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Remote-field eddy current signal analysis in small-bore ferromagnetic tubes
N DT Abstracts 52752
Mensching,
L.; Stegemann,
D.
52259
Sakamoto, T.; Fujiwara,
H.; Arita,
Y.
Internal pipe testing with eddy currents (In German, English abstract) Materialprufung, Vol. 35, No. 6. pp. 174-177 (Jun. 1993)
Eddy current examination using inner coil for ferromagnetic heat exchanger tubes (In Japanese, English abstract) Journal of JSNDI, Vol. 41, No. 12, pp. 685-693 (Dec. 1992)
Flaw size determination by separation of interfering signals in eddy testing inside tubes. New criteria and proceduresfor determining flaw sizes in tubes by suppressionof trouble signals are presented. This is highly valuable for the automation and improvement of tube testing. By four-dimensionalregressionanalysis of the resultsa high correlation of flaw size and evaluated parameters is found. The new procedure employs complex crosscorrelation of inspection signals with documentedsignals of
A new type of inner probe has been developed for ferromagnetic heat exchanger tube inspection. This probe contains special designed magnetic circuit using rare earth magnets to magnetize the tube sufficiently. This probe can detect the drilled hole of 0.8 mm in diameter, in the carbon steel tube (28 mm in outer diameter and 2 mm in wall thickness). Maintenance inspectionsof duplex stainless steel tubes were performed using this probe. The harmful corrosion in the tube was detected and evaluated by the defect signal characteristics such as the amplitude and the time width. The eddy current signal of D.C. magnetized tubes were also analyzed by the finite element method. It was revealed that the unique characteristics of signal phase angle were caused by the inhomogeneous permeability distributed around the defect.
current
reference flaws. Furthermore, inspection spectra including external tube structure interferences are improved by subtraction of stored signals from corresponding calibration samples.
52540 Becker, R.; Betzold, K.; Dobmann, G.; Holler, P. Progress in defect detection and characterization with multimulti- frequency-eddy-current and current perturbation testing
52254
Kirby,
M.W.; Lareau, J.P.
Eddy current imaging of aircraft using real time image signal processing
9th International Conference on Nondestructive Evaluation in the Nuclear Industry. Tokyo (Japan), 25-28 Apr. 1988, pp. 357-370. Edited by K. lida, J.E. Doherty and X. Edelmann. ASM (1988)
Proceedings of the International Conference on Nondestructive Testing and Evaluation of Composite Structures, Riga (Latvia), 22-24 Oct. 1991, Vol. 2, pp. 375-394. Riga (1991)
A new eddy current inspectiondevice designed especially for the defect testing of heat exchanger tubes in nuclear power plants is described. It improves the defect detection sensitivity and the signal interpretation in the critical part of the tube sheet with its expansion. The electric current perturbation method for the inspection on surface or near surface defects especially in austenitic componentsis considered.The interpretation of the measured signals is supported by computer results coming out from numerical models.
An eddy current system using portable precision scanners and signal analysis techniques developed in the nuclear industry has been applied to aircraft inspections. Using custom designed probes, multifrequency mixing, and digital signal processing, the detection criteria of 10% loss of wall on the interior faying surface and cracks 60 mils (1 .S mm) in length have been accomplished. Real time signal processing that requires a minimal amount of computation has been implemented in an eddy current imaging system. The signal processing produces spatial displays, in the C-scan format. of amplitude (in phase or quadrature) magnitude, phase of spatial derivatives of these parameters.
52537
Hoshikawa,
H.; Kayama,
K.; Kaida, J.; Ishibashi,
Y. 52251
Fundamental studies of remote field eddy-current inspection Conference on Nondestructive Evaluation in the Nuclear Industry, Tokyo (Japan), 25-28 Apr. 1988. pp. 339-344. Edited by K. lida, J.E. Doherty and X. Edelmann. ASM (1988)
Kawahe,
T.; Hasahara,
D.L.; Sullivan,
signal
analysis
S.P.
in small-bore (Apr. 1993)
A simple method for obtaining the depth of metal-loss defects in smallbore ferromagnetic tubes by using the remote-field eddy current method is described. Research and analysis were carried out using a probe equipped with a solenoidal detector coil coaxial with the pipe, scanning uniformdepth metal-loss defects shorter than the overall probe length. On a voltage plane polar plot, which is similar to the voltage plane used in conventional eddy current analysis, the variations in signal amplitude and phase caused by metal loss trace out an elongated loop known as a defect-signal trace. The length of the defect-signal trace indicates the cross-sectional area of metal loss. The experimental results are explained with reference to the skin-depth equation.
