Different Types of Pneumatic Valves
This valve has just two ports. Supply and output. There is no specific exhaust port. The exhaust function is usually performed at the work. Examples are air motors and air tools.
These valves have three ports. Supply (pressure), output (work), and exhaust. These valves are used in single action (spring return) cylinders, air brakes, pneumatic lifts, machine safety blow downs, and main air supply valves.
These valves have one supply (pressure) port, two output (working) ports and one common exhaust port. These valves are extremely popular in manufacturing in that these can operate anything requiring double action (work and return) functions. Some examples are cylinders, actuators, air boosters, part grippers, etc.
This is the same as a four way (above) except that it has one more exhaust port. Theoretically these valves are supposed to function somewhat faster than a four way. The jury is still out on this matter.
These valves are used as a safety valve in press clutch and brake operations. These are (OSHA) required on all press stamping operations. These valves have two in-line solenoids or operators, they also have one (supply) in-port, one (working) out-port and one or two exhaust ports. All have two distinctly separate internal in-line pistons which must cycle together or the valve will not cycle at all. These valves are connected to the ‘palm buttons’ which a worker depresses to cycle the press. Integral to the design is a safety design in which the valve must be completely at rest at the end of each cycle or the valve will not cycle at all. This doesn’t mean that the valve failed, this means it is working properly. This is a way that the press operating system knows that a worker’s hands are out of harm’s way.
In regards to the 2-way and 3-way valves there are two different configurations and the following explanations are necessary to add:
Normally open (or ‘passing’) valves are fully open when the operator is at rest and air will be at full flow. When the valve is energized the valve will close and no air will pass.
Normally closed (or ‘non-passing’) valves are closed and air cannot pass when the valve is at rest. When the operator is energized full flow is achieved.
Note: 4-way (4-port and 5-port) valves have one normally closed and one normally open working port.
Valve is leaking out of exhaust port:
On a two-way or three-way valve, turn off all incoming air, disconnect pipe/hose from the work port and plug it. Turn the air back on. If the valve continues to leak it should be removed from service and repaired or replaced.
If the valve is a 4-way or 5-way leave the air on. Whichever work port is exhausted remove hose, pipe or tubing. Determine if the leaking air is coming out of the valve or the ‘work.’ Reinstall piping and cycle valve. Remove the other hose, pipe, or tubing and repeat steps. If the leaking air is coming out of the valve remove the valve from service and repair or replace.
If the leak is coming out from the work (cylinder, actuator, air motor, etc.) the system should be shut down and the work should be serviced or replaced.
Operator (pilot) is making a chattering noise when cycling:
This problem occurs when an armature in an electric pilot goes out of tolerance. This happens through normal wear and tear and is usually undetectable by the naked eye. If this should be the situation the pilot should be serviced (rebuilt or replaced) immediately.
Valve cycles by hand (manually) but not electrically:
There are numerous items to check in this case: Power is turned off, pilot is in need of service, or coil is burned out. Many OEM’s claim this cannot happen with their designs but don’t believe them. It happens to all of them – no exceptions.
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