Welding a petrol tank

[XRVrider]

Have this old bike that has a petrol tank, and a spare, that have a stud broken off each. I cannot replace it as its really old and will be expensive/hard to find. Cant fit them to the bike without the studs. Really no way round this but to repair them.

I can weld and have all the equipment, but am dubious about welding them up, due to possibility blowing my hands (or more) off. One has had petrol in recently and the other hasnt for years.

Anyone filled a tank with water and welded... any other tricks that will be make this safe? Ta all.

[CookMySock]

Anyone filled a tank with water and welded... any other tricks that will be make this safe? Ta all.

I haven't, but the water-filled method was described to me in great detail.

From what I remember, the tank should be full of water except for the area to be welded, and that area should be kept as small as possible.

Once you start welding you should flash off any escaping gas every few seconds to make sure it does not accumulate and explode.

I have spoken to welders who have welded boat fuel tanks while they are full of fuel - apparently safer than empty - with diesel running down the job as they proceed.

I suspect the water-filled method is superceded by them purge-gas method.

I would consider armoring myself in some manner in case the thing went boom.

Good luck, and be careful, and ignore any advice from someone who hasn't done it.

Steve

[jellywrestler]

running water through for a period of time and then i've put the vacuum cleaner on blow or compressor through for a while while welding this will sort it.
meths in afterwards wilol disple any water

[sparkles]

put it on the end of a car exhaust and let it dry out some hours ,o but then u will get water in ya tank by condensation ummmm or pipe a hair dryer to it

[kevfromcoro]

its the fumes that make the bang.. think they are safer to weld full of gas.
personally i would fill it with water. the advice in this thread is pretty much on the button

[Ixion]

I've welded and brazed (brazing is better on old tanks) many bike tanks. I've not blown myself up yet.

Forget water. Gas purging is the only safe way.

[YellowDog]

its the fumes that make the bang.. think they are safer to weld full of gas.

Sounds interesting.

Look forward to the Youtube clip.

[CookMySock]

i've put the vacuum cleaner on blow or compressor through for a while while welding this will sort it.

I think that is very dangerous.

What if I get a bottle of oxy and bottle of nitrogen and blow it through a chamber at high pressure, and mix visible fuel vapour with it and ignite it? No? Well, thats what you are doing.

CO2, Nitrogen, or Argon purge.

Steve

[p.dath]

So you wouldn't recommend dropping a match in first to make sure the fumes are gone?

[LBD]

So you wouldn't recommend dropping a match in first to make sure the fumes are gone?

Darwin award coming up...

Water flush for a while then remove all fittings where fuel may be lurking ie valves or internal fuel pumps. When dry tape over openings and purge with an inert gas such as argon. Leave the inert gas flowing, at a low flow into the tank while welding.

Tig welding is then a good option as the absence of oxygen in tank will leave a clean tidy weld on the inside.

Avoid brazing...bronze welding if possible.

Dry out tank and refit fittings with new gaskets and seals.

Done it many times....

[Skunk]

Water flush for a while then remove all fittings where fuel may be lurking ie valves or internal fuel pumps. When dry tape over openings and purge with an inert gas such as argon. Leave the inert gas flowing, at a low flow into the tank while welding.

Avoid brazing...bronze welding if possible.

Best advise yet. I've welded many tanks and usually fill them with water. Purging with argon is the best (dry and inert).

[XRVrider]

Its gonna be easy to remove all fittings, and will give this a go tomorrow. Will try the water filled angle and am gas welding. The water will be filled right up to a very small area where I need to weld. There's no chambers in these tanks so no area for fumes to be caught apart from the small area I m welding. If I dont post here tomorrow, Im in hospital. Will keep an eye on here for any more advice tonite though. Cheers guys.

[jellywrestler]

DO NOT LISTEN TO ANYONE WHO SAYS WELD IT FULL ESPECIALLY THE ONE WHO MENTIONED DEISEL RUNNING DOWN THE WELD. deisle is far less volatile than petrol and you might get away with deisel running out but not petrol.

[XRVrider]

Right on, definitley not welding with anything but water in the tank. Ta Jelly, hey did you get my pm to you regarding the Nzeta's? Its those tanks Im welding.

[LBD]

Right on, definitley not welding with anything but water in the tank. Ta Jelly, hey did you get my pm to you regarding the Nzeta's? Its those tanks Im welding.

Plroblem with water can be the cooling effect and if it gets a little warm you get steam expanting coming out of the weld buggering up the integrity of the weld. The strength of the weld can also be affected with rapid cooling.

Wash with water then purge with inert gas is the only serious and reliable option.