Fuel Losses when Connecting / Disconnecting Canisters

[Bonzo]

As I discovered late in this thread, the fuel that escapes from a canister during connection/disconnection to/from a stove can be unexpectedly high: I found that with poor canister discipline – canister on side, tilted, inverted, fumbling during threading/unthreading, etc. – I was seeing losses of over a gram during each cycle.  A few posts later, Jon Fong posted some measurements of his own with two different stoves than the one I was using, and found losses as well: somewhere around a third of a gram for each connect/disconnect pairing.

I decided to do a direct measurement using his method:

1. Weigh canister.
2. Connect and disconnect canister to stove ten times.
3. Weigh canister again.
4. Divide result by ten to get an average.

My results with an Optimus Vega (for which I’ve been building the windscreen) and an MSR 211g Isopro were better than what I saw previously with the same stove and a Snow Peak Gigapower 211g canister: approximately .574g per paired connect/disconnect cycle, or approximately .287g for each individual event.  This second number is somewhat misleading, however: almost all of the fuel that was escaping was doing so during the disconnect phase, which is an inversion of my experience with the GigaPower canister.  When using that canister, the connection portion of the cycle was responsible for the bulk of the fuel loss…but in either case, more fuel is being lost than I expected.

I wanted to pass this along, as the data surprised me; for those that are only using a stove for a night or two it may be of no consequence, but for those that connect/disconnect their stoves multiple times during the day, the losses can add up over the course of time.

[Scott H]

I use a stove only for breakfast and dinner unless I have an afternoon coffee.  With that said when you spin the stove onto the can if you hear a hiss you are loosing some fuel.  I use the MSR pocket rocket delux, so far when I spin that on it is super smooth so you can spin fast and get a quick seal.  You also loose some gas every time you light up.  I like the striker on the pocket rocket because so far it has lit every time on the first strike.  I think you could loose more fuel fumbling with a lighter or matches than what you waste putting the fuel can on.  Also inefficient use of flame would be or could be an issue.  I do not have a pot cozy, so I get some heat waste but I mainly operate in the summer.

For my last trip I purchased a larger can than the smallest for two people for 4 days, turns out we could have done it with the small can we used less that 25% of the fuel cooking for two twice a day.

In the end there are multiple ways to waste fuel if you are doing a long enough trek that every gram counts.  I think you need to account for all of them.  If you can hear gas and there is no flame in the end you are wasting it.

[Philip Tschersich]

My JB Sol Ti allows me to store the burner with a small canister attached in the pot, so I would go an entire trip without separating the two. The fuel loss during connection or separation always bugged me so that was another selling point for the Sol. It’s interesting to hear how much it might amount to. I have to disconnect the JB Stash each time.

[Bonzo]

I think you could loose more fuel fumbling with a lighter or matches than what you waste putting the fuel can on.

That’s certainly possible.

In the end there are multiple ways to waste fuel if you are doing a long enough trek that every gram counts.

That’s more of my point: it was never in question as to whether or not the hissing of escaping fuel was existent, but rather, the surprising amount of fuel that can be wasted during connect/disconnect events.  I was honestly shocked that the simple act of tilting a canister 15° could equate to an entire gram escaping.  Those small losses add up significantly over time: if you’re losing 10% of your fuel to bad canister discipline and needless fuel loss, you’re not only paying for more more canisters over time, but generating more canister waste as well.

My JB Sol Ti allows me to store the burner with a small canister attached in the pot, so I would go an entire trip without separating the two. The fuel loss during connection or separation always bugged me so that was another selling point for the Sol. It’s interesting to hear how much it might amount to. I have to disconnect the JB Stash each time.

A very good selling point, indeed.  I have been in the habit of packing up and storing my cooking gear when it is not in use overnight – I’m always paranoid about a fuel leak – but ironically enough, this habit has now wasted more fuel than would have been lost if an entire canister or three bled out overnight (which has never happened).  From now on I’ll connect the canister before dinner and leave it connected until it’s packed away after breakfast the next morning.

