Opening a big compressor's tank INSPECTION HOLE

Sitting for a while with water inside should do it less harm than being used frequently with water inside. While it's sitting, the corrosion that can occur will be limited by the amount of oxygen in the tank. Do the maths and this won't add up to a great deal of corrosion. It's the same principle as a central heating system with pressed steel radiators; they don't corrode much as there's only a limited amount of oxygen in the system. So don't worry about corrosion on the inside due to it standing.

Chris

Sure, it isn't good when water sits in the tank. But my venerable Quincy puked a good quart or two of rusty water several years ago when I got it going, and I figured one of these days I'd have to replace the tank. Well, it's been 5 years so far, it's holding up fine.

GWE

Ignoramus29516 wrote:

In CA compressed air tanks are required to undergo periodic inspection. The inspector scraped a little paint off the tank, attached a small magnetic sensor to the tank and took a reading. He said in the old days they had to pull the inspection plugs, and use large, very expensive micrometers to measure the wall thickness.

You may also consider hydro testing. They fill your tank with water and if it will hold 600 PSI they will certify it for 300PSI.

They use water so if the tank ruptures the pressure drops to zero before the shrapnel starts flying. The local welding supply place might be able to do this for you.

Thanks for the encouragement. The thought of a 100 gallon behemoth exploding next to me was disconcerting. While the compressor was sitting, the air valve was open, so some minimal amount of oxygen culd enter it through that.

i

Thanks. I must note that the day when it stops holding fine, could be the last day when we see your posts (hopefully that does not happen), so you won't be able to reach us from heavens and say, guys, on such and such a day my tank did go bad after all. Again, I am hoping that it does not happen to you or me.

i

I buy stuff, but I sell it too... The 2HP compressor that I repowered for single phase, in on sale on ebay right now... The tractor I will sell also, after I fix it up a bit. I make a little $$ and learn a bit with every new thing.

My shop is my garage and part of basement.

i

Very interesting. What are these sensors called if I wanted to buy one?

i

Why is that a concern? Every such tank is always filled with moist, condensing air when it is in use. I don't see why a puddle at the bottom should make that any more corrosive.

I didn't realize you were that damn wealthy to be able to afford an ultrasonic thickness gauge! They start just below a grand and head up fast depending on what material you're trying to measure and so forth.

You'd be money ahead to find a place that can do it for you. Don't know what kind of place that would be, but perhaps ask and industrial supply who uses them.

Yes, those I have seen. In fact, I owned some ultrasonic military surplus gizmo that originally cost $4k that I sold on ebay.

Thanks Carl. I thought that the OP talked about some sort of magnetic sensor, not ultrasound.

i

| > uses them. | >

| | Thanks Carl. I thought that the OP talked about some sort of magnetic | sensor, not ultrasound. | | i

Oh, and if you want to, it might be worth having the inside of the tank sealed as well. You can have it done, radiators shops can do it, or you can buy kits from Eastwood and do it yourself. The DIY kit likely doesn't cost that much, either, relatively speaking.

There are and were all kinds of sensors that do that sort of thing. Ultrasonic is the most accurate and most modern method nowadays. Out in my tool chest I have what's called a pit gauge, which is a cool tool for measuring the depth of a pit or depression, originally for the inside of a boiler. There's a lever that shows the pit depth is % for different thickness walls, in addition to the raw depth figure. You obviously have to be inside the boiler to use it, so I imagine it was a rather unpleasant job!

The old boiler guys have little hammers they go around and ping on the walls and listen to the thickness of the vessel wall. That's a real skill!

From everything I've ever read, tanks explode only when they're poorly welded and the safety shutoff valve isn't working so the compressor continues to run until total failure. All other failures I've read about happen via pinprick holes due to age/rust or from things falling on them, knocking bungs out of them, or puncturing them. I wouldn't worry about it, Iggy. Opening that peep hole will only allow you one more potential leak. Rustout is probably the safest failure mode you could have.

Besides, if one did explode from a deweldment (izzat a word?), it would only blow the windows out of your house (and maybe your eardrums.) after a 2 or 3 atmosphere pressurization.

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I did that once. I made a clamp-on "wrench", with a long handle made of

1" Sch 40 pipe. When the pipe bent (!), I said "Screw it". Bob

Usually rust makes pinholes that leak air long before there is any danger of a rupture.

Thanks, Larry, Carl, and others. The compressor is working. I set it to cut in at 130 PSI and cut out at 160 PSI. My only problem is that there is a strange valve whose purpose I do not understand, and a plastic fitting witha plastic hose going to another plastic fitting, that became broken during transportation. On one side the fitting is

1/4", (I replaced it with 1/4" Home Depot fittings), but on another it looks like it may be metric. It works, but leaks air from a crack. So, I may need a fitting with metric thread and 1/8" barb. No idea where to find such a fitting. i

I never let the size of my shop limit what I try to put in it!

That's probably the head unloader, a valve which takes the pressure off the head when the tank has air in it and allows the compressor to start without blowing fuses/circuit breakers. Copper tubing might be a better fit for that purpose, but check with the mfgr.

HF had a problem with their aluminum unloader tubes and reverted to copper.

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Thanks. That's interesting. Do these kits actually work on used tanks?

That's interesting...

i