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#1 jrgpots

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Posted 03 July 2014 - 09:41 PM

I am drawing plans for a 15 cubic ft sprung arch downdraft kiln powered by 2 power blowers. The walls will be 9" thick. The power blower inlets will be 4" diameter. The outlet flue and chimney will be 8 x 4 1/2 internal dimensions.

The first of many question:
1. How high does the chimney need to be?
2. Can the bricks above the damper be K20 or less?

Jed

#2 Mark C.

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Posted 03 July 2014 - 10:11 PM

10-12 foot minimum more is always better as you can slow the suck down with damper but cannot make more with a short stack this is for natural draft.

if you have power blowers the stack can be very short just above kiln roof like Giel or a Bailey kiln

As to the k-20s the damber gets hot so use good bricks  a foot past it at least then you can use lesser bricks.

Mark


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#3 jrgpots

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Posted 03 July 2014 - 11:05 PM

That just what I needed.

Thanks,

Jedc

#4 Marcia Selsor

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Posted 04 July 2014 - 10:36 AM

Agrre with Mark. If you are using power blowers on your burners, you don't need a high stack. Natural draft is where the chimney needs to be naturally drawing the draft through the kiln. For your chimney needs to be a few feet taller than the kiln and definitely taller than a peak in a close roof line.

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#5 jrgpots

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Posted 04 July 2014 - 12:09 PM

Agrre with Mark. If you are using power blowers on your burners, you don't need a high stack. Natural draft is where the chimney needs to be naturally drawing the draft through the kiln. For your chimney needs to be a few feet taller than the kiln and definitely taller that a peak in a close roof line.Marcia


Can I use triple wall chinmey pipe as the stack goes through the roof?

Jed

#6 JBaymore

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Posted 04 July 2014 - 01:09 PM

Iffy.

 

best,

 

.....................john


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#7 jrgpots

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Posted 04 July 2014 - 03:00 PM

Thanks John.

Jed

#8 Biglou13

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Posted 04 July 2014 - 09:50 PM

You had me at power burner........
Are u making or buying?
I starting to put the part I was given togehter.

Draft is mostly controlled by power burner. So you can go short.

You also had me at 9 inches....
Man I'm having kin envy........

Not sure I understand your exit flue chimney calculations?

Do share your share your designs
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#9 jrgpots

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Posted 05 July 2014 - 12:35 AM

I have converted by natural draft burners to power burners. Each puts out about 45,000 BTU/hr. So I think I will need to makes two more for a total of 180,000 BTU/hr. If I use the 4 burners, I will have increase my exit flue to be 9"x 9". I think I can rebuild my 2 burners using 3/64" jet orifice and 2" mixing tubes giving me 90,000 BTU/hr each. If I can do this, the flue size can be 4" x 9", I think....

The interior footprint will 24" x 37". It will be 2'3" high at the side wall with a sprung arch top. That footprint should fit one 18" x 18" shelf and one 9" x 18" shelf. I should get two levels of shelves.

I'm still drawing the plans. I'll post them for review in about 2 week. For me this is a BIG project. I still have some apprehension.

If I have to buy new bricks this project is estimated at $3,200...I think. Marc will probably correct my estimate though.

Jed

#10 Marcia Selsor

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Posted 05 July 2014 - 09:06 AM

18 x 18 shelves sound heavy unless they are Advancers.
I always designed kilns around the size of a kiln shelf I could work with ..like 12 x 24.

Marcia

#11 JBaymore

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Posted 05 July 2014 - 09:27 AM

I use a lot of 18 x 18 shelves Marcia... even as an offical "old guy"...... not too bad unless they are the OLD 3/4" to 1"  standard SiC ones.  But I also have a lot of Advancers in the same size now......... a pleasure to handle. 

 

best,

 

................john


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#12 JBaymore

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Posted 05 July 2014 - 09:33 AM

Given your numbers above, I calculate about 15.5 total gross cubic feet.  If the walls are 9" IFB, the floor at least 7.5" thick with 5" graded IFB and a working floor of 2.5" hard (preferable 9" or 10" thick), and the arch 4.5" IFB backed with either a couple inches of fiber or another layer of graded IFB....... you only need about 150,000 BTU/ hr. input for typical cone 9-10 use.  And assuming 10% excess air capacity (for firing fully in oxidation all the way up if desired), blowers that will supply 27.5 CFM (not counting static pressure losses there).

 

best,

 

.............john


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#13 Mark C.

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Posted 05 July 2014 - 11:50 AM

My favorite kiln shelve size is 12x24. My whole life in ceramics goes they that shelve size. Advancers that size are 9#s and I can move them easy-they are wide enough for most items. Most of my fellow potters also use that size.

When we bought our advancers (my 50) we ordered them in group purchases at a small savings-10 was the minimum order. we ball bought them over some time.

I have a few advancer 12x 18s in my small updraft-these cost more as they are not as standard as 12x 24s..

 

Mark


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#14 jrgpots

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Posted 05 July 2014 - 07:57 PM

Given your numbers above, I calculate about 15.5 total gross cubic feet.  If the walls are 9" IFB, the floor at least 7.5" thick with 5" graded IFB and a working floor of 2.5" hard (preferable 9" or 10" thick), and the arch 4.5" IFB backed with either a couple inches of fiber or another layer of graded IFB....... you only need about 150,000 BTU/ hr. input for typical cone 9-10 use.  And assuming 10% excess air capacity (for firing fully in oxidation all the way up if desired), blowers that will supply 27.5 CFM (not counting static pressure losses there).

 

best,

 

.............john

I had planned on using #1 9 inch wedges for the arch giving me 9"   thickness on the arch instead of the 4 1/2 with added refractory on top.  I planned on 2 rows of hard brick on the floor for 5" thickness (2 layers of 2 1/2 hard brick).  Is that enough? Could I get away with a 4" layer of common brick under the 5" hard brick?

 

jed



#15 JBaymore

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Posted 05 July 2014 - 08:04 PM

5" of hardbrick .... nope. It gets done all the time.... and then potters wonder why the bottom fires cold. It is NOT good.

 

MINIMUM of 5" IFB and 2.5 of hard. Or 7.5 of IFB if you use somethiong like Greenlite 28s for the working surface.

 

The heat energy moves thru the floor "wall" the SAME as it moves thru everywhere else. Heat energy does NOT "rise".

 

9" of IFB for an arch will work, but graded refractoris give you more insulating value.

 

best,

 

...............john


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#16 jrgpots

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Posted 05 July 2014 - 09:10 PM

I have hear you say that to others as well.  I will do 5" IFB with 2 1/2 " hard brick surface. 

Do you think I will outgrow a 15.5 cubic foot kiln?  Right now It will take me a month of spare time pottery activity to fill the kiln. The studio in the area only fires electric oxidation to ^6....What's a guy to do?  Besides,  I really like the ash glazes...  Does that sound like I'm justifying my project. lol.

 

Jed



#17 Biglou13

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Posted 06 July 2014 - 07:29 PM

Jrg let's face it what you really want is a wood burning kiln!!!

And yes go BIG.
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#18 JBaymore

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Posted 06 July 2014 - 07:36 PM

There are things to be said for having a smaller kiln ALSO. I have a big wood kiln, a medium gas kiln, and a small electric kiln. I am thinking of adding a small gas kiln now......... maybe 6-8 cubic feet. For quick tests of ideas/glazes/bodies.

 

Will you "outgrow" the kiln .... likely. But you have to start somewhere. And starting with something you can fire often as a newer potter........ that is a GOOD thing.

 

Keep in mind.... maybe you can add a second kiln down the road.

 

best,

 

.....................john


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

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