Research On Resonant Magnetic Field Detection Technology Of Damaged Ground Steel Pipes With Insulation

The ground steel pipe with insulation is widely used in petroleum,chemical,electric power and other industries.With the development of insulated pipes transportation industry,the first problem is safety of pipes transportation.In order to effectively avoid pipeline leakage accidents,it is necessary to detect pipeline regularly.However,the existence of insulation brings great difficulty to detection.In this paper,a new nondestructive testing method is proposed for the damage detection of ground steel pipe with insulation.The new testing method is resonant magnetic field detection technology,it has the advantages of no downtime,the insulation does not be removed,high sensitivity,high reliability,good security,non-touch detection.In this paper,the systematic research on resonant magnetic field detection technology is done about the damage detection of ground steel pipe with insulation.First,the basic principle and detection method of resonant magnetic field detection technology are studied.The structure of detection probe is designed,including probe actuator,probe core material,probe detection device,probe array structure.Magnetic circuit analysis of the probe and magnetic saturation calculation are made.Optimizing probe structure by parameter calculation,determining the diameter and turns of the excitation coil of the probe and experimental safe current.Second,based on COMSOL multi-physical field simulation software,the magnetic field signals around the defective steel pipeline model with insulation are simulated and analyzed.Summarize the distribution law of magnetic field in the pipeline model and the distribution law of magnetic field when the probe moves along the pipeline direction.The influence of excitation current value,frequency of excitation current,thickness of pipeline insulation and number of turns of excitation coil on the magnetic field distribution of the probe moving along the pipeline direction is also studied.Then,the experimental platform of resonant magnetic field detection system is built.An experimental study on steel pipeline with insulation on the ground based on resonant magnetic field detection technology.Analysis of the distribution of magnetic field in x-axis,y-axis and z-axis triaxial testing is made.Data analysis and signal processing are carried out by using MATLAB,signal processing includes filtering and denoising,wavelet decomposition and reconstruction,separation of mixed signals,etc.Make the magnetic field signal at the defect intuitive and obvious.The influence of pipeline metal protective layer on test results is explored through experiments.The experiment is carried out in the form of two-probe difference to reduce the influence of harmonic excitation signal on defect signal.Finally,aiming at the problem that the probe exposed in the experiment and the error produced by the hand-held probe in the experiment,a scanner for pipeline inspection is designed,it is convenient for engineering application.The design includes three parts: internal structure,adjusting structure and sliding structure.Through parameter calculation,the final size and the range of pipe diameter that can be detected are determined,and the concrete implementation steps are listed.Through the above research,it is considered that the proposed resonant magnetic field detection method and the designed detection system can do damage detection for the ground steel pipe with insulation.It has good engineering application value and application prospect.