Research Of Pipeline Unsaturated Magnetic Flux Leakage In-line Inspection Technology

Pipeline transport is an important measure in energy transposition, It promotes thedevelopment of world economy. Ensure the safety of pipelines is one of the worldimportant issues. Pipeline magnetic flux leakage in-line inspection method has beensuccessfully used in the detection and early warning of the oil and gas network in thecountries across the world as one of the main methods of the detection for oil and gas.With the continuous development of Chinese economy, source has been used widely,and the length of oil and gas pipeline network construction has also increased greatly.Along with the using of local area networks which have been constructed in west-east gastransmission, SiChuan-east natural gas transmission project, Yangtze River Delta andZhujiang Delta, the safe operation for oil and gas pipeline network has been moreimportant, and the efficient, reasonable and high cost performance development andresearch of pipeline magnetic flux leakage in-line inspection have been more significant inindustrial application.This task is aimed at introducing the basic structure and working principle of thepipeline magnetic flux leakage in-line inspection detector and analyzing the main formedmechanism of oil and gas pipeline defect. The different reasons for the defect of the oil andgas pipeline and the multi-functional finite element analysis simulation software ANSYSare both introduced. This article summarizes this software’s basic function,the method andthe procedure of magnetic simulation, building up the2D physical model and3D physicalmodel for pipeline magnetic flux leakage in-line inspection detector.Through simulation, the influence of the defect character to magnetic flux leakagesignal is studied and then the defect character of pipeline inner and outer surface isanalyzed. The life-off value location of the Hall sensor is proved and also the exist ofcircumferential leakage signal when axial direction is magnetized has been discussed.This task is aimed at the defect problem which can’t be detected caused byunsaturated magnetic field and the smaller pipe wall defect, developing the experimentaldevice which is used to detect the steel plate magnetic flux leakage. This article introduced detection principle and each part of the structure are introduced. and3D simulation modelfor steel plate magnetic flux leakage experimental device is built up. By simulation,thecritical value of unsaturated magnetic field is found. Many experiments have been doneunder the different thickness plates, different geometry size defects, analyzing andstudying deeply the corresponding relationship between detection signal amplitude andelectromagnetic of different thickness plates.It is proved that the quantitative relation between magnetic leakage signal and surfacedefect by statistics analyzing to the data of experimental device. The research shows that,this device can detect the defect which is less than20mm thickness,10%upper and lowersurface depth of steel plates.In order to offer theory and basis for pipeline magnetic fluxleakage in-line inspection optimization, it is proposed that the influence of detector’smovement speed to detection signal.