Advanced Multifrequency Eddy-Current System for Steam-Generator Inspection

A research project conducted for the Electric Power Research Institute has resulted in substantial improvements in the assessment of steam-generator integrity. The objective of the work was to determine the maximum advantage of multifrequency methods for the inspection of steam generators. Advanced multifrequency technology has been developed under the program and has been implemented into a prototype system that uses both differential and absolute data simultaneously from four test frequencies. Multiparameter processing of the data results in very effective elimination of unwanted parameters such as support plates, probe wobble, dents, and other dimensional variations. The information of interest, flaw depth, is preserved in this process and is no longer masked or altered by the unwanted data. The availability of both differential and absolute multifrequency data significantly extends the range and accuracy of the flaw-sizing process, and enables the profiles or contours of larger volume flaws to be obtained.