Current deflection NDE for the inspection and monitoring of pipes |
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Affiliation: | 1. NDE Group, Mechanical Engineering Department, Imperial College London, London SW7 2AZ, United Kingdom;2. Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, OH 45221, USA;1. Imperial College London, Department of Mechanical Engineering, Exhibition Road, London SW7 2AZ, UK;2. E.ON Technologies (Ratcliffe) Ltd., Technology Centre, Nottingham NG11 0EE, UK;1. Structural Integrity & Composites Group, Aerospace Engineering Faculty, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, P.O. Box 5058, 2600 GB Delft, the Netherlands;2. Department of Industrial and Information Engineering and Economics (DIIIE), University of L’Aquila, Piazzale E. Pontieri 1, Monteluco di Roio, 67100 L’Aquila, AQ, Italy;3. Tomsk Polytechnic University, Lenin Av., 7, 634050 Tomsk, Russia;1. State Key of Power Systems, Department of Electrical Engineering, Tsinghua University, Beijing 10084, China;2. Department of Engineering, Durham University, Durham DH1 3HP, UK |
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Abstract: | Routine inspection of oil and gas pipes for time dependent degradation is essential. Pipelines are most commonly inspected using In-Line Inspection (ILI), however restrictions from pipe geometry, features or flow rate can prevent its use. Facility pipework rarely facilitates ILI, and external inspection often warrants the undesirable removal of the pipe insulation and cladding. This work investigates the applicability of a current deflection non-destructive evaluation technique for both the detection and growth monitoring of defects, particularly focusing on corrosion. Magnetic sensors are used to monitor variations in the spatial distribution of the induced magnetic flux density outside a pipe that arise from deflection of an injected electric current around inner or outer wall defects. An array of orthogonal magnetoresistive sensors has been used to measure the magnetic flux density surrounding six-inch schedule 40 seamless and welded carbon steel and austenitic steel pipes. The measurements were stable and repeatable to the order of 100 pT which suggests that the defect detection or growth monitoring of corrosion-type defects may be possible with a few amps of injected current when measurements are taken at around 50 mm lift-off. The sensitivity of the technique is dependent on factors including defect geometry, sensor lift-off, bends, variations in nominal pipe geometry or material properties, and the presence of ferromagnetic objects, each of which were investigated using either experiment or a validated finite element model. |
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Keywords: | Current deflection SHM Electromagnetic NDE Pipe NDT |
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