Tile Manufacturing

The tile industry plays a crucial role in the modern construction sector by providing innovative solutions for flooring and wall design. A key aspect of the production process for ceramic tiles is the sintering or firing process, which significantly influences the quality and functionality of the final product.

Different types of tiles, such as earthenware, stoneware, and porcelain stoneware, require varying firing temperatures and durations to develop their specific properties. Earthenware tiles, with a water absorption rate of over 10%, are fired at 900–1.100 °C, remain porous, and are mainly suitable for interior wall coverings. Stoneware and porcelain stoneware tiles, with a water absorption rate below 3%, are fired at 1.150–1.300 °C, achieving near-complete sintering, making them highly durable and suitable for a wide range of applications.

Firing is usually carried out in roller or tunnel kilns. To ensure consistent product quality, controlling the temperature distribution and heat input is crucial, as these factors directly affect the quality, strength, hardness, color, and other essential properties of the tiles. In light of modern trends, such as the use of large-format tiles, monitoring the homogeneity of the sintering process is particularly important to ensure uniform firing. Process Temperature Control Rings (PTCR) assist in cost-efficient thermal monitoring of kilns, ensuring consistent sintering results.

What are Process Temperature Control Rings?

PTCRs are ceramic rings that shrink proportionally to the heat input. The degree of shrinkage depends on factors such as the temperature profile in the kiln/furnace, heat conduction conditions,  and the dwell time in the kiln. The 20 mm small PTCR can be placed directly on the product and almost anywhere on the kiln/furnace car.

Pyrometric Rings help overcome various challenges in ceramic tile production and minimize potential issues:

Cracks and Breaks:
Cracks or breaks occur when the temperature inside the kiln is unevenly distributed or when the material is heated or cooled too quickly. This can compromise the structural integrity of the tiles and their glaze.

Deformations:
Uneven temperature distribution can lead to inconsistent shrinkage of the green body, causing deformations in the sintered material.

Color Variations:
Shade differences between batches can result from uneven heat distribution. Precise control of the firing process ensures consistent color tones.

Optical Properties:
The gloss or matt finish of the tile surface can be precisely controlled through accurate temperature regulation.

Energy Efficiency:
An inefficient firing process leads to increased energy consumption and rising production costs. Optimized kiln design and control can help minimize energy demand.

Use of Process Temperature Control Rings

After firing, the rings are removed, measured for their diameter, and the so-called reference temperature is determined using the provided temperature tables. This reference temperature indicates the heat input at the specific location in the kiln. Pyrometric rings allow for easy determination of heat input and continuous monitoring of kiln operation.

To minimize deviations and optimize energy efficiency, precise control of the firing process is essential. For tile firing, three main variants are available, depending on process parameters:

• PTCR ETH (850 °C - 1.100 °C)
• PTCR LTH (970 °C - 1.250 °C)
• PTCR STH (1.130 °C - 1.340 °C)

The appropriate ring type should be selected so that the maximum process temperature falls approximately in the middle of the temperature range. If the temperature is at the boundary between two ring types, additional process conditions such as holding time and atmosphere should also be considered.

In total, eight different PTCR ring types are available for the temperature range of 560 °C to 1.750 °C.