Introduction of different graduation numbers of thermocouples for power plants
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Thermocouples for power plants are temperature sensing elements and primary instruments. They directly measure temperature and convert temperature signals into thermoelectric potential signals, which are then converted into the temperature of the measured medium through electrical instruments. The main types of thermocouples are S, R, B, N, K, E, J, T, etc. Among them, S, R, and B belong to precious metal thermocouples, and N, K, E, J, and T belong to cheap metal thermocouples.
The characteristics of S-grade are strong oxidation resistance and are suitable for continuous use in reducing and plastic atmospheres. The long-term application temperature is 1400℃ and the short-term application temperature is 1600℃. Among all thermocouples, S-grade has the highest accuracy level and is generally used as a standard thermocouple;
Compared with S-grade, R-grade has about 15% higher thermal induced potential, and other characteristics are basically the same;
The thermal induced potential of B-grade is very small at room temperature, so compensation wires are generally not required for accurate measurement. Its long-term application temperature is 1600℃, and short-term application temperature is 1800℃. It can be used in reducing or neutral atmosphere, and can also be used in short-term application under vacuum pump conditions.
The characteristics of N-grade are strong high-temperature oxidation resistance at 1300℃, good long-term reliability of thermal induced electromotive force and reproducibility of short-term thermal cycle, good resistance to nuclear radiation and cold resistance, and can partially replace S-grade thermocouples;
The characteristics of K-grade are strong oxidation resistance, suitable for continuous use in reducing and plastic atmospheres, long-term application temperature of 1000℃, short-term application temperature of 1200℃. It is widely used in all thermocouples;
The characteristics of E-grade are that among common thermocouples, its thermal induced electromotive force is large, that is, the sensitivity is the highest. It is suitable for continuous use in reducing and ductile atmospheres, with an application temperature of 0-800℃;
The J-grade is characterized by being usable in both reducing atmospheres (application temperature limit 750℃) and oxidizing atmospheres (application temperature limit 950℃), and is resistant to H2 and CO gas corrosion, and is mostly used in refineries and chemical plants;
The T-grade has the highest level of accuracy among all low-cost metal thermocouples, and is generally used to accurately measure temperatures below 300℃.
