Molybdenum disilicide protection tubes primarily serve two functions: first, to prevent thermocouples from mechanical damage; second, to protect thermocouples from chemical corrosion by the measured medium.
      Thermocouples must be isolated in the following types of media: 1. Various metals (in all forms) that may alter the chemical composition of the thermocouple upon contact. 2. Furnace gases and vapors that can corrode thermocouple materials (sulfur and its compounds are harmful). 3. Various electrolytes that can corrode thermocouple materials.

      Thermocouple protection tubes are usually single tubes. In certain special cases, two concentrically installed protection tubes can be used. The one closer to the thermocouple is called the primary protection tube, while the outer one is referred to as the auxiliary protection tube. Typically, an alumina tube is used as the primary protection tube, and a silicon carbide tube serves as the auxiliary protection sleeve. Together, they form a composite protection tube, providing excellent overall performance, such as resistance to cutting flames, thermal shock, or mechanical damage.