Magnetic flux leakage inspection method and apparatus including magnetic diodes

Claim 2

An inspection apparatus for inspecting a magnetizable test object having at least one surface, said apparatus comprising a support; magnetizing means mounted on said support for magnetizing said test object; sensing means mounted on the support adjacent to said magnetizing means and for detecting magnetic flux leakage from the test obect caused by flaws in the test object, said sensing means including a plurality of single magnetic diodes disposed in pairs in magnetic opposition and connected electrically to form twin diodes whose output signals are substantially independent of temperature; and means cooperating with said support for moving said support to cause the magnetizing and sensing means to traverse the surface of the test object in sufficiently close proximity to magnetize said test object and to inspect said test object with said sensing means; wherein the twin diodes are connected electrically to form at least two separate groups, each group having a plurality of twin diodes; and the twin diodes in each group are spaced along a path so that the distance between the centers of any two adjacent twin diodes in that group is no more than approximately one-half the longest linear dimension along said path of the smallest flaw sought to be detected; and the groups are spaced along the path so that each group is adjacent to at least one other group; and the groups are spaced along the path in overlaPping relationship so that at least one twin diode in each group is between at least two twin diodes of each adjacent group, whereby said smallest flaw will be detected by at least two twin diodes in one of the groups when said path of twin diodes is moved over said flaw.

Claim 3

The apparatus of claim 1 including recording means connected to said sensing means for making a record of the magnetic flux leakage detected by the sensing means.

Claim 4

The apparatus of claim 2, wherein said twin diodes in each group comprise two sets of single diodes, with all of the single diodes in the first set being generally of one magnetic orientation and all of the single diodes of the second set being generally of an opposite magnetic orientation; and the single diodes of the first set are connected in series; and the single diodes of the second set are connected in series; and the two sets are connected to each other in series, whereby the difference between the voltage across each set of diodes is substantially independent of temperature.

Claim 5

An inspection apparatus for traveling through and inspecting a magnetizable pipeline, said apparatus comprising a support; magnetizing means mounted on said support for magnetizing successive portions of said pipeline; sensing means mounted on the support adjacent to said magnetizing means for detecting magnetic flux within the pipeline, said sensing means including a plurality of twin magnetic diodes, each twin diode comprising two single magnetic diodes; and propelling means for moving said apparatus through the pipeline to cause the magnetizing and sensing means to traverse the interior wall of the pipeline in sufficiently close proximity to magnetize said pipeline and to detect magnetic flux leakage from said pipeline caused by defects in said pipeline, wherein the twin diodes are spaced along a path so that the centers of adjacent twin diodes are no farther apart than approximately one-half the longest linear dimension along said path of the smallest flaw sought to be detected, whereby said smallest flaw will be detected by at least two twin diodes when said twin diodes move over said flaw.

Claim 6

An inspection apparatus for traveling through and inspecting a magnetizable pipeline, said apparatus comprising a support; magnetizing means mounted on said support for magnetizing successive portions of said pipeline; sensing means mounted on the support adjacent to said magnetizing means for detecting magnetic flux within the pipeline, said sensing means including a plurality of twin magnetic diodes, each twin diode comprising two single magnetic diodes; and propelling means for moving said apparatus through the pipeline to cause the magnetizing and sensing means to traverse the interior wall of the pipeline in sufficiently close proximity to magnetize said pipeline and to detect magnetic flux leakage from said pipeline caused by defects in said pipeline, wherein the twin diodes are spaced along a path so that the centers of adjacent twin diodes are no farther apart than approximately one-half the longest linear dimension along said path of the smallest flaw sought to be detected, whereby said smallest flaw will be detected by at least two twin diodes when said twin diodes move over said flaw.

Claim 7

The apparatus of claim 4 including recording means connected to said sensing means for making a record of the magnetic flux detected by the sensing means.

Claim 8

The apparatus of claim 4 wherein said sensing means are oriented to detect primarily that component of the magnetic flux which is substantially parallel to the longitudinal axis of the pipeline.

Claim 9

An inspection apparatus for traveling through and inspecting a magnetizable pipeline, said apparatus comprising a support; magnetizing means mounted on said support for magnetizing successive portions of said pipeline; sensing means mounted on the support adjacent to said magnetizing means for detecting magnetic flux within the pipeline, said sensing means including a plurality of twin magnetic diodes, each twin diode comprising two single magnetic diodes; and propelling means for moving said apparatus through the pipeline to cause the magnetizing and sensing means to traverse the interior wall of the pipeline in sufficiently close proximity to magnetize said pipeline and to detect magnetic flux leakage from said pipeline caused by defects in said pipeline, wherein the twin diodes are connected electrically to form at least two separate groups, each group having a plurality of twin diodes; and the twin diodes in each group are spaced along a path so that the distance between the centers of any two adjacent twin diodes in that group is no more than approximately one-half the longest linear dimension along said path of the smallest flaw sought to be detected; and the groups are spaced along the path so that each group is adjacent to at least one other group; and the groups are spaced along the path in overlapping relationship so that at least one of the twin diodes in each group is between at least Two twin diodes of each adjacent group, whereby said smallest flaw will be detected by at least two twin diodes in one of the groups when said path of twin diodes is moved over said flaw.

