Understanding Magnetic Flux Leakage Testing Reading 1

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FIGURE 7. Effects of induction on magnetic flux lines at discontinuity: (a) no surface flux leakage occurs where magnetic flux lines are compressed at low levels of induction around discontinuity; (b) lack of compression at high magnetization results in surface magnetic flux leakage. Charlie Chong/ Fion Zhang
At higher and higher values of applied field, the permeability falls. It is, however, still large compared to the permeability of air, so the reluctance of the path through the discontinuity is still larger than through the metal. As a result, magnetic flux leakage at the outside surface helps provide a sufficiently high flux density in the material for the leakage of magnetic flux from discontinuities (Fig. 7b) while partially suppressing long range surface noise. For residual field testing, it is best to ensure that the material is saturated. The magnetic field starts to decay as soon as the energizing current is removed. Charlie Chong/ Fion Zhang
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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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The signal from the lock-in amplifi
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Figure 4. Measuring points for back
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Figure 7 shows the power spectrum o
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Figure 5. Magnetic images with 10 H
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Figure 6. Magnetic images with 5 Hz
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IV. RESULTS AND DISCUSSION First, w
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Figure8. Magnetic images of pits wi
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Figure 10. Example of the extracted
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Figure 12. Relationship of the defe
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9.1 PART 1. Introduction to Magneti
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9.1.1.2 Receiving Testing The end u
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5. Forging laps occur when gouges o
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For used materials, fatigue crackin
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Steel Mill - Expert at Works Charli
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Steel Mill Charlie Chong/ Fion Zhan
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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 and 206: History: Although magnets and magne
Page 207 and 208: Three discoveries challenged this f
Page 209 and 210: Between 1861 and 1865, James Clerk
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
Page 217 and 218: Charlie Chong/ Fion Zhang http://ww
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
Page 229 and 230: FIGURE 3. Circumferential magnetiza
Page 231 and 232: FIGURE 5. Simple technique for circ
Page 233 and 234: Typical configurations shown in Fig
Page 235 and 236: FIGURE 6. Capacitor discharge confi
Page 237 and 238: A good rule is that, if H(r) in Eq.
Page 239: 9.2.4 Optimal Operating Point Consi
Page 243 and 244: 9.3 PART 3. Magnetic Flux Leakage T
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/
Page 251 and 252: MFLT- Expert at Works Charlie Chong
Page 253 and 254: The most commonly used in-service i
Page 255 and 256: Magnetic Flux Leakage fields. Charl
Page 257 and 258: Intelligence Piggy Charlie Chong/ F
Page 259 and 260: This induction direction makes it p
Page 261 and 262: It must be mentioned that only the
Page 263 and 264: This equation indicates that the ou
Page 265 and 266: FIGURE 9. Pickup coil and signal in
Page 267 and 268: Magnetic Flux Leakage & Signals Cha
Page 269 and 270: Magnetic Flux Leakage & Signals Cha
Page 271 and 272: Magnetodiodes Charlie Chong/ Fion Z
Page 273 and 274: Hall Effect Detectors Charlie Chong
Page 275 and 276: 9.3.1.4 Giant Magnetoresistive Prob
Page 277 and 278: FIGURE 10. Resistance versus applie
Page 279 and 280: However, there are some disadvantag
Page 281 and 282: Giant Magnetoresistive or GMR senso
Page 283 and 284: Okay so the AMR and GMR sensors see
Page 285 and 286: 9.3.2 Magnetic Particles Magnetic p
Page 287 and 288: (B) Wet Testing. Wet techniques are
Page 289 and 290: 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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