Fixed-Point Thermocouples in Power Plants: Long-Term Operational Experiences

Abstract

For more than four years, commercially available fixed-point thermocouples have measured hot-steam temperatures in power plants. A periodic self-adjustment procedure should keep their total measuring uncertainty within 1 K. This paper gives a short introduction to the measuring system components and their function. Despite heavy mechanical and thermal loads, the sensing elements show high reliability and appropriate availability. To evaluate the long-term reproducibility of the method, single thermometers have been dismantled and recalibrated in the laboratory at different time intervals. After more than 35 000 h of hard routine service the results have confirmed the expected uncertainty level.