How long should a small portable air tank be trusted? Bought a cheap on 15 years ago and wonder everytime I fill it. Pressure release seems to work (moves easily when I pull it) and there are no dents or rust on the outside. Yes I know they rust from within, that's my concern. max PSI is 125 on the gauge, I don't go over 110.
I too would like to know what to do (and when to do it) with my old portable tank so as not to blow myself or anyone else up...
I've generally filled it from my air compressor with a moisture trap in the line, but I've also noticed that said trap rarely seems to trap anything...
The expiry date on mine is from several years ago, and the one at the shop that was built before the safety nazis took over the world is even older.
Its only 125 psi. It won't hurt that bad when it ruptures. Probably.
If it is rusting out you won't have a catastrophic failure, it will just start leaking.
Hal wrote: If it is rusting out you won't have a catastrophic failure, it will just start leaking.
That's actually good to know. I've been filling mine at the local quickie mart, and I can feel the water coming out of the line every time I disconnect to change my grip.
Hal wrote: If it is rusting out you won't have a catastrophic failure, it will just start leaking.
Is this first hand knowledge? I am not trying to be arguementative but I could see that not always being the case...
Streetwiseguy wrote: The expiry date on mine is from several years ago, and the one at the shop that was built before the safety nazis took over the world is even older. Its only 125 psi. It won't hurt that bad when it ruptures. Probably.
Ever see what a 125psi (compressed gas) explosion can do? We were taught thermo by a fellow who was working in a shop as a teen when the air compressor blew - paralyzing him below the waist. He had an interesting perspective on compressed gas safety.
A hammer is a convenient, if imprecise, inspection tool for air tanks. Drain the tank of air, so nothing exciting can happen. Rap it with the hammer along the bottom, where it may rot out. Nothing should happen. But hit a thin area, and you'll dent it or may even punch through it.
I am not saying it is safe or not.. but I have seen a couple go.. they always seem to just split a seam.. usually at the bottom.
I deal with airtanks in Confetti Cannons. I cannot tell you how many times I have seen rental tanks with a large amount of water in them. One I drained and got about half a litre out of. Needless to say I sent a note back to the rental company about it, not that it seemed to make a difference
Hal wrote: If it is rusting out you won't have a catastrophic failure, it will just start leaking.
Rust is the enemy of air tanks. I had a home air tank start leaking due to rust, after 18-19 years. I have a portable air tank that I have used for 15+ years and have never found water in the tank. I do fill it at home 90% of the time for use at the track and at the track if I need air it's usually from the compressor that the tire guys at the track use so it has a water seperator as I do at home.
A catastrophic failure of an air tank can happen but most likely it would happen at a welded seam. The cause would be either a failure of the weld (not likely if the tank is a used tank and not over pressured.) or due to internal rust. In the latter case there would be some evidence of rust pryor to the failure. A regular inspection of the tank both internally and externally should catch this before it would lead to failure.
Checking a tank for moisture and removing it on a reuglar basis should be all thats needed.
On my home air compressor tank that rusted out, I sourced a used tank that was then cleaned internally, removing a light coat of rust. I then poured in some epoxy piant to seal the inside of tanks surface.
now you bring up a good question. My standup huskey compressor has died.. it cannot pump up more than 65psi.. any ideas where I can get a new compessor for the still very good tank?
If you're regularly draining excess water out so there isn't a puddle preventing coverage, does the same danger of oil mist in a non-oilless compressor which so annoys painters provide any hope of corrosion mitigation in the tank?
EDIT: Of couse, I have a semi-cheapie oilless compressor, but it's getting on in years, and I'd eventually like to change to a larger vertical compressor that's not in my ear so much...
RossD wrote:Hal wrote: If it is rusting out you won't have a catastrophic failure, it will just start leaking.Is this first hand knowledge? I am not trying to be arguementative but I could see that not always being the case...
I have seen two rust out. In both case they just leaked. One was one that I had bought used. About the 3rd time I went to use it I could hear it hissing when I shut off the compressor. It had rusted thru on the bottom and the pressure blew a hole ~1/16" in diameter in it.
