John Baymore on tue 26 sep 00
I see that of the four devices you mention, two I have never heard of:
flowmeters and flue analyzers. I suspect I'm not the only one in the dark=
here - would you please tell us what they are?
Sorry about that. I'll try to switch the power back on. It'll probably =
be
a dim bulb .
A flow meter is a device that can be put into a gas (any type) supply lin=
e
that gives you a VERY accurate reading of the VOLUME of material (cfm)
going through the line. So you can know how many cfm are running at any
point in time. There are numerous types of displays of the volume
available ....some are digital (big $). This is a standard industrial ty=
pe
piece of instrumentation....... (industry likes control of variables )=
.. =
Simply because they cost a bit to install....you don't find them in too
many handcraft pottery situations.....because of the "percieved cost" (se=
e
below). With flow meters on air and gas supplys you can pretty easily
determine very precise volume relationships....which gives you really goo=
d
control over atmospheric conditions in the kiln, as well as precise heat
input figures. None of these flowmeter units appear "cheap" or "a good
deal" to most potters. They usually quickly compare them to a simple gas=
"pressure guage"....and opt for the less expensive guage....thinking it'l=
l
give the same level of control or information. =
Not typically the device for the "casual" potter....unless money spent
really isn't an issue at all. Great device for a production oriented
studio. They can result in great fuel savings which can pay for them
pretty quickly if you fire a lot. Good device to think about having in
degree granting schools on at least one kiln though ....... teaching
environments should proivide a wide range of experiences whenever
possible...... you never know where a student will end up.
Although you can get them many places..... the most convenient one stop
shopping source for much "kiln equipment" for potters is now Ward Burner
Systems (TN) since my friend Harry Dedell (Dedell Burner, VT....formerly =
of
Cutter Ceramics, MA) has finally retired. Marc (Ward Burner) carries
flowmeters (Waukee brand) in his catalog...... they range in price there
from about $425.00 to $550.00. You'll find them on the same page with
pressure guages that sell for $7.50 to 43.50. Lacking a full understandi=
ng
of the difference of the two items...... most look a the two prices and o=
pt
for the guages . Marc makes an attempt in the catalog to explain the
different functions..... but my experience is most people can't seem to g=
et
beyond the price issue for this type of stuff.
I bet when Marc sells them it takes him some detailed explaining to "clos=
e"
the sale . Unless the purchaser already knows a lot about kiln
technology before they call.
-------------------------
ASIDE: By the way...... Harry Dedell retiring is a great loss to the
pottery community. Harry was a wonderful resource and had a wealth of
knowledge. He ran New England Ceramics and Kiln Supply in CT before it w=
as
aquired by Cutter Ceramics...and then was a driving force with Cutter up
until near the last breath of that company. He was a tireless helper for=
people struggling with ceramic technical issues in the whole eastern
USA.....and elsewhere too. Harry is missed from the ceramics scene by
those who knew him and depended on him. =
-------------------------
I used the term "Flue gas analizers" in the last posting somewhat
inclusively to include both what is often called by potters an "oxyge=
n
probe" as well as the wet chemical type emissions testing units like the
Fyrite unit. These devices allow you to sample the kiln atmosphere and
pretty accurately determine the level of reducing agents present. =
Atmospheric conditions are harder to judge without instruments than
temperature. One type uses an electronic probe to drive a digital
numerical display and the other uses a little pump to send some kiln gase=
s
into a chemical chamber that causes a volume change reaction that can be
read on a calibrated scale. In the end you get the same result.....more
easily gained, repeatable, accurate information. The digital "oxy-probe"=
is slicker and more convenient than the other ...and a bit more
accurate. The digital is quite a bit more expensive too......usually
$700-800.00 to the chemicals $300.00 -ish.
Most large pottery supply companies sell both of these units...... I don'=
t
think Ward Burner does.... but check with them too.
You can also get the Fyrite chemical method units (and replaceable
supplies) from your local porfessional plumbing and heating supply
company..... talk to your oil burner service technician. But you'll need=
some additional info about how to use them. I wrote the user manual on
using them with ceramics kilns for Cutter Ceramics many, many years
ago.....you might still find a copy of that handbook lying around somewhe=
re
.....or get the old Studio Potter article by George Wetlauffer (sp?). Bot=
h
have useful charts for the potter. If I remember correctly Wetlauffer's
article was reprinted in "The Energy Efficient Potter" by Regis Brodie mu=
ch
later.
