Mel Jacobson on fri 5 sep 97
>To: clay
>From: Mel Jacobson
>Subject: burners
>
>big bethas can be a fine burner, however i am more and more
>becoming convinced that being able to control primary air is
>a very important function during the firing of a reduction kiln.
>
>i have been inventing ways of doing just that.
>
>if you are using big or little berthas, or nils burners and or
>any other burner that is open totally on the air end,
>cut a pop or beer can with a scissors (very easy to do) and
>create a cap or cover with louvers that can restrict the air
>flow to the burners. i have cut a straight line and then a circle
>that will fit over the gas pipe. this pop can or aluminum bellows
>can be moved in or out to create primary air reduction.
>
>also changing the gas pipe coming into the burner to threaded
>rod (if you can find the right size) and adding a screw on cap
>that could be screwed down against the burner inlet...or some
>such thing. (won't work on bertha)
>
>some people will stuff a little piece of kaowool in the air intakes, but
>i really do not like to totally restrict the air.
>
>i have two old 500,000 btu denver burners on my big kiln...they have
>a bell bellows that screws down to completely close off the primary
>air. since seeing a mark ward post on air reduction at the end
>of firings i went back over some notes that are almost 40 years old
>and low and behold, that is how i fired in 1960...then with the
>energy scare i started to fire with the bellows wide open all during
>the firing. i now back the primary air to almost off when i reach cone 9
and fire that way til 11 starts to drop. then i open the air, the damper
and infuse oxygen into the kiln for about 20 minutes. shut if down, and
>leave the kiln open for another 20 minutes. the pots are much better,
richer in reduction, and the color better...they look like glazes from
>1960. this firing schedule also came at the time i sprayed
>the kiln with itc 100....it all helped.
>
>i am sure that closing down the primary air has caused the kiln
>to be more even....the last cold spot in front of the flue has left.
>i cannot really explain that, but it has happened. when i fire
>with a yellow flame, slow and easy, the kiln just evens out as
>nice as can be. go figure.
>mr. science.
p.s. it is very easy to make a nice, easy working burner
out of things from the hardware store....iron pipe, fittings
threaded pipe, etc. i had some old baso valves around the
farm, so built some small burners that have pilots on them
that can be placed in a kiln overnight. the average is about
100,000 btu's. we can get a kiln to 1200 degrees overnight,
a slow firing, no fuss, and safe. and the kiln is really warm when
you hit the big burners to full. (we do not have to worry then about
burners blowing out)
http://www.pclink.com/melpots
stephen on mon 8 nov 99
Hello all. Had a very satisfying day today. Made and test fired four
homemade propane burners. I used the design in Frederick Olsen, The Kiln
Book. On page 204,fig 7-43. The 1 1/4 inch IPS, Sch. 40. I used a #48 drill
which should give 40,400 BTU at the pressure I have of 11 inch WG.
THEY ROAR!
Now I have a Question. I noticed that the blue flame was down inside the
vertical Flame tube. Somewhere. Oh there was a good blue shaft of flame
outside about 3 to 4 inches and an equal amount above that of feathery
yellow. Is it normal for this primative sort of burner to have flame inside
of the flame tube? They seemed to resist going out, in the blustery winds we
had tonight.
I'm aiming at a copy of the Geil 802 Kiln eventually. I feel very encouraged
now.
Best Peace,Steve Yahn
Louis H.. Katz on tue 9 nov 99
Hi Steve,
My first suggestion before any explanation is that you buy some flame retention
rings from a reputable source such as Pyronics or Eclipse or Ward Burner. Of
course it might make sense to just buy the whole burner.
As the gases, a mixture of air and gas, move away from the orifice the front
of flame burns toward the orifice. The flame " burns back" until the two speeds
reach equilibrium.
A good flame retention ring provides a venturi where the gases are speeded up
allowing a burner to be turned down further before burning back. They also
contain a ring of small diameter holes that slow down the travel of gas enough
that the gases pasing through them can act as a ring of pilots keeping the
flame ignited closer to the burner.
Once back burning it can be hard to extinguish the flame at the orifice. Often
the pipes get so hot that they help the flame travel back to the burner
orifice.
If your kiln is red hot and you have an effective safety system, you can try
and extinguish the flame inside the burners by taking a small hand operated
spritz bottle and spraying a little water in the burner. Of course this won't
amount to even a teaspoon of water. It may however cool your thermocouple on a
safety system or interfere in some other way.
Louis
stephen wrote:
> ----------------------------Original message----------------------------
> Hello all. Had a very satisfying day today. Made and test fired four
> homemade propane burners. I used the design in Frederick Olsen, The Kiln
> Book. On page 204,fig 7-43. The 1 1/4 inch IPS, Sch. 40. I used a #48 drill
> which should give 40,400 BTU at the pressure I have of 11 inch WG.
> THEY ROAR!
> Now I have a Question. I noticed that the blue flame was down inside the
> vertical Flame tube. Somewhere. Oh there was a good blue shaft of flame
> outside about 3 to 4 inches and an equal amount above that of feathery
> yellow. Is it normal for this primative sort of burner to have flame inside
> of the flame tube? They seemed to resist going out, in the blustery winds we
> had tonight.
