PS: Even in the very cold, canisters make a fantastic preheater for a liquid fuel stove. I've carried a 4-ounce canister for my Varifuel as a lazy man's preheat and what a treat that's been.

Just attach the canister and run for about 15-30 seconds. this gets the combustion bell glowing cherry red and the preheat tube nice and hot. Then attach the liquid fuel bottle and slowly turn it on -- nothing but gas comes out! Light immediately and you will never have to deal with the "fireball effect" again. Much faster, simpler, and less leaky than carrying a bottle of methyl hydrate.

Hi Brian,

Although I am interested in what happens inside a canister in cold conditions it is not my main area of interest or expertise and I only have very limited resources (time and money which competes with family, work and bushwalking, trout fishing, long distance running/mountain running) I prefer to put most of my spare resources into my main area of interest (stove/pot efficiency, stove burner design and upside down canister stoves). I will do some more cold temperature pressure testing of caniaters with what I have and I will post the results when I have them.

Maybe one of BPL stove editors could do some work on the problems that you have suggested.


Tony

> >You are right: the gauge pressure inside either a Powermax canister or a Kovea 30%propane/70%isobutane canister will drop to zero around -10 F.
> I'm trying to figure out why. Wouldn't the propane in the Powermax canister still vaporize down to -35F/-40F even if the Butane doesn't? (The liquid-phase components would still come out mixed, as desired.)

Yes, the propane does continue to boil at -35 C.
The problem is all about mixtures. If you have half propane and half isobutane, then the final pressure is half of the propane pressure and half of the isobutane pressure. And so on. When you have only 30% propane, its high vapour pressure gets diluted down by the lower VP of the isobutane, such that the total VP falls to 14.7 psi at about -26 C.
Yeah, mumble. Annoying.

More in the next post about liquid feed.

> Basically the upside-down-canister theory is simple and obvious: unless it's -40 out, your propane will still boil and that will push butane into your stove.

If I have published that -40 C figure somewhere, my apologies. Because we are dealing with mixtures the figure should be -26 C for 30% propane / 70% isobutane. Other mixtures are generally not as good.

> So after you've burned most of the fuel in a canister in the cold, I think you've probably burned most of the propane *even if the canister was inverted.*
I am not 100% sure what you mean here, so let me put it this way. The amount of propane needed to pressurise an inverted canister is negligable. So the fuel coming out of the fuel line will be the same as what is in the canister. If you have a 30% propane / 70% isobutane fuel, that is what you will get out of the fuel line, and that is what will be left in the canister. As long as you only use a liquid feed of course.

> I suspect that, due to these two factors, the pressure goes to zero before the air is at the theoretical liquefaction temperature point of propane.
You have to distinguish here between absolute pressure (psia) and gauge pressure (psig). Absolute pressure is ... well, absolute. Gauge pressure is the difference between the absolute pressure and one atmosphere (=14.7 psia). So if you have 14.7 psia inside the canister at sea level, you have pressure in there, but the external pressure is the same so the gauge pressure (differential) will be zero.

Cheers

I threw my collection of 8 full and partially used canisters in the fridge in turn at 4 degrees C (39F), 0 degrees C (32F)and -20 degrees C (-4F) and then measured the pressure in each of the canister. Two of the canisters are 20% propane/80% iso-butane mix and the other six are the other 30% propane/70% iso-butane. All of the used canisters have been used in the normal upright position at some time some have been used in the upside down liquid feed configuration, some have been used in cold temperatures(at least for Australia) and some only in warm temperatures. I have not kept a record of use so I cannot relate the pressures/temperatures to any specific use.

% full by weight for 20% propane/80% iso-butane

100% full 4C/39F: 11psi, 0C/32F: 9psi, -20/-4F C: 0psi

21% full 4C/39F: 11psi, 0C/32F: 3psi, -20C/-4F: 0psi

% full by weight for 30% propane/70% iso-butane

100% full 4C/39F: 26psi, 0C/32F: 20psi, -20C/-4F: 5psi

70.5% full 4C/39F: 11psi, 0C/32F: 8psi, -20C/-4F: 0psi

37% full 4C/39F: 11psi, 0C/32F: 3psi, -20C/-4F: 0psi

35.4% full 4C/39F: 9psi, 0C/32F: 4psi, -20C/-4F: 0psi

17% full 4C/39F: 11psi, 0C/32F: 10psi, -20C/-4F: 0psi

2.8% full 4C/39F: 11psi, 0C/32F: 4psi, -20C/-4F: 0psi

It could be possible by the figures above to say that even in moderate temperatures that the Propane boils off faster than the Iso-butane.

