Transcript Remote Measurement of Stress in Carbon Steel

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
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School of Electronic and Electrical Engineering,
School of Physics and Astronomy,
University of Leeds, UK
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.
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
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Motivation
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Ageing global pipeline infrastructure
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Non-invasive, remote, pipeline integrity assessment
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Non-interruption of pipeline service
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Applicable to non-piggable pipelines
No change to operating parameters
Detection of stress not geometry
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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
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Stress Concentration
Tomography (SCT)
• Pipeline experiences stress
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Corrosion Anomaly
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Stress Corrosion and Metallurgical Defects
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Slippage
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Subsidence
Pipeline
Anomaly
Localised Stress
Concentration
Magnetostriction
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Changes in
magnetic field
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Stress Concentration
Tomography (SCT)
Length of
anomaly 1
Length of
Anomaly 2
Length of
anomaly 3
Magnetic field
Pipeline
Defective section
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Defective section
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Defective section
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Theory
SCT
Simulation
Field Trials
Instrumentation
& Analysis
Experimental
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Magnetoelastic effects
Joule Magnetostriction
Change in sample dimension in the direction of the applied field
Villari Effect
Change in magnetization due to applied stress
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Stress-magnetisation in carbon steel
2003 Jiles, Li, IEEE Trans. Mag, 39, 3037
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Experimental Investigation of
Stress-Magnetisation in Carbon Steel
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Stress-Magnetisation in Carbon Steel
Experimental Setup
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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]
0.42 0.50
0.170.37
0.500.80
<0.25
<0.25
<0.035
570
Yield
Point
[N/mm]
295
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Stress-Magnetisation in Carbon Steel
Processed Experimental Results
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FE Modelling of Magnetic Scalar
Potential in Stressed Steel Bar
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FE Modelling of Magnetic Scalar
Potential in Stressed Steel Bar
FEM of the Magnetic Scalar Potential of the Steel Bar Stressed to 120 MPa
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Comparison between
Experimental and FEM Results
Experiment image of field compared to model calculated image
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FEM of Cracked Steel Bar
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Magnetic detection of
Stress Concentration Zones (SCZ)
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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.
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Magnetic detection of Stress Concentration Zones (SCZ)
Instrumentation
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Magnetic detection of Stress Concentration Zones (SCZ)
Analysis of Field Data
48” diameter Gas Pipe at 40 bar
ΔZ pk-pk length
6m
ΔX pk magnitude
3 μT
ΔZ pk magnitude
12.5 μT
ΔX pk length
6m
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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
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Thank you for your attention
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