> I'm aiming at a copy of the Geil 802 Kiln eventually. I feel very encouraged
> now.
> Best Peace,Steve Yahn
Vince Pitelka on wed 10 nov 99
>A good flame retention ring provides a venturi where the gases are speeded up
>allowing a burner to be turned down further before burning back. They also
>contain a ring of small diameter holes that slow down the travel of gas enough
>that the gases pasing through them can act as a ring of pilots keeping the
>flame ignited closer to the burner.
Louis -
As I understand it, there is more to it than this. A flame-retention
burner-tip need not create a venturi effect. It need only create turbulence
in the moving stream of air and gas. That is why almost any design which
accomplishes this works just fine, explaining the broad diversity in
flame-retention tips out there. Whether a venturi burner or a straight tube
burner, the release of gas from the orifice and the resulting
air-entrainment do not result in a particularly efficient mixing of the air
and gas. A flame retention tip creates turbulence within the tip,
thoroughly mixing the air and gas, encouraging maximally efficient
combustion right at the tip. That is why a burner with a
flame-retention-tip has good turn-down characteristics. Even with the gas
set low, the mixing of air at the tip and the resulting efficiency of
combustion discourages the flame from "back-burning" into the burner tip.
The other common burner flame flaw, known as "flame-off" occurs when the
speed of travel of the gas and air exceeds the speed of combustion, and the
flame blows off the burner tip and extinguishes itself, such as often
happens in tube or venturi burners which are not equipped with a retention
tip. The flame-retention-tip accelerates combustion, preventing flame-off.
The old Norman updraft kilns we have at the Craft Center have ceramic
venturi burner tubes, and for flame retention the tubes simply have a sudden
increase in bore diameter just inside the burner tip. When the moving
stream of air and gas reaches this sudden increase in size, it causes the
necessary turblence for effective flame-retention.
And to Steve Yahn -
I think that homemade tube-burners can work just fine when they are properly
made, but they really do need flame-retention-tips. As Louis suggested,
contact a supplier and get proper tips to thread on to your 1 1/4" pipe.
Best wishes -
- Vince
Vince Pitelka
Home - vpitelka@DeKalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Louis H.. Katz on thu 11 nov 99
Hi Vince,
Thanks for the information on turbulence needed for mixing. It fits what I belie
to be true.
However, turbulence alone will not keep flames from moving back through a burner
why would it? If a zone of a gas and air mixture is ignited and hot and there is
other gas an air nearby, why shouldn't they ignite too?
Lack of mixing before the burner tip might prevent backburning.
As your tubes open up on your Norman kiln the average speed of the gases lessens
allowing the flame wall to exist in that zone.
At a low turndown if you close down the air (slowing the speed of gases) the
burner will backburn. If you open the primary air before the burner has heated u
you can "blow" the flame out of the mixer to the front of the tip where it
belongs.
I use natural draft pipe burners with flame retention rings at school. But, I
strongly prefer quality mixers (venturi tubes) on my burners. They allow more
primary air to be entrained inside the burner, and provide far more flexibility
firing with natural gas. I also prefer adjustable orifices which allow you to
minimize the orifice size and maximize entrained air. These burners are a joy,
and can be adjusted for a very stable flame. Quiet too!
Louis
Vince Pitelka wrote:
> ----------------------------Original message----------------------------
> >A good flame retention ring provides a venturi where the gases are speeded up
> >allowing a burner to be turned down further before burning back. They also
> >contain a ring of small diameter holes that slow down the travel of gas enoug
> >that the gases pasing through them can act as a ring of pilots keeping the
> >flame ignited closer to the burner.
>
> Louis -
> As I understand it, there is more to it than this. A flame-retention
> burner-tip need not create a venturi effect. It need only create turbulence
> in the moving stream of air and gas. That is why almost any design which
> accomplishes this works just fine, explaining the broad diversity in
> flame-retention tips out there. Whether a venturi burner or a straight tube
> burner, the release of gas from the orifice and the resulting
> air-entrainment do not result in a particularly efficient mixing of the air
> and gas. A flame retention tip creates turbulence within the tip,
> thoroughly mixing the air and gas, encouraging maximally efficient
> combustion right at the tip. That is why a burner with a
> flame-retention-tip has good turn-down characteristics. Even with the gas
> set low, the mixing of air at the tip and the resulting efficiency of
> combustion discourages the flame from "back-burning" into the burner tip.
> The other common burner flame flaw, known as "flame-off" occurs when the
> speed of travel of the gas and air exceeds the speed of combustion, and the
> flame blows off the burner tip and extinguishes itself, such as often
> happens in tube or venturi burners which are not equipped with a retention
> tip. The flame-retention-tip accelerates combustion, preventing flame-off.
>
> The old Norman updraft kilns we have at the Craft Center have ceramic
> venturi burner tubes, and for flame retention the tubes simply have a sudden
> increase in bore diameter just inside the burner tip. When the moving
> stream of air and gas reaches this sudden increase in size, it causes the
> necessary turblence for effective flame-retention.
