The first 2 in the 2/2 air valve refers to the number of “working” air ports that are found in the valve body. That is, the number of ports that supply air to the valve, and station the compressed air to whatever it’s that the valve is supposed to do.
Most 2/2 valves will have numbers or letters etched, painted or throw near each of the two “working” air ports. If there are numbers near the vents, the number 1 are the supply port to bring the compressed air to that valve.
Port number 2 would be the working port where air would flow to accomplish whatever task that you desired that valve to perform.
If the port designations are letters, then vent ‘A’ would be the supply port and port ‘B’ the working port.
If the 2/2 valve is to be “air operated”, that is an external air sign is to be used to shift the 2/2 valve, then there’ll be another port. Browse http://nssteel.co.th/ for more info about various kinds of valves.
That port might not have a designation or it may say ’12’. No, that is not a twelve, but instead indicates that air will flow from port 1 to port 2 when an outside air signal operates that valve.
The second 2 in a 2/2 air valve indicates the number of positions that the inner valve mechanism has. In this case, two.
If this valve is operated or actuated, it will either open or shut. At rest, that is when the external valve operator hasn’t been activated, the internal valve mechanism will either stay open or closed. Except this, Browse http://www.nssteel.co.th/ for more info about Steam systems.
Most 2/2 compressed air valves are classified as NC. NC stands for normally closed. This means that when the valve is not actuated, it’s normal state is closed, and compressed air can’t pass through it.
There are some applications for 2/2 valves in which the flow of air through the valve when it isn’t being controlled is desirous. A NO or normally open valve would then be selected.
All 2/2 valves will have actuators that will operate or ‘shift’ the air valve.
A compressed air blow gun is a fantastic example. On it there will be a push button or a trigger of some kind. A compressed air blow gun contains a 2/2 NC air valve.