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COUNCIL FOR 1989/90 President Dr O.K.H. Steffen President-elect Mr H.G. Mosenthal Senior R.D. Beck Vice Presidents Junior ].P. Hoffman Immediate Past President C.E. Fivaz Honorary Treasurer Dr H. Wagner

Jan 1, 1990

By O. G. Pauw

The relationships between mill power and pebble load, bulk density of the load, and circulating load were investigated on the pebble mills in the grinding circuit at Buffelsfontein Gold Mine. This paper describes the most significant relationships among the operating and control variables on the plant, and illustrates these by reference to experimental data gathered from the plant during operation. The results were used for the development of very successful multivariable peak-seeking controllers for the pebble load and bulk density of the load on these pebble mills. The peak-seeking control algorithms are described in detail. The control system has operated successfully at Buffelsfontein for more than 18 months and is still in operation.

Jan 1, 1985

By H. A. D. Kirsten

Mining-induced seismicity is usually evaluated in terms of continuum elastic analyses, and is quantified in terms of energy release rate as state parameter and excess shear stress along particular features on which failure may be induced. Although both of these quantities are representative measures of potential seismic activity, elastic analyses do not enable the associated stresses and displacements in the rock in which failure occurs to be evaluated reliably. The paper compares the effect of depth, span, support stf1Jhess, field stress ratio, and discontinuity strength on mining induced seismicity determined from elastic analyses and from analyses in which discontinuities in the rock are allowed to fall. It is, accordingly, shown that the incidence and magnitudes of potential seismic events and the net excess shear as representative state parameter cannot be determined reliably from elastic analyses that do not account for the failure of ubiquitous discontinuities. The magnitudes of seismic events in rock in which ubiquitous discontinuities are allowed to fail are very considerably overestimated in elastic analyses. The extent of the seismic source region and the associated seismicity do not increase with depth, which, together with the improved containment of the concomitant rockburst damage by backfill is reassuring for mining at greater depth in future. For conventional support, the magnitude of potential seismicity increases for an increase in span in elastic rock, but remains unaffected in non-elastic rock. For backfill, the magnitude of potential sesmicity decreases substantially in elastic and non-elastic rock for an increase in span. Increases infield stress ratio very significantly reduce potential seismicity irrespective if the type if analysis, but effect the distribution if potential seismic events very differently in elastic and non-elastic rock.

Jan 1, 1994

All photographs by Carlos Pais Pictures only.... no script.

Jan 1, 1985

By J. P. Hoffman

The School on the Continuous Casting of Steel, the second school organized by the Technical Programme Committee-Metals Technology of The South African Institute of Mining and Metallurgy (SAIMM), was held at the C SIR Conference Centre from 16th to 20th May, 1988.

Jan 1, 1988

The South African Institute of Mining and Metallurgy (SAIMM), together with his many friends and colleagues in the mining industry, mourn the loss of one of their most respected and well-loved personalities, Dave Viljoen, who passed away on 23rd June, 1988, in Sevile, Spain.

Jan 1, 1988

By D. J. Adams, R. G. Gürtunca

CONTRIBUTION BYJ.F. CURTlS The paper, which in an exemplary manner records the monitoring of backfill behaviour, falls short in the 'rock engineering' stated in the title. Just what the objective of the rock engineering was is obscure.

Jan 1, 1992

'We are going to be short of engineers for the foreseeable future, and particularly short of civil and heavy-current electrical engineers'. This is the basic message that emerges from the report 'The supply of and demand for engineers, 1984,t, prepared by Dr Philip Lloyd and Professor Bob Plewman for the Federation of Societies of Professional Engineers (FSPE).

Jan 1, 1985

NOTICE The Institute has received requests for copies of Uranium in South Africa', Vols. 1 and 2, but is unable to supply, as all copies have been sold out. If any members have copies they wish to dispose of it would be appreciated if they would contact the Secretary, P.O. Box 1183, Johannesburg. Telephone 834-1271.

On 24th November, 1982, Mr L. W. P. van den Bosch was inducted as the President for 1982/1983 of the Associated Scientific and Technical Societies of South Africa, which represents more than 40 scientific, professional, and technical bodies. Lynne Wilson Pearson van den Bosch was born at Senekal in the Orange Free State on 11th February, 1921. He was educated at the Hoer Volkskool, Heidelberg, and the University of the Witwatersrand, where he obtained the B.sc. degree in mining engineering.

Jan 1, 1983

Review Mining annual review June 1979. London, Mining Journal, 1979. 624 pp. Available as part of the subscription to the Mining Journal or at £12,50 per copy. This annual review is recognized internationally as the world leader in reporting on metals and minerals, and is eagerly awaited each year for its authoritative content, which is compiled by well-respected experts throughout the world.

