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I suspect the water-filled method is superceded by them purge-gas method.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

[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.

[jellywrestler]

Ta Jelly, hey did you get my pm to you regarding the Nzeta's? .
Hey; are we on first name basis now? i'll take them into a copy shop and get them done, as they're foolscap pages and my scanner thingy is only A4

[XRVrider]

Sorry Mr Wrestler

Thats great, ta for copying, like I said before just name your price, will send you a cheque, not a rubbery one. I got a couple of questions for you, just in regards to your bikes and what you did to em... and what one is worth when done up... I've no idea. Also I'm a grovelling bee-arch but got any interesting/hard to find spares?

[XRVrider]

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.

Ta LBD

I just gotta whip around one stud on each, should be quick so hopefully not too much steam. If so I try the inert gas way. Didnt think of that though, ta for the info.

[LBD]

Ta LBD

I just gotta whip around one stud on each, should be quick so hopefully not too much steam. If so I try the inert gas way. Didnt think of that though, ta for the info.

Studs For?

Sealed with a Gasket?

Do you need to weld them?

[XRVrider]

Yep there's no way around it. They are Nzeta tanks that have 4 studs that bolt the tanks down onto the body.

The studs are stupid as they actually go up inside the fuel tank a wee bit, so when these have broken out/pulled out they leave an 8mm hole. They are welded onto thicker metal patches that are welded onto the tank from new, so they pull out of the patch. Spose they were thought up 50 odd years ago, so go figure.

[LBD]

You have thought it out obviously...You restoring an old bike?

Out of interest, what is it?

[XRVrider]

They (2 of) are Nzeta's. You might know them, but google search Nzeta in images for how they are supposed to look.

[Firefight]

have been to a few of these that gone wrong over the last 20+ years in my the job, but would imagine they are the extreme events, I know that work shops do this all the time, with no problems. some good info posted so far.

have a look at these links

http://www.mig-welding.co.uk/forum/showthread.php?t=3818

http://www.mig-welding.co.uk/forum/showthread.php?t=6056

there poms, but it still of interst.

I did it myself a few years ago, just filled the tank with water as close to the top , put on the cap inverted the tank(tipped it upside down) and then braized (sp?) the hole, when done hooked a hose line to a warm air fan dried tank out ..

had a fire esxtingusher handi


Firefight

[imdying]

put it on the end of a car exhaust and let it dry out some hours


Forget water. Gas purging is the only safe way.


Carbon monoxide FTW!

[LBD]

They (2 of) are Nzeta's. You might know them, but google search Nzeta in images for how they are supposed to look.

Of course...I did not recognise the name but put the CZ in front...

Did the NSU look similar?

Good luck with the project.

[XRVrider]

Ta LBD. There are a few bikes that look similar but having the tank over the front wheel is the unique thing. The headlight is directly in front of the tank so some say the detonator and bomb are right together ha ha. Despite this there have been no reported explosions from Nzeta or Czeta riders.

Anyway Ive mangaed to put off til tomorrow what I could've got done today, so have procrastinated perfectly, and the pub has got in the way. Reports of hopefully avoiding explosions will have to wait til tomorrow.

[XRVrider]

All good, job done. Filled with water and brazed one stud in on the best tank, the other has rust inside and thin metal in spots cos of it. So that one's a almost a throw away. No problem with the water filled method tho.

Flushed both tanks throughly with water, and blew the car exhaust through them for 10 minutes. Dont know weather it helped, but the petrol smell inside the tank was much less after this. Filled them with water and brazed and welded with seemingly normal results. All went as if it was just another welding job.

Ta for the advice given here guys.

[_Shrek_]

All good, job done. Filled with water and brazed one stud in on the best tank, the other has rust inside and thin metal in spots cos of it. So that one's a almost a throw away. No problem with the water filled method tho.

Flushed both tanks throughly with water, and blew the car exhaust through them for 10 minutes. Dont know weather it helped, but the petrol smell inside the tank was much less after this. Filled them with water and brazed and welded with seemingly normal results. All went as if it was just another welding job.

Ta for the advice given here guys.

it's coz you put the car exhaust through that you had no problems, it gets rid of the fumes that would other wise explode

[Motu]

So long as it wasn't a Hillman Hunter with the choke on.But any engine warmed up will have enough Co2 to inhibit a flame.

[koba]

it's coz you put the car exhaust through that you had no problems, it gets rid of the fumes that would other wise explode

Correct. I know this the hard way.

[koba]

So long as it wasn't a Hillman Hunter with the choke on.But any engine warmed up will have enough Co2 to inhibit a flame.

I was dubious of that when I was using my dirty old Aircooled volksy so I made sure I got it nice and warm, I think I even leaned out the idle mix. It worked a treat, unlike when we blew one up as the water was pouring out faster than it was going in!

[_Shrek_]

Correct. I know this the hard way.

ditto :laugh: & I hope you got away with no scarring as i did

[koba]

ditto :laugh: & I hope you got away with no scarring as i did

Luckily I just shat myself.
Added about a litre to the tanks capacity too as it convexed the concave floor of the tank.