Design and evaluation of a vibration ore flow restore machine

Abstract

Ore passes provide a low cost method for gravitational transport of broken ore and waste rock through long vertical distances to lower levels of an underground mine. A hang-up or blockage in an ore pass is undesirable as it may lead to loss of productivity and a heavy financial cost to restore flow. This study focuses on methods to restore the flow of ore after a blockage occurs, specifically by designing an ore flow restoring machine that use vibration and building a physical machine to test the design. Mathematical models were developed to analyse the design of the proposed ore flow restore machine. This was regarded necessary to investigate whether the ore flow restore machine is capable of unblocking a blockage in an ore pass. Two three-degree-of-freedom mathematical models were developed to predict the dynamic displacements, dynamic forces and system natural frequencies for the ore flow restore machine for different operating conditions. These mathematical models were implemented in computer programs. A Finite Element Analysis (FEA) approach was used to analyse whether the design was free of structural resonance. An FEA approach was also used to determine the dynamic material stresses of the design when operating with and without steel cables. The design was deemed acceptable to build and evaluate experimentally. The input parameters required for the computer programs were characterised. Different mathematical models were developed for characterisation of the machine rubber mount vertical and horizontal dynamic properties. Measured data served as inputs and references for these mathematical models. The axial stiffness of the steel cable combination was validated with in-situ measured data. The operating frequency of the machine was also characterised, as was the size of the sample rocks used for experimental evaluation. The unblocking of interlocking and cemented blockages was evaluated for two possible unblocking methods: steel cables and a hammer. The underlying three-degree-of-freedom mathematical models for the ore flow machine were experimentally validated. The predicted response, transmitted forces and natural frequencies were compared to the respective corresponding measured values. This was done for the stand-alone machine, where the steel cables were removed from the machine, and for the machine when the steel cables were caught in a blockage.