Thermowells are used to protect temperature sensing elements such as Thermocouples, RTD’s, Bimetallic Thermometers, and Filled System Bulbs from breaking if they are installed in a tank, vessel, or pipe. Thermowells also allow a temperature measuring element such as a thermocouple, RTD, or bulb to be removed for servicing without the requirement that the plant be shutdown. Sometimes “Protection Tubes” instead of thermowells are used to protect thermocouples. These protection tubes are usually fabricated of ceramic materials and they are installed in high temperature flue gas and duct applications. Protection tubes are also available made of Inconel and with their ends open in order to improve speed of response and heat transfer.
Thermowells are used for almost all applications except for some specific applications (that is, for very-low-pressure air systems, for ventilating systems, bearing temperature measurement, lube oil drain in compressor and so on) where faster response required or space limitation such as casing drain in compressor. Temperature elements can be installed without Thermowells in following applications or condition exist,