Pulsed Remote Field Eddy Current Method for Identifying the Defect Location of Ferromagnetic Pipes

Defect location is critical information for building models in defect inversion analysis and formulating a reasonable repair strategy. The traditional remote field eddy current (RFEC) technique is widely applied for corrosion detection in ferromagnetic pipes but shows intrinsic deficiencies in defect location identification. Based on our previous work, we use the pulsed remote field eddy current (PRFEC) technology to address the issue due to its abundant excitation spectrum and lower power consumption. The magnetic flux distributions caused by inner diameter (ID) defects, outer diameter (OD) defects, and hybrid defects were respectively analyzed, and their signal responses acquired by an external RFEC probe were studied. Some critical parameters such as shield cages’ permeability, nonlinear pipe permeability, and pipe’s ovality were discussed. Finally, we show the numerical results of PRFEC modeling, whose characteristics extracted from the time-domain waveform can be used to infer the defect location. The numerical results show that: i) the defect location and ovality of pipes have a significant influence on the accuracy of detection results; ii) by taking the zero-crossing time of waveform as a signal feature, the defect location can be identified. The research results will provide the referenced values for the in-service testing of industrial pipelines.