Canister Refiller — WARNING

I don’t know if the seller on eBay knows how dangerous his product is. I wrote him but got no answer. I also reported the item to eBay. The item is still there this morning. I really hope no one gets hurt because of this thing. It’s not instant death, but it is an accident waiting to happen.

HJ
Adventures In Stoving

If you follow the sellers directions why would it be dangerous? His photos are very descriptive.

Because Jim's science is correct and your could hurt yourself and others. The pressures are easily double what the can is designed for.

I can imagine what Chinese consumer protection regulations are like. I think this character has taken two devices and re-purposed them to work together in a way they were never intentioned. Getting horribly burned or killed to save a couple dollars is just getting in line for the Darwin Award.

Used to work in the aerosol industry. There are DOT specs to the canisters that are used, and can be transported. Any can with the rolled lip and standard aerosol valve, which is what you find on the gas blends canisters, is NOT rated for the pressures propane exerts. That is why the 100% propane canisters are thicker stronger steel, with more robust valves and safety release valves. It is all about the vapor pressure. And to the poster that said that propane and butane are not that different in size, you are right, there is only one -CH2- unit difference, but in a molecule that small, that is a huge percent increase in moelcular weight (propane MW= 44, butane = 58, 31% increase in MW), thus the large drop in vapor pressure from propane to butane.
Another hazard of this is over-filling. All liquified gas canisters should have "head space" to allow for expansion of the gas if it is heated. The hazard being, if you overfill the canister, there is no room for the gas to form, you get hydrostatic pressurization and the canister fails. It is industry standard to leave 15-20% volume of a canister empty for headspace.
I would also say that this device looks incredibly dangerous from the perspecive that the tubing used looks like simple PVC or tygon tubing, which IS NOT RATED for the pressures you are going to be transferring that gas at. You should only be using tubing rated for pressure, which will have a braided stainless sheath around the tubing core.
Another issue to consider as well, the DOT specs for canisters that are considered refillable vs non-refillable. Non-refillabel canisters do not have to pass results for long term use and are not spec'd to be corrosion resistant. When refilling a canister you are potentially introducing water vapor which can potentially corrode the can causing catastrophic failure. Refillable DOT canisters are made with this corrosion resistance in mind, and therefore are "over-built" to make sure that they can withstand some corrosion without failure, at least until the next testing period. ALL refillable DOT canisters have notices on them regarding occasional hydrostatic testing.

Roger said this:

Obviously filling can be done – after all the supplier fills the canister in the first place.

Tony identified one of the major problems. If you overfill a canister and it gets hot it can explode. There MUST be gas space left above the liquid. But without an LPG valve on the canister, how will you know when it is full enough? Dangerous stuff.

There is a second problem. When new the surface of the Lindal valve is nice and smooth and shiny and it seals well agianst the Neoprene or Viton O-ring in the stove. When the canister comes from the factory this plating is protected by the plastic cap. But in our fine profit-driven society we find that the plating on the steel is so **%%$$## thin the steel does start to rust rather quickly. A rusty surface may not seal adequately, leading to a gas leak …

The canisters are rated to take up to a 30% propane content (depending on brand) at up to 50 C. Fill them with LPG and you have a potential bomb. Trust me, they can explode with appalling consequences. No, don't trust me – go read our article on exploding canisters at
http://www.backpackinglight.com/cgi-bin/backpackinglight/exploding_gas_canisters_the_hazard_of_overheating.html

So, what can you do with the empties? RECYCLE them!
But first make very sure they have been punctured. You don't need to spike the metal – a dangerous business anyhow most of the time. Let the canister run out while using it. Then take it home and hammer a nail down through the Lindal Valve. You will break the plastic doodad inside and all will be well. This can be done with the shepherds hook part of a titanium tent stake too, with skill.

Cheers

Very interesting article to be sure. But given the risks involved… and especially how inexpensive new canisters are… it's really not worth refilling at home. I certainly wouldn't do it.

clear plastic tubing for a pressurized application, i'll take 3!

