Magnetic flaw detector for use with ferromagnetic small diameter tubular goods using a second magnetic field to confine a first magnetic field
AssigneeWestern Atlas International, Inc.
InventorJackson H. Hwang
Life of this patent
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Abstract
A magnetic flaw detector for use in small-diameter tubular goods employs a second magnetic field to confine a first magnetic field to reside within a desired volumetric region in the wall of a specimen under test. A flux leakage detector and a variable reluctance sensor provide means for detecting and discriminating between defects on the inner and outer surfaces of the specimen.
Claims6
A magnetic inspection probe for internal use for determining flaws in ferromagnetic tubular goods, comprising:
- a first magnetizer element having poles of opposite polarity for establishing a magnetic circuit in a wall of a specimen under study, said wall having inner and outer surfaces;
- a second magnetizer element having poles of opposite polarity for confining the magnetic field of the first magnetizer to a desired volumetric region in said wall;
- said first magnetizer element being positioned between the poles of said second magnetizer element, like poles of said first and second magnetizer elements being juxtapositioned;
- and
- sensor means positioned between the poles of said first magnetizer for detecting and discriminating between flaws on the inner surface and flaws on the outer surface of said specimen.
A magnetic inspection tool for detecting defects in small-diameter ferromagnetic tubular goods having inner and outer wall surfaces, comprising:
- a first magnetizer element means for establishing a magnetic flux in a portion of the wall of a specimen under inspection;
- a second magnetizer means for magnetically bottling said magnetic flux field within a desired volumetric region within said wall;
- sensor means for detecting and discriminating between defects occurring on said inner and outer wall surfaces;
- said second magnetizer element means including a central permanently magnetized core that is terminated at each end by a prehensile pole piece;
- means for resiliently supporting said first magnetizer element from said central core;
- said sensor means including a flux leakage sensor means and a sensor means for measuring the reluctance across the bottled magnetic flux field, both said sensor means being mounted adjacent said first magnetizer means on said first magnetizer supporting means;
- and
- means for radially expanding said means for resiliently supporting against the inner surface of said specimen.
Dependencies are inferred from the claim text.