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By G. Panopoulos, R. P. King, A. H. Juckes

The flotation characteristics of two South African coals were investigated: one from the Dumacol Colliery in Natal, and the other from Landau Colliery in the WitbankCoal Field. Samples of fine coal (smaller than 1 mm)were studied, the Dumacol coal showing significantly better ash-liberation characteristics than the Landau coal. Neither coal was found to produce satisfactory flotation concentrates, except at very fine sizes. The poor flotation performance can be ascribed to the non-selective flotation of unliberated particles that may contain considerable quantities of ash. Flotation recoveries were greatest for particles between 100 and 200 µ m, and fell of rapidly as the size increased above 200 µ m. Very fine particles were found to float adequately, and acceptable concentrates can be made at comparatively high yields from materials smaller than 75 µ m. The flotation of ultrafine coal was demonstrated successfully in a continuous pilot plant. This result opens the way to a potentially viable industrial process for the beneficiation of ultrafines from the Witbank No. 2 seam, which for decades has been regarded as non-floatable.

Jan 1, 1986

Now a new generation of computerized drill rigs has been launched and they are based on modern standard PC-computer technology. The rigs have been well embraced by the market and more than 100 units have left the assembly line. The new generation has taken a quantum leap forward with respect to drilling accuracy, logging capabilities, reduction of manpower in some types and serviceability compared to the previous generation of drill rigs. The Can bus technology, well proven in the automobile products, is the backbone in the new generation control system of Atlas Copco. The short-term development is now focused on establishing this new automation platform on other product lines of Atlas Copco products. The long-term objectives is to offer the mining industry Atlas Copco products with one common automation platform. Essential for Atlas Copcois to contribute to the work with the on-going Data Exchange standard between mining machines and mining computer systems (IREDES). Our belief is that an accepted standard will make mine automation programs affordable for a wider base of the mining industry, because of the possibilities to a cost effective integration of different equipment with a minimum of system integration problems and machine specific interfaces.

Sep 1, 2001

By J. G. Ferguson, R. E. Burnton

The nature of the coal and of the roof in No. 3 seam at Coal brook Collieries is such as to preclude the use, during bord and pillar mining, of conventional mining equipment that employs cutting and blasting in its production cycle. Continuous mining machines of the borer type, operating within a mining height range of 1,9-2,3 m, have been successfully employed in No. 3 seam since 1957.The experience gained with this type of equipment, the operational methods adopted, and the results achieved are described. The ventilation method used to eliminate the dust and methane hazards created by this type of equipment is stressed. The limitation on the minimum mining height that can be obtained with the borers in use has lead to the recent introduction of a Rotary Drum type of continuous mining machine. This equipment is capable of operating in areas where the seam width decreases to 1,5m. The production potential of the machine has been proved. The roof conditions created by the cutting action of the Rotary Drum type of miner are not considered satisfactory and a modified drum head profile is to be tried.

The Centenary Luncheon for Past Presidents was held on Thursday, 24 March, 1994 at The President's Room at Gold Reef City, Johannesburg at 12:30. Herewith the proceedings that followed. Dr H. Scot-Russell It is with great pleasure that my fellow Office Bearers and I welcome you, our Past Presidents, to this luncheon to mark the centenary of the SAIMM. Today one hundred years ago, a group of professionals met and agreed to draw up the constitution and by-laws of a society later to be called an Institute. The Presidents of the Institute, of course, become its Past Presidents and help to guide its progress. A number of our sister institutes cannot wait for their Past Presidents to move of their councils, and cannot understand how we can give such free reign to ours! We believe it one of our strengths. The successful cooperation between our Past Presidents and ourselves is due to the personalities of these men. They attend meetings not to ensure that the status quo is maintained, but allow the current Office Bearers freedom to lead the Institute as they think fit. But they are always present to give sound advice, a helping hand, and support to the Institute in every way.

