UPDATE: Air Compressor Problem

Bill Arnold

1974
Staff member
Messages
8,622
Location
Thomasville, GA
I have a 6hp, 60gal Campbell Hausfeld air compressor that has served me well - until today. When I returned to my shop after lunch today, it was running, I heard a high pressure leak, and it smelled hot. I flipped the breaker off before walking over to the compressor itself. When I tripped the breaker, I heard the usual shutdown with the unloader valve closing. The tank pressure was only abut 50psi rather than its usual 115psi. Tank pressure is holding at about 45psi now.

I'm not familiar with all of the interactions of air compressor parts. My process is to turn it on to spray stuff and do routine maintenance on it.

Am I correct in assuming the most likely culprit is the pressure switch, since it controls the unloader?

If not, what do I look for next?

While I was writing this post, I turned the breaker on to let the compressor run. Turned out kinda like going to the doctor - ran all the way to 120psi and shut down without an issue - never heard a high pressure leak like earlier. OK, so I know it didn't fix itself!

Help?!?!?
 
Any idea where the hiss was coming from? Check valve probably would be my first guess too. I've had the line going from the compressor to the tank leak as well. Sometimes works its way loose with all the heat and vibration.
 
Any idea where the hiss was coming from? Check valve probably would be my first guess too. I've had the line going from the compressor to the tank leak as well. Sometimes works its way loose with all the heat and vibration.
I do now. The compressor started running, so I walked over to check it. Pressure was still at 120psi, but it started running! I listened carefully and can hear a leak at the check valve at the top of the tank. I'm thinking the best thing is to order a check valve and new pressure switch. Will do so after a bit more checking in the morning.


check for a leak in the tank. my brother welded the small hole, and has worked like a charm since then.
No leak in my tank. Besides, that would mean I'd hear an air leak all the time. o_O
 
...... The compressor started running ............ Pressure was still at 120psi, but it started running! I listened carefully and can hear a leak at the check valve at the top of the tank.
Sometimes (not often) the safety valves fail. They're an easy first check and if it's located in the same area as the tank inlet check valve it would be easy to hear that and think "tank valve". Before disassembling, use some soapy water on joints, on the safety release valve etc and see if a leak is obvious ??

However .... the safety valve will not cause the compressor to start and run, especially if it's already at shutoff pressure. That is likely down to a switch problem.

Safety valve ::

safety-valve.jpg
 
Welding leaks in compressed air tanks is like playing with dynamite. Have you ever seen what happens when even a small 20 gallon compressed air tank ruptures? About 20 years ago, as a fireman, I responded to an explosion call where a 20 gallon Craftsman air compressor had a tank ruptured in a 2 car garage/shop. It had a leak that had been welded just 2 weeks before. The owner had to be taken to the hospital with multiple wounds from flying debris and there were no windows or doors in the garage any more. Even the metal clad door into the house was blown into the center hallway of the house. Even some of the sheet rock on the walls had pressure damage. The air compressor had been located under a work bench that was now upside down. Spilled containers of hardware and paint were dumped everywhere, and the car in the 2nd bay had many dents in it from flying debris. It would take several sticks of dynamite to do this much damage.

The leak in the tank was a strong warning, that it should have been replaced, not welded. When you weld steel, the heat from welding softens that area of the metal, so it's weaker after welding than before it was welded. If you see a home owner grade compressed air tank opened up, it will amaze you how thin the tank metal is, and at 125-150 psi, when one of these lets go you really don't want to be there. My 80 gallon 3 hp air compressor lives in a shed extension off the end of my shop. There is a 2 X 4 studded wall and two layers of 1/2" plywood between the inside of my shop and that air compressor. Access to it is through doors on the shed extension, and not from inside the shop. The air compressor is only 5 years old and has a condensate reservoir made from 3" galvanized pipe under it, so there is never any condensate sitting inside the compressor tank. This condensate reservoir has a ball valve drain that's piped out through the shed wall and down toward the ground. I open the ball valve and blow out this condensate reservoir every day that I use the shop, blowing out any condensate that might be in it. Since the Ingersol-Rand Compressor (not Chinese) was new at the time of installation, I have replaced the pressure relief a year ago (just to be safe), and I suspect that I'll be replacing the pressure switch as soon as I can get the replacement, which is on order. It failed to start the other day when the pressure dropped below it's normal starting pressure. Just a tap on it started the compressor, so it's time for replacement. I won't even attempt to clean or repair it.

