Vince Pitelka on mon 28 may 12
Jeff Lawrence wrote:
I don't really want to adjust the air shutters during the firing - I figure=
d
I should get the right setting for my maximum desired gas setting (a little
less than half) and just let them be inefficient at other pressures. But ho=
w
can I tell what's efficient when more air makes no never-mind? Speak,
cognoscenti, and enlighten my darkness!"
Hey, Jeff, your burners are already enlightening your darkness. That's wha=
t
they do. Seriously, you can control the richness or leanness of the flame
with the primary air shutters, but it has little impact on kiln atmosphere,
and what you really want to do is find the happy medium and leave them
there, never changing primary air shutter settings during the firing, makin=
g
all changes in atmosphere using the damper.
As you have discovered, closing them too far produces an inefficient orange
flame with insufficient primary air. Opening them too far produces a
noisier flame that is excessively oxidizing. Having flickers of orange in
the flame is fine. It should be a long, quiet flame that is all blue or
blue with flickers of orange. If it becomes a short blue flame, there is
too much primary air and it is an inefficient flame.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
Hank Murrow on mon 28 may 12
On May 28, 2012, at 10:23 AM, Jeff Lawrence wrote:
> Hi,
> After making the discovery that natural draft burners don't work well =3D
with
> gobs of mortar over the gas orifices, I realized I have no idea what =3D
to do
> with the air shutters.
> So, with the kiln door open and burners on, I started monkeying with =3D
them.
> All the way shut gives an orange flame that just looks wrong and =3D
opening
> the shutters about three revolutions gives a lively-looking blue flame =
=3D
with
> ever-decreasing bits of orange at the tip.
> Great, I thought. If I can adjust them just right, I'll get a flame =3D
like a
> Bunsen burner on steroids.
> No joy, though. Opening the shutters past that first point of vigorous =
=3D
blue
> with hints of orange had little perceptible effect. Highly =3D
unsatisfying.
> I don't really want to adjust the air shutters during the firing - I
> figured I should get the right setting for my maximum desired gas =3D
setting
> (a little less than half) and just let them be inefficient at other
> pressures. But how can I tell what's efficient when more air makes no
> never-mind?
> Speak, cognoscenti, and enlighten my darkness!
Cognoscenti Here!
Note: When the kiln is closed up and firing, the draft will kick in and =3D
the flame will be very blue and hot at 3 turns of air. Burners don't =3D
work correctly without their intended kiln. Start with 1/2 turn air and =3D
1/2" wc gas, increasing by 1/2 turns and 1/2" wc until full on. Should =3D
take around 4 to 5 hours. Reduce as needed/decided upon.
The damper will need corresponding adjustment to tune for clean(the =3D
correct balance between adequate draft & too much secondary air)firing =3D
until reduction.
When the firing is finished, shut the air entirely, and wait for orange =3D
reflections on the floor, indicating that the system is purged of =3D
air____ then turn off the gas and damper the kiln. You should get no =3D
"pop" from air in the manifold.
Wait until kiln is below 250F and peek!
Cheers, Cognoscenti #1=3D
Jeff Lawrence on mon 28 may 12
Hi,
After making the discovery that natural draft burners don't work well with
gobs of mortar over the gas orifices, I realized I have no idea what to do
with the air shutters.
So, with the kiln door open and burners on, I started monkeying with them.
All the way shut gives an orange flame that just looks wrong and opening
the shutters about three revolutions gives a lively-looking blue flame with
ever-decreasing bits of orange at the tip.
Great, I thought. If I can adjust them just right, I'll get a flame like a
Bunsen burner on steroids.
No joy, though. Opening the shutters past that first point of vigorous blue
with hints of orange had little perceptible effect. Highly unsatisfying.
I don't really want to adjust the air shutters during the firing - I
figured I should get the right setting for my maximum desired gas setting
(a little less than half) and just let them be inefficient at other
pressures. But how can I tell what's efficient when more air makes no
never-mind?
Speak, cognoscenti, and enlighten my darkness!
Thanks,
jeff
Rimas VisGirda on tue 29 may 12
Jeff writes:
No joy, though. Opening the shutters past that first point of vigorous blue
with hints of orange had little perceptible effect. Highly unsatisfying.
I don't really want to adjust the air shutters during the firing - I
figured I should get the right setting for my maximum desired gas setting
(a little less than half) and just let them be inefficient at other
pressures. But how can I tell what's efficient when more air makes no
never-mind?
