Air Compressor Problem

[Bill Grumbine]

Greetings all

The safety valve on my air compressor has been steadily getting worse and worse, blowing off almost every single time the compressor reached its maximum pressure. So, I bought a new one and installed it this afternoon. The compressor has a maximum operating pressure of 125 psi. I bought a safety valve rated for 135 psi, which was as close as I could find. When I removed the old valve, I discovered that it is rated for 145 psi!

But, I have not gotten that far. The new valve is blowing at 80-85 psi! :mad: So now I am wondering if there is more trouble than meets the eye here. Anyone here have an idea of what might be going on? I suppose I could have gotten a defective valve, but I am a little concerned about catastrophic failure too. I don't want the next post under my name to be something my wife has to type, if you get my drift. ;)

Bill

[Al Willits]

Sure your gauge is right Bill???
I'm assuming the safety valve is non adjustable.
Al

[Bill Grumbine]

That is what is concerning me at this point Al. The old valve would blow pretty regularly at the point when the compressor would reach its max pressure, but a lot of times it would blow at the low end just as it kicked on. Now I am wondering if the gauge is way off and I have been providentially preserved. I hate pitching tools for something seemingly small, but this thing has seen hard use for almost eight years now, and while I think it should last longer than that, it is a "homeowner" level machine. It might be time to buy something a little more serious.

Bill

[Don Bullock]

Sure your gauge is right Bill???
Al

That would be my guess as well.

[Richard Keller]

Bill,

At the end of the fill cycle, your air compressor should "blow off" a little air. Between the cylinder head and the tank (usually screwed right into the tank) is a check valve. This valve prevents presure from remaining on the head after compresson. Once the cycle is complete, the air between the head and the check valve is "blown off" - basically so the compressor can start again next time it needs to. If the cylinder head was kept under pressure, the motor would not be strong enough to move it. If you are finding the compressor is blowing off at other odd times, the problem could be the check valve. They can sometimes get dirt, oil, and sawdust in there, preventing proper operation. Drain all the air from the tank, then remove the check valve and see if it's stuck open.

[Jim DeLaney]

Bill,
It seems unlikely that the pressure sensor in the auto-shutoff switch (control box) and the pressure gauge would both be that far off, so it's more likely that you've gotten a bad over-pressure relief valve. Try one more before you start digging any further.

BTW, you have been draining the water out of the tank regularly, haven't you? Excess moisture can corrode the over-pressure relief valve, too.

[Bill Grumbine]

Thanks guys. Richard, there was no chance to monkey around with the compressor tonight. SWMBO was in the shop painting a cabinet, and if I did something to blow a bunch of dust around then, I would not need to worry about any problems with anything. I would be compressed!

Jim, I have a plastic tube that comes out of the bottom just for making it easier to drain the water. This thing came with a stupid valve that was so hard to operate that it had to be laid over on its side and grabbed with a wrench. I replaced it with some parts from the Borg that make it a lot faster and easier, so much so that if I get a new machine, these parts are going on it too.

Bill