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By D. A. Fenton

The structural design of large grinding mills, with reference to shell-mounted bearings by D. A. FENTON*, P. Eng. (Visitor) The paper outlines the advantages of shell-mounted grinding mills over mills having a conventional trunnionsupported shell. The growing use of larger mills in the past decade has led to a significant number of mechanical and structural failures, the most common being those at the junction of the head and the shell. Larger mill diameters favour the use of shell-mounted bearings. The elimination of castings, which have an inherent weakness to fracture, makes the shell-supported mill lighter and stronger than a conventional mill of the same shell thickness.

Jan 9, 1976

By R. Watts, R. A. Laybourne

This paper describes how a 'mined out' coalfield is being mined successfully by opencast methods. The coalfield is that at New Vaal Colliery, which is situated in the Vereeniging-Vanderbijlpark-Sasolburg industrial complex. Al three coal seams at New Vaal had been mined previously, when the better-quality coal had been removed. The coal-preparation plant at New Vaal, which is also described, supplies coal to the 3600 MW Lethabo Power Station. The Colliery has been designed to supply 600 million sales tons of coal over its forty-year life.

Jan 1, 1990

By M. S. M. Aljuhani

In this paper, one of the human factors that affect productivity in an underground gold mine in Saudi Arabia was investigated and analysed for the purpose of improving productivity. The human factor that was investigated is labour utilization and labour productivity. In the selected mine, labourer?s performances were measured carefully. It was found that in this mine, workers spend only 65% of the shift time in a productive work, and they spend 35% of the shift time in non-productive activities. As a result, recommendations were presented to enhance productivity in the selected underground gold mine by enhancing labour utilization.

Jan 1, 2002

By H. Yavuz

Closed form solutions assume opening shape to be circular to simplify the calculation of the ground response curve for the design of underground openings. However, in mining and civil engineering works, non-circular openings are commonly excavated. Therefore, there is a need to estimate the ground response curve for such openings. In this respect, a simple model for circular, arch and rectangular shape underground openings subject to a hydrostatic stress field is the aim of this study. A comprehensive numerical modelling, using the finite difference method, based on numerical modelling code FLAC version 4.0, was carried out. In addition to shape of an opening, the effect of rock mass strength, opening size, in situ stress on strain (tunnel deformation to tunnel radius) of the opening in response to applied support pressures was investigated parametrically by developing models for each specific condition. The strain results for each excavation shape obtained from this large number of models against the normalized strength of rock mass and internal support pressure with in situ stress magnitude were evaluated by multiple regression analysis. As a result, a model that was well correlated to data was developed for an overall estimate of the ground response curve depending on relevant effecting parameters. The regression coefficients of the model were given for estimating both roof and sidewall response curve of each excavation shape. The model was verified by statistical tests and by an analytical solution. Diagrams were also established to highlight the influence of relevant parameters and to estimate the support pressure for a stable opening staying within the acceptable limits of strain. Strains occurring in a rectangular opening are found to be larger than those in the arch and circular openings for the other fixed parameters. In the mean time, larger strains occur around an arch shape opening than a circular opening.

Jan 1, 2006

By M. A. Roberts

Oebswana's Jwaneng Mine (south-central Botswana) is the richest diamond mine? in the world and has been contributing substantial revenue to Botswana since the mine started operating in 1982. The resource consists of 3 separate volcanic pipes/vents namely North, South and Centre pipes (2 additional small kimberlite bodies have also been intersected within the mining pit) which erupted through Transvaal strata and the overlying Karoo sediments -245 million years ago. Although earlier drilling and geophysical surveys suggest that the 3 pipes extend to depths greater than 1 km below the surface, the resource is only at an indicated level of confidence to a depth of 400m, and mining activities will start exploiting the inferred resource material below 400m in 2014.