Jan 1, 1994

By M. B. Cortie

The historical development of materials engineering in the mining industry Is briefly reviewed, and some of the factors currently influencing the industry in South Africa are discussed. Material usages in various parts of the mining operation are surveyed. The predominant mechanisms in the degradation of materials in mines are wear, corrosion, and fatigue. The issue of corrosion-abrasion Is considered, but it Is concluded that abrasive wear predominates in most rock-handling and comminution applications and that, in general, little economic benefit Is to be gained in those applications by the use of existing corrosion-resistant alloys. However, alloys with a measure of corrosion resistance find profitable application elsewhere in the mining environment. The use of other engineering materials such as polymers, ceramics, al1l1inium, and various ferrous alloys may be economically viable in a variety of niche situations. Identification of the most cost-effective material in each case calls for a systematic approach and some patience.

Jan 1, 1996

By Z. T. Bieniawski

Estimating the strength of rock materials by Z. T. BIENIAWSKI, Pr.Eng., D.Sc.(Eng.) (Visitor) A practical approach for estimating the strength behaviour of rock materials is presented. The demand for data on rock properties in engineering design is considered, and it is shown that, based on the trends observed in the South African mining industry during the last twenty years, simple and easy-touse methods for the estimation of the uniaxial and triaxial strength of rock materials are needed. It is shown that the uniaxial compressive strength of rock can be conveniently determined from the pointload strength index, which is obtained underground on unprepared rock cores. The triaxial strength of rock can be estimated for most practical purposes from empirical strength criteria. Two such criteria are proposed that allow estimation of the triaxial strength for rock materials to about 10 per cent. The only input required for these criteria is the uniaxial compressive strength. The validity of the practical approach outlined in this paper is confirmed from the experimental tests conducted on some 700 rock specimens representing five rock types. A practical example for the prediction of rock strength is given.

Jan 3, 1974

By N. B. Strydom, H. H. E. Schroder, A. van der Linde

This paper describes a study of the destination of the mercury that is present in the ore during the recovery of gold. It was found that over 96 per cent of the mercury passed through the process untouched. A small amount finds its way into cyanide solution, and is concentrated with gold in Zinc dust as Merrill precipitate. When the precipitate is calcined, the mercury is driven off and finds its way into the atmosphere. However, dilution of the stack gas in the atmosphere appears to be sufficient to prevent hazardous concentrations arising at ground level. No other significant concentrations of mercury were found at any stage of the process. The amount of mercury lost to the atmosphere by this mechanism appears to be less than 200 kg per year throughout the gold-mining industry in South Africa. Virtually no mercury vapour could be detected in the air in the smelt-house. Slight increases in mercury concentrations above background level were observed in soils around the reduction plants and in the discharge or return waters, but no environmental stress is anticipated from these increases.

Jan 1, 1982

By R. J. Gordon, N. J. Keys, N. F. Peverett

Photometric sorting of ore on a South African gold mine by N. J. KEYS. B.E. Met. (Queensland) (Visitor). R. J. GORDON. (Visitor). And N. F. PEVERETT. B.Sc. (Eng.) (Wits) (Fellow) This paper concerns the development and application of a high-throughput, multi-stream photometric sorting machine developed for the South African gold mines. It is now believed that this sorter and its progeny may be found suitable for a large proportion of all possible sorting applications. A laser-light source and sensitive photomultiplier are employed in a scanning system to detect light reflected from the surfaces of rocks passing through the sorting zone. Electronic circuitry then analyses the photomultiplier signal, which represents the varying intensity of the reflected light, and produces control signals to actuate the appropriate valves of an array of air-blast rejection devices to remove from the feed certain particles selected by the analysing process. Typical throughput per machine ranges from 50 t/h for a minus 60mm plus 30mm feed to 200 t/h for minus 150mm plus 70mm material.

