This arose out of a discussion on another thread (on wood burning stoves of all things), but I thought it was useful enough to justify it's own thread -- especially since gas stove tips wouldn't be something that you'd normally look for in a wood burning thread:

When cooking with canister stoves, there are a number of factors that must be held in tension: Air temperature, fuel temperature, type of gas (butane vs. isobutane and propane), elevation, canister chilling, etc.

I've just written a post where I try to tie these things together in a succinct and hopefully practical fashion. Have a look if you like at: Canisters, Cold, and Altitude: Gas in a Nutshell

HJ

I still vote Super-groovy.

Good stuff Jim! Makes sense to me....

Nice work

I think you should mention the coleman Xtreme fuel bottle and its problem with the feed tube rising above the liquid fuel level unless the bottle is sort of verticle. I use propane butane mix in my coleman and as you said - in a liquified feed like this - the fuel does not first "boil off" inside the canister so the ratio of fuels in the blend does not change as the bottle is consumed. Pushing the fuel bottle into the snow both keeps the fuel warm, and the stove in place. For using those other remote feed stoves like you showed - I would cover the fuel bottle with snow - it will keep the fuel bottle warmer than exposing it to the air and with a boiling point of -40 the propane will get plenty of heat from snow.

Also you pointed out that the outside air pressure matters a lot - the boiling points of these gasses depends upon pressure and are not the same at altitude as at sea level.

Another thing, there is no "open space filled with boiled gas" above the fuel in these liquid feeds stoves, because the liquid fuel flows out of the bottom. In a traditional cannister stove, as a fuel molecule leaves the surface of the fuel and enters this chamber, it will bounce off the walls many times before it finds its way out the exit hole. As the fuel is consumed and the size of this chamber increases, the path to the exit hole becomes longer, the trip takes longer, and effectively lowers the pressure of the gasified fuel leaving the bottle because its harder for it to get out.
Jim

Hi, Jim,

I own or have owned at least a dozen different PowerMax stoves (Xtreme, Xpert, and Xpedition). I've never had the type of problem that you describe either with the 170g canister or 300g canister. Not sure what to say there, but I always have had good success with them in normal side-laying mode.

Well, yes and no. If you're in a really cold area, that snow could be really really cold. Yes, snow can have some insulative properties, but I'd feel more comfortable keeping the canister with me inside my jacket and then putting it into a roll of closed cell foam rather than using snow. If the canister is already at ambient temperatures or there's reason to believe that the snow is warmer than the canister, then yes packing snow around the canister might be helpful.

Exactly. Canister pressure is dependent on boiling point; boiling pot is determined by the air pressure; air pressure varies with the elevation.

HJ

Jim and Jim, I have a Coleman and although I only used it a few times, I never had trouble with the pickup tube. I used it on snow, but not directly-it was on a piece of blue pad, temps around 20F.

Thanks, Tom.

I haven't heard of this problem before. I wonder if Jim got a bad canister?

Jim, if you shake your canister does it "klunk?" There should be a weighted dip tube in there that should "klunk" against the side walls when you shake the canister.

HJ

The open space is on the top of the tank and requires boiling to allow liquid to flow out. The canister whether right side up or upside down is constant volume. In order to pull fuel out that volume has to be replaced with something. That something is boiled fuel. Since liquid fuel is pulled out in inverted operation, the amount of required boiling is much less



Boiling point inside a canister is is not determined by air pressure. Boiling point inside the canister is determined by liquid temperature. However, in order to get fuel to flow out of the canister, the canister pressure has to exceed the atmospheric pressure. That is why canister stoves perform better at elevation. Not because atmospheric pressure changes the boiling point of the fuel, but because lower atmospheric pressure allows you to have positive fuel flow at a lower tank pressure.


...
ok, I've completed my scientific fact checks for the day...

