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[COUNCIL FOR 1992/93 President J.P. Hoffman President Elect Dr H. Scott-Russell Vice Presidents Senior J.A. Cruise Immediate Past President R.D. Beck Junior D.A.J. Ross-Watt Honorary Treasurer J.A. Cruise Members of Council Dr N.A. Barcza B.R. Broekman G.A. Brown P.M. Craven Prof. R.J. Dippenaar J.R. Dixon* A.A.B. Douglas B.R. Fleetwood Dr R.V.R. Handfield-Jones P.R. Janisch * co-opted P.J. Knottenbelt R.P. Mohring J.L. Nel* K.C. Owen P.D.K. Robinson K.A. van Gessel D.J. van Niekerk C.J.C.J. van Vuuren* P.M.T. White]

Jan 1, 1993

By Y. J. F. Haven, G. H. J. Kitson, D. G. Beadle

I have read this paper with considerable interest. By using an automatic instrument to assess the dust samples taken in South African collieries, the authors are ahead of the gold mining industry, which still uses the laborious method of microscopic assessment, with its limited accuracy, of the half-a-million dust samples taken each year. As the authors state, the result obtained from the photoelectric assessment of the samples is approximately proportional to the surface area of the respirable dust. However, modern theory is that, in assessing coal dust, it is the respirable mass which is important in determining the danger to health. Thus Table II of their paper is of considerable value in showing the relationship between the P.E.R. value and the mass concentration measurement. Unfortunately this table only gives the mean relationship. The important point is to know the scatter around this mean. If the scatter is small, then this mean value (for different operations) would have considerable value in converting from respirable surface area to respirable mass, but if the scatter is large, then such a conversion, using a fixed factor, will have little value. In the text the authors mention the range of values as being between 3 to 24, but without a statement on the number of samples used to determine this range and their distribution, this is a rather nebulous statement. I hope, in their reply, that the authors will give, in statistical terms, some statement on the overall correlation between these two parameters. I might add that at present a member of my staff is working on similar relationships for dust samples taken in gold mines. Another factor which may well be most important in determining the danger of dust levels in coal mines is the composition of the dust, specifically its quartz content. I understand that the authors have some information on this point, and to make their results of greater value in International comparisons of dust levels and the concomitant development of pneumoconiosis, it will be extremely useful if they could place this information on record. Even though, as I have said above, modern theory postulates that respirable mass is a better parameter to use than respirable surface area, the problem remains of how to measure this parameter with short time sampling, which, as the authors point out, is their preferred strategy for dust sampling and dust control. I know of no easily portable instrument, independent of external power supplies, which can, in 5 to 10 minutes, collect sufficient dust to enable it to be weighed accurately. Thus the authors' implied intention of continuing to sample by their present techniques and using their present parameter to report the results is, in my opinion, an entirely valid decision.

Jan 10, 1968

Copper cyanide is a common component of cyanide-treatable precious metal ores. The copper concentration in production heaps can be predicted from laboratory column tests, but the exact correlation is not necessarily intuitive. Generally, heap leach operators like to keep copper concentrations in solution below 300?500 ppm and may note problems with gold recovery and cyanide consumption when copper concentrations exceed this amount. There are several methods of copper removal from cyanide solutions including ion exchange; direct electrowinning; acidification, volatilization, and recovery (AVR); and sulphide precipitation such as the sulphidization, acidification, recycling, and thickening (SART) process. SART involves acidification with addition of soluble sulphide, separation of the resulting copper sulphide precipitate, and addition of lime to re-establish alkalinity prior to returning the solution to the leaching process, recovering both copper and cyanide as valuable products. In principle SART is very simple. Yet some SART plants that have been built may have been unnecessarily complex. This paper explores the basics of SART and makes the case for a simple plant design as applied to the heap leaching circuit.

Jan 1, 2012

By B. K. Loveday

A model for the leaching of non-porous particles by B. K. LOVEDAY*, Ph.D. (Fellow) A model has been developed for the prediction of the rate of leaching for an assemblage of non-porous particles in terms of size-distribution parameters. Expressions are developed for batch and continuous operation, and an example of the application of the model is given.

