The Research Of MFL Detection Method Of Inside Pipeline Weld Defects

Nowadays, Oil, Natural Gas are recognized as the most important energy in the world.They are occupied as a more and more important position in China’s national economy.Pipeline structure is widely used in the department of oil, natural gas transportation,chemical industry and urban construction. Pipelines are usually buried in the deep groundor under the sea. Due to the long-term use of the pipelines, cause the varying degreeserosion of soil and sea. If not timely serviced, the pipelines may lead to accidents. This willbe serious consequences for the national economy and social environment. According tostatistics, the detective of pipelines weld bead is one of the main factors in securityoperation. Therefore, the regular use of Non-destructive testing is significant for thesecurity in the normally used of the project.At present, the researchers at home and abroad have focused on pipeline wall defects,while ignoring other causation, such as pipeline welds, bends, tees and three links. Thistends to affect the test results in practice, which leads to an error of judgment. Due to thestructure characteristics of these parts, also can produce leakage magnetic field in thepipeline after being magnetized, if ignored the study of these parts of leakage magneticfield, is easy to be confused with defect leakage magnetic field, so it brought a lot ofinconvenience for pipeline detection and maintenance.This article discusses the basic structure and workflow of the magnetic flux leakagedetector, using magnetic flux leakage detection technology, focusing on different depths inthe pipelines weld defects in axial and radial variation of the magnetic leakage signal. Usethe finite element simulation software COMSOL established the pipelines whose diameteris8mm. The width of no weld and weld pipelines are respectively1mm,2mm in the leftand right side. Use the Two-dimension Axial Symmetry Pipeline Model whose symmetryaxis is the center of pipeline to simulate and analyze the conditions of defects at differentdepths. Including pipeline which has no defect contrasts pipeline whose weld has no defect;inside of the pipeline which has a defect contrasts inside of the pipeline whose weld hasdefect; inside of the pipeline whose weld has defect contrasts defects at different depths in radial direction; outside of the pipeline whose weld has defect contrasts defects at differentdepths in radial direction. Use COMSOL to get magnetic flux leakage signal ofpost-treatment in axial direction and radial direction. Then contrastive analyze of theresults. This provides a basis for the defect detection of pipeline at a later stage.