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reduction firing - smokey peeps

updated thu 22 mar 07

 

Lesley Anton on mon 12 mar 07


Hi all,
Reduction firing question here.

I have an 8 year old Laguna Updraft 9 cf fiber gas kiln. I have had
it for about a year and am still learning the ins and outs but have
had quite a few successful reduction firings with it.
Currently, I am having a weird thing happen though. Usually, upon
bringing the gas up slowly to about 3" WC, I get ready to reduce at
about 1650 -1700 F. then close the damper to about 1 1/2", to get my
nice orange, pungent flame. The last 2 firings, there have been a
little flame peek out of the damper even before I shut it. Then when
I go to close the damper, I get my good smell, but then the flame is
a bit small, and there is a bit more smoke than normal. After
playing with the damper, shut not so much as before, I reduced for
about 1/2 hr, then opened it a bit till cone 9ish. During that long
acceleration period, there is way more smoke than normal. I opened
the damper more, then the temp went up way too fast - so I tried
closing the damper again a bit, even with the smoke, then turned the
gas down to 2 1/2", still smokey, then down to 2" - less smoke but
still more than I am comfortable with. The flame is the right size
(I think) and the right color (as per Les Haworth at Laguna and Linda
Arbuckle's entry) I made tiny adjustments )1/4" to 1" with the
damper. When I opened it back up to where it was for oxidation (3")
the smoke is still coming out. Argh! Eeking out of the peeps - both
top and bottom. How much smoke is normal? should I be expecting
some and I am freaking out needlessly? The load didn't seem to be
reduced enough is why I ask.

Upon reading tons of entries, I understand that the smoke is caused
by an imbalance - or a waste - too much reduction - but I am
wondering ,, because I have played around with the balance as much as
I can figure, maybe the smoke is caused by a carbon build up? or
something else? Gas pressure oddity? All the dials read normal.

Help!!



Lesley Anton
www.lesleyanton.com

Lesley Anton on tue 13 mar 07


Thanks for the quick responses,
Sorry, in my panic, I forgot to mention the damper/air situation.
The reason I am so confused is that normally, when kiln starts, I
have the damper set open at 3", then at 1650 F start reducing,
closing the damper to about 1 1/2" , then after 30 min, open back the
damper a bit to about 1 3/4" ......usually the duration of the firing
is a nice 6" orange flame with no smoke....the last 2 firings, no
matter how much I opened the damper back up, even to the starting
position at 3" there was smoke coming out of the top peep hole (when
it was shut), some off the top of the main damper flame and a little
even out of the thermocoupler hole, yikes!. I had never had to open
up that much before.

I understand the whole "wasted fuel," thing and that "the smoke is
not necessary for reduction effects"
I didn't want the smoke, believe me, I just was so freaked about
going out of reduction I was reluctant to continue opening. But I
guess since there was still an orange flame, and not blue/green I
could have kept opening the damper until the smoke stopped. Though,
when I did open it up more, the temp seemed to zoom up too fast.

Eric, I haven't heard about adjusting the burners during the firing.
The discs under my (6) burners are set around 1/2" - maybe they're
open too much? (I guess that wouldn't make sense) I do get a little
uneven reduction though, that might be why.

A friend of mine thought I might have gone up in temperature too
quickly, that might have caused some weird excess smoke/ heat issues
- I also had a very full load, which I don't always have. What is a
good length of time to go from 0 to reduction temp (1650 -1700F)? I
usually take about 5 hours. -is that too short? For all of you
experts out there, what is a typical total cone 10 reduction firing
time - 0 to cone 10?

Gosh, sorry about the 5 million questions in this email - but I just
joined this list and am chomping to know, know, know.

Thanks,
Lesley
www.lesleyanton.com



The
On Mar 13, 2007, at 8:26 AM, Erik Harmon wrote:

> Lesley Anton wrote:
> Upon reading tons of entries, I understand that the smoke is caused
> by an imbalance - or a waste - too much reduction - but I am
> wondering ,, because I have played around with the balance as much as
> I can figure, maybe the smoke is caused by a carbon build up? or
> something else? Gas pressure oddity? All the dials read normal.
>
>
> Lesley you dont say anything about altering your Air intake. Its
> been about ten years, but the Olympic I used to fire in college was
> the same size as yours and with the old burners we had I adjusted
> them at least 3 to 4 times a firing, in order to attain the right
> level of reduction and temp increase.
> ______________________________________________________________________
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> melpots@pclink.com.
>
>
>
>
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>
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> melpots@pclink.com.




