Jennifer Boyer on wed 10 feb 99
Well,
I'm narrowing down some options for rebuilding my old gas IFB propane
kiln and need some opinions on whether I'm on the right track.
Bertha now:
36"wide and deep. 52" high. (interior dimensions)
9" thick IFB walls, 4.5" thick arch w/ 3 inches of misc. refractory
blanket.
12 foot HB chimney
4 B-4 Ransom venturi's side mounted. 4.5"/5" burner ports(90 sq in)
w/ max pressure 22 oz
9"/7/5" flue (67.5 sq in) (floor has flue trench)
19 inch high HB bag walls
HB floor
Atmosphere kept oxidizing( .04 on the oxyprobe) firing to ^10
My problem with this kiln is that the bottom and top back go to ^10
barely soft when the middle middle near the top of the bag walls is ^11
flat. My top middle and bottom cone packs in the door read ^10 down
top and bottom, ^11 soft middle. I figure I should try for a more even
kiln while I rebuild in a new building.
New Bertha: potential changes
40.5" wide and deep. 42" high
2 B-4 ransom venturi gas burners rear mounted w/ max pressure to 5 or 6
pounds
4.5"/7.5" burner ports(67.5 sq inches which would equal flue area)
13.5" high IFB bag walls
Gas pressure to 5 or 6 pounds.
IFB floor
The theory is to make the kiln size shorter to fix the kiln's
exaggerated height. Also using rear mounted burners would fix the
problem of a hot middle middle by not having flames going towards the
shelf stack. Does this make sense? Does anyone use venturi's on a rear
mounted burner system? Do you get an even firing? Temp is my main
concern, as I don't reduce. I'm not going for an MFT type system, but
will use a standard flue design. My recently bought shelves are 16"/20"
creating a 20"/32" stacking area. I'm changing the bag walls and floor
from HB to IFB to increase efficiency. The sq ft of the overall kiln
seems to be almost the same after the modifications.
What do you all think?
Jennifer,
--
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer jboyer@plainfield.bypass.com
Thistle Hill Pottery
Vermont USA
http://www.vermontcrafts.com/members/JenniBoy892.html
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
mathers, kevin R on thu 11 feb 99
I just finished a top loading kiln , 15 cu/ft, back fired with two forced
air burners , home made - N gas .Look in Bailey's catalog .. I copied their
layout. It fires absolutely even in temp and reduction . The lid is 4.5"
fiber , sandwiched on edge, hinged , S-steel support rods..easy to build. I
can open it with one hand . Only 4.5" IFB walls . Fires easily using 200K
BTU's total . You can get by with just two venturi burners ,especially since
you do not reduce. I would try it and change if you have trouble reaching
temp. I am way over powered with power burners . You could do (inside) 35" X
30" and save some energy using this unique bag wall lay out . Let me know if
you want more details .
Kevin
-----Original Message-----
From: Jennifer Boyer [mailto:jboyer@plainfield.bypass.com]
Sent: Wednesday, February 10, 1999 8:40 AM
To: CLAYART@LSV.UKY.EDU
Subject: gas kiln proportions
----------------------------Original message----------------------------
Well,
I'm narrowing down some options for rebuilding my old gas IFB propane
kiln and need some opinions on whether I'm on the right track.
Bertha now:
36"wide and deep. 52" high. (interior dimensions)
9" thick IFB walls, 4.5" thick arch w/ 3 inches of misc. refractory
blanket.
12 foot HB chimney
4 B-4 Ransom venturi's side mounted. 4.5"/5" burner ports(90 sq in)
w/ max pressure 22 oz
9"/7/5" flue (67.5 sq in) (floor has flue trench)
19 inch high HB bag walls
HB floor
Atmosphere kept oxidizing( .04 on the oxyprobe) firing to ^10
My problem with this kiln is that the bottom and top back go to ^10
barely soft when the middle middle near the top of the bag walls is ^11
flat. My top middle and bottom cone packs in the door read ^10 down
top and bottom, ^11 soft middle. I figure I should try for a more even
kiln while I rebuild in a new building.