>
> And to Steve Yahn -
> I think that homemade tube-burners can work just fine when they are properly
> made, but they really do need flame-retention-tips. As Louis suggested,
> contact a supplier and get proper tips to thread on to your 1 1/4" pipe.
> Best wishes -
> - Vince
>
> Vince Pitelka
> Home - vpitelka@DeKalb.net
> 615/597-5376
> Work - wpitelka@tntech.edu
> 615/597-6801 ext. 111, fax 615/597-6803
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
Earl Brunner on thu 11 nov 99
This thread raises a question.
I have never messed with the air settings on my burners during a firing, general
I leave primary air and even secondary air alone throughout the firing. I make
adjustments with the gas valve and the damper. (Natural gas, downdraft) I have
noticed that in the early stages of the firing the burners make quite a bit of
noise, a low roar... at some point (I'm just guessing here, because I've never
written it down) say around 800 F. I make an adjustment and quite suddenly the
burners get much quieter. I presume from what I've been reading that this would
the "norm" and that until this happens the burners are not burning correctly? W
I'm not sure from what I've read is whether or not this is detrimental to the
burners. Mine have ceramic burner tubes.
Louis H.. Katz wrote:
> ----------------------------Original message----------------------------
> Hi Steve,
> My first suggestion before any explanation is that you buy some flame retentio
> rings from a reputable source such as Pyronics or Eclipse or Ward Burner. Of
> course it might make sense to just buy the whole burner.
>
> As the gases, a mixture of air and gas, move away from the orifice the front
> of flame burns toward the orifice. The flame " burns back" until the two speed
> reach equilibrium.
> A good flame retention ring provides a venturi where the gases are speeded up
> allowing a burner to be turned down further before burning back. They also
> contain a ring of small diameter holes that slow down the travel of gas enough
> that the gases pasing through them can act as a ring of pilots keeping the
> flame ignited closer to the burner.
>
> Once back burning it can be hard to extinguish the flame at the orifice. Often
> the pipes get so hot that they help the flame travel back to the burner
> orifice.
> If your kiln is red hot and you have an effective safety system, you can try
> and extinguish the flame inside the burners by taking a small hand operated
> spritz bottle and spraying a little water in the burner. Of course this won't
> amount to even a teaspoon of water. It may however cool your thermocouple on a
> safety system or interfere in some other way.
> Louis
>
> stephen wrote:
>
> > ----------------------------Original message----------------------------
> > Hello all. Had a very satisfying day today. Made and test fired four
> > homemade propane burners. I used the design in Frederick Olsen, The Kiln
> > Book. On page 204,fig 7-43. The 1 1/4 inch IPS, Sch. 40. I used a #48 drill
> > which should give 40,400 BTU at the pressure I have of 11 inch WG.
> > THEY ROAR!
> > Now I have a Question. I noticed that the blue flame was down inside the
> > vertical Flame tube. Somewhere. Oh there was a good blue shaft of flame
> > outside about 3 to 4 inches and an equal amount above that of feathery
> > yellow. Is it normal for this primative sort of burner to have flame inside
> > of the flame tube? They seemed to resist going out, in the blustery winds we
> > had tonight.
> > I'm aiming at a copy of the Geil 802 Kiln eventually. I feel very encouraged
> > now.
> > Best Peace,Steve Yahn
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
Hank Murrow on thu 11 nov 99
>----------------------------Original message----------------------------
>>A good flame retention ring provides a venturi where the gases are speeded up
>>allowing a burner to be turned down further before burning back. They also
>>contain a ring of small diameter holes that slow down the travel of gas
>>enough
>>that the gases pasing through them can act as a ring of pilots keeping the
>>flame ignited closer to the burner. Louis Katz
Louis you are right on; A good flame retention tip has a narrowing at the
tip which has several small holes drilled in it to allow some of the
gas/air mixture to form an annular ring of fire when lit. Imagine the
burning hoop the lions jump through at the circus. When the main flow of
gas/air mixture goes past this annular ring of fire, it
burns......beautifully and completely. Because the ring of fire is
protected within the tip, the flame cannot blow off the tip, nor can it
travel back down into the mixer. The best example of this is an Eclipse
"Sticktite" burner nozzle. Get a peek at one sometime, as they're really
elegant. If short of cash, you can make a sort of replica by welding a
washer (which has several small holes drilled in it) inside a plain pipe
burner. The washer should have a central hole about two-thirds its
diameter, and should be placed back inside the pipe about 1/2" to 3/4" from
the mouth. And ask Eclipse for their H-1 Atmospheric Mixer Bulletin,
they're the best (no I don't own stock), I use them in my Doorless Fiber
kilns. Hank in Eugene
Chris on fri 17 mar 00
------------------
I=92m not sure how to start this post but I=92m in the process of rebuilding=
an
old Dickerson cone 10 kiln. I=92m trying to change it from an up draft to a
down draft. This is my problem. I don=92t have the burners that came with
the kiln, someone changed it to a forced air system and did a very poor
job. This is what has led me to the change, it=92s not a bad kiln soft brick
and what not. The thing is I=92m stuck on the high-pressure versus the low-
pressure venturi burner thing. I checked on some kiln sites and the inside
of the kiln is about 16 cu ft. and should need 200,000 btu. per. hr. to
reach =5E10 . Please feel free to correct me if I=92m off. I have 7 wcl.in. =
of
natural gas with about 130 ft. of 2=94 gas line feeding this kiln now. I
also have a 500 gal. Propane tank with 11 wcl.in or I can T off that
regulator and get to 2 lbs. of propane. So as you can see I have the gas
thing covered. So does anyone out there have some old west coast straight
tube venturi burners they would like to sell? I need 4 to make this work.
