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By R. M. Göktan

A theoretical comparison is made between point-attack and wedge-shaped picks in regard to their cutting efficiencies in coals having different strength characteristics. With specific energy as a criterion of cutting efficiency, it is shown that a mathematical expression can be derived for the assessment of the relative performances of these two groups of picks as a function of coal-strength parameters and pick-tip angle. The ratio of tensile to compressive strength of coal is found to play a significant role in the determination of relative cutting efficiencies, lower ratios favouring the use of point-attack picks.

Jan 1, 1992

Tests were carried out in a Hallimond microflotation cell and a Denver D12 cell on typical residue material from a gold mine in the Orange Free State (South Africa), in which 50 per cent of the kerogen was larger than 100 µm in size. Although kerogen is naturally hydrophobic, the observed unexpectedly poor flotation reponse may be due to occlusion of the kerogen by a slime coating and subsequent depression of the slime by guar gums. The recovery of gold from samples spiked with kerogen increased, with no significant reduction in grades, when a petroleum-based collector and tetrasodiumpyrophosphate (a dispersant) were used.

Jan 1, 1985

By G. M. Thain

Ancient Mining - The following three contributions were received for publication in addition to the preceding papers. 1. Ancient gold-mining sites in the Transvaal G. M. THAIN* Pre-European gold mining and working in South Africa is a tantalizing field for conjecture. Well over thousand sites have been identified in Rhodesia, but here we have had to reach double figures, judging by published accounts. Geologically, the Transvaal is less amenable primitive exploitation, but it difficult to reject the idea that the knowledge gained to the north did not have its influence south of the Limpopo.

Jan 1, 1974

By H. T. Kaiser, P. De Waal

The Alusaf aluminium smelter at Richards Bay by H. T. KAISER, B.Sc. (Pta), M.B.L. (Unisa) (Visitor) and P. DE WAAL, B.Sc., B.lng. (Mech.) (Stell.) (Visitor) A description is given of the aluminium smelter at Richards Bay, which operates on the Hall-Heroult electrolysis principle. The annual output of metal (average 99,7 per cent aluminium) is approximately 7S 000 tons. Since its commissioning in 1971, the plant has fulfilled South Africa's total demand for low-alloy rolling slabs, extrusion billets, remelt ingots, and electrical conductor rod. The plant layout allows for sufficient expansion of its capacity to meet longterm increases in demand.

Jan 7, 1977

By M. J. Nicol, P. Balestra, E. Schalch

A detailed fundamental study has been made of the various factors that influence the partial reactions comprising the electrochemical model of the cementation of gold from cyanide solutions by zinc. The effects of cyanide concentration, pH, agitation, additions of lead, and the presence of various impurity ions on both the anodic dissolution of zinc and the cathodic reduction of gold have been investigated. The results are used to explain the influence of these variables on the rate of cementation, and possible implications of this work for plant practice are discussed.

Jan 1, 1979

By S. J. Bluhm

Recommendations are given for the design of multi-stage spray chambers in which air flows horizontally through water sprays. A detailed description is given of one such spray chamber at Hartebeestfontein gold mine that is used for bulk cooling of the incoming ventilation air, and that has been constructed according to these recommendations. A method for predicting the performance parameters of horizontal multi-stage spray chambers is given, and the method is illustrated with some examples. The method is equally applicable to spray chambers in which the water, rather than the air, is cooled.

Jan 1, 1979

By E. L. Atkinson, G. W. Leach

The paper discusses the reasons for the introduction of load-haul-dump (LHD) units into Greenside Colliery, and the circumstances leading to the replacement of conventional mechanized equipment on a trial basis in the mining operations on No. 2, 4, and 5 seams. An outline is given of the factors governing the selection and introduction of these units into coal mining, and the associated mining and engineering aspects involved in the optimization of their use. Operating statistics comparing the performance of conventional and LHD equipment are included.

Jan 1, 1979

By I. M. W. Preston

A new shaft system was required to replace stope face for the North Section of Harmony Mine and to allow for systematic opening up of the North Eastern Section. Owing to the economic circumstances at the time the project started, it became vital to alter the original planning and to sink the service shaft first. The MATLA coal-sinking headgear, a novel presinking arrangement, allowed sinking to continue to 108 m concurrently with the erection of the permanent sinking headgear and sinking winders. It is estimated that this arrangement resulted in a saving of two months on the overall project.

Jan 1, 1983

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 J. C. Vreugdenburg, W. A. H. Poppmeier

An overview of methods of manufacture is presented, as well as the results of laboratory experiments on the making of stainless clad steels. , It is concluded that stainless clad steel can be made in South Africa with existing rolling equipment, and that good bonding between the two materials depends on clean mating surfaces, proper edge welding, and a minimum reduction of 25 per cent at a rolling temperature of 120O"C. In practice, a minimum reduction of 70 per cent at 1100cC is recommended. : Suggested applications for clad steel include parts and equipment for the chemical, petrochemical, marine engineering, and mining industries, for the building sector, and for household appliances.

Jan 1, 1991

The paper discusses some theoretical aspects of Gy's sampling theory and provides reasons as to why it has found limited use in the mining industry, particularly for ores with low concentrations of values such as gold. These types of ores are referred to as low grade ores in the paper. It is shown that the misuse of the a priori liberation factor proposed by Gy is the main reason for the implementation limitation of Gy's model for low-grade ores. In addition, results of a case study done at the Gencor Geostatistics Department based On the new implementation of Gy's theory are provided.

