Use of magnetic Barkhausen noise and magnetic flux leakage signals for analysis of defects in pipeline steel
- S.N. Bose National Center, Calcutta (India)
- Pipetronix Ltd., Concord, Ontario (Canada)
- Queen`s Univ., Kingston, Ontario (Canada). Dept. of Physics
Oil and gas pipelines are normally buried. They are inspected, while they are in service, by pumping tools through the lines. Inspection tools based on magnetic flux leakage (MFL) measurements are the most economical method used for detecting metal loss, such as corrosion pits. Here the authors report on studies of the effects of hoop and axial tensile stresses on magnetic flux leakage (MFL) signals from 50% penetration electrochemically milled pits eroded in line pipe steel. It is observed that stress can change the MFL signal by more than 50%, depending on the magnetization of the pipe wall. The studies were performed on pits created in both the absence and presence of 330-MPa hoop or axial tensile stress. The MFL results obtained in the two cases show detectable differences if the applied stress is high enough to create plastic deformation in the regions of stress concentration near the pits. The effect of stress applied during pit erosion is less than that when the same stress is applied during the subsequent measurements. Magnetic Barkhausen noise (MBN) measurements have been used to study the stress concentrations around electrochemically milled and mechanically drilled defects and have shown that significant additional stress and plastic deformation can be introduced during mechanical drilling. The MBN results are used to assist interpretation of the stress-dependent MFL results.
- Sponsoring Organization:
- Natural Sciences and Engineering Research Council of Canada, Ottawa, ON (Canada)
- OSTI ID:
- 357660
- Journal Information:
- IEEE Transactions on Magnetics, Vol. 35, Issue 3Pt2; Other Information: PBD: May 1999
- Country of Publication:
- United States
- Language:
- English
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