High temperature metrology for industrial applications (>1000 °C)

High temperatures, above 1000 °C, are routinely used in a range of European industries and in the production of iron, steel, glass and ceramics. These temperatures have to be carefully controlled during manufacturing, but measuring high temperatures accurately is challenging as environmental conditions affect the performance of measurement devices. At high temperatures, contact thermometers, such as thermocouples, become brittle and damaged while the performance of non-contact thermometers changes over time. In harsh environments, stopping processes to access measurement devices for recalibration or replacement is costly and the ideal solution is robust and stable temperature measurement devices.

This project developed methods to improve reliability and robustness of contact and non-contact high-temperature measurement, including:

• A demonstration of self-correcting thermocouples that self-calibrate without having to be removed from their operating environment.
• A facility to assess the performance of new thermocouples made from exotic materials, which may be better suited to harsh conditions. The performance of such thermocouples needs to be clearly understood and validated before they can be used in industry.
• A method to self-correct radiation (non-contact) thermometers was developed using blackbodies that emit radiation at fixed temperatures, allowing periodic assessments of thermometer accuracy.
• A demonstration of real-time, accurate temperature measurement for laser hardening, an industrial mass-production technique that hardens materials using a high-temperature laser.

The techniques and facilities developed are contributing to more accurate measurement of high temperatures in industry. Self-correcting contact thermocouples and novel materials for thermocouples are being developed further in the EMPIR project 14IND04 EMPRESS. This project will develop more durable high-temperature thermocouples that will be trialled in industry. The technique using fixed-temperature black bodies to validate non-contact temperature measurements has been used by the French Alternative Energies and Atomic Energy Commission (CEA) to study the effects of high temperatures on glass and concrete under critical conditions. The method developed for temperature measurement during laser hardening has been incorporated into the laser-hardening systems of an R&D organisation and material processing company in Germany.