Claim 10

An inspection apparatus for traveling through and inspecting a magnetizable pipeline, said apparatus comprising a support; magnetizing means mounted on said support for magnetizing successive portions of said pipeline; sensing means mounted on the support adjacent to said magnetizing means for detecting magnetic flux within the pipeline, said sensing means including a plurality of twin magnetic diodes, each twin diode comprising two single magnetic diodes; and propelling means for moving said apparatus through the pipeline to cause the magnetizing and sensing means to traverse the interior wall of the pipeline in sufficiently close proximity to magnetize said pipeline and to detect magnetic flux leakage from said pipeline caused by defects in said pipeline, wherein the twin diodes are connected electrically to form at least two separate groups, each group having a plurality of twin diodes; and the twin diodes in each group are spaced along a path so that the distance between the centers of any two adjacent twin diodes in that group is no more than approximately one-half the longest linear dimension along said path of the smallest flaw sought to be detected; and the groups are spaced along the path so that each group is adjacent to at least one other group; and the groups are spaced along the path in overlapping relationship so that at least one of the twin diodes in each group is between at least Two twin diodes of each adjacent group, whereby said smallest flaw will be detected by at least two twin diodes in one of the groups when said path of twin diodes is moved over said flaw.

Claim 11

The apparatus of claim 7 including recording means connected to said sensing means for making a record of the magnetic flux detected by the sensing means.

Claim 12

The apparatus of claim 8, wherein said twin diodes in each group comprise two sets of single diodes, with all of the single diodes in the first set being generally one magnetic orientation and all of the single diodes of the second set being generally of an opposite magnetic orientation; and the single diodes of the first set are connected in series; and the single diodes of the second set are connected in series; and the two sets are connected to each other in series, whereby the difference between the voltage drops across each set of diodes substantially independent of temperature.

Claim 13

The apparatus of claim 8, including differential means connected to at least two of said groups of twin diodes and to said recording means for determining and recording the difference of twin signals from said two groups, whereby the difference between the magnetic flux is detected by said groups may be determined and recorded.

Claim 14

The apparatus of claim 8, including filter means connected to at least one of said groups of twin diodes transmitting only a selected number of the larger signals received at any one time from said groups of twin diodes.

Claim 15

An inspection apparatus for traveling through and inspecting a magnetizable pipeline, said apparatus comprising a support; magnetizing means mounted on said support for magnetizing successive portions of said pipeline; sensing means mounted on the support adjacent to said magnetizing means for detecting magnetic flux within the pipeline, said sensing means including a plurality of twin magnetic diodes, each twin diode comprising two single magnetic diodes; propelling means for moving said apparatus through the pipeline to cause the magnetizing and sensing means to traverse the interior wall of the pipeline in sufficiently close proximity to magnetize said pipeline and to detect magnetic flux leakage from said pipeline caused by defects in said pipeline; and recording means connected to said sensing means for making a record of the magnetic flux detected by the sensing means, said recording means having at least two channels; and a first filter means connected to at least one of said twin diodes and to at least one channel of said recording means to transmit to said recording means only a selected number of the larger positive signals from said twin diode; and a second filter means connected to at least one of said twin diodes and to a different channel of said recording means to transmit to said recording means only negative signals from said twin diode, wherein one of said positive and negative signals is representative of flux leakage caused by flaws in the pipeline and the other of said signals is representative of flux flow caused by magnetic markers placed near said pipeline, whereby both flux leakage from flaws in the pipeline and flux flow caused by said markers may be detected together by said twin diodes and recorded on separate channels by said recording means.

Claim 16

An inspection apparatus for traveling through and inspecting a magnetizable pipeline, said apparatus comprising a support; magnetizing means mounted on said support for magnetizing successive portions of said pipeline; sensing means mounted on the support adjacent to said magnetizing means for detecting magnetic flux within the pipeline, said sensing means including a plurality of twin magnetic diodes, each twin diode comprising two single magnetic diodes; propelling means for moving said apparatus through the pipeline to cause the magnetizing and sensing means to traverse the interior wall of the pipeline in sufficiently close proximity to magnetize said pipeline and to detect magnetic flux leakage from said pipeline caused by defects in said pipeline; and recording means connected to said sensing means for making a record of the magnetic flux detected by the sensing means, said recording means having at least two channels; and a first filter means connected to at least one of said twin diodes and to at least one channel of said recording means to transmit to said recording means only a selected number of the larger positive signals from said twin diode; and a second filter means connected to at least one of said twin diodes and to a different channel of said recording means to transmit to said recording means only negative signals from said twin diode, wherein one of said positive and negative signals is representative of flux leakage caused by flaws in the pipeline and the other of said signals is representative of flux flow caused by magnetic markers placed near said pipeline, whereby both flux leakage from flaws in the pipeline and flux flow caused by said markers may be detected together by said twin diodes and recorded on separate channels by said recording means.

