Research On Non-destructive Testing Method Of Pressure Pipeline With Coated Layer By Pulsed Eddy Current Technology

Coated metal pressure pipes are used to transport crude oil,water,steam,liquid vapor and other products in the petroleum,gas,chemical and other industries.The interior is usually high temperature,high pressure,and corrosive working environment,which is easy to cause the internal and external surfaces of the pipeline to appear.Defects such as scaling,cracks,perforations,stress corrosion,etc.,the long-term existence of these defects will cause pipeline failure and easily lead to safety issues.In order to better ensure the safe operation of pipelines,a safe and reliable non-destructive testing technology is urgently needed.Pulsed eddy current(PEC)is an emerging nondestructive testing technology.The pulsed excitation source is a square wave signal with rich frequency components.The detected signal contains more information about the properties of the specimen.Because the pulsed eddy current testing method does not require the probe There is no need for couplant to contact with the test piece,and its detection has the advantages of strong penetrating power,wide range,strong ability,and fast speed.Therefore,there is no need to strip the outer coating layer of the pipeline in the industrial field inspection,which can meet the online inspection requirements of the pipeline under the coating layer.This dissertation uses pulse technology to detect different types of defects and welds in pipes with coatings.Through numerical simulation and experimental verification,the detection of pipeline defects and welds under the cladding layer is realized.First,starting from the analysis of electromagnetic induction theory,use the finite element software COMSOL to establish two-dimensional finite element models of different types of pipeline defects and welds,and study the subsurface defects of the cladding pipe,the surface defects of different widths/depths,and the width/height The welding seam affects the pulsed eddy current detection voltage signal.The simulation results show that the peak value of the detected voltage decreases as the depth of the subsurface defect increases;as the width/depth of the surface defect increases,the peak value of the detected voltage shows a downward trend;The increase in the width/height of the weld of the test piece corresponds to a decrease in the peak value of the detected voltage.Secondly,based on the pulse eddy current system testing platform,two sets of pulse eddy current probes are designed for the experimental detection of pipelines with artificial defects and welds,and the characteristic values of the detected voltage signals are extracted and effectively processed and analyzed.The experimental results of the two sets of pulse eddy current probes Consistent with the COMSOL simulation results,the results show that the detected voltage peaks change significantly at the defects and welds of the cladding pipes.The two sets of pulsed eddy current probes can use the detected voltage peaks to realize the detection of cladding pipe defects and welds.Finally,the polynomial fitting of the peak value of the detected voltage signal obtained by the experiment is used to predict the defects and welds of the cladding pipe.It comprehensively shows that the pulse eddy current technology proposed in this topic can be effectively used in the detection of cladding pipelines by using the peak value of the detected voltage signal,and has a wide range of engineering application value for solving the detection of pipelines under the cladding.