Issues regarding temperature measurement in power plant auxiliary equipment – Instrument selection – Thermal power plant processes

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I’m seeking help regarding the boiler feed pump of a million-unit unit: the temperature is 186 degrees. The outlet pressure during the speed-reduction test is 40 MPa, while it is 64 MPa at full speed. It is required that during testing, the temperature difference between the inlet and outlet of the pump be measured; this difference is quite small, only a few degrees. In regular tests, we usually use PT100 thermistors with threaded connections for temperature measurement; they are of the insert type and must have an adequate insertion depth as required. This allows for a relatively quick response, within a few seconds, with low error levels as well. But this time the pressure of this pump is too high; it’s definitely not possible to use a thermistor connected by threads. I saw in the sample materials that there is a sleeve-type design, where the protective sleeve is welded to the pipeline and the thermistor is inserted inside that sleeve. I also bought a few of these thermal resistors. But I found that the response time is extremely slow – it’s not just a matter of ten-odd seconds; I conducted a simple test. When the thermistor is placed in hot water, the temperature continues to rise slowly over three minutes without stabilizing; such a slow response rate does affect my measurement results. I would like to ask those who are familiar with power plant processes: what temperature measurement instruments are used on-site, especially in situations where rapid temperature response is required? What types, connection methods, and manufacturer brands are available? Thank you. At the moment, I buy all of my products from Shangziyi in China; I use other brands less often. I hope some experienced experts can answer this question. Thank you.