New Bertha: potential changes
40.5" wide and deep. 42" high
2 B-4 ransom venturi gas burners rear mounted w/ max pressure to 5 or 6
pounds
4.5"/7.5" burner ports(67.5 sq inches which would equal flue area)
13.5" high IFB bag walls
Gas pressure to 5 or 6 pounds.
IFB floor
The theory is to make the kiln size shorter to fix the kiln's
exaggerated height. Also using rear mounted burners would fix the
problem of a hot middle middle by not having flames going towards the
shelf stack. Does this make sense? Does anyone use venturi's on a rear
mounted burner system? Do you get an even firing? Temp is my main
concern, as I don't reduce. I'm not going for an MFT type system, but
will use a standard flue design. My recently bought shelves are 16"/20"
creating a 20"/32" stacking area. I'm changing the bag walls and floor
from HB to IFB to increase efficiency. The sq ft of the overall kiln
seems to be almost the same after the modifications.
What do you all think?
Jennifer,
--
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer jboyer@plainfield.bypass.com
Thistle Hill Pottery
Vermont USA
http://www.vermontcrafts.com/members/JenniBoy892.html
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Earl Brunner on thu 11 feb 99
I would elevate the kiln a little and place the burners under it with the
flame path directed *up*. With this configuration you may not even need a
bag wall. If you build it like the one pictured in Rhodes Kiln book page
214 with a flue along the bottom of the kiln, then you can control the draft
very well by covering parts of the horizontal flue. For example, you could
cover all of it except the front, directing the flame path that way, There
are all kinds of ways to fine tune this design, with a bag wall and openings
in the bag wall, etc. especially if you shoot the burners straight up.
Shooting them straight up, you may not need to lose your height.
Earl Brunner
Jennifer Boyer wrote:
> ----------------------------Original message----------------------------
> Well,
> I'm narrowing down some options for rebuilding my old gas IFB propane
> kiln and need some opinions on whether I'm on the right track.
>
> Bertha now:
> 36"wide and deep. 52" high. (interior dimensions)
> 9" thick IFB walls, 4.5" thick arch w/ 3 inches of misc. refractory
> blanket.
> 12 foot HB chimney
> 4 B-4 Ransom venturi's side mounted. 4.5"/5" burner ports(90 sq in)
> w/ max pressure 22 oz
> 9"/7/5" flue (67.5 sq in) (floor has flue trench)
> 19 inch high HB bag walls
> HB floor
> Atmosphere kept oxidizing( .04 on the oxyprobe) firing to ^10
>
> My problem with this kiln is that the bottom and top back go to ^10
> barely soft when the middle middle near the top of the bag walls is ^11
> flat. My top middle and bottom cone packs in the door read ^10 down
> top and bottom, ^11 soft middle. I figure I should try for a more even
> kiln while I rebuild in a new building.
>
> New Bertha: potential changes
> 40.5" wide and deep. 42" high
> 2 B-4 ransom venturi gas burners rear mounted w/ max pressure to 5 or 6
> pounds
> 4.5"/7.5" burner ports(67.5 sq inches which would equal flue area)
> 13.5" high IFB bag walls
> Gas pressure to 5 or 6 pounds.
> IFB floor
>
> The theory is to make the kiln size shorter to fix the kiln's
> exaggerated height. Also using rear mounted burners would fix the
> problem of a hot middle middle by not having flames going towards the
> shelf stack. Does this make sense? Does anyone use venturi's on a rear
> mounted burner system? Do you get an even firing? Temp is my main
> concern, as I don't reduce. I'm not going for an MFT type system, but
> will use a standard flue design. My recently bought shelves are 16"/20"
> creating a 20"/32" stacking area. I'm changing the bag walls and floor
> from HB to IFB to increase efficiency. The sq ft of the overall kiln
> seems to be almost the same after the modifications.
