double acting constantly has exaust air?

ok… this is a reletivly simple question… i hope!

we have our pnematics laid out on a board, everything is connected well and we are trying to use a double acting celenoid. Our problem is with pressure. Our tanks hold pressure when we close the pressure regulator, but when we open it our celenoid constantly leaks air prom the exaust, causing no pressure to build and the cylinder to move very slowly. Any tips?

ben lauer

The pressure regulator is set for being at 60 psi when it is completely screwed up, probably closed, When you unscrew the regulator it moves from allowing 60 psi to 0 psi when completely unscrewed open. If you unscrew the regulator you will have very little pressure working through the solenoids, You will still have the same amount of air to be pushed out the cyclinder and through the solenoid exhaust but it will do it slower because of the low psi coming from the regulator. You will want the regulator to be screwed in some if not all the way if you want to take advantage of 60 psi. This sound like a possible problem.

To be for sure, double acting solenoid works by taking air through it intake, center hole on three holed side, which should come from the regulator and being able to turn one side on (open) and the opposite sides exhaust open. So when the side that goes to the back of the cylinder is switches on to, it extends the cylinder and pushes the air on the opposite side of the cyclinder out the exhaust of the solenoid and to the atmosphere. Make sure this set-up is right.

Lastly, always be aware of leaks. I don’t think this is the case but it can’t hurt to double check. Use soap and water or fully charge the system, leave for 10 minutes and check to see if the psi is at the same level.

If you have any more questions just ask. Good luck.

no… the exaust come out the same side as the intake…

I would think that when the switch is one way, then it would only exaust until the cylinder was set in the proper position and then it would no longer have exaust.

please correct me if i am wrong.

and if this makes no sense, sorry… i am new to this.


Yeah that would be right. This is strange. Charge the system and look at the cyclinder and solenoids themselves. It would be rare to get a bad cyclinder but if there was leaking inside the cyclinder you could have this problem. If you have another cyclinder set it up and re-test. If the problem persist look to your solenoid. The exhaust is the same side as the intake. If you have another solenoid you could then change out and test another. This could even be done with the single for testing. If it works and you don’t have problems then you should order a new double solenoid. I’m not sure of all the details but it is a smc product. I would first look at a faulty cyclinder though. You can get another one from bimba if you find this is the problem.

Forgot to say, if it is the cyclinder you should be able to tell by charging the system. If the cyclinder is the problem you would still have a leak from the exhaust. But you think you would have other leaking problems. Also to speed up your cyclinder if you are using the needle valve for the cyclinder inputs, make sure they are all the way open.

Quick question: When the cyclinder is extended and the system is charged and open can you easily push the cyclinder back to retracted?

I’m really seeing it as a cyclinder problem. I would replace that one and try again for starters.

I just don’t see solenoid being that bad, but it could. If you don’t have and extra cyclinder you can use the single solenoid instead of the double for testing.

The solonoids require at least 30 PSI to work correctly - that might be your problem, or you might have it connected incorrectly - check the pnuematics manual part of the FIRST manual

its easy to check the cylinder itself - unhook the hoses and put your finger over one connector - you should be able to pull the end in and out and create pressure and suction in the cylinder

also - test it with the relay power off by pushing the little buttons on the solonoid - maybe you are powering both ends of the solonoid at the same time? To power the solonoid from only one Spike, you need to use diodes as shown in the electrical section of the manual.

one other possibility - if you are using the flow restrictors, they have to go on the cylinder, not on the solonoid - they restrict air in one direction only, and the cylinder has to be able to vent faster than its being fillled to work correctly.

Since the leak is coming from the solonoid, I’d guess that the valve isn’t seated properly. We have had trouble with this on the double solinoid in past years. Try cycling the valve manually a couple of times. There should be a little orange dot on each end of the valve. It is really a small pilot valve. Push one until the solonoid moves then push the other. There should be instructions on how to do this that came with the valve or check the FIRST Pnuematics handbook.After a few cycles it should begin operating normally.

If it continues to be a problem, check the system for contamination. Stuff like water, oil or teflon tape can get into the wrong spot and cause things to stick.

