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sprinkler leaking through pilot exhaust when pressurized

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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sprinkler leaking through pilot exhaust when pressurized

Unread postAuthor: mfalconer » Fri Jan 07, 2011 9:33 am

Hi everyone,

I have recently built a pneumatic cannon w/ a modified blow gun attachment. However, next... I want to build a remote control cannon using the solenoid with an Orbit 1" sprinkler valve (i.e., no blowgun modification). Everything is going good except I can't get the pilot valve to seal. When I pressurized the tank, air starts coming out of the pilot exhaust (i.e. the little oulet port on the barrel side of the sprinkler).

Has anyone ever had a problem like this? I figure the leak is somewhere in the solenoid housing. I might just buy a new sprinkler and try again.

Thanks

mfalconer
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Unread postAuthor: omniscient » Fri Jan 07, 2011 11:43 am

Two things, off the top of my head:

1.) You could have either (accidentally) put the sprinkler valve on backwards (been there-done that) or
2.) Pressurizing the chamber-side too slowly(With a bike-pump or small air compressor starting from zero-pressure.
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Unread postAuthor: mfalconer » Fri Jan 07, 2011 1:40 pm

Thanks for the reply

No, the sprinkler valve is attached correctly (i.e., arrow is pointed towards the barrel). The gun fires fine, but the air leaks out of the pilot exhaust valve stem, so you need to fire it before the air all leaks out.

I'm not sure what you mean by # 2... how would this make a difference?
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Unread postAuthor: Mr. Potato Head » Fri Jan 07, 2011 5:39 pm

Make sure the bleed valve is closed. I'm not sure which position the switch should be but try both and see. If that doesn't work try taking it apart, cleaning it, and then putting it back together. Mine wouldn't want to seal several times because of debris in the valve.
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Unread postAuthor: omniscient » Sat Jan 08, 2011 12:28 am

mfalconer wrote:Thanks for the reply

No, the sprinkler valve is attached correctly (i.e., arrow is pointed towards the barrel). The gun fires fine, but the air leaks out of the pilot exhaust valve stem, so you need to fire it before the air all leaks out.

<b>I'm not sure what you mean by # 2... how would this make a difference?</b>


You cannot pressurize a sprinkler-valve actuated pneumatic cannon with a "bike pump", for example. There is too small a volume (at too slow a rate of fill) to pressurize the top of the diaphragm. - As you are pumping air into the Chamber, the air (at such a small rate of fill) simply bleeds out of the equalization port. You need a larger cfm at a higher initial pressure, to instantly equalize both the upper and lower portion, to begin filling your chamber. Which also brings me to yet another suggestion;

An ORBIT Water Master Valve has a small plastic screen that is attached to the rubber diaphragm, right through the pilot hole. As near as I can figure, it is nothing more than a screen, which keeps debris from entering into the upper portion of the diaphragm.

Take a pair of wire cutters and <b>carefully</b> snip this piece off. - I have had the same problem getting the pilot to seal properly, with this component still in place.

Mr. Potato Head wrote:
Make sure the bleed valve is closed. I'm not sure which position the switch should be but try both and see. If that doesn't work try taking it apart, cleaning it, and then putting it back together. Mine wouldn't want to seal several times because of debris in the valve.


Excellent addition! Please try this, as well.
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Unread postAuthor: Mr. Potato Head » Sun Jan 09, 2011 12:33 pm

You cannot pressurize a sprinkler-valve actuated pneumatic cannon with a "bike pump", for example. There is too small a volume (at too slow a rate of fill) to pressurize the top of the diaphragm. - As you are pumping air into the Chamber, the air (at such a small rate of fill) simply bleeds out of the equalization port.

hmm....
I'll have to argue with you on this one. Having a small fill rate isn't at all bad in terms of valve operation. In fact the opposite is true. If you have too high of a fill rate the pressure won't have time to equalize through the tiny equalization port, thus causing the valve to open. Just to back up my claims, consider my first canon. It has a pretty large chamber yet i managed to bring it up to 50 psi with a shock pump. That took forever cause of how low volume the shock pump is, but it worked.

Edit: my iternet is being dumb right now, but I'll post a pic soon
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Unread postAuthor: Hubb » Mon Jan 10, 2011 5:54 pm

If the solenoid is still attached, check to make sure it is properly functioning (i.e. the spring is working correctly) and make sure the bleed valve is closed. If that is good, then you may have tapped the pilot valve correctly, and this can usually be fixed by adding more teflon tape or putting epoxy around to help seal it.