I=92ll pay a fair price, if so e-mail me. They should be about 12=94 in =
length
over all and have no more then a 2=94 outside Id. at the hot end. They sure
are asking a lot of money for burners now days. I guess I could just make
some but time and all? Would anyone like to help?
Cantello Studios on sat 18 mar 00
Sorry my e-mail address is tleecan@2xtreme.net this post is for the burner
?Chris thank you.
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.UKY.EDU]On Behalf
Of Chris
Sent: Friday, March 17, 2000 8:54 AM
To: CLAYART@LSV.UKY.EDU
Subject: Burners
----------------------------Original message----------------------------
------------------
I m not sure how to start this post but I m in the process of rebuilding an
old Dickerson cone 10 kiln. I m trying to change it from an up draft to a
down draft. This is my problem. I don t have the burners that came with
the kiln, someone changed it to a forced air system and did a very poor
job. This is what has led me to the change, it s not a bad kiln soft brick
and what not. The thing is I m stuck on the high-pressure versus the low-
pressure venturi burner thing. I checked on some kiln sites and the inside
of the kiln is about 16 cu ft. and should need 200,000 btu. per. hr. to
reach ^10 . Please feel free to correct me if I m off. I have 7 wcl.in. of
natural gas with about 130 ft. of 2 gas line feeding this kiln now. I
also have a 500 gal. Propane tank with 11 wcl.in or I can T off that
regulator and get to 2 lbs. of propane. So as you can see I have the gas
thing covered. So does anyone out there have some old west coast straight
tube venturi burners they would like to sell? I need 4 to make this work.
I ll pay a fair price, if so e-mail me. They should be about 12 in length
over all and have no more then a 2 outside Id. at the hot end. They sure
are asking a lot of money for burners now days. I guess I could just make
some but time and all? Would anyone like to help?
PBORIAN on sun 31 mar 02
Hello,
I have a question for those with kiln building experience. I have read in
Olsen's kiln book that one should never position the burners in such a way
that the orifice is above the burner tip. I would like for someone to
explain this principle, and i would also like to know if this would still
apply with propane. Also, would it then be allright to position the burners
with the orifice below the burner tip, with the gas flowing upward. I am
using forced air burners, if that makes any difference.
Any feedback would be greatly appreciated, as this is my first kiln building
project and i want to do it right. Thanks
Paul
Falmouth, ky
vince pitelka on sun 31 mar 02
> I have a question for those with kiln building experience. I have read in
> Olsen's kiln book that one should never position the burners in such a way
> that the orifice is above the burner tip. I would like for someone to
> explain this principle, and i would also like to know if this would still
> apply with propane. Also, would it then be allright to position the
burners
> with the orifice below the burner tip, with the gas flowing upward. I am
> using forced air burners, if that makes any difference.
Paul -
I have seen both arrangements (upward facing and downward facing burners),
usually with a right-angle tip pointing into the burner port, and I have
never known anyone to have problems with either arrangement, with either
natural gas or propane. The upwards facing burner is of course very common,
because virtually every updraft natural draft utilizes this arrangement, and
on other kilns whenever space is at a premium, it makes sense to have an
elbow just before the flame-retention tip, so that only the tip points into
the burner port, and the rest of the burner is parallel to the kiln wall
either hanging down below the burner port or else off to one side.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Dave Gayman on sun 31 mar 02
I'll let better engineers tackle this one, but wanted to point out that the
burner tip, not just the orifice and mixing chamber, has a lot to do with
your firing efficiency and speed. I found this out by accident -- a
foundry that had some leftover pieces of cast refractory that perfectly fit
my kiln floor needs also had a handful of commercial burner tips, and a guy
there explained their importance. He made maybe $40 on the total sale, so
it wasn't profit that drove him to take half an hour with me.
The tips do a final mix of gas and air, provide a self-piloting (= helps it
stay lit), shape the flame, and help determine where the hottest part of
the flame occurs downstream of the tip.
My 100 cu ft., forced-air, propane-fired catenary arch beauty is long gone,
but I still remember benefiting from somebody's burner tip engineering as I
watched flame shapes during the several stages of firing. By adjusting
blower speed and gas flow, I could play extra heat almost anywhere I wanted
it at any given point. I don't remember the name of the company who made
the tips and freely supplied the many pages of explanation and use
guidelines (there are probably better burner tips today anyway), or much
about the foundry and the guy who clued me in, but for 7 years, I was
deeply grateful for having stumbled across them.
Or maybe you already know this... apologies if you do.
At 05:21 PM 3/31/2002 -0500, you wrote:
>Hello,
>I have a question for those with kiln building experience. I have read in
>Olsen's kiln book that one should never position the burners in such a way
>that the orifice is above the burner tip.