Lesley Anton
Owner, designer, potter
Lesley Anton Handmade Ceramic Lighting
323.934.3463
lesleyanton@mac.com
www.lesleyanton.com

Chris Trabka on tue 13 mar 07


Lesley,

I once fired an updraft kiln like yours without an oxyprobe. My suggestion
is to, remove a peep and check the flame coming out of the peep. I
discovered a flame one to two inches long indicated good reduction. I never
had any smoke. The largest problem I had was seeing the flame when it was
bright outside. I cut the bottom and side out of a black 1 gallon plant pot
and used that as a background to see the flame. Little or no flame will
indicate that you are in oxidation, Too much flame (smoke) indicates that
you can either reduce the gas or open the damper.

As a side note, I live in Michigan, and the relative humidity has a
significant impact in my firings. On a sultry August afternoon, my gas is
at 2.5" WC. On a crisp October afternoon, my gas is at 3.5" WC.

Chris

>Hi all,
>Reduction firing question here.
>
>I have an 8 year old Laguna Updraft 9 cf fiber gas kiln. I have had
>it for about a year and am still learning the ins and outs but have
>had quite a few successful reduction firings with it.
>Currently, I am having a weird thing happen though. Usually, upon
>bringing the gas up slowly to about 3" WC, I get ready to reduce at
>about 1650 -1700 F. then close the damper to about 1 1/2", to get my
>nice orange, pungent flame. The last 2 firings, there have been a
>little flame peek out of the damper even before I shut it. Then when
>I go to close the damper, I get my good smell, but then the flame is
>a bit small, and there is a bit more smoke than normal. After
>playing with the damper, shut not so much as before, I reduced for
>about 1/2 hr, then opened it a bit till cone 9ish. During that long
>acceleration period, there is way more smoke than normal. I opened
>the damper more, then the temp went up way too fast - so I tried
>closing the damper again a bit, even with the smoke, then turned the
>gas down to 2 1/2", still smokey, then down to 2" - less smoke but
>still more than I am comfortable with. The flame is the right size
>(I think) and the right color (as per Les Haworth at Laguna and Linda
>Arbuckle's entry) I made tiny adjustments )1/4" to 1" with the
>damper. When I opened it back up to where it was for oxidation (3")
>the smoke is still coming out. Argh! Eeking out of the peeps - both
>top and bottom. How much smoke is normal? should I be expecting
>some and I am freaking out needlessly? The load didn't seem to be
>reduced enough is why I ask.
>
>Upon reading tons of entries, I understand that the smoke is caused
>by an imbalance - or a waste - too much reduction - but I am
>wondering ,, because I have played around with the balance as much as
>I can figure, maybe the smoke is caused by a carbon build up? or
>something else? Gas pressure oddity? All the dials read normal.
>
>Help!!
>
>
>
>Lesley Anton
>www.lesleyanton.com
>
>___________________________________________________________________________
___
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.

William & Susan Schran User on tue 13 mar 07


The smoke is not necessary for reduction effects.
It is unburned fuel/incomplete burned fuel and just a waste of fuel.
Some back pressure at spy holes will indicate reduction, but excess smoke &
carbon at peep holes is not needed.

How do you have the primary air controls (disks on back of burners) set?
Perhaps they are closed too much.

At school, with our downdraft Geil, I have the primary air controls set at
the width of two popsicle sticks. This gives a reduction in the 1800 degree
range simply by adjusting gas pressure.

At home, on my Olympic updraft, I have the air controls set a little more
open (1/4 - 3/8"), but I get uneven reduction, but I continue to work on
that.


--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com



On 3/12/07 6:54 PM, "Lesley Anton" wrote:

> Upon reading tons of entries, I understand that the smoke is caused
> by an imbalance - or a waste - too much reduction - but I am
> wondering ,, because I have played around with the balance as much as
> I can figure, maybe the smoke is caused by a carbon build up? or
> something else? Gas pressure oddity? All the dials read normal.

Erik Harmon on tue 13 mar 07


Lesley Anton wrote:
Upon reading tons of entries, I understand that the smoke is caused
by an imbalance - or a waste - too much reduction - but I am
wondering ,, because I have played around with the balance as much as
I can figure, maybe the smoke is caused by a carbon build up? or
something else? Gas pressure oddity? All the dials read normal.


