Compact/light weight propane canisters

[Roger Caffin]

A factor we should not forget in all this is the customer. A customer is quite happy with a short squat canister onto which he can screw his tiny upright stove. But I suspect said customer will be less happy trying to stand a Powermax or Greengas canister upright with a stove on the end. And should the long thin canister fall over, the stove would switch from gas feed to liquid feed rather abruptly.

On the other hand, with the small diameter in a Powermax canister, you can get away with a thin-wall aluminium alloy. For a short squat canister the forces in the skin are much higher, so you have to resort to fairly high tensile steel, which is both thicker and heavier.

Approximating wildly:
A new full 230 g steel canister is about 360 g. Add 50 g for a UL stove to get 410 g.
A full 170 g Powermax canister weighs about 240 g, and my winter stove weighs about 80 g, to give 320 g. Add another 50 g for pot support and 3-ply base board and you get 370 g. This is less than the weight of the squat upright format.
Hum …

Cheers

 

[David Thomas]

Devin,

One good experiment blows all theories out of the water.  If you’ve direct read what the pressure is, then that’s what it is.  I’ll go back and correct my post – the mole-fraction-weighted vapor pressure only applies if the compounds are mixed.  I’d missed the bit about separate foil bag.  So, yes, I’d agree that propene vapor pressure determines the bursting pressure the canister is subjected to in that configuration (with propene in the foil bag).

[Devin M]

David – No worries, your point about no free lunch stands. If these paslode cans don’t work out I think I’ll just get a few Kovea adapters and use a few 1 lb tanks for car camping. Or make a splitter with hoses as I can do that cheaply. It should still be a more compact set up than full size propane stove and lantern.

James – Thanks for the link to that calculator. Here’s how the green gas compares to Paslode if we put in a tensile strength (18000 psi) that gives us a burst pressure around the DOT 2Q (270 psi). Can’t calculate the actual burst pressure without knowing the strength of each particular alloy, but if we assume they are the same it will give us an approximate idea how they compare to each other.

Green gas: OD 2.08″, Wall .016″, Burst pressure 277 psi

Paslode: OD 1.25″, Wall .022″, Burst pressure 634 psi

That’s quite a bit higher! I think it would equate to around 95 deg C? Which is a similar failure temperature to the isobutane canister Roger tested. Of course the top may fail before that, or the tensile strength I used could be way off, but it does suggest the sidewall is less of a concern.

Roger – Yes, the customers are why this idea is likely not commercially viable. There aren’t enough that would appreciate the benefits and be willing to put up with decreased convenience, so you end up with a very limited market which can’t support the volume necessary to produce at a reasonable price that anyone would be willing to pay.

But hey if it’s cold enough to warrant propane maybe you could just jam the tall skinny tank down in to the snow and make a collar at the base of the stove to stop it from sinking further? That would be nice and stable.

[Roger Caffin]

if it’s cold enough to warrant propane maybe you could just jam the tall skinny tank down in to the snow and make a collar at the base of the stove to stop it from sinking further? That would be nice and stable.

Aaahhh – er – um – oh
Just when I think I have forseen all the problems, someone blows me out of the water. Sure, the snow would be cold, but maybe the top layer would not be that cold? And propane, good to -40 C …

Go on, try it, and PHOTOGRAPH it!

Cheers

[David Thomas]

“use a few 1 lb tanks for car camping.”

Yeah, as much I’ve loved my transitions from Optimus/Svea in the 1970s to MSR stoves in 1983 (admittedly late) to canisters around 2010, I’ve also got parallel set-ups for car camping AND SNOW CAMPING.  Now, if I was peak bagging or doing epic cross country trips in winter, I’d care about weight and size and probably be using a Moulder Strip (TM) (R) to make it go down to very low temps.  But for me, with kids, snow camping means relatively low-angle snow-covered trails.  We might be on skis or might be in snow boots, but I’m pulling a sled.  Weight still matters, but not nearly as much.  And bulk doesn’t matter.

So I’ve got a bunch of 16-ounce propane (plus one pound of steel) cylinders and various stove heads to go on them. There’s a box of full ones for remote trips and there’s a box of partials for car camping and use around the house.  Propane, even in 1-pound containers is 1/3 the price of butane/propane.  And if you refill those 1-pound cylinder (more illegal, but far less complicated than your efforts), then cost almost goes away – equivalent to a 220-gram butane cylinder selling for 35 cents.

