I have lots of half empty screw top gas canisters (coleman etc) that I want to empty. I know you stick the gas in the freezer, attach the adapter and then refill a canister but is there a website that takes you through the steps and which adapter do I need?

lots on eBay but they seem to be for filling screw canisters from the cheap butane (tall) cans rather than screw top to screw top…

Don’t, just don’t would be my advice.

this was mentioned on a thread a few years ago

http://www.ebay.co.uk/itm/G-WORKS-Gas-Saver-R1-Cartridge-Exchanger-Anodize-Duralumin-Shifter-Outdoor-UK-/222566139716?hash=item33d1f9c744:g:~dwAAOSwFJBZV6vg

http://singletrackworld.com/forum/topic/alpkit-brukit-out-of-the-box-review-and-test/page/3#post-6369895

You’re reliant on a pressure difference to do that. so it’d be one can in a bucket of icy water, the other in warm water and a pipe between. Im not sure how the screw cans are valved, but you might end up needing valves in the connecting piping….

I doubt you’re going to transfer enough to make the process worthwhile.

I use a G-Works jobbie like the one in the link below. (Although my recollection is I only had to pay a tenner or so.)

https://www.amazon.co.uk/G-works-Gas-R1-Cartridge-Exchanger/dp/B00TXZ4JUA/

The Gas Saver and Gas saver plus, brilliant bit of Kit. Temperature differential helps. 30 cans turned into less than ten. Just run the can your emptying under a hot tap for 5 minutes.

You’re reliant on a pressure difference to do that

You’re reliant on gravity to transfer liquid.

While I couldn’t possibly recommend it on H&S grounds I have had some success with a thin stiff plastic tube to depress both valves and a section on rubber hose to form a seal. I sure the adaptor Stoner linked would do it much easier and safer, and with less gas loss.

Use the G-Works thing, bottom (recipient) can straight out of the freezer, top can straight out of hot water, with a bit of boiling water poured in the concave base just for luck.

Don’t do it indoors while smoking tabs.

Better yet, save the £20 for the adapter and just run the canister empty by actually using it next time you’re camping.

I doubt you’re going to transfer enough to make the process worthwhile.

You can. I’ve been buying C500s cheap and filling up C100s from them for a couple of years now.

Use the G-Works thing, bottom (recipient) can straight out of the freezer, top can straight out of hot water, with a bit of boiling water poured in the concave base just for luck.

That’s exactly how I do it and it works quite well although some cannisters wok better than others.

Make sure you weight them before and after to ensure you don’t overfill.

You’re reliant on gravity to transfer liquid.

Much quicker to use pressure to help though. And let’s be honest who could resist giving the doner can a good shake?

Use the G-Works thing, bottom (recipient) can straight out of the freezer, top can straight out of hot water, with a bit of boiling water poured in the concave base just for luck.

Agree. However, in practice I’ve rarely bothered with hot water. Cool the target in the freezer, and use my body heat plus a good shake or direct sunlight to warm the doner and the liquid floods from donar to target so fast you can hear it.

Make sure you weight them before and after to ensure you don’t overfill.

This, I write the weight on when they’re new.

Just use a stove that doesn’t require disposable cans?

Rachel

Some good advice. Especially writing the weights on full cans.

I’ll go for a gas saver plus then. eBay seems the cheapest place…

I made a thingy in about 5 minutes:

It transfers from big resealable (cheap) to little resealable (less cheap). No leaks, death etc.

Always do it in an enclosed space and by candle light for best results.
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n.b. Some of the above may not be true 😉

Ar$e, double post

n.b. Some of the above may not be true

n.b. fume leakage may make you prone to double posts.

It transfers from big resealable (cheap) to little resealable (less cheap).

Yup.

No leaks, death etc.

As useful as it is, I don’t think it makes you immortal.

Much quicker to use pressure to help though. And let’s be honest who could resist giving the doner can a good shake?

I still can’t resist giving the donner a shake even knowing that as soon as both cans are connected with the valves open to allow transfer the pressure will equalise 🙂

I still can’t resist giving the donner a shake even knowing that as soon as both cans are connected with the valves open to allow transfer the pressure will equalise

Yup, but only after a load of fluid has been pushed down into the ‘target’ can.

I doubt you’re going to transfer enough to make the process worthwhile.

I’ve got one of the G-Works thingumywotsits too, actually works really well. So long as you get a decent temperature differential between the two cans it’ll transfer the vast majority of gas from one to the other.

It works fine. Recipient in the freezer, donor at ambient. Weigh recipient before and keep at an angle when filling so there’s always a gap inside. Refill to original weight. Job done.

I’ve missed the self immolation/emergency surgery steps for clarity 🙂

Can someone explain how this ‘angle’ thing works?

It makes sense if you’re pouring water into a glass so the excess will flow over the rim, but unless I’m missing something fundamental it’s surely utter nonsense in a sealed system?

Is the logic that the ‘shoulder’ is higher than the valve? Won’t the pressure broadly equalise when the fluid level is the same across both tanks though, rather than when it reaches the valve?

