When installing thermocouples and resistance thermometers, attention should be paid to ensuring accurate temperature measurement, safety, reliability, and ease of maintenance, without affecting equipment operation and production. To meet these requirements, the following points should be considered when selecting the installation location and insertion depth of thermocouples and resistance thermometers:
1. To ensure sufficient heat exchange between the measuring end of the thermocouple or resistance thermometer and the measured medium, the measuring point location should be chosen reasonably, avoiding installing thermocouples or resistance thermometers near valves, elbows, and dead corners of pipes and equipment.
2. Thermocouples and resistance thermometers with protective sleeves experience heat transfer and heat dissipation losses. To reduce measurement errors, thermocouples and resistance thermometers should have sufficient insertion depth:
(1) For thermocouples measuring the temperature of the fluid in the center of a pipe, the measuring end should generally be inserted into the center of the pipe (vertical or inclined installation). If the pipe diameter of the measured fluid is 200 mm, the insertion depth of the thermocouple or resistance thermometer should be 100 mm;
(2) For temperature measurement of high-temperature, high-pressure, and high-velocity fluids (such as main steam temperature), to reduce the resistance of the protective sleeve to the fluid and prevent the protective sleeve from breaking under the action of the fluid, a shallow insertion method or a thermowell type thermocouple can be used. For shallow-insertion thermocouples, the insertion depth into the main steam pipe should be no less than 75 mm; the standard insertion depth for thermowell type thermocouples is 100 mm;
(3) If the temperature of flue gas in a flue is to be measured, even if the flue diameter is 4 m, an insertion depth of 1 m for the thermocouple or resistance thermometer is sufficient;
(4) When the insertion depth of the measuring element exceeds 1 m, it should be installed vertically as much as possible, or a support frame and protective sleeve should be added.
