Hey, gas canisters are expensive. Why NOT just refill them with cheap gas from a bulk propane tank?


A "bulk" propane tank


Yeah, and on eBay you can get a cheap canister refiller that will do just that.

A very dangerous canister refill adapter


But refilling backpacking canisters with this particular canister refiller is inherently dangerous. Find out the whys and wherefores in my latest post:
Canister Refiller -- WARNING

HJ

No idea if this is a real problem or not. I don't know what the little canisters are rated for. It does seem plausible though.

lol. Thanks for your vote of confidence.

Backpacking canisters are generally intended for a blend of gasses, typically propane with either butane or isobutane. When you blend gasses, the resultant mixture has a vapor pressure somewhere between the various vapor pressures of the constituent gasses.

Now, go look on line or in stores. You will find no brand with more than 30% propane. A little flimsy (by comparison to 100% propane car camping canisters) backpacking canister just isn't built for 100% propane.

HJ

You certainly won't catch me anywhere near such a disaster-waiting-to-happen.

HJ

I am assuming you're referring mostly to the lightweight gas canisters for backpacking stoves? In which case I would agree with you, I'd never try and refill them.

Here's a diagram on the vapor pressures of different mix ratios

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

You can see that propane has a much higher pressure compared to butane

However, I do have a coupler for filling the small 1 lb propane bottles from the larger bulk tanks, but those 1 lb bottles are built a lot heavier than a standard stove canister. Even though I've read refilling those aren't recommended, but I've never had a problem and the risk seems much lower.

Nothing "mostly" about it. I am referring to the lightweight dome shaped canisters for backpacking stoves.

I believe they can be refilled safely -- just not with 100% propane.

The key thing here is to know the max weight before you start and never refill to greater than that weight. Overfilling is a sure way to have problems.

HJ

Where's Blast? I bet he invented that tube!

(I'm joking! I hope ... )

Maybe not, but I bet he could have, er, a "blast" with it. lol.

HJ

Have no fear, Blast is here! Let just order the gizmo and...funny, the back of my neck suddenly feels warm

...oh.

-Blast, being glared at by his wife.

Why is that NOT in either safety lime-green or safety orange? I'd buy it!

it seems that refilling fuel carts has caught on lately.it started from filling camping carts from the cheaper cans made for the Asian table stoves to this gizmo,the plastic tube put me off from the get go.my fear is that someone will blow them self and everything around to bits and adapators that can and do work are taken off the market.

I hear you, but strictly speaking, there aren't any backpacking canister refillers on the market now. No company with a legal presence in the US dares sell them; the potential liability is just too great. You have to buy them over eBay. Good luck suing an individual seller who lives in China or the like.

HJ

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

My guess is that the margin of safety on the Butane cannisters is adequate. Hook one up to an air hose and see what pressure causes a failure. You can control the resulting pressure by controlling what temperature your fill bottle is at.

I have not heard of one blowing up inside a hot car in the desert.

As IlBob said, is this a real problem? Yes, there is the potential for an explosion, but I don't know if the risk warrants trying to take this product off the market. We really don't know what the actual risk is, other than propane does a higher pressure which may lead to problems. But without actual data or testing, is this really a cause for concern?

I wonder what was this product advertised to do? And were there any instructions on how to use it properly and warnings how to prevent over pressure? I'm not usually in favor of banning items based on assumptions, unless there was a real danger in normal use and no attempt to warn consumers of the potential dangers or evidence of problems in the field.

I would hope in a well designed system, the seal will fail long before the container strength is an issue. That being said, I still wouldn't use this product because the cost savings just isn't worth it unless I was burning through canisters every day. The few dollars a year I might spend on fuel is just the cost of the hobby. But other people might have a legitimate use for this.

I understand the issue with refilling canisters such as these is not over-pressurizing them with gas, per say.

The issue is when you go and fill them 100% with liquid, leaving no headspace. When this is done, even a slight thermal expansion of the liquid has no gaseous buffer to expand into, splitting the container.

The safety of butane canisters is most definitely adequate. On butane. Put 100% propane in that same canister, and you're very likely to have some serious problems.

Yes, but again, those are properly filled with a butane blend. This guy is selling a device which fills with propane.

Tell you what, buy the device, put it in a hot car in the sun on a hot day, and stand WAAAY back with a camera. When you've the video posted on YouTube, let me know.

HJ

Would you over inflate your car's tires by more than double their rated strength? Perhaps there are circumstances where your tires might not burst, but would you do something that extreme?

This is that extreme.

HJ

Not everyone should play with things that go BOOM. The easy part is just don't buy it. Don't whine about the guy selling it.

This product, however has some applications. There are many appliances that fail to function in the bitter cold and high altitude. Butane stoves are in that class of limp wristed products that need to be understood. At -20 deg F, this solution may work fine.

One application involves adding other liquids and gasses to the stoves bottles other than its original intent. The problem always always involves figuring out the plumbing. This guy has helped out with a turnkey product!

Here is some other fodder. Take your empty propane bottle and remove the valve by unscrewing it. Pour some of your fuel of choice into the bottle - gasoline, alcohol, Ronson, etc, etc. Now replace and seal the valve back on. Take it down to your local propane dealer and have the tank topped off. You now have YOUR CUSTOM mixture for your Butane stove.

If you want a custom mixture for your propane weed burner, add styrene packing beads and diesel before you top off the propane tank. The "NAPALM" will stick much better to the brush and grass.

