Thread: refill your disposable canisters

cheers

Ok so I never had much luck with my one as it wouldn’t thread into the LPG cylinder enough so gave up on it.

Then today I stumbled upon this and have ordered one, will report once I’ve tried it. https://www.mtn.co.nz/product/gas-ca...refill-adaptor

Hi guys, I haven’t read though the whole thread but can I suggest you put the empty can in the freezer before filling. (Stuff moves from hot to cold) law of physics. And yes the full bottle needs to be upside down to get liquid out. Be very careful not to over fill as it needs space to expand.

Refilling camping canisters with LPG is extremely dangerous. There is a very good reason LPG and 100% Propane are stored in heavy steel vessels.

DO NOT DO WHAT THESE GUYS ARE DOING!

There are 3 main gases we use for cookers. n-butane, Isobutane and Propane. They all have different properties and we use them in different situations.

The boiling point of the gases are:
n-butane = -0.4C
Isobutane = -11.7C
Propane = -42C

As you increase the gas temperature above the boiling point of the gas the pressure inside the canister rises. At 20C n-butane is still pretty harmless and can be contained inside a plastic Bic lighter, you could not do this with 100% Propane. Have you ever seen one of those green steel gas canisters that Coleman makes? That's 100% Propane. That is what is needed to contain that gas.
So n-butane is no good for our needs and 100% Propane is no good due to the heavy steel vessels we would need to contain it. What we use is a mixture of Isobutane ( a chemically rearranged n-butane which lowers the boiling point) and Propane. A lot of gas canisters don't list the mix ratio anymore but it's around 80/20.

LPG in New Zealand is typically 60/40 Propane and Butane.

What happens when you fill a camping canister with LPG and your pot of boiling water overflows onto the canister below? Or you use a windshield around your cooker? These canisters are not designed to withstand the pressures of the higher ratio of Propane. You are literally risking your (or whoever is near the stove) life doing this guys. Youtube has some examples of what a camping canister explosion looks like - Do you really want to risk it?

The only way you should refill your camping canisters is with the same blend of gas it originally had in it. Since most manufacturers don't list the blend anymore the only real way to minimise the risk is to transfer from the same brand to the same brand eg. MSR to MSR. It's generally cheaper to buy gas in the larger bottles so this really the only reason to be doing this, or you want a custom amount inside a canister instead of two small ones you could take a 3/4 full larger can and save on the weight of the can material.

The correct way to do the gas transfer is to weigh your empty canister first and record the weight. Say it was a 230g canister and the empty canister weighed 150g. You would fill the canister until it weighed 150+230=380g this is the safe amount. Do not overfill. Put your donor canister (of the exact same blend of fuel) in warm (NOT hot) water and your receiving canister into an ice bath. Once the donor canister has warmed up you invert it and using the adapter you start to fill the receiving canister which is still in the ice bath. Let it fill for a minute or so and then weigh the receiving canister. Repeat until you reach your safe fill value. If you exceed the safe fill value vent the excess off outside or use a stove to burn it off.

I can post some links to further reading and a suitable adapter if anyone is interested to learn more. I would recommend any of you that have filled your canisters with LPG to vent them off.

Here's a picture taken from Kiwicamping website showing some typical vessels for the gases mentioned. Note the LPG and the 100% Propane are in heavy duty steel vessels.


Here's a video showing how camping style canisters are manufactured and tested. Note how they are tested in 52C water. Take a look on a canister some time it will state do not use them above 50C for Isobutane. https://www.youtube.com/watch?v=81lwc0L8Tfw

And finally a report of someone being injured by using a windshield around a gas cooker ( Can only assume it was regular Iso/Butane mix gas). The likelyhood of this happening is greatly increased with a higher percentage of Propane. Don't let it be you, your family or friends for the sake of saving a minimal amount of money.
https://worksafe.govt.nz/topic-and-i...burn-injuries/

gentlemen -this bloke obviously knows his stuff .having read it his advice is definitely cheaper than an undertakers bill and the bill for the post match function (he cant be here but deep down hes a nice guy so drink up and have another on him) so Im firmly in his court.
BTW I also have a long standing aversion to things that can bite me or inflict pain -gases and electricity are top of the fucking aversion list.

Originally Posted by K95

Here's a picture taken from Kiwicamping website showing some typical vessels for the gases mentioned. Note the LPG and the 100% Propane are in heavy duty steel vessels.
Attachment 135432

Here's a video showing how camping style canisters are manufactured and tested. Note how they are tested in 52C water. Take a look on a canister some time it will state do not use them above 50C for Isobutane. https://www.youtube.com/watch?v=81lwc0L8Tfw

And finally a report of someone being injured by using a windshield around a gas cooker ( Can only assume it was regular Iso/Butane mix gas). The likelyhood of this happening is greatly increased with a higher percentage of Propane. Don't let it be you, your family or friends for the sake of saving a minimal amount of money.
https://worksafe.govt.nz/topic-and-i...burn-injuries/

Im not condoning refilling any disposable canister, but that work safe report tells us nothing.
What a waste of time, what can we learn from this incident?

LPG (propane) gas cylinder-bottle pressure chart
Temp Temp Pressure Pressure Pressure
ºC ºF kPa PSIG Bar
70 158 2482 360 24.8
60 140 2013 292 20.1
54 130 1794 257 17.9
43 110 1358 197 13.6
38 100 1186 172 11.9
32 90 1027 149 10.3
27 80 883 128 8.8
16 60 637 92 6.4
-1 30 356 51 3.6
-18 0 152 24 1.5
-29 -20 74 11 0.7
-43 -45 0 0 0
Note: Some numbers have been

Originally Posted by 2post

Im not condoning refilling any disposable canister, but that work safe report tells us nothing.
What a waste of time, what can we learn from this incident?

It's an example of how explosions and injuries happen. Most of us have used windshields with upright canister stoves before and got away with it. Using LPG inside a canister increases the likelyhood of an explosion by lowering the temperature at which it will explode. That's the takeaway.

A chart of Propane pressures means nothing because we don't know at what pressure the canisters will explode. They are tested with a certain mixture of gas at say 52C and labelled not to be used above that temperature. Putting a different mixture of gas in there invalidates that test.

I was going to put a pt for butane up as well but having trouble getting a screen shot from my phone to my tablet.
The pressure at 30 deg isn’t much different.
It’s illegal to refill a disposable cylinder but most will cope with either gas pressure.

The work safe report says the stove fuel was LPG but the gas canisters was butane.
What was it?
The only learnings we can take from it is don’t use portable stoves if you are an idiot of work for worksafe.

Ok.

If you are gonna be so cheap you have to look for ways to squeeze the gas, maybe you have bigger problems..... most of the time I'm using Hexi or Meths, cheaper than gas by the way...... so the gas canister thing isn't a bugger for me, occasionally go gas cause I've got shitloads of canisters.

Is this whole refill canisters thing about being cheap? or not knowing how much you have left?. Both problems solved by changing your fuel methodology. Or carrying two canisters if no 2.

In the mornings I generally heat water till just hot to touch then disconnect and put the can of gas in the warm water for a couple of min and reconnect and continue cooking.
My issue is keeping the gas warm enough to supply enough pressure to the cooker especially as boiling off liquid has a refrigerant effect, I dont hunt in +30c temps tho and YMMV.