Theo Helmstadter on fri 16 mar 07
I just built the MFT described in the Mel Jacobsen/Kurt Wild article
(http://www.potterymaking.org/FlattopKiln_Complete.pdf). Construction was
straight-forward, but my initial firing to cone 06 took 10 hours with high-
pressure propane. The kiln is 22 cubic feet inside, with a 10 foot
chimney. How important is the furniture/flameway/target brick
arrangement? This aspect was unclear to me from the article.
Thanks for any tips or insights!
Theo Helmstadter
www.greenriverpottery.com
Lori Leary on sat 17 mar 07
Hi Theo,
What was your gas pressure?
Lori L.
Theo Helmstadter wrote:
> I just built the MFT described in the Mel Jacobsen/Kurt Wild article
> (http://www.potterymaking.org/FlattopKiln_Complete.pdf). Construction was
> straight-forward, but my initial firing to cone 06 took 10 hours with high-
> pressure propane. The kiln is 22 cubic feet inside, with a 10 foot
> chimney. How important is the furniture/flameway/target brick
> arrangement? This aspect was unclear to me from the article.
>
> Thanks for any tips or insights!
>
> Theo Helmstadter
> www.greenriverpottery.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.
>
>
>
Jennifer Boyer on sat 17 mar 07
We need your burner size, orifice size and gas pressure range during
the firing, as well as chimney diameter. Oh and propane tank size and
what temp it was outside that day.
Jennifer
On Mar 16, 2007, at 2:55 PM, Theo Helmstadter wrote:
> I just built the MFT described in the Mel Jacobsen/Kurt Wild article
> (http://www.potterymaking.org/FlattopKiln_Complete.pdf).
> Construction was
> straight-forward, but my initial firing to cone 06 took 10 hours
> with high-
> pressure propane. The kiln is 22 cubic feet inside, with a 10 foot
> chimney. How important is the furniture/flameway/target brick
> arrangement? This aspect was unclear to me from the article.
>
> Thanks for any tips or insights!
>
> Theo Helmstadter
> www.greenriverpottery.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.
*****************************
Jennifer Boyer
Thistle Hill Pottery
Montpelier, VT
http://thistlehillpottery.com
*****************************
Theo Helmstadter on sat 17 mar 07
Hi Lori,
I started the firing with 2 lbs. propane, and 2 MR750 burners: 76,880 btu/hr
each. By 1500 degrees fahrenheit, I was up to 3 lbs. pressure and had
switched to a pair of MR100 burners: 118,850 btu/hr each. This seemed like a
lot to me, so I wonder if there is a certain target brick arrangement that
will make a big difference.
Thanks for your email--
Theo
At 11:38 PM 3/16/2007, you wrote:
>Hi Theo,
>What was your gas pressure?
>Lori L.
>
>Theo Helmstadter wrote:
>>I just built the MFT described in the Mel Jacobsen/Kurt Wild article
>>(http://www.potterymaking.org/FlattopKiln_Complete.pdf). Construction was
>>straight-forward, but my initial firing to cone 06 took 10 hours with high-
>>pressure propane. The kiln is 22 cubic feet inside, with a 10 foot
>>chimney. How important is the furniture/flameway/target brick
>>arrangement? This aspect was unclear to me from the article.
>>
>>Thanks for any tips or insights!
>>
>>Theo Helmstadter
>>www.greenriverpottery.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.
>>
>>
>
>______________________________________________________________________________
>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.
shane mickey on sun 18 mar 07
theo,
a 22 cu ft soft brick kiln firing with mr100 or mr 750 burners would need much higher pressure than what you describe to get up to temp. was your ending pressure with the mr100s 3 pounds? if so this may be the culprit, i have used mr100s on a 30 cu ft reduction kiln and they get top btu's at 18lbs of pressure, so even for bisque you would need to be half way to 18 lbs. your stack sounds high enough if its 18" square inside. target/bagwall can slow down a firing if it directly impedes the flame path, but most likely it usually just cuases the kiln to fire unevenly. so questions are: do you know what pressure your regulator on the tank is set at? is it at least a 500 gallon tank? what were your damper settings (passive or active dampers)? It may have seemed like alot of pressure due to the sound, those little mr burners get really loud! almost scary loud. hope this helps
shane
shane mickey pottery and kiln design services
828-688-6982
_______________________________________________
Join Excite! - http://www.excite.com
The most personalized portal on the Web!
