PTCR HTH ceramic rings for oven temperature control

What is PTCR?

PTCR is a ceramic ring that records all the heat that is transferred onto it in the sintering furnace during firing. Thanks to the use of highly advanced techniques and materials, it provides an accurate representation of the heating process taking place in the furnace in the area of the ring. PTCR helps to achieve an outstanding quality of zirconia restoration.

The actual temperature set in the furnace during a firing process, as measured by thermocouples, does not guarantee repeatability of the firing conditions, which will of course affect the quality of the final product. The thermocouple gives the exact temperature only for a certain point, which does not coincide with the temperature of the whole product area. The final product temperature is determined by the total heat transfer and is not measured by the thermocouple. In addition, the same temperature set in different ovens does not guarantee the same heat treatment.

The PTCR ring has been designed to get a better representation of the firing process in order to give a better control of the transferred temperature.

The PTCR is a ceramic ring that records all the heat that is transferred onto it 

The PTCR measures the total amount of heat transferred around the ring by conduction, convection and radiation.It takes into account different firing conditions that may occur in the kiln, such as radiators, temperature gradients, gas flow, heat transfer coefficient, time, kiln setting, etc. Due to the measurement of the total heat, the repeatability of the process is ensured, thus the quality of the final product.

Click on the video below for presentation!

How does a PTCR ring work?

PTCR is a ceramic ring that shrinks when exposed to heat. The degree of shrinkage depends on the actual temperature in the furnace, the heat transfer properties of the furnace and the time of exposure to heat. The shrinkage (by how much the diameter of the ring has shrunk) is measured with a digital or numerical micrometer.

For simplicity and for comparison, the shrinkage (and therefore the total amount of heat absorbed) is translated into a single parameter - the ring temperature (RT). In short, it is not a temperature, but a time and temperature dependent parameter. E.g., RT does not reflect the maximum temperature of the combustion process and does not correspond to the actual temperature in the furnace, because the PTCR accumulates all the absorbed heat over time.

The measured contraction is converted by a table into RT (ring temperature), which is the effective temperature describing all the heat absorbed by the ring and the products in the oven. The ring temperature is the total temperature of the entire firing cycle and is not directly related to the temperature in Celsius, Fahrenheit or Kelvin. The ring temperature reading is influenced by the holding time. At a constant temperature, the PTCR will continue to contract, leading to a higher parameter. The maximum holding time (0.5-10h) depends on the type of ring used.

When is PTCR used?

Due to its specific properties, PTCR has a wide range of indications, the main ones being:

A) Process control and optimization

B) Problem identification

C) Increasing throughput

D) Increasing the quality of the final product

E) Reducing time and cost for final product inspection

General use

Step 1 - Place the ring in the oven

Step 2 - Burning

Step 3 - Measure the diameter of the ring with a micrometer

Step 4 - Convert the diameter in RT (ring temperature), according to the correspondence table received with the ring.

Presentation: set of 15 pre-treated rings HTH - 1450°C - 1750°C