Polly Harris on fri 5 apr 02
I fire propane and the burner is vertical - under the kiln. It is not forced
air.
The tip of the burner (not orifice) is approximately 11/2" below the floor of
the kiln - under side not top or inside of the kiln. There are no bag walls.
Most important with propane is the orifice size. My experience with 15
years of firing has netted two things. 1) your propane dealer has no idea
what you are doing 2) cultivate him anyway, so that you can get him to try
your ideas of how to fix what ever is not working right. Another observation
after moving last spring ... altitude does effect the orifice size.
Good luck....
p
Paul Taylor on mon 25 nov 02
Dear All (or rather any body that knows more about kilns than I - which
should be most of you.)
I am still wondering about a new kiln
I have changed my mind about preheated air for firing a kiln . I have
decided that any failure or leak in the recouperators ( the thingies that
heat the air) would leave me with another variable. The whole point of
building a new kiln is so I can have a kiln with the perfectly even
temperature little to go wrong and atmosphere that i can control with
different firing schedules.
I can not seem to get into contact with any of the authors concerned
with the energy efficient potters book but that may be because my server is
so paranoid about viruses and spam that he has been refusing to let Mr
Brodies reply through. The description of the burners the book suggest
building verge on the dangerous; because there are no details on the
positions of the safety ports or the spark ignition needed to run them.
If any body has drawings of nozzle mix burners and the safety set up I
would be grateful? If I could learn to build the burners and systems it
would make a cheap salt kiln out of my large kiln when the new one is in
service.
I need a kiln that is the most even; because the chinese style glazes I am
making need to be fired very accurately.
so I need to know
1 is a high velocity burner the same as a nozzle mix burner ? from my
research I think it once was but now they have improved the nozzle mix
burners and some give faster flame than others but I can not tell if I need
the burners that give the super fast flame or just the fast flame.
2 In a 20 cu foot kiln could a nozzle mixed burner be over kill? Would
forced air give me much the same results. Its always difficult to know the
proportional difference between these technologies. I think these
differences can be important but I know they are difficult to explain. Again
my criteria for this kiln is as few variables as possible and as even a
temperature and reduction as I can get.
3 I will be changing the kiln firing a lot so i have decided that I am
willing to adjust the kiln manually (air to gas proportions) according to my
oxiprobe. I am supposing that the flame speed will give me even atmosphere
as well as temperature. So will i need fancy control equipment beyond the
standard safety controls for either a nozzel mix or a blown air burner?
4 If I use nozzle mix burners will only one do ? and where do I put it in
relation to a down draft kiln. I can build a chimney I have the bricks.
however I do not have much head room - but I am tempted to adapt the design
from the energy efficient potters book. Has any body any experience of the
kiln described. the exit flue is in the roof and the nozzle mix burner fires
down from the roof.
--
Regards from Paul Taylor
Fifteen minutes of fame is all we ever need.
http://www.anu.ie/westportpottery
Craig Martell on mon 25 nov 02
Hi Paul:
Good luck getting an answer on Clayart about burner function. Outside of
two regular guys from Idaho and a rather inquisitive bloke from Australia,
I was totally skunked when I asked. I think the rest of the list were
firing electrics with controllers while catching the Three Stooges film
festival on Short Attention Span Theatre.
I don't think you need the hi velocity burners if you are going to build a
downdraft kiln. Those hi velocity jobs were used in updraft kilns and they
fired down from the roof so the flame was working against normal heat flow
and gravity too. It was sort of a reverse downdraft kind of design.
Are you talking about a 20 cubic ft total space kiln or a 20 cubic foot
stacking space kiln? You could fire a kiln of that size with two burners
firing from the back. You could make them yourself if you wanted to take
the time. Forced air design is not as difficult as venturis which take
some real careful proportion design in the mixer, throat, and exits. You
could also use four venturi inspirating burners, two front and two in back
and you wouldn't need blowers, solenoid valves, and a lot of other
stuff. When I fired with forced air, my burners were overloaded with extra
safety stuff and I also kept a gas generator handy in case of power failure.
If you are firing with propane and want to use venturis, look into the
"compound injector" designs. These burners will mix air and propane a lot
better than a single stage venturi. The whole thing with burner design is
AIR and how to move enough of it thru each burner to get efficient
combustion. With forced air, you will get all the air you want providing
you are using an adequate blower and you can also use a lower kiln chimney
because you don't need as much secondary air.
I'll shut up and let someone else talk, if the Stooges films are over and
they aren't laughing so hard they can't type.
regards, Craig Martell Hopewell, Oregon
Mondloch on tue 26 nov 02
> Good luck getting an answer on Clayart about burner function. >
> I'll shut up and let someone else talk, if the Stooges films are over and
> they aren't laughing so hard they can't type.
>
Hey, you guys just keep talking- we may be listening during commercials. ;)
Most of the burner posts fly right over my head, but I keep reading them
figuring eventually some of it should start to stick.
The glaze chem was incomprehensible to me at first too, but I'm finding that
more of it makes sense all the time, so maybe there's hope for burners too.
