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 1 School of Electronic and Electrical Engineering, 2 School of Physics and Astronomy, University of Leeds, UK 3 Speir 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.

STRICTLY PRIVATE AND CONFIDENTIAL 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

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 Concentration Tomography (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 Concentration Tomography (SCT) Pipeline experiences stress Corrosion Anomaly Stress Corrosion and Metallurgical Defects Slippage Subsidence Pipeline Anomaly Localised Stress Concentration Magnetostriction Changes in magnetic field Stress corrosion: cracks, laps, porosity, weld inclusions STRICTLY PRIVATE AND CONFIDENTIAL

Stress Concentration Tomography (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

STRICTLY PRIVATE AND CONFIDENTIAL SCT Instrumentation & Analysis Theory Simulation Experimental Field Trials Star diagram of research program Theory Experimental Simulation Field trials All feeding into instrumentation and processing technique 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 of Stress-Magnetisation in Carbon Steel

Stress-Magnetisation in Carbon Steel Experimental Setup 20 x 210 mm rectangular sample #45 Carbon Steel 3 axis fluxgate magnetometer Cyclic force 0-10-0 kN 0-250-0 MPa Physical Composition [%wt] Mechanical Properties C Si Mn Cr Ni Others Tensile Strength [N/mm] Yield Point [N/mm] 0.42 - 0.50 0.17- 0.37 0.50- 0.80 <0.25 <0.035 570 295 STRICTLY PRIVATE AND CONFIDENTIAL

Stress-Magnetisation in Carbon Steel Processed 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 between Experimental 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)

STRICTLY PRIVATE AND CONFIDENTIAL Magnetic detection of Stress Concentration Zones (SCZ) Methodology - Wang et al SCZ   Characteristic curves of Self Magnetic Flux Leakage (SMFL) 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

STRICTLY PRIVATE AND CONFIDENTIAL Magnetic detection of Stress Concentration Zones (SCZ) Analysis of Field Data 48” diameter Gas Pipe at 40 bar ΔX pk magnitude 3 μT ΔX pk length 6 m ΔZ pk-pk length 6 m ΔZ pk magnitude 12.5 μT STRICTLY PRIVATE AND CONFIDENTIAL

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

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