Research Of Tri-axial Magnetic Flux Leakage Pipeline Defect Inspection Technology

In the modern society of high-speed development, with the progress of science andtechnology, the energy is becoming more and more in need. And the energy transportationsafety is becoming more and more attention from people. Due to the security, effectivenessand economy etc, the pipeline transport has become the main method of all kinds of energytransportation. In recent years, the pipeline safety issues are increasing with the large areaof pipeline laying and the increase of the usage. The major problems of nondestructivetesting field are how to find oil pipeline safety hidden trouble timely and find out theproblem when testing.This task has an in-depth study on pipeline MFL detection technology. Base on theMFL detection principle, the defect leakage magnetic field is divided into axial, radial andcircumferential components, and the tri-axial MFL defect inspection technology is putforward. On that basis, the pipeline defect tri-axial MFL inspection technology is studied.Using ANSYS finite element simulation software, the tri-axial MFL defect inspectionsimulation module is built. With the3-D simulation analysis of the module, the magneticdensity curves of the axial component, radial component and circumferential component ofthe defect leakage magnetic field are obtained. Comparing the magnetic density curves ofthe leakage magnetic field in the situation of with and without defect on the measured steel,theoretical basis and reference of judging the defect of unit under test are provided.Proceeding the3-D simulation of two situations of defect size change and lift-off valuechange. The influence law defect leakage magnetic field is judged base on the graph ofthree components.The experimental platform is developed base on the principle of tri-axial MFL defectinspection technology. Using the tri-axial MFL test probe made of Hall sensor, themeasured steel with defect is detect in pros and cons to simulate the judgment of internaland external injury of pipeline. There are separately long and narrow cracks in axial andnarrow laying on the measured steel with the same size of length, width and depth. Andcollecting and contrasting the corresponding leakage magnetic field in three directions of the leakage detection signal. Multiple amplification filter circuit is designed and the PCBboard is made to amplificatory and filters the defect MFL signal collected by the tri-axialMFL test probe. After the analog-to-digital conversion of the Data Acquisition Card, thecorresponding digital signal is deposited into the computer and then the data analysis ispreceded. With the analysis and compare of the MFL signal in three directions, thefeasibility and advantage of the technology are proved.