>
> What do you all think?
> Jennifer,
>
> --
> ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
> Jennifer Boyer jboyer@plainfield.bypass.com
> Thistle Hill Pottery
> Vermont USA
> http://www.vermontcrafts.com/members/JenniBoy892.html
> ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Vince Pitelka on thu 11 feb 99
>New Bertha: potential changes
>40.5" wide and deep. 42" high
>2 B-4 ransom venturi gas burners rear mounted w/ max pressure to 5 or 6
>pounds
>4.5"/7.5" burner ports(67.5 sq inches which would equal flue area)
>13.5" high IFB bag walls
>Gas pressure to 5 or 6 pounds.
>IFB floor
Jennifer -
I think you are on the right track. Downdraft kilns which are taller than
wide do not tend to fire evenly. Your new design sounds good. However, I
am a firm believer in burner ports just large enough to allow in adequate
secondary air. Any larger than that and you tend to get excess secondary
air, which will just slow down your firing. I like to make my burner ports
4.5" by 5" maximum, which should let in plenty of secondary air for those
burners.
I do not know if two of those Ransome B-4s will be adequate at 5 or 6 pounds
of pressure. Mark Ward can tell you. But you should be able to guess,
depending on how the four B-4s worked on the old kiln. Did it seem greatly
overpowered? Granted, the new kiln is smaller and better proportioned, but
you want to check this out thoroughly before proceeding. It would be a
shame if you had to bore two more burner ports and add the other two B-4s.
You can get away without any bag wall at all with the burners coming in from
the rear corners, but you should put a target brick half way forwards to
deflect the flame upwards, and when you place your first shelf, place it up
4.5 inches high, right up against the back wall of the kiln, above the flue
opening, and place 2800 degree IFBs or hardbricks down either side of the
bottom shelves, creating a flue tunnel which will draw from the front of the
kiln. If a little bit of the flue shows above this bottom shelf at the back
this is OK. That will happen if you use a corbeled arch over the flue
opening. This setup gives the most even temperatures I have been able to
achieve in downdraft kilns. No coincidence that some of the country's major
downdraft kiln manufacturers use the same system.
Good luck -
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Tracy Dotson on fri 12 feb 99
Jennifer.....you did not mention the size the shelves and how you usually
stack them in the kiln ( distance from the back wall, space between the other
shelves and between the shelfs and the bag wall). You are so close to being
even to make some potters will say why bother but I think all you may need is
some "tweeking" of the bag wall and the spaces between the shelves and the
hight of the first shelf layer off the floor. Unless you are usto fireing
your kiln with 2 burners down the fire box, you may become more frustrated in
your results (reducrion and heat spots) I know I will get some flack on this.
I have found that the easiest way to spread the heat evenly in a fire box is
to mount the burners at sides of the kiln.
Also the hard brick on the floor adds mass to the cooling cycle as well as
taking the punishment of the weight of the shelf stack and in loading from
your feet.
It looks like you have a very good set of dimentions but with the shelf size,
I may be able to pass on some bag wall and stacking ideas to help even out
your kiln...Good luck..........Tracy Penland NC
Jennifer Boyer on fri 12 feb 99
Thanks for the input Vince,
I've been working with Mark Ward on this revision of my kiln. The reason for
the larger ports is that I have 2 pilot burners mounted under my B-4's and
with the standard ports that I have now, the pilot flames have always hit the
outside bricks. I can try to build the ports just as tall as the height of
B-4+pilot. I'll measure tomorrow and see if I can get away with less height
then 7.5". How do you deal with your pilots?
My (4)B-4's have run just fine at 22 oz so Mark feels that 2 burners at 5-6
pounds is fine. I'm going to build side ports into the kiln and plug them up
just in case things don't go well.....
