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Oxygen tank for propane ?

Posted by Arch-Tone 
Oxygen tank for propane ?
July 05, 2018 01:54PM
I’m still working on a gasoline burner system for the mini chopper and experimenting with a few ideas, but for the sake of testing the new natural circulation boiler I will continue to use propane for the convenience. The main problem with propane, at least for this project, has been the ability to store enough of it safely for the higher volume weed burner torch. The three 14 oz bottles I’m using now will “work” but it runs out too quickly.

My question is this: I have both a 20lb and a 40lb oxygen tank (the type used for oxyacetylene torches) that are empty. They are rated for over 2,000 psi working pressure and use a 3/4” female NPT fitting for the valve assembly....the same size used by a standard 20lb propane tank. I took an empty propane tank and removed the valve assembly from it. It fits perfectly on both the oxygen bottles. The oxygen bottles fit perfectly on the bike where the old boiler was, behind the seat. Can an oxygen bottle be used to safely store propane, using the valve assembly from a propane tank? The valve has a built in bleeder, safety relief valve, float shut off, etc. It could be refilled with a standard 20lb propane bottle....upside down...using a readily available adapter for that purpose.

My thinking is....the more heavy duty oxygen tank would hold plenty of propane, especially if I use the bigger 40lb one. It’s thicker walls would help prevent accidental punctures or other damage. It’s over 2000 psi pressure rating would contain any over pressurization, I would imagine, from heat, etc. The only downside I see is the added weight from the heavier tank, or possibly an issue with the O2 tank alloys not getting along with LPG. I’m not too keen on the idea of having a possible bomb 8 inches away from where I’m seated, especially on such a small vehicle with an open flame, so any advice on this would be appreciated.


Re: Oxygen tank for propane ?
July 05, 2018 02:50PM
Oxygen tanks will be made from either aluminum or stainless steel, both materials are fine for propane storage. The oxygen tank will be overkill pressure wise. The relief vale will vent the propane around 300psi / 130f. The only concern is making absolutely sure every last bit of oxygen is out of the tank before converting to propane.

Liquid oxygen is about twice as dense as liquid propane, so your 20 pound oxygen tank will be a 10 pound propane tank.

You can buy 10 pound aluminum propane tanks, but they're kinda expensive.
Re: Oxygen tank for propane ?
July 05, 2018 03:40PM

These tanks in particular are not stainless or aluminum...I know this because I have used them as pressure vessels in the past for steam generators and the presence of water causes surface rust to form and if water sat in them for any period of time, it would end up looking like coffee...not to mention I welded fittings on them. I was told they are made of a special heat treated steel alloy. You are probably thinking of the breathable oxygen tanks that people with lung issues use. Those are usually aluminium or stainless.

I already figured that a “40lb” oxygen tank that relies on high compression to store it would not give me the equivalent of a 40lb propane tank. 10lbs of propane would be sufficient, considering that a 20lb tank lasts more than 2 hours with the torch at full blast, as long as it’s warmer outside and the tank / valve / hoses don’t freeze closed.

I looked into the different size propane tanks, at least the ones Amazon offers. Your right....they are expensive, and they seemed to be too wide or too long for where I need to install it. But you gave me an idea...perhaps there is a breathable type, 40lb aluminum oxygen tank with similar dimensions as the steel, welding type one. Corrosion would not be a factor and it would certainly be much lower in weight....hmmmm....something to look into...might be worth the $ if it’s safe to convert to propane and fits on the bike.

Re: Oxygen tank for propane ?
July 05, 2018 08:54PM
I don't see any issue using the the oxygen cylinder for propane. As Zimirken points out above, using the valve and associated PRV from a propane tank, is going to limit the pressure to about 300 psi, way below the pressure rating of the oxygen cylinder. I'm pretty sure, oxygen cylinders are made from Cromoly and Propane cylinders are made from mild steel. Pounds of Propane is referring to the weight of the liquid, Propane weighs 4.24 pounds per gallon. So a 20 pound tank holds 4.7 gallons and represents 80% of cylinder volume at ambient temperature.

Oxygen is the weight of the gas - 1 pound equals 12 cu/ft., oxygen tanks like the one shown are gas only at high pressure.

The biggest issue you'd have using that is trying to get it refilled, any refill station that is aware of the rules will not fill it. You can fill it yourself though from a 20 pound cylinder, don't fill it over 80% of volume.

I have a Propane tank you can have, I think it's a 10 pounder, about as tall as a 20 pounder but skinny, I think its the same size as Tony has on his Deloura - if you've seen it. I can send a pic if you're interested.

Added: Yes as mentioned above make sure you purge that tank well before adding Propane, talk about a bomb, that would make a big boom. There are some considerations like how would the temperature extremes effect Cromoly, could be a strange thing where Cromoly becomes brittle at freezing temperatures, you might want to look into that.

Edited 1 time(s). Last edit at 07/05/2018 08:58PM by IronChief.
Re: Oxygen tank for propane ?
July 08, 2018 09:30PM

You may also use a CO2 tank, you've got to consider its a liquid tank, the problem I see is that no one will fill it.

I have a 5lb aluminum tank in my kegerator and its a decent size, you must consider that its full of liquid CO2 (and not a high pressure, like propane)

Look into CO2 tanks, I bet you will get the right fit. they are directly inter changeably as far as rating with propane.
Re: Oxygen tank for propane ?
July 09, 2018 01:22PM
Quote: "consider that its full of liquid CO2 (and not a high pressure, like propane)"

CO2 is about four times higher pressure.

Fellas, most of these gases being discussed here are stored in liquid form, the difference is, they boil at different temperatures and will be at different pressures at the same temperature.

Oxygen, the way the layfolk purchase it is in gaseous form, compressed gas, not a liquid.

Most of these cylinders can work for Propane, the best thing to do if you're insistent on running propane is find a DOT certified Propane tank that fits your plans. The better thing to do is devise some sort of a liquid fuel vaporizing burner. Something that is not going to be popping off and causing a hazardous situation if it overheats.

Re: Oxygen tank for propane ?
July 09, 2018 10:10PM
Quote: "consider that its full of liquid CO2 (and not a high pressure, like propane)"

This is my mistake I was referring CNG.
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