2-2-Air-Valves2-2-Air-Valves; what are they and how are they used in a compressed air circuit? Let's identify what a 2-2-air-valves is, first. If a compressed air valve is labeled as a 2-2 air valve, or a 2/2 air valve, these designations indicate the following about that particular air valve:
Valve At RestWhen an air valve is not being actuated by an electric or manual or internal operator, or when someone isn't pushing the button or moving the valve's lever, it is normally referred to as being "at rest". If the "at rest" position results in the air valve being closed (compressed air is not flowing from the in to the out port) then this valve is deemed an NC valve - one that is normally closed. If, at the "at rest" position compressed air flows from the in port through the valve to the out port, then this valve is deemed to be NO - a normally open valve. For most applications the NC form of an air valve is selected, as most will need the compressed air shut off when the valve is at rest. Actuated ValveAn air valve is actuated when that valve's external actuator is being operated by someone or something. This could be an operator pushing a button or lever, a moving object depressing a toggle or whisker switch, or electricity operating a solenoid actuator on that air valve. Please note that I differentiate between the actuator (the device that is used to actuate the valve) and the operator (who is a person that actuates the valve). Others may not use this same differentiation, so when you are talking to colleagues about compressed air, do make sure you understand their frame of reference and make sure you are talking about the same thing. 2/2 Valve ApplicationsApplications for the 2/2 air valve are varied. The 2/2 NC air valve that folks most often come in contact with is the air gun or blow gun.
When the external actuator (the trigger or button) is actuated, air will flow from the supply side out the nozzle. When the actuator is released, the internal actuator (the spring inside the gun) moves the internal seals back into place to stop the air flow. You can see from the photo that the blow gun's working port is the gun barrel, and it has no stop on the end. The barrel is open to atmosphere. That means that when the actuator is released, supply air stops flowing, and the compressed air that is in the gun and barrel of the blowgun continues to vent to atmosphere until it reaches ambient atmospheric pressure. This is a typical application for 2-2-air-valves. The ultimate destination of the compressed air that's flowing through it is atmosphere, not into a vessel or cylinder. Blow Off / Cleaning ApplicationsAside from the blow gun referred to above, other applications for the 2/2 air valve include quality control, cleaning, blow off, cooling, drying...etc. In fact, 2/2 air valves are used in any application where the compressed air flows through the valve to atmosphere. Here is more information on 2-2-air-valves.
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