5-2 Air Valves

5/2 air valves have specific and unique uses other air valves do not.

If you are supplying air to a double acting air actuator of some sort, perhaps a double acting air cylinder or a double acting rotary actuator , then your valve choices to supply them are to use two 3/2 valves, a single 4/2 valve, a single 5/2 valve, or a single 5/3 air valve.

Since the purchase of one air valve will cost less than two valves of comparable size, circuit designers will opt for a single 5/2 or 4/2 solenoid valve to operate the double acting air actuator rather than two 3/2 valves.

How 5/2 Valves Work

The 5/2 configured compressed air valve works the same way as the 4/2 style.

The 5/2 valve will have two actuator ports that are plumbed to the air actuator (air cylinder). When compressed air is supplied to the 5/2 valve, that air will pass through the valve and air will flow to just one of the two actuator ports.

The other actuator port will then be open to exhaust, allowing air from one side of the air actuator to escape, as a fresh compressed air supply flows into the other cylinder port.

When the 5/2 valve is shifted, regardless of what actuator is used to shift the valve, the spool or poppet inside the valve moves, and air is directed to the other actuator port. Then the previously charged line is opened to atmosphere allowing it to become the exhaust line from the actuator.

In this manner, the actuator rod or shaft can be extended or retracted alternatively; hence the term double acting.

The home position for the actuator (whether it's an extended or retracted rod or, if a rotary actuator, rotated in one direction or the other) will be determined by the requirements of the application. The 5/2 valve will be plumbed to ensure that air is supplied to the appropriate actuator port to achieve the desired rod position when the air valve is at rest, based on the demands of that particular air circuit.

5/2 Valve Numbers

The first digit in a valve designation number refers to the number of ports that the valve has. The second number is the number of positions the internal air control has. Therefore, a 5/2 air valve will have five ports and two positions.

Two of the ports are power ports to send compressed air to, and to alternatively exhaust air from, from the air cylinder.

One of the ports will be the supply air from the air main or the air compressor, to the valve.

The other two ports - and this is the difference between the 4/2 and 5/2 - the other two will be exhaust ports. A 4/2 air valve has only one exhaust port - the 5/2 valve has two exhaust ports.

Two Exhaust Ports

The additional exhaust port provides significant benefit to the system designer. That's why, in selecting a valve for a double acting actuator, I would always opt for a 5/2 version over a 4/2.

Having two exhaust ports allows the installation of two exhaust flow controls , one for each exhaust port.

Assuming that the valve is installed close enough to the actuator that throttling the exhaust at the valve will modify the actuator speed, then having two exhaust flow controls means that the air cylinder can be adjusted for one speed to extend another speed to retract.

For an air operated rotary actuator, the two speed controls can adjust speed of rotation in one direction and allow a different speed for rotation in the other.

Dual Supply Ports

Depending on the manufacturer and their design of their 5/2 valve, you may be able to use the two exhaust ports as dual supply ports, and use what was the original supply port as a common exhaust.

Plumbing the 5/2 valve with supply air to the two exhaust ports does negate the dual flow control possibility for that valve. However, now with the two supply lines, two separate pressures can be sent through one 5/2 valve to allow different forces to be generated by the cylinder in the extend or retract cycle.

If the application for a particular actuator means that it is moving without load in one or the other direction, lowering the pressure for that movement can save significant dollars in reduced compressed air and energy use.

If it's your job to select a valve for a double acting cylinder application, picking the 5/2 design over the 4/2 provides some benefits, all other things being equal.

Interested in learning how to draw a 5/2 air valve? Go here!

What is a 5/3 air valve? Here is where you find out.