关键词: 油气长输管道, 裂纹几何特征, 漏磁检测, 有限元仿真模型, 定量分析

Abstract:

In order to improve the accuracy of magnetic flux leakage (MFL) detection for the long-distance oil and gas pipeline, the impact of the moving velocity of detector on MFL signals should be carefully considered. According to the principle of 3D finite element analysis, a transient mathematic model for the MFL testing system was established and used to stimulate and analyze the crack detection process of oil and gas pipeline. A model for the static MFL distribution of pipeline crack was derived from the Maxwell's equations.Based on the model, the circumferential eddy current of pipeline generated from the movement of the detector was quantitatively analyzed, furthermore, the characteristics of inverse magnetic field formed by the eddy current and its effect on the external magnetic field were evaluated. Finally, a finite element simulation model for the magnetic flux leakage of crack was derived under the condition of dynamic magnetization. The model can acquire the tested results of MFL signals corresponding to different cracks. The consistency between the actual physical experiments and simulation analysis of the MFL signals proved the effectiveness and correctness of the transient simulation model. The relations of the crack geometric parameters, such as depth, width and the peak-valley value of MFL signals were discussed, and their relative curved surface plots were also drawn. The results of simulation analysis may be as a reference for practical MFL detection of cracks in long-distance oil and gas pipelines.

Key words: long-distance oil and gas pipeline, geometric features of cracks, magnetic flux leakage detection, finite element simulation model, quantitative analysis