Design methodology for the Levelok conveyance arresting system used in the mining industry

Abstract

Proceeds from gold and diamond mining operations make a significant contribution to the South African economy, and therefore deep-level mining has become widely practiced throughout the country. Six of the ten deepest mines in the world are located on the South African treasure route, where the extraordinary depths of vertical hoisting present a range of challenges, with rope stretch being one of the more common challenges. The Levelok conveyance arresting system is a solution that secures the positioning of a conveyance next to a shaft station to counter the problems associated with hoisting rope stretch. The concept behind the Levelok system has numerous potential advantages, but unfortunately, the system historically did not yet fully deliver on the promises of these advantages. The objective of the study was to address the shortcomings of the system, by studying and evaluating the Levelok Systems in the current industry as well as developing a design and evaluation methodology. The findings can be used to predict if the Levelok hydraulic power pack would be suitable for the customer requirements before it is approved for delivery. To achieve these main objectives, the research presented in this dissertation highlights some of the complexities associated with the Levelok systems. The most complex apparatus of these systems is the decompression cycle assembly. Different arrangements of this apparatus and how the flow of hydraulic fluid through the narrow annulus between its spindle and seat affects the control output were explained and studied. Using the knowledge obtained, a new decompression cycle arrangement was designed. This new invention has been patented in WJ Engineering's name with patent reference number PA165722/ZA and was the result of the application of the design methodology that was followed for the MK7, MK7s & MK7 Elec Levelok cage systems. The methodology for the design of a pneumatic actuated system and 24V DC operated system has been outlined in this dissertation. The different designed systems of the MK7 range were tested and analysed with a constructed Levelok Power pack Decompression Cycle Conveyance Displacement Mathematical Prediction Model. All results were found to satisfy all system requirements and delivered a constant output for different tests completed using the test benches at WJ Engineering (PTY) LTD and on-site tests in vertical mine shafts. With the confirmed, tested concentric annulus size of 0.07 - 0.08 mm in the MK7 decompression cycle arrangement, the decompression cycle pressure curve of the Levelok system was rectified. Thus, the control output of the Levelok system, of obtaining the required stable "slide" of the arrested conveyance after clamp release, was improved. The result of this dissertation addressed all system shortcomings and all objectives of the study.