Temperature Control Rings
PTCR Rings
Detailed User Guide
Introduction:
Process Temperature Control Rings (PTCR) are an invaluable tool for optimizing the firing of ceramics, refractories, and other materials in industrial kilns. Despite their compact size, they provide crucial information about heat distribution and the quality of the final product.
In this blog, we will guide you step-by-step through the use of PTCR rings, from selection to the interpretation of results.
1. Selection of the Appropriate PTCR Ring:
The first step is to choose the right type of PTCR ring for your application. PTCR rings are classified according to their central temperature range, which should be close to the maximum firing temperature in your kiln.
Consider the following:
Temperature Range: Choose a PTCR ring whose central temperature range encompasses the maximum firing temperature in your kiln. The rings are more sensitive to temperature changes within the middle range than at the extremes.
Firing Conditions: If your sintering process is conducted in an atmosphere other than oxidizing, consult the PTCR manual to check if pre-treatment of the rings is required.
2. Placement of the Rings:
PTCR rings can be placed almost anywhere in the kiln where you want to evaluate thermal performance. The number of rings will determine the precision of the heat map. Be sure to mark each ring with its position in the kiln.
3. Execution of the Firing Process:
Start the normal firing process. The PTCR ring will record the total amount of heat transferred during the heat exposure.
4. Measurement of the Rings:
Once the firing cycle is complete, measure the diameter of each ring with a special PTCR micrometer. This micrometer ensures precise, user-independent measurement. There is no need to measure the rings before use, as differences are corrected statistically and included in the conversion table.
5. Conversion of the Measurement to Temperature:
Use the temperature conversion table provided with each batch of rings to convert the diameter shrinkage into ring temperature (RT). This table is unique to each batch of rings and product, so make sure to use the correct one.
6. Interpretation of the Ring Temperature:
When using PTCR rings for the first time, tests should be conducted with different parameter settings and the resulting products compared to a quality standard. This establishes the relationship between optimal process settings and RT values.
In subsequent trials, consistent RT values indicate that firing conditions have been the same and product quality is assured.
It is important to note that RT values do not always represent absolute temperatures. The PTCR ring measures transferred heat, so a longer soaking time at the same maximum temperature will cause greater ring shrinkage and a higher RT value.
However, PTCR rings are ideal for determining differences in thermal treatment within and between kiln loads. Consistent RT values ensure the same amount of heat transferred, meaning the same firing conditions have been applied.
7. Additional Considerations:
- The PTCR ring will continue to shrink as long as it is exposed to heat.
- The best approximations are obtained with a temperature ramp-up rate of 120 °C/hour and a maximum temperature holding time (soak) of 1 hour.
- For more information on calibration, application, technical details, and influences on measurement results, consult the PTCR manual.
