Research On Pipeline Defect Detection And Recognition Method Based On Magnetic Leakage Principle

As an efficient means of transportation,oil and natural gas pipelines have developed into the top priority of China's modern industry and national economy,and are known as the "blood of energy." At present,some long-distance pipelines in China have gradually entered the aging stage.Due to the corrosion of the material of the pipeline and the damage caused by some external factors,there is a great potential safety hazard in the operation of the pipeline.In the magnetic detection device,the traditional permanent magnet excitation has difficulties in changing the magnetization,and after the excitation is interrupted,the pipeline still has residual magnetism,and it is difficult to repeat the test.The analysis of the signal distribution law has certain significance for the identification of pipeline defects.Aiming at the problems involved in the excitation device of traditional permanent magnet detection,the electromagnetic excitation magnetic circuit and the permanent excitation magnetic circuit model are mathematically modeled based on the electromagnetic field principle and Maxwell's equations to obtain the coil geometry parameters of electromagnetic excitation and the effect on the excitation effect;The difference between the magnetization effects of permanent magnet excitation and electromagnetic excitation is compared,and the calculation process of the electromagnetic field by the finite element method and the connection in the Comsol software are explored.Establish a simulation model with DC coil as the excitation source,optimize the model parameters,use Comsol to perform finite element simulation to solve the defects of different steel plates with the same material of the pipe wall,and study the magnetic flux leakage signal waveform of groove defects with different geometric characteristics Distribution law,select the characteristic value of the magnetic flux leakage signal curve,and obtain the mathematical relationship between the size of the defect and the characteristic value through curve fitting,build a DC electromagnetic excitation detection platform and conduct experiments to detect rectangular defective steel plates of different geometric sizes,by comparison The distribution characteristics and amplitude of the magnetic flux leakage signals in simulation and experiment verify the correctness of the simulation model.The results show that when detecting ferromagnetic materials such as steel plates and the same wall,the magnetization is proportional to the product of the number of coil turns and the excitation current,and the optimization of the simulated coil geometric parameters(turns and current size)can achieve the actual detection.Magnetization effect,and then replace the permanent magnet excitation environment,establish an electromagnetic excitation simulation model that can accurately describe the permanent magnet magnetic circuit;explain the geometry of the defect and the peak-to-peak spacing of the radial signal component of the magnetic flux leakage signal and the peak size of the axial signal component Equal feature quantities are related,and the size of the defect is quantified through regression analysis,and the mathematical relationship between the defect geometric size and the magnetic flux leakage signal can be obtained.The electromagnetic excitation simulation data is consistent with the experimental data trend and amplitude,which provides the possibility of identifying and quantifying pipeline defects in actual projects.