When installing bimetallic 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 the thermometer:
(1) To ensure sufficient heat exchange between the measuring end of the thermometer and the measured medium, the measurement point should be selected reasonably, and the thermometer should be installed as far as possible from valves, elbows, and dead corners of pipes and equipment.
(2) Thermometers with protective sleeves have heat transfer and heat dissipation losses. To reduce measurement errors, thermocouples and resistance thermometers should have sufficient insertion depth:
a. For resistance thermometers measuring the temperature of the fluid in the center of the 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 resistance thermometer should be 100 mm;
b. For temperature measurement of high-temperature, high-pressure, and high-speed 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 resistance thermometer can be used. The insertion depth of the shallow-insertion resistance thermometer protective sleeve into the main steam pipe should be no less than 75 mm; the standard insertion depth of the thermowell type resistance thermometer is 100 mm;
c. If the temperature of the flue gas in the flue is to be measured, even if the flue diameter is 4 m, an insertion depth of 1 m is sufficient;
d. 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.
