A lift-off revision method for magnetic flux leakage measurement signal

Magnetic flux leakage (MFL) measurement technique is commonly used in oil and gas pipeline integrity detection and defect estimation. Subject to the measurement condition, the lift-off effect is unavoidable which will affect the strength and trend of MFL signal seriously. In order to weaken the lift-off effect, this paper proposed a lift-off revision method to revise the measured signal down to a considerable level. Firstly, two corresponding signals at different lift-offs are measured. Then the signals are revised by a lift-off revision formula which is deduced based on the trend and depth-combination property of MFL signal. To demonstrate the feasibility and accuracy of the proposed method, the lift-off is revised not only from the simulation signals, but also from the experimental data of an artificial corrosion defect. In both cases, the proposed method shows a good performance for the lift-off revision of MFL signal.