Jan 9, 1975

By A. D. Thomas, K. C. Wilson

Some years ago, the authors developed an analysis of non-Newtonian pipe flow based on enhanced turbulent microscale and associated sub-layer thickening. This analysis, which can be used for various rheologic modelling equations, has in the past been applied to smooth-walled pipes. The present paper extends the analysis to rough walls, using the popular Bingham plastic equation as a representative rheological behaviour in order to prepare friction-factor plots for comparison with measured results. The conditions for laminar-turbulent transition for both smooth and rough walls are also considered, and comparisons are made with earlier correlations and with experimental data.

Jan 1, 2007

By J. N. Van der Merwe

The South African coal-mining industry uses a uniform safety-factor formula for non-squat pillars, incorporating a coal-strength constant that was derived empirically by Salamon and Munro in the 1960s. The constant is 7,2 MPa. Since that time, collapses of pillars at relatively high safety factors have occurred in the Vaal Basin. Analysis of the post-1960s' collapses indicated that the strength constant for the Vaal Basin is 4,5 MPa. A crude method for the prediction of the minimum life span of pillars in the Vaal Basin is presented.

Jan 1, 1993

By P. M. Scott

The South African Institute of Mining and Metallurgy held a colloquium on 'The Selection of Equipment for Underground Mining' in Johannesburg on 22nd September, 1982, which, judged by the interest shown, was an unqualified success. Mintek 50 As announced earlier, the Council for Mineral Technology (Mintek) will be celebrating fifty years of growth in 1984 and is organizing an international conference, MINTEK 50, on its areas of special expertise. Drilling Once again the South African Drilling Association will be holding a technical symposium in 1983. ILAFA Congresses The Instituto Latinoamericano del Fierro y el Acero (ILAFA) has scheduled the following congresses for 1983:

Jan 1, 1983

By J. D. Wells

An account is given of the planning required for the rehabilitation of land that is to be disturbed by opencast mining, and of the preparation of rehabilitation of land that is to the Inspector of Mines. The plans Include the provisions that are to be made to allow for climatic conditions, land use, vegetation and wildlife, surface-water resources, geology and ground water, soils, land capability, rehabilitation method, location of discard dumps and slurry ponds, pollution control, and costs. . . Monitoring of the operation is the only way that the rehabilitation plan can be improved, and both monitoring and planning are essential when provision is being made for the closure of a mine.

Jan 1, 1986

By J. H. Lazarus

The evolution of backfill-distribution systems for deep gold mines is examined. The status of current technology for the design of backfill-distribution systems is considered with reference to pipeline pressure gradients, pipeline wear rates, and slurry flow regimes. The effect of an increase in the relative density of the slurry on the performance of backfill-distribution systems is illustrated. Future trends regarding the design of backfill-distribution systems are discussed.

Jan 1, 1993

By I. J. Barker, D. A. Vetter, G. A. Turner

The modeling of the uranium-leaching process, and the logging of data from a plant for the evaluation of the model, are reported. A phenomenological approach was adopted in the development of the model. A set of eight chemical reactions was chosen to represent the complex chemistry of the process, and kinetic expressions for these reactions were incorporated in differential equations representing mass and energy balances. These equations were coded in FORTRAN to form a program that simulated the process, and that allowed averaged and continuous data from the plant to be compared with the model. This allowed the model to be 'tuned', and to reveal a number of minor

Jan 1, 1989

By F. P. A. Robinson, C. R. Thomas

Stress-corrosion studies on materials used for surgical implants * by C. R. THOMAS and F. P. A. ROBINSON Samples of Vitallium (a cobalt-chromium alloy), 316L stainless steel, and titanium T318 were subjected to the boiling magnesium chloride test so thattheir susceptibility to stress-corrosion cracking could be determined, and their behaviour under service conditions was then assessed. Stress-corrosion cracking was confined to the stainless-steel samples, while gross pitting was detected in the samples of forged Vitallium. It was concluded that the use of stainless steel should be avoided for long-term surgical implants. Surface imperfections on the stainless steel are generally the cause of pitting, from which stress-corrosion cracks are sometimes propagated.

