Gas canister use in cold

[Mark Ferwerda]

Here in Maryland we don't get real cold temperatures but this morning was 7 degrees when I got up. I had been wanting to test Roger's Caffin's idea about using a Brunton Canister Stove Adaptor (see http://www.backpackinglight.com/cgi-bin/backpackinglight/myog_winter_stove_summer_upright_stove_brunton_stnd.html) and this seemed like a good time to do it. I used a piece of copper (cut, flatened and shaped from regular copper 1/2" pipe as the feedback conductor instead of brass. I let it and the fuel canister stand outside over night. This morning I lit and and sure enough, after @ 2 minutes, it was burning blue. I was using a small (110g) SnowPeak fuel canister that was nearly empty but it was working well. Interestingly enough, I had also put out an MSR Windpro stove outside with a large MSR fuel canister (about half full). I lit this stove with the canister inverted. However the flame was just simmering despite the fact that the flame adjustment knob was set to fully opened. I turned the knob several times to make sure it was not clogged up but no change. I then switched the MSR fuel canister w/ the SnowPeak canister and then the performance of the WindPro was much better. I then bought all the stoves in and after things were warm, I re-attached the MSR canister and it worked just fine. So here is my question — In really cold weather, does the size of the canister make a difference? Or is it the fuel mixture that does it? I can't find what mixture SnowPeak uses. I do know that MSR uses 80% isobutane and 20% propane. Any thoughts? Thanks!
Mark

[cary bertoncini]

i seem to remember a few years back reading that the snowpeak mixture was most ideal for altitude/cold

[cary bertoncini]

http://zenstoves.net/Canister.htm#CanisterTypes

snowpeak: 65% Isobutane / 35% propane

MSR: 80% Isobutane / 20% propane

the higher propane % = burns better in colder temps

[Michael Martin]

A couple of notes:

1) bear in mind that n-butane and iso-butane have different boiling points. I don't recall which variety Snowpeak and MSR use, but a lot of n-butane in the mix would be bad for cold weather.

2) The composition of gases left in a partially-used canister depends upon the temperatures at which the can was previously used. If your MSR can was used previously (upright) at cold temps, it's possible that much of the propane is gone, leaving insufficient vapor pressure to drive the fuel to the stove. Note that if a can is used inverted throughout the life of the can, the gas mix will not change much.

[Brad Groves]

I made some calls recently to determine fuel blends; Snowpeak told me that their mix is 85% isobutane: 15% propane…

I suspect that when used previously, operating temps could have affected vapor pressures so that resultant mix was less in one fuel or the other, but I dunno. That'd be a question for Roger.

[Tony Beasley]

Rogers FAQ site http://www.bushwalking.org.au/FAQ/FAQ_Mixtures.htm has Pressure/temperature graphs for different Propane/Butane fuel mixes. If you can measure pressure and temperature from Rogers graphs it is possible to work out what mixture is in a canister.

Coleman max is supposed to have a 60% Butane/40%Propane mix in them, I have had no problems using Max fuel at around 0F (-18C)

Tony

[Roger Caffin]

Hi Mark

Good to see the Brunton worked. Thanks for feedback. Btw – copper is MUCH better than brass, and I don't (any more) recommend using brass for the fin.

Now, the MSR canister. That gas mix should work OK in the cold if it still has enough propane in it. If it had been used upright a lot in the cold (as Mike M suggested) it might however been reduced to mainly isobutane, with little propane left. Isobutane boils at -12 C (10.5 F), so if you were running it at 7 F it was a bit cold. With only a little propane left in the canister, the pressure would have been rather low, and this could have meant the stove would not rev up much.

The first solution to this problem is to pour cold water (NOT hot) over the MSR canister. Fill up the concave base with cold water. This will put heat energy at >32 F into the canister, warming it up from 7 F. Yeah – sounds strange, but the physics works.

Letting the heat from the stove radiate onto the canister also helps. Do NOT let the canister get so hot you can't touch it – EVER! But 'luke-warm' is fine: they are rated to withstand 50 C (122 F) continuous.

There is one other thing to check, and that is that you had screwed the connector onto the canister enough. If you hadn't done this the Lindal valve in the canister might not have been opened enough. This sort of problem can happen when the rubber O-ring in the connector gets very cold. The problem disappears when you take the stove back inside and it warms up – which can make for some very puzzled people.

On the whole, I suspect that the problem was that the half-empty MSR canister had little propane left in it. This is a well-known problem. Start with a full canister and always use it inverted.

> does the size of the canister make a difference
Not really. It's the fuel mixture that matters.

