Multi-loop magnetisation method for detecting coal mine wire rope defects

Existing methods for detecting magnetic leakage signals from damaged wire ropes require axial saturation magnetisation and the accuracy of the detection equipment depends on the degree of saturation of the magnetisation. Moreover, owing to the special characteristics of the structure, diameter and operating environment of the wire rope, it is difficult to achieve the expected magnetisation effect. Consequently, in addition to other issues, the detection accuracy and versatility of the equipment are low. This study proposes a method based on spatial multi-dimensional orthogonal array loop magnetisation to detect coal mine wire rope defects. First, a sensor excitation structure model is developed. Then, a method for detecting the radial magnetic flux using permanent magnet arrays is analysed and the influence of the number of permanent magnet radial magnetic blocks on the magnetisation effect is studied. In addition, a wire rope detection method based on the principle of clustering is investigated and used to discuss the influence of the shape, structure and size of the sensor on the magnetisation effect. Finally, through laboratory experiments, the applicability of the test model and the proposed method are verified. The results show that the magnetisation effect is better and more cost-effective when the number of permanent magnet radial magnetic blocks is eight and that the proposed detection method can effectively identify damaged wire rope joints. Furthermore, the proposed equipment achieves a signal-tonoise ratio of 28 dB, thereby improving the reliability of damage detection.