Sylvia
---
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake ,Wi 53075
HotArt@silvercreekpottery.com
http://www.silvercreekpottery.com
vince pitelka on wed 27 nov 02
> I want to cut the secondary air out of my kiln as a variable.
While this is certainly possible, I wonder why you would want to do this.
You need sealed-face burners to do that, and they are expensive and rather
exotic for a homemade studio kiln. Instead, you can easily minimize
secondary air and make it very easy to control. If you go to my website, go
to the gallery page, and then to the "Railroad Stoneware" page, there are
several pictures of a 100-cubic-foot car kiln I built for my production
studio in Northern California back in the early 80s. I built the kiln with
the standard 4.5" by 5" burner ports, but then I made softbrick inserts
which fit snugly in those openings. In each one I carved a round opening
that was 1" larger in diameter than the burner tip (1/2" all the way
around), and which flared open wider towards the inside of the kiln. The
burner tip was mounted 1/2" away from the outside face of the insert. With
that arrangement, I was able to control secondary air and
oxidation/reduction very easily with fairly small adjustments of the damper.
I never changed the primary air shutter settings on the burners.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://iweb.tntech.edu/wpitelka/
Paul Taylor on wed 27 nov 02
Dear Craig
Thanks for your advice .
From your posts I suspect you are working on the same sort of glazes that
I am.
I am starting to realize that my kiln is the most important tool I posses
And I am thinking that with a very well controlled kiln I can carry on with
better pots. I think there is a shadow of negativism left in the surface
treatments of my glazing that could be cured by having a tool I was
confident and prod of. As opposed to being apprehensive and relieved with
every firing that comes out well. I knows that my quest for the most
accurate kiln goes against the 'bung ho' inverted snobbery us potters are
meant to have.
From your question to the group it seemes you have also discovered the
necessity for these glazes to be fired very accurately because of the work
involved with glazing and decorating is too much to be hap hazard about the
firing.
Since starting my quest I have had to do lots of research and put away
prejudice . I have gained a deep respect for the chinese potters and a
mistrust of some of the more modern rumors on glazes and firing.
I want to cut the secondary air out of my kiln as a variable and as many
variables as I can . I know with deduction these variables can be managed;
but for thirty years I have lived quiet uncomfortably with the vagaries of
secondary air controlled by a damper and a flap over a hole entering the
side of the kiln . This flap lets the secondary air in under the burners
(internal ceramic cup burners supplied by venturies with high pressure 4
ppsi LPG ) . My kiln is about 40cu ft with about 30 something packing space.
It is tempting to place the pots especially bowls near the bag wall.
Sometimes I get small bloats on the surface of bowls if I do this. I suspect
that the firings I do are not only uneconomical but inaccurate as well .
Whats more ( apart from my guessing) I do not know what is going on with
the flame.
You know that I manage ok, but I feel with out the variable secondary air
controlled by the damper and also with a bit more flame speed I would have
more understanding of what is going on. In the archive some one mentioned
that secondary air some how helped in the transfer of heat . i still do not
understand that. I still think efficiently mixed primary air should do a
better job.
more control and less variables would allow me to change a reduction
schedule with ease. And if the schedule did not give the desired effects I
would know it was because of the proportion of amount of carbon to oxygen
to time was wrong, as opposed to never being sure If a firing experiment is
conclusive because I am not sure what is happening with the secondary air
and/ or the back pressure and or temperature - not sure what is happening at
all.
I suppose I am looking for a bit more than 'will do'. But after thinking
about it I am not going to stand a chance with these glazes on a commercial
level if I can not fir with the same even temperature that the ancients
fired to.
Could it be that we are at the same point with kilns as we were with
glazes twenty years ago when the best you could do was scrounge recipes or
wade through the arithmetic of Seeger analysis - with formulas that left the
important trace elements out. I suppose that knowledge of burners will never
get a common currency . Grinding the occasional bum test of a kiln shelf
because you made a bad calculation is nothing compared with rebuilding a
burnt down kiln room because you did not quiet get the flame retention
right.
As a synopsis of my knowledge so far :--- atmospheric burners (venturi)
made from old pipe are the least efficient.
Venturi burners with gradual openings helping to mix the gas is what I
have. I am not sure if a load of little ones is better than a few big
ones. I know that some of the technologies are better than others :- these
burners are safe and cheap to run. Many people run them with out fancy
flame familiar devises because they are so stable - but they all need
secondary air to burn efficiently. Again what i suspect is that for every
size kiln there is a number of burners run at a right pressure giving a
certain flame length with the right amount of secondary air which gives an
optimum kiln firing. the only trouble is, is that I do not know what these
measurements are and I can not afford the experimentation to find out. I
suppose you could study existing commercial kilns but that also supposes
they have got it right - by the reckoning of many they have nt. the other
point is as soon as you do a change in the fuel to air ratio all the other
variables go off and you are back to square one with deducing what the other
settings should be to get a decent firing.
The next most efficient are the forced air burners. I am supposing
(supposing ??) they give a greater flame speed . I do not know if they can
be mounted internally but most of the ones for sale seem to need a gap
between the burner head and the kiln for the flame sensors. Whether I should
concern myself that this gap lets in enough secondary air for it to be a
quantifiable variable in a kiln firing, or the venturi effect at the burner
tip is a relative constant that will not change appreciably with the weather
. I can allow for this with a pressure meter on my kiln that measures the
atmospheric pressure in the kiln but it is another bother.
