Research Of Pipeline Magnetic Flux Leakage TRI-AXIAL Inspection Method Theory

The reserves of China’s coal, oil and natural gas are rich, but these resources are non-renewable natural resources. Our country’s oil and gas transportation mainly relies on pipeline, but security issues of active natural oil pipelines increase prominent. Thus high precision, fast, convenient pipeline detection of non-destructive testing technology has received more and more people’s attention.This task aiming at the defects of oil and gas pipeline, basing on pipeline magnetic leakage flux technology, study the operating principle and structure of pipeline leakage flux in-line detector. Pipeline magnetic leakage flux tri-axial in-line testing technology is used to realize the high precision identification and location of defects. The excitation device is one of the main factors effecting pipeline leakage flux tri-axial detector precision as an important component of pipeline leakage flux in-line detector. The permanent magnet property is studied to design the suitable magnetic parameters to optimize the pipeline magnetic leakage flux tri-axial in-line detector. The magnetic transformation inside magnetic materials under the outside magnetic field is studied from the microcosmic and macroscopic angle. Pipeline leakage tri-axial in-line testing theory is analyzed based on infinite element method combining Maxwell equation. Comsol Multiphysics simulation software is used to build up the tri-axial model to calculate magnetic leakage flux.Comsol Multiphysics simulation software is used to calculate the curve, contour, height expression of pipeline magnetic leakage flux tri-axial components thus the tri-axial components can be used to judge the defects by tri-axial component curves with defects or without defects. Comsol Multiphysics software is used to analyze the relationship between the geometric size and magnetic leakage flux around defects to supply the theory foundation for inversion and reconstruction of defects. The axial length, radial depth and circumferential width are changed to study the change of circumferential component of magnetic leakage flux around defects, as a result, circumferential component makes a little contribution to confirmation of defect size combining simulation and. experiment.