It should also be possible if enough P/T data can be collected to determine how much propane is left in the canister by pressure /temperature reading.

Tony

Edited by tbeasley on 02/14/2007 14:39:45 MST.

Wow; fascinating!

Most of the canisters had very little pressure at *freezing.* So if my canister is at 4-8 PSI at freezing, at what temperature does it hit 0 PSI? -5? -10?

And even if it's -5 out, the canister will quickly cool itself to -10 or -20 through evaporative cooling, and the stove will go out.

I think that Dr. Caffin's advice re: warming the canister is very important below the freezing mark. I think the canister and valve must be kept warm by the flame of the stove to ensure consistent operation.

That said, as long as the canister was kept warm you'd be good to go past -4F/-20C!

Thanks very much for the data and time spent testing!

Hi Brian,

You and others have raised many good questions, doing those simple P/T tests has made me think about more on what is really going on in a canister. I am thinking about doing some more tests. As mentioned in my previous post,I am thinking does the Propane boil off first no matter what is the temperature and what happens in an upside down liquid feed canister.

I am a technician in a university research lab and I have access to a lab that the temperature can be controlled from 4C to 30C but I would like to get access to a lab or cooler that can do -20C to 30C. I am thinking about if I can the tests in a temperature control bath where I can control from -50C up.

I put a 30/70 canister in a freezer at work which measured -24C attached it to my latest liquid feed stove and nothing came out until it warmed up a bit.

Tony

> does the Propane boil off first no matter what is the temperature and what happens in an upside down liquid feed canister.
Try the page on gas mixtures at:
http://www.bushwalking.org.au/FAQ/FAQ_Mixtures.htm
Hopefully they will explain a bit about what is going on.

I have some P/T curves in the FAQ at:
http://www.bushwalking.org.au/FAQ/FAQ_Mixtures.htm#Liqu

Yes, 30% propane / 70% butane does kark at about -20 C.
30% propane / 70% isobutane gets almost to -26 C.

Hi Roger,

Thank you for the link to your excellent Bushwalking.org faq mixtures article. Your Bushwalking.org faq site is a resource that I use all the time.

I compared my data with your p/t graphs. It is nice to know with the 100% full 30 propane/ 70 iso-butane canister that our data matches, but on trying to match the data for the 70% full 30 propane/ 70 iso-butane canister, I am having a bit more trouble. The pressures that I am measuring line up with your figures for pure iso-butane (I will check my pressures again this weekend) if my pressure measurements are correct this would mean that all of the propane has boiled off and no iso-butane has boiled off the canister has not been used in very cold temperatures, but according to your other graph “amount of butane or iso-butane in vapour mixed with propane vs temperature and liquid concentration” this should not have happened.



70% full 30% Propane 70% iso-butane canister pressures.
4C 11 psi/0.75atms
0C 8psi/0.54atms
-20C 0psi(on gauge) I must get a absolute gauge

Tony

Mark-

like I had very much the same problem a few weeks ago with a Coleman Fyrestome ti. I started off with a new smaller canister, jetboil brand. The first time I used it fine. Later that night went to boil snow and couldn't get it started. Warmed the tank then started but dieded out.

I slept with the canister and trypod for it and the next day it started, worked fine and died out again.

When I went home in my apt everything worked fine. I was told by a friend I should have tired using a larger canister because it would create more pressure.

I've read any good reviews of the coleman stove so I'm not sure what I was doing wrong both times I used it camping I kept the canister in my coat for at least 15min before use. I was in a wooded shelter on the trail so wind was even an issue. Temps were around 0 or a little lower. I even went as far as keeping the canister next to the stove to keep it warm?

On the same trip my other friend was using a small jetboil. Both days his lighted and burned. It was not as hot as hot as it should have been but he wasn't pre heating the caninter or using any insulation.

I must say after this happend to me twice I'm a little put off by the Fyrestome.

Any tips or ideas would be helpful.

Joe F.

Hi Tony

> The pressures that I am measuring line up with your figures for pure iso-butane (I will check my pressures again this weekend) if my pressure measurements are correct this would mean that all of the propane has boiled off and no iso-butane has boiled off
Not so. What is very possible is that 95% of the propane has boiled off and 50% of the isobutane has boiled off. This would leave a tank about 1/3 full, but containing mainly isobutane. The amount of fuel left in the tank does not affect the pressure.

