The Effect of Cold on Gas Canisters

[Roger Caffin]

Weird. Dunno. Did not happen with mine. Sorry.

Cheers

[Hikin’ Jim]

Stuart Robb said> For a liquid fuel stove, the iso-butane is not neccessary. It will work just as well with regular butane. What is required is 25% or more propane.

Stuart, why wouldn't the isobutane matter? The pressure in the tank is a combination of all the gasses, yes? In very, very cold weather, I would think the approximately twenty degree Fahrenheit difference (between n-butane and isobutane) in boiling points would make a difference yes? After all, it (the partial pressures) all add up, yes?

HJ

[Stuart R]

Jim – did not say isobutane did not matter, I said that it was not neccessary, and this was in response to the comment:
"For temps above -25C (-13F) you can use any of the mixtures that contain both propane and iso-butane with a stove designed to burn canister fuel fed to it as liquid (connected to an inverted canister)."

Isobutane has a vapour pressure ~50% greater than n-butane. With an inverted canister stove, 30% propane / 70% isobutane will work at approx 4C lower than 30% propane / 70% n-butane (look at Fig 4 with 100% remaining).

[Hikin’ Jim]

Stuart,

Ah. That makes sense. Thank you.

And that's a good point about Figure 4. Thank you for that as well.

HJ

[Hikin’ Jim]

So, another question, if I may: Does the following statement (referring to Fig. 4) apply for inverted canister use as well?

"you should be able to use the canister so long as its temperature is approximately 5 C above the relevant line"

HJ

[Roger Caffin]

Hi Jim

Yes.

Cheers

[Stuart R]

Yes

Fig 4 shows the boiling point of the mixture, ie. the temp at which the vapour pressure equals atmospheric pressure. The gas pressure has to be a little more than atmospheric to get thru' the jet and based on experience, 5C above boiling point is sufficient.
There are no graphs shown for inverted use because the gas mixture does not change, so the graphs would be simple horizontal lines aligned with the 100% remaining point in Fig 4.

[Hikin’ Jim]

Gentlemen:

Thank you very much. I think I've got it. Your first comment yesterday, Stuart, (about looking at the values at the 100% mark for inverted mode) made the proverbial light bulb come on for me. When I re-looked at Fig 4 and that section of the article with that in mind, everything fell into place. This all makes a great deal of sense.

Thank you both very much,

HJ

[Stuart R]

When Roger and I wrote this article, my assumption was that a canister which labelled its contents as "Butane" did actually contain >99% butane, and a canister that was labelled "30% Propane 70% Butane" (like Coleman canisters) did contain just that.

But I was wrong. I should not be surprised of course; why would a manufacturer go to the expense of filling canister with a high purity gas which is only going to be burned in a camping stove? No, they are just going to use the cheapest fraction of gas they can get from a petroleum refinery.

So, what is the actual composition of a "Butane" canister?
The Campingaz/Coleman MSDS tabulates the contents of all their canisters under three headings: Butane, Super Butane and Butane-Propane Mix. It then describes each of these as:

Butane: composition in compliance with French decree of 3/9/79
Super Butane: mixture of butanes, butenes and propane (approx. 20%)
Butane-Propane mix : mixture of butanes, butenes and propane (approx. 30 %)

The Comite Francais du Butane et du Propane proscribes the properties of commercial Butane which it defines (in French) as "a mix of hydrocarbons made up mainly of butanes and butenes and containing less than 19% by volume of propane and propene". It also requires the vapour pressure of the mixture to be less than 6.9 bar at 50C.

So, "Butane" is a mixture too: Butanes (n-butane and iso-butane), butenes (4 possibilities, boiling points from -6.9C to 3.7C), propane and propene (less than 19% combined).

The MSDS gives some further information on the atmospheric boiling point of each of these mixtures:

Butane: -5C
Super Butane: -20C
Butane-Propane Mix: -25C

Pure butane boils at close to 0C, so clearly the other components of the "Butane" mixture are significantly depressing the boiling point.

Older versions of the MSDS also listed the PowerMax canisters containing Butane-Propane (40%) mix with a boiling point of -26C.

Conclusion? Depending on where you hike, "Butane" may be adequate for 3-season use, other brands may vary.

[Nate]

Does anyone still have the spreadsheet for this article? Thanks!

[Roger Caffin]

Does anyone still have the spreadsheet for this article? Thanks!

Of course, but which one? There are at least 6 spreadsheets in that article iirc.

Cheer

[Nate]

Of course, but which one? There are at least 6 spreadsheets in that article iirc.

The titular spreadsheet under the last section (“The Spreadsheet”), originally linked but now 404 here: https://backpackinglight.com/backpackinglight/images/effect-of-cold-on-gas-canisters.xls

[Roger Caffin]

I have asked BPL to sort this out. It seems that the whole article has been lost – from the web site. However, I still have all the sources, including the spreadsheets, so we can resurrect everything.
Hum – well, mostly. I am working on it.

Cheers

[Jerry Adams]

Somewhere I have the spreadsheet that calculates amount of n butane, isobutane, and propane vs time.

[Roger Caffin]

Oh, for sure. I have the sources for the whole article after all.

But while it is easy to put images up, even images of graphs, putting up a full spreadsheet inside a web page is a shade more complex. It is not an embedded image: it is usually a separate file you download and run on your machine.

OK, that is not entirely correct. You can embed a simple sort of spreadsheet into a web page, but the HTML code for that is a shade complex, and in this case it could put a bit of a load on the BPL servers. Or it could make the HTML code you download huge, which most readers would not want. 0.5 MByte for the spreadsheet data, PLUS many MBytes for the psuedo-Excel spreadsheet SW to interpret it. And there would be all sorts of legal hassles with distributing Excel!

Cheers

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