Surface Thermometers

Surface Thermometers

Surface thermometers are non-invasive instruments that infer the medium temperature by contacting only the outside surface of a pipe, reactor, or vessel. They are well suited to demanding industrial conditions and to retrofit or temporary measurement needs for energy and safety monitoring, because installation does not require opening the process boundary; key advantages include no leakage risk, no process shutdown, and reduced engineering effort (including avoiding thermowell wake-frequency calculations).

Because the sensor does not penetrate the wall, performance depends on heat transfer through the pipe/vessel material and the quality of thermal coupling at the contact point. Proper mounting force, insulation strategy, and knowledge of wall thickness and material properties are essential to reduce offset and improve dynamic response.

The benefits are primarily risk and cost avoidance. Non-invasive measurement eliminates pressure boundary modifications, avoids wear mechanisms associated with thermowells in abrasive or corrosive media, and preserves flow steadiness by removing obstructions. This makes surface measurement attractive where invasive measurement is impractical, risky, or too expensive to justify.

Typical applications include high-flow and high-pressure lines, viscous or corrosive services, abrasive slurries, piggable pipelines, and small-diameter piping where thermowell installation is challenging. Surface “skin” measurements are also used on fired heaters and heat exchangers to monitor tube skin temperature trends and identify abnormal heat transfer behavior.

Selection centers on required accuracy versus invasiveness, mounting method, ambient temperature limits, and the communication interface needed for the control or monitoring layer. Best results come from standardized installation practices - consistent contact preparation, repeatable mounting torque, and insulation detail - to reduce measurement spread across comparable points.

Instrumentation and Controls., an exclusive authorized representative of sales and service for Endress+Hauser.