Steam tube defect characterization using eddy current Z-parameters

Steam generator tubing inspections use the impedance of a differential eddy current probe inside a tube as an indication of incipient failure. An axis ymmetric finite-element computer code has been developed and utilized to ca lculate the impedances of the differential probe. The calculated values hav e been validated by comparison with experimental results. A Z-parameter mod el for a probe inside a steam tube utilizing differential coils is describe d, and the response of Z-parameters for the differential probe under variou s changes in the steam tube configuration is investigated.