Understanding Magnetic Flux Leakage Testing Reading 1

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In 1750, John Michell stated that magnetic poles attract and repel in accordance with an inverse square law. Charles-Augustin de Coulomb experimentally verified this in 1785 and stated explicitly that the north and south poles cannot be separated (dipoles) . Building on this force between poles, Siméon Denis Poisson (1781–1840) created the first successful model of the magnetic field, which he presented in 1824. In this model, a magnetic H-field is produced by 'magnetic poles' and magnetism is due to small pairs of north/south magnetic poles. Comment: H-field – magnetic field intensity? Relates to A∙m -1 Charlie Chong/ Fion Zhang http://en.wikipedia.org/wiki/<strong>Magnetic</strong>_field
Three discoveries challenged this foundation of magnetism, though. First, in 1819, Hans Christian Oersted discovered that an electric current generates a magnetic field encircling it. Then in1820, André-Marie Ampère showed that parallel wires having currents in the same direction attract one another. Finally, Jean-Baptiste Biot and Félix Savart discovered the Biot- Savart law in 1820, which correctly predicts the magnetic field around any current- carrying wire. Extending these experiments, Ampère published his own successful model of magnetism in 1825. In it, he showed the equivalence of electrical currents to magnets and proposed that magnetism is due to perpetually flowing loops of current instead of the dipoles of magnetic charge in Poisson's model. This has the additional benefit of explaining why magnetic charge can not be isolated. Further, Ampère derived both Ampère's force law describing the force between two currents and Ampère's law, which, like the Biot–Savart law, correctly described the magnetic field generated by a steady current. Also in this work, Ampère introduced the term electrodynamics to describe the relationship between electricity and magnetism. Charlie Chong/ Fion Zhang http://en.wikipedia.org/wiki/<strong>Magnetic</strong>_field
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Understanding Magnetic Flux Leakage
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Offshore Pipeline MFLT Charlie Chon
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Offshore Pipeline MFLT Charlie Chon
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Cross Country Pipeline MFLT Charlie
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Tank Bottom MFLT Charlie Chong/ Fio
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Tank Bottom MFLT Charlie Chong/ Fio
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Drilling String MFLT Charlie Chong/
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Principle of MFL Testing MFL testin
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Reading 1 E1571 Standard Practice f
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2. Referenced Documents 2.1 ASTM St
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3.2.4 single-function instrument—
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Keywords: • AC- Alternating Curre
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Alternating Field MFL method Charli
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FIG. 1 Schematic Representation of
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4.2 The examination is conducted us
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6. Basis of Application 6.1 The fol
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FIG. 5 Example of a Wire Rope Refer
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7. Limitations 7.1 General Limitati
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7.3 Limitations Inherent in the Use
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8.1.4 The instrument should have co
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9.2.4 The wire rope must be examine
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9.2.6 To assure repeatability of th
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9.2.9 If the NDT indicates existenc
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10.2 Wire Rope Reference Standard:
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10.3 Rod Reference Standard: 10.3.1
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11. Test Agency Qualification 11.1
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Reading 2 Magnetic Flux and SLOFEC
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1. Introduction NDT is an essential
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2. Progress in NDT capabilities The
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3. Traditional MFL Inspection syste
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Fig 2: Adjustable MFL pipe scanner
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For inspection of bare or painted p
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MFL method Charlie Chong/ Fion Zhan
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A magnet within a yoke construction
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5. Principle of "improved" MFL (SLO
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Figure 4: shows the relative sensit
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The technical thickness limit of th
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End Of Reading 2 Charlie Chong/ Fio
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INTRODUCTION Magnetic Flux Leakage
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Figures 5 to 8 are photographs of e
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METHOD PRINCIPLES MFL: The principl
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PROBABILITY OF DETECTION - MFL. The
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■ Sensor type and layout Two type
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■ Speed control Some degree of sp
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■ Defect notification There are t
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■ Scanning surface condition The
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■ Scanning surface coating One ma
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60%, 40%, 50%, Charlie Chong/ Fion
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■ Human factors As with other NDT
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PROBABILITY OF DETECTION - ULTRASON
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Flaw detector As a minimum it shoul
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Couplant method and type Two method
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Floor Parameters Thickness Thinner
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Charlie Chong/ Fion Zhang
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Pit characteristics The easiest pit
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POD Summary for Ultrasonics On good
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Figures 17 to 21 are photographs of
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The Truth About Magnetic Flux Leaka
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MAGNETIC FLUX LEAKAGE (MFL) In orde
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THE MFL INSPECTION ENVIRONMENT In o
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■ STORAGE TANK SURFACE CONDITION
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■ SENSOR TYPES MFL tools typicall
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MFL TECHNIQUE APPLICATION CONSIDERA
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■ QUANTITATIVE ASSESSMENT OF INDI
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■ THE SINGLE LEVEL THRESHOLD Comm
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Abstract— Magnetic non-destructiv
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History The effect was originally d
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I. INTRODUCTION Accidents due to de
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In this study, we developed the MFL
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Figure 1. Resistance of the TMR dev
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Faraday Law E(emf) = - N ∆(BA)/
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Page 161 and 162: Figure 5. Magnetic images with 10 H
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Page 165 and 166: IV. RESULTS AND DISCUSSION First, w
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Page 175 and 176: 9.1 PART 1. Introduction to Magneti
Page 177 and 178: 9.1.1.2 Receiving Testing The end u
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Page 185 and 186: Steel Mill Charlie Chong/ Fion Zhan
Page 187 and 188: Seams & Laps Charlie Chong/ Fion Zh
Page 189 and 190: Keywords: • Excitation systems.
