View Full Version : cutting a propane tank

john pen
06-01-2004, 08:31 PM
I remember a post a little while back where we talked about cutting an old propane tank..I did a search but couldn't find anything. I thought about filling it with water to purge it before attacking it with the cutting wheel. Any ideas or direction to the thread where this was already discussed.

06-01-2004, 09:39 PM
I've done it to two propane tanks now. Took a long time to get the valves off, but I eventually got them. Then I just filled them with water(which was overkill, purgeing them with air for a few minutes would have been fine. Then I took an OA torch them and turned em' into dip tanks for cooling my metal.

06-01-2004, 10:43 PM
I'm a little curious myself about this.

I've heard of the water idea before, but one that blows my mind, in its own way makes sense is to put a hose on a tail pipe of a car or truck down into the tank and then cut it. I heard this from a handful of old timers.

One guy told me he would do this with gas tanks. I dunno, but I see BOOM!

They all say the carbon monoxide is supposed to kill the fumes.

I would like to know if anyone has heard of this or done.

Mike W
06-02-2004, 04:28 AM
I once saw a guy fill a toy baloon with propane and wave a small propane torch (on a 10 foot pole) at it. No bang, 3 more attempts, not impressive.

I made a sand blaster out of a propane tank. I had to cut an opening in the top and the bottom. I forgot the safety steps I took or I would repeat them. I do remember welding legs on one with 6013. One of the welds caused a crack in the tank. I never did figure out why it did, any ideas. That is the one and only time I had a weld crack. :o

John C
06-02-2004, 07:40 AM
I've heard about the exhaust pipe trick, but my opinion on that is you have to use the exhaust from an engine that burns fuel 100% . I don't know of one that will do it.
The way I have seen & done it is fill the tank full of water & let it set for a day. Before I take a torch to it I will stuff some paper in one the bong holes & light it on fire. If it don't blow then I assume that it is safe enough for someone to cut.

06-02-2004, 09:27 AM
I've heard of the gas tank/monoxide thing before. The 'theory' is that monoxide displaces the oxygen so the gas can't burn. But when let the gas out of a propane tank, all that might be left is some standing airiated gas which is quite explosive unless you push the rest of it out with something like water or air.

06-02-2004, 03:35 PM
the idea behind exhaust in the tank is to produce an atmosphere with less than 16% oxygen (think it is around 16% that is needed for combustion)......just to give you an idea ....you need more than 18.5% to stay alive ....at 22% you start to get goofy like your drunk...and yes it does work i use it all the time useing the exhaust off my pipeliner....but be warned you better make sure it is full of exhaust and no oxygen pockets in it ....you can have all the fuel in the world but without oxygen it won't burn

06-18-2004, 11:23 AM
I've previously turned 100# propane tanks into air compresors, complete with cutting and welding in a bing in the bottom for a drain, and welding a set of heavy angle irons to the top to hold the pump and motor. When I lit the torch, the entire shop cleared - but nothing happened at all. I will add that some amount of oil/water mist had been added into the tank at some time by others using it as air storage in its stock form before I did any further modifications. It still smelled like propane (that chemical seems to stick right to the metal) but I couldn't get it to flame a match when I pressurized it and tested it first (held a match to a tube far away from the tank to see if the contents were flammable.

I say - make it inert and use the tanks...

06-18-2004, 03:02 PM
You can always purge the tank using c02, the shielding gas type. i have done this on several occasions and it worked fine.:blob2: :http://www.weldingweb.com/newreply.php?s=&action=newreply&threadid=1501#

06-18-2004, 11:01 PM
If you've got em', post some pics. That sounds like an interesting project, making an aircompressor setup out of old tanks.

06-19-2004, 04:53 PM
Propane is a very safe gas as fuel gases go. The mixture has to be between 2.1 to 9.5 to be flammable. Purging a propane tank with engine exhaust gasses would be effective. Keep in mind that driving exhaust through the tank would heat it adding to the effectiveness of the purge.
I fill the things with water and then cut them with a cutting disc. The water leaks out when I break though. I figure the remaining water improves my odds.
The "proper " way of course is steaming out and then vapour check. One of my friends who is a body man told me that he worked in a shop where the boss would remove gas tanks from cars then set them on the floor and lower the car hoist gently down on top. The idiot would wave his acetlyene torch past the mouth of the filler neck. After the explosion he woud proceed to braze up the original leak and any burst seams on the edge. Needless to say my friend vacated the shop every time this guy tried to get his Darwin award.
By the way ... I cut the tanks in half and make planters out of them.

06-19-2004, 06:29 PM
Sorry, that was about 6 years before digital cameras came out and the compressor has since been sold (and I miss it! - it worked much better than the silly oiless one I have now).

The whole idea was really pretty simple. I added a couple of legs on the bottom for stability (ran it upright like the vertical ones), added a bung in the bottom to drain water, tapped the threads on the top to take standard pipe thread, and welded on a set of angle irons (so that the top was flat). I carved out the bottoms of the angles so that they matched the contours of the tank, and just welded them on with a stick welder. I think I used 3" x .250 angle irons about 24" long and stuck a pair on the top.

Then I drilled the irons to fit a 1 HP industrial (read that HEAVY) motor and I used a York air compressor head off an old Ford. I added a regulator, and an electical shut off valve and a safety pop off, just in case. Later, I doubled the Yorks so they made more air (I was turning them FAST - motor was 3450 RPM and I was about 2:1 on pulley size (I ran the stock pully on the York and "locked it" by adding a couple of spot welds between the pully and the clutch). That littel machine made enough air to keep up with a die grinder, which isnt' too bad for having less than $30.00 in the entire project.