Jan 1, 2010

By R. J. Kendall

As we enter the new millennium, the South African mining industry has to ensure that it becomes more competitive if it is to survive in the ever more demanding global environment. Traditionally, mechanization in narrow stopes has been limited to the use of scraper winches, and numerous mechanization attempts have been restricted to pilot projects operated on an extremely limited scale (with varying degrees of success). The benefits of hydropower are well documented, and Northam Platinum has shown these benefits to be achievable on a mine-wide basis. However, the equipment originally developed for hydropower systems has followed the traditional labour-intensive approach commonly used in deep level narrow stoping operations. The problems experienced with the hydropower system are discussed and the rationale for developing alternate technologies is explored. The hydropower system has shown to be a versatile powering medium which can be harnessed for a diversity of uses. It (hydropower) enables the mining engineer to change traditional paradigms and to design an entirely new approach for optimizing the mining operation based on explosive techniques. The system developed for Northam consists of the following: ?Purpose-built stope drill rig operated off the hydropower system with special features to ensure accurate drilling patterns throughout the length of the blast hole ?Purpose-built high rate cleaning system for rapid transfer of fractured ore to the stope orepass ?Redesigned stope layout to facilitate in-stope water control and to recover fines from the run-off water ?Purpose-built drill rig for rapid establishment of reef raises and advanced strike gullies ?Purpose-built drill rig for flat end development. On both types of development end rig, emphasis is placed on ensuring accurate drilling patterns throughout the length of the hole to maximize linear advance per blast. The paper discusses the implementation of the Northam system on a large scale as well as current initiatives to further improve on the efficiencies of mining operations. It concludes by emphasizing that mechanized hydropowered stope technologies are in their infancy and thus offer unlimited scope in progressing beyond today?s paradigms to present as yet unthought of solutions for optimizing deep level ore extraction.

Jan 1, 2000

By A. L. Hinde, P. J. D. Lloyd, A. R. Atkins, J. G. MacKay

The control of milling circuits by A. R. ATKINS, M.Se. (Elee. Eng.) (Visitor), A. L. HINDE, S.Se., Ph.D. (London) (Visitor), P. J. D. LLOYD, S.Se. (Chem. Eng.), Ph.D. (Cape) (Fellow) and J. G. MACKA Y, S.Se. (Chem. Eng.) (Visitor). The general behaviour of mills is described in an attempt to find a control philosophy that will permit milling circuits to produce a constant particle size. Although the experimental work has been confined to a single section of the milling circuit of one mine, it is felt that the findings are applicable to other milling circuits.

Jan 6, 1974

By J. N. Van der Merwe, M. Mathey

"The South African squat coal pillar strength formula, developed by researchers from the Chamber of Mines Research Organization in the 1980s, predicts an exponential increase in coal pillar strength once a critical width-to-height ratio of 5 is exceeded. The arguments that have been proposed in favour of this formula are discussed critically in this paper.Field experience with squat pillars in the USA and evidence from published physical, analytical, and numerical model pillar studies corroborate the fact that a squat effect is unlikely to occur in coal pillars at width-to-height ratios less than 10. Furthermore, an exponential increase in peak strength of coal pillars does not exist. An alternative design criterion for squat pillars in South Africa is therefore suggested. IntroductionFive decades of coal pillar research in South Africa have produced a wealth of information on the mechanisms contributing to the strength and failure of in-situ coal pillars and accompanying phenomena. The relevant knowledge was sourced from, and for, a South African coal mining environment that remained largely unchanged in the second half of the 20th century. The depth of mining seldom exceeded 250 m, with mined seam thicknesses averaging 3 m and typical pillar width-to-height ratios (w/h) of 3–4.It is therefore not surprising that comparatively little research has been directed at the prediction of coal pillar performance in deeper deposits, where squat pillars of larger width-to-height ratios will be required to support the overlying strata. However, a thorough understanding of squat pillar performance will be necessary should the remaining deep coal deposits of the country be extracted in future, for instance in the Waterberg or Ermelo coalfields.A squat coal pillar strength formula has already been proposed in South Africa. The origin of this formula will be discussed in some detail in the following sections and its appropriateness will be critically reviewed against a great amount of evidence from relevant squat coal pillar research conducted internationally."

