Articles techniques et présentations

Mine hoists are significant capital investments, so their efficient, safe, and reliable operation are of vital importance to mining companies. ABB delivers numerous drum hoisting systems to underground mines in China, South Africa, as well as to Poland. ABB mine hoists are one of the largest delivered systems covering main unit, motors, control systems, the ACS 6000 MV drives, breaks control system and related technical support. Two drum systems of diameter of 5.7 m provide payload of 45 t with average payload of 1530 tph. Although hoisting systems compromise several mechanical and electrical components with potential of failure and stopping production. ABB technology offers the concept of the hoist digitalization by implementing remote high-speed sensing and diagnostics combined with advanced FEM modelling using a state of art software, particularly in the design phase. However, there are increasing needs to define the dynamic behavior of individual components whose properties can be rapidly defined and improved over the running time. So, the COMSOL was selected for that purpose. By developing FEA models, engineers can evaluate stress levels, identify potential areas of concern, and optimize the design to ensure adequate strength and reliability and to avoid unplan downtimes caused by rope failure. The focus on friction hoists where multiple ropes are wound and moved by the drum. During the operation, hoisting ropes are used to lift the load while balancing ropes compensate the weight and provide stability. Frictions between the ropes and the sheaves or drums create the necessary traction for lifting or lowering the mining loads. The relative motion between the ropes is also critical for operation and safety of the equipment. Ropes tensions are directly reflected by the stresses in the respective sheaves. When the ropes exhibit similar tension and friction conditions at the contact zone, balanced tension among the ropes ensures the load is evenly distributed across all ropes. This prevents excessive stress on any individual rope and promotes uniform wear, extending the lifespan of the ropes. Unequal tension or friction can result in jerky movements, vibrations, or irregular load control. Well-maintained balance between the ropes in a multi-rope friction hoist system is not only crucial for efficient hoist operation but also serves as a reliable indicator of proper functioning hoisting system. Uneven load distribution can lead to localized stress concentrations resulting in the reduction of the ropes lifespan and increase of the risk of failure. The FEM calculations using COMSOL packages were compared with other prediction models and then validated experimentally in ZA mines.