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Welding a fuel tank

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  • #61
    Originally posted by Don Young View Post
    In the 40's and 50's, Harley and Indian tanks were small and strong enough to contain any fire/explosion. It was common practice to empty the tank, blow it out a bit with air, and stick a lit torch in the filler opening. The result was a pretty good boom but I never saw any evidence of tank deformation. When the torch was applied a second time there was often a second smaller reaction. I have no idea how close the tanks were to rupturing and certainly do not claim this procedure to be safe.
    .
    That was "paintless dent removal" before there was paintless dent removal.
    Andy

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    • #62
      I enjoyed reading this thread and as it happens I had to weld one of my motorcycle tanks. Having soldered a few way back and not really pleased with how they came out I opted for using the mig. The tank in question had a crack in an area midway up the tunnel next to a strengthening rib. A rust free, near perfect tank that would cost way too much to replace. Pulled all the fittings and washed it out with a degreaser. Then a bit of the sunshine treatment for a couple of days. Being able to get the faintest of gas odors I ran some compressed air thru a couple of different times. Then to the store to get some dry ice which I found is sold in handy pellets about 2 inches long and about an inch in diameter. I bought five lbs for just over six dollars. So my five gallon tank is suppose to need about a pound of dry ice to displace the air. I throw in a couple of pounds and get the welder ready. The dry ice goes from solid to gas and will build pressure while settling at the bottom. A shop towel in the filler hole oriented up to vent air first and then keep out regular air, all other openings plugged. After awhile the tank is getting cold. I try to position it for welding and move the dry ice away from the weld area. I use a heat gun to dry the condensation that is formed near the area I want to weld. With a steady amount of CO2 exiting the tank I fire up the welder. The CO2 is building a little too much pressure so I adjust the shop towel to let more gas out. First weld ground down and redone. Realizing that installing the gas cap will pressurize the tank I pop off a cap on one of the fittings and just hold finger over it and get out the bubble solution. Find a second crack and install the shop towel again. Weld crack number two. Decide to strengthen the area a bit and retest. All good and the tank is perfectly clean inside after the the CO2 is gone. Leftover dry ice for drinks, break into smallish bits to get that Halloween mist. Two weeks and a few heat and cool cycles and the tank weld is holding great. Mike

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      • #63
        A pound of dry ice will produce 62 gallons of CO2 and is 1 2/3 denser than atmospheric air. I've use dry ice and let it sublimate with the exit of the tank at the highest point.
        Last edited by 914Wilhelm; 11-03-2016, 06:12 PM.

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        • #64
          Originally posted by Magicniner View Post
          The tank should either be steamed clean or have an inert gas piped in whilst working to maintain a non flammable mixture, a very easy way to achieve the second is to pipe the exhaust from an internal combustion engine into the tank, clean breathing air for the welder should be a consideration ;-)
          Filling with water and just leaving the area to be welded unfilled doesn't make a tank safe, it confines the potential explosion with an incompressible liquid - very un-smart and well documented bad practice for tank welding!

          - Nick
          This is how I've seen done & done some myself & it works fine, not a lot of extra work or cost.

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          • #65
            There are some excellent methods mentioned above but even though I'm a pretty fair welder, I'm going to let others do all the welding on fuel tanks. Whatever method you use, I'm of the opinion that you never really know what's going to happen when you weld a fuel tank.

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            • #66
              I welded my Motorcycle tank in July and have ridden it thru the Summer. I have been looking at the weld to see if there is any issues and so far everything is good. I found out the area I welded was prone to failure from another forum. The replacement cost of my tank would have been close to 1000 dollars and used tanks were not looking as good as what I have. Welding with the Dry Ice in the tank was very easy and I would say very safe. Dry ice was cheaper than trying to use inert welding gases and easily bought. Ventilation was as easy as an open door. I consider it a very good option for a hard to replace tank. Mike

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              • #67
                The water system works well in sits where it seems applicable. Object being to reduce the available volume of any flammable mixture to a point where it's not damaging. I have used the exhaust from a shop vac blasting in a tank prior to and during welding/brazing and that has been ok also ..prevents any buildup of fumes. All methods should include a thorough clean out first. When u heat the tank surface to repair, the heat will drive additional flammable vapors out of the pores in the metal and rust? and must be taken into consideration. Also when using oxy/acet torch it's possible to unintentionally introduce oxy thru the flaw you're repairing which ain't good!!

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