Flushed and drained the tank several times, then turned it upside down on a purlin base to let the remaining propane flow out what was the top valve. I checked it with my LEL meter, and it was completely void of propane after a couple of days. I feel comfortable cutting it now.
I'm sure you've researched how to safely cut into an old large propane tank, but I'll add my 2 cents anyways.
From what I understand, there's a possibility that residue from the propane may be impregnated into the steel walls of an old tank, and the heat from cutting might release the residue and lead to an explosion.
If I had to cut into a big ol' propane tank like the one you have, I'd first fill it completely with water, and as soon as the water began leaking from the cut I'd stop cutting and insert a hose into the tank and purge the growing air space with an inert gas, such as argon or nitrogen... Or better yet, I might just save myself some stress and pay the guy at the local welding shop to cut the initial opening... lol
At first, I was thinking you were gonna build a big ass barbecue smoker, but that nice looking stand you've built looks to be too tall for that, so now I dunno.
