A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg,in partial fulfilment of the requirements for the degree of Master of Science in Engineering (Mechanical Engineering), June 2017 / This research report describes the creation of a unique experimental facility for investigating localised stresses that can develop in conveyor belting during operation. High localised stresses can cause premature failure of conveyor belts, requiring expensive replacement. A key objective of carrying out research in this field is to gain a fundamental understanding of the stress that develops in various types of conveyor belting as it crosses over idler rollers. An experimental facility was developed that will be able to measure the stress and the deformation for different types of belting, such as solid woven/PVC and ply belting, with different belt classes. Particular attention was given to the various effects at the junction point caused by different idler configurations. Idler arrangements are configurable in the 24m–long test facility for inline, offset and belt-friendly types. Belt stresses at the idler junctions of these configurations are measured by applying strain gauges and load cells. The offset distance can be varied to determine the effect this has on the developing idler junction stress. This will allow comparison of the stresses as the class of belt increases, for each type of belt. The value of doing so is to determine the effect that the weft strength or stiffness has as the belt is forced into the idler junction. The test facility that was designed and built was shown to meet the requirements of the project. The instruments were calibrated to an acceptable uncertainty. The test facility can handle the full range of planned tests in terms of the design strength and is modular enough to handle a variety of other research initiatives. This establishment of a large, specialised experimental facility constitutes the first phase of an ongoing research programme into improving the design standards for belt conveyor systems / CK2018

Thesis (M.S.)--Ohio State University, 1977. / Includes bibliographical references (leaves 153-155). Available online via OhioLINK's ETD Center

Thesis (M. Eng.)(Electrical)--University of Pretoria, 2005. / Summaries in English and Afrikaans. Includes bibliographical references. Available on the Internet via the World Wide Web.

Call number: LD2668 .T4 1978 W91 / Master of Science

An experimental study of the drying of sand using an induction heated double-screw conveyor (screw shaft radius 0.0381 m, blade radius 0.0883 m, thread pitch 0.0869 m, heated length 1.96 m) is presented. The main aim was to improve the understanding of the operating characteristics of the dryer and obtain data for testing and refining future mathematical models. In the drying tests, power to the induction coils was controlled to obtain uniform screw shaft temperatures between 150 to 250°C. The angular rotation speed of the screws ranged between 2.5 to 15 rpm; and inlet moisture content (mass fraction of water) was varied between 0.1 to 10 %. The sand used had a mean effective diameter of 0.38 mm, particle density of 2743.7 kg/m3, and uncompacted dry bulk density of 1508.2 kg/m3. The results of sand characterization tests, conveying tests without induction heating, and drying tests are presented and discussed.

M.Ing. (Engineering Management) / In a tender bid to energy and chemical company Sasol, a request to offer a technical solution for a two-flight overland conveyor system whose function is to transport coal from a 15 000 tonne bunker into an external stockpile storage facility in the plant was made. This conveyor consisted of two conveyor flight sections of lengths 18 423m and 8 537m each. The prospect of combining the two flights of conveyors to form one, super-efficient conveyor structure with additional cost saving benefits was identified. It was found that this occurrence was not unique to the individual project as other researching engineers have been faced with similar problems before [18]. This then lead the researcher into believing that there could be some advantage in investigating the possible benefits to the overall cost, maintainability and scheduling of the fabrication and erection activities for the entire project of combining the multiple flight conveyors into a single-flight conveyor. It is also the conviction of the researcher that the achieved outcomes will prove beneficial to the bulk materials handling industry as a whole. The problem is traditionally short, multiple flight conveyors have always been used for performing the function of transporting bulk material from one location in a mining plant to another hence; long, single-flight overland conveyors of lengths exceeding 26 km have not been commonly installed. In this dissertation the possibility of employing a single-flight overland as opposed to a two-flight conveyor in the Sasol Impumelelo coal plant is investigated. This is done against the work of other researchers who have conducted similar studies in the field as well as by utilizing project-specific data using applicable industry standards as well as Engineering Management course theory. By employing actual project procurement and engineering design data; the investigation is done by calculating and comparing the individual capital and operational costs that encompass the total cost of ownership (TCO) for both conveyor systems as well as the two systems’ reliability, availability and maintainability to establish each system’s complete life cycle costs. It is the opinion of the researcher that the investigation method is valid as it is in line with the guidelines given by The Miami University of Ohio [24] as well as J Hanek [25] and thus provides the researcher with a plausible technique for establishing which between the single-flight overland conveyor and two-flight overland conveyor configurations is overall the more superior system to install. It was found that even though its initial capital and operational costs are higher; the single-flight conveyor system is more reliable, readily available and cheaper to run and sustain over the 30 year expected life-span of the plant. It also is less labour intensive to perform maintenance on, yields less material degradation and results in less material spillage because of the elimination of additional transfer points and transfer towers. These results can be taken as valid on a global scale, for any mining plant, not restricted to any specific material as they are not subject to South African temperature, altitude or seismic conditions nor are they constrained to the type of bulk material being mined.

