Factors Affecting Pipeline Flaw Detection and Measurement. Annual Report, May1996-April 1997

摘要

The following report focuses on two techniques for pipeline flaw detection andmeasurement: Magnetic Flux Leakage (MFL) and Remote Field Eddy Current (RFEC). A number of factors influence MFL signals, the least understood of which are stress and the variation in magnetic properties. In addition to bulk stress, local defect-induced stress concentrations can influence the MFL result significantly. This project therefore continues fundamental research on the effects of line pressure stress on MFL signal patterns. Defect-induced stress concentrations have been determined using neutron diffraction and magnetic Barkhausen noise (MBN) measurements, for correlation with MFL results. Finite element calculations have also been carried out to determine the effects of magnetic anisotrpy on MFL signals from pits of different shapes. First estimates of stress correction factors for MFL signals have been produced.