schupp PTCR Handbuch Seite 6

PTCR
Technique & Application
2. What is the advantage of PTCR in comparison to
thermocouples?
PTCR measures the thermal conditions at the same place where the
product is located. It measures heat instead of a spot temperature.
So it measures the true important parameter for a firing process: the
total amount of heat applied to the product.
3. Why is the temperature reading from the PTCR different from
the set temperature?
The PTCR measures heat and the reading depends on the set
temperature in the kiln and the time the PTCR is exposed to heat.
4. What is the difference between PTCR and its main competitors?
The PTCR allows a numerical determination of the kiln performance
and is one of the most reliable products of its kind available on the
market. It assures the reproducibility of the heat treatment applied to
the product and so it's quality.
5. Why is the temperature reading in R(ing) T(emperature) instead
of Celsius or Fahrenheit?
Since the ceramic temperature indicator measures heat instead of
temperature, the RT reading has no direct relation to the absolute
temperature in Celsius or Fahrenheit. Only after taking into account
both time and set temperature, a relation between RT value and the
Celsius or Fahrenheit scale can be determined.
6. Can PTCR be used in every atmosphere?
In principle yes. How ever in case of reducing atmospheres or
vacuum conditions, PTCR ZTH, UTH, ETH, LTH and STH versions of
PTCR have to be pre-treated in air (see point 5.7). PTCR MTH and HTH
are already pre treated as a standard. After this pre-treatment the
PTCR will maintain its full capability without any exception. We advise
to contact our customer service desk before using the PTCR in these
conditions.
7. Is the performance of the PTCR influenced by the atmospheric
conditions?
Yes, the actual atmospheric conditions have an influence on the rate
of contraction of the ring. This leads to a RT reading, which may differ
from the expected value, e.g. it may be lower. This however has no
influence on the reproducibility of the reading, which will still assure
the firing conditions to be within the process limits.
8. Do I need to pre-treat all PTCR types before using it under
reducing atmospheres or vacuum?
PTCR MTH and HTH are already pre-treated as a standard. These
ring types do not need to be pre treated again.
9. How is the performance of PTCR affected by the soak time?
The PTCR will continue to contract as long as it is exposed to heat.
Effectively this means that at a constant set temperature, the RT
reading will be higher, the longer the soak time is. The best
approximations are obtained by applying a ramp up speed of 120
Rev. 4_26.01.2018
°C/hour and a top temperature hold time (soak time) of 1 hour. For a
hold times of more than 1 hour please ask for the correction graph. If
you work with extreme short or extreme long soak times, please
contact our technical service staff. The maximum hold time for ZTH
rings is 2 hours.
10. Do I have to adjust my kiln setting once I apply a new batch of
PTCR?
No, provided the table delivered with a new batch is used, no changes
to the settings are necessary. Every new batch of PTCR is factory
(re)calibrated to assure the same RT reading under the same kiln
conditions.
11. Is there any influence of the material of the supports used?
Yes, it is known that "reactive" support material like e.g. carbon
strongly inhibits the performance of ceramic temperature indicators.
The support should be of a non reactive material, like ZrO
etc.
12. Has the temperature ramp-up any influence on the PTCR
performance?
Yes it does, because the PTCR registers the cumulative amount of
heat absorbed. A long ramp-up time will result in a higher RT reading
than a fast temperature ramp-up.
13. Do I need the micrometer to perform the measurements?
To ensure a correct determination of the contraction of the ring, it is
of vital importance, that the ring is positioned correctly during the
measurement of the ring diameter after the firing cycle is completed.
The special measuring device is the best assurance of a correct "fool
proof" RT reading. The PTCR Micrometer is available with USB port.
With a special USB cable you can connect the PTCR Micrometer to a
computer or laptop and transfer the measuring result at
the touch of a button. There is no special software required!
14. Why do different batches yield different ring temperatures and
how are these differences compensated for?
Batches differ, there is no question about that and there is no avoiding
that. The reason for this is that the materials used to manufacture the
rings differ from batch to batch. There are differences in composition,
grain size distribution and so on, which affect the shrinkage of the
rings made with these materials. So even though the same recipe is
used with every batch, there will be small but significant differences.
This will be minimized in future due to the usage of synthetically raw
materials.
To compensate for these differences a calibration of each batch by
firing rings from the new batch together with rings from the reference
batch in their standard conditions can be done. Usually slightly
different diameters are found. The diameter from the reference rings
gives the actual (RT) temperature.
The diameter from the rings of the new batch is correlated to this
temperature. This process is repeated 8 times, each time at a different
set temperature, covering the entire temperature range of the rings.
This results in 8 diameters, which correlate to 8 actual temperatures.
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M.E. SCHUPP Industriekeramik GmbH & Co. KG
Neuhausstraße 4-10, 52078 Aachen/Germany
Tel.: +49 (0) 241 -93677-0 Fax: +49 (0) 241 -93677-15
www.schupp-ceramics.com info@schupp-ceramics.com
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