don. gauthier on sun 9 nov 97
------------------
I have been in the process of changing my updraft fiber kiln to a downdraft
configuration. I am slowly adjusting the kiln to fire evenly but cannot
tweak the burners, bagwall, damper to give me an even firing. When I fire
updrafts, which I have with good results over the years, I have followed
some simple guidelines. If the top was cooler I would cut back the air in
the gas/air mix. This would lengthen the flame and move the heat
concentration to the top of the kiln. Opening the damper slightly would
help draw the heat to the top also. If the bottom was cooler I would
reverse the process, increasing air to the gas/air mix, shortening the
flame and concentrating the heat at the bottom of the kiln. This simple
process served me well.
For a number of reasons, most of which I am beginning to regret, I made the
change to a downdraft. I cannot seem to use the air mix at the burners and
damper to redistribute the heat throughout the kiln. Can someone offer
guidelines for evening the temp. in a downdraft by these concepts. I have
tried various combinations but they seem to have no influence on the kiln.
Any advise would be greatly appreciated.
Don Gauthier
Baldwin City, Kansas
Grimmer on mon 10 nov 97
Don,
My experience with DD kilns has always been: damper in/bells closed
heats bottom, damper out/bells open heats top. To a point. Then the
flame can become so short that you heat the bottom again. Really
oxidizing, now though. Good for a bisque fire situation, though. Too little
primary air can put the flame tip into the chimney, where it's not helping
anyone.
steve grimmer
marion illinois
don. gauthier wrote:
>
> ----------------------------Original message----------------------------
> ------------------
> I have been in the process of changing my updraft fiber kiln to a downdraft
> configuration. I am slowly adjusting the kiln to fire evenly but cannot
> tweak the burners, bagwall, damper to give me an even firing. When I fire
> updrafts, which I have with good results over the years, I have followed
> some simple guidelines. If the top was cooler I would cut back the air in
> the gas/air mix. This would lengthen the flame and move the heat
> concentration to the top of the kiln. Opening the damper slightly would
> help draw the heat to the top also. If the bottom was cooler I would
> reverse the process, increasing air to the gas/air mix, shortening the
> flame and concentrating the heat at the bottom of the kiln. This simple
> process served me well.
>
> For a number of reasons, most of which I am beginning to regret, I made the
> change to a downdraft. I cannot seem to use the air mix at the burners and
> damper to redistribute the heat throughout the kiln. Can someone offer
> guidelines for evening the temp. in a downdraft by these concepts. I have
> tried various combinations but they seem to have no influence on the kiln.
> Any advise would be greatly appreciated.
>
> Don Gauthier
> Baldwin City, Kansas
Ray Carlton on mon 10 nov 97
how have you got it set up don ie burners through floor, how many, how high
is the bagwall etc these specs will help to track down the problem
At 11:21 09/11/97 EST, you wrote:
>----------------------------Original message----------------------------
>------------------
>I have been in the process of changing my updraft fiber kiln to a downdraft
>configuration. I am slowly adjusting the kiln to fire evenly but cannot
>tweak the burners, bagwall, damper to give me an even firing. When I fire
>updrafts, which I have with good results over the years, I have followed
>some simple guidelines. If the top was cooler I would cut back the air in
>the gas/air mix. This would lengthen the flame and move the heat
>concentration to the top of the kiln. Opening the damper slightly would
>help draw the heat to the top also. If the bottom was cooler I would
>reverse the process, increasing air to the gas/air mix, shortening the
>flame and concentrating the heat at the bottom of the kiln. This simple
>process served me well.
>
>For a number of reasons, most of which I am beginning to regret, I made the
>change to a downdraft. I cannot seem to use the air mix at the burners and
>damper to redistribute the heat throughout the kiln. Can someone offer
>guidelines for evening the temp. in a downdraft by these concepts. I have
>tried various combinations but they seem to have no influence on the kiln.
>Any advise would be greatly appreciated.
>
>Don Gauthier
>Baldwin City, Kansas
>
>
raycarlt@valylink.net.au
Ray Carlton
McMahons Creek Victoria Australia 3799
Ron Roy on mon 10 nov 97
Best advice I ever got about evening out the temperature in a kiln was/is -
direct flame to where you need more heat and/or reduction.
I have an adjustable flue running the length of my floor. If my kiln was
cold at the bottom front I adjusted the flue to be more open at the front
and drag more flame through that part.
If the top was cold I raised the bag walls.
I've had - well having one today - 725 firing in that kiln now and can't
remember having a flash in the last 30 years.
Once you get it figured out I think you will be better off with a down
draft - I suess this is a case of no pain, no gain.
>----------------------------Original message----------------------------
>------------------
>I have been in the process of changing my updraft fiber kiln to a downdraft
>configuration. I am slowly adjusting the kiln to fire evenly but cannot
>tweak the burners, bagwall, damper to give me an even firing. When I fire
>updrafts, which I have with good results over the years, I have followed
>some simple guidelines. If the top was cooler I would cut back the air in
>the gas/air mix. This would lengthen the flame and move the heat
>concentration to the top of the kiln. Opening the damper slightly would
>help draw the heat to the top also. If the bottom was cooler I would
>reverse the process, increasing air to the gas/air mix, shortening the
>flame and concentrating the heat at the bottom of the kiln. This simple
>process served me well.
>
>For a number of reasons, most of which I am beginning to regret, I made the
>change to a downdraft. I cannot seem to use the air mix at the burners and
>damper to redistribute the heat throughout the kiln. Can someone offer
>guidelines for evening the temp. in a downdraft by these concepts. I have
>tried various combinations but they seem to have no influence on the kiln.
>Any advise would be greatly appreciated.
>
>Don Gauthier
>Baldwin City, Kansas
Ron Roy
93 Pegasus Trail
Scarborough,Canada
M1G 3N8
Evenings, call 416 439 2621
Fax, 416 438 7849
Studio: 416-752-7862.
Email ronroy@astral.magic.ca
Home page http://digitalfire.com/education/people/ronroy.htm
WardBurner@aol.com on tue 11 nov 97
Don,
What worked with an updraft, doesn't always work with a downdraft. Instead of
fooling with the burners to change flame length, you need to do more bagwall
adjustment. If the top is too cool you need to tighten up/raise the bagwall.
If the topp is too hot, do the opposite. Think of the bag wall as rocks in a
stream of water. Place the "rocks" in places to divert the flow to where it's
needed.
One other problem is that updrafts are (or should be) a different height to
width ratio than downdrafts. Because of this, you may find it difficult to
have a real even firing. If you have further questions, feel free to give me
a call....
Marc Ward
Ward Burner Systems
PO Box 333
Dandridge, TN 37725
USA
423.397.2914 voice
423.397.1253 fax
wardburner@aol.com
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