John Krausser on thu 4 apr 02
Hi folks,
We're in the process of rebuilding the chimney on the wood-burning kiln at
the ceramics department at the University of Oregon. We need to move the
chimney back a few feet, making the kiln longer, and we need to almost
double the height of the chimney, to about 26'. We've done some initial
research, and we will use the great info in Olsen's book, "The Kiln Book,
Materials, Specs and Construction", but any insight on kiln/chimney
volumetric proportions, dimensions, design ideas, etc. would be greatly
appreciated. The kiln fires great right now, but the chimney needs
replacement. We don't want to loose the quality of our fires! Right now
there is a very readable flame column out the top during reduction. With
the increased height we're worried that we may loose that key indicator.
We're considering a secondary damper to allow fresh air in the chimney at
the base so it draws less from the firebox if we need to offset the
greater draw. Any ideas or experience with this wood chimney design will
be rewarded by the pot fairy (!) with beautiful glazes!
Thanks Alot
-John
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"What you drive has more impact on the environment than everything else
you do put together." - The Union of Concerned Scientists
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Hank Murrow on fri 5 apr 02
>Hi folks,
>We're in the process of rebuilding the chimney on the wood-burning kiln at
>the ceramics department at the University of Oregon. We need to move the
>chimney back a few feet, making the kiln longer, and we need to almost
>double the height of the chimney, to about 26'. We've done some initial
>research, and we will use the great info in Olsen's book, "The Kiln Book,
>Materials, Specs and Construction", but any insight on kiln/chimney
>volumetric proportions, dimensions, design ideas, etc. would be greatly
>appreciated. The kiln fires great right now, but the chimney needs
>replacement. We don't want to loose the quality of our fires! Right now
>there is a very readable flame column out the top during reduction. With
>the increased height we're worried that we may loose that key indicator.
>We're considering a secondary damper to allow fresh air in the chimney at
>the base so it draws less from the firebox if we need to offset the
>greater draw. Any ideas or experience with this wood chimney design will
>be rewarded by the pot fairy (!) with beautiful glazes!
>
>Thanks Alot
>-John
Dear Oregon Clay Folk;
Have you considered four-foot sections of steel pipe, with a
sonotube core and insulating castable between, perhaps with Rib-Tec
re-inforcement? Pretty easy to cast them with galleries to 'lock' the
sections in place. The sonotube core burns out in the first fire. Is
the height requirement for safety or fire regs?
Best, Hank in Eugene
vince pitelka on fri 5 apr 02
> The kiln fires great right now, but the chimney needs
> replacement. We don't want to loose the quality of our fires! Right now
> there is a very readable flame column out the top during reduction. With
> the increased height we're worried that we may loose that key indicator.
> We're considering a secondary damper to allow fresh air in the chimney at
> the base so it draws less from the firebox if we need to offset the
> greater draw.
John -
My first question - if the kiln fires perfectly, why are you extending the
chimney? 26 feet is a little extreme for just about any chimney. In my
experience, you could get by with a shorter chimney if you just build it
with a taper. You did not mention the size of your kiln. But just for an
example, if your kiln is 100 cubic feet and you want to make sure you have
all the draft you can possibly use, you could start out with a chimney 13.5
inches square inside, and about 8 feet up start tapering. This is not
difficult. Build the angle-iron frame first, with the desired taper, and
then cut and stack the bricks within the frame. Let the frame taper from
13.5 down to 9" square inside over about 8 feet, and then put about six feet
of 10 inch ID steel pipe on top of that.
Those engineers who designed the Industrial Revolution smoke stacks knew
what they were doing. Those stacks are always tapered. A stack always
draws better when velocity can increase as the gases move upwards. A
tapered stack accomplishes that. A stack without a taper is naturally a bit
sluggish. It will still work fine if built of adequate proportions, but a
tapered stack always works better.
And passive dampers (pluggable air ports in the chimney) are always a good
idea. Anyone who builds a chimney without them is foolish, because it is no
trouble to plug them, and yet they are there if you need them. A standard
adjustable damper causes strange air currents when it is partly closed, and
the if the damper is located right next to the ware chamber there is often a
"vacuum cleaner" effect in the immediate vicinity of the exit flue. A
passive damper slows down the exit of air from the ware chamber without
causing any strange air currents.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Steve Mills on sun 7 apr 02
John,
My last two production Gas Kilns had to have very tall chimneys due to
their situation (urban). With the first I installed an anti low-back
piece called a Shorn Baffler which directed any blow-back out sideways
from the stack and otherwise let in so much air it was effectively the
chimney top! reduction was by damper. With the second Kiln I dispensed
with a damper and baffler, and regulated the draw by removing bricks
from the chimney base (not as dodgy as it sounds). The system used in
the last one was by far the best as it gave me total control over all
aspects of draw and reduction. Both Kilns were naturally aspirated and
used mains gas. Incidentally I never had a blow-back in the first Kiln.
Steve
Bath
UK
In message , John Krausser writes
>Hi folks,
>We're in the process of rebuilding the chimney on the wood-burning kiln at
>the ceramics department at the University of Oregon. We need to move the
>chimney back a few feet, making the kiln longer, and we need to almost
>double the height of the chimney, to about 26'. We've done some initial
>research, and we will use the great info in Olsen's book, "The Kiln Book,
>Materials, Specs and Construction", but any insight on kiln/chimney
>volumetric proportions, dimensions, design ideas, etc. would be greatly
>appreciated. The kiln fires great right now, but the chimney needs
>replacement. We don't want to loose the quality of our fires! Right now
>there is a very readable flame column out the top during reduction. With
>the increased height we're worried that we may loose that key indicator.
>We're considering a secondary damper to allow fresh air in the chimney at
>the base so it draws less from the firebox if we need to offset the
>greater draw. Any ideas or experience with this wood chimney design will
>be rewarded by the pot fairy (!) with beautiful glazes!
>
>Thanks Alot
>-John
>
>-----------------------------------------------------------------------
>"What you drive has more impact on the environment than everything else
>you do put together." - The Union of Concerned Scientists
>-----------------------------------------------------------------------
--
Steve Mills
Bath
UK
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