A Thermowell is a cylindrical fitting that protects the integrity of the sensor by action as a barrier between the process and the sensor. Thermocouples are generally used in process piping and vessels to protect against high velocity flow, high pressure, and harsh environments.

Thermowells are created using barstock which is machined from one solid piece of hexagonal or round bar or are fabricated using multipiece welded and machined assemblies. They have threaded, socket weld, weld in process or flanged type connections.