Adaptive wavelets for characterizing magnetic flux leakage signals from pipeline inspection

Natural gas transmission pipelines are commonly inspected using magnetic flux leakage (MFL) method for detecting cracks and corrosion in the pipewall. Traditionally the MFL data obtained is processed to estimate an equivalent length (L), width (W), and depth (D) of defects. This information is then used to predict the maximum safe operating pressure (MAOP). In order to obtain a more accurate estimate for the MAOP, it is necessary to invert the MFL signal in terms of the full three-dimensional (3-D) depth profile of defects. This paper proposes a novel iterative method of inversion using adaptive wavelets and radial basis function neural network (RBFNN) that can efficiently reduce the data dimensionality and predict the full 3-D depth profile. Initials results obtained using simulated data are presented. Index Terms--Adaptive wavelets, iterative inversion, MFL inspection, RBFNN.