Speak, cognoscenti, and enlighten my darkness!
Jeff, not a cognoscenti, just remembering that when I had gas kilns the air=
shutters (primary air) were open just enough to not have that dirty yellow=
flame and stayed that way for the life of the firing (and of the kiln). Th=
e reduction and length of flame was controlled by adjusting the secondary a=
ir with the damper. -Rimas
Ben Morrison on tue 29 may 12
I use primarily forced air burners in college. With those I was taught to o=
pen the air until the burner begins to pop or blows out and then turn it ba=
ck down until that stops. With venturi burners on our big gas kilns in coll=
ege we would open them until the flame was full blue.
-Ben
________________________________
From: Rimas VisGirda
To: Clayart@LSV.CERAMICS.ORG
Sent: Tuesday, May 29, 2012 4:53 AM
Subject: air shutters on venturi burners
Jeff writes:
No joy, though. Opening the shutters past that first point of vigorous blue
with hints of orange had little perceptible effect. Highly unsatisfying.
I don't really want to adjust the air shutters during the firing - I
figured I should get the right setting for my maximum desired gas setting
(a little less than half) and just let them be inefficient at other
pressures. But how can I tell what's efficient when more air makes no
never-mind?
Speak, cognoscenti, and enlighten my darkness!
Jeff, not a cognoscenti, just remembering that when I had gas kilns the air=
shutters (primary air) were open just enough to not have that dirty yellow=
flame and stayed that way for the life of the firing (and of the kiln). Th=
e reduction and length of flame was controlled by adjusting the secondary a=
ir with the damper. -Rimas
POST, JOHN on tue 29 may 12
Vince wrote-
As you have discovered, closing them too far produces an inefficient =3D
orange
flame with insufficient primary air. Opening them too far produces a
noisier flame that is excessively oxidizing. =3D20
--------------------------------------------
I used to fire Raku with my students using a Ward Burner set up on a =3D
variety of converted electric kilns.
I never noticed a point where I would open up the primary air spin plate =
=3D
and get an over-oxidizing flame. =3D20
Maybe I missed seeing/hearing that point.
I did notice that if I opened up the primary air plate from the closed =3D
position that you could hear the flame get louder.
It seemed to me that the minute I opened the spin plate up a little to =3D
about a 1/4 - 1/2 of an inch gap between it and the burner,=3D20
the sound of the flame would increase, but opening the spin plate as far =
=3D
as it would go did not make the volume keep increasing.
I never really thought about an over-oxidizing flame. I must have been =3D
working under the assumption that once the primary air plate was fully =3D
open
that the burner was at its peak efficiency. =3D20
Hmmmmmmmm... Now I'm going to have to think about this and take a look =3D
at the burners and sound of the flames when I fire my Olympic updraft =3D
this weekend=3D20
and listen carefully the next time I fire Raku with my students.
Lee on wed 30 may 12
On Tue, May 29, 2012 at 1:00 PM, POST, JOHN wrote:
=3DA0Now I'm going to have to think about this and take a look at the
burners and sound of the flames when I fire my Olympic updraft this
weekend
> and listen carefully the next time I fire Raku with my students.
Would LPG and Natural Gas be different? More pressure with LPG?
--=3D20
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
wynpotter on fri 1 jun 12
I can only speak for my firing an I'm sure others have other methods.
I have a 40 cu ft(stacking area) kiln that has 6 raku burners, 3 on a
side,fed by approx .5lb pressure each. I don't have gauges on each, but
like Lee listen to the sound of the burners.
At the beginning of the firings, I keep the PAPs(Primary Air Ports)
backed off so the air comes in with max air mix.
At 1500 deg F. which is the beginning of reduction for me I close the
PAPs all the way in and then back them off 1 turn.
At the same time I push in the damper till I get a back pressure flame
from the bottom peep.
As the temp rises I adjust the damper to keep the flame at the same
level, leaving the PAPs at the same place.
As the kiln heats up to 1800 deg I adjust the damper again, keeping
reduction without stalling the kiln.
At around 2100 deg I open the PAPs a quarter turn and at cone 6 another
quarter turn, where it stays for the rest of the firing.
I control the reduction with the damper as i see the bottom peep indicates.
My valves on each burner are about half open but I gauge this by sound.
Hope this helps Wyndham
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