That's the most dangerous propane hose combo I have seen. First the hose and fitting are made for low pressure air for aquariums Instead of braided rubber hose crimped on so the hose does not come off or leak.

For the size canister we use the canister cost is cheap. I have seen people refill car camping stoves canisters but that dangerous also. Most people just use the refillable large white canister with proper adapter to cook with car camping.
Terry

Roger says canisters are rated to contain 30 percent propane.

Ebay seller says:

"Please observe the change of real-time weight, when the weight reach the rated weight(Suggest below the rated weight, This would ensure security), please close the valve on the big gas tank at once, then close the valve on the Inflatable converter."

The seller clearly suggests to fill below rated weight.

30 percent leaves plenty of head room for expansion.

Using an electronic scale as instructed by seller will let us know when to close main valve. The electronic scale is our safety gauge.

Fill to recommended weight and were good to go.

Use appropriate hose and clamps and were good to go.

potentially missing the point, but 30% full of 100% propane is still 100% propane and all the vapor pressure that come with it.

I don't see how under filling addresses that the canisters are not built to hold the pressure.

The hose is the safety as it was pop before the can ;)

That’s the most dangerous propane hose combo I have seen. First the hose and fitting are made for low pressure air for aquariums

I don’t know for sure, but that’s what it looked like to me too — an aquarium hose. It sure isn’t anything I’d want to run high pressure through. And the hose barbs without clamp? On a more or less stretchy type material with nothing securing them in place? No thanks.

HJ
Adventures In Stoving

As soon as you have liquid propane in the canister the canister pressure will be the vapour pressure of the fluid.

So it doesn't matter if the canister is 90% filled with liquid and 10% filled with gas or 10% filled with liquid and 90% filled with gas the Vapour pressure and therefore the pressure the canister sees is the same.

Therefore a canister not designed for 100% propane vapour pressure is not safe to fill to any capacity with propane.

Roger says canisters are rated to contain 30 percent propane.

Yes, but as Cameron points out above, that’s 30% propane with the remainder being some form of butane. When you blend two gasses together, the resultant mix has a vapor pressure that is somewhere in between the vapor pressures of the constituent gasses. In other words a propane-butane mix will have vapor pressure lower than propane but higher than butane. With a 30/70 mix (by weight), the vapor pressure will be closer to butane than it is to propane. Note: The actual pressure calculation is fairly complex and depends upon molar fractions rather than the fraction by weight, but 70/30 by weight can give us a “ballpark” estimate.

Filling a canister 30% full of just propane is NOT the same as filling a canister with 30% propane and 70% butane. Yes, you will have identical amounts of propane in both canisters, but the canister blended with butane will have a much lower vapor pressure. Yes, as odd as that sounds, the canister with more in it will actually have less vapor pressure. Isn’t chemistry fun? :)

HJ
Adventures In Stoving

And in another thread Roger said this:

"A caution about what you use for refilling. While the standard canisters are rated for 70%(iso)butane/ 30%propane, they are NOT rated for straight propane. Propane has a far lower boiling point and will make the pressure too high for the ratings."

And in the same thread Edvin said this:

edvin mellergård
(Edvin)

Real scientific figures on 07/18/2010 13:05:28 MDT
At the end on this page there is a graph displaying the pressure for variuos propane and butane blends, both in metric and imperial.

http://www.engineeringtoolbox.com/propane-butane-mix-d_1043.html

Dan,

The tables from the engineering tool box site you reference prove why this device is not safe.

At 60F a 100% propane mixture, regardless of how much you put in the container will have a pressure of 93 psi

At 60F a 70% Butane, 30% propane mis, regardless of how full the canister is will have pressure of 36psi.

The canisters have been designed for the Butane/propane mix and not just pure propane. By filling with pure propane you are over doubling the pressure in the container. This is not safe.

What part of the Eng tool box table makes you think that this is safe to do?

Hi, Dan,

Yes! You’ve got it. This is exactly what I’ve been trying to get across and why I’m so concerned about this particular refiller.

