Sylvia See on thu 19 aug 99
Hi all. I am in dire need of some help with the size of a flue on a 24cu.ft.
kiln I just am almost finished making. I spent 2 years making firebricks for
this puppy and now need to fire it to fire the roof bricks I am making
3'x1'x4inches. I have fired the darn thing 3 times now and I can't get it up
to mid fire temps before my 100 lb. bottles run out. I am sure I have the
chimney too large as I have reassembled each time trying to correct various
other mistakes. I have a shell of 2 rows of firebrick, with one layer of
fiberfax outside the firebricks to protect the outer shell of red house
bricks. I have 2 100 lb. bottles of propane, and am firing with 2 tiger
torches. The lasttime I assembled this I was very careful about making sure
all small holes etc were covered with fiberfax or bricks and that the roof
was lined well with fiberfax. I put one layer on the top row of firebricks,
and another layer on top of the red bricks and then spread 2 layers of
fiberfax across the entire roof. I have a piece of galvanized sheet metal
over the fiberfax. I need to use it this way until I get the roof bricks
fired so they will hold the fiberfax. To answer the question your dying to
ask, how did I suspend the fiber over the roof. First firing I tried a sheet
of metal which melted at 1200 to 1500F. Today I tried it again with the wall
brackets for making shelf units. The ones that metal shelf brackets push
into. So far after 1400F they are still okay. I just need them to hold out
long enough to fire the bricks hard enough to not buckle in a higher firing.
I would like to be able to take this thing to cone 10 but will settle with
cone 6 if I have to. So far it is only 2 feet high but I plan to make it
higher. Right now I can get 2 rows of shelves lengthwise, 23" shelves, and
stack 3 rows high of medium sized pots, 2 rows if larger pieces. My problem
is getting it to temp. I am stuck at 14 or 1500F after 8 to 10 hours and
both propane bottles are empty after that time. Two firings and $152.00 for
propane and I haven't a clue what size I should make the hole at the bottom
for the chimney. Help!!! I made 2 flue openings, as I am a real greenhorn
with gas, and I thought after the first firing, when the flame started
backing out the burner port, that I had made the chimney too small and once
it was firing I couldn't change it. So, I remade the whole thing, and put in
double holes for the chimney. Then I could brick one from the outside and if
I needed more air, I could start by removing one brick at a time from the
outside while I was firing. Each one is about 4"x9". Also I have no idea
how high I should be making the bagwall. I think I am making the bagwall too
high and the chimney openings too big, but would sure appreciate some advice
here from the experts with propane. This will be a flattop, freestanding
hopefully. I hope to gas fire in our 5 nice days each summer, and fill the
puppy with sawdust for primitive in the winter. I'm up here in sunny
Alberta.
Thanks in advance.
Sylvia See Claresholm, Alberta Canada sylviac@telusplanet.net
Steve Dalton on fri 20 aug 99
Sylvia,
I was in your boat at one time as well. Go get a copy of Nils Lou book "The
Art of Firing," and read it through from end to end. You only need one
flue. In Nil's book the size is 7x4.5 in inches, if I remember right.
Second get a larger tank (250gallons). You'll save some money in buying it
bulk. Third you didn't mention how high you chimney is (12ft.-14ft I
presume)
If you're still getting flame coming from the ports after you make the
changes you might need to make the flue larger. But remember you're firing
green bricks though, it'll take some time.
You're first few firings are very testing, I went through six until I got it
right. Making changes here and there. Infact my kiln is a combination of
Nils Lou and Fred Olsen's theories. I had to expand the size of my flue to
get it up to ^10, but I plan to do some more changes before my next firing.
Steve Dalton
P.S. If you have a hard time finding the book, try Axner at www.axner.com
----------
> From: Sylvia See
> To: CLAYART@LSV.UKY.EDU
> Subject: flue size help Please
> Date: Thu, 19 Aug 1999 12:13:31 EDT
>
>----------------------------Original message----------------------------
>Hi all. I am in dire need of some help with the size of a flue on a
24cu.ft.