Y.
5 1735
Eddy current flaw detector
Moulder,
J.C.; Nakagawa,
N.
Characterizing the performance of eddy current probes using photoinductive field-mapping 00000673
British Patent No. 2,255,184 (28 Oct. 1992) A flaw detector for metal material which can check pipelines by means of the remote field eddy current method comprises an exciting coil EC fed with a.c., and a set of receiving coils RCl -RC9. The signal picked up in each receiving coil is filtered and passed via an a.g.c. circuit to a phase comparator which also receives a reference signal from the source. The
Research in Nondestructive Evaluation,
Vol. 4, No. 4, pp. 221-236
(I 992) We present a new method for characterizing current probes by mapping their electromagnetic
the performance of eddy tields. The technique is
based on the photoinductive effect. the change in the impedance of an eddy current probe induced by laser heating of the material under the probe. The instrument we developed maps a probe’s electric field distribution by scanning an infrared laser beam over a thil film of gold lying underneath the probe. Measuremenrs of both photoinductive signals and flaw signals for a series of similar probes demonstrate that the impedance change caused by an electrical-discharge-machined (EDM) notch or a fatigue crack is proportional to the strength of the photoinductive signal. Thus, photoinductive measurements can supplant the use of artifact standards to calibrate eddy current probes. To model commercial eddy current probes with ferrite cores, we developed a procedure to treat them as effective air-core probes. We obtained good agreement between the flaw signals calculated using this effective-coil approach and actual fatigue-crack signals measured with commercial probes. We also calculated probabilities of detection for target flaws in titanium alloys for a series of commercial probes.
comparator output is passed to a flaw detection signal generator. In an alternative embodiment, the receiving coil signals are processed in pairs, with phase adjustment of one signal of each pair. Thus stable phase detection can be obtained and precise diagnosis of the pipeline to be tested can be performed, without generation of spurious flaw indications. Further, by using an a.g.c. circuit to maintain the signal level provided by the receiving coils, S/N ratio of the flaw data can be improved.
523 I I
D.D.; Atherton,
Materials Evaluation, Vol. 5 I, No. 4. pp. 492-495,500
Remote field eddy current technique used for inspection of magnetic tubes has been studied through both experiment and finite element analysis. A defect in the remote field area causes significant change in the magnetic field around it inside the tube. External and internal defects in a magnetic tube can be detected from the tube’s inside with almost the same sensitivity. The phase rather than the amplitude of the defect signal is appropriate to detect defect depth. The amplitude of the defect signal decays as the test frequency becomes higher, while the phase becomes maximum at a certain frequency.
52316
Mackintosh,
Remote-field eddy current ferromagnetic tubes
9th International
Lund, F.P.
Eddy current flaw size detecting probe British Patent No. 2,256,7 I3 (16 Dec. 1992) The probe, for generating a signal indicative
of a quantitative of the size of a surface defect, comprises a magnetic field for inducing currents in the surface and a perturbation current sensor arrangement positioned relative to the field to give an output providing said quantitative measure. The probe comprises a solid cylindrical former on which is wound the perturbation current sensing coils which are rectangular or figure of eight shaped and have axes radial to the former. The tield generator coil has an axis aligned with the axis of the former and is constructed to produce a magnetic field which produces a spatially varied magnetic field in a material under test. measurement
51733
Delsarte,
G.; Levy, R.
MASCOTTE: analytical model of eddy current signals. (In French, English Abstract) Mermoires et Etudes Scientifiques Revue de Metallurgic, No. IO, pp. 653-658 (Oct. 1992)
176
Vol. 89,
Mensching,
L.; Stegemann,
D.