You cannot pressurize a sprinkler-valve actuated pneumatic cannon with a "bike pump"
I've pressurized pneumatic sprinkler valve cannons with bike pumps numerous times, so this statement is incorrect.
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Unread postAuthor: Davidvaini » Mon Jan 10, 2011 8:31 pm

omniscient wrote:
You cannot pressurize a sprinkler-valve actuated pneumatic cannon with a "bike pump", for example. There is too small a volume (at too slow a rate of fill) to pressurize the top of the diaphragm. - As you are pumping air into the Chamber, the air (at such a small rate of fill) simply bleeds out of the equalization port. You need a larger cfm at a higher initial pressure, to instantly equalize both the upper and lower portion, to begin filling your chamber.


idk if this has ever been said or suggested, I don't really have time right now to read everything.. but....

If you are having a problem supplying the air fast enough but you still want to use a bike pump or something of that nature, then Id suggest putting a Ball valve between your air tank and your sprinkler valve.. that way you can fill it up with the ball valve closed.. then open the ball valve and that should be fast enough and high enough airflow (cfm)

I myself have never filled one with a bike pump, only a co2 inflator, I was having some problems with that, but Ive always had bad luck with sprinkler valves leaking
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Vlave leak

Unread postAuthor: Oppertech » Mon Jan 10, 2011 9:02 pm

Hey Falconer, the problem is, on the diaphragm on the inside of the valve, there is a small hole in the center of the plastic piece in the middle of the seal. Air will leak through this and you can plug it with a small screw, I just had that problem, hope this helps!
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Re: Vlave leak

Unread postAuthor: Oppertech » Mon Jan 10, 2011 9:03 pm

Oppertech wrote:Hey Falconer, the problem is, on the diaphragm on the inside of the valve, there is a small hole in the center of the plastic piece in the middle of the seal. Air will leak through this and you can plug it with a small screw, I just had that problem, hope this helps!

BTW if you cant figure it out I would be happy to take apart a valve for you and post some pics for people with the same problem, Thanks
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Unread postAuthor: Vincenzo » Mon Jan 10, 2011 9:06 pm

If you plug that the valve won't equilize and it won't seal, which would make the problem worse :wink:
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Unread postAuthor: Oppertech » Mon Jan 10, 2011 9:08 pm

Nope, on the center of the diaphragm, there is a small pinhole on the circular plastic peice right in the middle, it will leak air into the barrel if not sealed. This may not be the problem, but it's a good thing to check while the valve is still open. This pinhole is in the middle of the plastic piece that seals the valve end of the barrel off from the chamber pressure, you'd need to take the top off the sprinkler valve. I recently had the same problem and figured out that it was actually air coming from the center of this plastic seal, not the pilot valve, hope this is useful, my first post so I'm itching to help someone out :o
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Unread postAuthor: Lockednloaded » Mon Jan 10, 2011 11:49 pm

Oppertech wrote:Nope, on the center of the diaphragm, there is a small pinhole on the circular plastic peice right in the middle, it will leak air into the barrel if not sealed. This may not be the problem, but it's a good thing to check while the valve is still open. This pinhole is in the middle of the plastic piece that seals the valve end of the barrel off from the chamber pressure, you'd need to take the top off the sprinkler valve. I recently had the same problem and figured out that it was actually air coming from the center of this plastic seal, not the pilot valve, hope this is useful, my first post so I'm itching to help someone out :o


are you sure you didn't have a chamber sealing valve? was there a guide rod on your top? barrel sealers shouldn't have a hole in the center
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Unread postAuthor: mfalconer » Tue Jan 11, 2011 11:20 am

ok I found the leak culprit. Its the tiny black o-ring in the underside of the valve lid. It has a crack in it. I tried going to the hardward store to get a replacement but they dont have the exact size I need. So I contacted the company that sold me the sprinkler valve and they agreed to send me a replacement o-ring in the mail.

Anybody else know of a good place to buy o-rings (w/ good selection)? I think most hardware stores (Home Depot etc) don't have a good enough selection... what about bearing supply companies?
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Unread postAuthor: Technician1002 » Tue Jan 11, 2011 12:44 pm

Find a shop that does hydraulics and Pneumatics. Hydraulic hoses have to be replaced often on heavy machinery along with o rings in control valves and such. They are an excellent resource.

Near me a place called Oil Filter Service Company is one of this type of shop. Look for a similar shop in your area.

If I need any type of high pressure hose, they are the place to go. From Hydraulic, to pressure washer, to power steering, to auto AC, or whatever. They got the tools and supplies to make a replacement.

They have a large selection of O rings too.
http://www.yelp.com/biz/oil-filter-service-company-portland
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