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Best fix for rust hole in air tank?

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  • Best fix for rust hole in air tank?

    My air compressor tank has developed a small rust hole and I am looking for the easiest fix that does not call for a new tank. I only use this thing for filling tires. I have thought of screwing in a sheet metal screw with a bit of a gasket. I might be able to weld it, but I would probably just burn a larger hole. Any other suggestions?
    Thanks, John

  • #2
    Buzzer John, I would not repair but would replace. I know you said you did not want to do this but this is the only safe alternative. You probably have many other rust pockets waiting to break through. You have a potential failure of a pressure vessel on the horizon. Stay Safe.

    P/R

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    • #3
      If you don't want to buy a new tank, buy a used tank that is in good condition. That basically means it would pass a hydrostatic test. Rust holes are like rats, if you see one, there's many more that you don't see. Sometimes airtanks fail catastrophically like a bomb and sometimes they just leak and it's pretty well impossible to tell in advance which one it will be. There's been a few instances where a great deal of damage was done when one blew up and if you were right there when it went, you would stand a good chance of getting hurt very badly if not killed. That also applies to any innocent people nearby. It really isn't a good idea at all to try to fix a problem tank that probably has already paid for itself many times over.
      Location: Saskatoon, Saskatchewan, Canada

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      • #4
        Thanks for the comments about safety. Would an old propane tank be strong enough? I have see some made into a portable air tank, but I don't know how much pressure they hold. My unit cuts out around 100psi.
        Again thanks, John

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        • #5
          i welded the tank on one of my compressors that developed a small pinhole leak from rust about 15 years ago. if your worried about your welding just clean it real well and braze it. rust holes or welding them closed will not cause any sort of catastrophic failure. rusting weld joints actually make a tank less likely to fail dramatically due to over pressurization as the weak seams open up fairly easily and relieve the pressure. i dont offer this as hearsay or old tales. i once worked for a company that made tanks and i was involved with the testing and failure analasys of a lot of tanks. we had fixtures that blew up tanks and we did it every day. it was incredible the damage a small 20 gal .125 wall tank would do.

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          • #6
            A 20 lb propane tank will work fine. They are rated to at least 300 psi. Take proper precations to avoid igniting residual propane. Washing with solvent and then hot soapy water followed by a rinse of boiling hot clean water will work.

            Disclaimer: Some may say it is dangerous. It is but only because any vessel filled with compressed air is dangerous. Small propane tanks and small air tanks have the same steel and same construction as well as same burst pressure requirements. Actually, propane tanks are somewhat better regulated. YMMV.
            Free software for calculating bolt circles and similar: Click Here

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            • #7
              Sounds like the propane tank is my best bet. I can probably pick one up at the local gas supplier. He used to have a pile of them with the old style valve.
              John

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              • #8
                Originally posted by Buzzer John
                Thanks for the comments about safety. Would an old propane tank be strong enough? I have see some made into a portable air tank, but I don't know how much pressure they hold. My unit cuts out around 100psi.
                Again thanks, John
                Look at the collar that surrounds the valve. There SHOULD be a DOT rating stamped there, something like DOT-250. The number is the tanks safety rating in PSI. Give yourself a comfortable safety margin, say 75-100psi above what your compressor is capable of putting out and you should be fine.

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                • #9
                  An old post on the subject.

                  http://bbs.homeshopmachinist.net/sho...OMPRESSOR+TANK
                  I just need one more tool,just one!

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                  • #10
                    I'm normally very willing to go with 'fixes' but for some reason I feel that the only real fix for an air tank is replacement.

                    I had a fantastic little compressor for work (carpenter, for nail guns etc) that I really loved because it was light, and extremely quiet ( a HUGE plus when you have to listen to it all day long!) I bought it used, and had it for over 15 years, and repaired several leaks towards the end of it's life with welds,braze, and even epoxy only to have a new leak show up a short while later. When I finally stripped it down, thee were 8 repairs along the bottom. (stupid, but when I find something I like, I try to keep it going as long as I can!)
                    I finally tossed the tank, because while prepping for another repair, I noticed several divots forming where I was sanding, and saw that I could easily press a needle through them.

