Exactly how many canisters does one have to go through in a year that the small savings of refilling vs. buying canisters for hiking becomes a real issue? What is saved? A few dollars per canister
before considering the cost of the refill adapter? You still have to buy the refill butane, and typically it is n-butane, rather than an isobutane/propane blend which will perform better in cold temperatures. If I hiked
all summer and used a small canister per week, I'd save $3 per week net on fuel, or $40 for the summer. I don't see where it is worth the time involved plus the associated safety risks. I weigh my partial fills and use them for overnights/weekends, and once really low when car camping or when testing trail meal recipes.
Anyone considering refilling DISPOSABLE isobutane canisters should read these threads
http://adventuresinstoving.blogspot....r-warning.html and
http://adventuresinstoving.blogspot....refilling.html and then proceed at their own risk.
Quickly summarized - potential problems (many dangerous) including one's not mentioned in the linked page:
1) Even IF you eliminate all the other safety concerns below, these canisters and especially their valves are not designed for repeated and prolonged use. Typically, 100 grams of fuel (small 4oz canister) will boil 12 liters under optimum conditions. So, that's 48 liters for the largest (16oz)canisters available that use this type of valve(Lindal), or maybe 100 connect/reconnect cycles if you boil 1/2 liter per meal and disassemble the canister from the stove each use. I'm sure the valves are designed and tested for much more frequent use AND abuse, likely by factors of 1000's of times or more, because that's how important safety is when dealing with flammable/explosive gases. But as with anything else, they are designed to be as economical as possible to manufacture while fulfilling their designed purpose. And their purpose is NOT to be repeatedly used beyond their designed life, which is one time use. They are designed to be safe and function with the normal contamination and wear expected from their one-time designed usage, but the more you reuse them the more they wear and the more contamination (such as minute particles of dirt) wind up in the seal and valve assembly.
2) Refilling with propane/LP gas, or any mix of fuel that creates vapor pressure greater than the design pressure rating of the canister, could result in failure of the valve or canister itself. 100% propane will create pressures approximately 3 to 4 times those that the typical 80/20 or 70/30 isobutane/propane blend creates in the sealed canister. Note the thickness of steel, construction of valve and fittings, pressure relief valve, etc. on a propane/LP tank vs. the rolled edge seam, thin wall steel, and Lindal valve on a canister. Enough said.
3) Control of filling - manufacturers precisely control the amount of fill to ensure adequate empty expansion space in the filled canister. Failure to do so could result in a catastrophic hydrostatic failure of the canister. And does anyone know the other process controls they undoubtedly use while filling to ensure product safety/reliability?
4) Safety controls. What happens if a bad leak develops during refilling? What about fire suppression and emergency response? Add the possibility of static spark during refilling, and thus the need for proper bonding and grounding regarding the refilling process. How about a small leak you didn't notice, with isobutane now slowly filling the trunk of your car as you drive to the trailhead?
Seriously, there is enough explosive potential in a small canister to kill you. People have died from small stove canister explosions!
5) Unknown quality of refilling devices/components. Things like quality of the machining of threads, seals, and others. A lot of the refilling parts on ebay, et al, come from unknown manufacturers and origins. With translated instructions from foreign languages that read like a fortune cookie.
6) Availability of refill gas. Most of these adapters connect an n-butane canister to an isobutane/propane blend canister. You are refilling with fuel that doesn't work very well in temps below 40°F.