Winter Stove Discussion – 2014

So I've read up on the inverted canister stoves – like the Spider previously discussed – and I want to clarify a few things…

I keep seeing in different posts that a liquid fuel stove is almost twice as inefficient as a canister stove… So I'd be taking twice as much white gas as I would canister gas… This is slightly offsetting the cost efficiency of WG. So I only have the figet factor of cold weather canister operation to address if I want to replaced WG on my wish list:

Since an inverted canister can maintain pressure due to a small percent of propane (which should be good to vapourize in my expected temp ranges) I'm wondering if anyone has measured the evaporative cooling rate of inversion stove use? What I'm getting at is I know how difficult it can be to keep a Jetboil going in 0F melting over 4 litres worth of snow… I'm wondering how long an inverted canister can function if it's taken fresh from my sleeping bag and placed in a down hat or similar cozy? I find that by removing the phase change from the canister it should, technically, maintain gas pressure and fuel flow down to the melting point of propane… Unless someone can school me better.

Thanks

Mitch,

I cannot answer your exact question, but I have used inverted canisters down to -15f and they have burned
solid emptying the can. I always try to keep cans warm by stashing in clothes in my pack.

One thing that I find is after I turn off the gas the stove will run for 5-10seconds after, I presume that's
the liquid fuel in the hose.

Stephen, is that unattended use or are you managing the canister with water, hand warmers, or a preheat loop (alpine bomb)?

Mitch

BPL has an absolute heap of articles on canister stoves. Can I suggest that many (or most) of your questions might be answered by reading them. (Disclosure: I wrote a lot of them.)

> the evaporative cooling rate of inversion stove use?
Essentially zero when the canister is inverted.

> how difficult it can be to keep a Jetboil going in 0F melting over 4 litres worth of snow…
Well, it can be a little tricky with an upright Jetboil, but try sitting the canister in a bowl of COLD (or very cool) water. That will keep it going well.

With any inverted canister stove, the smart trick is to put a few spoons of warm (or even hot) water into the bowl-shaped base. Replace when the water turns to ice. And no, I am not just being funny!

> how long an inverted canister can function if it's taken fresh from my sleeping bag
> and placed in a down hat or similar cozy?
I wouldn't bother with the cozy. Just let it get a LITTLE bit of radiation from the stove to keep it around 0 C. Make sure the canister never gets too hot to touch, that's all.

> maintain gas pressure and fuel flow down to the melting point of propane.
Not quite. Read our stove articles for the techie details. -24 C is about the open/bare limit for the canister – but the canister does not have to get that cold.

Cheers

Mitch,

No water involved, sometime the canister was sitting on snow others on some foam,
Once or twice it was in a cosy. The stove has a built in pre heat tube.

"> the evaporative cooling rate of inversion stove use?
Essentially zero when the canister is inverted"

and as you've said in the past, the small amount of propane in the canister will provide the pressure to push the liquid out

since liquid is being pushed out, there won't be a gradual decrease in proportion of propane in the mix so it should continue working until empty

and the canister doesn't have to stay above the vaporization temperature of isobutane, all it has to do is stay above the melting temperature which wikipedia says is -300 to -28 F – I don't understand the large range.

and the vaporization temperature of propane which is -44 F.

so, as long as you're above -44 F (or -28 F?) inverted stove should be okay

"so, as long as you're above -44 F (or -28 F?) inverted stove should be okay"

Nope, gotta stay above the vaporization temp of the mixture, same as non inverted. Otherwise the internal canister pressure is lower than external pressure and you have no force to drive the liquid out.

Your other points are correct and highlight the value of inverted use.

I'm basing this on theoretical, not actual use, so…

If you're above the vaporization temperature of propane, and there's enough propane in the mix, then there will be enough pressure to push out the liquid propane/isobutane mix.

For the above….there will be some propane exerting a PARTIAL pressure on the mixture. The isobutane will also exert a much lower partial pressure and the actual overall cannister pressure will be inbetween the two.

Google Raoult's law.

Also, see here:
http://www.engineeringtoolbox.com/propane-butane-mix-d_1043.html

And, as Roger is about to tell you (once he gets outta bed), read Stuart R's and his article on this topic:
http://www.backpackinglight.com/cgi-bin/backpackinglight/effect_of_cold_on_gas_canisters.html#.U_oe8iXD8m9

That's a good article – I see what you mean about partial pressure of isobutane and propane combining

For figure 1, the -20 C case, for several common mixtures at 100% remaining, the pressure is about 1150 mbar. Atmosphere is 1000 mbar. So that should be enough pressure for it to work?

Since we're talking inverted, it should stay at that pressure for the entire canister.

-20 C is -4 F. So that should be about the lower limit for inverted canister.

But if you start with a warmer canister, it has minimal evaporative cooling, so it should only slowly get colder, so it should be straightforward to use even below -4 F.

> And, as Roger is about to tell you (once he gets outta bed), read Stuart R's and his
> article on this topic:
> http://www.backpackinglight.com/cgi-bin/backpackinglight/effect_of_cold_on_gas_canisters.html#.U_oe8iXD8m9

Nice warm comfortable bed with a good quilt …
But yes, that article really is required reading for winter campers.

