The objective of Nondestructive Testing (NDT) is to detect flaws in the components, and characterize them by their size, shape, orientation etc. so that decision on fitness for service of the components can be made. In the case of thin walled tubes, ultrasonic or eddy current examination is generally performed for detection of defects. During the inspection of thin walled stainless steel tubes used in nuclear application, defect indications were obtained by eddy current examination in two of the tubes. From the eddy current examination results, accurate sizing and orientation of these defects could not be determined. Hence a complementary inspection method was required for better characterisation of defects in the two tubes. Even though ultrasonic testing is a most promising technique for detection and characterization of defects, the interpretation of results with A-scan presentation, relies heavily on the skill and experience of the operator performing the test, which comes only by extensive training [1]. This problem is still complicated in the case of thin walled tubes since resolution achievable is poor due to small wall thickness and diameter, and also due to poor signal-to-noise ratio obtainable from fine size defects.
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