These gas sensing units are INCREDIBLY valuable as a learning aid.......
not to mention as a production control device. They can help "shortcut"
many years of "seat of the pants" firing experience in learning what is
happening. I have shown this following example numerous times in teachi=
ng
college kiln design courses for the past 25 years or so. It is a bit of =
an
eye opener. =
Take a gas kiln in at a point it should be in reduction. Have a person
adjust the kiln to certain "level" of reduction by their usual "by eye"
(which probably includes numerous other senses...as already mentioned =
)
methods. Take a reading with the oxyprobe or the Fyrite device. Record
the numbers. Then have the person who just adjusted the kiln leave the
room while you take the kiln out of reduction and "screw up" the balance
quite a bit. (A few minutes of "out of whack" at most points in the firin=
g
won't ruin anything .) Have them then come back in and attempt to
duplicate exactly the reduction conditions they had just themselves set
previously. Take a reading again. More often than not the readings are
significantly different even if the kiln has some of the typically used
"potter quality guages" or calibrations on air and gas (which often are
pretty inaccurate devices ....but they were cheap ). =
The more experienced a person is, the closer they will get....but even
experienced firers often have great difficulty with this task. If they a=
re
not "familiar" with the particular kiln....say, the like one they fire al=
l
the time....... they have even more trouble . Most are quite surprise=
d
by the results.
This little "experinment" is even more enlightening when you have a highl=
y
experienced firer "show" someone else who's not fired much before how to
get the conditions "just right" for proper reduction. Which unfortunatel=
y
is the typical way kiln firing is usually taught . In this test, let
the experienced person communicate how to tell if the kiln is in the prop=
er
condition to another less experienced person. Read whatever guages or
calibrations or whatever....look at whatever flame length or color where
ever....smell whatever smell..... kick whatever specific spot on the side=
of the unit , and so on. Take a reading. Again, knock the kiln "out =
of
whack". Have the "learnee" now adjust the kiln (with no help) to the exa=
ct
conditions they have just been taught to create. Take a reading. A lar=
ge
portion of the time it'll be WAYoff.
And we wonder why we often get different results, load to load, person to=
person, or from one kiln to another kiln .
There are LOTS of visual, auditory, olfactory, and other sensory clues th=
at
a highly experiened person takes into account (consciously or
unconsciously) when they adjust kilns. It takes a lot of "cause and
effect" relationships to be established to gain this knowledge. Oftentim=
es
this is gained through a LOT of firings....and alot of "oh craps" upon ki=
ln
openings . Instrumentation can help cut down the number of "oh craps"=
necessary .
It certainly is possible to learn to fire "by eye".....because countless
generations of potters did so quite nicely, thank you. But tools can hel=
p
speed the learning process and help keep you from going off down "blind
alleys" (wrong conclusions about cause / effect relationships). =
A caveat...... never become so dependent on tools that you completely
disregard common sense and what your own senses are telling you is
happening. If there is a descrepancy between machinery and
senses..........THINK about it carefully. There are many dead aircraft
pilots who believed their instruments completely in IFR (instrument flyin=
g)
conditions as they saw the mountain goat looming in the windshield . =
Use tools to help learn....but remember your most important tool is your
brain.
While I'm "on a roll" here ...... a little subject sort of alluded to
above....... accuracy of measuring devices....... which leads to
...........cheap tools. Ah....... nothing like cheap tools. Save a bundl=
e
so you can screw up a fortune . Great example..... a "cheap" guage o=
f
some sort. "Cheap" usually means more inaccurate. That is how they are
often made cheaply. Accuracy usually costs more. But...... if you can't=
depend on the readings you are getting....... what did you save? Buy th=
e
good one. Yes, it'll probably be more expensive up front. But what is a=
single kiln load of pots worth? One blown load of pots caused by a guage=
that is plus or minus a huge percentage in it's abilty to resolve what it=
is measureing .....and you could have bought a gazillion of the expensive=
guages.
Example: Buy a "cheapie" analog $90.00 pyrometer as opposed to the
"expensive" digital $250.00 one. Now believe the analog display when it
says the kiln is at 225 F. From that belief, assume you are now past the=
danger zone for formative H2O issues because the meter says you're good t=
o
go......and increase your firing rate. Blow up a few $100.00 teapots. N=
et
result...... frustration, some nice landfill, valuable time lost (which i=
s
the REAL issue in pricing handcraft), and the development of the erroneou=
s
belief that it couldn't have been water issues because you were at
250F.....what could have caused this ? Oh......and a wasted $90.00.=
The "cheaper" pyrometer would have been the digital one.....cost less the=
the blown up pots.
Details matter. Another example in the same vein...... a cheap analog
meter movement..... fine print says ........ " +/- 2% full
scale".................... sounds insignificant. Only 2 percent. Right!=
=
Two percent of 2500 (full scale) degrees F is 50 degrees F. So a reading=
of 225 F could be anywhere from 175 to 275 degrees F. If you are a
molecule of liguid water waiting to change to vapor..... that two percent=
means a lot . Also remember...... that figure is the resolution of th=
e
meter movement all by itself, not the whole "system" (meter, extension
wire, cold joint compensation, thermocouple, and so on). Add the little
inaccuracies of it all up, and the accuracy could be even worse. When
buying instrumentation ........ ask about those little "plus and minus"
figures so you know what you are getting.
Understand what a proposed tool can and can't do. To paraphrase Clint
Eastwood ..... " A (wo)man's gotta know his/her limitations."
WOW....... sorry...that got long.
=
Best,
........................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752 (s)
800-900-1110 (s)
JBaymore@compuserve.com
John.Baymore@GSD-CO.com
"Earth, Water, and Fire Noborigama Woodfiring Workshop August 18-27,
2000"
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