Lesley you dont say anything about altering your Air intake. Its been about ten years, but the Olympic I used to fire in college was the same size as yours and with the old burners we had I adjusted them at least 3 to 4 times a firing, in order to attain the right level of reduction and temp increase.
______________________________________________________________________________
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You may look at the archives for the list or change your subscription
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Pamela Regentin on thu 15 mar 07


Ivor,

I have an updraft with atmospheric burners. I've only fired once so far. I got good body reduction but so-so glaze reduction. I did close the discs on opposite corners (there are eight burners)during reduction. Without checking my notes I don't remember if it was two or four burners. Anyway, I wondered about the placement of the tops of the burners, the head you called it, which are placed just below the port hole so that there is really no way to control all that secondary air that is mixing with the fuel. Is it correct to have the burner heads just below the port hole and not up into the port hole? Would closing the discs be sufficient to control the air intake there? How many of the burners need to have those discs closed and should any remain open?

I obviously have a lot of experimenting yet to do but your post is the first I have seen that addressed the secondary air at the port holes.

Thanks,
Pam

Ivor and Olive Lewis wrote: Dear Lesley Anton,

You say <>

Those disks or shutters that allow air to mix with your gas before it passes into the kiln need to be closed to some degree prior to adjusting your damper to get back pressure. It is essential that some unburned fuel enters the chamber of a kiln otherwise there is nothing to react with ingredients in clays and glazes .

Another factor that is sometimes overlooked is air that is entrained due to a venturi effect caused by the passage of gas into a kiln and chimney draw . This is secondary air that moves between the burner head and the hole into the kiln chamber. It assists gas to burn on the outside of the flame envelope.

I set my own burners and check by inspecting the flame. I close the shutters until I can see a white tip at the end of the flame. If the flame is all blue then all of the fuel is being consumed so reduction will not happen even if you close the damper and see flame issue from open "peeps". Set with the white tips combustion is almost complete. When I wish to reduce I wind my burner shutters to reduce the air flow, get more white in the flame and then, with the "Peep" open, I close the damper until a small white tip flame issues. The I put the plug back in the "peep". I would close the shutter more but keep the damper setting the same for reducing Copper glazes.

Best regards and Good firings,

Ivor Lewis.
Redhill,
South Australia.

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Ivor and Olive Lewis on fri 16 mar 07


Dear Lesley Anton,=20

You say <The discs under my (6) burners are set around 1/2" - maybe they're open =
too much? (I guess that wouldn't make sense) I do get a little uneven =
reduction though, that might be why.>>

Those disks or shutters that allow air to mix with your gas before it =
passes into the kiln need to be closed to some degree prior to adjusting =
your damper to get back pressure. It is essential that some unburned =
fuel enters the chamber of a kiln otherwise there is nothing to react =
with ingredients in clays and glazes .=20

Another factor that is sometimes overlooked is air that is entrained due =
to a venturi effect caused by the passage of gas into a kiln and chimney =
draw . This is secondary air that moves between the burner head and the =
hole into the kiln chamber. It assists gas to burn on the outside of the =
flame envelope.

I set my own burners and check by inspecting the flame. I close the =
shutters until I can see a white tip at the end of the flame. If the =
flame is all blue then all of the fuel is being consumed so reduction =
will not happen even if you close the damper and see flame issue from =
open "peeps". Set with the white tips combustion is almost complete. =
When I wish to reduce I wind my burner shutters to reduce the air flow, =
get more white in the flame and then, with the "Peep" open, I close the =
damper until a small white tip flame issues. The I put the plug back in =
the "peep". I would close the shutter more but keep the damper setting =
the same for reducing Copper glazes.

Best regards and Good firings,

Ivor Lewis.
Redhill,
South Australia.

Edouard Bastarache Inc. on fri 16 mar 07


Ivor,

"je fume le jambon"--I smoke the ham...

I close the air intakes on my burners, the damper
and the peep holes,
for 20 minutes, and then I reoxidize for 20
minutes after having opened
the damper and the burner air intakes..



Later,



Edouard Bastarache
Le Franšais Volant
The Flying Frenchman

Sorel-Tracy
Quebec
http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
www.thepottersshop.blogspot.com
http://www.ceramique.com/cerambooks/rayons/technologie.php
http://www.flickr.com/photos/30058682@N00/




----- Original Message -----
From: "Ivor and Olive Lewis"

To:
Sent: Thursday, March 15, 2007 9:00 PM
Subject: Re: Reduction Firing - Smokey Peeps


Dear Lesley Anton,

You say <burners during the firing. The discs under my (6)
burners are set around 1/2" - maybe they're open
too much? (I guess that wouldn't make sense) I do
get a little uneven reduction though, that might
be why.>>

Those disks or shutters that allow air to mix with
your gas before it passes into the kiln need to be
closed to some degree prior to adjusting your
damper to get back pressure. It is essential that
some unburned fuel enters the chamber of a kiln
otherwise there is nothing to react with
ingredients in clays and glazes .

