3-2 Air Valves Too

This is page two of 3-2 air valves information. Page one is located here.

The 3/2 air valves article continues, below.

Detented 3-2 Air Valves

When the 3/2 valve is operated, if it stays in its last selected position until an operator changes it again, then it is called a detented air valve.

Detented means it will stay where it's put! Detented valves are useful when an operator needs to actuate a valve and then perform another operation while the detented valve continues to feed compressed air to the application.

Single Acting Devices

The 3/2 air valve is commonly used to supply compressed air to single acting cylinders or other similar compressed air using devices.

These could be air cylinders, air springs, or air diaphragms, anything that is configured to "automatically" let the air back out when the compressed air supply flowing to it is stopped.

For example, a single acting air cylinder may contain a spring that will drive the piston in one direction when the compressed air is shut off, saving energy since compressed air is being used only half the time.

Another device that is normally supplied compressed air through a 3/2 valve is the air spring.

Picture a big rubber tire with a plate covering both sides of the center hole. Into one of the plates is a female port to allow an air supply to be connected. Place this air spring under something, and you have relatively low cost actuator able to supply tremendous loads as compressed air flows into it. When the lifting process is completed, the air flows back out through the exhaust port of the 3/2 valve, and the "tire" deflates. Neat!

The Big Difference

And that is the big difference between a 2/2 and the 3/2 air valve. With the 3/2 style, the air can get back out through the valve when necessary. With the 2/2 valve it cannot.

How 3/2 Valves Work

When the external actuator of the valve is released, an internal valve spring shifts the valve to off. The air supply coming into the valve becomes blocked so no more compressed air can flow through the valve to the application.

In shifting to off, the internal pathways of the valve open the working or power port that is connected to the actuator, and opens the exhaust flow path in the valve, allowing the compressed air in the actuator to flow freely back through the valve to the exhaust port and out to atmosphere.

Speed Control

If the exhaust port on a 3/2 valve is threaded, then you can install an exhaust flow control so that the exiting air can be metered to reduce its speed, and thereby, reduce the speed of the air using device, at least in one direction.

Convert 3/2 to 2/2

If the exhaust port in the 3/2 is threaded then, in the event that you actually needed a 2/2 air valve for your application, by threading a plug into the exhaust port of the 3/2 valve, you have created a 2/2 valve.

Some manufacturers don't even manufacture 2/2 valves any more, since the conversion from 3/2 to 2/2 is simple, and this reduces manufacturing costs. This strategy helps reduce inventory too.

Last point on the 3/2 valve. Two of them can be used to operated a double acting air cylinder in the event that a 4/2 air valve isn't in stock when you need it. You simply plumb the cylinder / power port from each valve to one of the two cylinder ports and voila, as each 3/2 is actuated, the cylinder will extend and retract.

Here's how to draw a 3/2 valve.

Let's have a look at 4/2 valves now. Please click here.