Research On Remote Field Eddy Current Inspection Of Pressure Pipeline Defects

Pressure pipes are widely used in long-distance oil transportation,steam transmission in power plants,urban heating,and other industrial or public facilities.Due to the complex flow conditions of the high-pressure pipeline,the inner and outer walls of the pipeline are likely to form local corrosion defects under the influence of the corrosive environment,and these defects will bring hidden dangers to safe production,cause accidents in the pipeline network and be forced to shut down,which directly affects the construction period.Bring huge economic losses to operating enterprises.Therefore,it is necessary to conduct health monitoring of pipelines,intelligent diagnosis and prediction of industrial pipelines,and safe and reliable detection.A comprehensive comparison of conventional nondestructive testing technology,because the remote field eddy current testing technology makes up for the shortcomings of conventional eddy current testing of shallow depth and narrow application range,the amplitude change of the defect signal is used to detect the defect,and the phase change can also be used to achieve the depth of the defect.In addition,it is convenient to realize automatic continuous detection.The basic theory of remote field eddy current testing technology is introduced in the article.Based on Maxwell's equations,the mathematical model of remote field eddy current testing,the mechanism of magnetic field propagation,and the calculation method of induced voltage in the detection coil are derived,which provide the theoretical basis for the numerical analysis of remote field eddy current testing in this article.Using the finite element numerical method,the eddy current detection situation of the pipeline's full-circumferential defect is analyzed.The magnetic field is used to locate and quantitatively analyze the defect in the pipeline,and it is obtained that the amplitude and phase of the axial magnetic induction intensity have a certain mutation at the defect position,and the change value is proportional to the change curve of the pipeline defect depth,which is the actual pipeline defect detection Provide reference basis.In order to obtain the remote field eddy current response signal of actual defects,a three-dimensional finite element simulation of the remote field eddy current detection of pipeline non-full-circumferential defects was carried out.The finite element simulation model of non-full-circumferential defects is established,and the half-circumferential defects,circular hole defects and axial defects are simulated to obtain the magnetic field signal of the defect,and the relationship between the axial sink signal and the size of the defect is analyzed.The overall design of the remote field eddy current inspection system for pressure pipelines was carried out,and three kinds of artificial defects were produced:full-circumferential defects,non-full-circumferential defects,and round hole-shaped defects,to test the performance of the system.The results show that the remote field eddy current detection of round hole-shaped defects is slightly worse than that of full-circumferential defects,but the phase of the detection signal is also approximately proportional to the defect depth;the system has poor detection capabilities for non-full-circumferential defects.When it is deep,it has a certain detection ability and can detect groove defects with a depth of 3mm.