The detection of axial cracks in pipe string using a feed-through ACFM probe

Pipe strings, as critical components in oil and gas industry, are highly susceptible to axial cracks for stress corrosion and fatigue damage. The conventional detection methods, such as magnetic flux leakage and magnetic particle inspection, are inadequate for accurately detecting a narrow axial crack. Alternating current field measurement (ACFM) technique is an electromagnetic inspection method capable of both detecting and sizing surface breaking cracks in metal specimens. This paper presents a novel feed-through ACFM probe used for axial cracks detection in pipe string. Both simulations and experiments are conducted to analyze the magnetic field disturbance above axial cracks and extract features for cracks recognition. The relationship between magnetic field features and the cracks is set up for quantitatively sizing cracks. The results show that the feed-through ACFM probe could make quantitative evaluation of axial cracks on the surface of pipe string.