[Clayart] Kiln Chimney extension of Metal

jonathan byler jebyler2 at gmail.com
Mon Jul 10 17:50:44 EDT 2017

if you add a plenum that pulls in cool ambient air and mixes with the flue gasses above the height of the brick chimney, you can use relatively low grade metal above that.  we were required to use special, very expensive triple wall stainless steel insulated flue pipe, because of fire codes and such here.  I wouldn’t worry about it so much if the kiln is in a separate shed away from other structures, and if the heat radiating from the metal chimney isn’t going to make it unbearably hot around the kiln.  you may need an insulated section of pipe where it passes through whatever roof is above the kiln.

I measured temperatures in our exhaust plenum, and they were somewhere between 600-700F at the hottest part of our firing.  There is a significant amount of cool air mixing with the flue gases because of this, making it much less detrimental to the metal flue material.  If this is a natural draught kiln using venturi burners, you may not be able to use this type of setup, since you will be relying on the chimney/flue height to make the draught to pull the hot gases through the kiln.  if the design uses natural draught, you will want a tight and insulated chimney to keep the draught proper for the height and chimney cross section calculated in the initial design.  Regular house brick may not be able to take the heat of the exhaust gasses, and may not hold up to the action of the soda on the bricks.  Whatever you do, be prepared to modify it later if it doesn’t prove satisfactory when actually fired.

> On Jul 4, 2017, at 8:09 PM, Vince Pitelka <vpitelka at DTCCOM.NET> wrote:
> Hi Helen - 
> Above the top of the kiln on both our salt and soda kiln we use ordinary galvanized steel corrugated culvert pipe for the chimney extension.  We probably get six or eight years out of a piece of pipe on the salt kiln, and ten or more on the soda kiln.
> - Vince
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka at dtccom.net  
> sites.tntech.edu/wpitelka/
> -----Original Message-----
> From: Clayart [mailto:clayart-bounces at lists.clayartworld.com] On Behalf Of Helen Stone
> Sent: Tuesday, July 4, 2017 7:59 AM
> To: Clayart international pottery discussion forum <clayart at lists.clayartworld.com>
> Subject: [Clayart] Kiln Chimney extension of Metal
> Hi folks, on my new soda kiln the chimney is made of dense firebrick up to above the firebox, then made of IFB up to the arch.  Above the arch |I would like to use either a metal piece or use regular house building red
> bricks.   If I use the metal extension, do I have to line it with
> insulating material?  For me it is not a viable option as only ceramic fibre would be available here in Ecuador.  Any advice would be appreciated.\
> Helen at Rio Yambala, southern Ecuador
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