Can I safely weld a steel gas tank?

[TX Mudder]

This is actually a steel motorcycle tank, but the question is the same regardless of if it's a motorcycle or a truck tank.

I want to grind off the stock tank bung (where the fuel petcock screws on) and weld on a new tank bung.

I have a MIG welder so I know I can weld it, but would it be safe? Obviously one would drain all the gas. Would I fill it with water? Or something else? I am of course concerned about gas vapors going boom.

What do you guys think? I think the local radiator shop fixes gas tanks, so they might be able to do it for me if it is a bad idea for me to do it.

The other option:
I could cut some of the length off my stock tank bung and use a die to thread it to stock Harley-Davidson, which is 22mm. I have not been able to locate a 22mm die. Anyone know where I can locate one? Obviously they exist, but I have not been able to find one.



http://www.pingelonline.com/adaptor_plates.htm
Scroll down to tank bungs and these are the ones I am looking at.

 

[big jimmy 91]

Take away the oxygen and you are good to go , no boom
Use an inert gas , pressurize the tank with it and weld away (keep it running in the tank at all times when welding)
You could also run an exhaust in it while welding to keep it from doing the big bang
Just be carefull , no need to get hurt or killed for a few dollars

 

[k20]

22mm die

 

[SkulzNBonz]

If you were to powerwash it internally, and use a good de-greaser on the internals, and then let it completey dry, I wouldn't see why not. I think there is even some kind of cleaner made to clean out gas tanks so they can be welded, but I'm not sure.

John

 

[diesel4me]

A body shop fixed a tank for me once by sqirting his CO2 fire extingusher into the filler neck after flushing it out with water,he sealed the filler neck and soldered it with a torch with no trouble--while I hid in the far corner of his shop,ready to dial 911! /forums/images/graemlins/yikes.gif.He said he has done hundreds of tanks this way with no problem--my dad used to work for the gas company,they used to put a flexible hose like the ones they use in garages to route the exhaust outside in the winter down into a broken gas main,and use the exhaust to purge the gas fumes out and make it non-combustible so they could weld it--they did have one minor explosion when the truck they used was running very rich because the driver had forgotten to push the hand choke in all the way,and it went poof!and scorched the welder pretty good.I hate to fix gas tanks,I have brazed them after filling them with water,but have never gotten any satisfaction,they always seem to have a few pinholes you cant seal up--or they leak again in short order,so I usually replace them.I had limited sucess with fiberglass mat or cloth on tanks too--about 6 months and it peels off and leaks again--J-B Weld works great though!. /forums/images/graemlins/crazy.gif

 

[TX Mudder]

Thanks all for both the info and the link for the 22mm die - it was just what I needed. I should be able to complete my project! /forums/images/graemlins/peace.gif

 

[CyberSniper]

I've washed the gas out with mild soap (like laundry detergent) and brazed them before.

 

[clarkjw24]

My father-inlaw is a pipeline welder. He always says just throw a match to it first. /forums/images/graemlins/dunno.gif It will only go boom once.

 

[surpip]

not to shure about the only go boom once thing, i have a potato gun and after i shoot the last potato i click the ignighter a cupple of time's to make shure its all out, but i can still go back to it in a week and make it lght off again, /forums/images/graemlins/dunno.gif

 

[spoolnaround]

When I worked in the oil fields we used to cut the tops of 55 gallon drums off that had once held flamable liquids. If you pressure wash a 55 gallon drum with 200* water you were good to go as long as it was full of steam. if your drum cooled on ya you would get a good flash out of the bung. I have seen people burned pretty good doing this. I would say fill it up to the point you are working on with water then go to town, thats assuming its most of the way.

 

[hi pinion]

Be careful with that please. I had a freind of a freind die that way in the junkyard.He was fooling with a gas tank and a tourche and it exploded and killed him. /forums/images/graemlins/frown.gif

 

[77ChevyK10]

fill it whit water

 

[mountainexplorer]

We flush out, repair and line fuel tanks at the radiator shop I work at.

We make for sure there are no fumes left. I've been the one who gets to clean the tanks before they are worked on. First, we use the pressure washer/steamer to flush them out. We use an industrial type of cleaner, and I repeat this process 1-4 times depending on how bad the tank is. The water is nearly boiling hot.

Then, we use Muriatic acid, which gets put in the tank, closed up, and turned so that the acid eats up all the gas fumes imbedded in the pores of the metal. It also dissolves old tank liner and rust. Sometimes, the acid process has to be done several times as well.

The acid gets drained, the tank gets thoroughly washed out with steaming hot water again, until no acid and no fumes remain. Then it gets dried with a torch. Air gets shot in through one (of usually two) openings, so that if any fumes do remain and ignite, the tank wont explode, but the flame will shoot out the 2nd opening. Then, once it's dried completely and no moisture is left, it gets patched. Patch jobs or plugs put into tanks are soldered in, rather than welded at our shop.

Then, comes the lining stage.

Thats the process as much as I know it to be. At least how our shop does it. The acid and liner isn't exactly something anyone can go out and buy though.

 

[spoolnaround]

I dont know about the lining but Muriatic acid can be found anywhere, thats the acid I put in my pool.