Defect separation considerations in magnetic flux leakage inspection
The magnetic flux leakage (MFL) method is used for assessing the corrosion integrity of oil and gas pipelines. The interpretation of defect-induced magnetic signals has to take into account the inspection tool and pipeline steel characteristics. The MFL signals are very sensitive to the stress state and magnetisation level of the specimen. The presence of a material-loss defect influences both the stress and magnetisation distributions in the material. Moreover, clustering of the corrosion defects complicates this situation by superposition of the local stresses and by magnetic shielding in the region between defects. In this paper, the degree of interaction between two adjacent metal-loss defects is analysed as a function of the defects’ centre-to-centre separation, residual and applied stresses, and magnetic flux density. The necessary centre-to-centre separation for two defects to be considered interacting is evaluated by extrapolation of the magnetic signal features of known defect geometries.
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Document Type: Research Article
Affiliations: Department of Physics, Queen's University, Kingston, Ontario, Canada
Publication date: 2005-05-01
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- Official Journal of The British Institute of Non-Destructive Testing - includes original research and devlopment papers, technical and scientific reviews and case studies in the fields of NDT and CM.
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