Jan 1, 1996

By K. E. Mantell

1. TRACKLESS MINING AT OAMITES by K. E. MANTELL Oamites Mine, brought into production in late 1971, is located 50 km south of Windhoek, South West Africa, on the northern boundary of and just outside the Rehoboth Gebied. Oamites was known as a possible mining proposition at the turn of the century when Hanseatische Minen Gesellschaft was adit mining on the adjacent farm Kamzwas. Rand Mines Limited carried out a small amount of prospecting in the early 1960s, Falconbridge Explorations Limited later taking over the prospect. Approximately 4600 m of diamond drilling was carried out between 1965 and 1967.

By M. J. Daly

Historically, engineers and scientists, particularly those involved in the coal-mining industry, have been slow to adopt statistical methods. However, the need to obtain the maximum information .from expensive exploration and development programmes, and the current focus on total quality management, have led to a change in perceptions if classical statistical and geostatistical methods and their application as planning tools. Some if the underlying issues associated with the generally poor communications between statisticians and engineers/physical scientists, which contribute to some if the misconceptions relating to statistical methods, are discussed The potentially profitable application if a number if statistical techniques in the fields if geological evaluation and mine planning! development is also reviewed, with specific reference to the coal industry.

Jan 1, 1995

By S. W. Evans, G. Pienaar

Weldable steel plate with a good combination of strength and toughness is currently produced from 0,12 to 0,28 per cent carbon low-alloy steel heat-treated by roller quenching and tempering. Alternatively, steel plate of the same strength can be produced at a lower production cost by the use of very-low-carbon steel (0,03 to 0,08 per cent carbon) processed by in-line quenching without tempering. This paper reports the results of experimental work on these steels, and compares them with the properties of conventional steel. On thinner sections, it was found that the properties of the experimental steels compare favourably with those of conventional grades.

Jan 1, 1989

By M. G. Atmoret

It seems to me to be particularly appropriate that this topic should be discussed at the first prize-giving function of this kind. As you know, this presentation of awards to young mining engineers and metallurgists is to be an annual event, and never before in the dynamic and rapidly changing climate of the South African metallurgical industry has it been more necessary for young, and perhaps older, practitioners to consider the future of their profession and their role in the industry. I look forward with interest to the time, five to ten years from now, when I shall recall my crystal-gazing of tonight to see how far wrong I have been.

Jan 1, 1977

By R. K. Brummer

The support of stopes and tunnels in South African gold mines subject to rockburst damage requires special attention. The interaction of a seismic wave with either a stope or a tunnel is subject to a number of variables, namely the distance from the source of the event, the ground velocity, the orientation of the excavation with respect to the direction of the seismic wave, and the geology and fracturing around the excavation. This paper discusses these factors in relation to the support requirements in stopes and tunnels. The need for the integration of hydraulic props with stope support and the use of yielding anchors for tunnel support are emphasized.

Jan 1, 1988

By C. E. Feather, G. M. Koen

The significance of the mineralogical and surface characteristics of gold grains in the recovery process by C. E. FEATHER B.Se. Hons. (Cape Town)* and G. M. KOEN D.Se. (Pretoria)* A description is given of the nature and occurrence of gold at various stages in the process of its recovery from Witwatersrand and related ores. Electron microprobe investigations show that the surface of gold grains in the ore is already coated. During metallurgical processing, further coatings, mainly hydrated iron oxides, accumulate on the grains. Theories are advanced for the formation of these coatings, and the adverse effects on metallurgical operations are discussed.

By S. Visage

By 1984 Iscor's first direct-reduction plant will be operating at the Vanderbijlpark Works, and for the fin;t time the Corporation will have an alternative method to the blast furnace for producing iron from ore. The performance of Iscor's four-kiln plant, which will be the largest coal-based plant in the world producing sponge iron, will undoubtedly be watched with great interest by steelmakers throughout the world. Beneficiation of tin The Southeast Asia Tin Research and Development (SEATRAD) Centre is a regional oganization, formed by the Governments of Indonesia, Malaysia, and Thailand with assistance from the United Nations, to conduct, coordinate, and promote research and training in the various fields of tin production, including geology, prospecting, mining, mineral processing, and smelting.

Jan 1, 1982

By J. A. Ryder, M. U. Ozbay

An ERR-based methodology is presented for use in the re-assessment of the performance of stabilizing pillars, taking into account the effects of fracturing that can occur in pillar foundations under conditions of high stress. It is shown that the damage in the foundations of under-designed pillars can cause up to 30 per cent increases in ERR compared with the ERR for pillars with unfractured foundations. Despite this reduction in assessed performance, stabilizing pillars are still generally found to result in substantially lower ERR levels than alternative methods of reducing ERR, such as the use of stiff backfill or backfill ribs.

Jan 1, 1990

By M. Klapwijk

Ancient Metallurgy - In addition to the preceding three papers, the following three contributions were received for publication 1. An analysis of Bantu-made iron implements from the Letaba district M. KLAPWIJK INTRODUCTION It has often been stated that it is hardly possible in South Africa to classify Bantumade iron hoes according to their places of origin and manufacture. It is well known that these hoes were used for barter, and as currency in the purchase of livestock or the payment of lobolo, although reports of the value of the hoes differ widely. The difficulty in their classification has arisen from their distribution over a very wide area.

Jan 1, 1974