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On the first page about compressed air valve actuators, we wrote about the valve internal spring actuator and the external valve actuator known as an air pilot.
On this page we will review additional common compressed air valve actuators.
Solenoid Valve Actuators
A solenoid , in terms of compressed air valves, is a device that allows the operation of the air valve with just an electrical signal (be it a control signal with low voltage or power signal to actually do work), or a combination of an electrical signal and compressed air to actuate the valve.
When an air valve is actuated solely by the electrical signal, that solenoid valve is defined as being one that is “direct acting”.
When a solenoid valve uses both electricity and compressed air to shift that air valve, that type is deemed to be a solenoid pilot valve. The difference between the two is a page unto itself, and how a solenoid converts electrical into mechanical energy, will be linked from here shortly.
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Fig. 44 shows a double solenoid pilot operated air valve.
A compressed air circuit may be controlled entirely by electricity, and all the compressed air valves, the proximity switches, temperature sensors, E-stops, they all can receive signals from, and in many cases send signals back to the "brain" of the air circuit, the PLC. (Programmable Logic Controller)
When the solenoid valve actuator gets an electrical signal from somewhere, and assuming that the valve is in good shape then the valve will shift and air will flow to the application. Please click this link if you wish information on how water in the lines negatively affects compressed air valves.
Solenoid actuators usually come from the factory already attached to their air valve. It's necessary to bring a power supply to each of the solenoid valve actuators.
One way to accomplish this is through the DIN type connector , the type shown in Fig. 44. Rather than "hard wiring" directly to the air valve, the hard wiring need only go to the DIN connector cap, which is connected to the valve via an internal plug. Use of the DIN connector allows the non-electrical-skilled maintenance person to disconnect and re-connect the wiring to the valve quickly and safely when that valve needs to be changed out.
If you opt for the DIN type of electrical quick connect, do purchase a one that contains an LED that will light up when the valve is energized. With that option you will be able to tell whether or not the valve solenoid is actually getting an electrical signal, should the air circuit not be performing properly. If the DIN connector lights up, you know the power has made it to the valve. Now, it's either the valve that has failed, or a component downstream from that valve is at fault.
More on compressed air valve actuators coming soon.
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