                    You can't tell what the inside is like without a serious inspection, and if it was rusted enough to leak in one place, there are several others that are very close.

                    Find another tank, there are hundreds of tanks tossed all the time because the motor or compressor died, save the headache, replace the tank.

                    A propane, freon, or even another air tank is great. A few years ago I trashed an old water heater, and noticed a tag on the tank itself that stated 'not to exceed 300psi" Which is about what a lot of air tanks are rated for.

                    Ken.

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                    • #11
                      id defentaly get a new tank or complet new compressor, i dont take chances with my life or the lives of others , somethings are better left to goto the scrap pile

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                      • #12
                        300 psi seems to be a minimum standard for small portable pressure vessels. Spray paint cans, 1 lb propane canisters and a wide variety of small pressurized products all meet that standard.
                        Free software for calculating bolt circles and similar: Click Here

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                        • #13
                          The main reason you can't use an old propane tank for compressed air is COATING.

                          Even though propane tanks are rated for just as much (or more) pressure, they don't have any type of anti-rust coating inside....

                          I remember years ago, a company used to make adapters to convert discarded propane tanks into air tanks. I'm sure they sold a lot of them. My brother and I used to race off road, and we had several. But, they were pulled off the market because somebody had one blow up in his face...and sued the adapter manufacturer. The reason? Rust. Air tanks, used on compressors and as portable air supplies ALL have an epoxy coating inside to prevent weakening the shell of the tank through rust formation.
                          Usually, if you see rust patches or leaks forming on the outside of a compressed air tank, it's time to discard it, PRONTO. If the rust has progressed through the epoxy coating, the tank is shot.

                          A discarded propane tank will rust up imediately, inside. And will rust through in no time.

                          Even 30 lb Freon containers are not coated inside. (BT,DT.)
                          No good deed goes unpunished.

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                          • #14
                            Hmm. Interesting about the lack of a coating inside tanks. I suppose one could coat the inside by thoroughly swishing around an epoxy mixture, but for one you couldn't see the results so you wouldn't know if there were dry spots or not, and secondly you'd want to add a water drain which would probably mean drilling at least one hole in the tank. Hmm.

                            I've used propane tanks for air without problem except for smell, but I did NOT drill or modify the tanks. It occurs to me that some mod of the existing valve might be made anyway for air use, so one could instal a tube through that fitting which would reach very close to the bottom of the tank. The tube would have a separate valve on it which would open to drain water as long as there's some pressure in the tank. If you epoxy, there's bound to be a level spot inside at the bottom, so any water would have to spread out before it could build up enough depth to exit through the tube. That leaves a significant amount of water to remain in the tank even after it has been drained. I guess you could always just turn the tank upside down to drain the water through the air valve. I dunno, I have mixed feelings about re-using propane tanks after having done that a few times. I definitely wouldn't want to be using the air inside a small room, where it could and would smell up the place with mercaptan, the odorant in propane. The tanks themselves are rated to not blow until at least 1200 psi has been reached (from my previous research several years ago) so safety factor with air at 150 psi or less should be fine.

                            Something else that occurs to me is that the remaining odorant and propane infused into the metal might interfere with the epoxy coating. If one is willing to do the work, you could spring for a new, unfilled tank, plus about ten bucks worth of epoxy, and then maybe feel a little more secure about the integrity of the epoxy coating- again, I don't feel so great about going this general route for an air tank. I also would be surprised to find that any particular air tank one could buy would be coated- I have my doubts on that, especially these days.
                            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                            • #15
                              Best fix? I could hardly guess.

                              Here's a NOT best fix:

                              I had this old hulk of an air compressor. It was a 60 gallon HEAVY tank with a REALLY heavy old (1939) compressor head and 1 HP motor in the standard horizontal configuration.

                              It had a small leak at the bottom and shed rust scales through the drain.

                              So I gave it to my old pal, Brian.

                              He said, "Hey thanks for the vacuum pump with the big reservoir." Then he slapped a simple epoxy patch on the outside, plumbed the pump in reverse and was ready to go.

                              D'oh. . . .

                              (not my first or my last, I'm sure)
                              Cheers,

                              Frank Ford
                              HomeShopTech

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