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View Full Version : O/T 20# Propane Tank



davidh
01-01-2009, 06:14 PM
i have an old 20# propane bottle, empty of course, and the valve opens and closes. . . i want to saw the bottom 25% or so off the tank so i can invert it and make a drain oil holding tank for feeding my garage wood stove.

question is: can i safely saw it open with a portaband band saw ? they do not make sparks as far as i know, and i have one that actually will cut pretty true if im careful.

or...................

should i try to remove the valve assembly again, stick my mig torch in the opening and pull the trigger (without any wire in the gun) and fill it with co/2 while cutting ? ? ? ? then i could use a die grinder with a cutoff wheel in it that does make sparks without any worry at all.

its too much work to get the valve out at this point, too hard to hang on to the tank when its in its original configuration.

input please ?

davidh, "one of the old guys"

winchman
01-01-2009, 06:32 PM
How long has the tank been empty? Has the valve been left open for a while?

We get old propane tanks at the school to make cookers and smokers. We leave them sitting out in the sun for several weeks with the valves open before cutting on them. If we need to work on them sooner, we flush them with water.

You could flush it with compressed air by pressurizing it, and then letting the air out. Each cycle is going to dilute the concentration considerably.

Roger

deltaenterprizes
01-01-2009, 06:37 PM
I like the idea of filling it with CO2.

barts
01-01-2009, 06:37 PM
i have an old 20# propane bottle, empty of course, and the valve opens and closes. . . i want to saw the bottom 25% or so off the tank so i can invert it and make a drain oil holding tank for feeding my garage wood stove.

question is: can i safely saw it open with a portaband band saw ? they do not make sparks as far as i know, and i have one that actually will cut pretty true if im careful.

or...................

should i try to remove the valve assembly again, stick my mig torch in the opening and pull the trigger (without any wire in the gun) and fill it with co/2 while cutting ? ? ? ? then i could use a die grinder with a cutoff wheel in it that does make sparks without any worry at all.

its too much work to get the valve out at this point, too hard to hang on to the tank when its in its original configuration.

input please ?

davidh, "one of the old guys"

The tank valve is 3/4" NPT. You can remove them, but it takes some application of will, as in "You will come out of there!". If you have something big available to strap it to, a 2" ratcheting strap works very well to restraint the tank while removing the valve. I've used a 10' length of 2"x3" steel tubing to good effect, here...

If you want to cut the tank, I'd open the valve outside to make sure the majority of the propane is out, and then repeatedly pressurize he tank w/ compressed air and then let it out. This will insure that there's no propane left to cause problems; the actual flammability limits are fairly tight and it's not like gasoline, where a bit of left-over liquid will cause problems.

- Bart

dhammer
01-01-2009, 07:38 PM
Just be advised that propane is heavier than air so it might not hurt to turn the tank upside down.

I'd flush it with water AND fill it with CO2.

I work for a propane company and change out valves every day..we have a big chain vise bolted to the floor and use a 3' cheater. some valves come out easy and some make me grunt.

You might consider a new tank..on sale for around $25.00..maybe a small portable air tank. I've heard too many horror stories about people getting blown up trying to reuse old propane tanks.

What system are you using to burn used oil? I used an old paint can, length of copper tubing and needle valve..works good.

Steve

clutch
01-01-2009, 07:40 PM
Crank the valve open, let it sit out in open. If in a hurry, wrap your hand around outlet, use an air gun to blow compressed air in and let it out a few times.

You should be good to go.

Clutch

wierdscience
01-01-2009, 07:54 PM
Last tank I cut I filled with water,lit the torch and burned it out.That tank had been open to air for a couple weeks though.

Lu47Dan
01-02-2009, 12:42 AM
Filling the tank with water works really well , I have done several 100lb propane tanks that way and never had a problem with them . One of the projects on hold in my shop ( lack of time and space ) is a dual tower bio-diesel rector skid , one 100lb propane tank for each tower . I had to strap one of them to a tree to get the valve out with an 18" chinee pipe wrench and a 6' cheater bar . But the other one came out with just a 24" Ridgid pipe wrench with the tank strapped down to my welding table . The tanks had been left with the valves open outside for a couple of days , but there was still a small amount of propane in the tanks . The weather was below zero at the time though :eek: . Just be careful and flush the tanks a couple of times . Dan

winchman
01-02-2009, 04:12 AM
I like the paint can idea. Having an open container of used oil close to a stove sounds like a potential hazard, and I've never liked the smell of used oil anyway.

Roger

Your Old Dog
01-02-2009, 09:48 AM
You might consider a new tank..on sale for around $25.00..maybe a small portable air tank. I've heard too many horror stories about people getting blown up trying to reuse old propane tanks.

This is exactly why I like seeing question like this repeated instead of sending people of to the archives. This has come up before and never once has anyone mendioned what Steve suggested and it should be a no brainer but I never thought of it. I have a few tanks I wanted to mess with and never thought of just springing for a new one as they are relatively cheap when compared to the expense if anything goes wrong using an old one :D

Evan
01-02-2009, 10:04 AM
I just leave the dead tanks sitting outside under the trees for about 10 years with the valve open. After that they don't even smell like propane any more.