Compressor leaks down..... grrrr

My compressor is a 30 gallon Sanborn. Other possible leak sources would be the pressure switch diaphragm or the manual pressure release. A pinhole in the diaphragm or a bad gasket would be hard to spot. Other possibilities are the main pressure gauge or the pressure regulator. Again, internal leaks would be hard to spot.

An 80 gallon tank holds about 10 cu. ft. or some 100 cu.ft. of uncompressed air. A leak down time of 50 hrs. would be around 2 cu. ft./hr. which is a fairly substantial leak. I would use a mechanic's stethoscope to try to locate the leak. Not having a stethoscope, a length of flexible tubing will work.


This morning I leak tested the output line by putting an MT 3 taper dead center over the hole and spraying it with soapy water, no leaking there.
Also, I disassembled the overpressure spillover for inspection and cleaning, all seemed OK there. Also, I took Jack's
recommendation and tightened the 6 Phillips on the bottom of the pressure switch assembly. It's up to pressure now at
165 pounds so will go out to the shop again and listen with some flexible tubing. Time will tell if it's leaking as it has been cycling about twice a day
with no usage...
 
There is a main valve that I shut off to prevent my overhead lines from leaking down as there are many threaded connections and probably
50 or so feet of pipe. With the main shut off, I could detect a tiny bit of air coming from an air nozzle by feeling the cool on my tongue. :p The leak was
not detectable by ear at all. Apparently I need to replace the seal on the main outlet valve. I also noticed that if I tightened up the valve very tight,
the leak was all but undetectable. I will check my gauge in the morning but I am pretty sure the valve is at fault. Sometimes it takes the
"process of elimination" to get to the root of the problem.

What is the most secure valve to use that will not leak? My thoughts would be a water line type valve sealing with rubber or possibly
a ball valve, certainly not a gate valve.
 
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I have had better luck finding air leaks using a piece of hose or large diameter tubing held to my ear and probing likely areas than by using soapy water. And I am about deaf. (it helps if the area around you is quiet).
 
What is the most secure valve to use that will not leak? My thoughts would be a water line type valve sealing with rubber or possibly
a ball valve, certainly not a gate valve.

Where I live there's a business that specializes in compressor sales and service. If you have someone near you like that, you could just call and
ask what they use.
 
A ball valve with stainless steel ball will have the least flow resistance and is least likely to have problems with debris. The former occupant of a building we once rented used ball valves for all of their test gas lines.
 
I've had a few ball valves leak in my system I used for isolation, I just pulled 3 out of the lines. I now run a single ball valve at the tank and took out the unneeded quick connects I had everywhere.

My leak was mainly from the older air/water separator I got off eBay. Sometimes it would seal up, but many times it would leak air out the auto drain. I went with a new 3/4" RapidAir regulator/filter set up since I use a 3/4" Maxline system. Its leak free and holding back the 165 psi just fine so far. Its actually working good, air is much drier than the old unit.

I also had a problem with the unloader valve, replaced mine recently. My Ingersol Rand 80 gallon has the valve built into the electrical switch. $80 replacement. I can't complain though, my IR compressor from Tractor Supply was only $899 and its over 4 years old. I run it almost everyday fairly heavy. Surprised its held up so well. Highly recommend the RapidAir Maxline system, haven't had a leaky fitting yet.
 
Another vote for a ball valve with stainless ball. They work very well.

When I took care of compressed air systems for a previous employer, they allowed me to purchase an ultrasonic leak detector. It was very expensive, but the energy savings that were realized from having a leak free system paid for the tester in no time. It also came in handy for diagnosing leaky or troublesome steam traps in the production heating systems. It was capable of finding nearly imperceptible air leaks from better than 20' away. I could also scan the entire plant air system for leaks on a monthly basis in just over an hour.
 
Replacing my air valve would have required cutting off the pipe and using a union to reassemble with a new valve.
Not wanting to do this, I machined a piece of white UHMW(ultra high molecular weight) plastic into a cone
shape with center hole and installed into the existing valve. This fix has been holding air pressure for days so will
call it good enough and save the ball valve for later use.
 
My compressor leaked down because the check valve that releases the head pressure was filthy and would not seal. I was lucky that my check valve came apart so I could just clean it and put it back together. I know some of them do not come apart and must be replaced.
 
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