[Jon Fong / Flat Cat Gear]

OK, I repeated the test using the Soto WindMaster and this time I inverted the canister 180 degrees (straight down).  I did 5 connects / disconnects and my average fuel loss shot up to 1.14 grams per cycle or 3.6 times as much fuel compared to vertical canisters.  BTW, this particular canister was maybe 1/3 full so expect greater losses with a fresh canister.  My 2 cents.

[Bonzo]

I’ll try the PRD tomorrow, from both directions.

[Bonzo]

I checked the Pocket Rock-ette De-luxe (take that, auto-linking!) this morning with the ten-cycle averaging test from both directions: one set with the canister upright, and the other with it inverted around 170-180°.  The results were surprising.

In the correct and upright position the canister lost 0.60g total, over the entire ten-cycle test: that works out to an average of .03g for each connection or disconnection.  I was actually concerned that I wasn’t fully connecting the stove because I didn’t hear any gas leaks at all for the first two cycles; only when I held the stove up to my ear did I hear a tiny “pfft!” upon disconnection.  Disconnect cycles 4 and 5 were the largest escapes; I would guess that they accounted for 75% of what was lost, by comparison.

Inverted, things were substantially different: 2.02g lost during the ten-cycle test, or approximately .10g for each connection or disconnection.  This is 3.36 times as much as was lost with the canister in the correct position.

Preliminary conclusion: stoves may connect better or worse to any given canister, but keeping the canister upright is good practice, regardless.

[bradmacmt]

Out on a pack last week I was contemplating the same connecting/disconnecting issue this thread addresses. Now I don’t need to test myself. Thank you all. Such a great website with so many good contributors.

[Daryl and Daryl]

Good data.

I avoid the potential loss by keeping my stove attached to the cannister for the entire trip.

I don’t like to attach/detach the cannister during a trip for other reasons too.  Cold fuel sometimes gets on my fingers, cross threading potential exists, dirt in screw threads of connection, etc.

[DWR D]

Also… heat makes a difference. If you leave the canister in the sun, the increased pressure will make for more loss when attaching or un-attaching a stove. So will probably lose more in the evening than the morning. And… doing the ten times test, it will likely lose more for the later attempts due to the warmth of your hands.

All that said, not a huge deal for me. I pack a small canister and only used half on a recent 9 day solo backpack… I’m pretty frugal with fuel…

 

BTW, I stopped attaching the canister inverted when some VERY cold liquid fuel froze the tip on one finger… hurt like heck… like a burn :(((

[Kevin Babione]

While I primarily use my Sterno Inferno alcohol setup now, I do have a nice collection of canister stoves too (including one of the original JetBoil stoves from 2007 and the piezo igniter is still going strong) so I’ve been following this thread. I have a couple of questions:

• @Bonzo – What are you using as a scale that measures in tenths of grams?  My wife would kill me if I “needed” a scale that was more precise than to the nearest gram ;)
• Has anyone measured the weight of the fuel used while lighting it?  When I light my stove I basically turn it to the lowest level and then light it with either the piezo or my lighter.  Let’s say that takes 2 seconds…How much fuel was wasted in that time?  What if it takes 5 seconds?
• With my Jetboil I plan on using 4-5 grams of fuel for each pint brought to a full boil – so a full 100g canister will give me 20 boils – and that includes the fuel loss from attaching/detaching the stove with each use.  Are others seeing similar fuel usage?

[Bonzo]

What are you using as a scale that measures in tenths of grams?  My wife would kill me if I “needed” a scale that was more precise than to the nearest gram ;)

I’m not using a scale that measures in tenths of grams; I’m using one that measures in hundredths of grams.  It’s an older Ohaus Explorer Pro; sadly, now discontinued.

Has anyone measured the weight of the fuel used while lighting it?

No, because I’m not sure how to go about it.  Do I weigh the canister, crack the valve, ignite, and then wait for a specified time?  What happens if I don’t get ignition?  Should I not ignite the stove at all?  Would it be better to crack open the valve to the “light” position and wait a specified time to simulate lighting and warming up?

Let’s say that takes 2 seconds…How much fuel was wasted in that time?  What if it takes 5 seconds?

