Welding a fuel tank (safely)

[fingers99]

Jugs is right. A new (car) tank costs maybe 60 or 70 quid. If it goes wrong, you may never earn £60 again............

 

[Pete.]

I guess if we're talking a car tank with it's long filler neck it might take somewhile longer or require a forced purge, but an open tank left out in the sun will soon flash-off all of it's combustible vapours/liquids. The tank pictured there had the filler removed from the top and the fuel level sensor removed from the underside, and was bone dry with hardly even much smell of petrol when I cut it open.

 

[hotrodder]

Re. welding petrol tanks + safety. It's pretty much all been covered but if i can just relate a tale...

A mate i occasionally do some welding for used to swear that running exhaust fumes through a tank would render it safe until one popped on him. Fortunatly aside from his pride and underwear all he suffered was a sore jaw when the tank jumped up and clobbered him. Didn't fit back in the car afterwoods though- VERY different shape

The way car tanks are made there's often a long seam that can trap residue/'varnished' fuel. Add a load of heat and...

 

[snowcat]

Still, welding petrol tanks is generally a bad idea, at collage many moons ago we were told not too, If you are happy in your skills and techniques then good, however people often read forums as Gospel, Its a good idea to always ere on the side of caution when giving advice especially on something that WILL if you get wrong seriously injure or Kill you.......you may be fine taking short cuts, BUT someone reading it may not...

 

[MJG]

Well for the record, I left my fuel tank empty, flushed with hose water for about 30mins, left standing with washing up liquid twice (after a rinse etc), then after reading something about professionals using caustic solution I stuck some washing powder in the tank and left to stand for a day, then emptied it all out as best I could and left to stand for another day or so. My brother was more of a daredevil and went upto it with a lighter with no flames. Smelling the tank it just smelled clean and of washing powder, but still I chucked a flaming rag onto it and not even a whisper of fire or explosions. I suited myself up with goggles, face mask, a hoody on top of my t-shirt, welding gloves, and a disposable painting type mask for my nose and mouth. I then angle grinded/hacksawed it in half, all was well. I've since repeatedly tried burning the tank but it does nothing, so I'm now happy to weld it.

Just as a note, I would always be VERY careful, but it seems the process of using detergents and water to wash it all out seems to work pretty well in this case at least.

Might also be worth noting my fuel tank was not rusty at all, it does have the pressed seams which I was concerned about but they are clean seams with no corrosion so if yours were a bit manky it may help hold fuel in there I don't know.

Thanks for all the concern and safety talk though guys, it could have saved my life if I was the irresponsible sort to just dive right in.

 

[Drains]

Re. welding petrol tanks + safety. It's pretty much all been covered but if i can just relate a tale...

A mate i occasionally do some welding for used to swear that running exhaust fumes through a tank would render it safe until one popped on him. Fortunatly aside from his pride and underwear all he suffered was a sore jaw when the tank jumped up and clobbered him. Didn't fit back in the car afterwoods though- VERY different shape

The way car tanks are made there's often a long seam that can trap residue/'varnished' fuel. Add a load of heat and...

MJG, Glad you're sorted.

Hotrodder - your mate isn't alone in recommending a dose of CO to purge the tank with. The truth is, as he found out, CO can burn (unlike CO2). CO is a major constituent of woodgas - which people ran vehicles on in WW2.

 

[Covbandit]

Exhaust fumes

I have a mate that uses the exhaust method he uses a petrol engine for his though never had any probs, another mate used to have a lot of welding to do on Coventry Council lorries, the diesels he never bothered emptying the petrol ones he emptied as best poss and flashed a torch in the tank one big pooooof then got on with welding it

Good Luck with either

 

[jugs]

I have a mate that uses the exhaust method he uses a petrol engine for his though never had any probs, another mate used to have a lot of welding to do on Coventry Council lorries, the diesels he never bothered emptying the petrol ones he emptied as best poss and flashed a torch in the tank one big pooooof then got on with welding it

Good Luck with either

NO Pete thats just silly, I know 2 blokes that have done that, one just lost 1 eye, 1 ear, hair and is deaf. The other lost nose lips & most of his fingers. You may have got away with it this time but before you do it again visit your local burns unit.

You may like to look at this it is film make up, but accurate.

We all know blokes that "get away with it" hostpitals & graveyards are full of the ones that didn't.

 

[frankentrike]

mt the tank,put an air hose in the outlet with the cap off.throw tons of air through it.use a lonnnnggg kitchen match tied to a lonnnnnggg stick .[about ten feet].light it.stick it in the hole.if it go boom,then you didnt get all the vapor out.works 9 out of ten times[#10 is kinda loud],,,,,feel like gambling?no ,seriously,be careful!gasoline vapor BAD!

