US3693075A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Eddy current system for testing tubes for defects,eccentricity,and wall thickness
Assignee: Individual
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Filing: 1970-10-16
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Granted: 1972-09-19
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Expires: 1990-10-16
Abstract
Abstract Electrically conductive nonferromagnetic or electrically conductive ferromagnetic tubes are tested for wall thickness, eccentricity or defects by the eddy current test method using the transmission coefficient. A coil system comprising an a-c excited primary coil means and an associated secondary (pickup) coil means is coupled sequentially to sections of the tube wall in such a manner that the tube wall section under test is disposed between the primary and the secondary coil means. In one embodiment the primary coil produces a magnetic field whose lines of force are perpendicular to the tube axis, in another embodiment the primary flux is directed axially to the tube. The flux transmitted through the tube wall is modified by the eddy current generated in the tube wall and the secondary coil means is inductively coupled to the flux emerging from the tube wall. Responsive to relative motion between the tube and coil systems an electrical signal appears at the secondary coil means which is evaluated by electrical circuit means for the physical characteristics of the tube. Various coil arrangements are disclosed to derive the stated parameters.
Inventors
- 👤 Friedrich M O Forster
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 13:33
CPC Classifications
G; G01; G01B; G01B7/00; G01B7/02; G01B7/06; G01B7/10; G01B7/107; G01B7/30; G01B7/31; G01B7/312; G01N; G01N27/00; G01N27/72; G01N27/82; G01N27/90; G01N27/9013; G01N27/902; G01N27/904; G01N27/9046
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
338 words
An apparatus for testing a tube made of electrically conductive nonferromagnetic or electrically conductive ferromagnetic material separately or simultaneously for defects, eccentricity and wall thickness with eddy currents comprising: primary coil means comprising a first and a second coil adapted to be disposed at diametrically opposed sections of the tube to be tested at one side of the tube wall to cause, when energized with alternating current, a pair of alternating magnetic fields, each field penetrating the respective tube wall section with lines of force which are substantially perpendicular to the tube wall whereby to cause in said sections eddy currents which modify the respective original alternating magnetic fields and cause counter-fields disposed at the other side of the respective tube wall sections opposite the locations of said first and second coils; means for energizing said first and second coils with alternating current to produce said alternating magnetic fields; secondary coil means adapted to be located at said other side of said tube wall sections opposite said first and second coils and for being coupled to respective portions of the lines of force of said respective alternating fields modified by said eddy currents; said secondary coil means comprising a third coil and a fourth coil, said fourth coil having two bifilarly wound windings, and said third coil being coupled in series with one winding of said bifilarly wound coil and coupled in opposition with the other winding of said bifilarly wound coil; means for causing relative motion between said tube and said primary and secondary coil means in a direction parallel to the tube axis and circumferentially about the tube surface, whereby to produce at the terminals of said secondary coil means an electrical output signal which is responsive to said motion, and means adapted to be coupled to said secondary coil means for receiving said electrical output signal and evaluating it for at least one of the properties comprising the presence of defects in the tube wall, eccentricity, and wall thickness of the tube portion under test.
Claim 2
Independent Claim
338 words
An apparatus for testing a tube made of electrically conductive nonferromagnetic or electrically conductive ferromagnetic material separately or simultaneously for defects, eccentricity and wall thickness with eddy currents comprising: primary coil means comprising a first and a second coil adapted to be disposed at diametrically opposed sections of the tube to be tested at one side of the tube wall to cause, when energized with alternating current, a pair of alternating magnetic fields, each field penetrating the respective tube wall section with lines of force which are substantially perpendicular to the tube wall whereby to cause in said sections eddy currents which modify the respective original alternating magnetic fields and cause counter-fields disposed at the other side of the respective tube wall sections opposite the locations of said first and second coils; means for energizing said first and second coils with alternating current to produce said alternating magnetic fields; secondary coil means adapted to be located at said other side of said tube wall sections opposite said first and second coils and for being coupled to respective portions of the lines of force of said respective alternating fields modified by said eddy currents; said secondary coil means comprising a third coil and a fourth coil, said fourth coil having two bifilarly wound windings, and said third coil being coupled in series with one winding of said bifilarly wound coil and coupled in opposition with the other winding of said bifilarly wound coil; means for causing relative motion between said tube and said primary and secondary coil means in a direction parallel to the tube axis and circumferentially about the tube surface, whereby to produce at the terminals of said secondary coil means an electrical output signal which is responsive to said motion, and means adapted to be coupled to said secondary coil means for receiving said electrical output signal and evaluating it for at least one of the properties comprising the presence of defects in the tube wall, eccentricity, and wall thickness of the tube portion under test.
