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Detection of Stress due to Corrosion through Passive Measurement and Analysis of Magnetic Fields. D Cowell 1 , S Staples 2 , C Vo 1 , P Jarram 3 , B Varcoe 2 , S Freear 1 1 School of Electronic and Electrical Engineering , 2 School of Physics and Astronomy , University of Leeds, UK
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Detection of Stress due to Corrosion through Passive Measurement and Analysis of Magnetic Fields D Cowell1, S Staples2 , C Vo1, P Jarram3, B Varcoe2, S Freear1 1School of Electronic and Electrical Engineering, 2School of Physics and Astronomy, University of Leeds, UK 3Speir Hunter Ltd, Long Bennington, Newark, UK Booth 429, CORROSION 2013 Information in this presentation is propriety to Speir Hunter Limited. Not to be disclosed without permission.
Overview • Motivation for remote stress measurement • Stress Concentration Tomography (SCT) • Magnetoelastic effects in steel • Experimental measurement of stress-magnetisation • Finite element modelling of stress • Finite element modelling of stress-magnetisation • Experimental magnetic field characterisation rig • Prototype SCT instrumentation • Initial field survey results STRICTLY PRIVATE AND CONFIDENTIAL
Motivation • Ageing global pipeline infrastructure • Non-invasive, remote, pipeline integrity assessment • Applicable to non-piggable pipelines • Non-interruption of pipeline service • No change to operating parameters • Detection of stress not geometry STRICTLY PRIVATE AND CONFIDENTIAL
Stress ConcentrationTomography (SCT) • Analyse changes in magnetic field along the pipeline • Reporting • Location of abnormal stresses • Metallurgical and mechanical conditions • Maximum allowable operating pressure (MAOP) • Safe operating term STRICTLY PRIVATE AND CONFIDENTIAL
Stress ConcentrationTomography (SCT) • Pipeline experiences stress • Corrosion Anomaly • Stress Corrosion and Metallurgical Defects • Slippage • Subsidence STRICTLY PRIVATE AND CONFIDENTIAL
Stress ConcentrationTomography (SCT) Length of anomaly 1 Length of Anomaly 2 Length of anomaly 3 Magnetic field Pipeline Defective section 1 Defective section 2 Defective section 3 STRICTLY PRIVATE AND CONFIDENTIAL
Magnetoelastic effects • Joule Magnetostriction • Change in sample dimension in the direction of the applied field • Villari Effect • Change in magnetization due to applied stress STRICTLY PRIVATE AND CONFIDENTIAL
Stress-magnetisation in carbon steel 2003 Jiles, Li, IEEE Trans. Mag, 39, 3037 STRICTLY PRIVATE AND CONFIDENTIAL
Experimental Investigation ofStress-Magnetisation in Carbon Steel
Stress-Magnetisation in Carbon SteelExperimental Setup • 20 x 210 mm rectangular sample • #45 Carbon Steel • 3 axis fluxgate magnetometer • Cyclic force • 0-10-0 kN • 0-250-0 MPa STRICTLY PRIVATE AND CONFIDENTIAL
Stress-Magnetisation in Carbon SteelProcessed Experimental Results STRICTLY PRIVATE AND CONFIDENTIAL
FE Modelling of Magnetic Scalar Potential in Stressed Steel Bar
FE Modelling of Magnetic Scalar Potential in Stressed Steel Bar FEM of the Magnetic Scalar Potential of the Steel Bar Stressed to 120 MPa STRICTLY PRIVATE AND CONFIDENTIAL
Comparison betweenExperimental and FEM Results Experiment image of field compared to model calculated image STRICTLY PRIVATE AND CONFIDENTIAL
FEM of Cracked Steel Bar STRICTLY PRIVATE AND CONFIDENTIAL
Magnetic detection of Stress Concentration Zones (SCZ) Methodology - Wang et al Characteristic curves of Self Magnetic Flux Leakage (SMFL) SCZ Graphic adapted from: Wang, Z.D., et al., Quantitative study of metal magnetic memory signal versus local stress concentration. NDT & E International, 2010. 43(6): p. 513-518. STRICTLY PRIVATE AND CONFIDENTIAL
Magnetic detection of Stress Concentration Zones (SCZ)Instrumentation STRICTLY PRIVATE AND CONFIDENTIAL
Magnetic detection of Stress Concentration Zones (SCZ) Analysis of Field Data 48” diameter Gas Pipe at 40 bar ΔZ pk-pk length 6 m ΔX pk magnitude 3 μT ΔZ pk magnitude 12.5 μT ΔX pk length 6 m STRICTLY PRIVATE AND CONFIDENTIAL
Summary • Motivation for remote stress measurement • Stress Concentration Tomography (SCT) • Magnetoelastic effects in steel • Experimental measurement • Finite element modelling of stress • Finite element modelling of stress induced magnetic field • Experimental magnetic field characterisation rig • Prototype SCT instrumentation • Initial field survey results STRICTLY PRIVATE AND CONFIDENTIAL