Solenoid Valve questions.
by FRANCISCO ACOSTA
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. Bill answers... 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 during machine set up, and is particularly useful when the power is off. A valve manual over-ride Is also a good way to diagnose a fault in a circuit. If an air cylinder isn't responding as it should, once you've made sure it's safe to do so, you can manually actuate the valve with the over-ride, and if the cylinder works while you are manually operating the valve, that would suggest that the fault in the 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, and internal spring inside the valve returns the spool to the de-energized location. That's a single solenoid, spring return valve. If you have a double solenoid, then the circuit designer decided that he didn't want the valve to shift back when the solenoid was de-energized. Adding the second solenoid instead of an internal spring return would accomplish this. #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. #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, un-clamps and returns to 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
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