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Working on a fuel tank
thepest - 22/4/09 at 01:33 PM

What would be the safest option? I've been using this tank for a few years now and I am adding a fuel sender unit and I need to weld a return line into it.

I was thinking of running exhaust through it thinking CO would kill the fumes then fill it up with water to work on it. Is this sufficient or am I going to be working on a bomb?

Anyone had any experience on this?


coozer - 22/4/09 at 01:38 PM

BOOM


thepest - 22/4/09 at 01:48 PM


blakep82 - 22/4/09 at 01:50 PM

is expoxy resin/chemical metal petrol resistant? i'd maybe just go with that.
drill a hole and expoxy resin it right up


smart51 - 22/4/09 at 01:55 PM

Isn't petrol quite a volatile solvent? (in the literal sense of the word - it evaporates quickly) How long would you have to leave an empty tank open for all the residual fumes to leave? What if you rinsed it out with soapy water?

How about after leaving the tank open for a few days you warmed it gently. Surely the residue could be driven off before welding?


britishtrident - 22/4/09 at 01:56 PM

You really want to wash it out with degreaser followed by soapy water, then steam it for a few hours (one of those steam cleaner/wall paper remover gadgets is perfect for the job, this should get any fuel traces out from the seams.

If you also want to use car exhaust gas to inert it use the exhaust from modern car with a two way catalyst --- very little carbon monoxide and unburnt fuel


02GF74 - 22/4/09 at 01:59 PM

Mr Henderson was asking about this last week.... now I don't know how he got on but we've not heard from him since ...


Mr Whippy - 22/4/09 at 02:03 PM

quote:
Originally posted by 02GF74
Mr Henderson was asking about this last week.... now I don't know how he got on but we've not heard from him since ...






[Edited on 22/4/09 by Mr Whippy]


britishtrident - 22/4/09 at 02:08 PM

quote:
Originally posted by smart51
Isn't petrol quite a volatile solvent? (in the literal sense of the word - it evaporates quickly) How long would you have to leave an empty tank open for all the residual fumes to leave? What if you rinsed it out with soapy water?

How about after leaving the tank open for a few days you warmed it gently. Surely the residue could be driven off before welding?


It tends to lurk in the seams it can stay there for years. you don't get any trace of it untill you heat the tank --
The petrol chemical industry uses steam as heats it up and also has the useful property driving the gas/vapour out.


britishtrident - 22/4/09 at 02:09 PM

quote:
Originally posted by Mr Whippy
quote:
Originally posted by 02GF74
Mr Henderson was asking about this last week.... now I don't know how he got on but we've not heard from him since ...






[Edited on 22/4/09 by Mr Whippy]


Wasn't that a movie -- Big Feet and the Hendersons


twybrow - 22/4/09 at 02:14 PM

I welded above my tank with fuel in the tank, and just a piece of masking tape over the filler neck! I am still here to tell the story.... I am not suggesting you should not worry about it, but I do think some make it sound more dodgy than it really is!

If I was doing it again, I would use the exhasut fumes trick to be safe - but life is too short to be safe!


welderman - 22/4/09 at 02:18 PM

Welded up a cracked seam on a tank yesteday, filled with water, gave i a shake and emptied water and petrol bits out, was a bit scared to start with but once i got going was ok.

Its up to you though !!!


nick205 - 22/4/09 at 02:18 PM

quote:
Originally posted by twybrow
I welded above my tank with fuel in the tank, and just a piece of masking tape over the filler neck! I am still here to tell the story.... I am not suggesting you should not worry about it, but I do think some make it sound more dodgy than it really is!

If I was doing it again, I would use the exhasut fumes trick to be safe - but life is too short to be safe!



Risky at best


I've heard mention of filling the tank with sand before - no idea if it's safe or not though. Would have thought you'd risk sand in the fuel system for ever more too.

[Edited on 22/4/09 by nick205]


blakep82 - 22/4/09 at 02:25 PM

its the fumes that are explosive, so anything you can use to displace them would help i guess. water would be best.

but i wouldn't...

[Edited on 22/4/09 by blakep82]


Mr Whippy - 22/4/09 at 02:26 PM

quote:
Originally posted by twybrow
I welded above my tank with fuel in the tank, and just a piece of masking tape over the filler neck! I am still here to tell the story.... I am not suggesting you should not worry about it, but I do think some make it sound more dodgy than it really is!

If I was doing it again, I would use the exhasut fumes trick to be safe - but life is too short to be safe!


WTF!

I suppose you'd be quite happy to weld the hinges on a box of dynamite then???

Definitely the most mental thing I've heard all year!

I welded my old cortina's fuel tank years ago after flushing it with water and washing up liquid, then filling it up to the top with water...

it still went bang and blew the water out the filler neck all over the garage ceiling!!

[Edited on 22/4/09 by Mr Whippy]


twybrow - 22/4/09 at 03:44 PM

Mr Whippy - no I would not weld a hinge onto a dynamite box, as dynamite is explosive. Petrol needs just the right A/F ratio to explode (as we all know). As such, if you fill the tank with petrol, the A/F ratio is all wrong, and it won't go bang. The important thing is to ensure you don't have a load of fumes floating around the area.... Do you also buy into the idea that a smoldering cigarette is enough to make your car/petrol station blow up?

I take no responsibilitiy if anyone blows themsleves up!


jeffw - 22/4/09 at 03:58 PM

Years ago I had a leaking bike tank, nobody local would touch but suggested I took it to the guy who ran the local British Bike shop ....An old boy who worked there took it out the back and drained the fuel out......

He then lit a oxy-acetylene torch and put in the neck of the tank ...big sheet of flame. He then turned it over and welded the problem area, job done.

Always impressed me but not something I would try myself.


nitram38 - 22/4/09 at 04:56 PM

I spent 5 years of my life in a welding workshop where I have lost count of the number of used fuel tanks that I have welded/soldered and braized.
If you have no compartments that trap fuel, then wash it out with soapy water.
Put the opening of the tank on a running car exhaust for about 30 mins.
Finally test with a lit newspaper on the end of a stick/pole.
Never had on even as much as pop.


BenB - 22/4/09 at 05:01 PM

I saw someone who gas welded a fuel tank. Not surprisingly it was when I was working the burns unit. The heat from the torch pressurised the sealed (doh!!) tank nicely just in time for the torch to burn through the metal and ignite the pressurised petrol / air mix that came pissing out.

Not a pretty site.

At least with MIG the full face shield offer some protection. Little welding goggles just give you terrible panda eyes....


speedyxjs - 22/4/09 at 05:57 PM

quote:
Originally posted by BenB
I saw someone who gas welded a fuel tank. Not surprisingly it was when I was working the burns unit. The heat from the torch pressurised the sealed (doh!!) tank nicely just in time for the torch to burn through the metal and ignite the pressurised petrol / air mix that came pissing out.

Not a pretty site.

At least with MIG the full face shield offer some protection. Little welding goggles just give you terrible panda eyes....


Ouch!


mr henderson - 22/4/09 at 06:05 PM

I'm using one of the rubber bung and metal elbow units that were suggested in the recent thread on this subject.

Just drill a 1/2" hole, de-burr, push the bung in, then push the elbow in and that wedges it tight into the hole.

Cost was ridiculously cheap, less than a fiver

John


thepest - 23/4/09 at 06:07 AM

Thanks for the advice everyone! I'll get cracking on with it then, if you dont hear from me till next week then my insurance company is going to have a field day...