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Safest way to weld inside a gas tank??????

Discussion in 'The Hokey Ass Message Board' started by 1950ChevySuburban, Mar 1, 2010.

  1. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,512


    Never heard of the dry ice method before! I do learn something every day!
  2. chaos10meter
    Joined: Feb 21, 2007
    Posts: 2,191

    from PA.

    Safest way ?

    Let someone else do it.
    49ratfink likes this.
  3. Sphynx
    Joined: Jan 31, 2009
    Posts: 1,142

    from Central Fl

    I ve heard of people running a hose from the exhaust pipe of there car to the tank , But that would only work if you cars emissions were good if not BOOM grenade inspected !!!!!!!!!!!:D
  4. dmw56
    Joined: Jan 1, 2008
    Posts: 709


    I too worked removing under ground storage tanks and we always used dry ice. Plus we used lots of monitoring equipment to check for oxygen concentrations and lower explosive limit levels before any cutting or removing of the tank. Any inert gas like CO2 or Nitrogen will make it safe to cut or weld.
  5. 1930roadster
    Joined: Nov 9, 2009
    Posts: 323


    i welded plenty of Motorcycle gas tanks, a few cars too. I just let them completely air out, about a week,2 is better. DO NOT FILL IT WITH WATER it WILL go boom!...
  6. hoof22
    Joined: Jan 15, 2008
    Posts: 530


    Had a friend that needed to "braze up" a small hole in his gas tank at my shop...he did the rinse it out 10 times, then fill it with water bit to push out the explosive fumes deal, left the water in while he brazed up the pinhole, just moved the tank around 'til the hole was on top. It worked fine, until he got impatient and decided to dry out the leftover water with the torch...he was heating the outside of the tank, and looking in at where the last little bit of water was boiling off when she blew-KABOOOMO! Scared the crap outa me! Took off his eyelashes, eyebrows, and about the first 4 inches of his hair...people look really stupid without eyebrows for some reason...he looked like he had bad haircut and a sunburn for a week or so...He was lucky, that time...apparently he closed his eyes just in time...good luck with your project!

  7. Roupe
    Joined: Feb 11, 2006
    Posts: 721


    Cosmo got it right! Back in the 60's my dad showed me how to solder a gas tank the old school way after a profesional welding shop blew up my buddies dirt bike tank. Here are some pics of the old school tools needed, a big copper tipped soldering iron and a torch. The torch is only used to heat the soldering iron. Just remember to keep the torch away from the tank.


    Attached Files:

    Fitty Toomuch and Hnstray like this.
  8. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 3,034

    from Dublin, OH

    I'm For the let a shop that does gas tank repairs do it, and at least 4 blocks from where you live!
    49ratfink likes this.
  9. Bloodandmotoroil
    Joined: Feb 22, 2010
    Posts: 154


    i've got one with with a 3in wide tip, the irion weighs about 15lbs
  10. chubbie
    Joined: Jan 14, 2009
    Posts: 2,316


    One should wear ear plugs
    49ratfink likes this.
  11. 1950ChevySuburban
    Joined: Dec 20, 2006
    Posts: 6,188

    Member Emeritus
    from Tucson AZ

    Drained it, flushed it with water, filled it with soapy water and let sit 2 days.
    Positioned the tank so I could weld with the most water in the rest of the tank.
    Hooked a dryer vent hose to my diesel truck exhaust, ran the truck for a while.
    Tested inside the tank with a burning very long stick. Mig welded 3 small tacks. Done!

    Cost of fabbing a swing baffle: $5 bucks
    Time spent doing this: 3 hours
    Scared? Shitless
    Maybe for some things there is Mastercard! haha

    Gas tank welding: One more service NOT offered at Kennedy Automotive!
  12. gearjam1
    Joined: Sep 6, 2006
    Posts: 248


    -Glad I found this discussion... I used the search feature in order to figure out how to modify my motorcycle tank, and then weld it as safely as possible. I've read lots of welding manuals from the 1930's that emphasize the dangers of welding fuel tanks, and want to tip the scales in my favor.
    I am going to use the combination of flushing with water and TSP, dry ice, and the exhaust method. One of the old methods I've read about involved filling the fuel tank with sand...but, I think that is more for something that is being permanently scrapped...not being used again. If I post a follow-up on how mine went, you'll know it went well. If I don't, then... :eek: -Tony B
  13. billfunk29
    Joined: Jun 28, 2005
    Posts: 42

    from Minnesota

    It is my experience that gas tanks are hard to blow up. I had an old tank with about 2 gallons of gas in it. Poured a trail of gas to the spout and lit it. When the flame got to the tank it just went woof!. Not to be deterred. Put the tank in the hot sun and sloshed the gas in the tank around. Woof again. Now I am getting frustrated. Get out the welder and put oxygen in the tank. Louder woof. I was a foolish child when I did this and don't recommend it.
    warbird1 likes this.
  14. Let my worthless brother-in-law do it...……… his garage!!
    61Cruiser, 49ratfink and alanp561 like this.
  15. Hmmm, 10 year old thread, op not seen in 8 years...maybe it didn't go well.
    49ratfink likes this.
  16. Fortunateson
    Joined: Apr 30, 2012
    Posts: 4,180


