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By B. M. Kunar

It is well known that job-related hazards and individual factors influence occupational injuries. However, research involving coalminers has been limited. This case-control study assessed the relationships of job-related hazards and individual/life style factors with injuries among underground coal miners. It compared 245 cases with at least one injury during the previous two-year period with 245 matched controls with no injury. The data were gathered via personal interview and analysed using the conditional logistic model. The significant risk factors were materials handling (adjusted OR 5.15), poor environmental/working conditions (2.63), geological/strata control-related hazards (2.35), lack of formal education (3.00), sleep disorders (1.86), alcohol consumption (2.32), disease (2.23), having a large family (5.40), and risk-taking behaviour (9.40). Machine-related hazards, sleep disorders and alcohol consumption primarily affected workers aged less than 45 years; whereas, environment/working condition-related hazards, presence of disease, smoking, risk-taking behaviour and large family size were more likely among workers aged 45 or over. Keywords: Occupational injuries, sleep disorders, job hazards, alcohol, coal miners

Jan 1, 2010

By F. L. Wilke

The use of operations research techniques and computer models has become entrenched in the mining industry, particularly in the area of mine planning. The paper considers three major areas where increasing efforts are likely to be directed in the future: the integration of multiple disciplines in a single model; the decentralization of computing capacity within a structured network; and the incorporation of sophisticated techniques such as computer aided design and artificial intelligence.

Jan 1, 1987

By V. H. R. Brereton

The gold deposits of the farms Lisbon and Berlyn in the Eastern Transvaal by V. C. H. R. BRERETON* (Visitor) This paper describes the discovery and recovery of gold, over a period dating back to the 1870s. on the farms Lisbon and Berlyn, situated approxim ately 1I km north-east of Pilgrims Rest. where mining ceased in July 1971. 99 years after gold was first discovered in the Pilgrims Rest and Sabie districts. Included in the paper are accounts of the discovery and mining operations of the Lisbon-Berlyn Company from 1884 to 1890. The operations of small companies and syndicates. the superficial winning of gold by diggers, and the encouraging reports of four mining engineers in 1890 are also mentioned.

Jan 11, 1973

The role of research and development In the South African gold-mining industry Presidential Address given by M. D. G. SALAMON, Fellow, Dipl. Eng. (Mining) (Hungary), Ph.D. (Durham) The decision of the gold-mining industry in 1974 to embark on a major ten-year research and development programme was widely publicized at the time. In choosing a subject for this address, I felt almost obliged to use this opportunity to give an account of the progress of this undertaking. On reflection, however, I felt that a simple progress report would not suffice. It seemed important that the programme should be shown in persepective, and that its aims should be outlined to the mining and metallurgical engineering community, many of whom are vitally concerned with the well-being of the gold-mining industry.

Jan 10, 1976

By E. Shavartz, N. B. Strydom

The incorporation of individual cooling in a compressed-oxygen closed-circuit breathing apparatus by E. SHVARTZ, M.Sc. (U.C.L.A.), Ph.D. (U.S.C.) (Visitor) and N. B. STRYDOM, M.Sc., Ph.D. (Illinois) (Fellow) A conventional compressed-oxygen breathing apparatus, which did not include provisions for dehumidification of the inspired air at high environmental temperatures, was tested at these temperatures with and without conductive cooling in the form of 2 kg of pre-frozen ice placed inside the breathing bag of the apparatus. The pre-frozen ice provided conductive cooling of the soda lime and of the chest and abdomen of the subject, who performed moderate work at 50,1 "c. Without cooling, the subject was exhausted after 35 minutes because of a wet-bulb temperature of the inspired air of 46"c. With cooling, the subject finished 2 hours of work. This was possible by keeping the soda lime at a relatively Iow temperature, which resulted in a wet-bulb temperature of the inspired air of only 42 °C after 2 hours, and by conductive cooling of the chest, which resulted in the maintenance of a relatively Iow heart rate and rectal temperature.