Jan 9, 1974

By N. C. Gay

During the past two to three years, there have been some significant Improvements to the quality of the support systems being used on South African gold mines, and the Implementation of these new developments, together with more worker awareness has been instrumental in reducing rock-related accidents, particularly in deep mines. This paper provides guidelines to mine and group personnel on how to monitor the ongoing Implementation of new technologies and so ensure the benefits that will accrue in terms of mine safety and profitability. Particular attention is given to the establishment of auditing procedures that will enable management to assess the benefits obtained from new technologies, as well as providing Improved maintenance procedures and procedures for the optimum utilization of seismic data. The areas that receive most attention include support systems for stopes and tunnels, such as hydraulic props, backfill, and rockburst-resistant tunnel support; stope and regional support layouts; mine standards; and staffing of the rock-engineering department. The paper includes a draft audit form and a hypothetical example of an audit report

Jan 1, 1997

NIM Reports Report No. 1563 Neutron activation analysis of samples from the Kimberley Reef Conglomerate. Report No. 1569 The use of DDTU as an analytical reagent for the noble metals. Special general meeting A Special General Meeting of the Institute was held in Kelvin House, Johannesburg, on Wednesday, 14th November, 1973. The President, Mr P. W. J. van Rensburg, opened the meeting at 9 a.m. and read the notice of the meeting, which was as follows: Colloquium and general meeting CONSTRUCTION OF SLIMES DAMS A General Meeting and Colloiquum on the above topic was held on November 14th and 15th, 1973, at Kelvin House, Johannesburg. Mr P. W. J. van Rensburg (President) was in the chair. The Colloquium was attended by 135 delegates and was opened by the President at 9.10 a.m. Orange Free State Branch PROCEEDINGS OF THE ANNUAL GENERAL MEETING The Annual General Meeting of the Branch was held in the Western Holdings Cant,een on Tuesday, 11th September, 1973, at 7.00 p.m. Book Review Westwood, W., and Cooper, B. S. Analytical methods in use in non-ferrous minin~ and metallur~ y: a selective review. London, Institute of Mining and Metallurgy, July 1973. 54 pp. £3.50.

Jan 12, 1973

By H. S. Sichel, Kleingeld

A frequency distribution model plays a fundamental role in ore evaluation, especially for the feasibility study of new deep gold mines. The geological complexity of the reefs being mined at present in the Witwatersrand basin poses some difficulties regarding the modeling of the underlying ore-value distribution. This geological complexity has given rise to a need for more applicable distributional models. This paper places the geology of the Witwatersrand basin in perspective and draws some important conclusions from the genesis of the deposition. In addition to the three-parameter lognormal model, two more-general distributional models are proposed. These are the compound lognormal (CLD) and log-generalized inverse Gaussian (LN-GIG) distributions. A detailed, although preliminary, comparative study of these two more-general models with the three-parameter lognormal model is described, and the efficiencies of the estimates and modeling are analysed. It is found that the broad assumption that gold grades follow a three-parameter lognormal law is not always the case, and the need to test for departures from log normality should be emphasized so as to ensure the use of appropriate models.

Jan 1, 1992

By A. Ball

This paper addresses the need for a unifying model that will permit the selection and design of optimum materials for a given wear situation. With this objective in view, the characteristics of the various forms of abrasive, adhesive, and erosive wear are described in terms of localized stress, strain, strain rate, and frictional heating. The measured performance of a variety of metallic, ceramic, and polymeric materials and coated or surface treated materials are described briefly. These results were obtained under conditions of dry-particle abrasion, abrasion in conjunction with corrosion, cavitation erosion in liquids, erosion by particles in low- and high-velocity gas streams, and erosion by particles in a liquid stream. Electron microscopy was used extensively, together with microhardness profiles, in the determination of the modes of material detachment and the underlying deformations and structural changes. As a result of the experimental work, a model based upon a critical strain to microfracture is presented. The microstructural features and materials properties that determine wear resistance are discussed.

