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Flux density measurement in ferromagnetic tubular product
NDT Abstracts outside of the pipe. Detector design, including the use of neodymium-ironboron magnets and finite-element flux leakage calculations, is described. Experimental results are presented and signal processing and noise are discussed. A hydraulically pressurized sealed pipe has been used to investigatethe effects of line-pressure stresson detector performance. 38251
Atherton, D.L.; Cheng, C.W.
A large Hall probe read head sensor for magnetic flux leakage inspection of pipelines Canadian Society for Nondestructive Testing, Vol. 8, No. 6, pp. 44, 46-50 (Nov./Dee. 1987) A magnetic flux leakage sensorusing a flux concentratorin the form of a read head with a Hall probe in the back air gap for use in pipeline inspection tools is described. Unlike the more usual inductive sensecoils the read head produces a velocity independent signal. It also increases the scan width achievable with a Hall probe by at leasta factor of ten. Finite element design optimization of the read head and shield are described.These give a signal amplitude dependent on defect penetration but essentially independentof defect width. Test results are given.
37628 Atherton, D.L.; Daly, M.G. Finite element calculation of magnetic flux leakage detector signals NDT International, Vol. 20, No. 4, pp. 235-238 (Aug. 1987) Two-dimensional finite element calculations are presented for anomalous leakage fluxes generated by nearside and farside grooves in pipes inspectedby magnetic flux leakage anomaly detectors. Flux density (B) is shown to be a non-linear function of penetration, increasing rapidly for deep grooves.This is contrary to previous analysesof cracks or grooves in plates using constant-field (H) excitation. The difference is due to the inclusion of the anomaly detectorassemblywhich tends to act with constant flux, particularly for detectors excited by permanent magnets. The new results are therefore of greater practical relevance.
37408
Nikolaenko, A.T.; Cuba, A.A.
Nondestructive local and average wall-thickness monitoring for ferromagnetic tubes Industrial Laboratory, Vol. 52, No. 10, pp. 905-906 (Apr. 1987)
Eddy current testing of metals Materials and Design, Vol. 8, No. 6, pp. 340-345 (Nov./Dee. 1987)
An instrument which uses a transverse magnetic field for monitoring wall thickness in tubes during manufacture has been developed. Recent modifications permit its use at temperaturesup to I50 C, tube diameters of up to 60 mm and wall thicknessesof up to 8 mm. A high level of stability in continuoususe has been recorded.
Eddy currentscan be used for testing metals for changesin composition, structure and hardness, and for detecting and measuring surface and sub-surface defects. They can also be applied to measuring changes in dimensions of rods and t&s and thicknesses of metal plates and non-metallic coatings on metal substrates and metal coatings on nonmetallic substrates.
37406 NDT Technologies, Inc., Method and apparatus for magnetically inspecting elongated objects for structural defects U.S. Patent No. 4,659,991 (21 Apr. 1987)
37936
37935
Blitz, J.
Atherton, D.L.; Szpunar, B.; Sullivan, S.
The application of finite-elmement calculations to the remotefield inspection technique Materials Evaluation, Vol. 45, No. 9, pp. 1083-1086 (Sep. 1987) The remote-field technique is a new method used for through-wall eddy current inspection of pipes. There are may intriguing experimental results connectedwith this technique.Finite-element calculationscan be used in the interpretation of these experimental results even though the magnetic fields measured in the remote-field techlniqueare very small.
37932 Denton, C. New inspection techniques yield good results in the field
Nuclear Engineering
International, Vol. 33, No. 402, pp. 31-32
(Jan. 1988) Recent experience with three new eddy current steam generator inspection techniques has tended to confirm their effectivenessin practical applications. Computer Data Screening helps minimize human error; three-frequency mixing helps with the difficult problem of sizing a multiple crack close to the tube sheet; whille a new rotating probe techniquefor Row 1 and 2 U-bends should prove invaluable for assessingthe effectivenessof in situ heat treatments for small mdius U-betids.
37638 Anon. Intelligent pigs now inspect pipelines down to 200 mm diameter Anti-Corrosion, Vol. 34, No. 10, pp. 7-8 (Oct. 1987) Inspection of high pressureoil and gas transmissionpipelines to within 1.5 metres with diameters down to 200 mm (8 inches) is being carried out using a new system developed by British Gas plc. The system uses inspectionvehicles known as “intelligent pigs” to magnet& a sectionof the pipe wall as the “pig” moves along in the current flow and then monitorsany local disturbancesin the field. The new system provides a lower cost, high precision alternative to hydrostatic pressuretesting and, using miniaturised electronics, can identify any me&l loss or mechanical damage.
37629
Atherton, D.L.; Czura, W.
