So far, none of conventional magnetic shielding models can model a field long pipeline consisting of many welded short sections with different permeabilities. This paper demonstrates the magnetic shielding model of long pipelines via simulation analyses based on the finite element method (FEM) and experimental verifications of the magnetic shielding of short pipes, torus pipes, and field long pipelines. The radial and axial shielding factors of a finite pipe can be accurately calculated by the FEM. As the pipe length increases, the axial factor rapidly converges to a value less than 1, and the convergence value is independent of the pipe length because of the magnetic charges at the two ends. For a long pipeline consisting of many short sections, the averaged shielding factors over a couple of adjacent sections are equal to that of an ideal infinite pipeline, and the axial factor is always equal to 1. An “average” strategy for field pipeline orientations that employs the averaged magnetic fields and shielding factors over several sections is then proposed and demonstrated. As the geomagnetic field is taken as the absolute reference, this orientation measurement method has no risk of divergence over a long time and distance. Index Terms—cylindrical magnetic shield, magnetic fields, pipeline orientation.

中文翻译：

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以管道定向测量为目标的长管道磁屏蔽分析与验证

到目前为止，没有任何传统的磁屏蔽模型可以模拟由许多具有不同磁导率的焊接短段组成的场长管道。本文通过基于有限元法（FEM）的仿真分析和短管、圆环管和现场长管道的磁屏蔽实验验证，论证了长管道的磁屏蔽模型。FEM 可以准确计算有限管道的径向和轴向屏蔽系数。随着管长的增加，轴向因子迅速收敛到小于1的值，由于两端的磁荷，收敛值与管长无关。对于由许多短段组成的长管道，几个相邻部分的平均屏蔽系数等于理想无限管道的屏蔽系数，轴向系数始终等于 1。 场管道方向的“平均”策略，它采用了几个的平均磁场和屏蔽系数然后提出和演示部分。由于以地磁场为绝对参考，这种方向测量方法没有长时间和距离发散的风险。索引词——圆柱形磁屏蔽、磁场、管道方向。这种方向测量方法在长时间和距离上没有发散的风险。索引词——圆柱形磁屏蔽、磁场、管道方向。这种方向测量方法在长时间和距离上没有发散的风险。索引词——圆柱形磁屏蔽、磁场、管道方向。