I'm very sensitive about the power of an exploding air compressor tank, after seeing what happened at that fire/rescue call, and I never want to be near one when it blows. My compressor tank is four times the size of that one in the fire/rescue call. My compressor shed is attached to the North facing wall of my shop. If it does ever blow, the debris direction will be toward the lake and not toward anyone else or their property. I live on the end of a peninsula in a 180 acre lake, so unless someone is near the lake and on my lawn when it happens, I think we are safe.

Charley
 
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I do now. The compressor started running, so I walked over to check it. Pressure was still at 120psi, but it started running! I listened carefully and can hear a leak at the check valve at the top of the tank. I'm thinking the best thing is to order a check valve and new pressure switch. Will do so after a bit more checking in the morning.



No leak in my tank. Besides, that would mean I'd hear an air leak all the time. o_O
buy virtue of the fact that it went to 40 PSI and help pressure is proof that there is no leak. I'm betting on the check valve.

I am very much attuned to the power of compressed air. We had 2000 PSI air system on the submarine and we used a straw broom to check for leaks, if the air cut off the straws of the broom we knew we had found the leak. Same thing with a steam leak. :eek:
 
I am very much attuned to the power of compressed air. We had 2000 PSI air system on the submarine and we used a straw broom to check for leaks, if the air cut off the straws of the broom we knew we had found the leak. Same thing with a steam leak. :eek:

I do something similar with hydraulics, but with a piece of cardboard. A hydraulic fluid skin puncture is pretty incredibly bad.
 
Got the new parts as scheduled Monday and installed them. Ran the compressor up to full pressure and it cut off at 125psi as it should. Left tank output valve closed overnight - pressure this morning is 110psi. So far, so good. I'll check it later today to see if it drifts down more; if so, I'll start checking connections with soapy water.
 
Nope - just a manual valve. Now that you mention it, this would have been a good time to have changed that!!! :dunno:
Thanks for the reminder. The valve at the bottom of my compressor tank seems to be clogged or broken. I need to depressurize the tank and do some investigating. Unfortunately, it's on the bottom of a 60 gallon tank that's bolted to the floor. :rolleyes: On the plus side, we have very low humidity here, so I doubt there's much if any moisture in the tank. In the time I've had the compressor installed in this shop, I've never had any moisture come out of any of the other traps in the air system.
 
Yeah, not so lucky here, even worse on the southern side of this state. I installed the HF kit on mine a few years back. It seemed to do the job, but have to run an air drier on the output as well for any jobs that have it running frequently.
 
Keep a close eye on that Harbor Freight drain. My first one failed in 2 months. The second failed in 4 months. Now I have the fat pipe version of a reservoir under my 80 gallon tank and a manual ball valve and piping to vent the accumulated condensate to the outside of my compressor shed. Gravity keeps the condensate out of my 80 gallon tank and in this collection tank. Air pressure cleans it out well when I open the valve.

Charley
 
Darren,
Warm moist air rises and cooler air falls. The quicker and cooler you can get the air, the faster it will release the moisture. Get as close to the atmospheric temperature around it as possible before you draw it out of the tank and the moisture will have condensed out of this air while it's still in the tank.

At any given temperature, moisture molecules can fit between the air molecules. The most that will fit at that temperature is 100 % relative humidity. As you compress the air there is less space for the moisture to fit between the air molecules and the relative humidity becomes more than 100%, so some of it is squeezed out of the air, at least until the relative humidity is at 100%. As the temperature of the compressed air drops lower, the relative humidity again becomes more than 100% and additional moisture condenses and falls out of the air. This 100% humidity level is called the Dew Point = the point at which the air cannot hold any more moisture. When you compress the air it also becomes hotter which allows it to hold more of the moisture that it had before being compressed. Cooling this air also lowers the humidity and dew point, again causing the air to release it's moisture until it reaches 100% or dew point. The more you compress the air, the more you can squeeze the water molecules out of it, but you have to cool it too to actually get this excess moisture out of this now heated compressed air.

Moving your air outlet away from the air inlet on your compressor air tank will allow your compressed air to cool to near the environment temperature and dew point. As you draw this cooled compressed air out of the tank you will be lowering it's pressure through the regulator. Lowering the pressure will result in a higher dew point and make it less likely that any moisture will condense out of it while on it's way to your spray gun or other point of use.
 
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