>kiln I just am almost finished making. I spent 2 years making firebricks
for
>this puppy and now need to fire it to fire the roof bricks I am making
>3'x1'x4inches. I have fired the darn thing 3 times now and I can't get it
up
>to mid fire temps before my 100 lb. bottles run out. I am sure I have the
>chimney too large as I have reassembled each time trying to correct various
>other mistakes. I have a shell of 2 rows of firebrick, with one layer of
>fiberfax outside the firebricks to protect the outer shell of red house
>bricks. I have 2 100 lb. bottles of propane, and am firing with 2 tiger
>torches. The lasttime I assembled this I was very careful about making sure
>all small holes etc were covered with fiberfax or bricks and that the roof
>was lined well with fiberfax. I put one layer on the top row of firebricks,
>and another layer on top of the red bricks and then spread 2 layers of
>fiberfax across the entire roof. I have a piece of galvanized sheet metal
>over the fiberfax. I need to use it this way until I get the roof bricks
>fired so they will hold the fiberfax. To answer the question your dying to
>ask, how did I suspend the fiber over the roof. First firing I tried a
sheet
>of metal which melted at 1200 to 1500F. Today I tried it again with the
wall
>brackets for making shelf units. The ones that metal shelf brackets push
>into. So far after 1400F they are still okay. I just need them to hold out
>long enough to fire the bricks hard enough to not buckle in a higher
firing.
>I would like to be able to take this thing to cone 10 but will settle with
>cone 6 if I have to. So far it is only 2 feet high but I plan to make it
>higher. Right now I can get 2 rows of shelves lengthwise, 23" shelves, and
>stack 3 rows high of medium sized pots, 2 rows if larger pieces. My problem
>is getting it to temp. I am stuck at 14 or 1500F after 8 to 10 hours and
>both propane bottles are empty after that time. Two firings and $152.00
for
>propane and I haven't a clue what size I should make the hole at the bottom
>for the chimney. Help!!! I made 2 flue openings, as I am a real greenhorn
>with gas, and I thought after the first firing, when the flame started
>backing out the burner port, that I had made the chimney too small and once
>it was firing I couldn't change it. So, I remade the whole thing, and put
in
>double holes for the chimney. Then I could brick one from the outside and
if
>I needed more air, I could start by removing one brick at a time from the
>outside while I was firing. Each one is about 4"x9". Also I have no idea
>how high I should be making the bagwall. I think I am making the bagwall
too
>high and the chimney openings too big, but would sure appreciate some
advice
>here from the experts with propane. This will be a flattop, freestanding
>hopefully. I hope to gas fire in our 5 nice days each summer, and fill the
>puppy with sawdust for primitive in the winter. I'm up here in sunny
>Alberta.
>Thanks in advance.
>Sylvia See Claresholm, Alberta Canada sylviac@telusplanet.net
Ray Aldridge on fri 20 aug 99
At 12:13 PM 8/19/99 EDT, you wrote:
>----------------------------Original message----------------------------
>Hi all. I am in dire need of some help with the size of a flue on a 24cu.ft.
>kiln I just am almost finished making. I spent 2 years making firebricks for
>this puppy and now need to fire it to fire the roof bricks I am making
>3'x1'x4inches. I have fired the darn thing 3 times now and I can't get it up
>to mid fire temps before my 100 lb. bottles run out.
I may be wrong, but a couple 100 lb. bottles of propane seems a small fuel
reserve for a kiln this size. I used to have a 16 cubic ft. hardbrick kiln
that could freeze a 500 gallon tank when the fuel was low.
Ray
Dorothy Weber on sat 21 aug 99
If you can't get your kiln up to mid range with 100 Gal. Propane tank you
need to check for air leaks into the kiln or change the oriface size of the
burners. You may want to check with Marc Ward on you input.
Tom Wirt on mon 23 aug 99
Subject: Re: flue size help Please
> ----------------------------Original message----------------------------
> Sylvia,
> I was in your boat at one time as well. Go get a copy of Nils Lou book
"The
> Art of Firing," and read it through from end to end. You only need one
> flue. In Nil's book the size is 7x4.5 in inches, if I remember right.
> Second get a larger tank (250gallons). You'll save some money in buying
it
> bulk. Third you didn't mention how high you chimney is (12ft.-14ft I
> presume)
> If you're still getting flame coming from the ports after you make the
Sylvia
Steve's notes are good. Also, we had trouble getting to c10 on our first
couple of test firings. (We're in a standard MFT (about 40 sq. ft.
stackable)). It uses the standard Nils Lou double venturi flue arrangement.
Our problem was the stack height. The initial stack was about 10
feet....I'd always heard that all you had to do with power burners was get
the stack outside. NOT SO. There is also a principal operating (discussed
in Nils' book) of a wave that forms in the flue gasses going up the stack.
If the top of the stack happens to be at a node in that wave, it's like
having a damper on the top of the stack.
Try lengthening the stack by 2 feet...It may turn the trick for you.
Tom Wirt
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