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Here are the steps.
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Start by drawing a square on your paper. It's easier if you use graph paper to help keep the lines straight. Then, after you've drawn your box, add a couple of lines to the square, as shown in graphic Fig.15a above.
The outer square box depicts the valve body. The air paths through the valve and the two ports in a 2/2 valve are shown by a line or lines running into the valve body from the top and bottom center.
If the two ports are shown as in the drawing in Fig. 15a, then the air cannot flow through this 2/2 valve. It is depicted as closed. The "cross bars" drawn at the top of the lines inside the box shows that air cannot flow through this valve.
Some circuit designers show the lines that are depicting the ports extending slightly through the wall of the valve. Some don't. I am of the latter persuasion.
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If the lines are as shown in the drawing in Fig. 16, then it shows that air can flow through this valve and this graphic depicts the valve as open.
Remember the definition of a 2/2 valve? It’s a valve that has 2 ports, and two positions, right?
In Fig.15a and in Fig.16 we show the same 2/2 valve in both possible configurations.
In one we show that the flow path through the valve is closed, and in the other we show the flow path as open. Both schematics are showing the same valve, in each of it’s two possible flow-path configurations.
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In Fig. 17 we have taken the two drawings, Fig.15a and Fig.16, and joined them together. Now we have the schematic for one complete 2/2 valve.
Fig. 17 shows the same valve with both possible valve configurations depicted. On the left side of the drawing the valve is shown as open, and on the right side of the same drawing that same valve is shown as closed.
The positioning of the two graphics of the same valve, either with the air passing through it on the right side of the drawing, or the air not able to pass through it placed on the right side, has meaning. I will discuss this later.
Please let me reiterate to make it clear! Fig. 17 shows one 2/2 valve, with both possible configurations or positions for that one valve, drawn in a single graphic.
And this is how you draw the basic 2/2 valve!
You will realize that a 2/2 valve won't work all by itself? To use a 2/2 air valve you will need valve actuators.
A circuit drawing can't just show the air lines and the various valve bodies and components, but must also show how each valve is to operate. Then, others looking at your circuit drawing, will know what valve and what valve actuators to select for that circuit.
In this page, in order to keep the concepts and the drawing of the valves as un-complex as possible, I have not shown the valve actuators.
Please go to this page to learn how to draw valve actuators.
Need to find some valve suppliers? Feel free to use the search box below:
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