Does a propane tank absorb propane?

[Haywire]

I'm getting ready to do some test cuts on a 20lb propane tank in preparation for converting a 40lb tank to a grill. I read someplace that propane gets into the metal of the tank and will leech back out after you've purged the tank. I've also read that what you smell is just the chemical they add to the gas that remains after you purge it. Which is it?

I took the valves off and filled the tanks with water to run all the remaining gas out, left it overnight to let any gas dissipate and then emptied the tanks back out the next day.

Safe to cut on with the plasma now?

Ian

 

[ericher69]

Check on ehow; safely cut a propane tank

The odorant that is added to LPG is called Mercaptan (also added to NG)

Just to be safe I would also consult an experienced qualified welder from a shop

 

[Egon]

What you smell is Mercapton that is added for oliffactoy sense of the gas.

Gases in tanks can become traped behind scale and also enter into intersituaties of atomic level in the metal. For a tank of your size all should be good having it filled with water. If in doubt fill it with water and heat to boiling. That should do it.




mercaptan

mercaptan (murkăp'tăn) [key]or thiol (thī'ōl) [key], any of a class of organic compounds containing the group -SH bonded to a carbon atom. The volatile low-molecular-weight mercaptans have disagreeable odors. Mercaptans are found in crude petroleum, and methyl mercaptan is produced as a decay product of animal and vegetable matter. They also are produced by certain plants and animals; e.g., allyl mercaptan is released when onions are cut, butanethiol (butyl mercaptan) derivatives are present in skunk secretion, and mercaptans are among the sulfur compounds causing the disagreeable odor of flatus. T-butyl mercaptan blends are often added to the odorless natural gas used for cooking and serve to warn of gas leaks. Mercaptans take part in a wide variety of chemical reactions. Their principal uses are in jet fuels, pharmaceuticals, and livestock-feed additives.

 

[Haywire]

Alright... Didn't make sense to me that the metal would absorb gas in any significant amounts.

Ian

 

[rjmack]

that ehow procedure will certainly do the trick, or...

if you have a brake line extension for your blow down nozzle, turn the tank updside down or valve to the bottom, run the extension to the bottom of the tank, and flush with atmosphere for 5 minutes or so.

i have done this many times, no issues, up to 100 gallon tanks. obviously, the larger tanks take longer to flush.

the mercaptan smell can still linger after you have cut the tank in half.

btw, those tanks are fairly thin... 5/64 zipcut works nicely.

 

[JB4310]

I made a 20 pound propane tank into a portable compressed air tank. Didn't do anything to purge it, except open the valve. Man, the air that came out of there stunk for years, I'm sure it was not at concentrates that could ignite, but you knew it was propane (the smell)

JB

 

[Sutol]

I make the odd wood burner out of old propane bottles.

Before cutting them I leave to stand overnight filled with water.

Mine have been ok to cut with an angle grinder (slim disc) after that.

 

[sandman2234]

I had a 350 pound cylinder that was empty and not needed. I opened the valve one day just to let it completely empty. Months later, I decided to use it for a project, so I removed the valve on the 2" opening at the top, and filled it with water, emptied it, filled it again, while the bottom valve stayed open. When I went to cut into it with a torch, it still popped and sputtered, keeping me on my toes. I have cut acetylene bottles with less problems, but that is another story.
David from jax

 

[Haywire]

I cut the small tank and it all went smoothly. No booms, whoofs, or anything else that would cause cause me to pinch a hole in my undershorts.

What I was really worried about was cutting a straight line around the perimeter of the tank. Found a carousel in my wife's pottery stuff that was just the ticket. Center the tank on the carousel, rig up something at the right height to brace the torch on and turn the tank slowly. There were a couple bobbles that messed the line up, but overall, for the first attempt, not too bad. That tank was a lot thinner than I thought it would be. I figured it would be at least 1/8". Not.

 

[dstig1]

Flipping it on it's side onto a couple rollers like a roller conveyor might be an easier method than the turntable, if you have something like that or can make it. Just roll it in place.

 

[Haywire]

Playing with my cell camera.

Propane Tank on a Turntable - YouTube

 

[crazyal]

I have a couple of the 20lbers with the old valves siting around. I've wanted to turn one into a pressurized blast pot but so far I haven't gotten around to that project.

 

[monckywrench]

They retain some odorant. No problem.

 

[slowzuki]

Propane molecule is pretty big, I wouldn't think it would actually get into the crystal structure of the metal.

 

[yomax4]

I purged the crap out of a 20# to convert it to an Air Tank. Still smells a little after 6 years.

 

[TaC team greene]

I used to weld on gas tankers and all kinds of gas tanks. Yes! every type of gas will absorb into every kind of metal. Soaking it in water is good but gas will come out of pores in the metal when you heat it up. If the mixture gets right it will blow up. You need constant are flow to prevent the fumes from accumulate in the tank. Use an air compressor and blow air in the tank with the hose all the way in the tank. That way the fumes blow out the valve hole and cant accumulat. This is so simple and easy to do safely, i just dont understand why someone wouldn't. :thumbsup:

 

[moored4]

Alot of people that shoe horses use them to make homemade forges out of!

 

[TaC team greene]

I used to cut, weld, and grind on gas tankers every day. Somthing as simple as ventalating the tank when you work on it could be the differnce between life and death. Stay safe.

 

[Johnp33]

I watched a guy trying to cut the top out of a 45 gallon barrel one time he was told to put an air nozzle in it and use an air chisel. He used the torch, It popped and flipped the top. He was a waist of skin but never got hurt.
I agree remove the valve, I like to leave it sit in the sun for a while then vent it continually, while working on it.
I also use propane bottles as air reservoirs, My compressor is about 50 ft from the work areas I have the 30 lb tanks hanging up side down with a drain pipe about 6 inches long hanging down and a manifold with a two couplings in it one large and one small. It gives you that little extra kick , as well as volume