This is my thing.. welder/machinist/ mechanic in a forklift shop..
The way that works for me is to remove one of the larger plugs
or bungs and prop/ rotate the tank until the opening is at the highest
point and fill it with water. jog or roll or jiggle the tank to make SURE
alla the air is out.[fumes] do this al least twice. lay it down in the position that U want and fill it one more time. fill it as far as possible.
I leave it about a half inch low on water and light a torch and stick it in
Now before U start downrating my ansestors, think about it.. If You
have filled it with water a few times it means that U have pushed ALL
the fumes out with water . If it is fulla water, it CAN'T be fulla fumes.
The reason that I fill it with water except for a half inch or so at the top
and stick a lighter or torch inna hole is because it makes you a WHOLE
lot more comfortable with it. Decreases yer pucker power a BUNCH..
The worse I have ever had happen is the time I probably got a bit lax about making sure it was FULL of water a coupla times. It flashed over
and just about gave me the green apple quick step. But being full
of water except a half inch and the plug out it just went ''Whoosh''
and it was gone. It just made me more careful next time.
Nitrogen as a flush works well also. Don't try the exhaust trick
because of the danger of unburnt fuel. always cut it as full of water
This is the way I cut the lp tanks at work for disposal because
the scrap yard will not accept them unless they are cut. If you don't
want to take a chance on cutting it yerself, it just means yer normal..