Claim 3
Dependent Claim
30 words
An apparatus as set forth in claim 1, said primary and said secondary coil means being disposed stationary, and said means for causing relative motion imparting motion to the tube.
Claim 4
Dependent Claim
53 words
An apparatus as set forth in claim 1, said means adapted to be coupled for receiving said output signal comprising an electrical quotient forming circuit connected to said in series coupled and said in opposition coupled windings for providing a signal responsive to the quotient of the signals across said respective winding connections.
Claim 5
Independent Claim
336 words
An apparatus for testing a tube made of electrically conductive nonferromagnetic or electrically conductive ferromagnetic material separately or simultaneously for defects, eccentricity and wall thickness with eddy currents comprising: primary coil means comprising a first and a second coil adapted to be disposed at diametrically opposed sections of the tube to be tested at one side of the tube wall to cause, when energized with alternating current, a pair of alternating magnetic fields, each field penetrating the respective tube wall section with lines of force which are substantially perpendicular to the tube wall whereby to cause in said sections eddy currents which modify the respective original alternating magnetic fields and cause counter-fields disposed at the other side of the respective tube wall sections opposite the locations of said first and second coils; means for energizing said first and second coils with alternating current to produce said alternating magnetic fields; secondary coil means adapted to be located at said other side of said tube wall sections opposite said first and second coils and for being coupled to respective portions of the lines of force of said respective alternating fields modified by said eddy currents; said secondary coil means comprising a third coil and a fourth coil, said fourth coil having two windings, and said third coil being coupled in series with one of said windings of said fourth coil and coupled in opposition with the other winding of said fourth coil; means for causing relative motion between said tube and said primary and secondary coil means in a direction parallel to the tube axis and circumferentially about the tube surface, whereby to produce at the terminals of said secondary coil means an electrical output signal which is responsive to said motion, and means adapted to be coupled to said secondary coil means for receiving said electrical output signal and evaluating it for at least one of the properties comprising the presence of defects in the tube wall, eccentricity, and wall thickness of the tube portion under test.
Claim 6
Independent Claim
336 words
An apparatus for testing a tube made of electrically conductive nonferromagnetic or electrically conductive ferromagnetic material separately or simultaneously for defects, eccentricity and wall thickness with eddy currents comprising: primary coil means comprising a first and a second coil adapted to be disposed at diametrically opposed sections of the tube to be tested at one side of the tube wall to cause, when energized with alternating current, a pair of alternating magnetic fields, each field penetrating the respective tube wall section with lines of force which are substantially perpendicular to the tube wall whereby to cause in said sections eddy currents which modify the respective original alternating magnetic fields and cause counter-fields disposed at the other side of the respective tube wall sections opposite the locations of said first and second coils; means for energizing said first and second coils with alternating current to produce said alternating magnetic fields; secondary coil means adapted to be located at said other side of said tube wall sections opposite said first and second coils and for being coupled to respective portions of the lines of force of said respective alternating fields modified by said eddy currents; said secondary coil means comprising a third coil and a fourth coil, said fourth coil having two windings, and said third coil being coupled in series with one of said windings of said fourth coil and coupled in opposition with the other winding of said fourth coil; means for causing relative motion between said tube and said primary and secondary coil means in a direction parallel to the tube axis and circumferentially about the tube surface, whereby to produce at the terminals of said secondary coil means an electrical output signal which is responsive to said motion, and means adapted to be coupled to said secondary coil means for receiving said electrical output signal and evaluating it for at least one of the properties comprising the presence of defects in the tube wall, eccentricity, and wall thickness of the tube portion under test.
Claim 7
Dependent Claim
30 words
An apparatus as set forth in claim 4, said primary and said secondary coil means being disposed stationary, and said means for causing relative motion imparting motion to the tube.
Claim 8
Dependent Claim
53 words
An apparatus as set forth in claim 4, said means adapted to be coupled for receiving said output signal comprising an electrical quotient forming circuit connected to said in series coupled and said in opposition coupled windings for providing a signal responsive to the quotient of the signals across said respective winding connections.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-09-19 | 1976-03-20 | 1976-09-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-09-19 | 1980-03-20 | 1980-09-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-09-19 | 1984-03-20 | 1984-09-19 | $7700.00 | Window Closed / Lapsed |