Pneumatic valves

A pneumatic system works through compressed air, which is generated by air pressure. A compressor compresses 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 right parts, and this is determined by which hoses are connected. In addition, safety and pressure reducing valves ensure that compressed air is fed into the system at the correct pressure. Valves can be used for direct control of cylinders, for example, similar to a switch used to turn a light bulb on and off.

The type of valve depends on the method of actuation. For example:

Valve operation

The operation of a solenoid valve is usually shown by means of a symbol.

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

2/2 valve
The valve as shown in the drawing below has two switching positions and also two connections (2/2). 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 switch positions (3/2). 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. Connection 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. Connection 2 and 4 are connections to a double-acting cylinder and 3 and 5 are vents.

Valve properties

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

Normally open (NO)
The valve is open in the rest or non-actuated position. If we operate the valve, the valve goes dicth and no flow is possible. We call this Normally Opened or NO.

Directly controlled
The sealing gasket pulls a plunger towards itself. This immediately opens or closes the passage. No differential pressure is required (works from 0 bar).
Indirectly controlled
Indirect or pilot operated solenoid valves use the differential pressure of the medium to open or close. The minimum pressure difference is usually 0.5 bar. Because the liquid pressure is used, a large membrane and therefore a high flow rate can still be controlled with a relatively small coil.
Semi direct cntrolled
In this version, the sealing membrane 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-direct operated valves switch from 0 bar.

Monostable
Monostable valves are valves in which a continuous control signal is required to switch the valve. If this control signal is lost, the valve switches by means of resilience back to its resting position.
Bistable
Bistable valves can be permanently switched by a short control signal. The valve remains in its position without a signal. The valve switches again by a control signal on the other side. A separate operation is therefore required for each position.

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 outlets. These outputs are normally ports 2 and 4 of a valve. By means of this type of connection, the valves can be directly mounted on a pneumatic actuator with the same NAMUR standard. A pneumatic actuator opens and closes, for example, ball valves and butterfly valves. Thanks to this NAMUR standard, you place the valve directly on the actuator. Hoses and couplings between the valve and the actuator are therefore not necessary.

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