Welding gas tank

[zedhead]

That's a very good point Pliers - thanks - but I find that the welding forums tend to have too much info! I was just looking for some direct hints and tips from someone who had actually worked on a motorcycle fuel tank, and who knows what works and what doesn't. And, more importantly, what works with cheap (unadjustable) TIG and MIG. The forums seem to focus on professional quality welding machines, not the el cheapo stuff that us shed-dwellers use :-)

[alanbcs]

Just a helpful hint...Fill the tank with crushed dry ice... this will displace the oxygen and keep any fumes from igniting to a flash of fire...
also too...tig welding is far better in welding up a gas tank...more control of your welding...

[shovel625]

An entertaining thread, for sure, but those of us who have yet to attempt modifying a tank would like some more direction please!
MIG or TIG or gas?
I have two tanks to modify, and I have a cheap MIG and a cheap TIG - which would be better? And any secrets with either method? Short runs? Thick / thin rod / wire? etc

I dont have enough skill with gas to do a tank, High Frequency TIG using pulse is the way i would go. im not a professional level yet, so i prefer to go with a bit of a cooler setting, just takes longer but penetrates fine.

[shovel625]

That's a very good point Pliers - thanks - but I find that the welding forums tend to have too much info! I was just looking for some direct hints and tips from someone who had actually worked on a motorcycle fuel tank, and who knows what works and what doesn't. And, more importantly, what works with cheap (unadjustable) TIG and MIG. The forums seem to focus on professional quality welding machines, not the el cheapo stuff that us shed-dwellers use :-)

cheap TIG, is it lift start or scratch start? Advice, dont draw too much heat into the metal or you will be working it with a planishing hammer to even it out all day, which you will be doing anyways to hammer form your weld beads. If you narrowing a set of stock tanks id bet the metal will be about .065 thickness. 60-65 amps as a baseline starting point

[Luky]

I dont have enough skill with gas to do a tank, High Frequency TIG using pulse is the way i would go. im not a professional level yet, so i prefer to go with a bit of a cooler setting, just takes longer but penetrates fine.

Before you decide to weld on those tanks do this. At night go outside in the dark and shine a bright LED flash light
from the outside of the tank while looking inside the tank. If you see many holes of light it would not be worth welding. Also if you see a tank lining material it is not weldable.
When you put extreme heat by welding to the tank any petroleum residue inside can make a explosion possible.
Even if you wash out the tank several times it can still have residue in the fabric of the steel tank.
It can still produce an explosion.

Now all these people will come on line and tell you they have welded on tanks or their friends do it all the time.
That does not mean it is safe.
Go to www.welding web.com and read about all of the injuries and deaths caused by welding on tanks.
It just is not worth it. Examples below.

https://www.youtube.com/watch?v=9DP5l9yYt-g

[grampastentis]

Before I retired I was a union pipefitter and I worked in refineries and power plants. You need three things to cause a fire or explosion, oxygen, fuel and a source of ignition.
Take away any one of these and you are safe. When welding on tanks that have residual fuel vapors the only thing you can control is the oxygen.

I weld on gas tanks every now and then and here is the secret. Insert a hose into your gas tank connected to a nitrogen tank. Nitrogen is an inert gas.

Duct tape all but two of the openings and then duct tape the hose to an opening of your choice.

Purge the tank with nitrogen then turn the regulator down to keep a slow and steady flow going through the tank and weld to your hearts content.

You eliminated one of three things needed for combustion, the oxygen is gone. On the last opening leave a space for the nitrogen to bleed out while you are welding.

Of course if you are welding a fitting you just leave the tape off and let the nitrogen continue to purge.

[metalheart28]

I've been doing it for years. Famous last words!

[farmall]

You can eliminate any internal residue by various methods including having a radiator shop dip it in their tank which also strips paint.

If you are careful, lye/caustic soda mixed with water has been used to remove carbon and grease since the steam locomotive days but it's caustic (which is why it works so well) and WILL hurt you if you fuck up. Wear rubber gloves and eye protection. Have a bucket of clean water and a garden hose handy for emergency washdown if ya get any on you.

