Establishment of theoretical model of magnetic dipole for ground marking system

Ground marking system is an important device used in pipeline corrosion and leakage detector (MFL_PIG) for recording the exact time when the detector with strong magnets passes right below the above ground marker (AGM). The precision of AGM is critical to defect location during pipeline detection. In this paper, a theoretical model of magnetic dipole is established and its working principle and detail process are investigated thoroughly, and different situation of above ground markers layout are considered. Experiments are presented to verify the correctness of theoretical model. Different above ground markers laid on the ground perpendicularly or having a certain angle with the magnetic flux leakage, and traction experiments show that the results are satisfying.