BZH
Go back and read the line that says "effectively lowers gas pressure" because its harder for the fuel moelcule to escape due to brownian motion. The actual vapor pressure etc if the fuel is not what we're talking about, its the time it take for the fuel to escape. (it doesn't count till it reaches the burner)

As the fuel is consumed the "void" Above the fuel) (this void is not constant volume as you state in your scientific fact checks) and above the liquified fuel this void does increase until the entire inside of the cannister is void. While the temp inside may not change and the Vapor Pressure is set by temp, we are talking about a "system" - fuel in a bottle in an environment, not about fuel evaporating openly.

There is an internal pressure set by the temperature of the fuel, and external pressure that it flows to and the friction in between. A longer path to the exit of the bottle = greater effective friction (impedance).

About the cannister. I have twice had failures of these cannisters when horizontal. Trouble is that a piece of metal pipe that is supposed to drop to the bottom has a short piece of plastic line in it so that it can drop. If this plastic freezes it can prevent the pipe from dropping. If you cut apart an empty cylinder you will see why. Maybe this was when they were new and they used diffeent plastic tube? Anyway it ran like it was on its last breath when the bottle was full. Its because it was exhaling only boiled off gas not a liquid feed. Shoving the bottle vertically into the snow solved the problem both times. I hope the problem is no more.
Jim

Which came first, the chicken or the egg?

My understanding is a little different than yours, but you are absolutely correct that the bottom line is the difference between the pressure in the canister vs. the outside pressure. The pressure in the canister must be greater than the outside pressure in order for gas to flow. Reduce the outside pressure, more gas will flow.

HJ

Interesting. Haven't heard of that happening, but I suppose it is possible at really low temps. How cold was it when you were out? Must have been really freaking cold!

Maybe the work around is to set the canister down in the position you want to use it while the canister is still warm. Then, if something does freeze up, no harm done.

HJ

We can argue about this if you want Jim. I love to talk thermal/fluid effects and thermodynamics. I am impressed you brought up Brownian motion however it doesn't really play a role. Fluid leaving a tank is a convective process dominated by the momentum equation. Brownian motion has to do with diffusive effects.

Calling the open space in the container a "void" is most certainly incorrect. A void suggests a vacuum. That space is most certainly filled with fuel vapor. The term we use in the rocketry community is "ullage". I never stated the "void", or more correctly the ullage, was a constant volume. I stated the canister was a constant volume. That volume is made up of liquid and ullage.

I am not sure what your point is about "system" effects and that temperature inside may not change. Evaporating liquid to replace the increased ullage volume due to draining liquid fluid consumes quite a bit of energy. That energy comes out of the liquid which drops its temperature. Lowering the liquid temperature drops the vapor pressure and therefore tank pressure. If you want to keep the tank pressure up you have to drive heat into the tank. Hikin Jim's post is all about effective methods to do that.

I completely agree with your third paragraph... indeed I think it is pretty much exactly what I said.

Given that the Coleman canisters and stoves are no longer being made, I guess it's a moot point.

True, but a standard canister when used upside down does the same thing.

I frequently run my Windpro with the canister inverted in cold weather for that very reason. It's not as good as a Coleman Xtreme, but it's the next best thing.

Don't throw out your old Coleman Xtreme or its canisters! I'm working on a refilling rig right now. The Coleman Xtreme is the best production cold weather gas stove out there, period.

HJ

Still got it and a couple of canisters. Coleman must still have all the equipment to make them unless they sold all the tools to the Chinese, which they may have done.

Tom, I've come up with a number of Powermax canisters for my Xtreme, just need to get out and use it now and HJ sent along a few when I picked up one of his stoves. I even have the adapter, which if I had known I could get the Powermax canisters, I would have passed on it. I've been using some of my other stoves this winter. Old X-GK, 41, 96, 11 Explorer Giga Power GS100 etc.
Duane

Those canisters are actually fairly generic. Go down to your local Rite Aid or CVS, and you'll see lots of pressurized aluminum canisters with exactly the same dimensions. Coleman basically took an "off the shelf" technology and used it for their Powermax canisters. The pick up tube inside is different and possibly unique though.