I'll have to think about bagwalls. The less width I have in the kiln the less
height I can have, making it smaller if I skip the bagwalls.
So you like creating a flue channel with brick on the floor better than
creating the flue channel IN the floor? That's what I have now, and was
planning to keep it, but I'm open for new ideas!
Take Care
Jennifer
Vince Pitelka wrote:
> ----------------------------Original message----------------------------
> >New Bertha: potential changes
> >40.5" wide and deep. 42" high
> >2 B-4 ransom venturi gas burners rear mounted w/ max pressure to 5 or 6
> >pounds
> >4.5"/7.5" burner ports(67.5 sq inches which would equal flue area)
> >13.5" high IFB bag walls
> >Gas pressure to 5 or 6 pounds.
> >IFB floor
>
> Jennifer -
> I think you are on the right track. Downdraft kilns which are taller than
> wide do not tend to fire evenly. Your new design sounds good. However, I
> am a firm believer in burner ports just large enough to allow in adequate
> secondary air. Any larger than that and you tend to get excess secondary
> air, which will just slow down your firing. I like to make my burner ports
> 4.5" by 5" maximum, which should let in plenty of secondary air for those
> burners.
>
> I do not know if two of those Ransome B-4s will be adequate at 5 or 6 pounds
> of pressure. Mark Ward can tell you. But you should be able to guess,
> depending on how the four B-4s worked on the old kiln. Did it seem greatly
> overpowered? Granted, the new kiln is smaller and better proportioned, but
> you want to check this out thoroughly before proceeding. It would be a
> shame if you had to bore two more burner ports and add the other two B-4s.
>
> You can get away without any bag wall at all with the burners coming in from
> the rear corners, but you should put a target brick half way forwards to
> deflect the flame upwards, and when you place your first shelf, place it up
> 4.5 inches high, right up against the back wall of the kiln, above the flue
> opening, and place 2800 degree IFBs or hardbricks down either side of the
> bottom shelves, creating a flue tunnel which will draw from the front of the
> kiln. If a little bit of the flue shows above this bottom shelf at the back
> this is OK. That will happen if you use a corbeled arch over the flue
> opening. This setup gives the most even temperatures I have been able to
> achieve in downdraft kilns. No coincidence that some of the country's major
> downdraft kiln manufacturers use the same system.
> Good luck -
> - Vince
>
> Vince Pitelka - vpitelka@DeKalb.net
> Home 615/597-5376, work 615/597-6801, fax 615/597-6803
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
--
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer jboyer@plainfield.bypass.com
Thistle Hill Pottery
Vermont USA
http://www.vermontcrafts.com/members/JenniBoy892.html
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer on sat 13 feb 99
Hi Tracy,
Thanks for your comments. As I said in my first post, I use 2 16/20 shelves for
a stack space of 20/32. Also my new kiln will have a car. Mark suggested using
pieces of kiln shelf under the stack posts on the new IFB floor. My kiln cools
REALLY slowly, so I'm not really worried about losing firebrick mass, but that i
something I'll rethink. I've tweeked my bagwall plenty, and if you'll notice
from my original post the kiln top and bottom are even with the middle being hot
and the top and bottom back cool. SO I came to a point where anything more I did
to the bagwall would cool off either the top or bottom back more, making the
situation worse. I have a 2 cone variation, which seems worth trying to
improve. Or maybe I'm dreaming.....
The new kiln plans have the flue trench 2.5" deep in the floor. The rest of the
flue rises 5 inches so the back shelf would cut across the flue opening.
I have small spaces in my bagwall. I place my shelves toughing the back wall,
and always start the back stack with a layer of tall vases or lamp bases. Where
would you anticipate hot spots with rear mounted burners?
My old kiln has 4.5" wide fire box and 1-2" between the bagwall and the shelves.
The new kiln will have a 5.5" wide firebox and 2.25" inches between the bagwall
and the shelves.
