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kiln stack height, an observation

updated sat 15 aug 98

 

William Brouillard on fri 14 aug 98

kiln stacks, an irrelevant observation



Years ago I was helping with the construction of a kiln.

Since it was going to be a student fired kiln and all of the

burners were located in the back of the kiln, I suggested

that we use some soft brick to insulate the bottom of the

stack. The idea was to make the outside surface of the

hard brick stack cooler at the base to avoid accidental

burns in the cramped quarters around the kiln controls. I

used some salvaged K-23s from the previous construction

and added 4.5 inches of insulation to bottom of the stack .

I insulated to a height of about three feet or just past the

damper and burners. It kept that area cooler and reduced

the risk of burns.



The additional layer of insulation also changed the draft of

the kiln. Kiln draft, As I understand it, is dependent on

the temperature difference between the top and bottom of

the stack. The greater that difference, the greater the draft.

In general terms the higher the stack the greater the

difference in temperature between the top and the bottom

of the stack. The volume of the flue and stack must be

adequate to the size and type of the kiln and the interior

surface of the stack can affect the amount of drag or loss

of velocity of the gasses moving though it.



The insulated stack kept the bottom of the stack hotter

than before and the draw was greater. The better draw

allowed us to use a shorter stack and perhaps we could

have used a smaller flue.



The use of forced air burners makes the height of the

stack a question of getting the exhaust out of the building

or past the roof line. Since the burners act force the

exhaust out of the kiln stack height can be reduced.

Atmospheric burners require greater stack height and

sometimes greater volume as well.


--
william brouillard
1011 literary road
cleveland,oh.44113
ch151@cleveland.freenet.edu