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
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