Take Care
Jennifer
Tracy Dotson wrote:
> ----------------------------Original message----------------------------
> Jennifer.....you did not mention the size the shelves and how you usually
> stack them in the kiln ( distance from the back wall, space between the other
> shelves and between the shelfs and the bag wall). You are so close to being
> even to make some potters will say why bother but I think all you may need is
> some "tweeking" of the bag wall and the spaces between the shelves and the
> hight of the first shelf layer off the floor. Unless you are usto fireing
> your kiln with 2 burners down the fire box, you may become more frustrated in
> your results (reducrion and heat spots) I know I will get some flack on this.
> I have found that the easiest way to spread the heat evenly in a fire box is
> to mount the burners at sides of the kiln.
> Also the hard brick on the floor adds mass to the cooling cycle as well as
> taking the punishment of the weight of the shelf stack and in loading from
> your feet.
> It looks like you have a very good set of dimentions but with the shelf size,
> I may be able to pass on some bag wall and stacking ideas to help even out
> your kiln...Good luck..........Tracy Penland NC
--
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer jboyer@plainfield.bypass.com
Thistle Hill Pottery
Vermont USA
http://www.vermontcrafts.com/members/JenniBoy892.html
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Vince Pitelka on sat 13 feb 99
>I've been working with Mark Ward on this revision of my kiln. The reason for
>the larger ports is that I have 2 pilot burners mounted under my B-4's and
>with the standard ports that I have now, the pilot flames have always hit the
>outside bricks. I can try to build the ports just as tall as the height of
>B-4+pilot. I'll measure tomorrow and see if I can get away with less height
>then 7.5". How do you deal with your pilots?
Jennifer -
We have two kilns with venturi pilots mounted beneath the main burner tips,
and both kilns have burner ports 4.5" by 5". Works fine. It can be a
pretty close fit, and the draft will still pull in plenty of primary air.
>My (4)B-4's have run just fine at 22 oz so Mark feels that 2 burners at 5-6
>pounds is fine. I'm going to build side ports into the kiln and plug them up
>just in case things don't go well.....
That sounds fine. The alternative would be two ports in front, opposite the
ones in the back, but then the front burners get in the way.
>I'll have to think about bagwalls. The less width I have in the kiln the less
>height I can have, making it smaller if I skip the bagwalls.
That is exactly the issue in most kilns with bagwalls. If you do get away
with just the two burners at the back, there is no reason for bagwalls. The
tendency of the flue to pull the flames directly to the bottom rear of the
kiln can be remedied by the method I mentioned - place the bottom shelf
right against the back wall above the flue, and place bricks beneath the
edges of the shelves, forming a flue tunnel which draws from the front of
the kiln.
>So you like creating a flue channel with brick on the floor better than
>creating the flue channel IN the floor? That's what I have now, and was
>planning to keep it, but I'm open for new ideas!
In some cases a flue channel in the floor is necessary, but in this case I
like to use the space below the first shelf as a flue tunnel. It works
great, and elminates the complexities of a flue tunnel in the floor. I like
to avoid a flue tunnel in the floor because it places the flue below the
burner ports, and I do not believe in that relationship.
Good luck -
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Jonathan Kaplan on sun 14 feb 99
Jennifer:
I designed and built two kilns for clients this year, Castle Clay in Denver
and The Potters Wheel here in Steamboat.
There is a full set of plans available for the "Scooter 9000" if you are
interested and would pay for copying costs.
It is a 40 cu ft IFB kiln with a spring arch and fiber door. Based on a
cube, around 2 shelves that are 14" x 28" giving a shelf space of 28" x 28"
..
Best,
Jonathan
Jonathan Kaplan, president
Ceramic Design Group LTD/Production Services
PO Box 775112
Steamboat Springs CO 80477
plant location
1280 13th Street Unit 13
Steamboat Springs CO 80487
(970) 879-9139 voice and fax
jonathan@csn.net
http://www.sni.net/ceramicdesign/
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