No if you're transferring can to can. Use a digital scale to avoid overfilling. Mark full (new from store) weight and empty weight on can. Never exceed the former (although I have by a few grams).
If I understand how this thing works, you are just connecting the two cans together, and then since the full can is at a higher pressure gas will flow into the empty can. You could also freeze one can and have the other warm to affect the pressure. But at most you are just equalizing the pressure between the two, right?. So won't you just end up with a lot of half filled cans this way?
If I understand how this thing works, you are just connecting the two cans together, and then since the full can is at a higher pressure gas will flow into the empty can. You could also freeze one can and have the other warm to affect the pressure. But at most you are just equalizing the pressure between the two, right?. So won't you just end up with a lot of half filled cans this way?
My (probably limited) understanding is that the canisters contain fuel in both liquid and vapor form, and while the vapor pressure between the canisters may equalize, the liquid fuel would drain from the top canister to the bottom. Disclaimer: I have only read about this and haven't tried it.
So won't you just end up with a lot of half filled cans this way?
No. Even if you do it wrong (see below re doing it right), the lower can will become more full because the liquefied fuel under pressure moves from the top can to the bottom can via gravity.
Opus wrote:
You could also freeze one can and have the other warm to affect the pressure.
See my first post re this reco:
-- Cool the lower (recipient) can by placing in an ice water bath during transfer. You can also precool the recipient can in a freezer before the transfer, although IME that does not obviate the need to keep the recipient can relatively colder during transfer.
-- Preheat the upper (donor) can by running under hot water before transfer.
I have confirmed via weighing that this method, when done correctly, will result in near emptying of the donor can (unless, of course, the receiving can becomes full or overfull during transfer).
If you do it correctly, the transfer happens fast, i.e., usually less than a minute. Be sure to weigh the recipient can after transfer because it's easy to overfill. Better yet, weigh both cans before starting transfer to determine whether the combined content of both cans exceeds the capacity of one can. If so, shut down the transfer early and weigh recipient can.
ETA: Big thanks to someone (HitTheTrail?) for recommending this device a couple years ago.
ETA2: An example: One of my Jetboil Jetpower cans has a gross mass of 387g full/new, 230g net fuel mass design capacity per label (confirmed by weighing) and 157g empty can mass. I wrote those numbers on the can with a sharpie and do calculations to determine whether there's a risk of overfilling (if it's a recipient can) or whether it's empty (if it's a donor can).
No. Even if you do it wrong (see below re doing it right), the lower can will become more full because the liquefied fuel under pressure moves from the top can to the bottom can via gravity.
Ah right, I forgot about the liquid in the canisters. Makes sense.
Going to buy one of these now.
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