THREADED THERMOWELL ASSEMBLY

Thermowells are used to protect temperature sensors used to monitor industrial processes while permitting accurate measurement. A thermowell consists of a tube closed at one end and mounted in the process stream. A temperature sensor is inserted in the open end of the tube, which is usually in the open air outside the process piping or vessel. The process liquid transfers heat to the thermowell wall, which in turn transfers heat to the sensor. Since more mass is present, the response time of the sensor can be reduced. However, if the sensor fails it can easily be replaced without draining the vessel or piping. To obtain accurate temperature measurement the recommended thermowell immersion length is ten times the outside diameter of the tip. The thermowell protects the instrument from the pressure, flow-induced forces and chemical effects of the process fluid. Typically a thermowell is made from metal bar stock bored to accept the temperature sensor with a NPT thread or flange for process mounting.