Watlow produces various products covering multiple fields, including temperature control, heating, sensors, and controllers.
Type of Thermocouples
Thermocouples are temperature sensors classified into several types. Watlow produces the following types of thermocouples: J, K, T, E, N, R, S, and B. The differences between these types are their metal combinations, measurement range, and accuracy. For example, J-type thermocouples are suitable for measuring the temperature at high temperatures, while K-type thermocouples are widely used in industrial control and heating processes.
In addition to the three common types, Watlow also produces other types of temperature sensors, such as RTD types, surface mount temperature sensors, gas temperature sensors, and fiber optic temperature sensors. The differences between these types are their measurement methods, applicable environments, and response times.
The different types of temperature sensors produced by Watlow differ in their measurement principles, metal combinations, sheath materials, and applicable ranges. Users should choose the appropriate type based on their specific needs.
Temperature Measurement of Molten Steel
Temperature measurement of molten steel is an important task in industrial production, and therefore, a suitable type of thermocouple is needed. Generally, the thermocouple type used to measure molten steel temperature should have the following characteristics:
- A high-temperature measurement range: The temperature of molten steel is usually above 1300°C, so a thermocouple type that can withstand high temperatures is needed.
- Corrosion resistance: Molten steel contains many metal elements and impurities, which can easily corrode sensors. Therefore, a thermocouple type with corrosion resistance is needed.
- High-precision measurement: The temperature of molten steel requires high accuracy, so a thermocouple type with high accuracy is needed.
Based on these characteristics, the R-type or S-type thermocouple is usually selected for measuring the temperature of molten steel. R-type and S-type thermocouples are precious metal thermocouples with a high-temperature measurement range (usually above 1300°C), good corrosion resistance, and high accuracy, making them widely used in molten steel temperature measurement. When using R-type and S-type thermocouples for temperature measurement, it is usually necessary to use a protective tube to protect the thermocouple from corrosion and mechanical damage, and to extend its service life. The selection of the protective tube should be determined based on the measurement environment and requirements.
For R-type and S-type thermocouples, ceramic thermowell is generally used. This is because ceramic protective tubes have good corrosion resistance and mechanical strength, can withstand high temperatures and thermal shock, and also have good insulation performance, making them suitable for use in harsh working environments.
How to Choose a Protective Tube?
When selecting a ceramic protective tube, its material and structure need to be determined based on the characteristics of the measurement environment.
- When measuring high-temperature melts, silica ceramic protective tubes can be selected, which have good high-temperature resistance and mechanical strength
- When measuring oxidizing-reducing environments, silicon nitride ceramic protective tubes can be selected, which have good corrosion resistance and thermal shock resistance.
- In some special cases, such as measuring high-temperature, high-pressure, and highly corrosive media environments, metal-ceramic protective tubes need to be used.
Metal-ceramic protective tubes are protective tubes composed of metal and ceramic materials and have the advantages of both metal and ceramic protective tubes. The metal part of the metal-ceramic protective tube has good corrosion resistance and mechanical strength, and can withstand high pressure and mechanical impact; while the ceramic part has good high-temperature and corrosion resistance, and can protect the thermocouple from the effects of high temperature, highly corrosive media, and mechanical damage.
In addition, to improve the measurement accuracy of the thermocouple, the length and diameter of the protective tube also need to be determined based on the measurement requirements. The length of the protective tube should be as same as the surface area in contact with the measurement environment possible, to ensure temperature uniformity; and the diameter of the protective tube should be determined based on the size of the measurement environment, for easy installation and removal.
