Non-Contact Geomagnetic Localization of Pipeline Defects Using Empirical Mode Decomposition and Magnetic Gradient Tensor

Non-contact geomagnetic anomaly detection, as one of passive non-destructive testing (NDT) techniques, can be used to locate pipeline defects, while its accuracy is affected by random noise and detection orientation. In order to extract effective geomagnetic anomaly signals of pipeline defects, a method based on empirical mode decomposition (EMD) and magnetic gradient tensor was studied. In order to filter random noise, EMD was performed to self-adaptively decompose magnetic field signals into a series of intrinsic mode functions (IMFs), and then Hurst exponent was implemented to exclude false modes; The calculation method of magnetic gradient tensor modulus (MGTM) was proposed to obtain precise defect locations according to tensor symmetry; Subsequently, the remote pipeline defect model was built based on the magnetic dipole theory, and the relationship between detection orientation and MGTM was discussed. The experimental results showed that the proposed method could realize high precision and reliable non-contact geomagnetic localization of pipeline defects.