Now I'm not one to tell someone to do something that will get them blown up, maimed, disfigured, killed, etc.
Propane is a liquid when under pressure, when exposed to atmospheric pressure, which is far less than the pressure that turns it to a liquid, it reverts to a vapor. That vapor is easily forced out of a tank by filling the tank COMPLETELY full of water (leaving no voids or pockets), or an inert gas.
See, I've dealt with a lot of locomotive Diesel fuel tanks, 3000-4000 gallon, that were damaged or cracked. We used to weld them with the tank completely full of Diesel fuel. Believe it or not, it works fine. That was the standard method for years. If the damage was major we emptied them and steamed them for 1-2 days. Then we started inerting them, much better solution. Very expensive for me
to do it, not so for a 3 billion dollar a year company.
As far as propane goes, what I've said goes. Check this link for more. The only exception I take is the last post by "mrbuzzsaw" who says "the only problem with propain (sic) is it gets in the metal and stays there". WRONG!
There is no way for it to "get in the metal". That is the old "pores of the metal" thing. Metal does NOT have "pores" and there is no way for propane to "get into it".
That said, read this -http://www.barbecuenews.com/forum/to...TOPIC_ID=10697
You have to take reasonable precautions. If you do, you should be fine.