material for external walls, electric furnace

[Terri Sigler]

I am building a freestanding electric furnace. Does anyone have favorable experience with TR-19 from Thermal ceramics? Is this a viable candidate for the external walls of my electric furnace? Do I need to paint it with a ridigizer after installation? Are there other materials that may be better suited for this purpose?


Thanks in advance,
Terri

[Pete VanderLaan]

To comment on that you would have to say what the inner walls are to be made of Terry, as well as thicknesses of those walls.

Further, if it is a wire furnace, it will be run at much colder temps than a moly or an SiC furnace would run at. What are you building specifically?

Rigidizer is really rarely used on the outsides of a furnace. I think the presumption is that the outer material is already rigid.

[Terri Sigler]

Thanks Pete. I am building a SiC furnace. My inner walls are one round of IFB K26, then K23, followed by a 4” thick outer wall of a material to be determined, perhaps this TR-19 that I read about on Thermal Ceramics’ product specification website.

Thanks,
Terri

[Jeff Thompson]

I would use 1/8" thick sheet metal for the exterior of the furnace, then pack fiber blanket into the 4" gap between the 23's and the metal skin. Do you have a reference book such as Glassnotes?

[Terri Sigler]

Yes, I am using Glassnotes as a reference in addition to Mark Lauckner’s DVD. While searching for a fiberboard compatible to that which Mark used, I stumbled on this TR-19. I wanted to make sure the TR-19 is an appropriate product and that I protect myself against potential floating elements found in vermiculite products.

Thanks,
Terri

[Garner Britt]

I'm not sure what Mark uses but TR-19 is Thermal ceramics version of Insblock 19 from Harbison Walker. Great insulation value for the price. The binder that holds it together burns off at 500-600 F and stinks. After the binder burns off it is somewhat fragile so a sheet metal shell would be advised.

You may also look into Skymol board. I've never used it but it sounds like the bee's knees.

garner

[Dave Bross]

Hardieboard (spelling?), it's a grey tile backer board. It's cellulose and concrete and makes a great outside skin for furnace or glory.

Find it at someplace like Lowes or Home Depot. This assumes a square or rectangular exterior.

You cut it by scratching it then snapping it, just like wallboard.

[Brian Gingras]

do not use hardibacker anywhere that will see heat, it does break down.

Used around my heating elements(there is heat there) it has since cracked and broken up. We used steel on the NY furnace becuase of this...it was a great experiment but in the long terms the heat takes it's toll.

[Glenn Randle]

I've always thought that the wavey corregated roofing metal was an attractive surface. That would work well, unless the galvanized coating is bad. Does anyone know the max safe temp for galvanized metal before it begin to make nasty fumes?

[Pete VanderLaan]

The mortared layer of 2600F brick ought to be enough. I would jettison the 2300F brick part and just use 8 " of fiber instead with a hardboard to hold it in. I would consider casting an inner liner on the G-26 hotface of a 95% alumina castable if I really wanted it to last forever. The 2600's will degrade.

[Terri Sigler]

Thanks for the tips. That should get me on my way!
Terri