Thermowells are recommended whenever a temperature element is to be inserted into a process where corrosion, pressure, abrasion, or shear forces may threaten the life of the element. In addition, thermowells allow for a defective instrument to be removed without shutting down or draining the process.
There are 3 broad categories: screwed, flanged, or weld-in, and can be designed to accept thermocouples, RTDs, temperature gauges or filled systems. Thermowells can be machined from solid barstock, or fabricated from pope. Fabricated thermowells offer a lower cost option, provided high pressure is not a design consideration.