Welding on a gas tank.

PAPSTISY

PAPSTISY

Member
#1
#1
Ok, I'm not a welder so this might be a easy answer that I'm not understanding.
I have a tank. It leaks in one spot where someone already tried fixing. So I cleaned area and tried JB weld and it still has a soak type leak.

Now the tank has been dried out and no gas. So I take it to my local welder and he said know way would he weld on a tank that had gas.

It's clean so wouldn't a welder just burn off gas when being worked on? What is the big deal to drop a small bead around tiny hole? If done from the outside and cosmetic is not an issue I don't see the concern. Do you guys?
 
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125ccCrazy

125ccCrazy

Well-Known Member
#2
#2
if there are any fumes you will only try welding it once...

if it's a tiny hole I would solder it so you don't take a chance of burning a hole in it... wash it out over and over with soap warm water and then leave an air hose off the compressor bleed through it for a while.... hold it in the sun and see if you can see any vapors coming out the neck and if you can smell ANY gas... It's not an impossible job but you do need to be extremely careful. my oldest brother can vouch for that after my Dad tried to braze the tank for his 55 chevy about 40 years ago... Thank God no one was killed or hurt... it sounded like a bomb went off in the garage... the tank split open so you could see the inside of the top and bottom at the same time..
 
bigrob

bigrob

#3
#3
I have brazed up quite a few bike tanks , some even with thumb sized holes rusted in them and have made a few custom round tanks from empty propane cyl
As mentiioned above I repeatedly wash them out with lots of hot soapy water then I place in front of my electric heater to heat and dry and evaporate any gas residue
Some times it takes several days and a second washing until I feel comfortable putting a flame to it

Yes there is a danger of iexplosive vapors , but we are talking about much smaller tanks than automotive and there are usualy no baffles inside to trap pockets of gas

I guess I would be aprehebsive about welding someone elses tank unless I had done the prep work and cleaning myself :shrug:
 
KustomKartKid

KustomKartKid

Administrator
#4
#4
I was hanging out in my buddys station and he pulled a leaking oil reservoir tank out of the inner fender of this Mercedes (dry sump car). He washed it out with gasoline...then washed it out with hot soapy water for about 10 minutes. Could not smell gas at all.
He's gonna braze it....he lit the torch and put it by that thing...we were both leaning over it...and BOOOM!!! :scared: :scared: That thing went off like a bomb...big flame shot out of the filler neck. We were both like "holy crap that scared the hell of me!!" :eek:hmy:

He says "oh well, the good thing is that can only happen once, the gas is burned out of it now". He lights the torch and puts it up to it again ...BOOOOOM!!! :scared: :scared: Almost knocked us down the second time....just as loud if not louder!

I said "that's enough...I'll see ya later." :no:
.
That was 30 years ago I rememeber it like it was yesterday.



.
 
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KustomKartKid

KustomKartKid

Administrator
#7
#7
I believe the correct way is to place a purge line of inert gas (like Argon) inside the tank while you're welding. No oxygen...no BOOOM!

The old timers used to run a hose off a tailpipe and pump exhaust gas into it while they were welding....:shrug:
 
Stangrcr1

Stangrcr1

New Member
#8
#8
KustomKartKid said:
I believe the correct way is to place a purge line of inert gas (like Argon) inside the tank while you're welding. No oxygen...no BOOOM!

The old timers used to run a hose off a tailpipe and pump exhaust gas into it while they were welding....:shrug:
Click to expand...
This ^^^^^


I did it once and used the gas line from my welder, Mig mix (Argon/CO2). Turned down the regulator to where it was just barely hissing out, stuck it in the tank, and started brazing. Tank had been washed also.
 
Txpowdercoater

Txpowdercoater

New Member
#10
#10
gumpit said:
Can you weld a tank when it is full of water? Just curious. No fumes that way.:shrug:
Click to expand...
The reason tanks go boom after copius rinsing and soap is that the steel gets the hydrocarbons in the pores of the steel and then when heated , the vapors come and go boom.

to answer the water weld question.
I watched my father do this when I was 14 or so, he filled a gas tank with water and proceeded to weld it and it blew up like a fat grape, pushed hell out of the tank seams but didnt tear them. The vapors are what gets you, I'm guessing he created a small pocket of air and vapor and then provided an ignition source.

You can also degas tanks using crushed dry ice, it will evaporate, the vapors being heavier than fuel vapors, so it fills the tank and pushes out the bad and leaves the tank with an inert atmosphere.
 
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