TDC – True Disc Clearance

TDC – True Disc Clearance

The TDC sensor has been designed to measure the gap between the grinding plates in high yield pulp refiners. The sensor is a market leading product that we are constantly developing and improving.

The TDC sensor is available in several models for the different refiner types used by pulp manufacturers all over the world.

The development of the TDC sensor

The TDC sensor has been used in refiners from Valmet since the 1970s and has been further developed over the years. Today the sensor can be considered as very solid and stable.

The sensor also contains a temperature element for indication of the process temperature to protect the sensor from overheating (>225 °C). The sensor’s temperature range extends up to 220 °C, which is necessary for certain high pressure processes.

Since we introduced complete welding of the sensor, the strength and the tightness have been further improved. As a result of this, the sensor is entirely protected from the chemicals of the pulp process, which contributes to longer life and higher stability.

TDC sensor
TDC sensors and segment

Technical specifications

Sensor principle Reluctance sensor
Measuring range 0-3 mm
Response time 500 ms
Accuracy ± 0.03 mm plus ± 1% of current value
Resolution 0.01 mm
Temperature range 0-220 ºC
Materials Stainless steel and bronze, aluminum in the socket
Mechanical dimensions Depending on model
Diameter of the holder 45-55 mm
Diameter of the measuring tip 27 mm
Distance to supporting edge 23 mm
Total length 97-476 mm
Weight 0.5-5.3 kg