Modern design of belt conveyors in the context of stability boundaries and chaos

Abstract

Belt conveying of bulk materials has evolved to the point where the demands of the modern mine to increase capacity is limited by the ability of engineers to design dynamically stable conveyors. Belt speed and width are two parameters that may be varied in the design to provide the required material flow rate. For certain values of belt speed, width and tension, unstable transverse belt vibration has been observed. Large-amplitude vibration may be so severe that the life of the supporting idler bearings is reduced significantly due to dynamic loads. Monitoring idlers for bearing failure in modern conveyors with lengths up to 20 km is practically difficult since there may be as many as 20000 idler sets. Chaotic transverse belt vibrations occur for certain levels of excitation, further complicating the prediction of bearing life. Before conveyor installation, an estimate of the stability boundaries for resonance-free operation is an essential precursor to failure-free conveyor operation. Nonlinear resonance phenomena such as belt flap is sensitive to initial conditions. The effects of chaotic vibrations on the predictability of design stability is reviewed using some examples of forced vibrations.