Apparatus for sensing thickness variations, discontinuities, and the like in elongated steel structures by measuring variations in magnetic properties utilizing a flux gate

Claim 2

Apparatus for determining the thickness of iron pipe which comprises: a. an electromagnet means having coaxial symmetry to the axis of said pipe for establishing a magnetic flux passing longitudinally through a length of the walls of said pipe, b. a circular magnetic shunt mounted coaxial to the axis of said electromagnet means spanning a central fraction of the pipe length through which said magnetic flux is passing and having means for cyclic time varying electromagnetic excitation thereof in a direction coaxial with said shunt, and c. means for sensing the axial portion of said magnetic flux passing through said shunt.

Claim 3

The combination set forth in claim 1 wherein means are provided for operation of said shunt as a flux gate.

Claim 4

The combination set forth in claim 1 wherein said shunt is an axially outwardly facing circular channel having flanges which are in juxtaposition to the inner wall of said pipe.

Claim 5

The combination set forth in claim 1 wherein said electromagnet means is of length about two diameters of said pipe, said shunt being centrally located thereon.

Claim 6

Apparatus for determining the magnetic variations in ferromagnetic pipe due to cracks, thinning or the like which comprises: a. an elongated magnetizable spool having a coil thereon and circular end flanges the peripheries of which face the inner wall of said pipe in two annular zones spaced apart along said pipe to establish upon energization a magnetic field in said pipe between said flanges which said magnetic field is below saturation, b. a short saturable magnetizable spool surrounding and spanning a central portion of said elongated spool and having a circumferential sensing coil thereon and a toroidal excitation coil, c. a source of alternating current coupled to said toroidal coil for energizing said toroidal coil to drive said short spool periodically toward saturation, and d. means coupled to said sensing coil operable in dependency upon the flux in said sensing coil to generate a signal representative of the flux in said short spool.

Claim 7

Apparatus for determining the magnetic variations in ferromagnetic pipe due to cracks, thinning or the like which comprises: a. an elongated magnetizable spool having a coil thereon and circular end flanges the peripheries of which face the inner wall of said pipe in two annular zones spaced apart along said pipe to establish upon energization a magnetic field in said pipe between said flanges which said magnetic field is below saturation, b. a short saturable magnetizable spool surrounding and spanning a central portion of said elongated spool and having a circumferential sensing coil thereon and a toroidal excitation coil, c. a source of alternating current coupled to said toroidal coil for energizing said toroidal coil to drive said short spool periodically toward saturation, and d. means coupled to said sensing coil operable in dependency upon the flux in said sensing coil to generate a signal representative of the flux in said short spool.

Claim 8

Apparatus for determining the thickness of ferromagnetic pipe which comprises: a. en electromagnet having symmetry to the axis of said pipe with spaced-apart, circular pole pieces the peripheries of which are facing the inner walls of said pipe, b. a detector structure having symmetry to the axis of said pipe with circular flux-receiving peripheral extremities facing the inner walls of said pipe and located between said pole pieces and having a toroidal excitation coil, c. a source of alternating current of low frequency for energizing said electromagnet, d. a source of alternating current of high frequency for energizing said toroidal coil, and e. means for sensing the component of the magnetic field in said detector structure having the low frequency.

Claim 9

Apparatus for determining the thickness of ferromagnetic pipe which comprises: a. en electromagnet having symmetry to the axis of said pipe with spaced-apart, circular pole pieces the peripheries of which are facing the inner walls of said pipe, b. a detector structure having symmetry to the axis of said pipe with circular flux-receiving peripheral extremities facing the inner walls of said pipe and located between said pole pieces and having a toroidal excitation coil, c. a source of alternating current of low frequency for energizing said electromagnet, d. a source of alternating current of high frequency for energizing said toroidal coil, and e. means for sensing the component of the magnetic field in said detector structure having the low frequency.

Claim 10

Apparatus for determining the magnetic variations in ferromagnetic pipe due to cracks, thinning or the like which comprises: a. an elongated magnetizable spool having a coil thereon and circular end flanges the peripheries of which face the inner wall of said pipe in annular zones spaced along said pipe, b. a source of alternating current for energizing said coil at low frequency to establish a magnetic field in the pipe between said flanges which is below saturation, c. a short, magnetizable spool spanning a central portion of said elongated spool and having a circumferential sensing coil thereon and a toroidal excitation coil, d. a source of alternating current for energizing said toroidal coil at high frequency to drive said short Spool periodically toward saturation, and e. means to detect a signal at said low frequency from the current induced in said sensing coil.

