Based on the introduction and analysis of difficulties encountered during technical inspection of the wire rope of a winding mine hoist (WMH) working at high speed, an open-loop permanent magnet magnetizer was used to simulate and analyze the effect of the structural dimensions of this magnetizer on the magnetic leakage field of a defect, and the results of the simulation analysis were initially verified by experiments. Additionally, in order to keep the axial position of the probe in line with the axial position of the wire rope, a rocker arm was proposed to act in coordination with a motor to drive the clutching open and closed probe, thereby creating an on-line nondestructive testing device to float and track the movement of the wire rope in different directions. Finally, the device was applied to testing of WMH wire rope on site to validate the effectiveness and feasibility of the method.

Wire rope will have defects such as local faults (LF) and loss of metal area (LMA) during the long-term using process. The nondestructive testing method of magnetic flux leakage (MFL) has been widely used in wire rope defect detection. Currently, the detecting distance between magnetic sensors and wire rope with the MFL method is relatively small (2–5 mm). Considering the inner surface of the sensor head is close to the wire rope, it quickly leads to the sensor head scraping off the surface oil of the wire rope or being stuck by a cut wire in the course of MFL detection. Therefore, it is challenging to realize the sensor with MFL detection of wire rope obtaining the weak signal at a large lift-off (>30 mm). This study used finite element analysis to verify if the MFL signal exists at the large lift-off (>30 mm). Meanwhile, the sensor head was improved using an open magnetizer to make the wire rope reach saturation and excite enough magnetic leakage field. By combining magnetic sensing and coupling and a weak analog signal processing method, not only was the signal effectively detected, but also the signal-to-noise ratio (SNR) was improved. Finally, experiments verify the feasibility of detecting defects at a large distance. The method also has been applied in the high-speed detection of wire rope, which can detect broken wire of 1 mm diameter.