Claim 17

An inspection apparatus for traveling through and inspecting a magnetizable pipeline conducting fluid, said apparatus comprising a battery capsule including sufficient batteries to supply power for said apparatus; a magnet module connected to said battery capsule and including at least one magnet assembly, said magnet assembly having a magnet to magnetize the pipeline as said apparatus travels therethrough and having a plurality of twin magnetic diodes to detect magnetic flux therein, said twin diodes comprising two single magnetic diodes and being connected electrically to form at least two separate grouPs, each group having a plurality of twin diodes; and the twin diodes in each group being spaced along a path so that the distance between the centers of any two adjacent twin diodes in that group is no more than approximately one-half the longest linear dimension along said path of the smallest flaw sought to be detected; and the groups being spaced along the path so that each group is adjacent to at least one other group; and the groups being spaced along the path in overlapping relationship so that at least one twin diode in each group is between at least two twin diodes of each adjacent group; and a recorder capsule connected to said magnet module and including a recorder connected to said twin diodes to make a record of said detected magnetic flux; and a plurality of annular cups secured to said battery capsule, magnet module and recorder capsule and engaging said pipeline, whereby, as said fluid impinges on said apparatus, it will travel through the pipeline magnetizing successive portions thereof and detecting and recording magnetic flux leakage caused by flaws therein, and said smallest flaw will be detected by at least two twin diodes in one of the groups when said path of twin diodes is moved over said flaw.

Claim 18

An inspection apparatus for traveling through and inspecting a magnetizable pipeline conducting fluid, said apparatus comprising a battery capsule including sufficient batteries to supply power for said apparatus; a magnet module connected to said battery capsule and including at least one magnet assembly, said magnet assembly having a magnet to magnetize the pipeline as said apparatus travels therethrough and having a plurality of twin magnetic diodes to detect magnetic flux therein, said twin diodes comprising two single magnetic diodes and being connected electrically to form at least two separate grouPs, each group having a plurality of twin diodes; and the twin diodes in each group being spaced along a path so that the distance between the centers of any two adjacent twin diodes in that group is no more than approximately one-half the longest linear dimension along said path of the smallest flaw sought to be detected; and the groups being spaced along the path so that each group is adjacent to at least one other group; and the groups being spaced along the path in overlapping relationship so that at least one twin diode in each group is between at least two twin diodes of each adjacent group; and a recorder capsule connected to said magnet module and including a recorder connected to said twin diodes to make a record of said detected magnetic flux; and a plurality of annular cups secured to said battery capsule, magnet module and recorder capsule and engaging said pipeline, whereby, as said fluid impinges on said apparatus, it will travel through the pipeline magnetizing successive portions thereof and detecting and recording magnetic flux leakage caused by flaws therein, and said smallest flaw will be detected by at least two twin diodes in one of the groups when said path of twin diodes is moved over said flaw.

Claim 19

The apparatus of claim 13, wherein the two single diodes of the twin diodes are fixed in magnetic opposition and are connected electrically in series, whereby the output signals of said diodes are independent of temperature.

Claim 20

The apparatus of claim 13, wherein said twin diodes in each group comprise two sets of single diodes, with all of the single diodes in the first set being generally of one magnetic orientation and all of the single diodes of the second set being generally of the opposite magnetic orientation; and the single diodes of the first set are connected in series; and the single diodes of the second set are connected in series; and two sets are connected to each other in series, whereby the difference between the voltage drops across each set of diodes and is substantially independent of temperature.

Claim 21

The apparatus of claim 13, wherein the centers of adjacent twin diodes in each group are between one-quarter inch and three-eighths inches apart.

Claim 22

The apparatus of claim 13, including a filter in each magnet assembly connected to each of said groups of twin diodes in that magnet assembly and to said recorder to transmit to said recorder only the largest signal received at any one time from said groups of diodes in that magnet assembly.

Claim 23

The apparatus of claim 13, wherein said twin diodes are oriented to detect primarily that component of the magnetic flux which is substantially parallel to the longitudinal axis of the pipeline.

Claim 24

The apparatus of claim 17, including a second filter in each magnet assembly connected to one of said groups of twin diodes in that magnet assembly and to said recorder to transmit to said recorder only the most negative signals received from said group.