A Novel Magnetoelectric Composite Probe for Dynamic and Rapid Inspection of Minor Metal Loss Defects in Pipelines

The development of oil and gas pipelines in the direction of large diameter, high pressure, high steel grade has put forward higher requirements for pipeline inspection technology. Traditional magnetic flux leakage (MFL) internal inspection techniques suffer from low micro-metallic defect inspection rates and are significantly affected by the velocity effect. Similarly, eddy current (EC) internal inspection technologies exhibit limitations in the inspection capability of internal wall defects and are noticeably influenced by lift-off effects. This paper addresses these challenges by analyzing the signal patterns of pipeline defects under the superposition of axial direct current constant magnetic fields and radial alternating magnetic fields, considering the impact of velocity effects on defect signals. A novel approach is proposed, combining MFL and EC inspection methods for inspecting micro-metal loss defects, referred to as the magnetic-electric composite inspection method. A dynamic and fast inspection magnetic-electric composite (MagEC) probe is developed to implement this approach. Laboratory experiments were conducted to test the inspection capabilities of the probe for crack-like defects and pinhole defects. Cracks with a minimum width of 0.1mm and pinhole defects with a diameter of 3mm and above can be inspected. The probe was further incorporated into a 1219 mm multi-physics field comprehensive internal inspection device, and pulling tests were conducted. The results indicate that the magnetic-electric composite probe can effectively identify various types of pipeline micro-metal defects, with differential sensitivities of the MFL and EC sensors to internal and external wall defects.