Small rings, big impact – Step-by-Step User Guide

Photo: Robert Wiezorek,

Would you like to use our PTCR process temperature control rings to optimize your firing process? However, you do not know how to use the PTCR rings. In our current news we present you in a short step-by-step instruction to easily use PTCR.

Function of Process-Temperature-Control-Rings

The PTCR is a ceramic ring which shrinks if it is exposed to heat. The degree of shrinkage depends on the actual temperature in the kiln, the heat transfer properties of the kiln and the time it is exposed to the heat treatment.

1. Selection

Select a PTCR type whose central temperature spread is nearest to the kiln’s peak firing temperature. PTCR are most sensitive to temperature changes in the middle of temperature range rather than at the extreme ends. If your sintering process takes place in conditions other than under oxidizing atmosphere, please check in our manual whether a pre-treatment of the rings is necessary!

SCHUPP® Ceramics bietet sieben Ringtypen für unterschiedliche Temperaturbereiche.


2. Positioning of the rings

The rings can be placed at almost any location in the kiln where a determination of the thermal performance is desired. The more rings you place in the kiln the more detailed the heat mapping. Please make sure that the rings are marked in relation to their position in the kiln!

3. Start sintering process

Sintering process can take place. The PTCR will register the total amount of heat transferred and shrink as long as it is exposed to heat.

4. Measuring of the rings

PTCR Mikrometer - Zum präzisen Ausmessen der Prozess-Temperatur-Kontrollringe PTCR

Photo: Robert Wiezorek,

After the termination of firing cycle, the ring diameters have to be measured. The special PTCR Micrometer ensures an operator independent, reliable and accurate record of the ring diameter. Rings do not have to be measured before using the rings because differences are statistically corrected and integrated in the conversion chart.

5. The temperature conversion table

The shrinkage of the diameter of the ring has to be converted into the Ring Temperature (RT) by using the temperature conversion table. This table is updated for every batch of rings to be delivered which means that both the product and the conversion table have a unique relation. Please, make sure, that you use the correct table.

6. Interpretation of the ring temperature

The first time the PTCR is applied, different runs (trials) with different parameter settings have to be made and the resulting products have to be compared to the quality standard. In this way the optimal process settings and RT values are coupled. In a new run, if the RT values are the same, the firing conditions have been the same and the quality of the product is assured.

It has to be emphasized, that RT values do not necessarily compare to absolute temperatures. Because it measures the heat transferred to the ring, a longer soak time at the same top temperature will cause the ring to shrink further, resulting in a higher RT value. However, the PTCR allow you to accurately determine differences in the heat treatment both within and between certain kiln loads. The same measured RT values guarantee the same amount of heat transferred. This means that so the same firing conditions have been applied.

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°C/hour and a top temperature hold time (soak time) of 1 hour.

For further information on calibration, application, and another technical details and influences to the measuring results please refer to our PTCR Manual.

To the PTCR Manual

We also show you all this and much more in our product video.

To the video


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