DIPOLAR MAGNETIC FLUX LEAKAGES FOR PIPELINE RECTANGULAR DEFECT CHARACTERIZATION: ANALYTIC APPROACH

Abstract

Magnetic Flux Leakages (MFL) find its application in non-invasive of Non-
Destructive Testing and Evaluation (NDT&E) to detect and characterized
defect in pipelines made from ferromagnetic materials. Various improvements
of MFL models have been investigated for defect quantification but still could
not achieve higher precision due to technical errors. We, therefore, propose
models that minimize the error generated by inverse MFL model for defect
quantification. Depth and width polynomial expressions were generated from
the peak values of the two MFL profile using polyfit function for their errors’
evaluation by varying depth at constant width and varying width at a constant
depth. The model gives a prediction of a rectangular defect quantification
based on dipolar magnetic charge model from the nature of the axial and radial
flux leakages profile. The proposed model used analytic expressions to
characterize the defect from the MFL signal. Among the three axes of the MFL
profile, only radial and axial profiles were used in this paper to quantify the
defect. The model improved the error margin and proved that the radial MFL
profile is best for the estimation of defect length along the scan axis direction
with nearly zero percent error while the axial MFL profile provides best results
for the evaluation of width and depth with 2.20% and 2.18%as maximum
percentage error. The proposed Radial and axial leakage profile analytical
models are simple and can be used for reconstruction of defect in inverse MFL
problem.