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Insulating A Converted Kiln


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#1 Claynut

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Posted 28 September 2010 - 01:20 PM

I have a old electric kiln that is only 2" thick and I have already purchased a gas conversion kit. It is an updraft kiln design. I would like to do reduction firing in it with slow cool downs. Can I put ceramic fiber on the outside of the kiln and then dry stack hard brick around the outside to insulate it? Would that be enough for slow cooling? I have about 900 hard brick from an old beehive kiln that I'm trying to find a use for...

#2 Deb Evans

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Posted 28 September 2010 - 03:30 PM

jack up the kiln w/ bricks. cause you'll need to build a chemney.
what ^ was the kiln rated for?
as long as your the only one using it - definetly wrap w/ fiber blanket-
I've found that students are hard on it
Sounds like your going to have some fun!
Firing to ^ 6r?



#3 Claynut

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Posted 28 September 2010 - 04:36 PM

jack up the kiln w/ bricks. cause you'll need to build a chemney.
what ^ was the kiln rated for?
as long as your the only one using it - definetly wrap w/ fiber blanket-
I've found that students are hard on it
Sounds like your going to have some fun!
Firing to ^ 6r?


I'll be firing to Cone 10, I used to fire to cone 6 in it but it was rated for cone 10. I plan to use natural gas. It has an extra ring on it that I thought about making a pully for so I could use it for Raku some of the time. It will be exclusively used by me but I've never fired a gas kiln myself so I am a little timid about it. If it is a 3 1/2 cubic foot kiln how tall should the chimney be?

#4 Username

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Posted 28 September 2010 - 04:54 PM

Why is a chimney needed?



#5 Claynut

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Posted 28 September 2010 - 05:06 PM

Why is a chimney needed?


that's a good question, I shouldn't need one for an updraft kiln should I?

#6 JBaymore

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Posted 28 September 2010 - 09:24 PM

Nope... no chimney for an updraft needed. However a short small "extension" from the exit flue port in the lid made of (light) IFB will help to even out the temperature at the very top of the chamber rather than just having a "hole in the lid". Doesn't have to be long..... 9" high is plenty. Same size XC as the hole in the top. I'd also recommend a half shelf located directly under the flue opening and above the top of the last shelf of work........ making sure that the space between that shelf and the bottom interior surface of the lid is adequate to match the XC of the flue opening in square inches of flow area.

And if you wrap fiber around the outside of the kiln without removing the metal jacket, you will bring the interface temperature of the point where the fiber is against the metal and the inner firebick layer up to a point that will quickly destroy the metal jacket. It was never designed to get that hot. Even if it is stainless. It will quickly rust out. The more you insulate it, the worse the problem. BUT.... if you remove the metal jacket on the firebrick that acts as the "tensioner" that compresses the insulating firebrick into istelf, the kiln structure will sort of "fall apart.

So insulating the exterior is not quite as simple as "wrapping" the kiln like you might a hot water heater in a house with pink fiberglass.

Insulating the floor and lit on the outside however is a snap.

And it you are working with RCF (fiber).... PLEASE check out the MSDS for that stuff to know well what you are working with BEFORE using it. And check out the European Union standards fior RCF online. An eye opener.


best,

......................john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#7 Deb Evans

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Posted 29 September 2010 - 04:16 PM

sorry
though you said you wanted down draft.

#8 Claynut

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Posted 29 September 2010 - 06:51 PM

Nope... no chimney for an updraft needed. However a short small "extension" from the exit flue port in the lid made of (light) IFB will help to even out the temperature at the very top of the chamber rather than just having a "hole in the lid". Doesn't have to be long..... 9" high is plenty. Same size XC as the hole in the top. I'd also recommend a half shelf located directly under the flue opening and above the top of the last shelf of work........ making sure that the space between that shelf and the bottom interior surface of the lid is adequate to match the XC of the flue opening in square inches of flow area.

And if you wrap fiber around the outside of the kiln without removing the metal jacket, you will bring the interface temperature of the point where the fiber is against the metal and the inner firebick layer up to a point that will quickly destroy the metal jacket. It was never designed to get that hot. Even if it is stainless. It will quickly rust out. The more you insulate it, the worse the problem. BUT.... if you remove the metal jacket on the firebrick that acts as the "tensioner" that compresses the insulating firebrick into istelf, the kiln structure will sort of "fall apart.

So insulating the exterior is not quite as simple as "wrapping" the kiln like you might a hot water heater in a house with pink fiberglass.

Insulating the floor and lit on the outside however is a snap.

And it you are working with RCF (fiber).... PLEASE check out the MSDS for that stuff to know well what you are working with BEFORE using it. And check out the European Union standards fior RCF online. An eye opener.


best,

......................john


Thank you for the response :). Now that you mention it I do remember reading archives on Clayart from others who have converted an electric kiln saying that the kiln won't last long. That must be why. I will check out the European Union standards before using the RCF, thank you. So should I not worry about the exterior of the kiln, just insulate the tope and the bottom?

#9 Claynut

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Posted 29 September 2010 - 06:52 PM

sorry
though you said you wanted down draft.


No worries, thank you for your help :)

#10 potterykiln

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Posted 30 September 2010 - 06:11 AM

Is it located inside or outside. I was not sure from your description.
Regards,

Frank Kiln
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