Cheers

[Mark Ferwerda]

Thanks to all who answered and a few comments. I know the SnowPeak canister had always been used inverted but I don't remember if the larger MSR one had (I believe it had been used both ways…) After the stoves were lit and going for a few minutes, I did put some cold water into the bowl of the canisters to see if that made a difference but I could not discern any visible differences in the output. Thanks again for all the replies. It is amazing the amount of activity that goes on these forums!
Mark

[Michael Ray]

Roger Caffin wrote:
> On the whole, I suspect that the problem was that the half-empty MSR canister had little propane left in it. This is a well-known problem. Start with a full canister and always use it inverted.

I take it that most people don't do always invert their canisters but SHOULD if they plan to also use them in colder temps so the original gas mixture is retained?

I believe I read elsewhere here you should start upright and then invert after 20-30 seconds or run it on low for 20-30 seconds if you start with it inverted to prevent flareups. Is that correct?

I'm looking for a stove suitable for Scouts that will work simply and reliably in all temps above 0 F (-18 C) with 2-6 L pots. It seems the MSR Windpro would be the front runner in that regard.

[Steven Evans]

Hi Michael,
At 0*F you are going to see MAJOR performance issues with an upright canister stove, so yes, it is best to run it inverted. Start it upright on low and light the stove…then slowly invert it (just as you stated). Too fast and you may get a big flame. Never light while inverted.

The windpro is a great winter stove, I used one for nearly 1 1/2 years before picking up the coleman extreme. Even at 0*F, the inverted windpro will show some performance decrease so if you want true efficiency in the winter, you should attempt to keep your canister somewhat warm aswell as invert it. You can search/read a bunch of Roger's posts on winter canister use – he knows his stuff.

I heat my canister inside my jacket and then throw a CCF cozy around it before use. There are a bunch of techniques you can do. As the temperature gets warmer (ie. higher then 0*F, you will see the stove performing better and better, at which point the additional canister warming techniques may not be required. Anything below 0*F and you will have to work to get that windpro to melt lots of snow. I have literally spent hours melting snow for a team of 3 in the evenings…it can get frustrating! :)

Summary:
The windpro is a great stove, however, just inverting the canister "at your lowest anticipated temp" (0*F) will not give you the performance required to efficiently melt liters of snow.

Hope that helps!

[Michael Ray]

Steve,
I'd always invert so the propane % would remain as close to original as possible. Our time near 0 F will be very small compared to you in the Great White North.

I'd considered the Xtreme (one of Roger's gold standards) also as you can still get them at least used, but how much longer will they support the PowerMax cells once the stock of everything that uses them is gone? 5 or 10 years from now? At that point the Xtreme shouldn't have any advantage over the WindPro as it would have to use the same cartridges with lower propane % as the WindPro but with an extra adapter.

I fail to understand how Coleman can use higher propane % in PowerMax with an apparently lighter can, which you'd think would burst sooner, than those with 30 % or less. There's clearly a market for 40% propane so why isn't it offered in traditional canisters?

[Stuart R]

Mike:
"The composition of gases left in a partially-used canister depends upon the temperatures at which the can was previously used."

No it doesn't (at least not significantly). See this post.

"If your MSR can was used previously (upright) at cold temps, it's possible that much of the propane is gone, leaving insufficient vapor pressure to drive the fuel to the stove."

This will be true regardless of the temperature at which it was previously used. See above post.

"Note that if a can is used inverted throughout the life of the can, the gas mix will not change much."

This much is true.

[Roger Caffin]

Hi Michael

Sorry – missed your questions – away walking.

> I take it that most people don't do always invert their canisters but SHOULD if
> they plan to also use them in colder temps so the original gas mixture is retained?
Definitely yes.

> I believe I read elsewhere here you should start upright and then invert after
> 20-30 seconds or run it on low for 20-30 seconds if you start with it inverted to
> prevent flareups. Is that correct?
With most stoves this is a very good idea too.

In some cases you can start the stove on low with the canister already inverted. With the Coleman stoves running on Powermax canisters and the Fyrestorm stove you always do it this way.

> a stove suitable for Scouts that will work simply and reliably in all temps
> above 0 F (-18 C) with 2-6 L pots. It seems the MSR Windpro would be the
> front runner in that regard.
I would recommend the Coleman Fyrestorm myself, but the Windpro would do.

Cheers

[Roger Caffin]

> how much longer will they support the PowerMax cells once the stock of everything
> that uses them is gone? 5 or 10 years from now?

Dunno. I'll worry about that when it happens. At present they are committed to supplying.

> I fail to understand how Coleman can use higher propane % in PowerMax with an apparently
> lighter can, which you'd think would burst sooner, than those with 30 % or less.
> There's clearly a market for 40% propane so why isn't it offered in traditional canisters?
Yeah, that's a bit tricky, but it does work out. You have to look at the pressure/temperature curves to see why. I think they are in the articles.

