A Thermowell is a pressure tight receptacle designed to accept a temperature sensing element and provide a means to insert that element into a vessel or pipe. It acts as a barrier between a process medium and the sensing element of a temperature measuring device and protects against corrosive process media. A thermowell also allows the sensing element to be removed from the application while maintaining a closed system. The material chosen must be compatible with the process medium to which it is exposed.
The U-length (insertion length) of a thermowell indicates its insertion depth into a process vessel or piping system and is measured from the tip of the thermowell to the underside of the threads. Lagging extension thermowells are used on applications where insulation covers the vessel or piping system. The extension length (T-length) is the measurement between the instrument connection and process connection of the thermowell.
Thermowells for temp sensors are used for applications where the process media may be corrosive or contained under pressure. This is usually to prevent damage to the sensor and to facilitate the removal from the process . To prevent leakage of the process material, spring-loaded sensors must always be installed in a thermowell.
