A technology of multiple-harmonic magnetic field excitation and its signal-processing method for noncontact steel pipeline defect detection

Harmonic magnetic field focus detection technology has been utilized for in-service pipeline defect detection due to its advantage in providing high-sensitivity and noncontact detection. However, this technology encounters interference from background signals and noise during high lift-off detection, which limits the accuracy of defect signal extraction. To quickly and robustly identify pipe defects, this work discloses a novel defect signal extraction method for multiple-harmonic magnetic field detection technology. The proposed method is insensitive to noise interference, effectively extracting defect signals even under high-intensity noise conditions. A pipe defect model based on magnetic dipole moments is established for simulation analysis, and a pipeline test platform is built for experimental validation. The results demonstrate that the proposed method can identify defects from signals with a low signal-to-noise ratio of 5.7 dB and locate pipes, welds, and defects with high resolution.