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Re: Homemade refractory insulation

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  • mphillipps2
    I picked up some refractory cement at Home Depot; other hardware stores may carry it. It costs about $15/gal. rated 2000 deg.F (~900 deg.C). Claims to seal
    Message 1 of 17 , Feb 1, 2006
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      I picked up some refractory cement at Home Depot; other hardware
      stores may carry it. It costs about $15/gal. rated 2000 deg.F (~900
      deg.C). Claims to seal holes and joints. Alternative to welding?
      Seems like a great way to increase efficiency by reducing sidewall
      conductivity of steel. Ceramic cookstoves have significantly higher
      efficiency than uninsulated metal stoves (Sci Am). One website also
      suggested filling the cement with sawdust. I haven't tested it yet.

      MP
    • doug
      There is a product called Plicast 36 it is rated at 3100 degrees, comes dry in 50 pound bags. Doug
      Message 2 of 17 , Feb 3, 2006
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        There is a product called Plicast 36 it is rated at 3100 degrees, comes dry
        in 50 pound bags.

        Doug
      • mphillipps2
        In a very general sense, refractory cement seems to be very similar to other cements, like portland cement; you just add water, and any other ingredients you
        Message 3 of 17 , Feb 3, 2006
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          In a very general sense, refractory cement seems to be very similar to
          other cements, like portland cement; you just add water, and any other
          ingredients you want, then mix it, mold it, shoot it through a gun
          (like "gunite" or "shotcrete"), or whatever.

          "Plicast" appears to be one type of "castable refractory cement".
          Anyone know what material properties are associated with the
          "castable" designation?

          There seem to be lots of types of refractory cement products. The
          differences seem to depend on which tradeoffs are taken, between:
          cost, availability, max operating temp, adhesive qualities, tensile &
          compressive strength, etc.

          The chemistry is tremendously complicated, but basically, unlike
          portland cement, it seems that refractory cement doesn't "hydrate" and
          bond to water. Rather, when heated, the water is released more
          gracefully without cracking the cement and destroying the structure.
          The thermal curing process is reminiscent of the pre-firing
          preparation of ceramics, where a long, slow heat is applied to slowly
          drive off the water.

          Oh, by the way, insulating value of a material depends on the thermal
          conductivities of it's components. The thermal conductivity of
          cement, is a fraction of that of steel. But all solids have MUCH
          higher conductivity than gases, so the greater insulating effect is
          actually due to the little pockets of trapped air or gases and the
          resulting high-porosity, low-density material.

          So for example, if you want a higher insulating value and you can
          afford to sacrifice strength, you might consider adding a material
          like vermiculite or sawdust, as apposed to pearlite, since when it's
          heated , the additive will (presumably) change state and leave a
          little insulating pocket of gases.

          -MP


          --- In WoodGas@yahoogroups.com, "doug" <doug@...> wrote:
          >
          > There is a product called Plicast 36 it is rated at 3100 degrees,
          comes dry
          > in 50 pound bags.
          >
          > Doug
          >
        • ROBIN DUMPLETON
          It means that it can be cast like cement or concrete, you can cast it into complicated shapes. One thing that is difficult is reinforcing it as it has a very
          Message 4 of 17 , Feb 3, 2006
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            It means that it can be cast like cement or concrete, you can cast it into complicated shapes. One thing that is difficult is reinforcing it as it has a very different thermal expansion to steel rebar. Vermiculite is used extensively as has been pointed out
            One way that it can be supported until it dries is by the use of expanded polystyrene foam block, which can be burnt out easily and is far easier to remove than a timber former. The EPS can be easily cut with a hot wire cutter or some sign makers have machines which will cut the EPS by cnc. I know that people are not really happy using petro chemicals but 95% of EPS is air and it can be recycled relatively simply.
            I just think that it is a great product maybe others feel different, but since my son is in the EPS business I have come to appreciate it's value and flexibility.

