High-temperature piezoelectric transducer for continuous online thickness monitoring


Improving reliability of components operating at high temperature, such as pipelines and boilers, within a variety of industries is of importance in the asset management process, and is implemented via regular inspections and condition monitoring. Performing online inspections without the need for plant shutdown is highly desirable. This work details the development and testing of a piezoelectric transducer, suitable for both portable or permanently installed high temperature ultrasound thickness monitoring. This transducer design incorporates compression, applied via a central bolt, to achieve acoustic coupling between the components, avoiding the use of adhesive layers. With the application of a bismuth titanate piezoelectric disc, the transducer is able to withstand temperatures of up to 500 ˚C, without cooling. The transducer has been tested at 350 ˚C using commercially available high temperature couplants on a stainless-steel sample, providing a signal-to-noise ratios (SNR), in the region of 20 dB. Further testing has been implemented with the use of dry clamping up to 450 ˚C, with both aluminum and nickel foil layers, generating a SNR of up 27 dB to on a stainless-steel sample. This transducer design has been tested at 500 ˚C for over 200 hours, showing its suitability for application in high temperature ultrasound thickness monitoring.