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Thread: Tank Valve Checker / Question

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    Tank Valve Checker / Question

    Hi all,

    Ever rebuild a tank valve, install it in the tank and fill, only to find a small (or perhaps major) leak? Every now and then it happens. Sucks to have to redo it. A valve checker solves this problem. I've seen the tank valve checkers for sale, but they're pretty pricey.....figured they can't be too hard to make.

    The one's I've seen are made from Aluminum. I have some 2" round stock AL, but also had Delrin as well. Much easier to work with and no corrosion. I knocked one up on the lathe in a few hours. 1/4 NPTF on one end, 3/4 14 NSF for valve on the other. It came out really nice. (see pics below) I had a short whip rated for 5000 psi made up at the local hydraulic shop, with 1/4 NPTM on each end. One end to attach to a regulator yoke with 1/4 NPTF adapter, other end screws into valve checker.

    As it is made from Delrin rather than aluminum, I am unsure of it's structural integrity. My original plan was to feed it from a regulated supply and limit the pressure to 1000 psi or so. I'm sure it can handle that amount of pressure with no issues. Then I got to thinking......

    Maybe it can handle a full tank with 3000 psi, and I wouldn't have to run through a regulator...just hook it to any nearby scuba tank. It's made from 2 1/2 " round Delrin, so the wall thickness is .75 at the valve end, and 1.0 at the input. Seems pretty stout to me, but what do I know?

    I figure there has to be a few on here with expertise on this type of thing that could shed a little light on this. Tobin, Martin, Troy???? Any engineers out there?

    I'd like to know what you think....stick with the lower regulated pressure for safety, or just use it straight up at 3000 psi?

    Thanks, FD
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    Re: Tank Valve Checker / Question

    Sorry.....somehow the bottom pics didn't rotate. I had them right when I looked at them.

    FD

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    Re: Tank Valve Checker / Question

    Not an expert, but I wouldn't trust the threading over time....

    Richie

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    Re: Tank Valve Checker / Question

    How high in the air are you planning on launching the valve? It will determine what pressure to feed the valve launcher you have built.

    Whether or not the wall thickness is sufficient for the pressure you wish to test, the small residual quantity of delrin thread material is likely the weakest element, without some form of external restraint to stop separation of valve and tester.

    One of the many old links on the net about delrin bullets and exploding tank caps.

    Plastic DIN cap warning [Archive] - ScubaBoard - Scuba Diving Forum - Diving Social Network

    Play safe!

    Regards,
    Tony

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    RBW Member Spiro is an unknown quantity at this point Spiro's Avatar
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    Re: Tank Valve Checker / Question

    Take it back to your hydraulics shop and get them to test it in their pressure test rig. might have to phone around tho as not every hose shop has pressure test rigs.

    Most parker stores should..

    I would test it for you in my test rig, but im on the other end of the globe..

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    Re: Tank Valve Checker / Question

    Getting conflicting responses. I kinda figured it might be a valve launcher too....that's why I asked. Others say no problem at all.

    In all honsety I could keep the feed quite low, say 100 or so psi.....just enough to leak test in a bucket of water. That should keep me safe. I'd only use the thing a few times a year, so I don't think the threads would wear out. I could also go back to the lathe and make one out of aluminum so I know it'd be strong enough.

    Still I'd like to hear from those with a background in this sort of thing as to what would be a safe operating range.

    Keep it coming!

    Thanks, FD
    Last edited by firemandiver; 8th February 2013 at 02:58.

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    Re: Tank Valve Checker / Question

    I used to use the delrin din valve caps on my tanks but one time when I was in a hurry I picked up the tank by the hand wheel. The hand wheel spun and the cap exploded sending pieces of the cap under my skin and about an inch upward. It was painful to dig them out but it could have been my eye.

    Rick

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    Re: Tank Valve Checker / Question

    If you look at the material strength of delrin compared to brass or aluminium then I think you're asking for problems pushing HP air through that.

    Keeping the pressure under 10Bar may prove to be OK but why take the risk?

    http://www2.dupont.com/Plastics/en_U...ign/DELDGe.pdf

    Brass Mechanical Properties

    ASM Material Data Sheet
    Last edited by steveharriss; 9th February 2013 at 08:52.

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    Re: Tank Valve Checker / Question

    Quote Originally Posted by firemandiver  View Original Post
    In all honsety I could keep the feed quite low, say 100 or so psi.....just enough to leak test in a bucket of water.
    I dont think 100psi will answer the problem. I've had valves be ok at low pressures, but then leak at high pressure. It generally seems to be the teflon bushings on the valve stem. I'd work on a setup to test to the full working pressure.

    Same design, but in brass or aluminum would probably do the trick!

  10. #10
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    Re: Tank Valve Checker / Question

    Quote Originally Posted by OceanOpportunity  View Original Post
    I dont think 100psi will answer the problem. I've had valves be ok at low pressures, but then leak at high pressure. It generally seems to be the teflon bushings on the valve stem. I'd work on a setup to test to the full working pressure.

    Same design, but in brass or aluminum would probably do the trick!
    Agreed... I've had a few valves hold pressure at 500 - 750 psi only to develop slow leaks at high pressure.

    Richie

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