    So you are saying the CO2 will purge the tank of fumes? What happens when you heat the tank up and the pores open up emitting more vapour? Or will the dry ice last long enough to rid the vapour after the tank is heated up?
  17. I have patched gas tanks using a soldering iron and silver solder. The Copper soldering iron has no sparks to set off explosion .
  18. not sure what you are implying but the gentleman in question died from a serious medical condition unrelated to welding a tank. he fought the fight bravely.
    chubbie, Tman, pitman and 1 other person like this.
  19. Gearhead Graphics
    Joined: Oct 4, 2008
    Posts: 3,851

    Gearhead Graphics
    from Denver Co

    Ha, gotta love a good 10 year old explosion thread coming back from the depths.

    I hope the guys still in one piece!
  20. Sorry to hear the op passed on...too much of that going on amongst us fellow enthusiasts.

    It was simply meant as a tongue in cheek comment about another resurection offering advice to a long past thread. No harm meant. I'll head back to my corner.
    Last edited: Aug 17, 2020
  21. birdman1
    Joined: Dec 6, 2012
    Posts: 1,250


    Just a side note. The guys that welding gas tanks that didn't work, are not telling their story
    49ratfink likes this.
  22. Smaller holes are easier to patch with a suitable band-aid metal patch simply soldered over the offending spot. (like the hole worn in my Dodge Dart tank from the pick-up screen rubbing on the tank). I just used a large, electric Vulcan soldering iron and tinned the area around the hole and the mating surface of the patch then pressed real hard whilst heating the whole thing again until the excess solder oozed out.

    Every tank I've ever WELDED has been done with oxy/acetylene. I fill the tank with soapy water and tilt it to leave the area to be patched sitting in an air bubble. Any volatile fumes that could burn are contained in such a small pocket that combustion is barely enough to disrupt the flame of the torch.

    I've lost track of the tanks I've fixed this way and have never had more than a slight "poof" when I waved the flame over the hole for the first time. The key is to make the air pocket under the area to be welded as small as possible and not have water contacting the back side of where you need to solder..

    The larger the air pocket, the larger the explosion. Empty tanks are highly explosive. Full tanks won't explode at all, they'll just burn at the filler neck if it's open.

    When I hung out at a salvage yard back in the sixties we used to pull out all the gas tanks and pile all the stripped bodies on top of one car that had the tank still in it (usually a car with a small tank) and fill the tank to the brim and light the filler tube.
    If we didn't have any small-tanked vehicles, we'd partially crush a larger tank to reduce the volume, fill it with gas and put it under the bottom vehicle. Once lit, the tank would burn for hours and keep the hulks burning until all the upholstery, wires, hoses and anything else that was flammable was gone then we'd crush them with the iron weight on the crane and load them onto the flatbed to be sold as clean scrap iron.
    We got a lot more money for clean scrap than for cars that were simply crushed.
    The greenies would have a fit with that today.
    Beanscoot likes this.
  23. pitman
    Joined: May 14, 2006
    Posts: 5,095


    Drain, air dry, soapy water, slosh around good, drain, then exhaust piped in. Final rinse. Dry. Don't get caught by leaving fuel puddles.
    Works fine.
  24. Fitty Toomuch
    Joined: Jun 29, 2010
    Posts: 251

    Fitty Toomuch
    from WVa

    Fill with water, dump, Slosh around some ammonia, dump, damn , it actually works:eek:
  25. junkman8888
    Joined: Jan 28, 2009
    Posts: 622


    If you need to clean out a fuel tank for repair or modification and you can't find a radiator repair shop to "boil it out", do this: If it's got sludge in the bottom, dump in a quart or so of lacquer thinner, then mop up the goo with a rag wired to a stick or a strip of metal. Keep mopping until the goo is gone, then take the tank to a car wash and blast it out with lots of hot soapy water. When you get it home, lay the tank out in the hot sun, the heat will help pull any solvents out of the pores of the metal, to help the process along I hook the vacuum hose to the exhaust side of my shop vac and blow air into the tank until what comes out doesn't smell of gas or oil.
    It's pet peeve time: You didn't mention what vehicle the fuel tank fits, and you didn't provide any pictures so we would know what you're dealing with. You did mention it was a "relatively new custom-built" gas tank, but you didn't mention what material the tank is made from. You talk about "epoxy", and "one or two quick spot welds", but the truth is, if you have to ask us how to do it, you can't do it. What you need to do is send the gas tank back to whoever built it, they should have put baffles in the tank to begin with. Best of luck with your project.
  26. Beanscoot
    Joined: May 14, 2008
    Posts: 2,077


    Not sure why people are wondering how the job went, when the original poster explained his success back in post #41.

    I would recommend against cleaning the tank with strong alkali such as caustic soda or TSP as they will remove the terne coating, which protects the steel of the tank from rusting.
    pitman likes this.

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