HJ

The whole subject is nearly a red herring.

Back in the 1980s, given available fuel in U.S., one had various troubles in cool-going on cold weather with French-made canister stove "Bluet," which was the standard of its kind at the time.

It is no longer a issune for canister stoves, at least down to around zero F. They've changed the fuel mix.

True, with any stove in bitter weather, warming the tank & cooking on a little insulation is a good idea. But it needn't be complicated business.

Bluet was strictly isobutane, it's boiling point is 10.8 F at standard pressure.

The new mixtures are not standard and may contain n-butane (31.1), propane (-43.8) or isobutane.


While these new mixtures are slightly better than pure Iso, they still suffer from the cold. There is significant drop off in gas pressure released as the temperature gets closer to the boiling point. They are NOT fine down to zero F. In fact below 32F one can already notice the effect of the ambient air temperature on the performance of the stove.
As the canisters release their gas ( as long as temp is above the boiling point) the pressure drops and this cools the liquid even more) potentially causing the canister's liquid to stop vaporizing.
This isn't to say one can't use them at zero F, but one must keep the canisters warm by sleeping with them, placing them in water, or some other technique. Simply, the claim that they are no longer an issue down to zero F, is misleading at best.

+1. Canister stoves suffer decreased inefficiency well before 0F and do not do well in subfreezing temps. They'll work, but not the same as in higher temps. Wouldn't rely on them in winter.

Lori is absolutely correct, and this situation is not exactly news. For years, if going into cold conditions where heat and cooking were critical, rational folks have picked up the weight of liquid fueled paraphernalia, along with a generous supply of white gas, and staggered out the door.

I remember prepping for a SAR mission, where we were headed out for what was certain to be an all night hike in heavy deep snow - one of my team members reviewed my full cook kit and Primus 71L, threw his own Svea kit in his pack, commenting that duplication of stoves made a lot of sense where we were heading. He was right, as it turned out. Sometimes it doesn't pay to quibble over grams, or even pounds.

Bah, I should have said "decreased efficiency" or "increased inefficiency."

Not enough coffee today, I guess. At least you got what I was trying to say.

http://vimeo.com/4453969

Gasoline-type stoves are more dangerous inside a tent, which is the only feasible place to cook in bitter weather.

Right: warm the canister stove in sleeping bag for a few minutes and maybe place it on some insulation. Warm Bic lighter similarly before flicking flint.

Not hard.

Perhaps you need to spend some time with experienced backpackers before you make unfounded assumptions.

Folks have been using white gas (I'm assuming that is what you mean, but tho there are stoves that can use gasoline, that is not what the fuel is generally) stoves for a long, long time, in and out of tents - they are far more efficient for melting snow than canisters and a better bet for the dedicated winter mountaineer. I don't like them because they are heavy and fiddly and rather ridiculously overkill for most of my needs, but if I continue with winter SAR I will likely end up with one. And I will cook inside my (floorless) shelter when conditions warrant.

Some of the canister stoves are also dangerous inside tents - the Pocket Rocket puts out a good bit of carbon monoxide, and the MSR Reactor put out such high levels of it that MSR redesigned it as a result of the review backpackinglight.com did on it. And the top of the canister mount models are too tippy for me to want it anywhere near anything I don't want scalded or burnt.

So now "no issues" have become "not hard". I am not sure you have used any canister stove even close to zero F.

The warming of a canister is necessary well before one reaches 0F. That isn't even bitter cold either. close to zero F, it certainly is "hard" to get it lit and keep it going. I have had to boil water for a number of people whose canister stoves failed them in the single digits. Even after trying all those tricks they and you read about on the internet.

When you get to negative teens fahrenheit, then you are entering the bitter cold range. At that point your canister is pretty useless even if you slept with it. You might get lucky and get it to light, but very quickly the air temp and the decreasing pressure will end it.