> But if you start with a warmer canister, it has minimal evaporative cooling, so it should
> only slowly get colder, so it should be straightforward to use even below -4 F.
I do keep harping on this point (I know), but it is worth remembering. Just because the ambient is -20 F does not mean the canister has to be that cold. There are many ways to warm the canister up a little bit to get it going, and once the stove is burning you can use the heat of the stove to keep the canister warm (not hot).

Cheers

I wonder if anybody has gotten their white gas stove cold enough to quit working?

I've used an XGK down to -33F and it worked fine.

If a white gas stove did stop working because of the cold, it wouldn't be for the same reasons canister stoves stop working. As mentioned above, the problem with canister stoves in the cold is lack of pressure in the canister. White gas stoves don't rely on pre-pressurized canisters. You use a pump to supply your own pressure.

I've taken the gamble and purchased a Kovea Spider. Provided this inverted system works without much fiddling down to -4F I'll be a happy camper. In worst case scenarios I can push it another 20F colder using the same fiddling as I do now with the Jetboil. Now that's not to say I'm going to be saving any money in fuel costs remaining with the canister system but I might have saved a couple pounds than had I gone with the XGK EX.

>"Plus, the price per gallon of water from snow is is obviously better with liquid fuel."

Hopefully you know this, but don't argue price of fuel until you've got one of the better heat-exchanger pots. Within 4-8 person-nights (or with any snow melting), their slight weight penalty is recovered through greater fuel efficiency.

I've also had good success pairing two pots such that one pot (full of snow) serves as as a snug lid for the lower pot. Then the water vapor (prior to boiling) and any outright steam (if you simmer or aren't mindful and let a pot keep boiling) isn't wasted but goes into melting the snow. Yes, the lower pot will take a bit longer to boil, but (1) those beans and rice take longer to cook at altitude, (2) that heat isn't wasted if you needed to melt the snow anyway and (3) you'll generate much less humidity in a tent or cabin (by condensing that steam) and that's a big plus.

> I wonder if anybody has gotten their white gas stove cold enough to quit working?
It is possible. Below a certain temperature the standard O-rings in the pump stop sealing: they get too hard. Viton goes to -25 C; some other rubbers are not so good.

Cheers

I'm not sure what the MSR o-rings are made of (a quick google couldn't determine), but common 70 durometer silicone is good down to -65F, and there are others with a much colder rating. But they do stiffen up a bit below zeroF (google "challenger feynman").

http://www.websealinc.com/oring_temperatures.html

In my experience, the most common cause of o-ring failures is scuffing when inserting a fuel tube into the pump assembly without first lubricating the tube. Mineral oil, vaseline, chap stick all work fine for this purpose, and all it takes is a very tiny amount.

Since there's no pump, I wonder how cold it has to be for a SVEA 123 to quit working?

The original Svea123 would get awkward at cold temperatures unless you could get it primed just right. The mini pump sped up that process. Also, you had to insulate the fuel tank underneath from the snow.

My big MSR white gas stoves kept operating right up until they ran out of gas, regardless of cold.

–B.G.–

Yep Bob, my Dragonfly has operated very nicely at -22 F. and I even baked a jelly filled large Bisquick biscuit with it that night. That was SO good to eat at those temps.

ALTERNATIVE STOVE:
My Traill Designs Sidewinder with the wood burning Inferno insert works well in any frigid temps if you don't mind feeding it every few minutes with finger sized sticks.
In fact the oxygen-rich cold air makes it burn even better with a stronger draft due to the temperature differential between near-zero outside air and hot internal stove gasses.

Hi Bob

> but common 70 durometer silicone is good down to -65F,
True, but silicone O-rings are rather porous and are not recommended for use with hydrocarbons.
I guess you could try using them once it gets seriously below freezing.

Cheers

"silicone O-rings are rather porous and are not recommended for use with hydrocarbons."

Ah, this is true. I should have remembered from my gasoline and methanol engine encounters.

In that case, nitrile, and there are others that work well with naphtha.

http://www.efunda.com/designstandards/oring/oring_chemical.cfm?SM=none&SC=Naphtha

I haven't tried, but I'm fairly sure these can be ordered from McMaster-Carr. Times like these it's nice to have a good digital micrometer.

I've used my SVEA123R at 0*F and found that it is easy to prime and light. It runs sitting encased in the snow, but it runs hotter when sitting on an insulating pad. It is nice to not have to pump it and it is fuel efficient. I doubt I'll ever use it in sub-zero weather but I am curious what becomes the critical item when it is really cold.

Hi Bob

> In that case, nitrile,
One reference says the temperature range for nitrile is -40° to +225° F, -40 C to +143 C, but this is a bigger range than most others suggest.
A second reference says -34 C to +100 C – depending on the version of nitrile used.

Yes, nitrile can go lower in temperature, BUT …
The canister won't work below -24 C anyhow
An upper limit of around 100 – 120 C is, to my mind, a bit dangerous. Stoves get HOT.

So, yes, other rubbers are possible, but so far I have not found anything (commercially available and affordable) which is better for our needs than Viton.

Cheers