If someone uses this particular refiller, they can wind up with pressures inside the canister that are WAY over what the canister is designed for.

This is a good discussion. Thanks for asking the questions.

HJ
Adventures In Stoving

Kudos to Hikin Jim for hiliting this and keeping on it. Folks need to be informed.

The behavior of mixtures vis-a-vis vapor pressure does seem counter intuitive but that does not make it false! I can only point out that it is not reasonable to deny or fail to accept advice that this is dangerous when the only reason is that you don't understand why. You need to have a reason to believe or accept that it IS safe.

Sorry to be blunt, but proceeding in absence of that reason is volunteering for what one local radio personality used to call "Nature weeding out the stupid".

OK, I'll crawl back under my rock now.

My Snow Peak canisters read, "WARNING: DO NOT REFILL."

My 1 lb propane canisters read, "Never refill this cylinder. Refilling may cause explosion. Federal law forbids transportation if refilled – penalty up to $500,000 and 5 years imprisonment (49 U.S.C. 5124).

I knew this before Jim posted the thread. I am sure my MSR canisters have similar warnings, but I am too lazy to walk out to the garage and get one.

Why warn people, let nature (Darwin) takes its course. Fewer people in the wilderness the way I look at it. :)

Nick,

There’s refilling and then there’s refilling. Yes, they all say “do not refill,” but a lot of people do refill and have done so safely with the appropriate gas/gasses. My objection here is not so much refilling in general but rather refilling with inappropriate gas/gasses. That and the fact that this particular refiller appears to be so shoddy.

HJ
Adventures In Stoving

Nick, good point. We've all heard about unsafe candy and childrens toys coming from China, this is an example that the Chinese are helping us weed out the dummies in the US, leaving us more intelligent humans to carry forth. Here we just thought we were only sending our hard earned money to them, making them richer.
Duane

"but a lot of people do refill and have done so safely with the appropriate gas/gasses."

Jim, I am going to respectfully disagree on this one. It is safe until one blows up. There are many factors, a big one is how many refills can the valve accept in a canister or cylinder? There is no published standard I have ever read, they are designed to take one initial fill at a minimum. Then there are different blends iso/pro, butane, propane, etc. Do we know the burst rates of canisters? Are MSR's different from Snow Peaks, Optimus, etc.? Too many variables. I will just spend the extra money to minimize the danger. When it comes to stoves I simply follow the manufacturer's specifications, knowing that some of it is determined by litigation and product safety lawyers.

There are many other areas in my life where I can save money.

Again, not challenging you only expressing how I approach things.

Hi, Nick,

No problem. I think a lot of people feel the way you do — and aren’t interested in refilling.

…there are different blends iso/pro, butane, propane, etc.

Indeed there are. I so far have restricted myself to 100% butane for refilling. 100% butane will always have the lowest possible vapor pressure out of any of the possible blends of the gasses typically used for stoves (propane, isobutane, and butane). Lowest vapor pressure = least risk of a canister problem. I am however very tempted to refill my Powermax canisters with a 35/65 propane-butane blend.

HJ
Adventures In Stoving

I’m looking for answers, facts and enlightnments :-) even from those under rocks.

The ebay seller describes his item as:

MacCoupler Liquefied Gas Refill Adaptor Gas Charging Valve Inflatable converter

He does not mention LPG as the gas to be transfered.

A little more research shows me that folks in Egypt use large cylinders of butane gas. Is it possible that the ebay seller is in the mind frame that everyone uses large cylinders of butane? If they use them in Egypt are they also used China also in many other countries. The ebay seller may not be aware of the USA using large cylinders of Propane and the dangers of it.

Here is a headline I found on the internet:

“Sinai Egyptians rioting because butane cylinders smuggled to Gaza”

And here is a photo that was given to show the cylinders being taken:

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The cylinders are very large. They look similar to what the seller shows in his description.

My question to all(even the guy under the rock) is this:

Is the ebay seller using a large butane tank to fill his little butane canister?