            Robin

            mphillipps2 <mphillipps2@...> wrote:
            In a very general sense, refractory cement seems to be very similar to
            other cements, like portland cement; you just add water, and any other
            ingredients you want, then mix it, mold it, shoot it through a gun
            (like "gunite" or "shotcrete"), or whatever.

            "Plicast" appears to be one type of "castable refractory cement".
            Anyone know what material properties are associated with the
            "castable" designation?

            There seem to be lots of types of refractory cement products. The
            differences seem to depend on which tradeoffs are taken, between:
            cost, availability, max operating temp, adhesive qualities, tensile &
            compressive strength, etc.

            The chemistry is tremendously complicated, but basically, unlike
            portland cement, it seems that refractory cement doesn't "hydrate" and
            bond to water. Rather, when heated, the water is released more
            gracefully without cracking the cement and destroying the structure.
            The thermal curing process is reminiscent of the pre-firing
            preparation of ceramics, where a long, slow heat is applied to slowly
            drive off the water.

            Oh, by the way, insulating value of a material depends on the thermal
            conductivities of it's components. The thermal conductivity of
            cement, is a fraction of that of steel. But all solids have MUCH
            higher conductivity than gases, so the greater insulating effect is
            actually due to the little pockets of trapped air or gases and the
            resulting high-porosity, low-density material.

            So for example, if you want a higher insulating value and you can
            afford to sacrifice strength, you might consider adding a material
            like vermiculite or sawdust, as apposed to pearlite, since when it's
            heated , the additive will (presumably) change state and leave a
            little insulating pocket of gases.

            -MP


            --- In WoodGas@yahoogroups.com, "doug" <doug@...> wrote:
            >
            > There is a product called Plicast 36 it is rated at 3100 degrees,
            comes dry
            > in 50 pound bags.
            >
            > Doug
            >





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          • William Carr
            ... I ve never heard of a foam made with air. In my experience the blowing gas is usually pentane. I nearly passed out from inhaling the smoke from a hot
            Message 5 of 17 , Feb 3, 2006
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              On Feb 3, 2006, at 2:00 PM, ROBIN DUMPLETON wrote:

              > I know that people are not really happy using petro chemicals but
              > 95% of EPS is air and it can be recycled relatively simply.

              I've never heard of a foam made with air. In my experience the
              'blowing gas' is usually pentane.

              I nearly passed out from inhaling the smoke from a hot wire cutter
              slicing expanded foam and was shaky for 24 hours after that.

              [Non-text portions of this message have been removed]
            • banditknight@aol.com
              So, is there anyone here that has used refractory cement as an insulation in making the pyrolisi chamber a wood gas generator? I read an aussie site that said
              Message 6 of 17 , Feb 3, 2006
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                So, is there anyone here that has used refractory cement as an insulation in
                making the pyrolisi chamber a wood gas generator?

                I read an aussie site that said they did and it cracked and failed rather
                quickly.
                I can't find the link right now though.


                [Non-text portions of this message have been removed]
              • hillmannglass
                I have used it to in a forge for melting aluminum. I used it for mortor between bricks and it didnt crack but i let it dry for over six months before firing it
                Message 7 of 17 , Feb 3, 2006
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                  I have used it to in a forge for melting aluminum. I used it for
                  mortor between bricks and it didnt crack but i let it dry for over
                  six months before firing it and when i did light it i didnt warm it
                  up all at once i lit a small fire with out forced air and slowly
                  opned the damper till it was fully open it took about two hours to
                  before i opened it all the way.