Another factor that is sometimes overlooked is air
that is entrained due to a venturi effect caused
by the passage of gas into a kiln and chimney draw
. This is secondary air that moves between the
burner head and the hole into the kiln chamber. It
assists gas to burn on the outside of the flame
envelope.

I set my own burners and check by inspecting the
flame. I close the shutters until I can see a
white tip at the end of the flame. If the flame is
all blue then all of the fuel is being consumed so
reduction will not happen even if you close the
damper and see flame issue from open "peeps". Set
with the white tips combustion is almost complete.
When I wish to reduce I wind my burner shutters to
reduce the air flow, get more white in the flame
and then, with the "Peep" open, I close the damper
until a small white tip flame issues. The I put
the plug back in the "peep". I would close the
shutter more but keep the damper setting the same
for reducing Copper glazes.

Best regards and Good firings,

Ivor Lewis.
Redhill,
South Australia.

______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or
change your subscription
settings from http://www.ceramics.org/clayart/

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reached at melpots@pclink.com.



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Chris Trabka on fri 16 mar 07


Ivor,

I have a modified MFT that has 12 venturi burners (Geil). When I fire the
disks or shutters are all the way down. The flame is all blue in each
burner. I can easily get my oxyprobe reading to 6.4 and the damper
completely out.

I believe burning occurs on the surface of the gas/air mixture. The inner
portion of the gas/air mixture is not burning.

Chris

If the flame is all blue then all of the fuel is being consumed so
reduction will not happen even if you close the damper and see flame issue
from open "peeps".

>Ivor Lewis.
>Redhill,
>South Australia.
>
>___________________________________________________________________________
___
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.

Vince Pitelka on fri 16 mar 07


Ivor Lewis wrote:
Those disks or shutters that allow air to mix with your gas before it passes
into the kiln need to be closed to some degree prior to adjusting your
damper to get back pressure. It is essential that some unburned fuel enters
the chamber of a kiln otherwise there is nothing to react with ingredients
in clays and glazes .

Ivor -
On many kilns equipped with venturi burners, the air shutters are set for
ideal burner operation and are never changed. They only control primary
air, while as you point out, it is the secondary air entering around the
burner tip that allows the flame to combust completely. Thus, by reducing
the damper opening you can often sufficiently reduce the entry of secondary
air to allow unburned fuel to enter the kiln. Different kilns and burners
behave differently, but if one is able to achieve adequate reduction without
changing the shutters, that certainly simplifies things.
- Vince

Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/

Vince Pitelka on sat 17 mar 07


Ivor Lewis wrote:
"One thing I have noted when firing with gas is that when the shutters are
wide open excess air, combined with low gas flow, causes a flame to
"Flashback" to the jet nipple. This is due to the flame velocity being
greater than the gas velocity. Do you experience this when firing commences
with fully open burner shutters ? Or do you progressively open the burner
shutters?"

Ivor -
I have always respected your knowledge and your generosity in sharing, but I
am also very concerned about correct information. The above is opposite my
own experience. Having the shutters open too wide will only admit as much
air as can be entrained by the jet of gas emitted from the orifice, and it
is unlikely that backburning (flame receding back down the burner tube and
burning right at the orifice) would ever be the consequence. The problem in
that case is likely to be flame-off, where the flame blows away from the
burner tip and extinguishes. A proper flame-retention tip will generally
prevent that.

The shortcoming of straight tube burners is that they do not entrain air as
efficiently and do not mix the air and gas as thoroughly through the burner
tube, but either one will work well with a proper flame-retention tip, which
serves simply to create turbulence at the burner tip, mixing the gas and air
so that the flame leaving the burner tip will combust more efficiently.
Secondary air entering around the burner tip is still required for complete
combustion, and inversely, diminishing vacuum within the kiln chamber by
closing the damper will diminshing incoming secondary air, making for
excessive unburned fuel in the kiln.
- Vince

Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/

Ivor and Olive Lewis on sat 17 mar 07


Dear Pamela Regentin,=20

Thanks for your notes. Never had a chance to work with more than two =
burners with either oil or gas. But then I have always built my own =
kilns on a limited budget.