Jan 1, 2016

n interesting situation arose last week when two Vaal River residents wrote to me (and a third telephoned) giving me details of how Sasol wanted to develop an open-cast coal mine on the south bank of the Vaal, just upstream of the Barrage. This is agricultural land and is across the river from Millionaire?s Row, where a number of wealthy people have built river-side mansions. The mine would be hidden by a 30 m-high (10 storeys) earth wall set 300 m back from the edge of the river. It could operate 24 hours a day.

Jan 1, 1996

By M. Krasowska, W. Skinner, R. K. Asamoah

Understanding chemical interactions at solid-liquid interfaces have played a pivotal role in improving mineral flotation performance, increasing the rate of mineral crystallisation and profitable leaching of valued minerals and metals. This paper highlights gold leaching with links to surface and interfacial chemical processes occurring, and opportunities to maximise extraction while reducing usage of more recent scarce resources. From the review, there is a significant link between surface and interfacial processes and gold leaching performance. Evidently, gold leaching kinetics could be increased by changing leaching conditions, including manipulating the surface and interfacial interactions. Control of surface and interfaces during gold extraction could enhance rapid, smarter gold extraction and mitigate formation of passivation layers. Keywords: Surface and interfaces, refractory ores and concentrates, gold leaching, reaction mechanism and kinetics

Jan 1, 2020

By M. Le Roux

Fine coal (-500 µm) is notoriously difficult to dewater. It is not uncommon for a dewatered product to have a moisture content as high as 30 per cent after vacuum filtration. This poses several handling and financial problems to such an extent that a lot of fine coal is discarded onto slurry waste ponds. A novel way of dewatering fine coal was developed at North-West University. It entails deliberately damaging the filter cake during dewatering to allow for an increased flow of air through the cake at the expense of the applied pressure differential. This method resulted in an average improvement in final cake moisture of between 3 per cent and 5 percent when executed in the laboratory under controlled conditions. A device was designed that could be fitted onto existing belt filters that would damage the filter cake as it passes by. This device was tested on a vacuum belt filter installation at a coal beneficiation operation in the Waterberg coal field in South Africa. The results showed a 3 per cent reduction in final moisture of the cake, proving the validity of the method at full industrial scale.

Jan 1, 2012

By M. Le Roux

Fine coal (-500 µm) is notoriously difficult to dewater. It is not uncommon for a dewatered product to have a moisture content as high as 30 per cent after vacuum filtration. This poses several handling and financial problems to such an extent that a lot of fine coal is discarded onto slurry waste ponds. A novel way of dewatering fine coal was developed at North-West University. It entails deliberately damaging the filter cake during dewatering to allow for an increased flow of air through the cake at the expense of the applied pressure differential. This method resulted in an average improvement in final cake moisture of between 3 per cent and 5 percent when executed in the laboratory under controlled conditions. A device was designed that could be fitted onto existing belt filters that would damage the filter cake as it passes by. This device was tested on a vacuum belt filter installation at a coal beneficiation operation in the Waterberg coal field in South Africa. The results showed a 3 per cent reduction in final moisture of the cake, proving the validity of the method at full industrial scale.

Jan 1, 2012

By H Möller

The purpose of this paper is to give an overview of the corrosion behaviour of steel in seawater. It is shown that the corrosion products (oxy-hydroxides and calcareous deposits) that are formed during corrosion in seawater have a significant effect on the corrosion behaviour of steel. The chemical composition of the steel determines how protective the oxy-hydroxide corrosion product is. The composition of the seawater influences the nature of the calcareous deposits. This needs to be considered when artificial solutions are used to simulate the corrosion behaviour of steel in seawater. A 3.5% NaCl solution is used frequently for this purpose, but because no calcareous deposits can be formed in this solution, erroneous results in terms of corrosion rates are obtained. The more complex ASTM D1141 artificial solution can be used to include the effects of ions other than Na+ and Cl- in synthetic seawaters. The importance of these other ions on the formation of calcareous deposits is discussed. Keywords: Steel, corrosion, seawater, calcareous deposits, oxy-hydroxides