                  --- In WoodGas@yahoogroups.com, banditknight@... wrote:
                  >
                  > So, is there anyone here that has used refractory cement as an
                  insulation in
                  > making the pyrolisi chamber a wood gas generator?
                  >
                  > I read an aussie site that said they did and it cracked and failed
                  rather
                  > quickly.
                  > I can't find the link right now though.
                  >
                  >
                  > [Non-text portions of this message have been removed]
                  >
                • mphillipps2
                  I would expect that most types of cement or concrete could be casted to some extent. Maybe it would have been more to my point to ask: Is there such a thing
                  Message 8 of 17 , Feb 3, 2006
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                    I would expect that most types of cement or concrete could be casted
                    to some extent. Maybe it would have been more to my point to ask: Is
                    there such a thing as a non-castable cement?

                    Perhaps the mold could be removed more easily buy using a mold release
                    agent; it would probably be quicker and easier, plus the mold isn't
                    destroyed in the process, so it can be reused or "recycled".

                    The numbers I found say that the thermal expansion (CTE) of refractory
                    cement is matched by both stainless steel and copper (data and sources
                    below). These might be suitable materials for reinforcement in a
                    cement composite.

                    IIRC, EPS is filled with something other than air, and to some extent,
                    that may be part of the environmental concern. FYI, EPS/PS is also
                    one of the least recyclable plastics. Other than that, I agree it's a
                    great material.

                    I'm reminded of this irrelavent anecdote: I once saw a positive mold
                    made with EPS, then used to make a negative mold in cement. Then a
                    casting of molten lead was poured, and the lead "melted" away the EPS.
                    It worked fairly well, although there seemed to be some voids where
                    the liquid EPS had pooled. Given that the casting material (lead) is
                    a soft metal, there was some question about the structural integrity
                    of the casting. Anyway, the casting was drilled and coated to make a
                    sailboat keel, and it worked out okay in the end.

                    -MP
                    -------------------------

                    CTE
                    ---
                    steel: 7.7-9.2 CTE linear @ 500 degC (ppm/deg.F) http://www.matweb.com/

                    copper: 11.2 CTE linear @ 500 degC (ppm/deg.F) http://www.matweb.com/

                    stainless steel: 9.6-10.8 CTE linear @ 500 degC (ppm/deg.F)
                    http://www.matweb.com/

                    Aluminum: 15.2 CTE linear @ 500 degC (ppm/deg.F) http://www.matweb.com/
                    --------
                    refractory cement: 10.9 (ppm/deg.F), omegabond ob-500,
                    http://www.omega.com/manuals/manualpdf/M1241.pdf
                  • banditknight@aol.com
                    Just make an exact mold to duplicate the part and make sacrificial bolds out of something easily destroyed, like a wood over or outer mold, used to hold the
                    Message 9 of 17 , Feb 3, 2006
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                      Just make an exact mold to duplicate the part and make sacrificial bolds out
                      of something easily destroyed, like a wood over or outer mold, used to hold
                      the inner mold made of something like, perhaps a thick paper mache (spelling?)
                      packed tightly.
                      When you cast the part, remove the wood over/outer mold and just torch the
                      paper.


                      In a message dated 2/3/06 10:23:36 PM, mphillipps2@... writes:


                      Perhaps the mold could be removed more easily buy using a mold release
                      agent; it would probably be quicker and easier, plus the mold isn't
                      destroyed in the process, so it can be reused or "recycled".




                      [Non-text portions of this message have been removed]
                    • jackf
                      Yep, be warned, have plenty ventilation when burning acrylics or any other kind of plastics, foam or not. regards, Jack F ============================== Police
                      Message 10 of 17 , Feb 4, 2006
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                        Yep, be warned, have plenty ventilation when burning acrylics
                        or any other kind of plastics, foam or not. regards, Jack F
                        ==============================
                        Police wear handguns because they are
                        a practical means of self defense.
                        <http://www.gunsmith.fuselier.com> in East Texas

                        From: William Carr <Jkirk3279@...>
                        To: WoodGas@yahoogroups.com
                        Date: Friday, February 3, 2006, 1:30:04 PM
                        Subject: [WoodGas] Re: Homemade refractory insulation

                        On Feb 3, 2006, at 2:00 PM, ROBIN DUMPLETON wrote:

                        > I know that people are not really happy using petro chemicals but
                        > 95% of EPS is air and it can be recycled relatively simply.