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Magíster en Minería / La minería a cielo abierto se caracteriza por sus grandes volúmenes de producción, los cuales hacen posible la operación de minas con bajas leyes, altos costos de inversión, crecientes costos operativos y la reducción de la productividad debido a la profundidad de los rajos; a todo esto se suma la complejidad para administrar grandes flotas de camiones de alto tonelaje. Es por ello que en la actualidad se hace determinante el uso de tecnologías correctas en las actividades de mayor incidencia en el costo mina. El principal objetivo de este trabajo es el desarrollo de una metodología adaptable al mundo minero polimetálico usando In-Pit Crushing and Conveyors (IPCC), ya que ofrece diversas configuraciones para su aplicabilidad, convirtiéndola en una opción atractiva. Se inició con un estudio pormenorizado del transporte de materiales, sintetizando sus variables más influyentes, como es el costo del combustible. Posteriormente se avaluó la evolución del costo mina en función de la profundidad. Ésta fue desarrollada en base a simulación del sistema tradicional de carguío y transporte, considerando el consumo de combustible para la flota de camiones. Luego para el modelamiento del costo mina se partió de la premisa que el costo de combustible representa un 25% del costo mina, para proseguir con la optimización, agentamiento y evaluación de cada escenario. Dentro de los resultados obtenidos se puede apreciar variaciones en el material a remover tanto en mineral como en desmonte. El costo de capital mayor del IPCC es abatido por la vida útil del mismo y los menores costos operativos asociados a su uso. Es por ello que en el caso de los chancadores semi-móviles y especialmente en los semi-fijos es de suma importancia su ubicación óptima dentro del yacimiento y no solo a partir de una evaluación de costos, sino también en base a una evaluación de VAN. Según sea el caso hay la posibilidad de un reemplazo total de la flota de camiones por las correas transportadoras y los chancadores móviles. Todo esto conduce a una reducción significativa del costo mina según la configuración del IPCC, también queda susceptible a la coyuntura actual de precios del petróleo, la fuente y suministro energético del país. Finalizamos recomendando el uso de los gráficos como referencia para evaluaciones relacionadas al uso de esta metodología, además de realizar estudios más profundos.

M.Phil. / Pulleys are critical items in belt conveyors. Their primary role is to drive large mining conveyor systems, facilitating the transportation of ore over extensive distances, both in South Africa and abroad. The effect of the manufacturing process (with specific emphasis on the induced residual stresses) on the fatigue performance of conveyor pulleys is herein investigated and reported. A pre-selected pulley was chosen based on size, suitable for experimental work as well as practical specifications. The static and fatigue performance of the pulley were investigated both with the current design criteria as well as Finite Element Analysis, with comparisons drawn. The material data for the Finite Element Models was obtained experimentally with tensile tests of the SANS 1431 350 WA plate. The magnitude of the residual stresses were obtained experimentally by using the incremental hole-drilling technique for non-uniform residual stresses. The method was verified by comparison with the Finite Element Analysis results for the non-linear material analysis of the roll-bending of the shell. The fatigue analysis revealed that the stress ranges of interest for the pulley were below the non-propagating stress range, and hence theoretically infinite fatigue life would be possible under constant amplitude conditions. The operational fatigue life required for the pulley would be possible, when considering the latest S-N curve for "very high cycle fatigue". The stress intensity factors for the weld details were also below the threshold value and hence crack growth should not occur, upon crack initiation. A new design criteria was proposed for the fatigue analysis considering either fatigue assessment standards or fracture mechanics for the assessment of the butt-welds. This investigation showed that the manufacturing-induced residual stresses may play a significant role in the fatigue life of a pulley. The fatigue strength of a machined stressrelieved joint is higher if the stress range is partly compressive. The fatigue strength of a machined as-welded joint is higher than estimated by the fatigue classifications. This is due to residual stress relaxation that occurs at the weld toe because of yielding and hence a subsequent reduction and redistribution of the residual stresses. This reduction in the mean stress level, with a stress range that is partly compressive, would mean an increase in the fatigue strength of the joint. This would in conclusion result in similar fatigue strengths for a stress-relieved and an aswelded joint. This would additionally depend on the extent of the reduction of the residual stress in the as-welded joint. Recommendations were suggested for further experimental and numerical work for both the T-bottom and Turbine-type pulleys.