Jan 7, 1975

By J. P. Hoffman, A. S. M. de Jesus

Additions of boron have been found to increase the hot workability of stainless steels. Boron forms complex chromium-iron borides, primarily at grain boundaries but also on delta-ferite stringers. This paper describes how a nuclear technique based on the track-etch method was used to distinguish between borides and chromium carbides on grain boundaries and to investigate the distribution of boron in stainless steels. The method was found to be sensitive for boron, and made it possible for boron precipitates to be identified on grain boundaries and interphase boundaries.

Jan 1, 1989

By G. W. Healy

The smelting of calcium carbide has always been plagued by eruptions, too often with serious injury y or loss of life. To find their causes, the author calculated an internal energy balance using 1992 data for CaC2 and CaO, and older data for the remaining items. The heat content of the charge, and that of the hot gases formed at the reduction temperature, showed that only a fraction of its heat content can be supplied by these gases. Laboratory data on the electrical resistivity of fine mixtures of coke and non-conductive solids were extrapolated to a commercial carbide charge, and then used to calculate the heat produced by current flowing through the mix from the electrode surface to the hearth, which, under favourable conditions, sufficed to bring the charge to 1900 K and higher, at which temperatures reduction could take place.

Jan 1, 1995

By R. R. Mankowski, F. J. Cox

Experimental results are presented on the longitudinal atenuation of a kinetic shock wave traveling along a typical mine hoisting cable. Mathematical curve-fiting of the results established these losses to be exponential and tension-dependent. The reflection and power-transmission coeficients of a typical winding drum were also investigated. The degree of penetration of an incident stress wave onto the coil of cable wrapped round the drum is shown to be governed by a second-degree relationship, and is solely dependent on the acceleration of the cable at the cable-drum interface. Although the investigation is limited to the testing of a single hoisting cable, certain qualitative trends that were identified can be generalized and applied to other types of hoisting cable with diferent geometries, elastic properties, and instalations.

Jan 1, 1986

By R. I. Klintworth

The multi-reef area of Cooke 3 Shaft provides a unique mining challenge on account of the very thin middlings between the pay bands and the marginal values of the reef. It is uneconomic or impractical, because of the excessive heights, to mine the middlings using conventional stoping methods. The development of suitable mining methods is discussed with particular emphasis on the control of water inflow and the policy of not jeopardizing or sterilizing other reef horizons by the mining method implemented. No definite solution is currently available, but with the aid of instrumentation, computer analyses and mechanized mining equipment, the mine continues to attempt to maximize extraction and profits.

Jan 1, 1988

By J-C. Lv, S. Zhao, F-L. Zhang, T. Yan

"To eliminate nozzle clogging during continuous casting of ship plate steel and reduce the calcium addition required, the composition of CaO-MgOAl2O3 inclusions in the liquid phase region must be controlled. Thermodynamic calculations using FactSage show that when the balanced Al content is 0.03 mass %, aCa in the liquid steel is 1–10 ppm, and aMg is 0.01–0.3 ppm; and when the balanced Al content is 0.06 mass %, aCa in the liquid steel is 1–30 ppm, and aMg is 0.05–0.9 ppm. The CaO-Al2O3-CaS inclusions can be controlled in the liquid region below 1600°C at aCa values of 5 ppm, 15 ppm, and 30 ppm, and the balanced Al content should be controlled in the range of 0.001–0.050, 0.005–0.250, and 0.010–0.50 mass %, respectively. Based on theoretical analysis, the refining slag composition should be controlled to 45–53 mass % CaO, 30–37 mass % Al2O3, 6–12 mass % SiO2, and 6–8 mass % MgO. Optimization of the slag system and steel composition can reduce, or even eliminate, the requirement for calcium treatment. The total oxygen content in the slab can be controlled to 15–21 ppm, with typical micro-inclusions ??10 ??m in size, with compositions in the CaO-Al2O3-MgO and CaO-Al2O3-CaS systems. Introduction With the rapid growth in steel output in China and the changes in the macroeconomic environment, competition in the steel industry has become more intense. The technology for economical cleaning of high-grade steel is important for improving product quality and reducing production costs. However, the functions of refining equipment have not been fully taken into consideration, and the combination of refining methods has not been optimized completely. These problems have become a bottleneck, restricting modern steel enterprises from developing an economic clean steel production process. Ship plate steel produced by the converter long process has been selected as the example in this study. The composition of the steel is shown in Table I. This steel is a high-strength low-alloy steel for rolling media and heavy plates, mainly used for ocean-going vessels and other steel structures. The carbon content in the steel is far from the peritectic point, and the crack sensitivity of the slab surface is weak, so impurities and gas content are strictly limited. Therefore, the process route BOF (basic oxygen furnace) – LF (ladle furnace) – CC (continuous casting) needs to be studied."

