01-30-13, 02:36 PM | #41 |
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I had the same problem last month with my project. The unit would hold pressure to about 50-75 psi, but no higher. It would eventually leak down to 10 psi or so. I eventually found the leak with the soapy water method and 60 psi from an almost empty tank of torch gas. Turned out to be a crack in a bend. I suppose at low pressure it was holding itself shut.
Hope this helps. Good luck and godspeed |
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01-30-13, 05:16 PM | #42 |
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First thing I'd try is to put a pressure gauge on the
output and a vacuum gauge on the input. Run the compressor and see if you can tell which side has the problem. Might be interesting to energize the reversing valve. Hard to tell from the picture you posted, but a corner of one of the tabs on the reversing valve mounting bracket looks like it might be pressing into one of the copper tubes. I have an ultrasonic leak sniffer that listens for the high pitch of a leak. Not sure if it will help on a low pressure leak. Also have a couple of freon and hydrocarbon sniffers that can find leaks. I'm assuming that the dryer is the only place you could contaminate with test gas, but not sure what's safe to use. I think canned air is freon???? |
01-30-13, 05:52 PM | #43 |
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Had you tryed a spray bottle with soapy water and compressed air.??Look for the bubbles. Old gas-fitters tool. Randen |
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01-30-13, 06:01 PM | #44 |
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My personal favorite is a litttle shot of propane and wave the torch around the unit. Dramatic and effective.
Randen |
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01-30-13, 06:25 PM | #45 |
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I've used Randen's method before (do it outside!).
When I was looking for a very hard to find leak on my system, I ended up trawling the bubble blowing forums for the best bubble mixture. Plain old soapy water was not tenacious enough to find the leak (I could pull a 500 micron vac and gain 1000 microns overnight). I ended up with a mix of dish washing liquid, water and glycerine. The trick turned out to be lots and lots of dish washing liquid. Like a 50/50 mix of soap/water. I just added a tiny splash of glycerine to that and put it into a squirt bottle. |
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01-30-13, 06:32 PM | #46 | |
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Quote:
-AC
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01-30-13, 06:52 PM | #47 |
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01-30-13, 08:10 PM | #48 |
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Not to get this thread too far off point, but I had been hooked up to the Internet for about a week and was trying to find some way in which it could be useful.
Well, I was drilling a hole in a motorcycle frame that was made of some really tough metal, and my drill bits kept turning blue and then no more cutting. So I tried an Internet search... I searched on the term "hot bits". Well, it turned out that hot bits was the then-current Aussie slang for porno. So I forgot all about the motorcycle frame... -AC
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01-30-13, 08:19 PM | #49 | |
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01-31-13, 04:41 PM | #50 |
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OK... well, after all my flailing failed me, I grudgingly resorted, as a very last resort, to rational thinking.
I started at my micron gauge, and tried to pull a vacuum on just the micron gauge. The readings were dishearteningly high, so I checked the fillings for tightness. Everything was OK. The gauge has a battery life graph and it looked fine, so I pulled out the 9v battery and measured it... almost a volt low. I also looked into the end of the micron gauge's fitting and saw more than a little bit of oil, so I bought a new 9v battery and some 99% isopropyl alcohol and filled the gauges thermistor cavity with alcohol, let it soak, and shook it as best I could and emptied the alcohol. I repeated this - three times, and let it dry over night. Then I pulled a vacuum on the whole unit and got down into the few hundreds of microns range (a big improvement), and capped the heat pump off. The morning after that, I hooked up my flared copper vacuum tube (I use this instead of expensive vacuum hose) to the vacuum pump, and I pumped down the line, then I opened the valve to the heat pump that had been pumped the night before, and there was no jump in the vacuum gauge, so I think that the vacuum is good. All of which makes me question my previous results with the air compressor, etc. I think that I may have a questionable Schrader valve core in the heat pump. This will be easy to replace. Also, the refrigerant valve that connects to the 1/2" line was persistently leaky, but now it doesn't seem to be. I'm really not happy with this possible answer, but it may be that all the working, opening & closing, had the effect of re-seating an O-ring. Whatever it was, it does seem to be holding. Darn, I was looking forward to doing randen's flame test, too. Through all of this, I have not been using new, fresh vacuum pump oil, so new oil should make a big difference. Thanks for the suggestions! Best, -AC
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