Pneumatic Valves – General Info

Valves are generally 3/2 for single acting systems (air bags, spring return actuators) and 5/2 or 5/3 for double acting systems (most cylinders).  The first number is the number of ports, the second is the number of valve positions.

For example a 5/2 valve would be used for a cylinder that has only two positions (extended and retracted).  A 5/3 valve would be used on a cylinder where the movement might be required to stop between extended and retracted.

Port Size

The size of the ports in valves can vary from 1/8″ right up to 1″ or larger.  The size is dictated by the flow of air required, which is dictated by the size of the cylinder and the desired speed.

Valve Movement

Finally there are three main ways of moving the spool:

• Manual (hand lever, foot pedal, plunger).
• Electrical via solenoid coils.
• Pneumatic pilot operation where air pressure is used to move the spool.