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welding an air tank?

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  • welding an air tank?

    Hey ... this probably sounds like a dumb idea, but I was thinking of welding an air tank out of 1/8" steel.

    That would be much thicker than store-bought tanks, and I would even be able to treat the inside with rust-prevention compound -- like the rust-proofing they use on cars.

    I think to bend the steel into a cylinder would be very difficult, so the best way to do it would be a 16 X 16 X 48" box, which would be about 53 gallons.

    I know that a square box isn't as strong as a cylinder, but with 1/8" steel, it should be overkill, right?

    What do you think? Criticism and suggestions are welcome!

  • #2
    The variables are based upon your skills and your ability to test the stenght of the tank.

    But by the time you you have the steel and welding equipment together, it maybe cheap to buy a used tank.

    Just my thoughts,

    Jerry

    Comment


    • #3
      I welded up a tank 25 years ago to use in a wood boiler, i made it from sheet 1/8" plate. It was 24x24x3" thick. I pressured it up with air to test it and the sides pushed out like a big fluffy pillow, now it is 6" wide in the middle. Needless to say i didn't use it but it didn't leak either.
      This is just my opinion, i would not build a tank today because of the liability if something did happen even way years down the road unless you are certified for pressure vessle work...Bob
      New tanks aren't that expensive from even Graingers.
      http://www.mcmaster.com/ PAGE 891 Air Tanks
      Last edited by aametalmaster; 09-18-2006, 06:46 PM.

      Comment


      • #4
        Ok ... that was a bad idea ... my apologies :-)

        Comment


        • #5
          If you're thinking of making your tank to save money,........don't. But if you need a custom size then try it if your welding skills are up to par. If it is a square and you don't want it to pillow out maybe you could put a rod through
          it and weld the ends or just use heavier plate. I would restrict this idea to small tanks like on a motorcycle or small project. Tank failure danger would probably be in proportion to its size. Persons using old freon tanks and such
          being discouraged is because of the internal rusting and weakening of the tank from moisture from compressing moist air. The tanks are capable of holding pressure greater than most home shop air systems plus they have a pressure safety on them. What will go into the tank and at what pressure is the key issue. I would much rather be around a small tank that failed than
          a large say 80 gal that burst. There is a lot of kinetic energy there. Be careful.

          Comment


          • #6
            Originally posted by monte55 View Post
            I would much rather be around a small tank that failed than a large say 80 gal that burst. There is a lot of kinetic energy there. Be careful.
            I would not want to be around ANY air tank that ruptures. Have you seen pics of then after that exploded? Plus they can throw shrapnel when they explode.
            Heres some pics of one. Looks like it rusted out then went KABOOM
            http://www.doli.state.mn.us/airtank.html

            Comment


            • #7
              yeah ... I'm definitely not going to try to weld an air tank ... that was just a bad idea all around. A few days ago, I found those same pics you linked to and didn't like the look of it at all!!

              Notice that they mentioned that the drain valve was removed and the outlet was plugged up. That's obviously why it got so rusty in the first place. Me ... I did the exact opposite. On my little dual-tank nail-gun compressor, I put two ball valves on it so that I could drain them more easily. I always drain them after each use, and tilt the compressor around to make sure all the water is draining out.

              About the freon tanks ... I've been thinking of ganging together a few of the disposable tanks ... they are rated at 250 psi, which is 50 psi greater than the store-bought compressor tanks. The only downside is they have no plumbing for a drain valve. So ... perhaps I can carfully weld in a drain valve there. I haven't decided yet.

              Thanks for all the input ... and keep the ideas coming!! This is very helpful.

              Comment


              • #8
                Robert,

                Have you thought about seeing if your local bottle gas place has gas bottles and or vessels that don't meet pressure standards, they would make great bottle for 200psi.

                I have never done this, so I am not if it will work, I just thought I throw out this idea.

                Jerry

                Comment


                • #9
                  Originally posted by jfsmith View Post
                  Robert,
                  Have you thought about seeing if your local bottle gas place has gas bottles and or vessels that don't meet pressure standards, they would make great bottle for 200psi.

                  I have never done this, so I am not if it will work, I just thought I throw out this idea.

                  Jerry
                  Yeah ... I called a welding supplier and they said the largest they can get are some 4-foot by 7-inch scrap bottles for $15.00. Those are still pretty small by compressor standards, so I'm thinking that ganging the free freon tanks together might be a better option.

                  If I do go with the freon tanks, I'm going to spray the inside with some kind of rust preventative. I'll have to be able to get a wand in there or something. Or maybe I can use an agricultural sprayer to get inside and coat it with something. Anybody have any ideas what kind of spray would work well for that? Paint? Rubberized undercoating (not the oily kind)? Other ideas?

                  I think the key thing is to take proper care of whatever tanks you use.

                  Comment


                  • #10
                    I would just use a good primer and some oil base paint, pour it in the valve hole, coat the inside, then turn it upside down to drain and air out. If you want to get real fancy use some POR15 gas tank sealer that stuff is tough as nails...Bob

                    Comment


                    • #11
                      If you go with painting, rubberizinf or what ever to preserve these tanks, have a really good output filter on this arrangement, maybe even a double filter.

                      Jerry

                      Comment


                      • #12
                        If you're talking disposalable freon tanks consider this............they have a one way check valve to stop anything from entering the tank. Plus the valve orifice size may be too small for good air flow. You might have to remove the valves and use another fitting. How will you drain the tanks of moisture? I have heard of people using water heater tanks for air but I would think by the time they get them they would be crap. I personally think you may be wasteing your time to use freon tanks and try to coat the inside. The reason
                        for the one way valves was to stop people from doing this. Now if you can find some old aluminum freon tanks, that would be great. I doubt you will. They probably have all be taken to the recycle spots already.

                        Comment


                        • #13
                          Originally posted by jfsmith View Post
                          If you go with painting, rubberizinf or what ever to preserve these tanks, have a really good output filter on this arrangement, maybe even a double filter.

                          Jerry
                          Hi ... thanks for the input ... why would a coating on the inside require more filtering? You'd think it would, if anything, keep the inside cleaner (less rust).

                          Comment


                          • #14
                            Robert,

                            When you have a air flow thru a void, its bound to pick up some material, not sure of how much, but some. Plus I have to drain my tanks every so often for moisture, that may be a concern for you using these freon tanks.

                            My plasma cutter require two air filters on the input of the cut, while I keep those on the cutter. The air line to the plasma cutter also has filters. It keeps the moisture down and the cutter doesn't complain about foreign matter.

                            Jerry

                            Comment


                            • #15
                              Air Tank

                              Their are codes to go by when designing and building pressure vessels, even small ones for air. You can buy some Sch. 10 Pipe and some caps. Then you have the cylinder shape. Boxed , (Square) is a very bad Idea . Having the metal rolled somewhere might be an option also, and buying some dished heads for the ends. Keep it safe with a relief device.

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