And when I’m car camping or snow camping, I bring my HX pot(s) because dinner and drinking water always happens faster in a HX pot (for BPing, they may or may not be worth the fuel weight savings).

[Jerry Adams]

that is really weird that if you keep the propane and butane separate, the pressure inside the canister is higher

maybe you could exploit that?  have the propane inside a bag that breaks open when all the butane is used up and that bag expands to fill the entire canister?

but you’d have the same problem as pure propane – higher pressure when it gets warmer so you need thicker walled canister?

[Roger Caffin]

Hi Jerry

Yes, you are right! How to exploit the idea? … YAKP?
(Yet Another Kickstarter Project)

And yes about the higher pressure anyhow – so why bother with the butane at all? Straight propane in a slightly thicker-walled container is the way to go – with the internal dip tube of course.

Cheer

[Jerry Adams]

If you kept the canister much colder than 120 F you wouldn’t need as heavy a canister.  Like, in winter, I could easily keep it below 80 F, or if I didn’t bring it inside, keep it below 60 F or 50 F.

[Roger Caffin]

Hi Jerry

You are right, you are right, you are right!
But have you ever heard of idiot members of the public and Tort Lawyers?

Cheers

[David Thomas]

“If you kept the canister much colder than 120 F you wouldn’t need as heavy a canister.”

And I’ve done that whenever I’ve put propane into some container it didn’t belong in.  Of course, no one could market that.  And you’ve got to empty all your canisters after a trip or put them somewhere they will NEVER get very warm and CLEARLY mark them.

 

[Jerry Adams]

okay, what’s the max temperature if you put pure propane in one of the standard butane (isobutane) canisters?

[Roger Caffin]

Hi Jerry

A simple question which, as usual, does not have a simple answer. Reference to our article on exploding gas canisters at https://backpackinglight.com/exploding_gas_canisters_the_hazard_of_overheating/ and our article on the temperature effects of cold on canisters at https://backpackinglight.com/effect_of_cold_on_gas_canisters/ will give you graphs of pressure vs temperature. Different gas mixes will give you different curves.

We can take 50 C as a working limit, as that is specified in DoT regulations. With the ‘best’ butane/propane mixes, this gives a pressure of about 150 psia. Other mixes give lower pressures. Straight propane will reach this pressure (150 psia) at 30 C.

So you could get away with it fairly safely (but not legally) in a northern Alaska winter, but it could be very unsafe in California. The flip side is why would you bother doing this except in very serious snow country?

Cheers
(PS: I am not recommending anything; I am just giving science facts.)

[Jerry Adams]

30 C is 86 F

So, you could put propane in a regular canister as long as you kept it below 86 F?

You’d have to be careful it didn’t get warm when you were running stove, maybe put a screen between the burner and the canister

Then it would operate down to -40 F.  Maybe -30 F when you consider evaporative cooling

Again, just scientific data, don’t actually do this : )

 

[Roger Caffin]

With an inverted canister stove it should operate to -40 C (=-40 F).
I am not sure I operate at that temperature though  ;)

Cheers

[Bob Moulder]

Or you could simply refill standard isobutane canisters with cheap butane and have an extremely safe system.

[Jerry Adams]

$20 isn’t too bad.

You could also use that to combine two canisters, so that if you had a day or two left it would be more convenient to get rid of that canister.

Fred Meyer stopped carrying the cheap “Max” isobutane canisters for $4 so this is more worth it to me.

And they have 16 ounce isobutane canisters that are cheaper than 8 or 4 ounce.  You could always put just what you needed in the canister you carry and save a few ounces of unneeded fuel.

[David Thomas]

You’d need a different adaptor to combine two canisters after a trip.  One with a Lindal valve on each end.

[Bob Moulder]

Actually there is something for that, and it too isn’t very expensive: 

[David Thomas]

“With an inverted canister stove it should operate to -40 C (=-40 F).
I am not sure I operate at that temperature though  ;)”

Roger, one of the best rules of thumb I took away from an Arctic Engineering class I took was:

Productivity drops 1% for every degree F below 60F.

