Temperature Monitoring of Pipe Surface Using Ultrasonic-Strip Waveguide Sensor

Pipe temperature monitoring is crucial in the process industries, such as reactor pipes and heat exchangers. Suitable temperature sensors are required, and it is obvious to measure the temperatures frequently for coated and buried pipelines. Conventional temperature sensors (Thermocouple and Resistance Temperature Detector-RTD) have limitations like drift, durability, and junction failures. Measuring temperatures with the ultrasonic waveguide technique is optimal. Temperature-dependent material properties are “elastic moduli and density,” which influence the ultrasonic wave velocity to develop ultrasonic waveguide sensors for temperature measurement. Ultrasonic thin-strip waveguide sensors have a flattened surface than cylindrical waveguide sensors, allowing for better contact between the transducer and laying easily on the measurement region of interest. This study employs a shear wave transducer (0.5 MHz) in the pulse-echo technique to propagate S0 wave mode in a thin strip waveguide. We made notches on the strip waveguide with appropriate gauge lengths for transmitting and receiving ultrasonic signals. The strip waveguide and the co-located thermocouples are calibrated using the time of flight (ToF) shift from the sensor reflectors. The developed single-strip waveguide sensor for measuring pipe surface temperature along the circumference is easy to use, durable, and affordable. It is suitable to track the temperatures on pipe surfaces that are insulated, buried, or otherwise inaccessible.