V1.0; May 27, 200416th WCNDT, Aug 30 - Sep 3, 2004 Montreal 1 SIMULTANEOUS MEASUREMENT OF MATERIAL...
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Transcript of V1.0; May 27, 200416th WCNDT, Aug 30 - Sep 3, 2004 Montreal 1 SIMULTANEOUS MEASUREMENT OF MATERIAL...
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
1
SIMULTANEOUS MEASUREMENT OF MATERIAL PROPERTIES AND THICKNESS OF CARBON STEEL
PLATES USING PULSED EDDY CURRENTS
V.O. de Haan1 and P. de Jong2
1 BonPhysics Research and Investigations BV, Putterhoek, The Netherlands; 2 Röntgen Technische Dienst bv, Rotterdam, The Netherlands
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
2
Outline
• Introduction to RTD-INCOTEST©
• Principe of new method
• Measurements and results
• Discussion
• Conclusion
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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RTD-INCOTEST©
• Insulated COmponent TEST• Corrosion survey method • Ferrous objects covered with insulation, asbestos,
fire proofing, concrete or coating• INCOTEST is aimed at the detection of larger area
(not localised) corrosion• Pulsed eddy current technology
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Pulsed Eddy Currents
l
d
I
object
Transmitter coil
Receivercoil
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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0.001
0.01
0.1
1
10
100
0.01 0.1 1x
(x
)
1/3
-3 dB point
inverse power law t -1.5
exponential decay
Pulsed Eddy Currents / ,,)( 5.1 tΘlAtU
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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RTD-INCOTEST©
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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RTD-INCOTEST©
Typical applications
insulated vessels, storage tanks, piplines
riser/caisson (splash zone) inspection
rough corroded or coated surfaces
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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RTD-INCOTEST©
Advantages:
measurement at a distance
no cleaning needed
fast
Disadvantages:
reference needed
large footprint
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Principe of new method
= permeability
= conductivity
l = lift-off
d = thickness object
t = time
F = depends on geometry of probe
/ ,,,,)( 5.1 tΘtdlFtU
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Principe of new method
probe
tlA
tdlF
1
,,,,,,
2),( dlprobe 2 d
/ ,,,,)( 5.1 tΘtdlFtU
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Pulsed Eddy Currents tdlFtΘtU ,,,,/)( 5.1
0.001
0.01
0.1
1
10
100
0.01 0.1 1x
(x
)F
F < 1
F = 1
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Dimensions of probert2
rr2
rr1
rt1Transmitting coilnt turns
Receiving coilnr turns
lt1 lt2lr2lr1
Conducting plated
l1 / mm l2 / mm r1 / mm r2 / mm nTransmitter 2.15 7.05 5.25 7.70 400Receiver 2.15 7.05 7.70 10.25 1280
7.6 mm
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Measurement example
1E-6
1E-5
1E-4
1E-3
1E-2
0.001 0.01 0.1Time (s)
Ind
uct
ion
vol
tage
(V
) . 10-2
10-3
10-4
10-5
10-6
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Resultsobject
ms/mm2d
mmdfit
mmerror
%2
%
mm
D2 0.78 18.8712.976.87
19.813.57.5
6.43.8
21.0
0.80.70.2
5.04.49.3
0.90.60.6
A3 2.01 19.1213.237.09
21.114.19.6
9.94.64.9
0.70.81.1
10.56.2
36.0
2.00.82.6
A4 1.32 18.7713.156.99
18.915.010.4
47.016.0
9.8
2.41.60.3
0.914.148.4
0.21.93.4
D36 1.09 18.5312.766.85
20.313.07.5
4.04.18.5
0.20.91.4
9.62.29.5
1.80.30.7
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Discussion
• Only for the smallest thickness a deviation occurs larger than 2 mm. With the old model and a (not) favorable reference measurement the relative deviation would be at least (60) 30 %.
• As 2 varies around 1 the fit error is not determined by systematic differences but by the accuracy of the measurements.
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Discussion
• 1% of the signal is generated by eddy currents at a distance larger than 7 cm from the center of the coils. The plates dimensions were 16.5 by 16.5 cm, hence the footprint was a little larger than the object.
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Discussion
• The smaller the wall thickness of the object, the less accurate the fitted wall thickness. This is due to the special form of function F and is a limitation of the method.
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Conclusions
1 Simultaneous fit of two time constants from the signal measured by RTD-INCOTEST© pulsed eddy current method facilitates the determination of both material properties () and absolute thickness of an object.
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Conclusions
2 Measurements show that accurate geometry is very important. The object must be larger than the (effective) footprint and the distance between probe and object must be accurately known or measured.
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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Conclusions
3 Accuracy of 10% is possible and can be reduced by enhancement of probe design and measurement accuracy. Further research is needed to increase the accuracy of the method.
V1.0; May 27, 2004 16th WCNDT, Aug 30 - Sep 3, 2004 Montreal
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SIMULTANEOUS MEASUREMENT OF MATERIAL PROPERTIES AND THICKNESS OF CARBON STEEL
PLATES USING PULSED EDDY CURRENTS
Thank you for your attention