Frances Pusateri on tue 8 aug 00
The kiln: Interior size of base is approximately 16" wide x 22" long x
10" deep, hard brick exterior w/ soft brick interior. Cover is
approximately 24" interior diameter x 24" high with 5" flue, expanded
metal frame with two overlapping layers of fiber blanket. The 12" x =
20"
shelf is approximately 8" above the floor. The burners are homemade =
and
consist of a =BD " pipe capped with an appropriately sized nozzle for
natural gas. They are inside an 8" long piece of movable 2" diameter
pipe. The burner ports are slightly larger than the 2" pipe.
Changes to Kiln in Last year: I've been firing this kiln for about 8
years now with no problems. In the past year, there have been a few
changes including: base was rebuilt, converting the old hard brick =
base
to a base with a hard brick exterior and soft brick interior while
maintaining the same inside chamber size. The burner ports are =
slightly
smaller than they were previously and the kiln base is much tighter =
than
before. The kiln yard was paved with cement and ground level is now
even with the bottom of the burner ports whereas before it was a couple
of inches below the bottom of the burner ports. Prior to the =
previously
listed changes, the burners on the kiln were fired using fans (look =
like
metal hair dryer with directional nozzle) to force air into either in
one or both burner ports to fire to cone 05 in 15 to 20 min once the =
old
hard brick interior of the kiln was warmed up. =20
The Problem: Currently, I'm having problems keeping the burners lit,
even after the kiln has heated up. It is impossible to use the fans on
the burners and unless the burner ports are mostly covered, the burners
won't stay lit. The kiln is in moderate reduction all the time and
firing times are more like 45 minutes. What I have observed is that
prior to lowering the cover, the burners burn blue right back to the
nozzle. As I close the cover, the blue flame separates from the =
nozzle,
fluttering approximately 3 - 4" in front of the nozzle and frequently
going out. Aside from the fact that the kiln is not firing efficiently
and loosing heat from constantly having to open to relight the burners;
it must be constantly monitored in case one of the burners blows out =
and
allows gas to build up. I have cleaned the nozzles and cleared all
debris from the 2" pipes that enclose the nozzles (in days of old
sometimes spider webs had blocked the nozzles causing problems).
Does anyone have any suggestions? I will be teaching a 2 week raku
workshop starting August 21st and need to get this resolved.
TIA,
Francie
=20
Frances M. Pusateri
Colorado Division of Wildlife
317 W. Prospect
Fort Collins, CO 80526
(970)472-4336
(970)472-4458 FAX
francie.pusateri@state.co.us
Ken Kang on wed 9 aug 00
Francie,
If you are using a forced air burner, and the fan is always on, you do no=
t
need secondary air from your burner port. If you do not have a control fo=
r
your fan or your incoming air, I would suggest when you start, block off=
most of the opening on the fan intake then light your burner. Then as yo=
u
increase the gas, increase the opening. This should stop the flame from
separating from the burner nozzle.
Another beautiful day in Hawaii.
Aloha, Ken
Richard Jeffery on wed 9 aug 00
Have you calculated area of air intake around burners in relationship to
area of flue? [you don't say how many burners there are, unless I missed
something].
If you have reduced burner port size, and reduced secondary air that might
have been coming in through a looser floor, there may not be enough for
combustion? Not sure from description, but it seems that burners are inside
kiln? [sorry - it's a detailed description, but I still can't visualise
it...]. I have a similar if smaller kiln, with one largish burner outside
the kiln, so plenty of scope for secondary air to be drawn in around the
flame. This is propane, though, so not sure what difference natural gas
might make.
Hope this of some help as a starting point - I'm sure the real kiln gurus
will sort you out...
Richard
Bournemouth UK
www.TheEleventhHour.co.uk
> >-----Original Message-----
> >From: Ceramic Arts Discussion List
> >[mailto:CLAYART@LSV.CERAMICS.ORG]On
> >Behalf Of Frances Pusateri
> >Sent: 08 August 2000 16:11
> >To: CLAYART@LSV.CERAMICS.ORG
> >Subject: I Need Help With Raku Kiln
> >
> >
> >The kiln: Interior size of base is approximately 16" wide x
> >22" long x
> >10" deep, hard brick exterior w/ soft brick interior. Cover is
> >approximately 24" interior diameter x 24" high with 5" flue, expanded
> >metal frame with two overlapping layers of fiber blanket.
> >The 12" x 20"
> >shelf is approximately 8" above the floor. The burners are
> >homemade and
> >consist of a ½ " pipe capped with an appropriately sized nozzle for
> >natural gas. They are inside an 8" long piece of movable 2" diameter
> >pipe. The burner ports are slightly larger than the 2" pipe.
> >
> >Changes to Kiln in Last year: I've been firing this kiln for about 8
> >years now with no problems. In the past year, there have been a few
> >changes including: base was rebuilt, converting the old
> >hard brick base
> >to a base with a hard brick exterior and soft brick interior while
> >maintaining the same inside chamber size. The burner ports
> >are slightly
> >smaller than they were previously and the kiln base is much
> >tighter than
> >before. The kiln yard was paved with cement and ground level is now
> >even with the bottom of the burner ports whereas before it
> >was a couple
> >of inches below the bottom of the burner ports. Prior to
> >the previously
> >listed changes, the burners on the kiln were fired using
> >fans (look like
> >metal hair dryer with directional nozzle) to force air into either in
> >one or both burner ports to fire to cone 05 in 15 to 20 min
> >once the old
> >hard brick interior of the kiln was warmed up.
> >
> >The Problem: Currently, I'm having problems keeping the burners lit,
> >even after the kiln has heated up. It is impossible to use
> >the fans on
> >the burners and unless the burner ports are mostly covered,
> >the burners
> >won't stay lit. The kiln is in moderate reduction all the time and
> >firing times are more like 45 minutes. What I have observed is that
> >prior to lowering the cover, the burners burn blue right back to the
> >nozzle. As I close the cover, the blue flame separates from
> >the nozzle,
> >fluttering approximately 3 - 4" in front of the nozzle and frequently
> >going out. Aside from the fact that the kiln is not firing
> >efficiently
> >and loosing heat from constantly having to open to relight
> >the burners;
> >it must be constantly monitored in case one of the burners
> >blows out and
> >allows gas to build up. I have cleaned the nozzles and cleared all
> >debris from the 2" pipes that enclose the nozzles (in days of old
> >sometimes spider webs had blocked the nozzles causing problems).
> >
> >Does anyone have any suggestions? I will be teaching a 2 week raku
> >workshop starting August 21st and need to get this resolved.
> >
> >TIA,
> >Francie
> >
> >Frances M. Pusateri
> >Colorado Division of Wildlife
> >317 W. Prospect
> >Fort Collins, CO 80526
> >(970)472-4336
> >(970)472-4458 FAX
> >francie.pusateri@state.co.us
> >
> >_____________________________________________________________
> >_________________
> >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.
> >
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