52259
Sakamoto, T.; Fujiwara,
H.; Arita,
Y.
Internal pipe testing with eddy currents (In German, English abstract) Materialprufung, Vol. 35, No. 6. pp. 174-177 (Jun. 1993)
Eddy current examination using inner coil for ferromagnetic heat exchanger tubes (In Japanese, English abstract) Journal of JSNDI, Vol. 41, No. 12, pp. 685-693 (Dec. 1992)
Flaw size determination by separation of interfering signals in eddy testing inside tubes. New criteria and proceduresfor determining flaw sizes in tubes by suppressionof trouble signals are presented. This is highly valuable for the automation and improvement of tube testing. By four-dimensionalregressionanalysis of the resultsa high correlation of flaw size and evaluated parameters is found. The new procedure employs complex crosscorrelation of inspection signals with documentedsignals of
A new type of inner probe has been developed for ferromagnetic heat exchanger tube inspection. This probe contains special designed magnetic circuit using rare earth magnets to magnetize the tube sufficiently. This probe can detect the drilled hole of 0.8 mm in diameter, in the carbon steel tube (28 mm in outer diameter and 2 mm in wall thickness). Maintenance inspectionsof duplex stainless steel tubes were performed using this probe. The harmful corrosion in the tube was detected and evaluated by the defect signal characteristics such as the amplitude and the time width. The eddy current signal of D.C. magnetized tubes were also analyzed by the finite element method. It was revealed that the unique characteristics of signal phase angle were caused by the inhomogeneous permeability distributed around the defect.
current
reference flaws. Furthermore, inspection spectra including external tube structure interferences are improved by subtraction of stored signals from corresponding calibration samples.
52540 Becker, R.; Betzold, K.; Dobmann, G.; Holler, P. Progress in defect detection and characterization with multimulti- frequency-eddy-current and current perturbation testing
52254
Kirby,
M.W.; Lareau, J.P.
Eddy current imaging of aircraft using real time image signal processing
9th International Conference on Nondestructive Evaluation in the Nuclear Industry. Tokyo (Japan), 25-28 Apr. 1988, pp. 357-370. Edited by K. lida, J.E. Doherty and X. Edelmann. ASM (1988)
Proceedings of the International Conference on Nondestructive Testing and Evaluation of Composite Structures, Riga (Latvia), 22-24 Oct. 1991, Vol. 2, pp. 375-394. Riga (1991)
A new eddy current inspectiondevice designed especially for the defect testing of heat exchanger tubes in nuclear power plants is described. It improves the defect detection sensitivity and the signal interpretation in the critical part of the tube sheet with its expansion. The electric current perturbation method for the inspection on surface or near surface defects especially in austenitic componentsis considered.The interpretation of the measured signals is supported by computer results coming out from numerical models.
An eddy current system using portable precision scanners and signal analysis techniques developed in the nuclear industry has been applied to aircraft inspections. Using custom designed probes, multifrequency mixing, and digital signal processing, the detection criteria of 10% loss of wall on the interior faying surface and cracks 60 mils (1 .S mm) in length have been accomplished. Real time signal processing that requires a minimal amount of computation has been implemented in an eddy current imaging system. The signal processing produces spatial displays, in the C-scan format. of amplitude (in phase or quadrature) magnitude, phase of spatial derivatives of these parameters.
52537
Hoshikawa,
H.; Kayama,
K.; Kaida, J.; Ishibashi,
Y. 52251
Fundamental studies of remote field eddy-current inspection Conference on Nondestructive Evaluation in the Nuclear Industry, Tokyo (Japan), 25-28 Apr. 1988. pp. 339-344. Edited by K. lida, J.E. Doherty and X. Edelmann. ASM (1988)
Kawahe,
T.; Hasahara,
D.L.; Sullivan,
signal
analysis
S.P.
in small-bore (Apr. 1993)
A simple method for obtaining the depth of metal-loss defects in smallbore ferromagnetic tubes by using the remote-field eddy current method is described. Research and analysis were carried out using a probe equipped with a solenoidal detector coil coaxial with the pipe, scanning uniformdepth metal-loss defects shorter than the overall probe length. On a voltage plane polar plot, which is similar to the voltage plane used in conventional eddy current analysis, the variations in signal amplitude and phase caused by metal loss trace out an elongated loop known as a defect-signal trace. The length of the defect-signal trace indicates the cross-sectional area of metal loss. The experimental results are explained with reference to the skin-depth equation.
