Weld on propane tank

[brightspark]

By the way the tube that I welded to the propane tank had another thing welded to hit, but that weld joint is leaking, can I just weld over the leaking holes or what do I need to do?

if the weld is sound but just pin holed yes but if weld is like Pidgeon crap no

 

[sardine]

I cut them with a 9" inch grinder, while they are still full of water, letting it drain out as I go, I have washed them out and then had a flame shoot out while cutting so I won't be doing that again.

 

[Bill Edwards]

I think there's probably a greater risk of a piece of metal in the eye from grinding, cutting yourself on burrs or burning yourself on a fresh grinder, oxy or plasma cut than there is of suffering injury from it once holding flammable gas.
Yes, there's risk to everything - but keep things in perspective.

 

[Farside]

I practised on a stainless beer keg before I did a gas cylinder.
I had to empty the keg first. That took a few days, funnily enough.
There was no trace of the contents when I got back to it.

 

[BarrieJ]

I cut them with a 9" inch grinder, while they are still full of water, letting it drain out as I go, I have washed them out and then had a flame shoot out while cutting so I won't be doing that again.

Sometimes there's an oily residue left in the bottle, particularly if it's been around a few years and it's impossible to know where in the bottle this might be, particularly if the bottle has been lying on its side somewhere, (maybe discarded by the travelling community?).
I've not had it happen to me but I know of one that went off like a jet (sounded like one too!) shot across the workshop and demolished a fuseboard and switch on the opposite wall (not a big workshop to be fair, single garage size). The guy had cut the brass valve off with a hacksaw, leaving a 1/4" or thereabouts hole, had the cylinder on its side and was welding legs on it, the oily residue had settled right behind where one of the legs was being welded.

I was in an area next door, brick wall and a bi fold door between us; there was a bang, a roar and a crash.

 

[gordon stephenson]

Never ever known one with oily residue, But you can't discount that somebody may have used the bottle for other purposes, They are quite often dirty on the inner walls,