Jan 1, 2006

By J. C. Taylor

The Rhodax inertial cone grinder, designed by France?s FCB Group Fives, is the result of three years, theoretical and mechanical research in the field of compression grinding by the research staff of FCB?s CRM minerals research centre. A number of potential uses have been assessed and will be discussed in the paper. The crusher is an inertial grinder that works on the pressurized bed fragmentation principle. The fragmentation force is caused by the rotation of unbalanced masses rather than by an eccentric mass, as is the case in a conventional crusher. This makes it possible to achieve very high reduction ratios. By controlling the speed of rotation of the unbalanced masses, the grinding force can be modified, thus changing the product size distribution. The paper describes the machine layout, operating principles, control parameters and will briefly describe the results obtained on reef, waste and ROM reject pebbles. Some comparisons are made with conventional crushing.

Jan 1, 1998

By K. Esmeli, A. Ozkan

The enhancement of shear flocculation of a galena suspension by ultrasound in the presence of sodium isopropyl xanthate and potassium ethyl xanthate was investigated by studying the effects of surfactant concentration on flocculation efficiency, contact angle, and zeta potential. Strong flocculation was obtained under alkaline conditions (pH > 9) and a high ultrasound power level (150 W). Although the ultrasonic treatment increased the negativity of the zeta potential of the galena particles, this did not decrease the flocculation efficiency, thereby showing that the hydrophobic interactions between the particle were stronger than the electrical double-layer repulsion resulting from xanthate adsorption. The findings indicate that the ultrasonic treatment promoted the adsorption of surfactants onto the mineral surfaces.

Jul 5, 2023

By P. C. Schutte

Ergonomics is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance. Despite the fact that the application of ergonomics principles can make a major contribution to the management of significant occupational safety and health risks, ergonomics is currently applied on a limited scale in the South African mining industry. The objective of this paper is to provide a perspective of ergonomics, the main aim being to create a point of departure for the development of strategic objectives to enhance existing health and safety initiatives through the application of sound ergonomics principles. Two of the major consequences of poor ergonomics, namely work-related musculoskeletal disorders and worker fatigue, and possible means of introducing ergonomics into the South African mining industry, are discussed.

Jan 1, 2005

Council for 2003/2004 President T.R. Stacey President-elect F. M. G. Egerton Vice-presidents Senior W. H. van Niekerk Junior R.P.H. Willis Immediate Past-president S.J. Ramokgopa Honorary Treasurer J.A. Cruise

Jan 1, 2004

Council for 2001/2002 President A.A.B. Douglas President-elect S.J. Ramokgopa Vice-presidents Senior F.M.G. Egerton Junior Prof. T.R. Stacey Immediate Past-president Dr L.A. Cramer Honorary Treasurer J.A. Cruise

Jan 1, 2002

Council for 2002/2003 President S.J. Ramokgopa President-elect T.R. Stacey Vice-presidents Senior F.M.G. Egerton Junior W.H. van Niekerk Immediate Past-president A.A.B. Douglas Honorary Treasurer J.A. Cruise

Jan 1, 2003

By F. Sawyerr

A bubble population balance model is proposed for the prediction of Sauter mean bubble diameters in mechanical flotation cells. In the model, the flotation cell is treated as two separate, statistically homogeneous zones?the impeller zone, and the bulk tank zone. Balance functions for the rates of bubble breakage, coalescence, recirculation and inlet-outlet events are proposed based on classical chemical engineering research in two- and three-phase fluid mixing systems. An initial simulation of the population balance model shows trends in bubble size distributions comparable to measured distributions in industrial mechanical flotation cells.

Jan 1, 1998