Bonnie Hotz on sun 12 feb 12
Hi,
I just joined tonight, but have been making pottery for awhile now. I rec=
=3D
ently=3D20
moved my 24 cf downdraft kiln - 6 burners, 3 on each side that come in fr=
=3D
om the=3D20
bottom. Since re-connecting and firing it (with propane) which is what I =
=3D
used to=3D20
use, the top is not heating up. I had a 3 cone difference. I was able to =
=3D
keep the=3D20
bottom from getting hotter for 4 hours by lowering the gas pressure a lit=
=3D
tle and=3D20
opening the damper, but the top only climbed a little bit in those 4 hour=
=3D
s so I shut=3D20
it down to make corrections. Since the firing I've added some fiber and f=
=3D
ire bricks=3D20
to the roof of the kiln (hopefully to keep heat in) and I'll block the fr=
=3D
ont of the bag=3D20
walls to try to get the heat to rise. My kiln shelves are usually flush =
=3D
with the back=3D20
of the kiln, should I try to leave a little gap back there - would that =
=3D
help airflow=3D20
at all - or should I keep them flush?=3D20
Bonnie
Eric Ciup on mon 13 feb 12
We probably need more information to be able to give meaningful advice.
When you moved your kiln did it move in one piece or did you dismantle
it and rebuild it. Is the line pressure of the propane the same as at
your original site. Is the chimney the same height and diameter. Chances
are adding insulation won't help, it sounds as if you don't have enough
gas going into the kiln either from lower gas pressure, blocked orifices
or draft issues.
Eric
On 2/12/2012 10:34 PM, Bonnie Hotz wrote:
> Hi,
> I just joined tonight, but have been making pottery for awhile now. I rec=
ently
> moved my 24 cf downdraft kiln - 6 burners, 3 on each side that come in fr=
om the
> bottom. Since re-connecting and firing it (with propane) which is what I =
used to
> use, the top is not heating up. I had a 3 cone difference. I was able to =
keep the
> bottom from getting hotter for 4 hours by lowering the gas pressure a lit=
tle and
> opening the damper, but the top only climbed a little bit in those 4 hour=
s so I shut
> it down to make corrections. Since the firing I've added some fiber and f=
ire bricks
> to the roof of the kiln (hopefully to keep heat in) and I'll block the fr=
ont of the bag
> walls to try to get the heat to rise. My kiln shelves are usually flush =
with the back
> of the kiln, should I try to leave a little gap back there - would that =
help airflow
> at all - or should I keep them flush?
>
> Bonnie
douglas fur on mon 13 feb 12
More info please
Did you change anything in the set up ? as eric says gas supply or altitude
or change in length or diameter of gas line from tank to kiln or even flies
attracted to the smell of propane who crawled into the dissassembled
burners, died and clogged the orifices? (really. I've seen it)
My first thought was "too much draft is sucking the flame out before it can
rise to the top" but thats pure speculation based on no facts.
drb
Seola Creek
On Mon, Feb 13, 2012 at 6:41 AM, Eric Ciup wrote:
> We probably need more information to be able to give meaningful advice.
> When you moved your kiln did it move in one piece or did you dismantle
> it and rebuild it. Is the line pressure of the propane the same as at
> your original site. Is the chimney the same height and diameter. Chances
> are adding insulation won't help, it sounds as if you don't have enough
> gas going into the kiln either from lower gas pressure, blocked orifices
> or draft issues.
>
> Eric
>
>
> On 2/12/2012 10:34 PM, Bonnie Hotz wrote:
>
>> Hi,
>> I just joined tonight, but have been making pottery for awhile now. I
>> recently
>> moved my 24 cf downdraft kiln - 6 burners, 3 on each side that come in
>> from the
>> bottom. Since re-connecting and firing it (with propane) which is what I
>> used to
>> use, the top is not heating up. I had a 3 cone difference. I was able to
>> keep the
>> bottom from getting hotter for 4 hours by lowering the gas pressure a
>> little and
>> opening the damper, but the top only climbed a little bit in those 4
>> hours so I shut
>> it down to make corrections. Since the firing I've added some fiber and
>> fire bricks
>> to the roof of the kiln (hopefully to keep heat in) and I'll block the
>> front of the bag
>> walls to try to get the heat to rise. My kiln shelves are usually flush
>> with the back
>> of the kiln, should I try to leave a little gap back there - would that
>> help airflow
>> at all - or should I keep them flush?
