cutting propane tank?

admin

Ok I picked up a 120 lb propane tank for free.  It's no longer serviceable as a propane tank.  I want to make it into a grill.  My understanding is this tank has already been purged.  However I don't want to wake up dead.  That's less than desirable!  The person I got the tank from is a good buddy of mine who works for a fuel company that sales and installs a lot of propane.  He told me they use grinders with cutting wheels all the time on empty tanks that have the valves removed.  He told me the tank will not explode.  He told me worst case the gas flashes and burns.  But if the valves are removed it will not kaboom!  However this sounds dangerous to me.  It is my understand that propane is about 1.5 times heavier than normal "air" so it sinks and does not float up.  What I am thinking about doing is removing the valve and standing the tank upside down on the collar.  All the propane should sink out of the tank of there is any left.  I'll let it sit a few days just to do it.  I want to then set it right side up and fill with H2O dump out water and cut.  Anyway am I wasting my time or going the right way about this?  I don't want the last thing I here to be kaboom! Thanks!
Reply:This has been discussed a few times.http://weldingweb.com/vbb/showthread.php?t=99381Neutralize the methyl mercaptan odorant with bleach (or a solution of water and bleach). Rinse with water. Vent inverted until dry (gas is heavier than air).  I don't fill the tank with water but that would certainly force all the gas out. Cut using any method desired. I normally use oxy-propane as we're doing large tanks.
Reply:I have cut into quite  a lot of propane tanks, I used to remove the valve and then fill with water overnight, Now I just remove the valve and leave to stand for a little while, Then put the tank on it's side, put a 10mm bore pipe from the compressor thro' the valve hole right down to the tank bottom and purge with air for a couple of minutes. then immediately turn off the air,remove pipe and plasma cut or grind through, Never ever had even the slightest hint of remaining gas, Hope this helps,P.S. I was very apprehensive cutting into the very first bottle, Until you have done it a couple of times following a safe procedure.Lincoln SP-170 MigHypertherm powermax 45Lorch T220 AC/DC TigButters FM 215 synergic MigKemppi 180 adaptive mig RULES ARE FOR THE OBEDIENCE OF FOOLS AND THE  GUIDANCE OF WISE MEN.
Reply:I like the idea of filling with water, I guess leaving that overnight would get rid of the gas smell and fumes, surely that would be enough??
Reply:Put in a cup of bleach and fill with water to the brim overnight.  The methyl mercaptan (rotten egg stink) soaks into the metal over time.  If it's an old tank, it's probably worse.  Then drain it out and go to town.You didn't build that.'85 Miller AEAD-200LE
Reply:Last big one (300 gal)  I did I took off all the valves and purged it the best I could then lit it off with a highway flare outside.  After about 4 seconds of the most adrenaline producing 20' jet flame I have ever produced, it was done. It was so cool we put more propane in it and tried again, but we could never get the mixture perfect enough to reproduce it for a good video.  I have cut a lot of 300 gallon tanks without any issue.  I have also led propane fire trainings with the fire dept where we light off big tanks, up to 1500 gallons, they have never exploded but can vent huge flames that many spectators mistake for explosions. If you are really worried throw a chunk of dry ice in it, the tank will fill with co2 vapors. I don't know how much dry ice is needed, but I had to put several pounds in a 1000 gallon gasoline tank once to move it per inspectors code (they just don't know how to have fun)
Reply:Oh, and 3 of my sons went off to be explosive experts (0351) in the Marines, I can't imagine hanging around the shop influenced them. It was a good thing my shop is away from any populated area.
Reply:LOL thanks for the info.
Reply:Blackbart,I used to drill about a 1/4" - 3/8" hole in a 2 liter soda bottle cap, then give the bottle about a 5 -7 second spritz of propane from a small propane torch.  Screw on the lid, lay it on a piece of c-channel as a launch ramp, light it and watch out!  WHOOSH, like a rocket.  The noise is scary; I think the hot gas comes out at sonic velocity.  If you want to calculate how much CO2 you need:1 pound of CO2 is about 8.4 cubic feet. (Liquid or dry ice doesn't matter.)1 cubic foot is 7.48 gallons.I figure for cutting oil drums, one pound of CO2 per 55 gallon drum is probably good.(My son was MOS 1371 - Combat Engineer.  Build it, then blow it up.)  )"USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:I used a 30 pound one to make a pressure sand blaster. I took out the valve then filled it to the top with water. I then use a 2.5 " hole saw on the top where the valve was to cut the top out for the fill pipe. After that I dumped the water and stuck a lighted rosebud torch inside it and ran that until it was all dry inside. No popping or flaming at all as I think any gases left in it were burned out as the tank dried out. After that I hole sawed out the other 2 holes needed and welded in the fittings. Still operational today.
Reply:Yeah, the several second "whoosh" left us speechless.......the first words were Lets do it again!
Reply:Originally Posted by blackbartYeah, the several second "whoosh" left us speechless.......the first words were Lets do it again!