I always keep the head of the burner outside the kiln, so with the =
flames rising vertical I suggest a gap of about one inch between the =
orifice of the burner and the low side of the kiln floor.

I always try to keep both of my burners working in unison. If I had =
eight burners they would always be given identical adjustments. They =
should all sing the same song.

Closing shutters on diagonally placed burners will lead to an uneven =
firing.=20

If the shutters are closed then burning is only supported by the =
secondary air which flows past the burner heads. If the damper is closed =
with this shutter setting you will get free carbon, a very smoky =
atmosphere and lots of soot. You do not need this.

The idea is to create carbon monoxide gas.

During your initial heating set the shutters to give a blue flame with a =
white tip on all of your burners. As you increase your gas flow you may =
need to adjust all of the burner shutters to maintain this kind of =
flame. Set you damper during this period so that air is drawn into the =
kiln chamber through the peephole.

When you reach the temperature at which you wish to reduce your work, =
open the peep. Close the damper a fraction so that there is a small =
flame issuing from the kiln. If it is a clear flame, close all of the =
shutters by one revolution. Observe the effect. If you start to get a =
white tip to the flame you should induce a moderate reduction. A wisp of =
smoke will give more reduction.=20

Remember that adjustments of the damper control secondary air flow.

There may be some who would disagree with my firing program.

There is a wonderful book by Australian Potter Harry Memmott, "An =
Artists Guide to Firing Kilns" a private publication of Victoria =
College, Prahran Campus. It may still be available from "The Artisans =
Bookshop" in Melbourne. Very practical.

All the best,

Ivor Lewis.
Redhill,
South Australia.

Ivor and Olive Lewis on sun 18 mar 07


Dear Vince Pitelka,=20

Good to learn that you had an enjoyable time at the conference.

Now, you tell us...<< On many kilns equipped with venturi burners, the =
air shutters are set for ideal burner operation and are never changed. =
They only control primary
air >>

Yes I know. I have worked with these and was never able to get =
satisfactory reduction even with the Damper partially closed to the =
minimum that will allow fuel to enter the chamber. Burners with a flame =
retention ring but no air shutters seem to be engineered to fire with =
the minimum volume of secondary air.=20

I found them to be a problem when using L.P.G to create an oxygen free =
atmosphere To do this the air inlets were sealed with refractory fibre =
because there was no Bunsen Burner type collar to close and seal the air =
inlets.

Perhaps tuning the whole system is necessary when using burners that do =
not have adjustable shutters, with special attention being paid to the =
area of the burner fire ports. Half an inch in diameter either way can =
make a great deal of difference to the volume of air that will be =
admitted to support total or partial combustion. The distance between =
the burner head and the port also influences the volume of air that is =
admitted into the kiln.

Which seems to suggest that to master the process of firing potters need =
both science and art

Best regards,

Ivor Lewis.
Redhill,
South Australia.

Ivor and Olive Lewis on sun 18 mar 07


Dear Chris Trabka,=20

You tell us... << The flame is all blue in each burner. I can easily get =
my oxyprobe reading to 6.4 and the damper completely out. >> indicating =
that there is a considerable amount of Oxygen passing into the kiln via =
the port apertures as well as that entrained in the gas stream. Perhaps =
you would be willing to describe how you adjust your burners to control =
reduction.

One thing I have noted when firing with gas is that when the shutters =
are wide open excess air, combined with low gas flow, causes a flame to =
"Flashback" to the jet nipple. This is due to the flame velocity being =
greater than the gas velocity. Do you experience this when firing =
commences with fully open burner shutters ? Or do you progressively open =
the burner shutters?

And ...<mixture. The inner
portion of the gas/air mixture is not burning.>> This is the popular =
assumption and I would accept it as a fact applying to a stream of pure =
gas burning in air. It may not be true for a mixture of air and gas =
burning in air since it is possible to demonstrate such a "Flame" has a =
thickness. It is also possible demonstrate that Air will "Burn" in a =
pure gas atmosphere.

When I was doing first year Science we did a lot of spectroscopic =
observations of the common substances that give coloured flames.One of =
the things I noted when recording my observations was groups of fine =
spectral lines in the blue end of the spectrum that seemed to be =
consistent in every test. I asked Dr Hogg about this and was told that =
they were involved with the decomposition of the gas and represented the =
free radicles that were created during pyrolysis and the commencement of =
oxidation of some of the reaction products. This happens inside the =
flame, not at the surface.

