Mar 17, 2009 at 3:15 pm #1234885
Companion forum thread to:Mar 18, 2009 at 7:23 am #1486652
Great article and insight. Being new to UL and having so many questions, I've often wondered how to service as Vargo Jet-ti. As minimal as the stove is, so is the servicing instructions and tools included. No complaints. Excellent stove. Excellent article.Mar 18, 2009 at 2:04 pm #1486807
The following question was raised by email:
>Why do you call for "cool" water to pre-warm a cold canister? It seems that
> even "hot" water up to the point that you can put your finger in it comfortably would
> be OK. Are you just being conservative? Or, is there some other reason that you don't
> want the canister exposed to temps up to 105F or so? Is there a thermal stress issue
> on the canister or some other problem if one side is 32F and the other is 100F?
It may be worth while first repeating what was written in the article:
>However, do not try pouring hot water over the canister: that can be dangerous. It's
> OK to add a few spoonfuls of warm water to the bowl, as long as you keep the water
> in the bowl on the cool side: below skin temperature.
First of all, the canister is rated to be able to withstand up to about 50 C by DOT regulations. That is over the 'OK-to-touch' temperature which is around 40 C. This is covered in our article on Exploding Gas Canisters. There are no stress worries.
However, there is another hazard which is not covered by that regulation, and it is this extra hazard I am concerned about. The pressure inside a canister is a function of the temperature, as shown here:
As you can see, the pressure rises fast as the canister warms up. In fact, it nearly doubles between 0 C and +10 C. Now, ask yourself what would happen if you suddenly poured very hot water over the canister **while the stove was running**? The pressure in the canister would rocket, and the fuel flow into the stove and through the jet would rise dramatically. This could cause a dangerous rise in the flame height from the stove (flaring), or worse still it could increase the flow to the point where the flame lifted off the burner and blew out. Both are very dangerous.
For this reason I have warned against using 'hot' water. After all, anything above 0 C is warm enough to make the butane boil and the stove work. Hotter than that is wasted.
So, start with water from your water bottle (or a creek), get the stove running and some water warming. Then add a few spoonfuls of warm water to the dish of water while the stove is on a medium to low setting. This will bring the water temperature up to (say) 10 C, which is plenty warm enough. You don't need anything more.
CheersMar 18, 2009 at 2:51 pm #1486826
I was trying to get the last fumes out of a isobutane canister at 30F/0C. Just a spoonful of hot water made enough flare to get my attention.
I don't think it was that the pressure got too high, rather the quick increase pushed the cool, dense butane that was in the tube up and out.
In the future I won't do that while the stove is running.Mar 18, 2009 at 6:30 pm #1486925
Good to know. Never had thought about stove maintenance. Thanks for the article.Mar 18, 2009 at 10:02 pm #1487001
What is that tent of yours? The doorway and the colour are so similar to mine!
CheersMar 19, 2009 at 10:07 am #1487107
Hilleberg Kaitum 2 GT
Have not taken a crap in the vestibule yet – but it is on my to do list : )Oct 15, 2011 at 9:33 pm #1791072
On the stoves I have owned (a camping gas and pocket rocket) the valve is held in place with a pin. So valve maintenance is impossible. As to the jet I cannot remove the burner (the parts appear to be pressed together) on the pocket Rocket so cleaning the jet is also impossible. fortunately I haven't had an problems.
I don't agree with the author about the odorant as being the most likely cause. It is unlikely ethyl mercaptanhe is the cause because it evaporates at -148C. It won't be in solid form at the jet or valve. Instead I think the silicone oil the author recommends applying to the valve might be the cause. Silicone oil is composed of silicon carbon and hydrogen. If it gets to hot it can leave behind solid silicon byproducts which can block the jet.
"white grunge (brown arrow) around the needle valve from the author's favourite Snow Peak GST100. How it got there and exactly what it was are unknown, although I may have been operating" with an inverted screw-thread canister at the time."
Using this stove with an inverted canister would require heating the fuel before it gets to the jet. This is often done by placing a metal rod in the flame and attaching the other end to the valve body. This could get the silicone oil hot enough to break down and plug the jet.Oct 15, 2011 at 10:54 pm #1791084
> On the stoves I have owned (a camping gas and pocket rocket) the valve is held in
> place with a pin. So valve maintenance is impossible.
Ah, and the valves on some of my stoves were held also locked in by some mech or another. In the case of pins, I just pressed them out. They are roll-pins, and this was easy enough to do. The pin is there to satisfy the lawyers, to make sure I can't unscrew the valve so far that it falls out. Can I assume you know better than to do that – at least while the stove is connected to a canister!
In the case of lock nuts, some of them were held in by Loctite or similar. Boiling water and the right sized spanner fixed that.
> I cannot remove the burner (the parts appear to be pressed together) on the pocket Rocket
Over the years I have collected a few stoves from most of the vendors around the world. I have yet to find one stove which does not permit the owner to remove the jet for cleaning.
The burner tube on my Pocket Rocket is attached to the base with what looks to me like an M11 x 1 thread. Yes, it was screwed on tightly.
> I don't agree with the author about the odorant as being the most likely cause. It
> is unlikely ethyl mercaptanhe is the cause because it evaporates at -148C. It won't
> be in solid form at the jet or valve.
I agree that it is most unlikely to be ethyl mercaptan. However, the odorant does not have to be ethyl mercaptan, and the fuel does not have to not-contain-anything-else. It is interesting that some (not all) screw thread canisters have given this problem while the Coleman Powermax canisters have never given me this problem.
My interpretation is that the fuel in the Powermax canisters was more highly refined, precisely because the fuel was being used as a liquid feed, while many screw-thread camisters have less refined fuel because they are designed to work upright. If the fuel evaoprates off, any contaminants are going to be left at the bottom of the canister – and there is often quite a smell if you open up a genuinely empty canister. Perhaps there are cheaper odorants than ethyl mercaptan which don't evaporate that easily?
In the worst case (some cheapy Chinese canisters), there was also fine dust in the fuel – that played merry hell with the jet on a winter stove when the canister was inverted!
Note that none of the normal screw-thread canisters are warranted for use inverted. That is not part of their specification. Caveat Emptor. (Footnote: I have emptied 450 g canisters of French Campingaz inverted with never a problem.)
> Instead I think the silicone oil the author recommends applying to the valve might be the cause.
Oh, that's possible, for sure. But this happened before I ever stripped this stove down for maintenance, and I think others have also had the problem with other stoves. The silicone grease (not oil) could have been applied by the manufacturer, but where it would have come from within the stove … I don't know. Anyhow, I never apply *that* much grease!
CheersOct 15, 2011 at 10:56 pm #1791085
> I was trying to get the last fumes out of a isobutane canister at 30F/0C. Just a
> spoonful of hot water made enough flare to get my attention.
Oh, been there done that many times. Warm water is fine, but don't use boiling water.
We also sometimes sit the canister in a dinner bowl of warm water in the snow – works great, but do insulate the bowl from the snow!
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