mel jacobson on thu 11 aug 05
if any of you have nils lou's/`art of firing`...look at the picture
of the natural draft electric kiln vent that i use.
it is a piece of 5 inch stainless steel pipe..10 feet long.
i goes right through my ceiling/roof.
i have a 1 inch pipe that runs from it to my kiln.
drilled a hole in the kiln side. near the top. i plug the peeps etc.
it has a slight angle up...the bottom and top of the pipe are open.
as the kiln fires...it makes a chimney.
all the ick goes right out.
when the kiln is done...i put a piece of foam in the bottom of
the pipe to slow down the draft...as i don't want the bisque to
cool too fast.
works like a charm.
easy. you must use stainless...it will rot out a piece of galvanized
in a few firings.
i am toying with using heavy plastic sewer pipe/four inch..
i know it would not burn or get too hot with just the small amount
of air/mixed with heat, and the draft air coming from the bottom would
cool it fast.
something for someone to experiment with.
no blower, fan...motor.
just natural draft. i will add a drawing to the clayart page...if i can
find it.
i have re/shot some of the images (website) from the last firing..with
rhodes 32V (v for variation, thank you ron.) a bit brighter light.
the teapot image is new.
and the two images on my index page are new.
one with iron red interior. i think you can feel them, even
in a picture.
mel
i think ron has come up with a new symbol for glaze recipes.
name, cone, V for variation.
so:
Rhodes 32 V , cone 10, reduction/iron bearing clay body. from david shaner.
added silica to taste.
hmmm, i like it.
from mel/minnetonka.mn.usa
website: http://www.pclink.com/melpots
http://home.comcast.net/~figglywig/clayart.htm
for gail's year book.
Gordon Ward on thu 11 aug 05
Thanks Mel - love the simplicity of your vent. Should last forever...
Makes me think that a fan system could be built on this principle, so
that the fumes don't actually go through the blower - in the absence
of a clear shot for natural draft like yours.
Your photos of 32v want to make me try it. Probably will.
Gordon
John Baymore on fri 12 aug 05
Makes me think that a fan system could be built on this principle, so
that the fumes don't actually go through the blower - in the absence
of a clear shot for natural draft like yours.
Gordon,
Yup this is rather common in industrial setups. They are often refered to
as a "draft inducer". I have uesd them numerous times also for gas kilns
where some design constraint dictated their use to solve a "problem".
Simplified.........I'll try to describe it here in words:
Put in a "T" unit in the duct piping laying on it's side with the long side
connected to the kiln you want to vent. The now vertical "top" part of the
original "T" shape is pointing vertically up and down. The top pointing
part is ducted to the exterior in order to vent the crap out of the
building. On the bottom down-pointing part, you place the blower unit. It
does not have to be anything "special" because it sees no real heated
gases.... just cool air through it. (You can place this unit outdoors... or
can duct the supply of inlet air for this blower directly TO the outdoor
fresh air.)
The one "caveat" here is that the static pressure in the ducts has to be
considered a bit. If the "resistance to flow" in the "to the outside"
portion of ducting AFTER the leg that is connected to the kiln is too
high..... the blower will send cold air INTO the kiln instead of pulling
stuff out of the kiln. Not what you want ! Again as a generality....
the duct past the kiln needs to be sized (XC plus calculations for rise and
ells and such) to handle the kiln effluent removed PLUS the air supplied by
the blower. This can be tested by more potter-type "trial and error"
methods... or you can do the math....... if you are so inclined .
The "T" area of this basic idea can be modified to improve it's
characteristics... such as creating a venturi shape with the kiln leg
entering at the exact correct place to increase the draw relative the to
volume of air moved by the blower. But to do this correctly it gets into
some "sophisticated engineering" and if you have to ask questions about
HOW... you probably won't really succeed . Venturi design is a tad more
complicated than just creating a narrowing in the duct ...... due to the K
factor in the venturi equation (basically the resistance to flow created by
turbulent gas flow at the restriction point).
Oh,.... and mel-san.... have used PVC for venting electrics ...but with a
blower supplying air movement....never the passive natural draft method you
mention. Works just fine and doesn't corrode from the suplhirc acid
generated from the sulphur in the clay getting oxidized and combining with
the H2O vapor generated and condensing out of the effluent. Good idea to
put in drip T's in the PVC stuff or the metal though .
best,
....................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
JBaymore@compuserve.com
http://www.JohnBaymore.com
"Please use compuserve address for any direct communications."
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