Jan 1, 2018

By G. D. Schena

The issue of evaluating the economic impact of large mineral projects in developing countries was studied by the use of econometric models. The evaluating system is demonstrated by its application to an example from Namibia. Three-dimensional graphics are used to illustrate the procedures leading to an assessment of the economic effects of the mineral development. The analysis allows the assessment of the overall economic consequences of mineral developments where there is a need to incorporate in the evaluation issues that are broader in scope than the pure financial objectives. Sets of technical coefficients are exploited for the development of input-output models of the productive structure of an economy. The models are refined to incorporate country-specific behaviours. The increased flexibility of the enhanced semi-input-output model permits a more confident investigation of the economy wide effects associated with a new project in the mineral sector of a developing country. Synthetic measures of profitability at market and shadow prices are introduced, and the cost/benefit ratio is used to rank mineral projects according to their economic profitability. The cost is the capital mobilized for the development of the project and for increasing the productive capacity of the related satellite industries. The benefits are identified with the economy-wide increase in value added induced by the project. 80th costs and benefits are initially valued at market prices. Their ratio is likely to be an index of economic profitability superior to measures that concentrate exclusively on the benefit side of projects. To allow for market distortions, the concept of shadow prices is introduced, and accordingly project-related costs and benefits are re-evaluated. A new cost/benefit ratio at shadow prices is recalculated, which is more meaningful to the policy-maker than decision-making based on socio-economic issues.

Jan 1, 1993

By J. Abdollahisharif

Optimal cut-off grade is one of the most critical parameters in open-pit mine design because it defines the ore and waste and thus determines the maximum net present value possible from the mining operation. Although the algorithm presented by Lane (Choosing the optimum cut-off grade. Colorado school of Mines Quarterly, vol. 59, no. 4, 1964. pp. 811-829) is the most common one in the literature, it does assume constant capacities of the mine, processing, and refinery. In this paper, Lane's original algorithm has been modified to consider variable processing capacities in order to determine the optimal cut-off grade in open-pit mines. The new algorithm proposed here is compared to both Lane's original algorithm and to a previous modification that incorporated rehabilitation costs into the cut-off grade estimation. The algorithm proposed here that permits variable processing capacities is shown to be superior for the determination of optimal cut-off grade to both these previous versions. In addition, a computer-based program was developed in Microsoft Office Excel© to calculate the optimal cut-off grade as proposed here.