Jan 1, 1979

By D. W. Horsfall

This paper reviews the properties and uses of mixtures of coal with fuel oil, methanol, or water, emphasis being placed on mixtures of coal and water. The material presented is taken from studies conducted overseas, and it is recommended that similar studies should be conducted on mixtures containing South African coals, which differ from the coals of the northern hemisphere

Jan 1, 1990

By B. J. Madden

The formula developed by Salamon and Munro in 1967 has been used for the past 22 years in the design of bord-and-pillar workings in South African collieries. This paper re-assesses the formula In the light of Its past performance and examines the effect of mining method on coal-pillar strength. An account is given of the extension of the formula so that it can be applied beyond the empirical range for which it was derived, and the advantages of the extended formula (the squat-pillar formula) are described.

Jan 1, 1991

By J. E. Robinson, W. Pilkington, J. L. Taylor, B. J. Bluhm, E. B. Viljoen, P. Le Grange

The Chemwes uranium plant was designed and constructed within fifteen months; commissioning started during. June 1979, and the plant was producing at design capacity four months later. This account highlights the procedures and methods adopted to bring the plant Into production. The description of the various phases includes some details of the early evaluation, and the feasibility and optimization studies; of the financing, project management, design, construction, and commissioning of the plant; and of the training of personnel. Some of the mistakes made and the factors that contributed to the success are also listed.

Jan 1, 1981

By W. F. A. T. Meihack

The scope of this paper is confined to gas-fluidized beds in pyrometalurgical applications. After considering the general characteristics of these fluidized beds, the author deals with their potential applications, using the following processes, which are currently under investigation, as examples: pretreatment of chromite, prereduction of manganese-ore and iron-ore fines, roasting and prereduction of ilmenite, and roasting and pyrolysis of gold-bearing pyrite. He concludes that fluidized beds are potentially of great benefit to the metallurgical industry, although much developmental work remains to be done.

Jan 1, 1986

The problem of providing adequate thrust to manually operated rockdrills operating at air pressures of 70 lb/in2g to 80 lb/in2g with the aid of an air-leg is analyzed. It is shown that adequate thrust is provided by an air-leg or the stiff-leg if it is inclined at an angle to the floor of about 25°. However, this requires that the leg react against some support or protuberance, as the friction force between the leg and the floor is inadequate to contain the thrust. Conclusions summarizing optimum thrusts, blow frequencies, penetration rates, drill steel life and bit wear are presented.

By J. Ungar, F. X. McGarvey

The selectivity of ion-exchange sites varies with the matrix of the polymer, the nature of the site. and the method of application. The effect of these variables on the recovery of uranium is examined. with particular attention to vinyl pyridine and to symmetrical and asymmetrical quaternary ammonium sites. The effect, on the loading. of high concentrations of chlorides in the liquors is discussed. and other components of the liquors that may cause fouling of the resin are also considered. The discussion is supported by the results of tests conducted on various types of resins. The economics of the process is discussed briefly.

Jan 1, 1981

By C. T. Connor, O&apos

The fifth University of Cape Town (UC1)/University of Stelenbosch (US) Minerals Processing Symposium was held at the Faculty of Engineering, University of Stelenbosch on Friday, 8th August, 1986. This series was initiated in 1982, the symposia being held alternately in Cape Town and Stelenbosch. The South African Institute of Mining and Metallurgy has kindly agreed to sponsor this event for the next three years. Cokemaking On the initiative of the European Cokemaking Commitee, the First International Cokemaking Congress will be held in Essen (F.R. Germany) from 13th to 19th September, 1987. It is being organized by the Steinkohlenbergbauverein, together with the Verein Deutscher Eisenhitenleute.

Jan 1, 1986

By H. Skretting, J. Gundeesen

The paper compares operational parameters for the electric reduction smelting of pig iron and ferroalloys in pilot and industrial furnaces. Data from two pilot furnaces of approximately 200 and 500 kW operating-load capacity, as well as from several production furnaces, are included. Examples are given for the smelting of pig iron, ferronickel, ferromanganese, ferrochromium, and ferrosilicon. In most instances, the results from the pilot furnaces, such as the values for consumption and product analyses, corresponded fairly well with comparable data from the industrial furnaces. For ferrosilicon, the power consumption in the pilot furnace was higher than that in the industrial furnace.

Jan 1, 1979

By D. R. Hardman

Coal mining has been practised in South Africa for over one hundred years. The total production increased gradually in the early pat of the twentieth century, but over the past twenty years the rate of growth has been considerable. Although opencast mining has contributed largely to this increase in production in recent years, underground bordand- pillar operations still contribute slightly less than 50 per cent of the total production. The paper highlights problems arising from old bord-and-pillar workings, and an indication is given of how some of the problems have been addressed.

Jan 1, 1990