Daniel Rotblatt on sun 21 feb 10
I am about to build my first kiln, and I have a question about burner
placement in kilns. I'm building a small ~10 cu ft downdraft, and the
two propane burners will come in on either side of the smokestack
horizontally - pretty much following Nils Lou's MFT designs. I have
noticed that on all the kilns I've looked at the burners are placed
outside the kiln by an inch or so with the flame entering the port. I
have built a number of melting furnaces (for bronze or aluminum) and I
plant to use the same burners for the kiln. In the furnaces, the
burner tips enter the very close fitting port (which I completely
close off by inserting ceramic fiber around the end of the burner) and
the end of the burner is flush with the inside of the wall. There are
a few variations, but essentially these burners do not get any
secondary air, nor do they need them. It seems to me that setting the
burners back is just plain inefficient! Is there a downside to
placing the burners in a kiln like I do on my furnaces? The only one
I can think of is that if the draw of air into the chimney is enough,
it will pull more air through the burners and create an oxidizing
flame - although I imagine it would do the same if it was drawing more
secondary air as well. BTH, these are naturally aspirated burners
(sometimes called venturi burners).
In summation the question is, does the burner need to be set back from
the burner port for a burner that does not need secondary air?
Daniel Rotblatt
www.RotblattSculpture.com
shane mickey on tue 23 feb 10
danielPottery kilns have the burners on the outside for a reason. First of =
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ll is that with the head of the burner inside the kiln it will corrode over=
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ime and cause the flame retention holes(if it has them) to clog or in gener=
a=3D
l will just ruin the head of the burner. Most burner sets ups that i have s=
e=3D
en on speedy melts or furnaces are merely a piece of pipe with an orfice in=
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the back so if the end gets ruined it doesn't really hurt them. Secondly i =
k=3D
now bronze and aluminum melt much lower than our cone 10, thus the temperat=
u=3D
re at the burner port is significantly lower on metal furnace than on a con=
e=3D
ten kiln. I had a case where the client was getting severe back burning (f=
l=3D
ame coming out the back of the burner). It was due to the fact that the bur=
n=3D
ers had been sealed inside the burner ports by placing fiber board over the=
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burner tips to cut down on secondary air. On the kilns i build i use a much=
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tighter tolerance for my burner ports but still set the burner back about 3=
/=3D
4 of an inch to an inch. closer than is recommend, but the air mixture is b=
e=3D
tter controlled thru the primary air adjustment. I would advise to set back=
=3D
the burners at least one inch.shane mickeykiln design serviceshttp://www.sh=
a=3D
nemickeypotterslife.blogspot.com/
------------------------------------------------------------
Make the most out of every dollar. Click here to find websites and service=
s=3D
to help invest wisely.
Investing
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DANL. ROTBLATT on tue 23 feb 10
Shane,
Thanks. I pour my bronze at 2250 degrees F, which is in the cone 10
range, but I realized that the burner head is only at that
temperature for a short time - it takes 35 minutes or so to melt.
The kiln sits at high temps of 2000+ for a couple of hours. I also
make my burner heads out of stainless, but they are just a stainless
tube with the end forged out a bit wider (a 12 degree taper for a
couple of inches is ideal). The stainless holds up quite awhile, and
when it dies it's easy to make another one. Either way, I think I'll
just have to play with it - start with the burner set back an inch
and see how that works, then maybe try it a bit closer and see what
the difference is.
Thanks to all who gave me input on this! (I got several replies in
private)
Daniel Rotblatt
www.RotblattSculpture.com
On Feb 23, 2010, at 4:14 AM, shane mickey wrote:
> danielPottery kilns have the burners on the outside for a reason.
> First of all is that with the head of the burner inside the kiln it
> will corrode overtime and cause the flame retention holes(if it has
> them) to clog or in general will just ruin the head of the burner.
> Most burner sets ups that i have seen on speedy melts or furnaces
> are merely a piece of pipe with an orfice in the back so if the end
> gets ruined it doesn't really hurt them. Secondly i know bronze and
> aluminum melt much lower than our cone 10, thus the temperature at
> the burner port is significantly lower on metal furnace than on a
> cone ten kiln. I had a case where the client was getting severe
> back burning (flame coming out the back of the burner). It was due
> to the fact that the burners had been sealed inside the burner
> ports by placing fiber board over the burner tips to cut down on
> secondary air. On the kilns i build i use a much tighter tolerance
> for my burner ports but still set the burner back about 3/4 of an
> inch to an inch. closer than is recommend, but the air mixture is
> better controlled thru the primary air adjustment. I would advise
> to set back the burners at least one inch.shane mickeykiln design
> serviceshttp://www.shanemickeypotterslife.blogspot.com/
>
>
> ------------------------------------------------------------
> Make the most out of every dollar. Click here to find websites and
> services to help invest wisely.
> Investing
> http://tagline.excite.com/c?
> cp=3DlfXUbsRBszf42i9yBv9a5AAAKZQBVA8xn_DPiJKMg94jEn-7AAYAAAAAAAAAAAAAAAA
> AAADNAAAAAAAAAAAAAAAAAAADZhjqLlY=3D
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