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  1. #1
    Hobo
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    Project Pressurized Alcohol Stove - explosion danger?

    Hi, what's up? Is the forum not very active these days? The dates of last posts seem pretty few and far between. Anyway, I've not been here for years, myself. I'm just getting my new kit together to do some wild camping, and I have a question about a project for a modified alcohol stove.

    I've used Trangias and one or two pop-stoves, and was going to make another when I found small aluminium screw-top jars online, about 5 cm across and 2 high, with plastic foam inserts to seal. I bought a few and stuffed one of the bases with rockwool and a bit of mesh to cover. It burned ok just like that, but with the whole of the top burning it was undirected and easy for the breeze to push about. It needed jets...like penny stoves and other pop-can stoves...

    So I had the idea of using one of the tops on it, with a smaller hole cut in the centre (ditching the plastic foam insert) - another lid with insert could be put on to store unburned fuel. How big to make the centre hole?...

    I then had the idea of dishing the lid downwards, but pushing up to make the hole, creating a little depression in a ring around the hole, so I could put a small amount of alcohol in it as a primer and not have to fill the whole stove. If the screw thread sealed the container (without the plastic stuff), pressure would build up as it heats and create a single jet in the middle. I tested the seal by putting one in a jug of hot water to see if bubbles came out of the screw area, and none did, so it's feasible.

    I dished the top and poked a hole from inside as planned. Now, here's the problem: if this hole is made big enough, presumably it gets to being much like an open dish of fuel (with or without wick) burning without a build-up of pressure. But if it's too small a hole, could it heat up too much and create enough pressure to explode, or could the enclosed ethanol/air mixture get to combustion proportions and explode for that reason?

    I know a similar container (paint can with hole in the lid) full of gas burning from the hole gets to that point and blows the top off, because it was a school physics demo, but that's with whatever gas bunsen burners use, and alcohol might not do the same thing.

    It's possible that once burning, as the pressure increases from the heat of the flame, the flame will exhaust faster and thus direct heat away from the stove more, and thus it'll be self-regulating, or it may just be impossible for pressure to build up in such a situation because the vapour can escape so fast.

    On the other hand, if it acts like the bunsen gas in a can, yikes.

    Any thoughts? I could just go for the safe option of a moderate sized hole, but I imagine that just being a slower version of the whole tin open at the top, still being blown about because of no pressure build up. It's tempting to try the jet version, but I don't want to have an accident ... when I'm solo wild camping.

  2. #2
    Ranger Ehecatl's Avatar
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    Hello. The forum is not very active these days. I think FB and similar are the new norm for posting stuff. Now onto your question. In short, I don't know. My thought was, could you fashion some sort of push-fit lid (like a paint tin has) and test it with that? If the lid doesn't get blown off, then the screw on version should be ok provided you have the same sized holes. Another alternative would be a pressure relief valve but that could be cost prohibitive.

    Good luck and stay safe!
    "If you were to ask me what I consider to be my finest achievement, I could answer the question without hesitation: teaching." ~ Raymond Blanc.

  3. #3
    Hobo
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    Quote Originally Posted by Ehecatl View Post
    Hello. The forum is not very active these days. I think FB and similar are the new norm for posting stuff. Now onto your question. In short, I don't know. My thought was, could you fashion some sort of push-fit lid (like a paint tin has) and test it with that? If the lid doesn't get blown off, then the screw on version should be ok provided you have the same sized holes. Another alternative would be a pressure relief valve but that could be cost prohibitive.

    Good luck and stay safe!
    Thanks! That's a great idea about a push-fit lid, I didn't think of that. I'm pretty sure there isn't a risk with this anyway - if the hole is small, it doesn't produce enough heat - I gave up and just use the burner without a lid.

    I joined another forum (Bushcraft UK) and was surprised to see it's very active. I think it's from having things like buy and sell sections, and the owner seems very proactive in welcoming newbies, introducing where you can say hi, and then others welcome you as well. Not sure what's going on here, but it ain't much. Oh well, thanks for your reply, and take care too!
    John

  4. #4
    Ranger Ehecatl's Avatar
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    "If you were to ask me what I consider to be my finest achievement, I could answer the question without hesitation: teaching." ~ Raymond Blanc.

  5. #5
    Woodsman rik_uk3's Avatar
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    As a 'stovie' I'd not pressurise alcohol unless it in a stove designed to do just that like an Optimus 111T which will also burn paraffin/Coleman fuel/Panel wipe. You could always buy one of these and slot it in your Trangia 25/27 https://www.ebay.co.uk/itm/162388381...Bk9SR6iNwaGgYg

    No connection to seller
    Richard
    South Wales UK

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