Research On Eddy Current Testing System For Weld Positioning Under Non-Conductive Coating

As the infrastructure of the petrochemical industry,pipelines and storage tanks bear the task of transportation and storage,and their safety and reliability are the key to ensuring normal production.Welds are the structural connections of pipelines and storage tanks,and they are also the areas most likely to cause safety hazards.It is particularly important to carry out regular inspection and maintenance.The application of non-conductive coating on the surface of pipes and storage tanks makes it impossible to directly identify the position of the weld.Therefore,the detection of the position of the weld is a prerequisite for the evaluation of the weld.However,non-conductive coatings limit the application of advanced detection technology in this occasion.Eddy current non-destructive testing technology has the characteristics of non-contact,nondestructive,no coupling,fast detection speed,and suitable for online monitoring.It is an effective method to solve the weld position detection under the non-conductive coating.Based on the eddy current testing technology,this paper conducts in-depth research on the eddy current testing system of the weld position under the nonconductive coating through modeling simulation,system development,and experiment.The main research contents are summarized as follows:1.Simulation research on eddy current testing of weld position under nonconductive coating.According to the theory of eddy current testing and finite element modeling,combined with the types of welds under non-conductive coatings,COMSOL is used to establish eddy current signal models for welds without and with reinforcement.On this basis,parametric scanning was used to simulate the eddy current signals of different coil positions,and the law of the coil impedance changing with the coil position in the two types of weld inspection process was revealed,and the influence of excitation signal frequency,coating thickness,and the coil outer diameter on the test results were explored.2.Development of eddy current testing system for weld position under nonconductive coating.According to the coil signal detection and eigenvalue extraction requirements,the system development plan is designed,and the system is researched from the hardware and software levels respectively.Firstly,take STM32 as the microcontroller,direct digital frequency synthesizer as the signal source,74HC4051 as the array sensor channel selector,and AD8302 as the signal conditioning unit to design each part of the testing system.Secondly,based on the coil structure and detection requirements,the array sensor package and system panel are designed.Then,the serial screen interface is developed based on DGUS Tool,Keil is used for hardware control program design,and Lab VIEW language is selected for system host computer software programming.Finally,the extraction program of weld profile is designed.3.Testing and evaluation of performance of eddy current testing system for weld position under non-conductive coating.Firstly,use Q235 B steel material to prepare welding seam position detection samples,and design the probe.Secondly,design an experimental program and use a three-coordinate instrument to build an experimental platform.Then,based on the amplitude and phase characteristics,the two types of welds under the non-conductive coating were tested,and the influence of the coil outer diameter,excitation signal frequency,and coating thickness on the test results was studied.Then,through experiments,the range of non-conductive coating thickness when the system can detect the weld is determined,and the performance of the system is evaluated.Finally,the weld profile extraction test and performance evaluation were carried out.The experimental results show that the developed system can effectively detect the position of the weld under the non-conductive coating.The research results obtained in this paper have important guiding significance for the in-depth development of the eddy current testing of the weld position under the nonconductive coating,and provides an effective and reliable solution for the detection of the weld position of the pipeline and storage tank.The paper has 93 pictures,19 tables,and 85 references.