I like my cup burners ( retention heads) they are made of two carved HTI's
one in top of the other with a fiber gasket in between. The cup and tube are
carved into each half. The nice thing about them is that they are inside the
kiln and are relatively silent but how they would work with a flame
familiar devise I do not know.
The next most efficient is the nozzle mix burners . They give a whacking
flame speed dependent on the design to how fast they go. the kits I have
seen take enough pipe work to refine oil and I do not know how much of this
is over kill. I am tempted to get one because it is said they give ultimate
control with no variables apart from the air gas ratio. even the shape of
the kiln matters little (within reason) because the speed of the flame is so
fast that the kiln can not help but heat up evenly; again as an improvement
relative to a forced air burner I have no idea.
What I can not get a handle on is the relative efficiency of any of these
systems. I have opinions but no measurements that I can compare.
What I liked about the nozzle mixed burners was the increase of packing
space relative to firing space at 16 cufoot packing you have a good 27 cu
foot of firing space with a nozzle mix burner you can get 20.5 cu foot
packing to the 27 internal firing space according to "the energy efficient
potter" book but I can not get hold of the author to check what drop in even
temperature efficiency there might be. - I suspect he is on to Larel and
Hardy by now.
But the fact that you went back to venturies from forced air has upset the
nozzle chart. Was it that venturi technology has progressed enough to catch
up with the forced air in efficiency/ or was it just the bother of the
(alleged) safety system that made you change back to venturies? I am now
wondering is if the burner heads are mounted externally does the venturi
effect on the secondary air prevents it from being a variable (or rather
keeps it more constant -or enough not to matter) as opposed to internal
secondary air which totally relies on the internal pressure in the kiln for
its function (if it is functioning at all with this set up)
Soon I will have to make some decisions. I have decided to get rid of as
many doubts as I can and then accept what I am doing as the best that can be
done. For once in my life I am doing this before I build the thing not
after.
I was grateful for Sylvia's post am glad to see that its not just you me
and two lads from Idaho interested in kilns - so I shall post you my
decisions.
--
Regards from Paul Taylor
'Craftsmanship is art'
http://www.anu.ie/westportpottery
phone 098 21239
Paul Taylor
Westport pottery
Liscarney
Westport
County Mayo
Ireland
> From: Craig Martell
> Reply-To: No title defined
> Date: Mon, 25 Nov 2002 17:39:13 -0800
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Re: Burners
>
> Hi Paul:
>
> Good luck getting an answer on Clayart about burner function. Outside of
> two regular guys from Idaho and a rather inquisitive bloke from Australia,
> I was totally skunked when I asked. I think the rest of the list were
> firing electrics with controllers while catching the Three Stooges film
> festival on Short Attention Span Theatre.
>
> I don't think you need the hi velocity burners if you are going to build a
> downdraft kiln. Those hi velocity jobs were used in updraft kilns and they
> fired down from the roof so the flame was working against normal heat flow
> and gravity too. It was sort of a reverse downdraft kind of design.
>
> Are you talking about a 20 cubic ft total space kiln or a 20 cubic foot
> stacking space kiln? You could fire a kiln of that size with two burners
> firing from the back. You could make them yourself if you wanted to take
> the time. Forced air design is not as difficult as venturis which take
> some real careful proportion design in the mixer, throat, and exits. You
> could also use four venturi inspirating burners, two front and two in back
> and you wouldn't need blowers, solenoid valves, and a lot of other
> stuff. When I fired with forced air, my burners were overloaded with extra
> safety stuff and I also kept a gas generator handy in case of power failure.
>
> If you are firing with propane and want to use venturis, look into the
> "compound injector" designs. These burners will mix air and propane a lot
> better than a single stage venturi. The whole thing with burner design is
> AIR and how to move enough of it thru each burner to get efficient
> combustion. With forced air, you will get all the air you want providing
> you are using an adequate blower and you can also use a lower kiln chimney
> because you don't need as much secondary air.
>
> I'll shut up and let someone else talk, if the Stooges films are over and
> they aren't laughing so hard they can't type.
>
> regards, Craig Martell Hopewell, Oregon
>
Hank Murrow on wed 27 nov 02
On Wednesday, November 27, 2002, at 03:43 AM, Paul Taylor wrote:
> I am starting to realize that my kiln is the most important tool I
> posses.
*** Very good!
>
> I want to cut the secondary air out of my kiln as a variable.
**** It IS possible to do this with inspirating venturi burners.
>
> I still think efficiently mixed primary air should do a
> good job.
**** My experience suggests that flame retention tips properly aligned
with their ports will optimize secondary air mixing whatever the stage
of the firing.........and achieve your stated goal of eliminating a
variable.
>
> As a synopsis of my knowledge so far :--- atmospheric burners
> (venturi)
> made from old pipe are the least efficient.
**** Very true. They really do not meet the criteria for a venturi
design, except within a very narrow range.
