fuel tank

[bluebobtail]

Hi there, i'm modifying my alloy fuel tank. i have a few issues with it. at the moment it just has flanges bolted to the tank where the return and breathers are and no drain hole.
Im wanting to change it and have bsp threaded fittings in to the tank and move the return out of harms way.
The questions are,
1- do i use a 10mm flat plate weld all the way round then drill it out then drill it out and tap it?
2- use a solid ali tube. drill out tap and weld it to the tank?
3- Is there a good way of reducing any risks before welding without having to start from scratch?

The tank has been used with diesel.
It will be off the car and completely empty.

Help advice would be appreciated.

Thanks

 

[Angusdog]

First off, I have absolutely no experience with fuel tanks. But a search will drag up a few threads and a open a whole can of worms. There's plenty of theories: flushed empty, filled with exhaust gas / welding gas, filled with water, filled with petrol. The last one, although sounding like a recipe for disaster, may well be safe but I'd like to meet the man who tries it (then run away very quickly). The safest method (from my inexperienced point of view) was flushed constantly for ages (days), then filled with inert gas i.e. welding gas.

I'm sure others will be along shortly with more experience.

 

[Mad Mick]

Hi All,welding of used fuel tanks should not be undertaken lightly.Plenty of advice on the HSE site.Regards,Mick.

 

[PTvor]

A friend told me recently that in 1960 he had a 500 Matchless. He came off and dented the tank and broke off the fuel tap. He didn't know how he was going to get the dent out. He filled the tank with water and soldered the tap back.

Bang! The tank took off and landed ten yards away and the neighbour came out to find him unhurt but dazed on the driveway. However, the fuel tap was soldered back and the dent was neatly pushed out from the inside.

Soldering/welding fuel tanks which have been used is a dangerous thing to do and if you try it, your experience might not be as happy.

 

[wyn]

An aluminium tank holding diesel shouldn't have the corrosion and residue problems of a steel tank. It should clean out quite well to be able to weld on it.

 

[bluebobtail]

Thanks,
Would it just be easier to build up a tab rather than weld a flat plate to it?
As i would have to buy the plate, probably a off cut. But have some rods all ready.

 

[Mad Mick]

An aluminium tank holding diesel shouldn't have the corrosion and residue problems of a steel tank. It should clean out quite well to be able to weld on it.

Hi All,sorry Wyn,but I do not follow your logic,regards,Mick

 

[wyn]

Hi All,sorry Wyn,but I do not follow your logic,regards,Mick

The way i see it is that the majority of tanks that need welding are steel and would be subject to a fair bit of internal corrosion, which may be why they are being welded. This will more than likely mean a fair bit of internal rust and rubbish soaked in fuel. This would be a bit of a nightmare to try and remove it all which would probably not work well and why it is dodgy.

An aluminium fuel tank is more likely to have less corrosion or none at all meaning it's easier to clean out with no surfaces for any sort of fuel soaked residue to hang about in. The diesel is much less volatile than petrol and would need a bit of effort to make it go bang.

But this is only my opinion.

 

[davenport]

we often modify diesel tanks from HGV`s....

ripsaw or jigsaw the offending area out.... a quick blast with the karcher.... then strike up the TIG and buzz it up...

diesel is far more forgiving than petrol...

 

[Mad Mick]

With the greatest respect to all,there is no way that I can agree with what is being proposed re welding used fuel tanks,regards to all,Mick.

 

[langy]

I agree with Mick welding tanks is very dodgy, I won't touch them these days as its not worth the aggro, a lot of rad repariers used to do this job but most won't touch them these days.

Couldnt you drill holes and use a skin fitting ??? this would be much easier.

With the greatest respect to all,there is no way that I can agree with what is being proposed re welding used fuel tanks,regards to all,Mick.

 

[bluebobtail]

A skin fitting? Sorry i don't follow

 

[outofthefire]

I've been asked to repair a vintage tractor diesel tank its washed out and I will fill it with argon prior to welding, but I asked one of my colleagues at work today if he'd welded any diesel tanks and he has twice both full of diesel the diesel absorbs the heat.

 

[Mad Mick]

Hi All,I rest my case,regards,Mick

 

[Angusdog]

My mechanic is quite happy to weld fuel tanks, I don't know his method (and don't really want to). I suspect if I tried it the result would be predictable...

 

[Drains]

I asked one of my colleagues at work today if he'd welded any diesel tanks and he has twice both full of diesel the diesel absorbs the heat.

I've crossed the road in front of a bus more than once - not been run over yet! Doesn't prove much though does it?


Diesel is far less dangerous than petrol as it vapourises/ignites at far higher temperatures (and pressures). Small tanks are far less dangerous than large ones too.

Personally I'd not touch a petrol tank without feeling absolutely sure without question that there was no chance of any vapour being present. Diesel, I'd be less concerned about as a dangerous substance, but I'd still want no vapour - the difference is that vapour is less likely to be present.

I'm not telling anyone to do anything though - you make your own decisions...

 

[langy]

To fit a skin fitting you put the main body of the fitting through say the filler neck on a piece of wire then when in position you fit the nut and seal outside and tighten, easy

A skin fitting? Sorry i don't follow

 

[bluebobtail]

ah i see, a bit like a bulkhead fitting?

 

[bluebobtail]

I dont want to sound funny, but is welding a gas bottle a lot more dangerous than welding a empty diesel tank?
I may be barking up the wrong tree but surely its worse??

The skin fitting is sounding a lot safer to me.

 

[langy]

yes like a bulkhead

ah i see, a bit like a bulkhead fitting?