compressor explosion risk

Old 03-10-22, 11:04 AM
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compressor explosion risk

So, the Youtube compressor tank explosion rattled me, since I've got a 40 year old craftsman with 20 gallon horizontal tank. Its a ASME rated compressor with 2 or 3" dia plugs at each end. The plugs have 3/4" drive so I thought it would be easy to unscrew them and look inside the tank. Well, I've got a total of 4' of breaker bar/pipe on it and its not moving. I don't see any weld spots, so it must be threaded. Any advice? longer pipe maybe
Or toss it all and get a modern/china thing....
Old 03-10-22, 12:11 PM
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Depending on the location of the plugs it is a risk trying to remove them from such an old tank. They could come out. You could rip the female threaded bung out of the tank if it's badly rusted. Or the threads can be corroded so you'll have a hard time getting it to not leak in the future.

I have never had a tank explode but I have seen a couple that rusted through and developed pinhole leaks. No explosion. Just the metal just gets thinner and thinner until one little spot blows out and you get a "Psssssssss" sound. But, just for safety the compressor in my shop is located in a cement block storage room where I do not spend a lot of time should anything bad happen.

I would also make sure your tank has a safety valve. This will open in case the switch fails and the compressor continues to run after reaching cutoff pressure. If you have a working safety valve and are still concerned you can replace the valve with one with a lower opening pressure. Or, you could add another pressure safety valve to the discharge line at the tank so you've got two protecting against over pressure.
Old 03-10-22, 03:24 PM
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Agree with PD above, air tank failures are 99.99% pinhole rust due to not being drained.
I've got a 1990 5hp 60 gallon tank, used consistently for about 10 years, then 10 in storage, returned to my shop about 10 years ago. And, since it was sitting for so long, I had the same question-

So I did a "window maker" test by filling the tank to the rim with water, (water is not compressible and doesn't store energy like air) So then I borrowed a neighbor's compressor and pressurizing my old tank to 150 psi and let it site for a couple hours. No leaks, no BOOM, so I'm good with quality control.

I DID add on an auto-water purge AND replaced the bottom wingnut-drain with a 10' air hose and cheap air gun- So now I use the 'drain' at the bottom of the tank as the air connection for blowing grass and mud off the law mower and lawn tractor.
Also for launching 2L air-water rockets with nephews or plinking targets with the brake-tubing-airsoft-caliber BB gun attachment (you didn't hear that...)
Old 03-11-22, 02:36 AM
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I also agree draining the water out of the tank goes a long ways toward preventing tank explosion. On my 40 yr old 11gallon 1 hp compressor I completely drain it after each use. My 60 gallon compressor just gets bled off when shut down at the end of the day. I've never been concerned about my tanks failing.
Old 03-11-22, 04:51 AM
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The inspection plugs on most pressure vessels use a hardening pipe thread sealant.
Yours most certainly could be held in place by rust but to remove them would require them to be heated enough to soften the sealant but not enough to alter the temper of the tank metal.
I would suggest you leave them alone and don't worry about your tank having any problems.
As said, when tanks rust they normally just leak.
Besides, you learned about this on the internet....right?
We all know the internet is always correct.....right???
Old 03-11-22, 06:41 AM
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Thinking back, the only problem I can recall was at a junkyard where somebody sheared off the 'wings' of the bottom drain plug, and swapped that out for the pop-out pressure-relief valve, which, being mounted on the bottom of the tank, eventually gunked up; somebody leaned a board against the compressor, which jammed the cut-off switch-
with all of that going wrong, what happened was that the copper pipe from the compressor to the tank ruptured, a big boom, but no shrapnel.

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