Butane Cannister Shortcomings - Page 3 - ClubTread Community

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post #31 of (permalink) Old 08-03-2010, 02:13 PM
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Quote:
quote:Originally posted by aklinz
[brnteresting threads out there about the so-called "mixed gas blends" sold by various brands. Butane and Propane DO NOT MIX. Period. So a so-called 80/20 Butane/Propane mix is simply 20% Propane on top, with the remaining Butane on the bottom. So running one of these cans on a LPG stove results in the stove first burning pure propane.
That is completely bogus, I'm sorry.
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post #32 of (permalink) Old 08-03-2010, 02:37 PM
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A little reading on the subject...

http://www.bushwalking.org.au/FAQ/FAQ_Mixtures.htm
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post #33 of (permalink) Old 08-03-2010, 07:00 PM
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Lots of good reading here, maybe a weeks worth. Thanks for the info links, Pack Rat & johngenx. So butane and propane become a mixture or a solution? And they burn off at differing rates, depending on temperature? I guess I'm looking for the simple answer here, rather that spend my next weeks evenings reading about Boyle's Law and such heady stuff.

swebster, thanks for the version in layman's terms and simplifying the explanation.

Andrew, Yes I have seen the Brunton adaptor for making a canister top stove into a remote canister stove. Is there any weight savings over an MSR windpro, when the dust settles, regarding the accumulated weight of the adaptor stand?

Peter
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post #34 of (permalink) Old 08-07-2010, 04:38 PM
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I have experimented a little with this, and my Trangia (made by Primus) butane burner has a preheat tube. If you dont want flareups when turning cannister upside down, you ned both redused opening on the valve, and a well preheated stove. I have a fyrestorm SS too, with upside down cannister stand, this has a buildt in restrictor (jet) in the stand, and gets no flareups.

I have tested refilling cannisters too, but only filling up one with whats left in several almoast empty ones. Not filling to more than normal weight (80% full). It works well, but it is usually only the butane-part left. Somtimes the valves not closing perfect, and I have to leave it on the stove.

You may do a lot of theese things if you have the skills, but not if you only believe you have the skills.

I do not refill anymore, to many problems. but I turn the cannister upside down as described.

dsk
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post #35 of (permalink) Old 08-11-2010, 08:31 AM Thread Starter
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DSK: As stated earlier, the boiling point of Propane is -42 C, so all the gas in my cylinder is GAS no matter what the temp. With propane there is no need for pre-heating the cylinder; and no need to invert it. Also note that one of the reasons the Reactor works so well (with all cannisters) is that it has a pressure regulator valve. And yes, I agree with you, I only refill my cylinders to about 80 - 85% by weight. Have had no problems in the last two years of doing this. Regards
Andrew Klinzmann
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post #36 of (permalink) Old 08-11-2010, 09:11 AM
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Quote:
quote:Originally posted by aklinz

DSK: As stated earlier, the boiling point of Propane is -42 C, so all the gas in my cylinder is GAS no matter what the temp. With propane there is no need for pre-heating the cylinder; and no need to invert it. Also note that one of the
Temperature and pressure both affect which phase of material you are dealing with. If you only have gas in your cylinder it isn't going to last too long.
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post #37 of (permalink) Old 08-11-2010, 09:34 AM
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Hey this is a great thread. I personalty have wished for a refill or metered propane/butane tank for my. I hate having to bring two half full tanks in order to insure I will have enough for the trip.


I think it would be a great idea for mec or some company to provide a refillable tank with a meter on it to tell how much cooking time is left on it plus provide a refill station to mec and other stores for people like us to go in and refill our (meant for refill) tank safely.

The white gass products are really appealing to me because they have this technology but they are simply to much hassle and extra weight. I role with the MSR SuperFly Stove and love it I just wish I could have a definate measure of how much gass I have left other then the shake test.
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post #38 of (permalink) Old 08-11-2010, 10:05 AM
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Quote:
quote:Originally posted by MatthewBaldwin

Hey this is a great thread. I personalty have wished for a refill or metered propane/butane tank for my. I hate having to bring two half full tanks in order to insure I will have enough for the trip.


I think it would be a great idea for mec or some company to provide a refillable tank with a meter on it to tell how much cooking time is left on it plus provide a refill station to mec and other stores for people like us to go in and refill our (meant for refill) tank safely.

