Thermowell

A thermowell is a closed-end tube installed in the pipe or vessel wall into which the temperature sensor slides. It carries the process pressure and takes the flow forces and the corrosion, so the sensor itself can be a standard mineral-insulated insert exchanged in minutes with the plant running. Choosing the well correctly is as important as choosing the sensor: a well that is too long or too slender for the flow can fail by vortex-induced vibration, and one that is too short reads the wrong temperature.

Wells are machined from solid bar stock for the best pressure integrity and surface finish, or fabricated from pipe for long insertion lengths and large diameters, up to 12 m subject to design verification. Process connections are threaded, flanged or weld-in, with pressure ratings to ASME Class 2500 for flanged and Class 3000 for threaded designs, and temperatures to 1,800 °C depending on material. Materials are 316 and 316L stainless steel, Hastelloy, Monel, Inconel, titanium, tantalum or gold-plated for hydrogen and highly corrosive service.

Every well can be supplied with a wake-frequency calculation to ASME PTC 19.3, material certificates, hydrostatic and NDT testing, surface polishing for hygienic duty and special cleaning for oxygen service. Plug and chain, and companion flanges are available.

Thermowells are used on pipelines, furnaces, tanks and reactors across oil and gas, petrochemical, chemical, refining, power, marine, water and general process industries.