Research On The Principle And Method Of External Penetrating Rotating Electromagnetic Field Detection

As the main transportation carrier of petroleum and other energy,pipelines are widely used in industry.Because pipelines are mostly laid in extremely harsh environments,and the age of pipelines increases year by year,various damages will occur.In this paper,in view of the deformation,corrosion,cracks and other defects of the pipeline,the external penetration rotating electromagnetic field detection technology is used to carry out research on the pipeline,so as to ensure the safe operation of the pipeline.The externally penetrating rotating electromagnetic field detection technology is used to detect the outer wall of the pipeline,which can cover the entire outer surface,and all defects can be detected in one scan.Unlike the traditional eddy current detection technology,the externally penetrating rotating magnetic field detection technology can realize the detection of the outer wall of the pipeline.The fast positioning of defects can detect defects in any direction on the surface of the pipeline,and has the characteristics of high detection efficiency and not easy to miss.In this paper,the theory and mathematical model of the externally penetrating rotating electromagnetic field are first studied,and the three-dimensional finite element model of the external penetrating rotating electromagnetic field detection technology is established,the sensor optimization design of the external penetrating rotating electromagnetic field detection technology is optimized,and the external penetrating rotating magnetic field detection technology detects defects.Research on the influencing factors and quantification methods,and finally set up an externally penetrating rotating electromagnetic field detection system for experimental research,and design other types of sensors based on rotating electromagnetic field detection technology.The thesis mainly conducts research from the following five aspects:(1)Theoretical research on the external penetration rotating electromagnetic field detection technology and the establishment of finite element modelThe theory and mathematical model of the rotating electromagnetic field are analyzed,and two externally penetrating rotating electromagnetic field detection sensor models are established by using finite element: the simplified model of the distributed wire column and the non-simplified model of the centralized coil.Two models were used to detect defects,and the feasibility of the two models was verified.The distribution of the eddy current generated by the externally penetrating rotating electromagnetic field detection sensor on the outer wall of the pipeline and the interaction between defects and eddy currents are also studied.The results show that the axial magnetic field can be used as the characteristic signal of the external penetrating rotating electromagnetic field detection technology.(2)Design of outgoing rotating electromagnetic field detection sensorThe external penetrating rotating electromagnetic field detection sensor has been optimized and designed,and the changes of the background magnetic field with the sensor parameters when the pipeline is defect-free and the change of the characteristic signal under different sensor parameters when the pipeline is defective are respectively explored,and finally determined A set of optimal sensor design schemes were developed,which laid the foundation for subsequent research on influencing factors and experimental research.(3)Research on influencing factors and defect quantification method for external penetration rotating electromagnetic field detectionThe influence of different influencing factors on the detection results of the externally penetrating rotating magnetic field detection sensor was explored,and the coil excitation frequency,defect circumferential position,pipeline inclination angle,defect direction,presence or absence of iron core,and the shape of the excitation coil were studied.The relationship between the signals,and finally a set of defect quantification methods is determined through the characteristic signals.(4)Construction and experimental research of external penetration rotating electromagnetic field detection systemAn externally penetrating rotating electromagnetic field detection system was built,and the pipeline was tested.The test results show that the test results of the externally penetrating rotating magnetic field detection system are consistent with the finite element results;when the circumferential position of the defect is different,the real and imaginary parts of the axial magnetic field will also change,thereby changing the angle of the impedance diagram;the pipeline is inclined There is an inconsistency in the size of the peaks and troughs;defects in any direction can be detected,and the law is consistent with the finite element results.(5)Design of dual rotating electromagnetic field detection sensor and rotating electromagnetic field sensor based on impedance analysisTwo other types of sensors based on the principle of rotating electromagnetic fields are designed: detection sensors based on double rotating electromagnetic fields and rotating electromagnetic field sensors based on impedance analysis.The finite element analysis of the two sensors is carried out,and the defects are detected.The results show that both types of sensors can realize the rapid location of defects,which provides a new direction for the future research of rotating electromagnetic fields.Two other types of sensors based on the principle of rotating magnetic field are designed: a detection sensor based on dual rotating electromagnetic fields and a rotating electromagnetic field sensor based on impedance analysis.Both types of sensors can realize the rapid location of defects,which provides a new direction for the future research of rotating magnetic field.