                        I've never heard of a foam made with air. In my experience the
                        'blowing gas' is usually pentane.

                        I nearly passed out from inhaling the smoke from a hot wire cutter
                        slicing expanded foam and was shaky for 24 hours after that.
                      • jackf
                        It should not fail. A good refractory cement will hold in a forge at temperatures high enough to melt steel. Perhaps what they used was not a good mixture,
                        Message 11 of 17 , Feb 4, 2006
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                          It should not fail. A good refractory cement will hold in
                          a forge at temperatures high enough to melt steel. Perhaps
                          what they used was not a good mixture, it was not baked properly
                          to dry it, or was not installed correctly.
                          regards, Jack F
                          ==============================
                          Police wear handguns because they are
                          a practical means of self defense.
                          <http://www.gunsmith.fuselier.com> in East Texas

                          From: banditknight@... <banditknight@...>
                          To: WoodGas@yahoogroups.com
                          Date: Friday, February 3, 2006, 3:01:14 PM
                          Subject: [WoodGas] Re: Homemade refractory insulation
                          So, is there anyone here that has used refractory cement as an insulation in
                          making the pyrolisi chamber a wood gas generator?

                          I read an aussie site that said they did and it cracked and failed rather
                          quickly.
                          I can't find the link right now though.
                        • mphillipps2
                          Some manufacturers of refractory cements supply datasheets that have a recommended heating profile (temperature vs. time). This process could be monitored
                          Message 12 of 17 , Feb 4, 2006
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                            Some manufacturers of refractory cements supply datasheets that have a
                            recommended heating profile (temperature vs. time). This process
                            could be monitored with a simple timer and an oven thermometer which
                            would only cost a few bucks.

                            Perhaps one could dry the cement in an oven of some type, like a
                            woodgas "dutch oven", an old toaster oven, or a kitchen oven. Can
                            anyone confirm or deny the safety of using a kitchen oven for this?
                            I'm not sure about the toxicity, but you should be okay as long as you
                            don't eat the stuff or breathe the dust. Again, it's wise to read the
                            entire datasheet.

                            -MP
                          • William Carr
                            ... They had used that table for the hot-wire cutter for years. I worked at the station next to it for over a week until something changed... and the smoke
                            Message 13 of 17 , Feb 4, 2006
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                              On Feb 4, 2006, at 7:19 AM, jackf wrote:

                              > Yep, be warned, have plenty ventilation when burning acrylics
                              > or any other kind of plastics, foam or not. regards, Jack F

                              They had used that table for the hot-wire cutter for years. I
                              worked at the station next to it for over a week until something
                              changed... and the smoke almost got me.

                              Well, I had to quit at noon and go home. My lungs were clogged with
                              the smoke. Next day, I was shaky until lunch, so that's 24 hours.

                              My supervisor said "if it's bothering you, it can't be good for the
                              rest of us either", and decided to move the cutting station to the
                              back room and do the cutting in front of the open door.

                              A happy ending. Except that he went on vacation a week later and
                              his replacement wasn't interested in common sense, or safety either.

                              A dimwit I worked with complained about having to carry that HEAVY
                              styrofoam another 100 feet !

                              I told the new guy I couldn't work next to that smoke, and when he
                              later ordered the cutter brought back into the front room I punched
                              out and quit.














                              [Non-text portions of this message have been removed]
                            • banditknight@aol.com
                              Get a blower and some flexible duct work (like that expandable plastic and wire dryer tube if they have it bigger) and have it blow the smoke in his direction!
                              Message 14 of 17 , Feb 5, 2006
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                                Get a blower and some flexible duct work (like that expandable plastic and
                                wire dryer tube if they have it bigger) and have it blow the smoke in his
                                direction!


                                [Non-text portions of this message have been removed]
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