Jan 1, 2012

By S. R. Xie, S. Gong, E. P. Li, S. S. He, Y. J. Sun, S. J. Li

"Based on the complicated geological production conditions and abnormal strata behavior of the fully mechanized caving face No. 102 in the Xinyang Coal Mine, we analyze the breaking and forming process of distinguishing key block structures in close spaced coal seams. This analysis establishes an integrated mechanical model of these distinguishing structures. Furthermore, the horizontal force TAB generated by downward key blocks A and B is quantified, as is the Pressure PG exerted by key block B on caved gangue. Finally, the interaction mechanism is revealed. Analysis of the results using Mathematica reveal the following: 1. Both TAB and PG exhibit approximately inverse relationships to coal pillar width b; 2. TAB exhibits an approximately exponential relationship with mining height M of which the base is greater than 1; 3. PG exhibits an approximately arctangent relationship with mining height M. Combining these results with field observations, we conclude that the area in the vicinity of supports 100#–120# in the upper area of working face No. 102 is the likely zone of abnormal strata behavior. Thus, this area was classified as a key control area. Based on these results, the graded support control technique is proposed. Application of this technique in the field resulted in a reduction in the rate of hydraulic support system malfunction from 47% to 7% in the key control area. In addition, during times of periodic mining pressure, the roof caving height value never exceeded 0.3 m and the maximum spalling depth never exceeded 0.2 m. Overall, the results indicate that this new technique has markedly increased the stability of surrounding support rock material. IntroductionClose-spaced coal seams are widely distributed in China, and mining proceeds from the uppermost to the lowermost seam (Zhang et al., 2008). In the case of coal seams in close proximity, a particular set of risk factors becomes pertinent. These include disturbance of lower seams during the mining of overlying ones and the decrease in mechanical stability of lower coal seams following repeated movement of key blocks in main coal seam roofs. This inevitably results in behaviour such as heavy wall spalling and support damage to fully mechanized caving faces in lower-lying coal seams, which necessitates a significantly increase in the measures to support surrounding rock material (Zhang et al., 2010; Huang et al., 2013; Xie et al., 2013)."

Jan 1, 2016

By S. A. Abdel Sabour

Strategic decisions in the mining industry are made under multiple technical and market uncertainties. Therefore, to reach the best possible decision, based on information available, it is necessary to integrate uncertainty about the input variables and model financial risk of the project?s merit measures. However, this provides few useful insights to decision-makers unless accompanied by modelling management responses to uncertainty resolutions. It is widely acknowledged that conventional decision-support methods based on static, no-change, discounted cash flow (DCF) techniques such as net present value (NPV) and internal rate of return (IRR) tend to provide inaccurate value estimates. This could mislead the strategic decision-making process and result in significant value losses. This paper aims to model financial risk related to uncertainty about market variables such as metal prices and foreign exchange rates. Other sources of risk that are related, for example, to geology and production costs are not considered in this work. The article outlines a flexible financial model that integrates uncertainty about market variables and management flexibility to react to uncertainty resolutions into mine project valuation using a real-options valuation technique based on Monte Carlo simulation. Significance of information generated from this simulation-based flexible valuation model to the strategic decision-making process is tested using an illustrative case study of a Canadian mining project. The project is a typical multi-metal, open pit mine that produces copper and gold. In this case, there are three uncertain market variables, which are: copper and gold prices and US$/CAN$ exchange rate. Financial valuations are carried out using both the conventional static DCF method and a flexible real-options model. In the flexible model, management flexibility to decide whether to go ahead with the next expansion or terminate production operations is integrated. Results show how the flexible financial model can enhance the decision-making process.

Jan 1, 2009

By R. J. Dippenaar, J. C. van den Berg

This paper describes an investigation into the prereduction of hematite fines in a fluidized-bed reactor as a means by which they can be prepared for direct smelting in a transfered-arc plasma furnace. A single-stage fixed fluidized bed reactor using the in situ gasification of coal was employed. It is shown that the hematite is reduced to magnetite at 1000 QC, the degree of reduction being limited by the inherent shortcomings of a single-stage reactor in which both the gasification and the reduction reactions have to occur. Methods by which the degree of reduction can be increased are suggested. The gasification process was studied in some detail, and three different reducing agents are compared. The dominating effect of the Boudouard reaction on the behaviour of the fluidized bed is clearly illustrated. Non-coking coals of high reactivity are best suited to this process, a finding that would complement the trend away from coke as a metallurgical reducing agent.

