compressed air, which is generated by air pressure. A compressor compresses the air to the desired pressure, and this is made possible by the hoses that connect the compressor to various valves.

These valves ensure that the compressed air is directed to the correct parts, and this is determined by which hoses are connected. In addition, safety and pressure reducing valves ensure that the compressed air is introduced into the system at the correct pressure. Valves can be used for direct control of cylinders, for example, similar to a switch that allows you to turn a lamp on and off.

The type of valve you need depends on the way of control.

Types of valves:

How a pneumatic valve works

The operation of a solenoid valve is usually indicated by a symbol

The square frame stands for 1-switch position (several squares mean multiple switch positions)
The lines in the frame represent the connections. These are indicated in the box that shows the normal position/resting state. (usually right)
The arrows in the frame indicate the direction of flow.

2/2 valve
The valve as shown in the drawing below has two switching positions and also two connections (2/2). For example: Connection 1 is a connection to the compressed air supply or to the vent. Connection two is the connection to a cylinder or to the control port of another valve.

3/2 valve
This valve has three connections and two switching positions (3/2). For example: Connection 1 is a connection to the compressed air supply. Connection two is the connection to a cylinder and connection three is a connection to the control port of another valve.

5/2 valve
This valve has five connections and two switching positions (5/2). For example; Connection 1 is the connection to the compressed air supply. Connections 2 and 4 are connections to a double-acting cylinder and 3 and 5 are vents.

5/3 valve
This valve has five connections and three switching positions (5/3). For example; Connection 1 is the connection to the compressed air supply. Connections 2 and 4 are connections to a double-acting cylinder and 3 and 5 are vents.

Properties of a valve

Normally closed (NC)
In the idle or non-actuated position, the valve is closed. When we operate the valve, the valve opens and flow is possible. We call this Normally Closed or NC.

Normally open (NO)
In the idle or non-actuated position, the valve is open. When we operate the valve, the valve closes and no flow is possible. We call this Normally Opened or NO.

Sent directly

The sealing gasket pulls a plunger towards it. This immediately opens or closes the opening. No differential pressure is required (works from 0 bar).

Indirectly controlled

Indirect- or servo-controlled solenoid valves use the differential pressure of the medium to open or close. The minimum differential pressure is usually 0.5 bar. Because the liquid pressure is used, a relatively small coil can still control a large diaphragm and thus a high flow rate.

Semi direct controlled

In this version, the sealing diaphragm is directly connected to the plunger. When the coil voltage is switched on, the plunger is pulled up against the spring force and the auxiliary steering opening is opened. Semi-directly actuated valves switch from 0 bar.

Monostable

Monostable valves are valves that require a continuous control signal to switch the valve. If this control signal is lost, the valve switches back to its idle position by means of spring force.

Bistable

Bistable valves can be permanently switched over by a short control signal. Without a signal, the valve remains in its position. The valve switches back by a control signal on the other side. A separate control is therefore required for each mode.

NAMUR

Valves are available in a standard or NAMUR operated version. A NAMUR valve is a pneumatic valve with a special connection pattern of the valve's outputs. These outputs are normally ports 2 and 4 of a valve. By means of this type of connection, the valves can be mounted directly on a pneumatic actuator equipped with the same NAMUR standard. A pneumatic actuator opens and closes, for example, ball valves and butterfly valves. Thanks to this NAMUR standard, you can place the valve directly on the actuator. Hoses and couplings between the valve and actuator are therefore not necessary.

Find all your pneumatic valves at Pneuparts

Pneuparts offers a wide range of pneumatic valves. They are available in various types, such as mechanical, electric, pneumatic and manually operated. Pneuparts has the right valves for every application, with different controls and specifications. If you have any questions, please do not hesitate to contact us. Our staff is ready to help you make the right choice.

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