METHOD AND DEVICE FOR DETECTION OF CROSS-CUT AREA VARIATIONS IN A STEEL CABLE

摘要

A method and apparatus is provided for electromagnetically testing an elongate object such as a wire rope for cross-sectional area variations. The elongate object is magnetized over adjacent sections in opposing directions along a longitudinal axis of the elongate object. Variations in axial magnetic flux, which have been observed to be coincident with variations in the cross-sectional area of an elongate object, are measured by using saddle coils which are positioned adjacent the magnetized sections of the elongate object and which detect variations in radial flux. The saddle coils are positioned to have first half circumferential windings located where the magnetic flux density in the elongate object is at a maximum value and second half circumferential windings located where the magnetic flux density in the object is zero.