So at 10F, you’re 50 degrees below 60F and 50% less productive.  I’ve found that holds pretty true (I’ll be drilling wells in Fairbanks next week, possibly at 0F / -18C).

Our first year in Alaska, I found that the bottom of my fun meter was -15F/-26C.  I can deal with 10F colder just fine, but at those temps little mishaps can become survival situations so I’m not relaxed anymore.

Extrapolating, one gets to 0% productivity at -40.  Which is pretty much true.  You’re not doing any productive work – you’re spending all your time preventing the equipment and yourself from freezing.

[DAN-Y/FANCEE FEEST]

Some good information in this thread on wall thickness of canisters and their strength:

Recently I began looking at options for running my isobutane stoves/lantern etc on propane. Rather ironic that I ended up here, as I was thinking in the context of car camping on a multi-month road trip coming up next year. The goal being cheaper and greater availability of fuel, but avoiding the bulk of full size propane gear. I also want to get back in to winter hiking and camping so the low temp/high altitude prospects are a secondary goal for me but likely the primary for most of you I imagine.

Initially I thought of just refilling the isobutane cans, and in searching that came across the article on pressure testing an isobutane can to failure (https://backpackinglight.com/exploding_gas_canisters_the_hazard_of_overheating/), which was informative.

Anyway, I thought I’d post about this as I’ve come up with an approach that doesn’t seem to have been discussed here as far as I can tell from searching.

[IMG]http://i64.tinypic.com/168vqqs.jpg[/IMG]

Green gas is propane and a small amount of silicone oil, used in some airsoft guns. It appears to come in aluminum or steel cans, and I tracked down some aluminum ones (250 + 1100 ml). I thought the seamless aluminum would be a better bet given the point of failure being at the seam in the above test. The cans have the same style of nozzle and top diameter as the butane cans used to refill lighters. Adapters for this style of can to threaded lindal are cheap ($5+), or a bit more if you need a stand and hose, which would likely be necessary with these tall cans unless you already have a remote stove.

I assumed the propane can would be stronger, but they both have DOT 2Q rating (minimum wall thickness 0.008″, tested to 270 psi without bursting) so I decided to cut them open and find out. For fun I threw a can of sunscreen in to the mix, also with a DOT 2Q rating.

[IMG]http://i68.tinypic.com/2dvl8nn.jpg[/IMG]

The butane and green gas both have a wall thickness of 0.016″ and the sunscreen is 0.013″. The bottom of all three cans is thicker than the sides. Butane 0.038″-0.064″, green gas 0.052″-0.08″, sunscreen 0.029″-0.058″.

I was surprised how thin the wall was especially on the green gas can, and that it was the same as the butane can. If I use this I would be inclined to sleeve it with some inner tube or a coat of plasti-dip, bed liner, etc. to prevent drops or scrapes from weakening the wall. Without knowing the exact specs on the aluminum it’s hard to calculate the theoretical burst pressure, but if .013 can pass the 270 psi test then .016 should clear 330 psi if it’s linear. This would be reached around 60 degrees C, and it’s hard to imagine how it would get that hot unintentionally if it’s not used directly under a stove. Maybe sitting out in the sun all day? I’m not involved with airsoft so I don’t know if many of them are missing fingers from using these cans, but I can’t imagine it would last on the market if it was a big problem.

So…thoughts?

[Jerry Adams]

what?  we were asking all the same questions in 2016???

some new information though, it’s all good : )

 

[David Gardner]

Ha! I was even a member back then and have no memory of this thread. I should do a search on whatever subject it is I’m thinking about creating an “original” post for before I do it.

[David Gardner]

Case of Torch arrived today

Can’t wait to try some.

[DAN-Y/FANCEE FEEST]

For the last 4 days I’ve had a canister of BOSS Torch fuel in my freezer. First thing in the morning I would take it out, screw on the Torch and ignite. 4 days and no problems igniting. No “O” rings leaking, lindal valve functions without issues.

 

@gearmaker……..We look forward to your future testing. Have fun! :-)

[Jerry Adams]

Your freezer must be zero F?

If a canister works at zero F that should be good enough for almost everyone

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