Background The significant feature of the remote field ECT method is that the two coils that consist of the ECT probe, the excitation and search coil, are separated by twice of the testing pipe outer diameter. Consequently, the probe length increases and makes it difficult to insert into the bent part of the testing pipe. Object This paper aims to propose a compact probe design for the RF-ECT with ferromagnetic shield rings and to verify effects of reducing the probe length and its compact design on detection sensitivity. Method This research, three types of eddy current testing probe ware fabricated, and their detection performance was compared based on their detection sensitivity. Furthermore, nonlinear eddy current analysis using the 3D finite element method was employed to analyze the effect of ferromagnetic rings on detection sensitivity. Result In the measurement result, ferromagnetic rings that combined into the RF-ECT probe makes the probe length decrease. In addition, the detection sensitivity of proposed probe is significantly improved compared to the conventional RF-ECT probe. According to the results of FEM analysis, it was found that the change of the phase angle between the average flux density in the search coil due to the excitation current and due to the eddy current increased compared to the conventional RF-ECT probe, and it contributes to improve detection sensitivity. Conclusion This research investigated the effects of the proposed probe with ferromagnetic rings on probe length reduction and defect detection sensitivity to make the remote field eddy current testing probe compact. This research does not require an ethical statement.
Komatsubara et al. (Mon,) studied this question.