best practice for welding on a car

[BrokenBiker]

ive done god knows how many patches to cars, and exhasuts, but the exhausts have always been on a bench rather than on the car itself.

the megane failed the test today on lower arms and obviously the blowing exhaust. i have decided that i am going to replace the centre section now aswell (why not? its the only bit left to replace anyway) so the plan so far is, drop the cat and centre off the car (its already been welded together), measure up, cut in a decent place, weld new centre pipe on...thats easy enough. have done it a few times before.

the next bit is the tricky bit. i have given up and i want to weld the centre and rear sections together to eliminate any chance of it blowing from there...but it is right next to the fuel tank (plastic).

i think i can just about squeeze enough space for the torch if i drop both exhaust hangers and jack the rear of the car up to lower the rear beam as far as it will go, allowing me to get a weld all around the joint, but the bit that is concerning me is the petrol tank being so close to the joint.

i managed to revive my gasless mightymig earlier, its a bit rough but should do the job well enough to get me an mot.bought a reel of wire so once i pick the centre section up im ready to go with it.

 

[rory1]

So what are you asking BB? If we think it's safe for you to weld next to The fuel tank?

The only man that can answer that question is you. Your next to the job - you need to look at the risks and determine if they are acceptable. If they are not acceptable then you need to devise another way around the problem. If you can't determine the risks then the job should be left to someone else.

 

[slim_boy_fat]

....but it is right next to the fuel tank (plastic).

That'd be close enough for me to let someone else do the job/take the chance.

 

[BrokenBiker]

Well ideally I would like to know if there is anything I put against the fuel tank to eliminate the risk of a spark melting it's way through. I was thinking of gaffa taping something like an old towel to the tank, doubled up and then spray it with water until it's saturated

 

[slim_boy_fat]

Fire blanket?

 

[Justme]

Having once welded in the boot of an old mini that burst it flames with my head in the boot due to the fuel tank being in the boot & the rubber hose being a bit on the leaky side, I would not weld near a plastic tank ever.

 

[Justme]

Reading that back, I now realise just how lucky I was all those years ago to have lived let alone not had any physical scars.

The mini however needed a complete new interior, 4 tyres & full respray.

 

[BrokenBiker]

Fire blanket?

Haven't got one. I have some flame proof overalls that don't fit anymore...would they be any use?

 

[Tinbasherdan]

id do it , and yes bunch the overalls up and wrap them round the tank

 

[slim_boy_fat]

I'd not jerry-rig something. How big a cover for the tank would you need, and how much is your life worth? See these....

http://www.amazon.co.uk/s/?ie=UTF8&...vptwo=&hvqmt=b&hvdev=c&ref=pd_sl_6idj4rvqce_b

Personally, I'd let someone else do it. I know someone who was trapped in a pit when the car he was working on caught fire - wasn't pretty.

 

[BrokenBiker]

That's the confidence I was looking for...lol.

The actual fuel pipe connections are well out of the way, and I have chalked them to make sure they aren't leaking at all, no damp spot after an hour is good enough for me.

I will tape the overalls to the tank in as big an area as possible and just get it welded up quickly.

 

[rory1]

Flame retardant overalls will stop a flame but they will still radiate heat into the plastic tank. Im not being a neigh sayer and being doom and gloom but a pair of flame retardant overalls won't stop Heat

 

[Tinbasherdan]

Flame retardant overalls will stop a flame but they will still radiate heat into the plastic tank. Im not being a neigh sayer and being doom and gloom but a pair of flame retardant overalls won't stop Heat

I'd think for what he's likely to be doing, ie tack and pause, tack and pause, radiated heat at that level isn't going to be an immense factor, I'd say the exhaust would be running at a fair temp when given some welly anyways

 

[anjum]

Put some wet towels under the flame proof overalls.....

and have someone standing by with a CO2 extinguisher and a large first aid kit

 

[doubleboost]

I use a piece of aluminium exhaust heat shield
A mig spark will never melt a plastic tank
Safer with a full tank as well
If you need to ask don't do it

 

[J.B. Welding]

Hi BB. Is there no way you can weld on a slotted sleeve or two, to allow you assemble the zorst with a boring old exhaust clamp. If it was diesel I'd say fire in, but petrol and welders and your head don't really make a good team, especially if your working undernieth off ramps and not a lift. There's all the pipes and breathers around not just the thick plastic tank.

 

[BrokenBiker]

Have had a new plan, we'll sort of anyway. Still weldi g the exhaust on the car, but was looking through my shed earlier and came across a bit of the heat shield that I pulled off ages ago because it was rattling about. It big enough to cover the exposed bit of the tank so I'm going to use that

I have also had a look and if I unbolt the cat I can rotate the exhaust down and get much better acces to the top, and it moves it away from the tank a few more inches

Just noticed John mentioned about he heat shield also