A magnetic method of wire-rupture detection in steel cables

Lifting ferromagnetic wire cables are subjected to wear during service. The number and distribution of ruptures in the wire and the rupture-accumulation rate are criteria of cable conditions. Wires at the surface layer are more often subjected to rupture, as are wires at the interfaces of exterior strands and the steel core in the strand ropes. A magnetic method is used to detect wire ruptures; the method is implemented using defectoscopes based on permanent magnets. The controlled section of the cable between magnetic poles is magnetized up to induction of technical saturation. A magnetic stray field is formed at a site of wire rupture above cable surface. The presence of the stray field and, hence, of wire rupture can be registered by Hall sensors or induction sensors (measuring coils), which are placed near the cable surface at measuring units. The stray field is characterized by low intensity and weak localization and is unusable for experimental studies, which impedes the design of effective measuring systems. Analysis of the metrological characteristics of defectoscopes from the majority of producers shows their low sensitivity to wire ruptures. This paper has shown that the parameters can be optimized of a measuring unit with an inductive sensor to increase the reliability of wire-rupture detection in steel cables based on mathematical simulation of the stray field. Requirements that allow one to optimize the parameters of measuring units have been formulated.