The white gass products are really appealing to me because they have this technology but they are simply to much hassle and extra weight. I role with the MSR SuperFly Stove and love it I just wish I could have a definate measure of how much gass I have left other then the shake test.
Sounds like refilling a printer toner cartridge!

You can get a definite measure of how much gas you have left by weighing the canister. This isn't convenient in the backcountry though.
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post #39 of (permalink) Old 08-11-2010, 10:11 AM
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You know I never thought of that. I am going to give that a try.

Full canister weight expected burn time.
canister in question weight - Full canister weight = half empty expected burn time.


Yea I am always finding myself bringing the half empty one and the full one and never needing the full one.. One of these days I will. Now I can probably gauge it a bit better thanks to your in site.

I should have thought of that! now I feel like a bafoon.
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post #40 of (permalink) Old 08-11-2010, 10:22 AM
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When you get some empty canisters you can weigh them so you know more exactly how much fuel weight you are dealing with too.
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post #41 of (permalink) Old 08-11-2010, 07:30 PM
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On the canisters there is usually the net weight, or the weight of just the fuel, and the gross weight of both fuel and can. Subtract net from gross and you get the weight of an empty can.

I weigh my used canisters and print on masking tape how much in grams of fuel are left. I usually average about 15 grams of fuel to boil 1200 ml of water. Of course there are factors such the temperature of the water to start with and wind, but I can usually get 7 to 10 days cooking (30 boils) from a large (450 net/ 644 gross) canister. That's one boil of water for breakfast and two for dinner. I don't cook or simmer food in my pot.

Since I started weighing my fuel supply, I am more likely to take a partial filled tank, rather than end up with several "almost empty's" left at home. A large empty canister only weighs 214 grams, so if I take an almost empty one on a trip, with a full back up canister, the extra weight is negligible. Besides, when we divy up the gear, I give the full tank to my partner and I take the almost empty one. That way it "looks" like I'm carrying half.

Peter
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post #42 of (permalink) Old 08-13-2010, 02:44 AM
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As a chemistry teacher, I am somewhat horrified at how little grade 11 chemistry some people know.

To answer a few questions.

Do propane and butane mix? Yes, they are fully miscible in their liquid phases.

Does the propane actually burn off first? Kinda. The amount of vapour that comes off a liquid is dependent on the vapour pressures of its component parts. Since the vapour pressure of propane in a propane/butane mixture is higher than the vapour pressure butane, the vapour coming out of the tank has a higher proportion of propane, causing the butane percentage in the cannister to rise.

This is akin to distilling alcohol, where the alcohol leaves the water in a vapour, allowing it to be condensed.

What happens when I turn my cannister upside down? The butane comes out as a liquid. Liquids can't burn, but they always produce a vapour above them, that can. To truly work well, the stove has to have a method of using its heat to convert the liquid to a vapour at some point. That's why turning the canister upside down is less effective on stoves without a pre heater.

How does the propane exist in the cannister? As a liquid. There are two ways to make a gas turn into a liquid, lowering the temperature or increasing the pressure. How much the pressure has to increase is dependent on the boiling point. Since propane has a lower boiling point, it must be under much higher pressure to become a liquid. That's why pure propane cannisters have thicker walls than prop/but mixes.

Keep in mind, most fuels are just a chain of carbons (with hydrogen). Natural gas has one carbon, propane 3, butane 4 and gasoline theoretically 8. Diesel has 10. White gas (coleman fuel) has 6. Ashphalt has about 16. The more carbons, the more difficult it is (the higher the temp required) to convert it to a gas.

Stoves come in two basic designs, ones that assume the fuel is a gas, and ones that assume the fuel is a liquid that must be heated to make a gas. That's why liquid fuel stoves tend not to be finicky about what they burn.

As for the op's question, what he is doing is dangerous. How dangerous, I don't know. If I was doing it, I would sacrifice a couple canisters on a test. Fill the canister with propane, using your method. Find an open area a long ways from civilization. Place the canister in a bucket of water. Place a digital thermometer in the bucket of water that records maximum temp. Place the bucket on another camping stove and heat. Record the temp that the explosion occurs at. If it doesn't explode under the boiling point of water, it's probably safe.

One problem with propane is that when mixed with air, it forms an explosive mixture at a large gap of percentages. That means that exploding propane tanks tend to ignite, while exploding butane tanks don't. It means that if your canister explodes, it will create a fireball. A big one.
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post #43 of (permalink) Old 08-13-2010, 08:20 AM
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How to HADOUKEN!
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