Lightweight, High Performance Detection Method of Pipeline Defects Through Compact Off-Axis Magnetization and Sensing

This paper proposes a new lightweight, low cost, and high performance detection method of pipeline defects through compact off-axis magnetization and sensing. By deploying the magnetic sensor below the edge of the tiny magnet instead of its center, high magnetic sensitivity of defect detection can be achieved while magnetic sensing saturation can be avoided. It is experimentally demonstrated that both the sensitivity and effective lift-off value of defect detections are significantly enhanced. For various defects of different sizes and shapes, the sensitivity of the proposed scheme is mostly enhanced by 2–12 times and sometimes up to 20 times, compared with passive magnetic detection; the effective lift-off values are as high as 6 mm–13 mm, which exceeds conventional magnetic detection methods and is also much larger than the thickness of the protective polyurethane layer on the probe required by a field pipeline detector. In addition, speed independence as for the detected magnetic characteristics makes the proposed probe particularly suitable for the pipeline detector whose moving speed is unstable. Finally, its capacity of detecting a real oil-stealing hole is experimentally demonstrated.