Air Compressor Solenoid Valves

Hi. I’m in China. As it is hard to explain to my workers some things I need, I decided to do some simple tasks by myself.

I’ve found so interesting this pneumatics field that I didn’t enter before. I’m Mexican. Buying pneumatics stuff  in Mexico is so expensive. Here, just 1 or 2 cents of USD for any piece you want, so the possibilities are infinite…but, for that price, I won’t get enough support, so I look for assistance from you.

My questions are these….

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We answer…

Hello Francisco. Very nice to hear from Mexico via China!

I’ve taken your questions and listed them below, and answered each as best I can.

#1) What is the small bolt located at the bottom of the solenoid valves? This bolt may be pressed down and turned about 90 degrees.

Answer: Without seeing a photo it’s hard to be sure, but I suspect what you are referring to is a manual over-ride. This allows the valve to be shifted manually to direct the compressed air to a different valve port.

The use of a valve manual over-ride is also a  way to diagnose a fault in air circuit. If an air cylinder isn’t responding as it should, once you’ve made sure it’s safe to do so and the compressed air supply is on, you can manually actuate the valve with the over-ride.  If the cylinder works while you are manually operating the valve, that would suggest that the fault in the compressed air circuit is in the valve, not the cylinder.

#2)  What is the difference of a valve with a single or double solenoid? I mean the difference in functions.

Answer: Most single solenoid valves shift when the solenoid is energized. In the absence of an electrical signal to the solenoid, an spring inside the valve returns the spool or poppet to the de-energized location. That’s a single solenoid, spring return compressed air valve.

If you have a double solenoid on a valve, then the circuit designer decided that he didn’t want that valve to shift back automatically when the solenoid was de-energized. Adding the second solenoid instead of an internal spring return would accomplish this. Sometimes 3-position valves have two internal springs and two solenoids, providing a different function. You need to know if your air valves are 2 or 3 position to understand what that double solenoid valve is supposed to do in the circuit.

#3) I’ve seen some applications that have a small tank (something like an accumulator). What is that for?

Answer: Again, very difficult to be sure without seeing it, but I suspect that it’s a pneumatic timing device that will allow an air signal to decay slowly in an air control circuit, thereby allowing something else in the circuit to occur before the valve shifts back. Back when PLC’s were very expensive, people used to build air circuits that ran with air signals only, no electricity. Nowadays, and particularly in China, small, capable PLC’s are low cost, and it’s almost always better to use a PLC and solenoid valves for circuits now that to try to build an air logic circuit. Air logic still has it’s place (particularly in flammable locations) but solenoids are the way to go for most air circuits these days.

#4) There are some devices that feed (step by step) a coil of material into a press. In my factory we punch brass (to make key blanks) and we are considering to purchase one of these air feeders but would like to know how it works. Do you know them? Can you help me to understand?

Answer: There are a number of pneumatic companies that make pneumatic press feed circuits. Yes, I do know how they work. In terms of their function, it’s a system whereby an air circuit alternately clamps, strokes, unclamps and returns,  to regularly feed a fixed length of product into a press.

I’m afraid if you’re looking for installation assistance, you’ll have to either get a local vendor to help, research press feed circuits from some of the pneumatic manufacturers around the world, or pay me to come to China to help! I was there a few years back, and wouldn’t mind visiting again. 🙂

Cheers,

Bill