Finite element calculations on the effects of permeability variation on magnetic flux leakage signals NDT International, Vol. 20, No. 4, pp. 239-241 (Aug. 1987) Magnetic flux leakage anornaly signals from pipeline inspection tools can be obtained from hard spotsor other regions of anomalouspermeability. The signals obtained from cormsion pits are dependenton pressureand this is attributed to stress-induced permeability changes. The results of two-dimensional finite element calculations of the effects of permeability measurementson such signals suggestthat permeability changesby as much as a factor of two may be requilad to producethese effects.
A magnetic inspection device for nondestructively detecting loss in metallic cross section and localized discontinuities in elongated objects, such as wire cables, rods, pipes, and the like has been developed.
37169
Stanley, R.K.
Use of inductive ammeters to ensure saturation of tubular magnetic materials using the internal conductor method Materials Evaluation, Vol. 45, No. 6, pp. 594-598 (Jun. 1987) A previous article outlined the use of inductive ammeters to check both the measurable parameters of a current pulse from a capacitor discharge (CD) system and the effectivenessof the magnetic field intensity (H) from such a pulse in magnetizing a ferromagnetic tubular material. The following short article provides proof that the inductive ammeter can be used to construct a specification for magnetization by this method, thereby obviating unscientific specificationsaccording to “amperesper inch of pipe outer diameter”.
37159
Spierer E.D.
Flux density measurement in ferromagnetic tubular Electromagnetic Methods of Nondestructive Testing. William Lord. Nondestructive Testing Monographs and 3, pp. 161- 173. Gordon and Breach Science Publishers
product Edited by Tracts, Vol.
(1985). Flux leakage testing of ferromagnetic tubular product for defects requiresthat the flux density in suchproduct be near 95% of saturationwhen being tested. If the flux density in the material under test is significantly below saturation, inside-diameter and mid- wall defects will be missed. Until recently there has been no means of determining the value of the flux density in the tubular product or whether this value is maintained during testing in order to validate the test. This paper presents a solution to the problem of continuous determination of the flux density in the material under test.
37158 Moake, G.L.; Stanley, R.K. Capacitor discharge magnetization of oil country tubular goods Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 15 I- 160. Gordon and Breach Science Publishers (1985). The circular magnetization of Oil Country Tubular Goods (OCTG) is normally performed by capacitor discharge (CD) along a “central” conductor which is insulated from the tube being magnetized. The magnetization process is complicated by the induction of an eddy current which flows in a manner which opposes penetration of the magnetizing field. In this article, we outline the development of a CD system which will adequately magnetize a wide range of OCTG, despite the demagnetizing effect of the eddy current. We also discuss the effectiveness of multiple pulsing.
Atherton, D.L.; Cheng, C.W.
A large Hall probe read head sensor for magnetic flux leakage inspection of pipelines Canadian Society for Nondestructive Testing, Vol. 8, No. 6, pp. 44, 46-50 (Nov./Dee. 1987) A magnetic flux leakage sensorusing a flux concentratorin the form of a read head with a Hall probe in the back air gap for use in pipeline inspection tools is described. Unlike the more usual inductive sensecoils the read head produces a velocity independent signal. It also increases the scan width achievable with a Hall probe by at leasta factor of ten. Finite element design optimization of the read head and shield are described.These give a signal amplitude dependent on defect penetration but essentially independentof defect width. Test results are given.
37628 Atherton, D.L.; Daly, M.G. Finite element calculation of magnetic flux leakage detector signals NDT International, Vol. 20, No. 4, pp. 235-238 (Aug. 1987) Two-dimensional finite element calculations are presented for anomalous leakage fluxes generated by nearside and farside grooves in pipes inspectedby magnetic flux leakage anomaly detectors. Flux density (B) is shown to be a non-linear function of penetration, increasing rapidly for deep grooves.This is contrary to previous analysesof cracks or grooves in plates using constant-field (H) excitation. The difference is due to the inclusion of the anomaly detectorassemblywhich tends to act with constant flux, particularly for detectors excited by permanent magnets. The new results are therefore of greater practical relevance.
37408
Nikolaenko, A.T.; Cuba, A.A.
Nondestructive local and average wall-thickness monitoring for ferromagnetic tubes Industrial Laboratory, Vol. 52, No. 10, pp. 905-906 (Apr. 1987)
Eddy current testing of metals Materials and Design, Vol. 8, No. 6, pp. 340-345 (Nov./Dee. 1987)
An instrument which uses a transverse magnetic field for monitoring wall thickness in tubes during manufacture has been developed. Recent modifications permit its use at temperaturesup to I50 C, tube diameters of up to 60 mm and wall thicknessesof up to 8 mm. A high level of stability in continuoususe has been recorded.
Eddy currentscan be used for testing metals for changesin composition, structure and hardness, and for detecting and measuring surface and sub-surface defects. They can also be applied to measuring changes in dimensions of rods and t&s and thicknesses of metal plates and non-metallic coatings on metal substrates and metal coatings on nonmetallic substrates.