Jan 1, 1989

By A. J. Lynch, N. W. Johnson, D. J. McKee, G. C. Thorne

The behaviour of minerals in sulphide flotation processes, with reference to simulation and control. by A. J. LYNCH, Ph.D., N. W. JOHNSON, Ph.D., D. J. McKEE, Ph.D., and G. C. THORNE, B.Sc. (Hons.) (Visitors) In sulphide flotation processes, there are two mechanisms by which particles are transferred from the flotation pulp to the concentrate: adhesion to air bubbles and natural flotation, and entrainment in the froth. The entrainment mechanism is particularly important for particles of non-sulphide gangue, which do not absorb collector. The importance of controlling the recovery rate of water was illustrated in plant testwork in which selectivity between valuable sulphides and sulphide gangue, and between valuable sulphides and non-sulphide gangue, was altered by manipulation of variables affecting the water recovery rate. The two mechanisms should be recognized in the development of a control system. Most of the control schemes in operating plants have concentrated on reagent additions, which affect the natural flotation mechanism. Although control of the chemical environment is clearly of paramount importance in flotation, plant tests have shown that control of the variables affecting the entrainment mechanism is also important.

Jan 4, 1974

By J. P. Beukes

The production of ferrochrome alloy from chromium bearing chromite ores is conducted at high temperature under highly reducing conditions. However, albeit completely unintended, it is impossible to completely exclude oxygen from all high temperature process steps, with the corresponding possibility arising for the generation of small amounts of Cr(VI) species. Certain Cr(VI) species are regarded as a carcinogenic, with specifically airborne exposure to these Cr(VI) species being associated with cancer of the respiratory system. With approximately three-quarters of the world?s viable chromite ore reserves located in South Africa, and annual ferrochrome production approaching almost half of total annual global output, aspects of Cr(VI) generation and control are of particular relevance and importance to the local industry, and naturally to the global industry at large. This paper seeks to examine theoretical and practical aspects associated with Cr(VI)generation (based largely on experience within the local South African industry, but considered to be generally encountered in the broader global industry context), together with mitigating measures that can be applied within the context of the production processes. From the discussions it is clear that significant improvements in various Cr(VI)-related aspects have been made by the South African ferrochrome industry. However, it is also evident that several areas of uncertainty still exist, which require further research in order to better quantify risks and enhance the efficacy of mitigating steps. Keywords Hexavalent chromium, Cr(VI), ferrochrome production, South Africa.

Jan 1, 2010

By A. Hinde, M. H. Moys

Tailings from metallurgical plants, when deslimed with hydrocyclones, provide a valuable source of material for the backfilling of mines. The effectiveness of this material as a support medium is a sensitive function of its particle- size distribution and water content. It is therefore important that the hydrocyclone-classification plants used to prepare the backfill are operated efficiently, and that the effects of feed disturbances on the composition of the backfil are minimized. This paper addresses the problem of the design, control, and optimization of classification plants to satisfy this need. The development of a computer program to simulate the dynamic behaviour of a hydrocyclone circuit of any given configuration is described. The use of the simulator to investigate the relative performance of conventional and innovative control strategies for single-stage and two-stage circuits is discussed in depth. The results of simulation studies are presented that indicate there is considerable scope for improving the performance and cost-effectiveness of backfill-classification plants.

Jan 1, 1991

By D. G. Keefe, I. C. Robinson

In this paper the authors present their views on the actual and potential role of commodity analysis in mining industry. Owing to the dominant influence of the economy on all commodity markets, it is essential that individual commodities are studied not only in depth but within the broader context of economic influences. A commodity unit, which monitors market developments in a wide range of commodities, is well placed to provide the broader perspective in the study of commodity markets. This paper describes some of the specific functions of such a unit. Some of the methods used for price forecasting are described, and the results of price forecasts by different forecasting methods are compared.

Jan 1, 1980

By J. C. Steinhobel

Answers to questions raised at the Symposium on Trackless Mining in Metal Mines Questions by J. O. Steinhobel (1) When rubber-tyred equipment is used for the delivery of stores and items of equipment, how is heavy material-pipes, rails, timber support, ventilation columns, etc.-dealt with? Termination of Membership In accordance with By-Law 7.6.1. of the Constitution of the Institute, the names of the undermentioned members have been removed from the membership register.

Jan 9, 1973