Page 191 and 192: FIGURE 1. Electromagnetic yoke for
Page 193 and 194: Reluctance. Magnetic reluctance, or
Page 195 and 196: L, Henry - H, The inductance of an
Page 197 and 198: Weber (Magnetic Flux Ф) In physics
Page 199 and 200: Electrical Inductance - Henry The h
Page 201 and 202: More Reading on: Magnetic field A m
Page 203 and 204: The weber The weber may be defined
Page 205: History: Although magnets and magne
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Page 211 and 212: Lorentz Force Law Both the electric
Page 213 and 214: From the force relationship above i
Page 215 and 216: Alternative names for B • Magneti
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Page 219 and 220: Reluctance S is the sum of the relu
Page 221 and 222: Reluctance S Reluctance, S = Length
Page 223 and 224: 9.2.1 Magnetizing Coil A commonly u
Page 225 and 226: Introduction of the test object int
Page 227 and 228: 9.2.1.2 Testing in Residual Field T
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Page 233 and 234: Typical configurations shown in Fig
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Page 245 and 246: Magnetic Flux Leakage fields. Charl
Page 247 and 248: BS EN 10246-5:2000 MFLT Set-up 1: T
Page 249 and 250: MFLT- Expert at Work Charlie Chong/
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Intelligence Piggy Charlie Chong/ F
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This induction direction makes it p
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It must be mentioned that only the
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This equation indicates that the ou
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FIGURE 9. Pickup coil and signal in
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Magnetic Flux Leakage & Signals Cha
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Magnetic Flux Leakage & Signals Cha
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Magnetodiodes Charlie Chong/ Fion Z
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Hall Effect Detectors Charlie Chong
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9.3.1.4 Giant Magnetoresistive Prob
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FIGURE 10. Resistance versus applie
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However, there are some disadvantag
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Giant Magnetoresistive or GMR senso
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Okay so the AMR and GMR sensors see
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9.3.2 Magnetic Particles Magnetic p
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(B) Wet Testing. Wet techniques are
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9.3.2.2 Imaging of Magnetic Particl
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FIGURE 11. Flying spot scanner for
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In practice, charge coupled device
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CCD Charlie Chong/ Fion Zhang
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CCD Charlie Chong/ Fion Zhang http:
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9.3.3.1 Finite Element Techniques A
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The solutions of classical problems
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FEA Model Charlie Chong/ Fion Zhang
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Other Reading: Leakage signals due
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Design considerations for magnetiza
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9.4.1 Test Object Configurations 9.
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Elongated Objects- Pump Jack Charli
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Threaded Regions of Sucker Rod Char
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9.4.1.4 Ball Bearings and Races Sys
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Relatively Flat Surfaces Charlie Ch
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In the metal processing industries,
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9.4.3 Typical Magnetic Flux Leakage
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Ampere's Law The magnetic field in
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9.4.3.2 Transverse Discontinuities
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The effective permeability of the m
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1. Where there is a direct current
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9.4.4 Particular Applications 9.4.4
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9.4.4.2 Internal Casing or Pipeline
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Production and transmission compani
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Cannon Tubes Charlie Chong/ Fion Zh
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9.4.4.6 Billets A relatively common
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As with many forms of nondestructiv
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9.5.1 Introduction The magnetic flu
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An earlier study of samples magneti
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9.5.2 EXPERIMENTAL Three simulated
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Fig. 2. Camera picture of a gouge o
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Fig. 3. Outline of pipeline sample
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After the three magnetization cycle
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Fig. 4. Contour map of radial activ
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Keywords: ■ Contour map scan ■
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Fig. 6. Contour map of radial resid
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Compare the magnetic flux density o
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Fig. 8. Contour map of radial resid
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Active and residual flux distributi
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Fig. 10. Probable flux distribution
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One of the interesting features of
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Fig. 11. Active (a) and residual (b
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Irregular gouge The active and resi
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Fig. 12. Active (a) and residual (b
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The main interest was to determine
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Fig. 13. Residual MFL scans of circ
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9.5.4 CONCLUSIONS The residual MFL
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Peach - 我爱桃子 Charlie Cho
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Good Luck Charlie Chong/ Fion Zhang
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