37406 NDT Technologies, Inc., Method and apparatus for magnetically inspecting elongated objects for structural defects U.S. Patent No. 4,659,991 (21 Apr. 1987)
37936
37935
Blitz, J.
Atherton, D.L.; Szpunar, B.; Sullivan, S.
The application of finite-elmement calculations to the remotefield inspection technique Materials Evaluation, Vol. 45, No. 9, pp. 1083-1086 (Sep. 1987) The remote-field technique is a new method used for through-wall eddy current inspection of pipes. There are may intriguing experimental results connectedwith this technique.Finite-element calculationscan be used in the interpretation of these experimental results even though the magnetic fields measured in the remote-field techlniqueare very small.
37932 Denton, C. New inspection techniques yield good results in the field
Nuclear Engineering
International, Vol. 33, No. 402, pp. 31-32
(Jan. 1988) Recent experience with three new eddy current steam generator inspection techniques has tended to confirm their effectivenessin practical applications. Computer Data Screening helps minimize human error; three-frequency mixing helps with the difficult problem of sizing a multiple crack close to the tube sheet; whille a new rotating probe techniquefor Row 1 and 2 U-bends should prove invaluable for assessingthe effectivenessof in situ heat treatments for small mdius U-betids.
37638 Anon. Intelligent pigs now inspect pipelines down to 200 mm diameter Anti-Corrosion, Vol. 34, No. 10, pp. 7-8 (Oct. 1987) Inspection of high pressureoil and gas transmissionpipelines to within 1.5 metres with diameters down to 200 mm (8 inches) is being carried out using a new system developed by British Gas plc. The system uses inspectionvehicles known as “intelligent pigs” to magnet& a sectionof the pipe wall as the “pig” moves along in the current flow and then monitorsany local disturbancesin the field. The new system provides a lower cost, high precision alternative to hydrostatic pressuretesting and, using miniaturised electronics, can identify any me&l loss or mechanical damage.
37629
Atherton, D.L.; Czura, W.
Finite element calculations on the effects of permeability variation on magnetic flux leakage signals NDT International, Vol. 20, No. 4, pp. 239-241 (Aug. 1987) Magnetic flux leakage anornaly signals from pipeline inspection tools can be obtained from hard spotsor other regions of anomalouspermeability. The signals obtained from cormsion pits are dependenton pressureand this is attributed to stress-induced permeability changes. The results of two-dimensional finite element calculations of the effects of permeability measurementson such signals suggestthat permeability changesby as much as a factor of two may be requilad to producethese effects.
A magnetic inspection device for nondestructively detecting loss in metallic cross section and localized discontinuities in elongated objects, such as wire cables, rods, pipes, and the like has been developed.
37169
Stanley, R.K.
Use of inductive ammeters to ensure saturation of tubular magnetic materials using the internal conductor method Materials Evaluation, Vol. 45, No. 6, pp. 594-598 (Jun. 1987) A previous article outlined the use of inductive ammeters to check both the measurable parameters of a current pulse from a capacitor discharge (CD) system and the effectivenessof the magnetic field intensity (H) from such a pulse in magnetizing a ferromagnetic tubular material. The following short article provides proof that the inductive ammeter can be used to construct a specification for magnetization by this method, thereby obviating unscientific specificationsaccording to “amperesper inch of pipe outer diameter”.
37159
Spierer E.D.
Flux density measurement in ferromagnetic tubular Electromagnetic Methods of Nondestructive Testing. William Lord. Nondestructive Testing Monographs and 3, pp. 161- 173. Gordon and Breach Science Publishers
product Edited by Tracts, Vol.
(1985). Flux leakage testing of ferromagnetic tubular product for defects requiresthat the flux density in suchproduct be near 95% of saturationwhen being tested. If the flux density in the material under test is significantly below saturation, inside-diameter and mid- wall defects will be missed. Until recently there has been no means of determining the value of the flux density in the tubular product or whether this value is maintained during testing in order to validate the test. This paper presents a solution to the problem of continuous determination of the flux density in the material under test.
37158 Moake, G.L.; Stanley, R.K. Capacitor discharge magnetization of oil country tubular goods Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 15 I- 160. Gordon and Breach Science Publishers (1985). The circular magnetization of Oil Country Tubular Goods (OCTG) is normally performed by capacitor discharge (CD) along a “central” conductor which is insulated from the tube being magnetized. The magnetization process is complicated by the induction of an eddy current which flows in a manner which opposes penetration of the magnetizing field. In this article, we outline the development of a CD system which will adequately magnetize a wide range of OCTG, despite the demagnetizing effect of the eddy current. We also discuss the effectiveness of multiple pulsing.