What is a pneumatic steering control valve?

What is a pneumatic valve?

The pneumatic valve is a very important element in our pneumatic circuit that will allow us to direct or distribute the air towards one element or another, control the pressure or regulate the flow. Depending on the application we need, we will use one type of valve or another.

What types of valves are there and what are their drives?

There are several types of valves. But we have 3 types of valves among the most common that according to their function and properties are classified as follows:

Directional or directional control valves

These valves control the direction and deviation of air towards the rest of the elements, added to the start and stop, without influencing the pressure or the air flow consumption. For this we will use 3, 4 or even 5 routes.

Flow control valves

Flow control valves, or also known as flow control valves, have the purpose of regulating the speed of an actuator by regulating the flow. And they are called auxiliary valves.

Pressure control valves

This type of valve is also called an auxiliary valve, and its main function is to protect other elements of the electrical circuit from overpressures. So if they detect a high pressure in the circuit reaching the maximum expansion level, it will cut off the air passage. In this way, by means of cuts and openings of the air flow, the pressure in the pneumatic circuit is constantly stabilized.

How does it work and how to read a pneumatic steering valve?

Today we are going to focus on the steering control valves due to their greater importance and relevance in the pneumatic circuits that we can find.

The assembly of any distribution valve consists of two totally differentiable parts. On the one hand, we have the distributor itself (black elements in the following image), which is responsible for directing the air flow towards the pneumatic receivers, which depending on our needs can be 2/2, 3/2, 4/2, 4/3, 5/2 or 5/3.

And on the other hand, there is the actuating device of said distributor (red element in the following image), which may well be pneumatic, electrical, manual or mechanical.

So far we have been explaining theoretically what is relevant about valves. We are going to focus now on a more practical part to explain how they work. As we can see in the previous photo, we have in front of a normally closed 3/2 valve. In the centre we have two black squares that represent the slides, and therefore, the 2 possible positions that our valve will work. Then, we have in red the electrical actuator of the valve that will allow us to change to the position that is next to it, the one on the left. And finally, in blue we have a return spring drawn in the diagram that will always make us return to the initial position or also called rest. This being the square on the right.

How to identify which pneumatic valve is a 3/2 and how does it work?

The name 3/2 has created confusion many times, but we are here to answer your questions and help you. The first number, bone 3, indicates the number of ways (inlet / outlet orifices) that the valve has. While the 2 indicates the positions that the internal slide can adopt. As we can see in the photo.

Within the elements of the pneumatic diagram we can find the intakes with their corresponding numbering. The 1 corresponds to the intake, air inlet or power supply, while the 2 represents the hole through which the air will come out towards an element that we want to activate or redirect the air. While the 3 corresponds to the escape.

The operation of the valve is very simple. In this case we have in front of a 3/2 as we can identify according to the previous indications, and if we look at the 1 in the part of the diagram corresponding to the spring we can see in green that it is closed. This tells us that the valve is normally closed. In addition, we can verify that 2 has the escape output enabled by 3 (red arrow).

On the other hand, if we look, once we actuate, in this case electrically, the valve, 1 is open, diverting the air pressure to 2 (blue arrow) to activate or redirect the air to our element connected to the valve. And number 3, which corresponds to the exhaust, we have it blocked so as not to have air leaks in the circuit.

How to identify which pneumatic valve is a 5/2 and how does it work?

Like 3/2, the name 5/2 has also brought a lot of confusion but using the logic explained above it will not happen again.

The 5 corresponds to the tracks as we saw and the 2 to the positions of the slide. On this occasion we have put a pneumatic return instead of a spring so that you can see its symbols that you can find in the image.

The operation of this valve is very similar to that explained above. In this case we have 2 elements to which we want to direct the air that we will have connected in 2 and 4 or a double effect element where one effect will go to 2 and the other effect to 4.

Now depending on whether the valve is at rest or the activated, the air will go to 2 or 4 respectively as we can see in the image (2 at rest and 4 activated). Each of the connected elements (2 and 4) has its corresponding escapement (3 and 5). As we can see, while the air from the intake intake (1) is not directed to these elements, its corresponding exhaust remains free so that the air can leave our pneumatic element and thus the receiver is not blocked.

Learn how to connect a pneumatic valve

With these simple steps that we have seen, we will learn how to connect a pneumatic valve correctly.

Here is a brief summary:

1 – Air inlet. In this way we will feed our valve, generally directly from the network that is usually fed by a compressor.

2 and / or 4 – Elements where we want to direct the air , for example, if it is a single-acting cylinder we will use a 3/2 (way # 2) or on the contrary, if it is a double-acting cylinder we will use a 5/2 ( routes 2 and 4).

3 and / or 5 – Exhaust of our elements , it is always advisable to use silencers, since in addition to damping the noise of the exhaust, they prevent the passage of particles in our valve extending its life.

Pneumatic Valves Connectors and Threads

As a general rule, the connections are female and the threads are 1/8, 1/4, 1/2 and 3/4. Although exceptionally and less common (it all depends on the application) we can find threads of even 1 ”(one inch).

The fittings that are used are normally male fittings of the aforementioned threads, on the one hand, and on the other, quick connections to receive air tubes that are usually of external diameter, 4, 6, 8, 10 or 12. Although We can also find applications that work with lower or upper pipes.

Positions and Interlocks

In the following image we can see that the V-shaped slits correspond to the positions of the pneumatic valve. While the line above one of them is indicating that this position has an interlocking.

What is interlocking? Interlocking means that once the valve is manually or mechanically actuated to one of its positions, it remains fixed in that position without the need to continue exerting any type of force to retain it.

Final conclusion on pneumatic valves

With all the above data, you should no longer have any problem physically identifying, knowing how to connect or identifying any type of pneumatic valve in a pneumatic diagram. You will be able to identify the 3/2 way, 5/2 way, 5/3 way, 2/2 way, 4/2 way and 4/3 way valves.

Remember that we are always at your disposal to advise you and offer you a technical service, as well as to supply you with all the components you need, both Hydraulic and Pneumatic.

Source: Hynesur

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Matthew Seaman

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