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8/6/2019 Development of Automated Electromagnetic Techniques for Inspecting Inner
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Development of Automated
Electromagnetic Techniques forInspecting Inner Cracks of LPG Tanks
Yung-How Wu,
Feng-Ju Hsieh, Mu-Chung Peng, Hsing-Jeng Yang
Materials Research Laboratories, Taiwan
Email:[email protected]
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Objective
To integrate an automated
ElectroMagnetic Array based systemfor inspecting inner surface crackson LPG Tank.
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Background
LPG tanks were frequently subjected to SCC oninner surface during service and must beinspected from inside regularly.
Conventional ISI by MT or PT is toilsome andcostly.
Extremely hot in summer
Scaffolding & Coating removal ACFM has been used to detect surface breaking
cracks without removing coating on components.
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Electromagnetic Array
Techniques
ACPD EMA or ACFM
V2/V1 = (2d + ) / d =/2((V2/V1) 1)
V1
Span =
V2
dSurface
current Surface crack
Currentperturbation
Surface current
Crack tip
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Crack Detection and Sizing
EMA System Data Display
SDDPUSolo
Probe for AutomationHandheld Probe
Crack
CP Abs Corr.Display
Abs CP
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Samples with Artificial Cracks
Notches Cracks41210
150
Plate-1
A group
B groupC group
Defect(mm)
Block TypeDepth
Lengt
h
Positn
Weld-6 Toe Crack ~2mm 12 30
Weld-9 CenterlineCrack ~2mm 13 380.25102
0.25202
0.25402
Notch/A
WidthLengthDepthType/Positn
Defect(mm)
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Characteristic Defect Signals
A single defect was detected by three successive channels.
Defect could be clearly identified by various displays.
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Signals in Various Conditions
1_Plate1_Plate2
0
1
2
3
4
5
6
0 1 2 3 4 5 6 7
(mm)
(mm)
Weakest response at 380
Amplitude decreased exponentially
with Lift-Off
Measuring error could be
controlled down to 25%
0
2
4
68
0 20 38 50 90
o
1
5
15
10mmx1mm
0
5
10
0 10 20 30
(Max/Min)
1
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Automated Inspection System EMA System
Lizard solo 64 channels SDDPU
Scanner Control Console PC + TFT monitor
Motor control module Motion control &
monitoring package
CCD camera and 2-axis
stage Scanner
With 4 magnetic rollers
Carrying 32-channel
probe
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Automated Inspection Method Weld and Plate regions were
Inspected individually Weld: along the weldment
Plate: as shown
Scanner was moved to the top
position and then scan
automatically on each path.
Scanning route was
monitored by CCD cameraand full coverage was assured.
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Field Trials
Scanning is controlled andmonitored through CCD cameraby inspector operating below theLPG tank.
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Inspection Process
Scan a Line
Yes
No
CCD Camera
or
EMA
EMA
EMA
Control Console
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Conclusions
Laboratory and preliminary field trials provedthe method satisfactory in detecting real
cracks down to 10mm in length and 1mm in
depth in both regions. However, minor
improvement on the scanner manipulation is
required before practical application.