mel jacobson on wed 6 jul 05
it has happened to me twice.
that was before i installed the 220v light
above my desk. (for the janitor to see)
the problem:
the height of a throwing stool is the exact same
height of the weight that falls to turn off the kiln,
a kid slid his stool back...right in front of the kiln.
off went the sitter...smack on top of the stool.
kiln ran all night.
melted the shelves and the entire mess fell
into the sidewalls. pots stuck to the coils.
kiln shut itself off. (broken coils)
broken. ruined.
we threw it away.
old kiln...all used up anyway.
time for a new one. almost the same thing
happened a year later...but, thank god the janitor
spotted the light...turned the kiln off.
just an over fired kiln.
threw out the stuff.
loaded it the next day.
mel
ok vince...hear this one.
how i test for bad coils.
turn kiln to high for ten minutes.
open cover...prop it.
take a wooden pencil with an eraser.
touch each set of coils with the eraser end of the pencil.
does the eraser burn? splat, burned eraser. good coil.
eraser just sits there...coil is bad.
turn off kiln.
\i know..not osha approved..but it is a two minute test.
and, only a dork would touch the coils with metal or a
hand. just like checking with your fingers to see if your
chain saw has stopped spinning.
from mel/minnetonka.mn.usa
website: http://www.pclink.com/melpots
Gary Harvey on wed 6 jul 05
The way I test that a element is good is to use 1/2 inch paper pieces ripped
from a sheet. Lay them on the elements before you turn the elements on.
They will start to smoke on high in about 1 to 2 minutes. Which ever paper
is burnt is a good element. However, that doesn't prove that the elements
are bad. For instance, when my kiln sitter had problems, half the kiln was
not working, the elements didn't fire. The best way to test elements is to
use an ohm meter. An ohm meter test resistance. Most multimeters you can
buy from radioshack or electronic stores will have an ohm meter tester on
it. When you test for resistance and an analog meter needle goes to the far
right that is called infinite resistance. Digital meters will give a weird
reading. The display will jump around just like if you simply touched the
two leads together. Both meter will give a zero reading for open circuits.
Otherwords, if the elements are bad nothing will be the reading. You can
buy a cheap circuit tester from Wal-Mart that will also work. You can also
use a flash light bulb and a small AA battery. Test the bulb and battery
before you do this. Connect the bulb and battery in series with the ends of
the elements using alligator clips. If the bulbs lights your OK. If it
doesn't light you have a bad element. Good luck, Gary Harvey, (substitute
the obvious) prettypaos(at)academicplanet(dot)com
----- Original Message -----
From: "mel jacobson"
To:
Sent: Wednesday, July 06, 2005 6:59 PM
Subject: ruin an electric kiln
> it has happened to me twice.
> that was before i installed the 220v light
> above my desk. (for the janitor to see)
>
> the problem:
>
> the height of a throwing stool is the exact same
> height of the weight that falls to turn off the kiln,
> a kid slid his stool back...right in front of the kiln.
> off went the sitter...smack on top of the stool.
> kiln ran all night.
> melted the shelves and the entire mess fell
> into the sidewalls. pots stuck to the coils.
> kiln shut itself off. (broken coils)
> broken. ruined.
> we threw it away.
> old kiln...all used up anyway.
> time for a new one. almost the same thing
> happened a year later...but, thank god the janitor
> spotted the light...turned the kiln off.
> just an over fired kiln.
> threw out the stuff.
> loaded it the next day.
> mel
> ok vince...hear this one.
>
> how i test for bad coils.
>
> turn kiln to high for ten minutes.
> open cover...prop it.
> take a wooden pencil with an eraser.
> touch each set of coils with the eraser end of the pencil.
> does the eraser burn? splat, burned eraser. good coil.
> eraser just sits there...coil is bad.
> turn off kiln.
> \i know..not osha approved..but it is a two minute test.
> and, only a dork would touch the coils with metal or a
> hand. just like checking with your fingers to see if your
> chain saw has stopped spinning.
> from mel/minnetonka.mn.usa
> website: http://www.pclink.com/melpots
>
> ______________________________________________________________________________
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> melpots@pclink.com.
>
Vince Pitelka on thu 7 jul 05
> ok vince...hear this one.
I hear it Mel. I've seen kilns do that a few times, once at U-Mass when
someone unloaded a kiln and left a leather welding glove laying across the
top of the neighboring kiln. It was draped over one edge, right over the
kiln sitter. As was the case with the throwing stool in your studio, it
prevented the shutoff lever from falling. I came in the next morning to the
horrible smell of burning leather, and a kiln that was pretty much melted
inside. We salvaged the lid and the top section, threw out the rest.
These are dumb mistakes, and no one is to blame, but we can do plenty to
minimize the possibilities. If there are throwing stools in close proximity
to a kiln sitter that is at the same height, then good old Mr. Murphy is
waiting for the first opportunity to apply his law.
As you have seen, at the Craft Center we have a huge kiln room, and, all our
electric kilns are located far away from anything else at one end of the
room. No one leaves things on top of the kilns. No one pushes stools or
chairs up against the kiln. Hey, I'm not categorically denying the
possibility, but it hasn't happened in the 11 years I've been here (knock on
wood).
Any overfirings we have experienced in toploader electrics have been the
result of corroded cone support prongs (that was a dumb one, because they
are so cheap to replace), accumulated debris inside the porcelain sensing
tube, or warpage of the sensing rod that rests on top of the cone. In those
cases, we opened the kiln to find overfired bisque-ware, and a cone melted
but still stretched between the support prongs, supporting the sensing rod.
As I mentioned, it looks like we'll be getting rid of our last kiln-sitter
kiln in a few months, so hopefully those problems are a thing of the past
(knock on wood knock on wood knock on wood).
- 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/
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