Detailed investigations regarding the surface profile of the tubes were carried out using a novel technique called the projected interferometry method developed at the author's' laboratory. The projected interference pattern obtained from the cladding tubes revealed periodic diametral variations. The observations were further confirmed by cross sectional profiling.

To study the feasibility of detecting defects in such banded tubes, studies were carried out on tubes with artificial defects using single frequency and multi frequency eddy current methods. In view of unsatisfactory SNR obtained by the two methods a new method called the Phased Array Eddy Current Testing (PAECT) was used, with relatively successful results.

This paper discusses the use of the projected interferometry method as well as the relative performance of the three eddy current methods used for inspection. The specific advantages of the PAECT method in unambiguous defect detection in situations similar to the one encountered during the present investigations are also discussed.