But also note that the one-piece aluminium Powermax canisters are actually stronger than the 2-piece steel ones. The reason for this is the much smaller diameter of the Powermax canister and the way the Powermax base is made.

Cheers

[Roger Caffin]

> "The composition of gases left in a partially-used canister depends upon
> the temperatures at which the can was previously used."
> No it doesn't (at least not significantly).

I am going to disagree here with the 'not significantly' bit, for two reasons. If you do the thermodynamic calculations you can see the effect happening, as shown in this graph (thanks Don):

But equally, many winter climbers and walkers know from sad experience that you can end up with a canister still 1/3rd full of butane with negligible propane left – and no gas coming out. It happens in the cold.

> "If your MSR can was used previously (upright) at cold temps, it's possible
> that much of the propane is gone, leaving insufficient vapor pressure to drive
> the fuel to the stove."
> This will be true regardless of the temperature at which it was previously used.
I'd like to clarify this as I disagree with the word 'regardless'.
If you use an upright in the cold this will happen. But if you keep the canister 'warm' there will be enough propane left to keep the stove running right to the end. Mind you, even if the percentage of propane remaining does fall significantly, the butane in a 'warm' canister will still be boiling when more than a few degrees above 0 C.
Hey – most of us have no trouble completely emptying a canister, so it obviously works.

'warm': say 10 – 20 C. Definitely NOT above 30 C.

Cheers

[Stuart R]

Hi Roger
I have done the calculations and I don't disagree with your graph. Here's a graph of gas pressure at three different temperatures starting with 30% propane, 70% butane.

At any point you can warm the canister and jump to the line above, or cool the canister and drop to the line below. The propane provides the bulk of the pressure at all temperatures, providing there is sufficient propane left. This graph shows the % propane when the canister is used at 10C and at -10C. There is a difference, but it's not very much.

[Roger Caffin]

Hi Rob

Interesting, and thanks. I assume you are holding the gas temperature constant in this? That can be difficult in itself – I have created frost on the odd canister or two in the cold as it cooled down. :-)

How about a recalc at 20 C? I am thinking of summer time in America or Australia.

Any objection if I save the graphs (with acknowledgement of course)?
Actually, what about the code used? Would you be willing to share that? Again, with acknowledgement of course.

Cheers
Roger
[email protected]

[Paul McLaughlin]

Roger – what factors make you prefer the Fyrestorm to the windpro?

[Roger Caffin]

Hi Paul

I have used both. I found the WindPro accumulated some sort of gunge at the valve when the canister was inverted. It tended to block up the gas flow every now and then. I don't know what it was – it may have been part of the odorant used in THAT canister. I didn't have this problem with the Fyrestorm. Otherwise – both are fine.

This pic is taken from the FAQ at http://www.bushwalking.org.au/FAQ/

The white stuff (F) at the tip is the gunge.

Cheers

[Paul McLaughlin]

Thanks, Roger. Was that an experience with just one canister? Your emphasis on "THAT canister makes me wonder if that's the case.

[Stuart R]

Hi Roger
Sure, here's a graph with 20C (still 30/70 propane/butane)

The graph I found most interesting was the boiling point of the gas mixture as the gas is used. Here I analysed three different mixtures: 30/70 Propane/n-Butane, 25/25/50 Propane/i-Butane/n-Butane and 20/80 Propane/i-Butane

This is for a canister used upright of course. I reckon the canister needs to be at least 5C above the boiling point for there to be enough pressure to run a stove.
It's a different story when the canister is used inverted of course: the boiling point should remain constant because the mixture doesn't change. In this case, the 30/70 mixture is actually best, but theres not much difference between them.
Feel free to make use of these graphs. They were all generated using spreadsheets and you can download the simple version here (if my link works this time).
Explaining the equations is a bit more involved, but I can if you are interested, or you can look up Raoult's law.
cheers
Stuart

[Stuart R]

I've posted a basic explanation of the theory here, for anyone thats interested.
cheers

[Roger Caffin]

Hi Paul

> Your emphasis on "THAT canister"

I made that emphasis because I do know that different retail brands and different can-filling companies use different odorants, and so the results may differ. I have never had this problem with a Powermax canister, so I am left with a suspicion that Coleman have been careful in specifying the odorant for these canisters.

But getting the chemistry info out of the companies … :-)

cheers

[Roger Caffin]

Hi Stuart

Thanks for all of that. Very helpful.

Cheers

[Laurence Beck]

I keep the canister and the stove in my tent at night and then I put them in my pockets while I am packing up. When I am ready to cook they have warmed up somewhat.

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