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Thread: Starting my new furnace

  1. #1
    Senior Member 4cylndrfury's Avatar
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    Starting my new furnace

    I have started a new furnace. Buster has busted for the last time, and I am ready for a new start. I found a water expansion tank for a water heater on the side of the road, I got a bunch of refractory stuff from a boiler installer. I also got a blower fan from an old oven from my father in law. Heres some pics:

    heres the tank-


    Here it is cut open and the guts removed


    And the manufacturer was even nice enough to include a drain in case of crucible failure:


    And heres the refractory Im gonna use:


    I am going to use a bunch of strips of 1" ceramic fiberboard for insulation behind the refractory that will form the hotface.

    Unfortunately I dont have pics of the blower, but I will hook it up to a dimmer switch for control and it will burn waste oil, and take pics once its operational - soon I hope :twisted:

    so heres the list:
    1. tank for furnace body - free
    2. Ceramic insulation - free
    3. 3000* dense castable refractory - free
    4. blower fan - free

    the only bits that will need to be paid for are:
    1. the dimmer assembly - ~$20
    2. bits for the burner venturi and oil tank ( probably an old milk jug) - ~$20
    and thats it

    Anyway, I will update this thread as the build progresses Im so excited I cant stand it 8)

  2. #2
    very cool man. Sometimes the process of making the new furnace is just as exciting as actually usings. Best of luck!
    "Alas! what perils do environ
    the man who meddles with cold iron!- "
    Samuel Butler

  3. #3
    I would use foam and dense castable mix for the insulation. I dont know what the fiberboard insulation is, probably pretty good but it seems like using strips is going to let the heat right out to the shell, maybe a combination of both?

    An anti freeze, oil or old gas jug will be much sturdier than a milk jug.

    w3

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    Senior Member 4cylndrfury's Avatar
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    W3, when I say strips, I mean that I will cut the panel into 1" pieces with beveled sides, and arrange them inside the tank like wooden barrel. There wont be any gaps. But I may mix up a layer of 3:1 refractory and perlite, and apply a layer between the barrel and the hotface as a little extra protection. If what I read in other threads and on the website about WMO burners being able to reach iron temps without much trouble - around 3000* if I recall correctly, my 2400* ceramic board will not make it (not that I plan to melt Iron at a=ny time, but I want to be able to progress there if I want to later). But Im hoping that if I put a layer of refractory/perlite between the ceramic and the hotface, it may protect the ceramic board.

    And I do have a few old jugs like what youre talking about, but now Im thinking about a 5 gallon bucket with a lid. I could probably even add a little pressure to help mist the spray of oil in the venturi better. I will see what happens. Thanks for the ideas

  5. #5
    Senior Member ragingslab's Avatar
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    Sometimes the process of making the new furnace is just as exciting as actually usings.
    "The Process" is what I enjoy the most. I get "post-project-letdown syndrom" once I finish something no matter how good or bad it turned out.
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    Administrator Site Admin Anon's Avatar
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    Quote Originally Posted by 4cylndrfury
    But I may mix up a layer of 3:1 refractory and perlite, and apply a layer between the barrel and the hotface as a little extra protection. If what I read in other threads and on the website about WMO burners being able to reach iron temps without much trouble - around 3000* if I recall correctly, my 2400* ceramic board will not make it (not that I plan to melt Iron at a=ny time, but I want to be able to progress there if I want to later). But Im hoping that if I put a layer of refractory/perlite between the ceramic and the hotface, it may protect the ceramic board.
    Perlite melts significantly below 2400F, and is a flux once molten. Use foam instead.

    If that ceramic board is anything like the ceramic wool I've had experience with, it won't actually melt until about 3000F. What it does when overheated is shrink and stiffen up. Which makes sense in a way--the fibers are behaving the same way that clay particles do when sintered.
    The process of turning stumbling blocks into stepping stones can at times require the use of a large sledgehammer.

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    Senior Member 4cylndrfury's Avatar
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    Anon, I have heard a lot of mention of foam as a component in a insulating layer in the past. Im not opposed to using it, I have a bunch of expanded foam packing material I can grind down. But Im really surprised that at Iron temps the foam doesnt break down and excape as gas or something. I know dense castable becomes pretty watertight on its own once cured, but I still would think the foam burning out would cause an issue. Is the point that the foam burn out leaves dead space in the refractory and therefore insulates better? What am I missing?

    Also, as far as the ceramic shrinking, Im hoping that it will be minimized if I do reach crazy high temps since its already compressed a little. The closest thing I can relate the panel i received to is a drop ceiling tile...its kinda crumbly like a drop tile and feels like its about as dense (gauging from weight vs size). Do you think a 1/2" layer of 4:1 refractory to foam beads behind a 1/2" hotface of pure refractory (btw, the refreactory is 60% alumina) would be sufficient protection for the ceramic? Im really counting on it to do a majority of my insulation.

    Thanks again for everyones input.

  8. #8
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    Out gassing is exactly what it does. And the little pores in the hot face let out the gasses and you don't want to heat it very fast (The first time) for the same reason. What it leaves behind is holes in the stuff and those make for a much longer heat path to the outside and that is what insulation is all about.

  9. #9
    Administrator Site Admin Anon's Avatar
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    Quote Originally Posted by 4cylndrfury
    Is the point that the foam burn out leaves dead space in the refractory and therefore insulates better?
    Yes. Foam is a good choice for a burnable material because it doesn't produce much gas in comparison to other things (there's not actually much material to get rid of), it doesn't absorb water (which can mess with the refractory's binding ability), and it doesn't leave any significant residue (as opposed to sawdust, which will leave some amount of fluxing ash behind).

    You may not need any (thermal) protection for it at all. Point a torch at it for a while and see what it does. Mind the respiratory hazard.

    I'd go with at least 2" thick of the stuff, behind a 1/4"-ish hotface. Maybe more, because I can't tell how big that tank is.
    The process of turning stumbling blocks into stepping stones can at times require the use of a large sledgehammer.

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  10. #10
    hey 4cylinder, instead of a 5 gallon bucket of whatever you plan on using, why not use an old 20 pound propane tank, i have a bunch of old ones you can have

    i made an oil tank from one a few years back, it didnt turn out the best, i have had plans to make another one soon, this time i am gonna remove the valve and make a fitting to screw into the valve hole (3/4 inch pipe thread fitting) with a tube going down the middle so it is not to the bottom (so it wont suck up any dirt) with an air fitting so i can also pressurize the tank with no more than 20 PSI which will force the oil up thru the rube going into the bottom

    that may be my winter project this year, an oil burner of some kind, after seeing all the ideas some of you on here have been playing with i may try my hand at one again

    let me know if you want a tank, like i said free, i also have a bunch of those refrigerant tanks as well, they are just a bit smaller than a 20 pound propane tank


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