A Sensor Liftoff Modification Method of Magnetic Flux Leakage Signal for Defect Profile Estimation

Abstract

Magnetic flux leakage (MFL) testing is the most widely used for the in-service inspection of oil and gas pipelines. The variation of sensors liftoff caused by vibration results in the distortion of the defect signals, thereby decreasing the estimation performance of the defect profile. In this paper, we discuss the effects of the detector vibration on the MFL signal and propose a sensor liftoff modification method of an MFL signal based on the finite-element method simulation. The proposed method mainly introduces a mapping algorithm to modify original measured signal and obtain pure signal. This mapping algorithm is constructed by iterative defect models closed to the real defect. The algorithm effectiveness is tested by using simulation and experiment data. The results demonstrate that the proposed method can improve the signal-to-noise ratio and estimate the profile more accurately.