Understanding Magnetic Flux Leakage Testing Reading 1

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Probe Type In many cases the thickness of material being examined is less than 10mm and the scanning surfaces are not completely smooth. This means that the initial pulse of single crystal transducers will occupy a significant portion of the nominal thickness so these transducers are not suitable. Twin crystal (Dual) transducers overcome this problem but it must be remembered that the optimum distance at which the maximum amount of transmitted energy is able to be captured by the receiver is a function of the probe design. Figure 13 illustrates this and shows clearly why reflectors below this distance will give reduced amplitude signals even when the reflecting surface in question is flat and parallel to the scanning surface. The operator should be aware of this possibility especially as corrosion pits are not ideal reflectors and should be prepared to vary the gain when backwall echoes are 'lost'. The rough surfaces encountered will rapidly wear Perspex shoes and change the beam angle so it is necessary to fit a wear ring to the probe. The crystal size should be between 10 and 15 mm diameter. Charlie Chong/ Fion Zhang
Couplant method and type Two methods of coupling ultrasound to the material are in current use. For manual scanning the contact method is used, whilst for automated and semiautomated scanning, water irrigation is preferred. In either case it is essential that the couplant is able to 'wet' the surface. Suitable gels are available for manual scanning and for water irrigation it may be necessary to add a wetting agent (soap). Scanning technique It should be obvious that taking spot readings on a grid pattern is only suitable for detecting areas of general corrosion and is useless in detecting isolated pits. Therefore it is necessary to use an area scan technique with a suitable overlap to ensure coverage by the effective area of the probe. With manual scanning it is better to use a fairly rapid probe movement with suitable calibration than to use a slow painstaking approach to the detection phase. This is because the human eye naturally responds to a sudden change (movement) in signal pattern. Once the pit has been detected, a more careful investigation of pit depth can be carried out. 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
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
Page 65 and 66: Fig 2: Adjustable MFL pipe scanner
Page 67 and 68: For inspection of bare or painted p
Page 69 and 70: MFL method Charlie Chong/ Fion Zhan
Page 71 and 72: A magnet within a yoke construction
Page 73 and 74: 5. Principle of "improved" MFL (SLO
Page 75 and 76: Figure 4: shows the relative sensit
Page 77 and 78: The technical thickness limit of th
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Page 81 and 82: INTRODUCTION Magnetic Flux Leakage
Page 83 and 84: Figures 5 to 8 are photographs of e
Page 85 and 86: METHOD PRINCIPLES MFL: The principl
Page 87 and 88: PROBABILITY OF DETECTION - MFL. The
Page 89 and 90: ■ Sensor type and layout Two type
Page 91 and 92: ■ Speed control Some degree of sp
Page 93 and 94: ■ Defect notification There are t
Page 95 and 96: ■ Scanning surface condition The
Page 97 and 98: ■ Scanning surface coating One ma
Page 99 and 100: 60%, 40%, 50%, Charlie Chong/ Fion
Page 101 and 102: ■ Human factors As with other NDT
Page 103 and 104: PROBABILITY OF DETECTION - ULTRASON
Page 105: Flaw detector As a minimum it shoul
Page 109 and 110: Floor Parameters Thickness Thinner
Page 111 and 112: Charlie Chong/ Fion Zhang
Page 113 and 114: Pit characteristics The easiest pit
Page 115 and 116: POD Summary for Ultrasonics On good
Page 119 and 120: Figures 17 to 21 are photographs of
Page 125 and 126: The Truth About Magnetic Flux Leaka
Page 127 and 128: MAGNETIC FLUX LEAKAGE (MFL) In orde
Page 129 and 130: THE MFL INSPECTION ENVIRONMENT In o
Page 131 and 132: ■ STORAGE TANK SURFACE CONDITION
Page 133 and 134: ■ SENSOR TYPES MFL tools typicall
Page 135 and 136: MFL TECHNIQUE APPLICATION CONSIDERA
Page 137 and 138: ■ QUANTITATIVE ASSESSMENT OF INDI
Page 139 and 140: ■ THE SINGLE LEVEL THRESHOLD Comm
Page 143 and 144: Abstract— Magnetic non-destructiv
Page 145 and 146: History The effect was originally d
Page 147 and 148: I. INTRODUCTION Accidents due to de
Page 149 and 150: In this study, we developed the MFL
Page 151 and 152: Figure 1. Resistance of the TMR dev
Page 153 and 154: Faraday Law E(emf) = - N ∆(BA)/
Page 155 and 156: 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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End Of Reading 5 Charlie Chong/ Fio
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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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