Kurt Wild on mon 19 mar 07
Theo:
I would have responded sooner but i don't read Clayart every day.
I wish you would have contacted me or Mel directly.
Anyway, there is no need for a target brick in the flameway -
I don't use one and we don't use any at Hay Creek.
I do use a slanted brick at the end of the flameway to deflect the flame
upward.
You said: "my initial firing to cone 06 took 10 hours with high-
pressure propane"
Were you up to or on 3 lbs with the MR100's after the switch?
How long?
I'm not sure I can give you a good answer on the gas pressure because
I don't know anything about your burners. However you do have sufficient
BTU input with the "118,850 btu/hr each".
My burners are rated at about 122,000 BTU/burner and I fire propane at 9" WC.
I candle overnight and reach 1000 degrees F. by morning.
Then I crank it up and reach cone 9 reduction in 4 to 4-1/2 hours.
A friend that has Nils Lou burners fires propane at 3 lbs max. I think a
lot depends on your burners
as to what gas pressure you use. At Hay Creek we often use Big Bertha weed
burners at 25 to 30 lbs but
adjust it at the burners.
Have you called Marc Ward and asked him about operating pressure for the
MR100 burners?
Your 10 foot stack is just right - same as mine.
Another thought - often the answer to not reaching temp is that people tend
to pour in more gas when they should be
using less - you can be choking it with too much gas. Try cutting back on
your gas pressure.
Kurt
Kurt
Vince Pitelka on mon 19 mar 07
Shane Mickey wrote:
"a 22 cu ft soft brick kiln firing with mr100 or mr 750 burners would need
much higher pressure than what you describe to get up to temp. was your
ending pressure with the mr100s 3 pounds? if so this may be the culprit, i
have used mr100s on a 30 cu ft reduction kiln and they get top btu's at
18lbs of pressure, so even for bisque you would need to be half way to 18
lbs. "
Shane -
I am a little concerned about the above advice. Our current 20-cubic-foot
soda kiln is hardbrick, and we use three MR-100s, and get to cone 10 very
easily without ever turning the LPG pressure higher than 10 lbs.
Previously, we went through a series of softbrick soda kilns lined with ITC.
They didn't hold up well under heavy use, but they fired to cone 10 just
fine on two MR-100s without turning the pressure up past 5 or 6 lbs. For a
bisque-firing in a 22 cu.ft. IFB kiln with two MR-100s, you shouldn't need
more than two or three pounds of pressure.
I'm kind of horrified at the thought of firing a kiln with MR-100s on 18
lbs. of LPG. You'd have to wear hearing protectors when you get near the
kiln. I'm assuming that this was with just two MR-100s, and far better to
use four or six burners and turn the pressure WAY down.
I think that people underrate the MR-100s. On the 40-cu. ft. natural gas
car kiln I designed for Michael McDowell, I specified four MR-100s. Michael
talked to Marc Ward, who told him he needed six MR-100s, so I redesigned the
kiln to have three burner ports on each side. Michael did a beautiful job
of building the kiln with the six burners. On the first firing, two
thermocouples were apparently defective and failed, and Michael fired the
kiln to cone 10 with no problems on four of the burners. It's always nice
to have extra power. Remember that this was on standard household natural
gas - seven water column inches of pressure - that's 1/4 of 1 PSI.
I think that the MR-750 and MR-100 work more effectively on lower pressures.
At high pressures I think that they are less efficient, and they are
certainly very noisy. That's been my experience in using them on about a
dozen different kilns.
- 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/
| |
|