Or have I got a complete GCSE Physics failure here?

Can someone explain how this ‘angle’ thing works?

No idea, when I use the adaptor, I just put them on the ground bolt upright no need for an angle of any kind.

*If* I fill a C100 from a Butane Lighter fuel refiller then I seem to have to wobble it a bit and hold it at about 25 degrees angle to the target to get it going but that’s nothing to to with physics – it’s just some feature of the mechanism/valve. …but that’s not what we’re talking about here IMO.

I think the angle thing is to to keep a vapour pocket in the receiver to avoid over filling. Weighing can also help this.

I think the angle thing is to to keep a vapour pocket in the receiver to avoid over filling.

Yeah, I wasn’t really asking “why” so much as “how.” I can’t envisage how tilting it will make any difference to that.

Bubble of vapour trapped in the shoulder that is higher than the valve and enclosed so can’t escape.

What is the largest can of butane/propane mix that will work as donor?

I’ve not done anything as clever as maintaining an angle and mine seemed to work fine. I may have been lucky.

I’m using c500 ATM as that is what I happen to have to hand. I usually use ~20-25g of gas per day back/bikepacking. Return from a trip, top up the little can back to 190g total, phone firebrigade, visit A&E etc….

Not sure it’s any riskier than using my various petrol stoves. My Whisperlite feels like it’s about to detonate every time I use it 😉

What is the largest can of butane/propane mix that will work as donor?

I don’t think there is an upper limit. As long as it fits your adapter. In practice I think the largest (cheapest) canister you can get with the coleman screw[1] is C500. You can probably get adaptors to connect all kinds of cannisters, or get them made up.

What you must bear in mind is that Butane is lower pressure than propane. Your Coleman canister is 70/30 Butane/Propane. So you can fill it with neat butane but if you fill it with neat propane it’s potentially going to be higher pressure than the can is designed to take. (If you did some research and some maths you could work out how hot it has to be for 100pc Propane to go beyond the max pressure the can is designed for, in which case perhaps you could safely use 100pc propane on frosty days – personally I’d avoid this for all kinds of reasons!)

All of that is academic for me – I just buy C500s which are 70/30 split.

[1] EN 417 7/16″ UNEF threaded Lindal B188 valve.

i use the blue camping gaz containers and refill the with the lighter butane canisters without any adapters,

psa erics angling website have. the c500 canisters really cheap

refill the with the lighter butane canisters without any adapters

I was astonished this worked but it did. Unfortunately I tried in autumn and lighter fluid is 100pc butane. So come the first frost there wasn’t enough pressure to push the gas out. Cue me putting an ice cold cannister against my flesh to try to get enough heat in it to actually work. 🙁

Bubble of vapour trapped in the shoulder that is higher than the valve and enclosed so can’t escape

The vapour will condense as the pressure increases, so this does not guarantee that the canister won’t be overfilled. Weighing it is the only way.

Weighing it is the only way.

Agree the only way to be sure and the easiest way…

…but on the other hand if you give it a shake and there sounds like there’s some space in the top, and you know the temperature isn’t going to increase much before you use it that’s probably good enough.

I’ve always been careful to leave a decent gap, but doesn’t the valve handle overfilling? Presumably the excess fluid can push past the valve & turn to gas. It’s not going to be much and won’t hang around forever. Surely nobody designed a valve that doesn’t handle overfilling in a sensible way?

(If you did some research and some maths you could work out how hot it has to be for 100pc Propane to go beyond the max pressure the can is designed for, in which case perhaps you could safely use 100pc propane on frosty days – personally I’d avoid this for all kinds of reasons!)

You don’t need to the internet provides a chart:
http://www.engineeringtoolbox.com/propane-butane-mix-d_1043.html

Looks like it would need to be fairly cold before Propane pressure is as low as Butane on a hot day.

doesn’t the valve handle overfilling?

I don’t know if there’s an over-pressure relief built into disposable canisters* (why would there be?). Even if there were, you would get gas being released inside your tent / car / whatever on a hot day. If there isn’t, the risk is that an overfilled canister bursts, releasing the whole lot at once.

*For clarity: AFAIK, the head space is needed to prevent the pressure inside the container reaching dangerous levels in warm conditions. I believe 80% capacity is the maximum for LPG in normal refillable containers, but have no idea about disposables.

I don’t know if there’s an over-pressure relief built into disposable canisters* (why would there be?).

Because one day someone is going to leave a canister in a hot car in death valley and when that happens the designer will have wanted it to harmless vent a small amount rather than fail in some terrible way.

Even if there were, you would get gas being released inside your tent / car / whatever on a hot day.

Yup, but assuming it vents sensibly it will be in tiny quantities. (I have no idea if that assumption is correct.)

Google doesn’t tell if it seeps round the edges or fails bigly. Maybe someone with more braincells than me can work it out from this diagram:

What is the largest can of butane/propane mix that will work as donor?

What did you have in mind?