Claim 11

Apparatus for determining the magnetic variations in ferromagnetic pipe due to cracks, thinning or the like which comprises: a. an elongated magnetizable spool having a coil thereon and circular end flanges the peripheries of which face the inner wall of said pipe in annular zones spaced along said pipe, b. a source of alternating current for energizing said coil at low frequency to establish a magnetic field in the pipe between said flanges which is below saturation, c. a short, magnetizable spool spanning a central portion of said elongated spool and having a circumferential sensing coil thereon and a toroidal excitation coil, d. a source of alternating current for energizing said toroidal coil at high frequency to drive said short Spool periodically toward saturation, and e. means to detect a signal at said low frequency from the current induced in said sensing coil.

Claim 12

Apparatus for determining the thickness of ferromagnetic pipe where a magnetic flux passes longitudinally in the walls of said pipe, which comprises: a. an annular magnetic shunt, including an annular channel the peripheries of which face the pipe and having coaxial symmetry to the axis of said pipe, and spanning a short portion of the pipe length and having means for cyclic time varying electromagnetic excitation of said shunt in a circular direction coaxial with said shunt, and b. means coupled to said shunt for sensing the axial portion of said magnetic flux passing through said shunt.

Claim 13

Apparatus for determining the thickness of ferromagnetic pipe where a magnetic flux passes longitudinally in the walls of said pipe, which comprises: a. an annular magnetic shunt, including an annular channel the peripheries of which face the pipe and having coaxial symmetry to the axis of said pipe, and spanning a short portion of the pipe length and having means for cyclic time varying electromagnetic excitation of said shunt in a circular direction coaxial with said shunt, and b. means coupled to said shunt for sensing the axial portion of said magnetic flux passing through said shunt.

Claim 14

Apparatus for determining the magnetic variations in ferromagnetic pipe due to cracks, thinning or the like where a magnetic field directed longitudinally in the walls of said pipe is below saturation which comprises: a. a short saturable magnetizable spool spanning a small portion of the length of said pipe and having a circumferential sensing coil thereon and a toroidal excitation coil, b. A source of alternating current for energizing said toroidal coil to drive said short spool periodically toward saturation, and c. means coupled to said sensing coil operable in dependence upon the flux in said sensing coil to generate a signal representative of the flux in said short spool.

Claim 15

Apparatus for determining the magnetic variations in ferromagnetic pipe due to cracks, thinning or the like where a magnetic field directed longitudinally in the walls of said pipe is below saturation which comprises: a. a short saturable magnetizable spool spanning a small portion of the length of said pipe and having a circumferential sensing coil thereon and a toroidal excitation coil, b. A source of alternating current for energizing said toroidal coil to drive said short spool periodically toward saturation, and c. means coupled to said sensing coil operable in dependence upon the flux in said sensing coil to generate a signal representative of the flux in said short spool.

Claim 16

Apparatus for measuring variations in magnetic properties of an elongated steel structure comprising: a. an electromagnetic means having coaxial symmetry with respect to an axis of said structure for establishing a magnetic flux passing longitudinally through a length of the elongated steel structure, b. a circular magnetic shunt mounted coaxial to the axis of said electromagnetic means and spanning a central fraction thereof and having means for cyclic time varying electromagnetic excitation thereof in a direction coaxial with said shunt, and c. means for sensing the axial portion of said magnetic flux passing through said shunt.

Claim 17

Apparatus for measuring variations in magnetic properties of an elongated steel structure comprising: a. an electromagnetic means having coaxial symmetry with respect to an axis of said structure for establishing a magnetic flux passing longitudinally through a length of the elongated steel structure, b. a circular magnetic shunt mounted coaxial to the axis of said electromagnetic means and spanning a central fraction thereof and having means for cyclic time varying electromagnetic excitation thereof in a direction coaxial with said shunt, and c. means for sensing the axial portion of said magnetic flux passing through said shunt.

Claim 18

Apparatus for measuring variations in magnetic properties of an elongated steel structure as set forth in claim 10 wherein said electromagnetic means includes an elongated magnetizable spool having a coil thereon and circular end flanges the peripheries of which face outward from the axis of said spool.

Claim 19

Apparatus for measuring variations in magnetic properties of an elongated steel structure as set forth in claim 10 wherein said circular magnetic shunt includes a short saturable magnetizable spool surrounding and spanning a central portion of said elongated magnetizable spool and having a circumferential sensing coil thereon and a toroidal excitation coil.