Automating an eddy current test system for in-service inspection of turbine/generator rotor bores

The comparison of the results of eddy-current testing and magnetic-particle testing of rotor bore sections shows satisfactory correlation if the eddy-current sensitivity is not excessive. Replacement of the present standard ferritic rotor bore tests with automated eddy-current testing thus allows continuity for recording purposes as well as improved repeatability and sensitivity where desired. use of eddy-current imaging techniques for automated processing, data extraction, and decision-making provides length estimates for surface breaking structures with error of about half a coil mean radius or less. A novel method, involving the surface integral of the threshold signal in the vicinity of an indication, can be used to estimate depth within 2:1; this capability is not available with magnetic particle data