The 'Eal' Story on Old Propane/Butane Tanks?

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I appolligize for asking this question on two different threads.Can anyone enlighten me on the process of converting retired Propane/Butane tanks to BBQ Tanks?I have heard storys that you have to fill them with water before putting a torh to them.K.O.
Reply:Again, you have to figure that propane is only a gas.  Once that gas is expelled, only a little bit of it is left in the stagnent air and that is the 'potential' explosive part of the recpie.  Once you purge that from the area(via water, air, co2 or whatever you wish) it's gone.  You might smell something afterwords, but that is the chemical they put in the gas to let you know it's gas.  The gas has no smell normally.  So the manufacturers put that there to keep people from lighting up in an area that could be potentially explosive and the chemical settles in the container.Common sense in an uncommon degree is what the world calls wisdom.
Reply:Like Brainfarth says, it's a gas so there will be no liquid residual in there, but you will want to purge the heck out of it. Make sure that all ports that have plugs and valves have those removed so the tank can vent. Flush as much as you need to to feel safe. The stink goes on for a long long time, so that can't be your indicator as to whether there is anything left in there or not."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:It occurs to me, that "filling" with water might cause a problem if that water gets heated and expands (or steams) when working the tank...  Purge, yes -- fill, perhaps no.Hey! Bring the camera...Is it still hot?   $%#^%^#  Guess so...
Reply:So, the propane itself does not become inpregnated into the metal, as I've been told?I just need  make sure I get the gas out of the tank?K.O.
Reply:Flush with water then leave a bit in the bottom of the tank.  Heat the bottom until the water starts to boil off.  Steam expands about 1700 times when it changes from water to steam.  Once the tank is full of water vapour/steam there will be no available oxygen.   Although you might have a the smell of odourizer there will be no fuel vapour left.
Reply:What lotechman said...     If it makes you feel beter, I cut and welded one a while back for an air compressor - no problems...But, I did it in concert with an auto body class that I was taking through a local technical college (at our high school) and you should have seen all the guys run when I brought in that tank and lit the torch...  Hey! Bring the camera...Is it still hot?   $%#^%^#  Guess so...
Reply:>================================================Sure it does, just as there can be moisture in metal too.  But, unlike water, propane wants to be in a gaseous state so it doesn't lay there and sog. It vacates the metal in the absence of extremely low temps or lack of pressure. And in a open environment, the propane molecules are trying to occupy the microscopic pores in the metal along with natural air and moisture. How much vacant space can there be in rolled steel? Here is what could happen to spurn the "impregnated"theories: Someone could have taken the valve out of a tank. Propane molecules, being heavier than air, would lay in the tank as vapor.  Fire up a torch just after taking the valve off and whooooomp! Bomb.  Remember the butane lighter and beer can trick? Same thing.  That's why you should purge. Purge untill you feel comfortable. But common sense should prevail. There is no oily residue to turn into flammable vapor, no volatile liquid entrapped in the metal  to turn into flammable vapor.But again, make yourself comfortable. You'll get a better result."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:One other note. On the small tanks I fill them clear up with the wife's smell purty dish washing liquid and Lisol try try and get the stink out. Slosh it around, drain the tanks completely, blow with air to dry them out a little and cut away. They don't blow up but they still stink. If you do wash a tank, don't use additives that might turn caustic with heat. Plain water is probably the best."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Hi, I'm new here,+ don't want to step on any toes...........But, I've been using Propane Tanks for my art for Years..........From Bells, to Wood Stoves, to Driveway Sealer Sprayers, to a 45' X 16' Self Powered Brage, in daily use on the St. Lawrence river.......Propane is heavier than Air.... if you remove the valves,+ or all the plugs from a propane tank, and stand it so there is an open hole at the Lowest Point,After a couple days, It's as Safe as it's going to get.............This Isn't Gasoline............Propane is a Very Different animal........  No Lingering Effects......I've cut up 100s of these things with Ox/Ac torches............  No Boom.........