Jan 1, 1986

By C. J. Fauconnier

The main purpose of the paper is to determine the contribution of fluctuations in barometric pressure to flammable gas explosions in South African mines. For this purpose, the barometric-pressure patterns preceding each of the 59 major explosions in South African gold and coal mines over the past 20 years were analysed. It is concluded that diurnal fluctuations in pressure do not have a major influence on the accumulation of gas in the underground workings, but that pressure drops associated with cyclonic weather systems moving across the country over a number of days are the major factor contributing to gas explosions in mines. To illustrate some of the points made in the paper, the Hlobane Colliery explosion of September 1983 is used as a case study. In the final section, several general conclusions are drawn and recommendations put forward as to how mines should recognize and react to meteorological phenomena that may lead to an increased probability of gas explosions in underground workings.

Jan 1, 1992

By H. D. Mtegha

The Southern African Development Community (SADC) aims to harmonize mineral policies and regulatory regimes in the minerals sector. This paper provides a review of the progress made towards harmonization of mineral regimes in the region. It singles out only the mining fiscal environment, as this is normally one of the key issues of interest to potential investors as well as the host state. Indications are that the region is slowly progressing towards a more harmonized approach, and there is evidence that the ?race to the bottom? has been prevented, which is the basis for an integrated mineral sector that the region aspires to.

Jan 1, 2011

By A E. Paterson

General aluminium corrosion charts based on 1100 alloy listing product and temperature have been developed by AFSA, mainly from available sources. The categories of corrosion expectation are fairly wide. As a result the charts are more useful in indicating what is not suited as distinct from what is. The question of how to develop useful information is assessed. Having discarded improbable options one is left with the need to refine the possible. Within each alloy group corrosion potential differs. From an engineering application point of view, the corrosion resisting marine alloys, the 5xxx series show increasing corrosion as the percentage of Magnesium increases. An important issue is that as the welding filler used for 5xxx series is Mg rich (to avoid hot cracking), the filler is likely to show the weakest resistance. In addition, when subjected to fatigue loading, the preference for critical joints is to dress the joint to the level of the base material. Overheating of the weld extends the HAZ zone and weakens the material as Mg moves to the grain boundaries. Indicator chart refinement approaches suited to aluminium use in commercial transport are discussed.

Jan 1, 2006

By J. W. Wilson, P. C. Graham

Raise-boring experiences in the gold mines of the Anglo American Corporation Group by J. W. Wilson M.Sc., M.I.M.M., F.S.A.I.M.M., M.A.I.M.E. and P. C. Graham M.Sc. (Eng.) Gold mining is being carried out at ever-increasing depths in South Africa. For reasons of safety and human comfort, it is becoming imperative for raises to be developed by means other than conventional drilling and blasting. Raise-boring is an attractive alternative method. Initial raise-boring experiences in South African gold mines showed disappointingly high costs due to the abrasivity and difficulty of drilling Witwatersrand quartzites. Consequently, a research and development project was instigated with the objective of making raise-boring an economically viable technique in hard abrasive rock. A Robbins 61R raise-borer was made available to the Research and Development team and a number of raises have been drilled. During these trials two advances in cutter design were tested. This paper presents the results obtained, including drilling costs, and provides details of the equipment used.

Palladium Alloys. E. M. Savitskii, V. P. Polyakova, M. A. Tylkina. Translated by: R. E. Howard. Published by Primary Services, New York, N.Y. 10012. $24.50. The output of palladium in the U.S.S.R. greatly exceeds the internal usage. The primary purpose of this 200 page volume is therefore to record details of fundamental researches on the properties of this metal with a view to expanding its marketability. Theoretical studies have revealed a number of alloys with great promise in electrical instruments and for the chemical industry. The success of these researches in the U.S.S.R. and in the U.S.A., resulted in the industrial usage of palladium exceeding that of platinum in 1957 and increasing its lead during the next decade. This volume is divided into three parts. Section I covers the mineralogy, extraction and the physical metallurgy of the metal. It records a considerable area where the resistance to corrosion of palladium equals that of platinum. Section II deals with the preparation and the properties of palladium in alloys and contains a comprehensive metallographic treatment of the many binary alloy systems. Section III is devoted to industrial applications. The 460 references which are quoted are mainly from the U.S.S.R. but otherwise have a world-wide coverage. H.B.

