Jiuhao Ge

Application of induced circumferential current for cracks inspection on pipe string

Pipe strings (such as drill pipe, tube, pipeline, riser) are critical facilities in oil & gas industry, which are highly susceptible to cracks caused by stress corrosion and fatigue damage. The most common defects are longitudinal and transverse surface cracks on pipe strings in oil & gas industry. Conventional nondestructive testing (NDT) methods are inadequate for these surface cracks on pipe strings. In this paper, a full 360° circumferential current induced by a coaxial excitation coil is present for inspection of longitudinal and transverse surface cracks on pipe strings. The finite element method (FEM) is employed to obtain characteristics signals by analyzing the distorted electromagnetic field above the cracks. The induced circumferential current test system is set up and crack inspection experiments are carried out. The results show that both longitudinal and transverse surface cracks can be detected effectively at one pass scanning on pipe string using the induced circumferential current.

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.