Portable Air Tank Leaks?

I just bought a 7 gallon aluminum portable air tank, which has a short
hose with a tire chuck. It has a tire valve to fill it, a gauge, a
shutoff valve and an over-presure relief valve all mounted in a brass
manifold. The tire valve and shut-off are built into one combination
assembly and are also an integral part of the manifold.
When I first pressurized it, I filled it to 100 PSI, and let it sit for a
day, at which point it had bled down to ~85 PSI. As best I could tell,
the over-pressure valve was leaking, and it is pretty much integral with
the manifold. I complained to the manufacturer, and they sent me a whole
new manifold. I installed that a couple days ago, and it leaks even
worse. I haven't had time to figure out where the leak is this time, but
I can hear it. I'm going to try soapy water next to try to pin down the
leak.
I have a couple questions:
1) For a decent system, how well should it hold pressure? I would think
that losing a PSI a week might be more reasonable.
2) Can anyone recommend a decent source for a manifold, over-pressure
relief and tire valve filling adapter? The tank has a 3/4" NPT opening,
and if I can't fix this one, I'll just replace it with something other
than Chinese garbage. The tank itself is very nice, but it's pretty
obvious the accessories are junk.
Thanks!
Doug White
Reply to
Doug White
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You can build an new manifold from brass pipe fittings. I do this using old propane tanks and use them for air tanks. I use a POL fitting to hook to the tank valve then add a 1/4" brass cross to attatch a hose, a Schrader valve(tire valve) and a hose with a tire chuck. Notice, no safety to leak. The valve on the tank is far better than anyvalve that come in an air-tank kit. All the individual pieces except the POL fitt> I just bought a 7 gallon aluminum portable air tank, which has a short
Reply to
Gerry
I have a portable tank that I carry around just in case I need it. I haven't used it for a couple of years. You can see the pressure go up and down with temperature. But I haven't noticed any lost any air in it at all.
Is there an on/off valve that you spin by the schrader fill valve? Is it off?
Wayne D.
Reply to
Wayne
Did you fill with warm air which then cooled changing the pressure? Did you cause the leak by installing the new parts?
Reply to
Pat
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That's the type of design. The second one has a quirk, in that if you turn it too far off, it leaks out the fill port. There's a middle position where it doesn't leak (much). If you turn it out, the tank is opened to the output port, but if you turn it too far in, it leaks. The first one didn't do that, but the pressure limit definitely leaked on that one.
I've discovered that McMaster Carr sells a manifold that appears to be identical to the design of the ones on my tank. Hopefully theirs don't leak. I still haven't ahd a chance to play with soapy water to see where this one is leaking.
Doug White
Reply to
Doug White
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With the original setup, you could hear a faint hiss coming from the over-pressure valve. It's possible I introduced a leak reassembling everything, or maybe the gauge leaks, which I re-used from the first round. I used Teflon filled paste on the threads, and all the joints are pretty tight.
Doug White
Reply to
Doug White
Funny you should ask, I had to dig out my portable tank this afternoon. It's a Sears tank, same size as yours. The valve assembly is a one piece aluminum block with pop off valve (necessary item here), gage, schrader valve for filling, and a slide operated shut off valve. Pressure drop is around 10 to 15 pounds per day, all through the slide shut off valve.
My old tank was a converted Freon tank (until it tipped over and fractured the tank to vavle fitting. ) That would hold pressure for literally years.
About the only thing you can do is build a new valve block, add the pop off, shutoff, gage, and schrader valve. Doing this with pipe fittings is a mess, subject to damage. An aluminum manifold block would be a good start.
Doug White wrote:
Reply to
RoyJ
I have a commercial air compressor that I leave plugged in all the time. I don't recall the brand off-handbut I think it is something like Campbell/Clausing.
With the air hose removed (making the unit mostly like a portable air tank), the compressor will turn on 3 or 4 times a day to recharge the tank to its preset pressure.
I bought a smalller unit (Toshiba - I think) that loses 15 PSI every hour. I just assumed that pressuree loss like this was "normal".
Gary
Reply to
grice
I have a commercial air compressor that I leave plugged in all the time. I don't recall the brand off-handbut I think it is something like Campbell/Clausing.
With the air hose removed (making the unit mostly like a portable air tank), the compressor will turn on 3 or 4 times a day to recharge the tank to its preset pressure.
I bought a smalller unit (Toshiba - I think) that loses 15 PSI every hour. I just assumed that pressuree loss like this was "normal".
Gary
Reply to
grice
I moved my 60 gal compressor last weekend. It normally has 110-125 lbs of pressure. It had been turned off and unplugged since June. It still had 105 lbs of pressure.
It's an off brand sold by a local company using a rating system that is hilarious. It shows 6HP peak with a motor about the size of a 3/4 HP. It's an Emerson but under HP it shows "Special" 15A @ 220v max.
At least the tank is USA made and doesn't leak...
Reply to
Clif Holland
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That's what I figured. I removed the pressure gauge & plugged that port in the manifold. It's been holding 50 PSI for several days, so it looks like the leak was either in the gauge or around the gauge stem where I screwed it in. I have a spare gauge, so I'm going to try that next.
Doug White
Reply to
Doug White
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Thanks to the advice from various folks, my air tank has now been holding 100 PSI for a week without the slightest drop in pressure. The final solution was to crank the tank gauge in another full turn over what I had considered "tight" before. I also allowed the Teflon thread sealing paste a day to set up a bit before I applied pressure. Not sure if that helped, but it didn't hurt.
The whole process was a royal pain in the neck, because of the mechanical interference between the various pieces. The tank gauge couldn't go on until the regulator for the output was installed, and the gauge for the regulator couldn't be installed until the regulator was on. The result of swapping things in & out & testing stuff for leaks took a LONG time.
Thanks!
Doug White
Reply to
Doug White

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