Empirical structure for characterizing metal loss defects from radial magnetic flux leakage signal

Magnetic flux leakage (MFL) technique is one of the oldest and most commonly used technique for detecting corrosion in the pipe wall as well as pipeline features like welds, valves, supports, attachments, etc. The MFL data obtained is processed for detecting (isolating) defect or feature signal and characterizing it for the purpose of sizing or assigning a template. This paper discusses the methodology adopted for analysis of radial MFL signal. The characterization of the defects is based on primary and secondary parameters of the radial MFL signature. Primary parameters are axial and circumferential spread and amplitude of the signature. In addition, secondary parameters like shape and extent of the signature are also considered. Accuracy and confidence of sizing achieved by the proposed scheme are validated by several dig site inspections of actual buried oil pipelines.