Hi Joe

>I started off with a new smaller canister, jetboil brand. The first time I used it fine. Later that night went to boil snow and couldn't get it started. Warmed the tank then started but dieded out.
> I slept with the canister and trypod for it and the next day it started, worked fine and died out again.
> I even went as far as keeping the canister next to the stove to keep it warm?

Now this is different, and strange. You mention the tripod, so I assume you were using the canister upside down as it should be. It seems to me that your problem has to be dirt or gunge somewhere in the system, or a poor connection. I have had problems with the valve on an MSR WindPro when I was using a canister upside down: the valve kept getting blocked. But this should not happen with the Fyrestorm imho.

Check the jet to make sure it is clean. Check the connections too, to make sure they were fully mating. There have been a few cases where the Powermax canister has had trouble mating to the Xtreme stove.
Check that you were screwing the canister onto the tripod fully: if you don't the valve inside the canister won't open properly. Don't be brutal!, but check the connection is fairly tight. There is an O-ring to be compressed inside the connector.

If you can get the stove into the cold again and it seems to be giving problems like this, you could try opening up the valve a full turn briefly (or shutting it right down briefly) to see if this improves things - by dislodging any gunge in the valve. If it does, you may have gunge in the valve.

> I was told by a friend I should have tired using a larger canister because it would create more pressure.
Nope. Doesn't work that way with a liquid feed. Can have some influence with an upright stove in the snow afetr a lot of use.

Lots of good info being posted here. I've had good luck with the Jetboil stove in below freezing temps. Last night and this morning I used mine at 25F - 15F with 10mph wind (hands for windbreak). I heated 8 cups (two at a time) of almost freezing water (taken from frozen over stream) to a rolling boil for three minutes, and my small canister seemed to still be going strong. I wouldn't take it if I was expecting 0 or below, but it works pretty well below freezing.

Rodger thanks for the advice and tips.

I will take it out next week and give it another try. The double valve system even though it's for our safety I found makes flame adjustment harder to use plus wastes fuel.

Joe F

Over the years I've figured out what my problem was with the canister stove I have. Even on a full canister and being in an igloo where it is warm enough for the fuel to vaporize, I found the stove sputtering after 20 minutes or so of burn time.
Well, it turns out that the heat warms up the stove and canister and the metal expands. I found that I could again tighten the stove onto the canister about another 1/16 of a turn and the stove would perk right up.
I can't see this being relevent in a liquid feed stove with the canister that far away from the heat source but...

Hi Ed

> Well, it turns out that the heat warms up the stove and canister and the metal expands. I found that I could again tighten the stove onto the canister about another 1/16 of a turn and the stove would perk right up.
Yeah, I can see that happening with an upright. Great bit of info, thanks.

> I can't see this being relevent in a liquid feed stove with the canister that far away from the heat source but...
Hum - true. Joe's problem may be different - dunno.

>>I can't see this being relevent in a liquid feed stove with
>> the canister that far away from the heat source but...

>Hum - true. Joe's problem may be different - dunno.

Hi Roger,
Maybe Tony has an IR thermometer and could check the line temperatures.
We put up a page on my recent trip to Yellowstone where I used cannisters: http://www.grandshelters.com/yellowstone-2007

Dunno about -40 & the exact percentages, analyses, etc., but I know my buddy's Xtreme stove didn't want to do much of nothing at all in 30 below. It had some gasket and freezing problems, perhaps due to the relatively high humidity of quebec winter?
When crunch time comes, I don't want to be messing around with the theoretical workings of canister stoves, and prefer to get a flame going using white gas.

> I know my buddy's Xtreme stove didn't want to do much of nothing at all in 30 below
Is that Centigrade or Fahrenheit? :-) (Yes, I know there is precious little difference!)

But you are right: the Powermax canister has very little pressure, if any, if it is at -30 C.

> When crunch time comes, I don't want to be messing around with the theoretical workings of canister stoves, and prefer to get a flame going using white gas.
Ah, but white gas is going to be even less useful at that temperature unless you warm it up. OK, the preheat tube will do that once you have got the stove going, but you first have to get it lit and running. How do you prime it at -30 C? Alcohol at -30 C won't light either, nor will a butane lighter.

Yes, I can do it, but YOUR methods will be of interest. :-)

Cheers

Really? White gas won't light at -30?

I have run coleman double-burner stoves at -40, but it was like 20 years ago and I can't remember if they were hard to light.

Could you tell us more?