Thermowells

Thermowells

Thermowells are the process-wetted protective components of a temperature measuring point. They shield the temperature sensor insert from harsh conditions such as high pressure, high flow velocity, and corrosive media, and they allow the insert to be replaced without interrupting the process. Thermowell selection is influenced by mechanical design, manufacturing method, applicable industry standards, and plant certification requirements, making them a critical engineered element of measurement-point integrity.

Design families typically include welded (fabricated) thermowells, barstock (machined from a single piece), and forged constructions. Process connection options are broad and may include threaded, flanged, weld‑in, socket weld, compression fittings, clamps, and other hygienic interfaces. Extension neck options are available where thermal isolation, accessibility, or clearance for insulation and heat tracing must be considered.

Material selection is fundamental to survivability and compliance. Thermowells can be specified in stainless steels, higher alloys, and ceramics to address corrosion, erosion, and extreme temperatures. Standardized designs may follow DIN 43772, ASME B40.9, or NAMUR NE 170 conventions, supporting consistent mechanical expectations and documentation across global projects and multi-site standardization programs.

Manufacturing approach impacts both cost and performance. Welded thermowells are often cost-effective and offer substantial design flexibility, while barstock thermowells provide robust construction suitable for a wide range of applications depending on dimensions and material. Specialized barstock geometries - such as helical designs intended for high-velocity applications - address demanding flow regimes where mechanical loading and vibration behavior become key design constraints.

Hygienic thermowell variants extend these principles into sanitary design. Hygienic thermowells can be designed without welds or dead legs to support cleanability and aseptic performance, including tee and elbow thermowell geometries for short immersion lengths in hygienic piping, vessels, or tanks. Quick-release mechanical concepts can further simplify recalibration workflows while maintaining a hygienic, non-dismantlable process interface where required.

George E. Booth Co., an exclusive authorized representative of sales and service for Endress+Hauser.