Method for ultrasonic inspection of generator field teeth
First Claim
1. A method for ultrasonically inspecting a generator field tooth for the detection, characterization and/or sizing of cracks thereat, the generator having a rotor with an axis of rotation, the rotor having a plurality of field teeth extending radially outward with respect to the axis of rotation and having an elongated profile that extends parallel to the axis of rotation, the rotor having a plurality of sets of wedges disposed between adjacent teeth, a set of wedges having at least two wedges disposed end to end parallel to the axis of rotation so as to form a butt joint between adjacent ends, the teeth having an outer surface, and a load surface having boundaries that define a horizontal centerline at a vertical distance down from the outer surface, each wedge having a bearing surface disposed proximate the load surface such that in response to rotation of the rotor, the bearing surfaces bear against the load surface of the tooth, whereby the wedge is restrained from outward radial movement and the load surface experiences a load stress whereat fretting of the load surface may occur, the method comprising:
- selecting an electromagnetic acoustic transducer (EMAT) productive of a test signal having a defined angle of refection with respect to the tooth material;
positioning the EMAT at the outer surface of the tooth absent a fluid couplant;
orienting the EMAT so as to direct the test signal to propagate through the tooth toward the load surface where the butt joint is disposed; and
activating the EMAT so as to test the load surface proximate the butt joint for cracks thereat.
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Accused Products
Abstract
A method for ultrasonically inspecting a generator field tooth for the detection, characterization and/or sizing of cracks thereat is disclosed. An electromagnetic acoustic transducer (EMAT) productive of a test signal having a defined angle of refraction with respect to the tooth material is selected. The EMAT is positioned at an outer surface of the tooth absent a fluid couplant and oriented so as to direct the test signal to propagate through the tooth toward a load surface of the tooth where a butt joint of a set of wedges is disposed. The EMAT is activated so as to test the load surface proximate the butt joint for cracks thereat.
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Citations
21 Claims
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1. A method for ultrasonically inspecting a generator field tooth for the detection, characterization and/or sizing of cracks thereat, the generator having a rotor with an axis of rotation, the rotor having a plurality of field teeth extending radially outward with respect to the axis of rotation and having an elongated profile that extends parallel to the axis of rotation, the rotor having a plurality of sets of wedges disposed between adjacent teeth, a set of wedges having at least two wedges disposed end to end parallel to the axis of rotation so as to form a butt joint between adjacent ends, the teeth having an outer surface, and a load surface having boundaries that define a horizontal centerline at a vertical distance down from the outer surface, each wedge having a bearing surface disposed proximate the load surface such that in response to rotation of the rotor, the bearing surfaces bear against the load surface of the tooth, whereby the wedge is restrained from outward radial movement and the load surface experiences a load stress whereat fretting of the load surface may occur, the method comprising:
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selecting an electromagnetic acoustic transducer (EMAT) productive of a test signal having a defined angle of refection with respect to the tooth material;
positioning the EMAT at the outer surface of the tooth absent a fluid couplant;
orienting the EMAT so as to direct the test signal to propagate through the tooth toward the load surface where the butt joint is disposed; and
activating the EMAT so as to test the load surface proximate the butt joint for cracks thereat. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for ultrasonically inspecting a generator field tooth for the detection, characterization and/or sizing of cracks thereat, the tooth having a length, the tooth having a radial height with an outer surface, the tooth having a load surface that runs lengthwise with boundaries that define a horizontal centerline at a defined distance down from the outer surface, the method comprising:
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positioning an electromagnetic acoustic transducer (EMAT) productive of a test signal at the outer surface of the tooth;
orienting the EMAT so as to direct the test signal to propagate through the tooth from a point of entry at the tooth outer surface toward a region of interest on the horizontal centerline of the load surface at a defined distance from the point of entry; and
activating the EMAT so as to test the load surface for cracks at the region of interest. - View Dependent Claims (17, 18)
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19. A method for selecting an electromagnetic acoustic transducer (EMAT) capable of producing a test signal for inspecting a generator field tooth for the detection, characterization and/or sizing of cracks at a region of interest of the tooth, the tooth having a length, the tooth having a radial height with an outer surface, the tooth having a load surface that runs lengthwise and has boundaries that define a horizontal centerline at vertical a distance down from the outer surface, the method comprising:
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defining a direction vector for the test signal in the tooth such that the test signal is directed firm a point of entry at the tooth outer surface to the region of interest;
defining a skew angle and an angle of refraction that results in the test signal that follows the defined direction vector; and
selecting an EMAT with the desired angle of refraction capable of providing the test signal at the defined direction vector. - View Dependent Claims (20, 21)
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Specification