Well, Cliff,

Maybe so, but most people would have no idea that it has the potential to be as grossly unsafe as it is. Perhaps at the very least my blog post will serve to educate.

100% propane in a backpacking canister actually would be fairly safe at -20F. At -20F, 100% propane would be at about 11.5 psig. Backpacking canisters should be able contain at least 100 psig (although you're starting to push it there). You'd have to be really danged careful you didn't forget and bring it in the nice warm house after your trip. But I still wouldn't use this el cheapo rig with aquarium tubing to try to transfer propane.

If you get one, let us know how it goes.

HJ

Let me say first that I agree with you on the risks and I personally wouldn't do it myself. And I applaud you in your efforts to warn other people. But at that point I would say it's up to the individual to decide if they want to use it. I wouldn't recommend inflating your car tires to twice the rated pressure, but I don't think air compressors should be limited to 40 psi just to avoid the potential problem. You can't protect everybody from their own stupidity, it's up to the individual to know the risks.

To play devils advocate, you state "I believe they can be refilled safely -- just not with 100% propane". I'm sure there are some people who think that there's enough safety factor in the canisters to fill with propane, then on the opposite extreme you'll have people who say it's not safe to refill at all, even with butane. Who's right? Unless someone can come up with data to support their position, it's all just feeling. You probably knew all the risks involved before you bought this contraption, yet you wanted to try it for yourself. I think other people also have the right to make their own decisions about it.

EDIT: I actually re-read you post and am confused. Did you actually buy this device and try it out for yourself?

OK, good example. But say you pulled into a gas station to fill up your tires with air and the compressor at the gas station shot your tires up to double normal in a split second. Safe compressor or unsafe?

I think most people would say that, for filling tires, it's better to have a compressor that is a little slower.

So, I agree with you that we shouldn't approach life with the equivalent of a 40psi cap on everything we do -- but there are safe ways to do things and there are unsafe ways. A compressor that shoots your tire pressure up over double normal inflation in a split second is probably not a compressor that the vast majority of us would want to use to fill our tires.

Likewise, I agree, there are people who will have reason to put propane in canisters not rated for propane-level pressure. Cold weather hunting or backpacking comes to mind. So long as you exhaust the canister before you bring it into a warm environment, you should be OK.

But would this device be the way to do it? To my mind, no. This device is so shoddy that I wouldn't use it even if I thought the application were appropriate.

Heck no! I wouldn't want to be within a quarter mile of this thing if it were in use. I'm not afraid of canister refilling if intelligently done. I'm not even afraid of using propane if intelligently done. I'm afraid of this device and of the directions the seller lists with this device. Who in their right mind uses aquarium tubing to transfer propane!?

HJ

Thanks for the heads up. I have a different device I bought through a catalogue, much different than what you have shown. Never had a problem but now I'm a lil concerned with the cannisters I have at the cabin.

Interesting. Do you have a photo?

What kind of canister did you refill, what did you refill them with, and were you careful to only fill to their rated weight limit?

First, the most critical thing is to note how much a full canister weighs when you bring it home fresh from the store. When you refill, NEVER exceed this weight. Overfilling can lead to dangerous pressure levels inside the canister. If you forgot to weigh the canister when you brought it home, you could weigh an empty canister and add the net weight printed on the canister to derive your max weight, but I think weighing a fresh canister is the better option; it avoids any potential math errors.

Second, know what type of canister you're refilling. Is it a 100% butane canister? Is it a butane blend canister? Is it a 100% propane canister? Different canisters can accommodate different gasses, and you need to know which type you have.

Last, only refill with a gas or gas blend with a vapor pressure that is equal to or less than what originally came in your canister. Do NOT refill with a gas or gas blend with a higher vapor pressure. Generally, refilling with 100% butane is relatively safe (as safe as canister refilling gets anyway) because 100% butane will always have equal to or lower vapor pressure than any combination of the gasses typically used to fill canisters (butane, isobutane, and propane).

You can get some idea of what's going on with various blends by looking at the following chart:


Note that the above chart lists propane and butane only. Isobutane is not listed. Vapor pressures with isobutane will always be higher. So, that chart can give you some idea with propane and butane, but don't use that chart for isobutane. You'll need to look elsewhere for that information.

HJ

Assuming I survive, the first thing id be thinking is where can i get one of those compressors? On a somewhat unrelated but equally dangerous topic, i have read of people using their spare tires as an air tank, filling them to 80-105 psi. I dont know if it was a widely used practice, but it seemed fairly common to read about it. Again, not something I would do, but it's one of those things that many people have done without dying. So while a compressor like that could be dangerous, I wouldn't see the need to have it removed. Maybe a warning sticker or something

I will admit I was curious about the product you showed so I looked it up on eBay to see how much it was. One thing I noticed was that it never really said it was used for refilling propane, only liquified gas. There is a picture in the ad of some sort of blue bulk gas canister, but I can't read the writing on it because it's in Chinese. When I looked closer at the picture, I'm not even sure if it's even possible to connect this hose to a standard propane tank, at least not to the common type of propane valves that we use in the US. Are you sure this isnt a butane tank refiller that is meant for the overseas market?

Depends on the spare, some donut type is actually designed to run at very high psi, something around 80.

The product was for sale on US eBay. In the US, that connector attaches to "bulk" propane tanks.

HJ