>>
>> Bonnie
>>
>
William & Susan Schran User on tue 14 feb 12
On 2/12/12 10:34 PM, "Bonnie Hotz" wrote:
> I just joined tonight, but have been making pottery for awhile now. I rec=
ently
> moved my 24 cf downdraft kiln - 6 burners, 3 on each side that come in fr=
om
> the bottom. Since re-connecting and firing it (with propane) which is wh=
at I
>used to use, the top is not heating up. I had a 3 cone difference. I was =
able
to keep the bottom from getting hotter for 4 hours by lowering the gas pre=
ssure
a little and opening the damper, but the top only climbed a little bit in =
those
4 hours so I shut it down to make corrections. Since the firing I've added =
some
fiber and fire bricks to the roof of the kiln (hopefully to keep heat in) a=
nd
I'll block the front of the bag walls to try to get the heat to rise. My k=
iln
shelves are usually flush with the back of the kiln, should I try to leave =
a
little gap back there - would that help airflow at all - or should I keep =
them
flush?
Bonnie,
You write that you moved this kiln. Had you fired it previously at it's
other location? You write the burners come in from the bottom - are the
burner ports in the bottom of the wall, burner horizontal or ports in the
floor, burners vertical? If floor/vertical, why do you have bag walls? How
about the stack/flue? Same height as at previous location? How do you have
the primary air disks set on the burners?
You wrote lowering gas pressure (good), but if you want heat to go to the
top you'll need to close the damper a bit, not open it. Opening the damper
will pull heat to the bottom.
How you load the kiln can affect evenness of firing. Packing top with more
pots & furniture can make it harder to heat.
You wrote heat climb was very little in couple hours time. Was the same siz=
e
gas line installed as was at the previous location? Smaller diameter line
can cause issues at higher temperatures. Is there a regulator along the mai=
n
gas line?
Leaving a gap between shelves and back wall will help heat flow in the kiln=
.
Did you build this kiln or is it commercially built?
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Neil Estrick on wed 15 feb 12
There are a lot of possibilities, but I'd start with the bag wall height =
=3D
and/or flue=3D20
draft. My general rule when firing a kiln is to find a balance where you =
=3D
have=3D20
enough gas to get the heat, enough air for the amount of reduction you ne=
=3D
ed,=3D20
and the damper set to where you just have at least a touch of back pressu=
=3D
re out=3D20
of the bottom spy hole. If you can't achieve evenness with these settings=
=3D
, then=3D20
the bag wall or flue opening may need adjusting. Sometimes no matter what=
=3D
you=3D20
do with gas and air and flue, it won't even out. Adjustments must be made=
=3D
to the=3D20
physical kiln at that point.
Even if you fired this kiln at a different location with no problem, thin=
=3D
gs change=3D20
when a kiln moves. There are a lot of forces at work that we do not see! =
=3D
Even=3D20
identical kilns sitting side by side will not fire the same. Different ga=
=3D
s pipes,=3D20
different air, planet alignment, black holes, the Force, etc......
Ingeborg Foco on thu 16 feb 12
While what Neil is suggestion is perhaps a good way to start, I don't
agree. Messing with the bag walls can make dramatic changes and create
more problems. I also don't agree with the general thinking that a moved
kiln will/can operate differently in the new location. Logically, if it is
reassembled in the same manner, same plumbing etc it should run the same
way. There are variations of things such as climate, elevation and so
forth that can have an impact, but that's really all..
I went thru a similar experience and had problems for a long time. Many
people on this list generously gave their time to help me solve the
problem. I went thru the same thing and fooled with the bag walls, the
chimney height, the shelf placement etc etc. None of it helped and much
of it made it worse.
One person asked if I had cleaned the burners and of course I had. I clean
them regularly. Finally I came up with the idea of cleaning the tips with
tip cleaners not just some brush. . So I bought tip cleaners and
thoroughly cleaned the tips (each little individual orifice) You can
purchase tip cleaners at your local welding store or on line.
After I did this cleaning, I put the bag walls back to their original
position and fired the kiln It is even top to bottom like it used to
before the move and before all of the fiddling around. This new location
is lower in elevation and the climate is totally different and yet after
this cleaning the tips, the kiln runs just like it did in the old location.
My personal experience would say, don't mess with all of the stuff changing
things that can dramatically make a difference and not necessarily for the
better. First make sure you assembled it correctly and all of the piping
is the same. then try cleaning the tips and see what happens. If that
doesn't work, proceed slowly look to see if you can figure out where to go
next. Sometimes the simplest way is the best way.
Good luck. I know how frustrating this can be I have been there.
Sincerely,
Ingeborg
http://www.thepottersworkshop.com
> There are a lot of possibilities, but I'd start with the bag wall height
> and/or flue
> draft. My general rule when firing a kiln is to find a balance where you
> have
> enough gas to get the heat, enough air for the amount of reduction you
> need,
> and the damper set to where you just have at least a touch of back
> pressure out
> of the bottom spy hole. If you can't achieve evenness with these settings=
,
> then
> the bag wall or flue opening may need adjusting. Sometimes no matter what
> you
> do with gas and air and flue, it won't even out. Adjustments must be made
> to the
> physical kiln at that point.
>
>
--
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