Welding on a fuel tank (jerry can)

I would like to convert a 5 gallon steel jerry can into a fuel tank to hold diesel fuel. To that end, I will need to add three fittings to it
(fuel intake with tube almost to the bottom, fuel return, and breather fitting).
Presently this jerry can contains diesel fuel.
The way I want it done is to drill holes in the top of the can for the three aforementioned fittings, and TIG weld them on.
To avoid explosion, my plan is to drain all diesel fuel from the jerry can, and fill it with water almost to the top, so that ony very little space is left between water and where I will drill and weld.
Would that be a basically safe thing to do. thanks
i
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On Mon, 23 Nov 2009 10:07:17 -0600, Ignoramus25468 wrote:

Add baking soda to the water. I have brazed a VW fuel tank this way.
I have stick welded a gas tank on a forklift that was part of the frame by filling the tank to the top with gas and catching the overflow from expansion in a pan of floor dry as I welded.
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On Mon, 23 Nov 2009 10:07:17 -0600, Ignoramus25468 wrote:

Add baking soda to the water. I have brazed a VW fuel tank this way.
I have stick welded a gas tank on a forklift that was part of the frame by filling the tank to the top with gas and catching the overflow from expansion in a pan of floor dry as I welded.
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Heh, I had to drill a hole in a motorcycle gas tank to enlarge a breather hole in the collar that went down into the tank a bit to help stop gas from rushing out after a crash (I assume that is what it was for).
Did it with the tank filled to the brim with gas, with a wet rag ready to just plop down onto the filler opening if the drill bit or the brushes ignited the fumes.
Dave
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I think I would avoid finding out. Three things come to mind.
First, you could weld the fittings to the cap. (Run the pick up line diagonally)
Next, you could use gasketed fittings rather than welding them.
Or, buy a new can for the project.
To answer your question I do not think a water purge is a good idea. I think the way to weld a fuel tank is to purge with an inert gas, and keep the tank under a positive pressure with the purge gas while welding. Chunks of dry ice might be viable.
As a matter of first impression, a new can would be cheap enough not to risk a failure of the purge and the resultant explosion.
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It is not a purge, the jerry can will have water filling it almost to the level of where I will do welding.
i
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Iggy, fill it half-way full of hot water, add about a 1/4 cup of good liquid detergent, and WASH it out. Then rinse, and see if you still smell fuel. If so, repeat until it's only a hint of a smell.
THEN fill it almost full of water, and leave the cap off while welding, so that if there is a small explosion in that tiny volume, it will vent harmlessly.
I modify acetone and racing fuel drums thus all the time.
LLoyd
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On 2009-11-23, Lloyd E. Sponenburgh <lloydspinsidemindspring.com> wrote:

Lloyd, yes, I agree. I will flush the tank with hot water a couple of times, and then fill it to displace ait prior to welding. With the fill cap off, at worst it will be a little whoosh.
i
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you'd think it's electro-galvanized wouldn't you? i'd think you're going to have to remove the zinc inside and outside to do the tigging. would soldering work? brazing would be a much hotter process huh? brazing would burn off lots more of the galvanizing. i think if it were me i'd just keep washing it out till there were no vapors.
b.w.
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you'd think it would be electro-galvanized wouldn't you? i'd imagine you'd have to remove the zinc (closely surrounding the weld area) on the inside and the outside to do the tigging. i think if it were me i'd just keep washing it out till there were no vapors.
b.w.
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Doesn't anyone solder anymore? Use two big coppers, heated by a torch a few steps away from the tank and above it, then there wil be no source of ignition. Just keep swapping coppers as they cool. http://tinyurl.com/ybh4d86
Since you are planning on TIG welding, we know you have Argon. As it is heavier than air, plug the other holes and fill it from the top, no oxygen, no fire.
I have heard of tanks filled with water still going off, the fumes will still be in any air space, so the preceding two methods are safer.
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I have done this many times.first wash out tank with liwuid gunk degreaser. flush it good with water.but tank on bench.stick airhose in tank low preasu re.leave tank sit 5 minutes.leave airhose in while welding.no stangent fume s no explosion.a old mortorcycle mechanic taught me that 50 years ago
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On 1/4/2020 3:50 PM, snipped-for-privacy@gmail.com wrote:

I did something similar on MC tanks, but used CO2 because its inert and heavier than air.
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wrote:

That's how I repaired the oilpan on a '65? Riviera ---
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On Sat, 4 Jan 2020 14:50:31 -0800 (PST), snipped-for-privacy@gmail.com wrote:

filling it with co2 from a fire extinguisher works pretty good.
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On 1/4/2020 5:49 PM, Clare Snyder wrote:

Argon or CO2 either one , if you happen to have welding shield gasses on hand . Big plus is that it leaves the extinguisher usable for it's intended purpose .
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wrote:

Disn't have sheilding gas - so I just sent the apprentice out to the safety supply to borrow a 5 pounder
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Would engine exhaust work?
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Jim Wilkins wrote:

Yes it will
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wrote:

Assuming the engine is running efficiently and not sewing large amounts of CO and unburned hydrocarbons, yes.
I would be cautious about making that assumption using exhaust from something other than a properly functioning emmission controlled vehicle - don't, for instance, use your lawn mower or an old gasoline tractor - - -
From OSHA
What are fire hazards and extinguishing media for carbon monoxide?
Flammable Properties: EXTREMELY FLAMMABLE GAS. Can easily ignite. Can readily form explosive mixture with air at room temperature.
Suitable Extinguishing Media: Carbon dioxide, dry chemical powder, appropriate foam, water spray or fog. Foam manufacturers should be consulted for recommendations regarding types of foams and application rates.
Specific Hazards Arising from the Chemical: Gas or vapour may accumulate in hazardous amounts in low-lying areas especially inside confined spaces, resulting in a health hazard. Heat from fire can cause a rapid build-up of pressure inside cylinders. Explosive rupture and a sudden release of large amounts of gas may result. Cylinder may rocket. In a fire, the following hazardous materials may be generated: Very toxic carbon monoxide, carbon dioxide.
? What are the stability and reactivity hazards of carbon monoxide?
other ignition sources.
contact with: oxidizing agents (e.g. peroxides), halogens (e.g. chlorine), metals (e.g. aluminum). Not corrosive to: aluminum alloys, stainless steel.
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