管道漏磁内检测的管壁缺陷漏磁场解析模型

漏磁内检测技术是长输油气管道缺陷检测的主要手段,缺陷几何特征识别对管道安全运行评价具有重要意义。基于二维磁偶极子模型,建立管道内壁缺陷漏磁场空间分布的三维解析模型,对磁化方向垂直缺陷时磁荷产生漏磁场的变化规律进行研究;基于内壁解析模型,引入管壁退磁影响因子,对模型进行补偿,建立管道外壁缺陷漏磁场三维解析模型,得到了管道外壁不同缺陷漏磁场的分布特征。搭建漏磁检测实验平台,对所建模型有效性进行实验验证。结果表明,管壁对外壁缺陷漏磁场具有一定屏蔽作用,实验结果和理论分析具有很好的一致性,所建模型可有效描述管道内外壁缺陷漏磁场空间分布特性,对缺陷识别和定量评估具有一定工程指导意义。

Analytical model of magnetic flux leakage field of pipe wall defects based on magnetic flux leakage internal detection

Magnetic flux leakage internal detection technology is one of the means for detecting defects in long-distance oil and gas pipelines. The identification of geometric features of defects is of great significance to the safety operation evaluation of pipeline. Based on the two-dimensional magnetic dipole model, a three-dimensional analytical model of the spatial distribution of the magnetic flux leakage field of the inner wall defects of the pipeline is established, and the variation law of the magnetic flux leakage field generated by the magnetic charge when the magnetization direction is perpendicular to the defect is studied. Based on the analytical model of the inner wall, a demagnetization factor is introduced to compensate the model. The three-dimensional analytical model of the defect leakage magnetic field on the outer wall of the pipeline is established, and the distribution characteristics of the defect magnetic flux leakage field on the outer wall of the pipeline are obtained. An experimental platform for magnetic flux leakage detection is built to verify the effectiveness of the model. The results show that the magnetic flux leakage field of the outer wall has a certain shielding effect, and the experimental results are in good agreement with the theoretical analysis. The model can effectively describe the spatial distribution characteristics of the magnetic flux leakage field on the inner and outer walls of the pipeline, which has certain engineering guiding significance for defect identification and quantitative evaluation.