Best regards,

Ivor Lewis.
Redhill,
South Australia.

Vince Pitelka on mon 19 mar 07


Ivor Lewis wrote:
"Surely your secondary air would need to be flowing at a very high velocity
to blow a small flame from the burner mouth, for example into a hot kiln
with the damper fully open?"

Ivor -
Thanks for your response and all the good information. Regarding the
statement above, lots of people in North America still use the
"Alfred"-style tube burners, which were crude at best. They had no
flame-retention nozzles, and on such burners, there is very little mixing of
gas and air inside the burner tube. If the velocity of gas and entrained
air exceeds the speed of combustion, the result is "flame-off," where the
flame leaves the burner tip. At lower temperatures, the flame can simply
extinguish itself, but if there is a pilot burner it will re-ignite, but
over time a lot of fuel is wasted. Once red heat exists in the firebox or
flame zone, flame-off is no longer a problem, because all of the gas
combusts, even if the flame is a little ways away from the tip of the
burner. That doesn't happen with a flame-retention tip, and as I am sure
you will agree, flame-retention tips are always a good idea. It doesn't
make any sense to not have them on standard open-port kiln burners.
- Vince

Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/

Chris Trabka on mon 19 mar 07


>
>One thing I have noted when firing with gas is that when the shutters are
wide open excess air, combined with low gas flow, causes a flame
to "Flashback" to the jet nipple. This is due to the flame velocity being
greater than the gas velocity. Do you experience this when firing commences
with fully open burner shutters ? Or do you progressively open the burner
shutters?

Ivor,

I do not change the setting for my shutters. They are always fully open.
My burners are Geil burners. I adjust the atmosphere in the kiln with the
gas preasure and the damper. When the preasure is below 0.5" WC the flame
originates at the jet nipple and has the same look as a candle's flame.
Between 0.75" WC and 1.0" WC the flame moves to the tip of the burner, is
yellow and vibrating, and there is a gentle roar that can be heard. Above
1.0" WC the flame is all blue and the sound from the burners is dimished.

Chris

Kathy McDonald on mon 19 mar 07


Vince ,

I'm glad you clarified this,

"The shortcoming of straight tube burners is that they do
not entrain air as
efficiently and do not mix the air and gas as thoroughly
through the burner
tube, ......................"

Years ago a friend of mine lost his kiln and shed to a bad
fire.
He was using straight tubes for burners with propane.
Apparently the fire/explosion was caused by an improper mix
of
air and fuel in the burners that resulted in a build up of
unburned
propane that ignited.

I was a neophyte at the time and in the process of
building and learning to fire my first kiln.

The fire scared me.

It made me rethink my design and contact a fellow named
James Clackery
who built the burners I used.

His recommendation at the time was to add some height and
two dampers to my chimney , one low on the chimney
and another a bit higher up allowing for better control
of secondary air input at the damper as well as the air
intake
wheels on the burners.
That kiln has since been retired but the burners live on
in another kiln.


Kathy











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Ivor and Olive Lewis on tue 20 mar 07


Dear Vince Pitelka,=20

My burners are not home made, but commercial products from a company =
that specialises in gas engineering. So they do have flame retention =
devices and safety features.

Have to be careful with terms because of cultural and regional =
differences. "Backburning" is a process used by our Fire Officers to =
create a line lacking in combustibles in advance of a fire front. Very =
dangerous job!=20

My Oxy welding kit has "Flashback Arrestors". Hence my preference for =
that term. Perhaps "Backfire" would be a compromise. Any noise is due to =
a high flame velocity, creating a shock wave with a velocity somewhere =
near 350 m.p.s. A flame can travel very fast without making any sound.

Surely your secondary air would need to be flowing at a very high =
velocity to blow a small flame from the burner mouth, for example into a =
hot kiln with the damper fully open ?

Best regards,

Ivor Lewis.
Redhill,
South Australia.

Ivor and Olive Lewis on wed 21 mar 07


Dear Vince Pitelka,=20

I appreciate your explanation of the Alfred Burner. Seems to be nothing =
more than an overgrown Bunsen Burner. Without a doubt invention of flame =
retention devices makes a big difference to stability of a flame.

Yes, if the kiln temperature is above the flash point of the gas, which =
is somewhere round about 600 deg C, as you say, red heat, then it will =
burn as it passes around the ware.

Thanks for the conversation.

Best regards,

Ivor