Steve Slatin on wed 9 jul 08
Paulette -- I don't have the exposed-type
thermocouples, but I don't think that should
make a difference -- you can tell if your
thermocouples are 'drifting' by examining
your cones. If the cones start to show
different results when the computer (or just
the thermocouple itself) are telling you
that you're making temperature, then the
TC is drifting.
Steve Slatin --
--- On Wed, 7/9/08, Paulette Carr wrote:
>
> I have a 3-probe computer controlled ConeArt kiln. I have
> fired
> under 100 times in this kiln, 80% under ^02, and 20% at ^9.
> All
> firings within the last year and a half have been at lower
> tempteratures These are long slow firings.
>
> The lining or cladding (refactory, I believe) of these
> pyrometer
> probes has cracked, and in some cases broken off. The
> probes were
> never completely encased (a 0.25" section of the tip
> was always
> exposed, but now more of the metal of the probe is exposed.
> I do not
> see any obvious metallic degradation/deterioration, just
> the normal
> darkening(oxidation?). How might this affect the heat-work
> of the
> various zones, and ultimately the life of my elements?
>
> Finally, how long do these probes last, and how do I know
> when to
> replace them? I do not see any obvious drift, just a very
> slightly
> cooler section of the kiln lately. I realize that this
> could be due
> to many other factors, such as the load of each shelf, and
> the
> elements, themselves.
Paulette Carr on wed 9 jul 08
Earl Brunner wrote:
I use Euclid's all the time in the city kilns. I change out the
elements about every 200 firings of which about half are glaze to
cone 6. There are a lot of factors on element life. One might be
the connectors and how well you fastened them together..... Another
is the pyrometer probe (at least on our computer controlled kilns.
Steve Slatin wrote:
There are many things that can affect
a kiln's firing though -- especially
computer-controlled kilns, where the
sending unit (thermocouple/s) may
show 'drift' or other irregularities
after many firings.
(I did replace my thermocouples about
a half year after replacing my elements.
When I pulled them from the protective
tubes, they were very deteriorated.)
I have a 3-probe computer controlled ConeArt kiln. I have fired
under 100 times in this kiln, 80% under ^02, and 20% at ^9. All
firings within the last year and a half have been at lower
tempteratures These are long slow firings.
The lining or cladding (refactory, I believe) of these pyrometer
probes has cracked, and in some cases broken off. The probes were
never completely encased (a 0.25" section of the tip was always
exposed, but now more of the metal of the probe is exposed. I do not
see any obvious metallic degradation/deterioration, just the normal
darkening(oxidation?). How might this affect the heat-work of the
various zones, and ultimately the life of my elements?
Finally, how long do these probes last, and how do I know when to
replace them? I do not see any obvious drift, just a very slightly
cooler section of the kiln lately. I realize that this could be due
to many other factors, such as the load of each shelf, and the
elements, themselves. But I do not know if I should replace these
probes. ( I do have pictures of the probes, along with new ones which
I can send off-line, if the visual will help.)
Thanks in advance for your help!
Regards,
Paulette Carr
Paulette Carr Studio
St. Louis, MO
Member Potters Council
Arnold Howard on wed 9 jul 08
From: "Paulette Carr"
> Finally, how long do these probes last, and how do I know
> when to
> replace them? I do not see any obvious drift, just a very
> slightly
> cooler section of the kiln lately.
I wouldn't replace the thermocouples until they either
stopped working, began to show erratic temperature readings,
or drifted way off in temperature.
If the welded tip cracks, sometimes the thermocouple will
continue to work, but the readings may bounce around. You
can verify that the thermocouple is bad by moving the
thermocouple tip with your fingers. If the readings become
more erratic, replace the thermocouple.
Type-K thermocouples gradually drift in temperature. You can
adjust the controller's Thermocouple Offset to compensate
for this.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
Paulette Carr on fri 11 jul 08
Thanks to Hank, Arnold and Steve for responding and sharing their =20
expertise! I will be following Arnold=92s advice to retain my current =20=
thermocouples for awhile, since they seems to be in pretty good shape =20=
(and the change in heat work is just a few degrees), and use the =20
thermocouple offset to compensate for the drift. I must admit that =20
it never occurred to me to do this, so I am pleased to add another =20
trick to my bag!
My best,
Paulette Carr
Paulette Carr Studio
St. Louis, MO
Member, Potters Council
On 9 July, 2008, Arnold Howard wrote:
I wouldn't replace the thermocouples until they either
stopped working, began to show erratic temperature readings,
or drifted way off in temperature.
If the welded tip cracks, sometimes the thermocouple will
continue to work, but the readings may bounce around. You
can verify that the thermocouple is bad by moving the
thermocouple tip with your fingers. If the readings become
more erratic, replace the thermocouple.
Type-K thermocouples gradually drift in temperature. You can
adjust the controller's Thermocouple Offset to compensate
for this.
On 9 July, 2008, Steve slatin wrote:
Paulette -- I don't have the exposed-type
thermocouples, but I don't think that should
make a difference -- you can tell if your
thermocouples are 'drifting' by examining
your cones. If the cones start to show
different results when the computer (or just
the thermocouple itself) are telling you
that you're making temperature, then the
TC is drifting.
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