2-2 Air Valves
In a particular quality control application, a product may be moving down a conveyor system. When the product moves through a quality checkpoint, a sensor (perhaps a weigh scale or some sort of colour scanner) determines if that product meets the quality set points. If it does not, a signal is sent to a PLC which in turn sends a signal to an actuator on a 2/2 air valve. The 2-2-air valve shifts, and compressed air flows through the valve to a nozzle, to blow the defective part from the conveyor.
Some other 2-2 Valve Applications
In another application for a 2/2 valve, parts may be exiting a manufacturing operation, and if debris is noted by the quality checking sensors - then, a signal is generated that actuates the 2/2 valve allowing it to blow air through the air knife onto the part to remove debris from the part.
Typically, the 2-2 valve that could be used in the quality control or cleaning operations as noted above is a solenoid actuated valve. In the graphic just above is a small 2/2 air valve with a solenoid operator and a DIN electrical connection.
A Cooling Device
When compressed air is flowed through certain types of devices, the flowing compressed air generates a cooling effect.These venturi compressed-air-driven appliances are used to provide simplistic cooling to control cabinets where the application cannot use other typical forms of cabinet cooling such as fans or refrigeration.
Typically, when the temperature inside the cabinet reaches a high level set point, a signal is generated which, in turn, opens the 2/2 air valve. Compressed air flows to and through the cabinet cooler, and lowers the temperature in the cabinet to an acceptable level. When the low temperature set point is reached the air valve shifts to a closed position until the high set point is again reached and the cycle repeats.
Driving Air Motors
2/2 air valves are used to drive air motors.As an typical example, an air motor may be powering a fixture to turn tops onto bottles. When a bottle reaches a set spot in the assembly line, a signal is generated. The PLC fires the 2/2 valve which powers the air motor, and possibly also triggers an air cylinder to position the motor, and the air motor then turns the cap onto the bottle.
A compressed air regulator could be used to modulate air motor force, allowing the air motor to stall out before it over torques the cap.
Or a simple timer may be used, which allows the air to drive the air motor for just the time it takes to install the cap, and then shuts off the signal to the valve, and stops the air motor.
Air Driven Pumps
Compressed air driven pumps are another frequent user of 2/2 valves.For example, picture a submersible air pump in a tank. A float switch signals when the tank level reaches a set point, a signal is sent to the PLC and then to the 2/2 valve. The pumps starts and runs until the level in the tank reaches a low set point, at which point, the PLC is signalled again, and the valve is de-energized, allowing the pump to stop. The cycle repeats as the level in the tank reaches the start set point again.
A Problem!
Do you see a potential problem with using the 2/2 air valve in certain applications?No 2/2 air valve can be used to supply air to any device that is a closed vessel as once the 2/2 air valve is shut off, compressed air in the air line from the valve to the application, and any compressed air in the application itself - both now at full line pressure - is trapped! Compressed air cannot get back out if it is a 2-2 air valve that is used to supply air to that application.
As a result, 2/2 air valves are normally only used when the application ultimately leads to atmosphere. Then, when the valve is shut off, air in the downstream line can bleed off, through the application, to atmosphere.
Valve Sizes
2/2 air valves are available in a variety of port sizes - in some cases as small as 4 MM or 10-32.Of course, as the need for more air flow for the application is determined, larger ported 2/2 valves are selected.
Consider The Economies Of Manufacturing
For purposes of economy of manufacturing, larger air valves used for a 2/2 application may have 3/2 or even 4/2 body styles, with any unused ports plugged to configure the flow paths of these valves to 2/2 format.It seems more economical to make larger bodied valves multi-ported and then to have the unused ports plugged for different applications than it is to purchase tooling to manufacture many different body styles. And, there are fewer applications for really large 2/2 air valves too.
Installation / Application
When needed, 2/2 valves can be stacked or manifolded together. Other models can be sub-based type installations, to allow removal of the valve without touching the valve air line plumbing.Or, 2/2 valves can be plumbed individually in line as needed.
Drawing The 2/2 Air Valve
And no, I have not forgotten.Here's where you learn how to draw the schematic for a 2/2 air valve.
Forum
To allow us to share information on the 2/2 air valve, I have set up an 2-2 air valve forum here. Share your experiences or question your use of this useful air valve.
