High-Temperature Phased Array Inspection

High-temperature inspection offers considerable benefits for monitoring defects and corrosion during plant systems operation. This can save outage costs and permit better scheduling of repairs, as well as offering improved safety due to the ability to conduct routine monitoring. With extended maintenance cycles becoming common for many industries, targeted monitoring while systems continue operation will help prepare for shutdowns and will benefit the critical path nature of the shutdown. All ultrasonic inspections have issues to overcome with high-temperature inspection adding some supplementary considerations. Conventional and phased array inspection campaigns will need to address mechanical delivery of the probe along scan paths, couplant delivery, potential sensor damage and compensation for the beam skew caused by temperature effects on velocity. Phased arrays offer a convenient solution to the problem of velocity effects on refracted angles. A phased array technique enables the use of a wide variety of angles to achieve a volumetric inspection. By generating a sectorial scan (S-scan) the technique can target anticipated temperature range compensation and by monitoring component, wedge and array temperatures, the post-processing, by incorporating this compensation, can provide highly accurate results. This paper will present some mechanical solutions along with demonstration of the potential of encoded data collection enabling rapid acquisition followed by post-processing analysis. Reference signals to aid operators with the collection of quality data will be stressed and examples will be shown.

References
1. Ginzel, E. and R. Ginzel. “Study of Acoustic Velocity Variations in Line Pipe Steel,” Materials Evaluation, The American Society for Nondestructive Testing, Volume 53, No. 5, 1995. 2. Birks, A. and Robert E. Green, Jr. Nondestructive Testing Handbook, second edition: Volume 7, Ultrasonic Testing, The American Society for Nondestructive Testing, Columbus, OH, 1991 3. Selfridge, A. “Approximate Materials Properties in Isotropic Materials,” IEEE J. n Sonics and Ultrasonics, Volume SU 32, No. 3, May, 1985
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