By PeteF
#91170
Wheaters, all this talk of welding tanks makes me cringe.
You do know EXACTLY what you are doing and taking the correct precautions??
Just 'cos a tank is empty doesn't mean it can't explode.
By Daiwiskers
#91172
I'm not going to say how on a public forum but it is easy enough to do it safely

Gas bottles too

I am sure that Paul (Wheaters) knows what he's doing
By papasmurf
#91173
PeteF wrote:
Wed Jul 01, 2020 11:30 am
Wheaters, all this talk of welding tanks makes me cringe.
You do know EXACTLY what you are doing and taking the correct precautions??
Just 'cos a tank is empty doesn't mean it can't explode.

I don't recommend doing it at home, as it takes an expert, but it is safer to weld a full petrol tank than an empty one that has not been cleaned properly.
User avatar
By Wheaters
#91179
I might have made light of welding the tank but it’s definitely not something I undertook lightly.

The preparation took far longer than the weld. I ensured there was absolutely no liquid fuel inside, then allowed it to bake and drain upside down in the hot sun, with the cap off and the tap removed for a full day and then overnight (petrol vapours are heavier than air). This was followed by a very thorough wash and rinse out with very hot water with a lot of detergent. That was then allowed to dry out and hot air used to complete the job.

I wouldn’t try this on any container where I couldn’t ensure it was absolutely cleaned of fumes; because the fuel tank could be removed and swilled around this was relatively easy but obviously the job couldn’t be rushed.

After about 36 hours of preparation, the actual welding process took about 30 seconds.

A friend of mine who does this sort of thing for a living on vintage cars uses piped in car exhaust fumes or Argon welding gas to displace the air because some of the tanks can’t be removed from the vehicle. I reckon my method is actually safer.
User avatar
By Wheaters
#91184
papasmurf wrote:
Wed Jul 01, 2020 12:27 pm
PeteF wrote:
Wed Jul 01, 2020 11:30 am
Wheaters, all this talk of welding tanks makes me cringe.
You do know EXACTLY what you are doing and taking the correct precautions??
Just 'cos a tank is empty doesn't mean it can't explode.

I don't recommend doing it at home, as it takes an expert, but it is safer to weld a full petrol tank than an empty one that has not been cleaned properly.
Until you blow a hole in it..... :shock:
User avatar
By stinkwheel
#91189
In fairness, I think it's one of those things people go batshit about pretty unecessarily.

How big an explosion can you get from an empty motorcycle fuel tank with the lid off if it goes off bang? I mean yes, it could make a fair old bang and give you a goodly jet of flame up out of the filler cap if the vapour mixture gets exactly right but is the tank itself going to grenade? Can't see it being any worse than when we used to deliberately explode the exhausts of our 2-strokes while decoking them by pouring petrol in, lighting it then blowing an airline down them.

If you're welding, you ought to be wearing a minimum level of PPE so a flash explosion isn't going to hurt anything but your underpants and if you aren't prepared for stuff to catch fire when you're welding, you're in for a surprise.

I have an old petrol tank somewhere. Also have an ignition coil and sparkplug. I might deliberately blow it up sometime just to see what happens and post the video on youtube.

Probably the safest way would be to pour in some petrol and set it on fire then weld it while it's on fire :lol:

I reckon it's mostly that welders simply don't like welding petrol tanks because they are usually thin and far rustier than they look. The explosion risk is a good excuse not to. If I had to fix one of those tabs, I'd probably go with braze or silver solder over welding anyway. Much less chance of making more holes than I started out with.
User avatar
By stinkwheel
#91193
Yeah, although that's a large, almost totally sealed car tank. I strongly suspect a motorcycle tank with the lid off would give you more of a woosh out of the open cap. Explosions not involving high explosives are dangerous when contained, if the pressure has somewhere to go, it's a lot less of an issue. Not saying it couldn't make a hell of a loud bang mind.

All speculation though, must try it some time. Ask me about exploding cast-iron downspout flame-organs at a rally some time.
By Daiwiskers
#91194
Many years ago there used to be a scrap yard at the bottom of my street , one day there was a explosion,
The usual method of dealing with scrap cars was drain fuel that was stored and sold to locals
Then fill tank with water then the cars would be cut up with the gas axe
The day of the explosion the fella apparently drained the petrol then missed filling the tank with water,

No one knows for sure he didn't make it!

Take care all Dai


Mind you beer cans half filled with petrol placed around a bonfire give a jet of flame not a explosion
But there again your igniting the fuel in the can not the vapour
By Daiwiskers
#91195
Too late to edit again


The beer can ! the petrol heats up gives of vapour the vapour ignites not the petrol

Sometimes things just don't come out like I mean them too

@Stinkwheel if your going to do it please do it from a distance and behind cover just in case

Take care all Dai

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