Jan 11, 1976

By J. A. L. Napier

An essential requirement for the planning of the global capacity of a mine is a knowledge of the functional relationship between the production level and the capital expenditure necessary to establish that level. An underlying mechanism connecting capital expenditure and mine production capacity is proposed in terms of a characteristic profile of the expenditure that both precedes and succeeds production expansion. By the assignment of a representative shape to this profile, the capital expenditure of individual mines can be modelled. The empirical values describing the characteristic profile are computed for a number of gold mines, and an attempt is made to explain variations in the model coefficients from mine to mine in terms of physical parameters such as shaft depth, shaft concentration, and average rate of depth increase during the life of the mine.

Jan 1, 1981

COUNCIL FOR 1988/89 President C.E. Fivaz President-elect Dr O.K.H. Steffen Senior H.G. Mosenthal Vice Presidents Junior R.D. Beck Immediate Past President B.C. Alberts Honorary Treasurer Dr H. Wagner

Jan 1, 1989

COUNCIL FOR 1990/91 President H.G. Mosenthal President Elect RD. Beck Senior J.P. Hoffman Vice Presidents Junior Or H. Scott-Russell Immediate Past President Or O.K.H. Steffen Honorary Treasurer OrH. Wagner

Jan 1, 1991

Council for 1995/96 President D.A. J. Ross-Watt President Elect Dr N.A. Barcza Vice Presidents Senior R.P. Mohring Immediate Past President J.A. Cruise Junior J.R. Dixon Honorary Treasurer J.A. Cruise

Jan 1, 1996

[Council for 1993/94 President Dr H. Scott-Russell President Elect J.A. Cruise Vice Presidents Senior D.A.J. Ross-Watt Junior P.D.K. Robinson Immediate Past President J.P. Hoffman Honorary Treasurer J.A. Cruise]

Jan 1, 1994

By E. F. W. Buermann

This paper, which is meant to be read in conjunction with the other papers on the Grootegeluk Coal Project in this Issue (J. S. Afr. Inst. Mm. Metal/., vol. 82, no. 12. Dec. 1982) deals with the extent to which civil-engineering infrastructure had to be provided for that project, near Ellisras in the Transvaal.

Jan 1, 1982

By G. T. G. Emère

The Harmony Gold Mining Company Limited employs approximately 29 500 people, including 27000 Black workers recruited from areas both within and beyond the boundaries of the Republic of South Africa. The problems arising from the control of this diverse and complex labour force have led to the need for a fully computerized labour control system. This paper describes how, with the aid of an extensive interrelated network of satellite minicomputers, together with ancillary peripheral user terminals and printers, the management of Harmony Gold Mine intends to meet these problems.

Jan 1, 1983

Council for 1998/99 President R.P. Mohring President Elect J.R. Dixon Vice Presidents Senior M.H. Rogers Junior Dr L.A. Cramer Immediate Past President Dr N.A. Barcza Honorary Treasure J.A. Cruise Members of Council J.P.W. Bennie E.G. de Villiers A.A.B. Douglas F.M.G. Egerton R. Graham Dr R.G. Gürtunca Dr R.V.R. Handfield-Jones P.J. Knottenbelt R.G.B. Pickering* P.S. Piper Prof. R.F. Sandenbergh Dr T.R. Stacey D.J. van Niekerk P.J. Venter J.C. Viljoen

Jan 1, 1998

[Council for 1994/95 President J.A. Cruise President Elect D.A.J. Ross-Watt Vice Presidents Senior P.D.K. Robinson Junior Dr N.A. Barcza Immediate Past President Dr H. Scott-Russell Honorary Treasurer D.A.J. Ross-Watt Members of Council J.P.W. Bennie Dr L.A. Cramer Prof. R.J. Dippenaar J.R. Dixon A.A.B. Douglas F.M.G. Egerton Prof. R.H. Eric B.R. Fleetwood Dr M.A. Ford Dr R.V.R. Handfield-Jones P.J. Knottenbelt R.P. Mohring K.C. Owen M.H. Rogers K.A. van Gessel P.M.T. White]

Jan 1, 1995