Modelling and design of a general purpose, vertical shaft conveyance, all level docking device

Abstract

Deep level mining is widely practised throughout South Africa, particularly in the gold sector, where the extraordinary depths of vertical hoisting present an array of challenges. The accurate and secure positioning of a conveyance next to a station has been and continues to be one of the unresolved challenges that have led to many serious injuries and equipment damage. The literature study presented in this dissertation highlights some of the complexities associated with properly docking a conveyance and investigates some current, proposed and similar systems to address the issue. From the study it was found that no satisfactory device existed prompting a systematic design of a conveyance arresting device capable of securing a conveyance in a vertical shaft at any level. Proper definition of the system requirements was obtained and summarised into 16 groups. The system requirements play an important role in the design process by setting the direction but also featuring in concept screening and evaluation. In order to generate concepts a variety of creativity inspiring techniques were employed facilitating a systematic search for a solution. Application of the techniques, Brainstorming, Synectics, TRIZ, 2500 Engineering Principles, Sourcebooks and a Morphological chart resulted in the synthesis of 9 concepts. Screening and evaluation was performed on these concepts and the most suitable concept identified. The proposed concept is a simple system where two sets of beams are extended into the shaft in order to have the conveyance settle onto the supporting shaft steelwork. Once the conveyance came to a rest on the steelwork a second set of beams are extended beneath the steelwork to positively lock the conveyance in position. This required the geometric design of the system to ensure adequate strength to satisfy a factor of safety of ten. Design decisions were made on the section properties of the clamp beam by comparing a solid section and a box section. A supporting frame is used to guide the beams, with consideration given to the most appropriate method of attaching this support frame to the conveyance. The first choice was to have the beams extend from the rear of the conveyance but due to the moments and forces involved the conveyance roof structure could not support this configuration. The support frame was instead affixed directly to the conveyance Transom. In order to support the findings of the conventional calculations performed on the system components the system was subjected to finite element analysis. The results obtained from the simulation corresponded well for the simple components and varied somewhat in the more complex shapes attributed to the assumptions made to ease the conventional calculations. Weight and reliability in a harsh shaft environment was identified as critical design parameters and motivated the use of exotic high strength materials. The high strength of the materials made is possible to design a system with practical dimensions of adequate strength supported by the conventional and modeled calculations. Even though high strength materials were used in the design the overall system weigh is dissatisfying. A potentially successful and practical device was designed but certain factors such as weight, cost, conveyance structure and infrastructure modifications threaten the implementation of the design. This dissertation sets a sound foundation for future development and the continued search for a practical simple solution to this age old challenge.