Solid question.  What if it takes neither two nor five, though?  What if it takes ten seconds?  Or, what if your stove – like my Optimus – doesn’t fire and stay lit until somewhere around 40% valve opening?

With my Jetboil I plan on using 4-5 grams of fuel for each pint brought to a full boil – so a full 100g canister will give me 20 boils – and that includes the fuel loss from attaching/detaching the stove with each use.  Are others seeing similar fuel usage?

I couldn’t tell you if the fuel usage is similar, to be honest: I don’t have a JetBoil, so I can’t test it to see what it’s actually consuming per given unit of water boiled.  I can tell you that my Optimus is using more than that, however; somewhere around 8g for each 500ml based on the initial test.  What I would like to do, however, is do a series of ten successive boils with no disconnections; the starting and ending weight of the canister, divided by ten, should give a much more accurate average fuel consumption.  I would then like to do the exact same test with a known velocity of air moving past the cooking site, and then I would like to try out my other stove/pot combinations to see exactly how much fuel they’re consuming.  I’m also going to try a few different canister/stove combinations to check fuel leakage during connect/disconnect; as I said, it’s not a big deal in one moment, but it adds up over time.

[Mark Ferwerda]

Over time the o-ring that seals the base of the stove to the canister will deteriorate. That will also cause a significant loss of fuel when connecting or disconnecting.

[Kevin Babione]

Okay – here’s a really stupid question:  Does a lit stove use more fuel than an unlit one?  In my simple mind, I’m opening a valve 5% to light my stove and the gas output (temperature remaining constant) would stay the same until the canister is empty.

Thus to test it you could weigh the setup to start and then after 10 seconds without ever lighting it.  Divide total consumption by 10 and you have your per second consumption.  Do that 5 times to minimize variances in opening the valve and you might have a usable number.

@Bonzo – To 1/100th of a gram?  Unless you use that scale for something work-related, you are now my Gram Weenie King!  I bow to your minisculness (that should be a word).

[Bonzo]

Does a lit stove use more fuel than an unlit one?  In my simple mind, I’m opening a valve 5% to light my stove and the gas output (temperature remaining constant) would stay the same until the canister is empty.

As long as the flow rates don’t change by the act of lighting the stove, lit versus unlit wouldn’t matter.

Thus to test it you could weigh the setup to start and then after 10 seconds without ever lighting it.  Divide total consumption by 10 and you have your per second consumption.  Do that 5 times to minimize variances in opening the valve and you might have a usable number.

I would say that as long as you know the ignition setting on the stove’s throttle and reach that point in a repeatable, accurate fashion every time – same setting, same timespan, etc. – you could use that method and get decent results.

To 1/100th of a gram?  Unless you use that scale for something work-related, you are now my Gram Weenie King!  I bow to your minisculness (that should be a word).

The scale in question is used at work for certain chemical applications; the scale I have at home is quite a different animal altogether.  It reads in thousandths of a gram.

…and that is the story of how I became known throughout the lands as “King Weenie.”

[Kevin Babione]

I am in awe…

[Bonzo]

I am in awe…

As are all who stand in the presence of King Weenie.

…

…

Sorry, couldn’t resist.  But anyway, yeah, I have a small scale that measures very tiny amounts of things…but it only has a 100-ish gram limit, so it’s not useful for most things.  It’s also stupidly sensitive; if a car passes on the street outside while the scale is in-use, it goes a little bit haywire.  Even walking around the room or breathing on it can throw it off.

[Jenny A]

This thread is timely.  For a couple of years now, I have been using MSR and JetBoil canisters exclusively because they last a little longer at altitude and in cold temps (30’s-40’s).  I almost always use my Soto Windmaster when backpacking, but I’ve noticed that the MSR containers are a little harder to attach to the stove and more fuel is wasted during the attachment process over JetBoil.  I have idly wondered about that difference but have not studied nearly to the degree of previous posters.

[Bonzo]

…because they last a little longer at altitude and in cold temps…

Now that’s an interesting side of things; I hadn’t thought about how different brands might interact in different ways because of T’s and P’s…

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