Different Atmospheres; Pre-Treatment Of Ptcr; Faq - schupp PTCR Handbuch

PTCR
Technique & Application
absolute temperature. Under certain conditions RT readings may be
related to the absolute temperature scales.
The best approximations are obtained by applying a ramp up speed
of 120 °C/hour and a top temperature hold time (soak time) of 1 hour.

5.6 Different atmospheres

The PTCR originally has been developed for use in heating processes
in air. However the ring may be applied under different atmospheric
conditions as well provided some rules are taken into account. We
advise clients to contact our customer service desk in case of using
the rings for firing processes under reductive or vacuum
circumstances. In this way the specific advice can be given in order
to get optimal results.
As a general rule it can be stated that, under vacuum conditions and
reductive atmospheres like N2/H2 mixtures, the rings have to be pre-
treated to burn out the organic binder system of the ring completely.
If this is not done properly, the organic material will not disappear as
CO , but will decompose to carbon. This carbon, left behind in the
2
ring, will inhibit the shrinkage of the ring, resulting in a lower RT
reading than expected. Under vacuum conditions, the carbon may
even precipitate on the kiln wall and contaminate the kiln.
In addition to that, under vacuum the RT reading will be lower than
expected, because the heat transfer mechanism lacks the
contribution of convection.
It is known that PTCR absorb carbon when used in a carbonising
atmosphere. The carbon migrates through the ring and will inhibit the
shrinkage significantly. It has to be determined by trial and error, to
assess whether sufficient shrinkage capability is left to allow an
accurate determination of the change in the outer ring diameter.
5.7 Pre-firing / -treatment of PTCR
As mentioned under point 5.6 of this manual, it is absolutely
necessary to pre-fire PTCR under specific requirements before using
it e.g. under reducing atmospheres or vacuum.
PTCR MTH and HTH are already pre-treated and do not need to be
pre-treated again! Would you like to pre-fire PTCR yourself, please
use the following ring specific pre-firing parameters:
5.7.1 Firing curve for PTCR ZTH
Rev. 4_26.01.2018
5.7.2 Firing curve for PTCR UTH
5.7.3 Firing curve for PTCR ETH
5.7.4 Firing curve for PTCR LTH
5.7.5 Firing curve for PTCR STH
We will gladly manage the pre-firing process for you. Please feel free
to contact us!
6. FAQ – Frequently Asked Questions
1. What is a PTCR?
PTCR is a ceramic device, which measures the total heat transferred
during a firing cycle. It is not a temperature indicator in the same
sense as a thermocouple, it is an energy meter. The indicated Ring
Temperature is a standard that has to be the same by rehearsed firing
processes under the same conditions. In this way the stability of the
process and quality of the products is assured.
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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