V1.0; May 27, th 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 Haan 1 and P. de Jong 2 1 BonPhysics Research and Investigations BV, Putterhoek, The Netherlands; 2 Röntgen Technische Dienst bv, Rotterdam, The Netherlands

V1.0; May 27, th 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, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 3 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, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 4 Pulsed Eddy Currents

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 5 Pulsed Eddy Currents

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 6 RTD-INCOTEST ©

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 7 RTD-INCOTEST © Typical applications insulated vessels, storage tanks, piplines riser/caisson (splash zone) inspection rough corroded or coated surfaces

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 8 RTD-INCOTEST © Advantages: measurement at a distance no cleaning needed fast Disadvantages: reference needed large footprint

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 9 Principe of new method  = permeability  = conductivity l = lift-off d = thickness object t = time F = depends on geometry of probe

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 10 Principe of new method

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 11 Pulsed Eddy Currents

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 12 Dimensions of probe  7.6 mm

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 13 Measurement example

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 14 Results

V1.0; May 27, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 15 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, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 16 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, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 17 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, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 18 Conclusions 1Simultaneous 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, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 19 Conclusions 2Measurements 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, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 20 Conclusions 3Accuracy 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, th WCNDT, Aug 30 - Sep 3, 2004 Montreal 21 SIMULTANEOUS MEASUREMENT OF MATERIAL PROPERTIES AND THICKNESS OF CARBON STEEL PLATES USING PULSED EDDY CURRENTS Thank you for your attention