Remote field eddy current technique applied to non-magnetic steam generator tubes

Unlike the impedance plane analysis form of common eddy current testing (EC T), the remote field eddy current (RFEC) technique is a through-transmissio n effect that reduces problems such as lift-off normally associated with EC T. In the inspection of steam generator (SG) tubes, the real issue is to de tect the minute cracks growing up from the outside. However, using ECT, it is considered infeasible to accurately find them from the inside because of the limitations of penetration of eddy currents. This paper describes a fi nite-element approach to the solution of time-harmonic electromagnetic fiel ds for the RFEC technique based on a magnetic vector potential and an elect ric scalar potential. A comparison is made of experimental and finite-eleme nt predictions of electromagnetic phenomena under the inspection of non-mag netic tubes. For the cracks outside demanding high sensitive and precise me asurements in the SG tube inspection, numerical results are given for param eters to design a RFEC probe. (C) 2001 Elsevier Science Ltd. All rights res erved.