I have seen one catastrophic failure but that was a home made tank. Guy used a large diameter piece of iron pipe and welded ends on it. Crappy welding, first time he put air in it one end blew out. The end plate didn't completely detach, there was ~2" where the weld held and the rest of the plate bent out about 30 degrees. He was using a large induatrial compressor to fill it to test. I don't know how much pressure he had in it but I assume it was a lot more than the usual 125 psi.
Testing of pressure vessels is NOT done w/ compressed air. A hydrostatic test consists of filling the vessel w/ water, submerging it in a big tanks of water, and adding compressed...water.
You can do it yourself w/ a porta-power.
When a pressure vessel fails the test when it's filled with a nice, incompressible fluid, there's not a great deal of potential stored energy to blow the windows out of the building as would happen w/ compressed gas. I'm talkin' big tanks w/ upwards of 2500psi, but it translates.
Small portable tanks don't see a fraction of the moisture a full size compressor sees in a humid climate. If you're concerned, turn it upside down so the gazoutta is on the bottom and release the air, effectively draining the tank - after each use.
I have a 2hp 20-gal 5.2 CFM portable compressor I bought new in 1987 that still runs great and looks new, absent a bit of dust. It holds pressure and doesn't make any strange noises. It has always been stored inside and the tank has been drained after each use. During the shutdown draining process, a small bit of water may come out but it is clear, no rust staining present.
Because of it's age, I have lately become worried that maybe I should replace it rather than risk a tank explosion. Has anyone given thought about building some kind of containment cage, in the event of a catastrophic failure. I'm thinking perhaps of a welded frame with chain link fabric. Has any one done something like that? If so what did you do?
Hydro testing seems like a great deal of work, if the tank turns out to be as sound as I think it may be. What are your thoughts and advice?
Thanks, Rich909
In reply to njansenv :
Most compressed gasses, are much more than 125 psi
I've never heard of an expiration date on an air compressor tank. 
'Course I've never wanted a slice of toast while taking a bath, but that a whole 'nother thing.
I've had old rusty air tanks (from 90 psi, to 160 psi) start to leak. The leak usually gets worse over many weeks. I think he will have time to avoid harm.
YMMV
In reply to motomoron :
With the "square inch" in psi being an important part, those really big tanks (with a lot of square inches) don't relate to a hand held tank, even if they "only" had 125 psi in them. Neither would a same size tank, with 2500 psi. So apples to oranges, from a safety perspective.
Again, not a recommendation, just an opinion, based on science and experience.
03Panther said:...I've never heard of an expiration date on an air compressor tank.
Maybe not actual compressor tanks, but I have seen "destroy by" dates on portable "pig" tanks.
+1 for experience where a consumer-grade compressor tank simply starts leaking when it rusts thru, rather than anything worse.
In reply to Oapfu :
I was only using "air compressor" tank to differentiate from the high pressure gas cylinders some are thinking are comparable.
I never looked at the portable tanks that close, and most I've been around have been older (or worse, home made!)
Just seems as silly as telling folks not to use the toaster they just bought, in the bathtub (Yep. Seen that in writing, before)
Now I need to check my portable air tank when I get home. Think I bought it in 2011, should probably check for any dates.
My compressor is 53 years old. The tank was originally tested to 300 psi. I run it at 125. I mostly don't worry about it. It is a Quincy. If it was a consumer grade it would probably worry me more.
Portable air tanks, like the one you bought 15 years ago, generally have a lifespan of 10-15 years, depending on usage and maintenance
Just a few of the air compressor explosions on YouTube:
https://www.youtube.com/watch?v=sm_FJ6Pat4I
https://www.youtube.com/watch?v=mgLiRAa-1qM
https://www.youtube.com/watch?v=-y8ujgzM94c
https://www.youtube.com/watch?v=KVP_A7eGYxw
Why take a chance. If in doubt, replace it.
Jerry said:Now I need to check my portable air tank when I get home. Think I bought it in 2011, should probably check for any dates.
I found a 06.2012 stamped into the foot of my 5gal tank I use at events. Might be worth replacing.
In reply to so_slow :
Yep. Boob toob . Along with Jackazz movies, is where everyone should go for safety advice.
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