>
> Venturi burners with gradual openings helping to mix the gas is what I
> have. I am not sure if a load of little ones is better than a few big
> ones. I know that some of these technologies are better than others :
**** Yes. My experience suggests that the Eclipse Inspirating Mixers
are the best available venturi types. They have compound barrels
available for high pressure propane, BUT I would suggest that you
consider operating your mixers at low (10" wc) pressure. Just as
efficient, but qquiter and with a slightly longer blue flame.
> Again what i suspect is that for every
> size kiln there is a number of burners run at a right pressure giving
> a
> certain flame length with the right amount of secondary air which
> gives an
> optimum kiln firing. the only trouble is, is that I do not know what
> these
> measurements are and I can not afford the experimentation to find out.
I have had the luck to try many setups as a kiln builder (see
http://www.murrow.biz/hank/kiln-and-tools.htm), and it IS possible to
set up a venturi burner system using Eclipse Mixers that meets all of
your criteria.
>
> The next most efficient.....
**** I think those Chinese potters who you admire were not so concerned
about efficiency. BUT.....they were masters of observation and
intelligent response.
>
> For once in my life I am doing this before I build the thing not
> after.
**** You are really giving yourself a break here. Good on you, mate.
>
> I was grateful for Sylvia's post am glad to see that its not just you
> me
> and two lads from Idaho interested in kilns - so I shall post you my
> decisions.
**** Would love to hear about your progress through this project.
GOOD LUCK! Hank in Eugene.
> --
> Regards from Paul Taylor
>
>> FROM CRAIG MARTELL:
>> Hi Paul:
>>
>> Outside of two regular guys from Idaho and a rather inquisitive bloke
>> from Australia,
>> I was totally skunked when I asked.
***** I did respond privately to Craig's questions. We are both in OR.
>> I don't think you need the hi velocity burners if you are going to
>> build a
>> downdraft kiln.
**** I agree.
>> Forced air design is not as difficult as venturis which take
>> some real careful proportion design in the mixer, throat, and exits.
***** True. A very useful alternative which I mentioned to Craig, is to
manifold two or more flame retention tips to a single burner on each
side of the kiln. More bang for the buck (pound).
>> If you are firing with propane and want to use venturis, look into the
>> "compound injector" designs. These burners will mix air and propane
>> a lot
>> better than a single stage venturi. The whole thing with burner
>> design is
>> AIR and how to move enough of it thru each burner to get efficient
>> combustion.
***** Now we are talking. Eclipse makes a very good one, called a
Compound Injector. I think one of these on each side supplying two or
even four small tips would serve you well. These should be used with
cast burner blocks which you can make yourself. These will insure that
the mix of secondary air is proportional at any burner setting.
>> I'll shut up and let someone else talk.
***** So this is Hank in Eugene talking. Please see my webpage
http://www.murrow.biz/hank/kiln-and-tools.htm for a look at my kiln
designs. They use such a system.
Bonnie Staffel on thu 22 apr 04
Dear Clayarters,
I have a friend who wants to change an electric kiln to gas as he was given
an old burner system he would like to adapt. He has placed pictures of the
burners as well as listed some questions he would like your insight in
helping him to achieve this change. He would greatly appreciate your help.
His URL is
http://www.stephenkostyshyn.com/burner/
Thank you very much.
Regards, Bonnie Staffel of Charlevoix, MI.
http://pws.chartermi.net/~bstaffel/default.html
http://www.vasefinder.com/
Jeff Pender on tue 19 jul 05
Helllo! Got a question about kiln/burners. Just built 25 - 28 cu ft
Cant....Firing with propane.
Burners are an issue...I have two venturi (Ensign ribbon burners...ER 4)
Does anybody know about these burners? Will they do the job?...Orifice
looks really small!!!
Thanks for the help!
jeff pender
Marcia Selsor on tue 19 jul 05
Jeff,
I never heard of your burners, sorry.
you need 14,000 BTU's per cubic foot for a soft brick kiln and 30,000
for a hard brick kiln. If you spray with ITC onto soft brick that
would cut your consumption again but I can't say to what.
Figure 14,000 x 28 = 392,000 BTUs per hour. Check the orifice size
and then check a chart from the propane company regarding orifice
sizes. I saw one once so I know they are out there. .
I built some burners with black pipe and steel pipe, bell reducers,
and squirrel cages blowers. Fired a kiln of used hard brick to ^10
with them on 4 100 gallon tanks in tandem
back in 1971 (since Mel is reminiscing) I drilled holes in the 2
inch pipe to insert the 1/4 inch pipe . A small 1/4 inch pipe with 5
holes about 1/64 inch fed the gas into the 2 inch pipe towards the
bell reducer. Used the metal from the top of a coffee can to cut
back the air on the blower.
Marcia Selsor
On Jul 19, 2005, at 12:09 PM, Jeff Pender wrote:
> Helllo! Got a question about kiln/burners. Just built 25 - 28 cu ft
> Cant....Firing with propane.
>
> Burners are an issue...I have two venturi (Ensign ribbon
> burners...ER 4)
>
> Does anybody know about these burners? Will they do the
> job?...Orifice
> looks really small!!!
>
> Thanks for the help!
>
> jeff pender
>
> ___
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