While evaluating the depth of corrosive defect of the pipe through Remote Field Eddy Current (RFEC) Testing technology, the critical principle of the process is to use the interaction of the magnetic field. Generally, exciter coils in the low-frequency alternating current and detector coils can generate the magnetic field. The signal curve can be transformed by receiving and plotting the induction voltage of detector coils. In addition, the signal curve can be used to identify the existence and the depth of corrosive defect from the shape and angle of the curve. Thus, the structure of the detector has a great influence on the exactitude of the testing. However, in the real experiment, RFEC probe is covered by shell and hard to disassemble. Thus, few people doing the research to analyze the structure of the RFEC probes. This research is based on two-dimensional axial-symmetry models and using Finite Element Method to simulate different structures or designs, such as the distance between exciter coils and detector coils, the amplitude and frequency of current in exciter coils, and even the material and size of shield. The simulation results show the influences of changing these important characteristics. Therefore, with these scenarios, the RFEC testing technology can be understood more completely and be improved the accuracy and reliability of the experiment by optimizing the sensibility of the RFEC probe.

While evaluating the depth of corrosive defect through Remote Field Eddy Current (RFEC) Testing technology, the researcher tried to investigate the signals of supporting plate which may produce variations by the thickness of supporting plate, diameter of tube hole in supporting plate, the value of crevice between tube and tube hole and tube wall thickness. Errors of evaluation of defect depth may consequently be identified or measured by the variations of the support plate signal. This study explores the effects of above four factors by experiments and an analysis of variance in statistics. By the analysis of experimental results, the researcher found the four influential factors would cause angle deviation of supporting plate signals. Except the factor of tube wall thickness, the deviation is not so substantial that the difference of evaluation in depth was consequently fallen into an acceptable range of engineering practices. When utilizing the remote field eddy current testing technique to test inservice tubes, the researcher found the thickness of inservice tube is normally different from the specified thickness of a standard tube. This variation consequently resulting in an evaluation curve produced by a standard tube may not lead to proper assessment of defects in inservice tube. To deal with the problem many researchers used a frequency compensation method to compensate for the evaluation error contributed by the variation of tube thickness on the basis of the standard ASTM E2096-00(2000). But the use of the frequency compensation method did not measure the inservice tube thickness and thus produced a drawback of consuming much time for the adjustment steps of compensation. Therefore, a mathematical compensation method was introduced in this study for the compensation of thickness variation derived from skin depth theory. This method in the present experiment is proven to be both feasible and reasonable through the derivation of the methodology. Generally, this study aims to apply the mathematical compensation method to overcome the drawback of frequency compensation method and to solve the problem of the difficulty in measuring inservice tube wall thickness in heat exchanger bundles.