No half measures! Remove all the petroleum leftovers or get another tank. They're cheaper than a fuckup.

Purging the tank with shielding gas works nicely AFTER thorough degreasing. While I have nitrogen, CO2 is cheap, the cylinders hold much more volume since CO2 stores as a liquid under pressure, and is worth having even if you MIG with MIG mix (better for sheet metal). I use my CO2 cylinders for tire inflation and to drive pneumatic tools in the field as well as welding.

And any secrets with either method?

Practice on similar scrap until you can do it in your sleep, same as any process.

[confab]

I've never done this, but I took an ICAR certified structural sectioning and welding course in my youth, and painted cars and did chassis work for a time subsequent to that.

Our instructions were: If you must repair a fuel tank, remember that the fluid is flammable but the fumes are explosive.

We were told to fill it with water, place a torch in the neck and drain the water from the tank slowly.. And that the end result was safe to work from that point.

Again, I never did this but it was a pretty good course otherwise.

Free advice is worth what it cost..

[confab]

PS: On the subject.. I also once saw a Harley Fat Bob style tank that had to be replaced because a bodyman stuck a stud gun to the side of it, attempting to remove a dent.

It didn't break the tank (although I guess it easily could have?) but it never fit the bike again after that..

lol..

Be careful out there.

[farmall]

He should have cleaned out the tank then heated the area with a torch before pulling the stud. Pulling the outside of a rather strong curved shape was bound to fuck with the stock tabs.

[confab]

Probably..

I know the guy who did it. He's a local.

Nice enough guy, not super bright. He's probably lucky just to be alive.

lol.

[shovel625]

Before you decide to weld on those tanks do this. At night go outside in the dark and shine a bright LED flash light
from the outside of the tank while looking inside the tank. If you see many holes of light it would not be worth welding. Also if you see a tank lining material it is not weldable.
When you put extreme heat by welding to the tank any petroleum residue inside can make a explosion possible.
Even if you wash out the tank several times it can still have residue in the fabric of the steel tank.
It can still produce an explosion.

Now all these people will come on line and tell you they have welded on tanks or their friends do it all the time.
That does not mean it is safe.
Go to www.welding web.com and read about all of the injuries and deaths caused by welding on tanks.
It just is not worth it. Examples below.
https://www.youtube.com/watch?v=9DP5l9yYt-g

thanks, i take all pre caution. im a good welder i just dont (gas) oxy actelyne weld.

[Scrapenstein]

Last weekend I filled up a tank with hot water and liberal amount of dawn dish soap then let soak for 24 hours, repeated this a second time. This left it with zero gas smell. I then sand blasted the entire tank with no problems and saw plenty of sparks from the built up static electricity. I'll have no qualms about welding on this tank but may stick the oxy torch in the fill hole before hand just to be safeish.

[KrisCarr]

As an autobody tech for the past 16 years and a C ticketed welder, I have welded my share of fuel tanks. I drain the tanks, blows them out with compressed air for about 15 minutes and then flush with argon. I always leave caps off and any opens clear. Fuel ignites, it doesnt explode unless confined. I use a mig welder. I have cut tanks in half and welded them back together, replaced bungs, moved filler necks and even made a couple from scratch. Ive never had so much as a flare up.
My business partner is of a different school of thought. He always fills tanks for of water. This works for him but it does present its own issues which is why I don't do it. One problem is that it makes welding more difficult as pressurised steam from rapidly boiling water pushes agaisnt your welds causing pinhole blowouts. Another problem is getting all that water back out so it doesn't get into your fuel system. The one potential problem people overlook is that if using a welder such as a mig or tig you are running high electrical current through the metal to create the arc to weld. What happens when you run high electrical current through water? It can create hydrogen gas, which is more volatile than gasoline. While I have never seen him blow himself up in this manner I know that there is potential. Realistically though there is always a potential for danger when welding something that once contained flammable products so extreme caution should be used. Also proper PPE (personal protective equipment) should be used at all times.