By A.M. Edwards

1. Book reviews Platinum in South Africa, compiled by A.M. Edwards and M.H. Silk. Randburg, Council for Mineral Technology (Private Bag X3015, Randburg, 2125 South Africa), 1987. 55 pp. U$30. Reviewer: R.D. Wintle Scientific and technological developments in extractive metalurgy-G.K. Wiliams Memorial Volume. Parkvile (Australia), The Australasian Institute of Mining and Metalurgy, 1986. $A12 (incl. surface postage). Reviewer: T.Y. OweD Ion exchange and sorption processes in hydrometa/urgy, edited by M. Streat and D. Naden. Chichester, John Wiley & Sons, 1987. 229 pp. Reviewer: B.R. Green Role of Government in mineral resources development, edited by Michael J. J ones. London, The Institution of Mining and Metalurgy, 1985. 180 pp. £40. Reviewer: K.E. Ducat 2. Recent publications Annual report 1987. International Tin Research Institute, Kingston Lane, Oxbridge, Middlesex UB8 3PJ, England, 1988.Tin and its uses no. 156. Address as above. 3. Mintek reports Application Report no. 5 The production of and alusite and other refractory minerals. 1988. 16 pp. . Application Report no. 6 The development up to commercial application of a process for the recovery of lead, copper, zinc, and silver from the Black Mountain deposit. 1988. 14 pp.

Jan 1, 1988

By NONEn NA

1. Book reviews . Rudiments of mining practice, oy C.E. Gregory.Clausthal-Zellerfeld (West Germany), Trans Tech Publications.OS$24.Reviewer: A.N. BrownProfessor Gregory has had a wide experience of hardrockmetalliferous mining throughout the world, beinga well-known academic who has taught at many universitiesin the Western World. His basic training was obtainedin his native land of Australia. In this publication he identified the need for a basic, simple book on miningpractice to provide new students of mining with a backgroundto their studies. He also designed the book to providea background to persons operating on the fringesof the industry such as students of economics and journalists.The text extends to only some 120 pages, and containsa sufficient number of monochrome sketches, diagrams,and photographs. It is written in a straight-forward, easyto-read style. The book contains an index and elementarytable of conversion from imperial to SI (metric) units,and there is also a glossary of mining terms that mostreaders would find useful.The author has succeeded in keeping the contentssimple, as indicated by the title. However, after each chapter, there are references to further recommendedreading. The book could be useful in the South African context, although the coverage of coal and opencast mining operations is slender.

Jan 1, 1987

By L. A. Vermeulen, D. D. Howat

Extensive work was done previously on the wear of grinding media and on the comminution processes operative in bal milling based on the determination of the number-size and mass-size distributions of samples of balls taken from bal mils by a specially designed device. Proof that a sample is as nearly representative as possible of the whole mass of material from which it is drawn is usually extremely difficult. This paper reports a special case in which a direct comparison was made between the number-size and mass-size distributions obtained from a sample drawn from a mil and those from the whole bal charge emptied from the mil. Exposure of the internal defects of the grinding balls caused them to develop irregular shapes after wear had reduced their diameters by about 50 per cent. As a result of the marked change in the morphology of the grinding components, an anomaly was observed between the proportion of small components collected by the sampler and that determined in the total charge. Except for this anomaly, a marked similarity was found in the data relating to the larger components in the sample and the total charge, indicating that the sample obtained by the procedure outlined is representative of the mass of the grinding charge in a mill.

Jan 1, 1989