Enhancing process efficiency through improved temperature measurement

Energy efficiency is at the heart of EU Commission plans for improving the competitiveness of Europe’s manufacturing industries, that, combined, account for about 25 % of total EU energy consumption. Industrial processes, for example the heat treatment of aircraft components, are best maintained at specific temperatures for optimal efficiency, yet precise control is not always achievable due to the measurement inaccuracies of industrial thermocouples at high temperatures. Also, thermocouples used in industrial processes tend to be susceptible to measurement drift, resulting in expensive and disruptive replacement rather than recalibration, as such thermocouples cannot be recalibrated in-situ.

The project developed and evaluated new, more stable, thermocouples, including self-validating thermocouples: a Platinum-Rhodium thermocouple optimised for minimal calibration drift for use up to 1800 C; a sapphire tube-based blackbody sensor for use in silicon processing up to 1600 C; and a carbon thermocouple for use above 2000 C. To implement in-situ traceability of temperature measurement in industry, ultra-low drift sensors were developed and assessed. A mineral-insulated, metal-sheathed, double-walled thermocouple emerged that offered ten times the stability of equivalent conventional thermocouples, and a self-validating thermocouple with a traceably calibrated fixed-point cell providing in-situ self-calibration. A suite of thermometry techniques was also developed based on phosphor thermometry, as well as a contact probe capable of automatically compensating for heat flow; a key output being a surface probe calibrator. Finally, a portable standard flame was characterised, for use as an artefact to traceably calibrate flame and combustion thermometry instrumentation.

As the project concluded, a licensing agreement was signed with CCPI Europe to exploit the developed slimline in-situ thermocouple design, targeting high-value manufacturers looking to reduce downtime costs and improve confidence in temperature measurements. A portable standard flame was offered by NPL as an artefact to validate flame thermometry systems, such as for in-field monitoring of thermal aspects of welding; work being further developed as a practical imaging spectrometer for industrial use within the follow-on project EMPRESS2.

Improvements in temperature measurement accuracy developed in EMPRESS provide opportunities for enhanced control of industrial processes, likely to lead to higher-quality products, higher levels of process efficiency and improved competitiveness for Europe’s manufacturing industries.