Noncontact steel pipeline corrosion detection method with harmonic magnetic field excitation and an integrated sensor probe

Rapid and reliable defect detection for concealed pipelines is critical for maintaining industrial safety. However, the lift-off distance required for detecting such pipeline defects results in diminished responses from the receiving array elements, decreasing the sensitivity of the detection and complicating defect identification and evaluation. To address this issue, a novel high-sensitivity probe that uses harmonic magnetic field excitation (HMFE) and integrated sensors consisting of a modified pickup coil and an improved tunnelling magnetoresistive (TMR) bridge (as a receiver) is used to measure magnetic fields. The HMFE technology amalgamates carrier and alternating magnetic fields, which mitigates the eddy current (EC) attenuation by modulating the magnetic permeability of steel conductors, thereby increasing the detectability of pipeline defects. The modified pickup coil has favourable stability and immunity to interference, and the improved TMR bridge circuit has high sensitivity (4.787 V/[email protected] V) and low noise density (150 pT/√Hz@1 Hz) to capture minor magnetic field variations. The receivers are arranged in a cross-shaped array, and a numerical model based on the magnetic dipole moment outputs the optimal measurement direction. A prototype probe was developed and tested for weld seam location and defect detection in single and parallel pipelines. The experimental results demonstrate that the probe has favourable sensitivity and can locate weld seams and recognize corrosion defects with a high signal-to-noise ratio of 19.82 dB at a 0.7 m lift-off distance via the output of the data fusion model.