Receiver Signal Analysis on Geometry and Excitation Parameters of Remote Field Eddy Current Probe

Abstract

The traditional remote field eddy current (RFEC) testing is a method widely applied for detecting the corrosion and wall thinning in a ferromagnetic pipe system and shows intrinsic deficiencies in axial defects quantification due to the distinct probe structure. A circumferential alignment probe structure is used to improve the sensitivity to axial defects of pipes. Meanwhile, current approaches typically are incapable of classifying inner diameter (ID) and outer diameter (OD) defects of the pipe, which brings difficulties to the formulation of strategies in pipe repair. In this article, an external pulsed RFEC method is proposed to address these issues. First, we give a thorough analysis of the effects of probe geometry and excitation parameters on the output signal, targeting parameters optimization. Second, the finite-element model is built and used to analyze the relationships between the defect size and signal features under different excitation types. Finally, the improvements in probe performance and the ability to classify ID and OD defects are validated by measuring the defect depths of the pipe. Results showed that the zero-crossing time feature can be used to distinguish ID from OD defects. Thus, the proposed method is an effective complementary measure for the existing RFEC tools.