Understanding Magnetic Flux Leakage Testing Reading 1

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Reading I Content • Reading One: E1571 (Revisiting) • Reading Two: Magnetic Flux and SLOFEC Inspection of Thick Walled Components (Revisited) • Reading Three: • Reading Four: Charlie Chong/ Fion Zhang
Principle of MFL Testing MFL testing is a magnetic based NDT method. The method is used to detect corrosion and cracks in ferromagnetic materials, such as pipelines, storage tanks, ropes and cables [10,27–29]. The basic principle of MFL testing is that the flux lines pass through the steel wires when a magnetic field is applied to the cable. At areas where corrosion or missing metal exists, the magneticfield leaks from the wires. In an MFL tool, magnetic sensors are placed between the poles of the magnet to detect the leakage field. The signal of the leakage field is analyzed to identify the damaged areas and estimate the amount of metal loss. Thus, the transducer includes magnetizers and magnetic sensors. The magnetic-field can be produced by a permanent magnet yoke, or a solenoid with the direct current. The magnetic-field density needs to meet near saturation under the sensor. Figure 3 shows the principle of MFL testing. The permanent magnet yoke is used to produce the magnetic-field, and the coil is used to induce (detect?) the leakage field. Charlie Chong/ Fion Zhang
Page 1 and 2: Understanding Magnetic Flux Leakage
Page 3 and 4: Offshore Pipeline MFLT Charlie Chon
Page 5 and 6: Offshore Pipeline MFLT Charlie Chon
Page 7 and 8: Cross Country Pipeline MFLT Charlie
Page 9 and 10: Tank Bottom MFLT Charlie Chong/ Fio
Page 11 and 12: Tank Bottom MFLT Charlie Chong/ Fio
Page 13: Drilling String MFLT Charlie Chong/
Page 17 and 18: Reading 1 E1571 Standard Practice f
Page 19 and 20: 2. Referenced Documents 2.1 ASTM St
Page 21 and 22: 3.2.4 single-function instrument—
Page 23 and 24: Keywords: • AC- Alternating Curre
Page 25 and 26: Alternating Field MFL method Charli
Page 27 and 28: FIG. 1 Schematic Representation of
Page 33 and 34: 4.2 The examination is conducted us
Page 35 and 36: 6. Basis of Application 6.1 The fol
Page 37 and 38: FIG. 5 Example of a Wire Rope Refer
Page 39 and 40: 7. Limitations 7.1 General Limitati
Page 41 and 42: 7.3 Limitations Inherent in the Use
Page 43 and 44: 8.1.4 The instrument should have co
Page 45 and 46: 9.2.4 The wire rope must be examine
Page 47 and 48: 9.2.6 To assure repeatability of th
Page 49 and 50: 9.2.9 If the NDT indicates existenc
Page 51 and 52: 10.2 Wire Rope Reference Standard:
Page 53 and 54: 10.3 Rod Reference Standard: 10.3.1
Page 55 and 56: 11. Test Agency Qualification 11.1
Page 57 and 58: Reading 2 Magnetic Flux and SLOFEC
Page 59 and 60: 1. Introduction NDT is an essential
Page 61 and 62: 2. Progress in NDT capabilities The
Page 63 and 64: 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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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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