Understanding Magnetic Flux Leakage Testing Reading 1

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9.4.3.4 Liftoff Control of Scanning Head To obtain a stable detection of discontinuities, liftoff between the probe and the surface of the material must be kept constant. Usually liftoff is kept constant by contact of the probe with the surface but the probe tends to wear with this technique. A magnetic floating technique has been used for noncontact scanning. In this technique, liftoff is measured by a gap probe and the probe holder is moved by a voice coil motor, controlled by the gap signal. This system and related technology are described in this volume’s chapter on primary metals applications. Charlie Chong/ Fion Zhang
9.4.4 Particular Applications 9.4.4.1 Wire Ropes An interesting example of an elongated steel product inspected by magnetic flux leakage testing is wire rope. Such ropes are used in the construction, marine and oil production industries, in mining applications and elevators for personnel and raw material transportation. <strong>Testing</strong> is performed to determine cross sectional loss caused by corrosion and wear and to detect internal and external broken wires. The type of flux loop used (electromagnet or permanent magnet) can depend on the accessibility of the rope. Permanent magnets might be used where taking power to an electromagnet might cause logistic or safety problems. By making suitable estimates of the parameters involved, a reasonably good estimate of the flux in the rope can be made. Because discontinuities can occur deep inside the rope material, it is essential to maintain the rope at a high value of magnetic flux density, 1.6 to 1.8 T (16 to 18 kG). Under these conditions, breaks in the inner regions of the rope will produce magnetic flux leakage at the surface of the rope. 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
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Keywords: • Excitation systems.
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FIGURE 1. Electromagnetic yoke for
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Reluctance. Magnetic reluctance, or
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L, Henry - H, The inductance of an
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Weber (Magnetic Flux Ф) In physics
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Electrical Inductance - Henry The h
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More Reading on: Magnetic field A m
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The weber The weber may be defined
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History: Although magnets and magne
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Three discoveries challenged this f
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Between 1861 and 1865, James Clerk
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Lorentz Force Law Both the electric
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From the force relationship above i
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Alternative names for B • Magneti
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Charlie Chong/ Fion Zhang http://ww
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Reluctance S is the sum of the relu
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Reluctance S Reluctance, S = Length
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9.2.1 Magnetizing Coil A commonly u
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Introduction of the test object int
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9.2.1.2 Testing in Residual Field T
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FIGURE 3. Circumferential magnetiza
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FIGURE 5. Simple technique for circ
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Typical configurations shown in Fig
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FIGURE 6. Capacitor discharge confi
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A good rule is that, if H(r) in Eq.
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9.2.4 Optimal Operating Point Consi
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At higher and higher values of appl
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9.3 PART 3. Magnetic Flux Leakage T
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Magnetic Flux Leakage fields. Charl
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BS EN 10246-5:2000 MFLT Set-up 1: T
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MFLT- Expert at Work Charlie Chong/
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MFLT- Expert at Works Charlie Chong
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The most commonly used in-service i
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Magnetic Flux Leakage fields. Charl
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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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Page 299 and 300: 9.3.3.1 Finite Element Techniques A
Page 301 and 302: The solutions of classical problems
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Page 305 and 306: Other Reading: Leakage signals due
Page 307 and 308: Design considerations for magnetiza
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Page 317 and 318: Relatively Flat Surfaces Charlie Ch
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Page 323 and 324: Ampere's Law The magnetic field in
Page 325 and 326: 9.4.3.2 Transverse Discontinuities
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Page 339 and 340: 9.4.4.6 Billets A relatively common
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Page 343 and 344: 9.5.1 Introduction The magnetic flu
Page 345 and 346: An earlier study of samples magneti
Page 347 and 348: 9.5.2 EXPERIMENTAL Three simulated
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Page 351 and 352: Fig. 3. Outline of pipeline sample
Page 353 and 354: After the three magnetization cycle
Page 355 and 356: Fig. 4. Contour map of radial activ
Page 357 and 358: Keywords: ■ Contour map scan ■
Page 359 and 360: Fig. 6. Contour map of radial resid
Page 361 and 362: Compare the magnetic flux density o
Page 363 and 364: Fig. 8. Contour map of radial resid
Page 365 and 366: Active and residual flux distributi
Page 367 and 368: Fig. 10. Probable flux distribution
Page 369 and 370: One of the interesting features of
Page 371 and 372: Fig. 11. Active (a) and residual (b
Page 373 and 374: Irregular gouge The active and resi
Page 375 and 376: Fig. 12. Active (a) and residual (b
Page 377 and 378: The main interest was to determine
Page 379 and 380: 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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