Y.
5 1735
Eddy current flaw detector
Moulder,
J.C.; Nakagawa,
N.
Characterizing the performance of eddy current probes using photoinductive field-mapping 00000673
British Patent No. 2,255,184 (28 Oct. 1992) A flaw detector for metal material which can check pipelines by means of the remote field eddy current method comprises an exciting coil EC fed with a.c., and a set of receiving coils RCl -RC9. The signal picked up in each receiving coil is filtered and passed via an a.g.c. circuit to a phase comparator which also receives a reference signal from the source. The
Research in Nondestructive Evaluation,
Vol. 4, No. 4, pp. 221-236
(I 992) We present a new method for characterizing current probes by mapping their electromagnetic
the performance of eddy tields. The technique is
based on the photoinductive effect. the change in the impedance of an eddy current probe induced by laser heating of the material under the probe. The instrument we developed maps a probe’s electric field distribution by scanning an infrared laser beam over a thil film of gold lying underneath the probe. Measuremenrs of both photoinductive signals and flaw signals for a series of similar probes demonstrate that the impedance change caused by an electrical-discharge-machined (EDM) notch or a fatigue crack is proportional to the strength of the photoinductive signal. Thus, photoinductive measurements can supplant the use of artifact standards to calibrate eddy current probes. To model commercial eddy current probes with ferrite cores, we developed a procedure to treat them as effective air-core probes. We obtained good agreement between the flaw signals calculated using this effective-coil approach and actual fatigue-crack signals measured with commercial probes. We also calculated probabilities of detection for target flaws in titanium alloys for a series of commercial probes.
comparator output is passed to a flaw detection signal generator. In an alternative embodiment, the receiving coil signals are processed in pairs, with phase adjustment of one signal of each pair. Thus stable phase detection can be obtained and precise diagnosis of the pipeline to be tested can be performed, without generation of spurious flaw indications. Further, by using an a.g.c. circuit to maintain the signal level provided by the receiving coils, S/N ratio of the flaw data can be improved.
523 I I
D.D.; Atherton,
Materials Evaluation, Vol. 5 I, No. 4. pp. 492-495,500
Remote field eddy current technique used for inspection of magnetic tubes has been studied through both experiment and finite element analysis. A defect in the remote field area causes significant change in the magnetic field around it inside the tube. External and internal defects in a magnetic tube can be detected from the tube’s inside with almost the same sensitivity. The phase rather than the amplitude of the defect signal is appropriate to detect defect depth. The amplitude of the defect signal decays as the test frequency becomes higher, while the phase becomes maximum at a certain frequency.
52316
Mackintosh,
Remote-field eddy current ferromagnetic tubes
9th International
Lund, F.P.
Eddy current flaw size detecting probe British Patent No. 2,256,7 I3 (16 Dec. 1992) The probe, for generating a signal indicative
of a quantitative of the size of a surface defect, comprises a magnetic field for inducing currents in the surface and a perturbation current sensor arrangement positioned relative to the field to give an output providing said quantitative measure. The probe comprises a solid cylindrical former on which is wound the perturbation current sensing coils which are rectangular or figure of eight shaped and have axes radial to the former. The tield generator coil has an axis aligned with the axis of the former and is constructed to produce a magnetic field which produces a spatially varied magnetic field in a material under test. measurement
51733
Delsarte,
G.; Levy, R.
MASCOTTE: analytical model of eddy current signals. (In French, English Abstract) Mermoires et Etudes Scientifiques Revue de Metallurgic, No. IO, pp. 653-658 (Oct. 1992)
176
Vol. 89,