Ken’s suggestions about the electrcal side of things are also good things to check.

isnt the double valve the one with two small screws and a rubber gasket in between? maybe someone loosened the screws, or maybe the gasket is in downsidebackwards.

two gaskets…we only use one though…the other one didn’t make sense to us. Yeah, I thought it could be the solenoid only reason I think it might be a cyclinder is because he mentions how air come out of the exhaust after the cyclinder reaches a extended or retracted state. Any of these answers are potential problems. Just keep playing with it until it works.

ok…thanks everyone…

if none of this works i will ask again. i didn’t think of the fact that our cylinder could be bad…hmmmm.

thanks again

Put a pressure gage in the system after the regulator and be sure you are set at 60 psi.

Be sure the regulator is connected correctly - it has a flow direction and if is in reversed it wil constantly leak air. There should be arrows on it and air flow is “from” the pump.

Did you use the thicker gasket when putting together the solenoid? If I recall correctly, the thick one is the one we use and you trash the thinner one.

Several possibilities:

First off, disconnect the two coils from the electronics, then momentarily pulse ONE coil with just the robot battery. This will set the spool to ONE of the two sides.

If that fixes it, you probably had both coils on at the same time. Check your wiring and software.
Remember, the two coils fight over one “spool rod”. If they’re both on at the same time, the position of the spool may be indeterminate (IOW it’s possible for it to be “stuck in the middle”, where you’ll leak out of a port).

If it STILL leaks, keep it disconnected from the Spikes, disconnect the rod from what it is actuating, and check for problems in this order:

  1. Wrong/missing/imporperly installed gasket, gasket leak, and/or connector leaks (use a mild detergent/water mix or “bubble fluid” for testing, and it’ll bubble wherever you have a leak.)

  2. Incorrect plumbing to the double solenoid.

The three holes on one side, in order, are:

  • Exhaust 1 (no connection)
  • Primary Pressure (Air Input from regulator)
  • Exhaust 2 (no connection).

Each of the two holes on the other side go to one of the two ends of your cylinder via a Flow Control fitting mounted DIRECTLY on the cylinder’s air opening. The flow control fittings are Metered Out. This means when mounted directly to a cylinder that the air flows INTO the cylinder FREELY, but the needle valve controls the rate the air LEAVES the cylinder. Think of it as a rate control for rod motion TOWARD that needle valve.

  1. Something obstructing one of the air outlet paths.

The kit valves are AIR PILOTED. If you do not maintain a SIGNIFICANT differential air pressure across the valve, the spool rod may NOT switch fully, leaving you with a LEAK out of an air port.

Once you have checked that the plumbing is correct, there are no leaks, and the exhaust is unobstructed, temporarily disconnect the cylinder from the air outputs and set your regulator to a about 30 PSIG. Manually test each coil in sequence by pulsing it with the robot battery. You should hear a click each time, and air should first come out of one of the two ports on the “two hole” side, then the other. Turn off the air and depressurize the system.

Now, set the cylinder to 1/2 stroke. Turn the flow controls on the ends of the cylinder WAY IN, gently tight, THEN reconnect the cylinder. Refill the system, and set the regulator to at least 30 PSIG. Slowly open each flow control a small but equal amount until the cylinder starts steadily moving toward one end. Let it do this, and complete the stroke.

Now, as you pulse each coil with the battery, the cylinder’s rod should gently move from one end to the other.

Once THAT is working, THEN reconnect the coils to your electronics.

NOW, check each coil with a DC voltmeter, to insure you are only turning one on at a time.

Once the electronics are working, NOW reconnect it to your mechanics, and set your cylinder’s flow controls where you wish them to be.

Let me know how these tests worked out for you.

  • Keith


Were you able to solve your problem? What was the final solution?

(Closure here will make the forum more valuable for another team that experiences similar problems.)

We ended up just having to switching out the selenoid. We didn’t have any spares at the time of my orginal post, but some where donated on friday night and we switched it out with a new one and everything works wonderfully.

Thanks for all the tips and ideas.

there’s another reason why it may be leaking, when you have the black gasket and you are assembling the solenoid make sure that the a side lines up with a and b with b. there are little letters that help you to line them up, we had ours hooked up backwards and when we reset it it stopped leaking