Scielo RSS <![CDATA[Journal of the Southern African Institute of Mining and Metallurgy]]> http://www.scielo.org.za/rss.php?pid=0038-223X20090004&lang=en vol. 109 num. 4 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Surface drainage around the Venetia pit</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2009000400001&lng=en&nrm=iso&tlng=en Venetia is an open pit, truck and shovel operation owned by De Beers South Africa and situated in the northern part of South Africa in the Limpopo province. The kimberlite body was discovered in 1980 and full production started in 1992. The mine is currently mining the fourth cut of the open pit and plans are in place to ake the mine underground by 2014 employing a block cave mining method. This project was initiated because of a lack of a drainage system that prevents stormwater from reporting into the open pit during the rainy seasons. The project had been attempted before without much success and the problem in question is escalated by an ever expanding pit. <![CDATA[<b>Investigation of factors influencing the attrition breakage of coal</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2009000400002&lng=en&nrm=iso&tlng=en The presence of fines (particles smaller than 6 mm in diameter) causes hydrodynamic problems in gasifiers and therefore it is of great importance to minimize the amount of fine coal in the feed. This serves as motivation for understanding coal's breakage mechanisms, which could lead to the ability to predict the generation of fines. The aim of this project was to simulate the pulsating effect of the conveyor belt in order to investigate factors influencing the breakage. Results indicated that an increased initial particle size had an increasing effect in the amount of fines generated. Weathering had an insignificant effect on the breakage of coal. To conclude, a breakage model was developed to describe the rate of breakage out of the top size when a combination of two breakage modes is present. <![CDATA[<b>A critical comparison between a compressed air driven rocker arm shovel and a track-bound non-throw loader</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2009000400003&lng=en&nrm=iso&tlng=en This report compares the compressed air driven rocker shovel to the newly developed Warthog Non-throw development end loader. The two machines were compared on aspects such as safety, loading potential, energy efficiency and costs. The objectives of the comparison were to determine whether or not the replacement of the rocker shovel with the Warthog will be operationally and financially justifiable. The results from this study were obtained from underground observations and time studies on the machines, as well as consultations and data collection at the shaft and suppliers. This paper compares only the Warthog loader to the Trident 215 rocker shovel used at Anglo Platinum's Brakspruit shaft and does not compare the other models of rocker shovels, which are fundamentally the same but will have different loading potentials and specifications. Cleaning times for the rocker shovel are based on underground observations at Brakspruit shaft. These times can be influenced by factors such as blasting practices, compressed air pressure and operator experience and skill. For this reason the times will most likely vary at different shafts. The Warthog cleaning times are based on manufacturer specifications and results from trial stages and therefore further work is required to confirm cleaning times achieved. The findings from this study indicate that the replacement of the rocker shovel with the Warthog will improve the safety, production, cost and energy efficiency of development end cleaning operations. The Warthog also complements the system of rapid face advance achieved by the Mantis drill rigs, by achieving faster cleaning rates to handle the longer advances and larger volume of rock. In this way the Warthog benefits the overall efficiency of flat end development. <![CDATA[<b>Optimization of the loading and hauling fleet at Mamatwan open pit mine</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2009000400004&lng=en&nrm=iso&tlng=en The purpose of the study was to investigate the factors which affect the performance of the loading and hauling fleet and also find possible solutions to eliminate these factors, so that the daily tonnages required could be produced .This is due to the high demand of manganese required by clients. The investigation strongly focuses on the performances of the three 777D Caterpillar trucks and the R984 C Liebherr Litronic Hydraulic Excavator. In the content of the study, these machines are used to remove and move the low grade manganese (also known as the top cut overburden) in order to expose the high grade manganese from north pit to dump 4. The objectives of the project were to determine the actual performance of the loading and hauling fleet per shift, compare the actual and the theoretical performance and identify areas that need to be improved. To achieve the goals set for the project, a number of activities were carried out. e Perform a time study to compare the performance of the loading and hauling fleet with the manufacturer specifications e Match the equipments analysis for Loading and hauling e Road conditions analysis e Rolling resistance and Road Gradients analysis e Operating cost analysis. <![CDATA[<b>Quest for 'effective pack' support</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2009000400005&lng=en&nrm=iso&tlng=en Following on the design of good mining layouts and regional support systems, and the implementation of sound strata control practices, stope support is the ultimate strategy to combat the hazards of rockfalls and rockbursts. The primary function of stope support in intermediate and deep level mines is to stabilize the rock mass immediately surrounding stoping excavations, that is, the zone of fractured rock which behaves inelastically around stopes. Support design is a process resulting in a support system which is both practical and meets or exceeds by a factor of safety the requirements for a particular geotechnical environment. The aim of this project was to design a support system, which accommodates the factors of rockfalls and rockbursts. The pack support unit must be easily handled, less costly and can be used in stopes without any significant convergence. The project tested the structural stability of packs to their expected deformation, in order to design a height to width ratio for stopes where little convergence is expected. <![CDATA[<b>Assessing the effects of the cone force ratio on the performance of hydrocyclones</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2009000400006&lng=en&nrm=iso&tlng=en Hydrocyclones are a common feature in almost all mining operations in the world, serving mainly as classifiers. Some of their advantages include low capital costs, low space requirements and their ability to reduce residence time in closed circuit grinding processes. Although an extensive body of literature exists for hydrocyclones, these devices are still inherently inefficient, and more research is currently being undertaken, particularly in the field of modelling. In the vast body of hydrocyclone literature published so far, there has been little or no effort devoted to analysing the effect of the cone force ratio on the performance of ydrocyclones. The cone force ratio is defined as the ratio of the spigot to the vortex finder diameter (Shah, 2005). In this study a total of 44 tests was carried out in a custom-built rig at the University of Cape Town. These tests were aimed at evaluating the effect of the cone force ratio on the performance of a small diameter hydrocyclone. The cut size and water split were used as the criterion for evaluating the performance of the ydrocyclone. Results from the tests showed that the cut size decreased with an increase in the cone force ratio. The cut size also appeared to decrease as the calculated locus of zero vertical velocity (LZVV) shifted inwards. The water recovery to the underflow appeared to increase with an increase in the cone force ratio. The effect on the cut size of adjusting the cone force ratio was found to be higher for a coarser feed than it was for a finer feed. <![CDATA[<b>Technical skills - a major strategic issue</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2009000400007&lng=en&nrm=iso&tlng=en A shortage of technical skills in all areas of the mining industry is being experienced worldwide. This has significant consequences for design, operations, productivity and safety and, therefore, needs to be seriously addressed, both in the short and longer term. It is therefore both a strategic and a tactical issue. Importantly, however, since mining is a long-term business, the shortage of skills must be dealt with from a strategic point of view to ensure the supply of the necessary skills for future mining. This paper will deal specifically with the provision of high level technical skills, that is, university graduates in mining engineering, and the outlook for the institutions that are currently producing such graduates. <![CDATA[<b>Age-hardening of the aluminium alloy EN 4017</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2009000400008&lng=en&nrm=iso&tlng=en A shortage of technical skills in all areas of the mining industry is being experienced worldwide. This has significant consequences for design, operations, productivity and safety and, therefore, needs to be seriously addressed, both in the short and longer term. It is therefore both a strategic and a tactical issue. Importantly, however, since mining is a long-term business, the shortage of skills must be dealt with from a strategic point of view to ensure the supply of the necessary skills for future mining. This paper will deal specifically with the provision of high level technical skills, that is, university graduates in mining engineering, and the outlook for the institutions that are currently producing such graduates.