 

[rikrobson]

or there's the Canadian way

http://www.youtube.com/watch?v=tD4K...04E5A96B&playnext_from=PL&playnext=1&index=36

 

[bozzza]

http://www.youtube.com/watch?v=tD4KiQEnxwQ



Video of someone welding fuel tank full of fuel

 

[BeNos]

i think a tank repairer ive seen puts them in a big furnace and basically burns them out before welding. this way it removes all the gasses by burning it out. so no more explosion when welding them.
not 100% on the specifics but seems logical to me.

 

[aametalmaster]

i think a tank repairer ive seen puts them in a big furnace and basically burns them out before welding. this way it removes all the gasses by burning it out. so no more explosion when welding them.
not 100% on the specifics but seems logical to me.

I guess there are retards born everyday. The proper way to do it is clean then sniff it with an LEL or explosion meter. If you get LEL clean it some more until you get a ZERO LEL reading. I worked in a refinery and that was my job and you have to be 100% sure that it is safe before any hot work on it...Bob

 

[jimzzr]

I guess there are retards born everyday. The proper way to do it is clean then sniff it with an LEL or explosion meter. If you get LEL clean it some more until you get a ZERO LEL reading. I worked in a refinery and that was my job and you have to be 100% sure that it is safe before any hot work on it...Bob

Even this isn't completely safe. The main issue is that starting hot work will then drive fuel out from pores or from under paint films. In a relatively small volume this might be sufficient to get above the lower explosive limit. This particularly true for lower volatility fuels (ie. high flash point) like diesel which wouldn't at room temperature create a flammable atmosphere above them. However, heat diesel to a little over 60 degrees centigrade (minimum closed cup flash point of diesel is 60) it will form a flammable atmosphere above its surface.

Incidentally in normal usage petrol tanks are safe because the fuel/air mixture is too rich to (fuel concentration above the upper flammable limit) and diesel tanks are too lean (below the Lower Flammable Limit).

Personally for a small tank I'd be tempted to clean the tank as much as I could and then rig up some form of inerting (i.e. nitrogen, argon or CO2). With good mixing a continuous purge , after five tank volumes have passed through, will have reduced the oxygen concentration in the tank to around 1% vol (for hydrocarbons the Minimum Oxygen concentration for Combustion is around 10%vol). In this condition gases exiting the tank (with any quantity of fuel) would not be flammable when mixed with the surrounding air (as well as inside the tank)

For the record exhaust gases are mainly water and CO2, for Cat equiped engines at least CO content is trivial and nowhere near enough to render the mixture flammable.

Other possible techniques would include filing the tank with say glass beads or sand - if channels between particles is small enough this will prevent flames propagation. This is sometimes used with banks of lead acid betteries to prevent hydrogen explosions during charging. Aircraft fuel tanks can (but generally aren't for passenger aircraft) be fitted with expanded metal networks or reticulated foams, which also prevent flame propagation/explosion.

That probably far more info than required so I should probably stop now.

Jim

 

[fridgeman999]

I have followed this post over the last few days, and just wanted to add my bit.

I have just today repaired my fuel tank on an old Renault. I used silver solder with oxy/ acetylene, as metal was so thin.
This was after i had steamed it out with a wall paper stripper (flat plate removed), and hose up filler tube, and the tank almost full with water.
Yes, maybe i was lucky, and my bum has never been so tight, but after looking for months for another tank, it worked a treat.

Chris.

 

[malcolm]

I've probably got a spare tank if that's any help Depends on the model year - I'm good for early ones but forget which one you have. Do mail before doing anything so daft again, though full with water does increase your chances.

 

[the artfull-codger]

dear me all this trouble to repair a small hole in a pertol tank,I've repaired a number of petrol & diesel tanks with small holes in them & all I do is drain them & leave the top off for a couple of days then clean the area with coarse wet & dry then with an active flux soft solder the hole, even putting a patch on if need be, of course it's done with a decent size SOLDERING IRON hence no flame or danger.

slan go fol

 

[outbackjohn]

ex mot welder now retired

the garages that i workt at seems very reasnable as to price for welding as quite often they could charge more for me just doing mots.now for my problem wire feed moter for snap on 2160 mig any ideas as to where i can get my clammy claws on one thanks .i always filled tank to top anhttp://www.mig-welding.co.uk/forum/images/smilies/waving.gifd left cap off http://www.mig-welding.co.uk/forum/images/smilies/waving.gif

 

[Wozzaaah]

John, it looks like you've got two posts in one here, is it a reply to this one or a request for a motor or both?
Can you edit it accordingly please so I know which section it belongs in.
Thanks.

 

[Covbandit]

Did my tank in the end put it on or as close to a diesel exhaust revved it up for about 5 minutes and it was neutralised no pooooooof bang or anything didn't smell of any fuel what so ever when I chose to weld it.
No hospital or grave yard.