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By A. A. Hazell

Mine management by objectives by A. A. Hazel The procedure of setting production targets is illustrated in Appendix I of the paper. This procedure is intended only as a guide although the standards on which it is based were established by work studies and found subsequently to be well within the limits of a trained crew.

By G. Paul

The mechanism of nodular crystallisation of graphite in the production of spheroidal cast Iron is not fully understood. The work reported In this paper confirms that in cast iron melts having a high Interfacial tension against the environmental atmosphere, the graphite tends to crystallise in nodules during solidification. The Influence of Interfacial tension between melt and solid graphite is similar.

By C. M. Sellars, W. E. Stumpf

SYNOPSIS The effects of concurrent recovery, prior creep deformation and concurrent high temperature fatigue on the coarsening of some carbides in steels have been studied. It was found that concurrent recovery enhances the coarsening rate by orders of magnitude and prior creep deformation causes an enhancement of about two times. Finally, concurrent fatigue causes an initial greatly enhanced coarsening rate but after prolonged cycling dissolution of the carbides occurs.

COLLOQUIUM PRACTICAL APPLICATIONS OF INSTRUMENTATION IN THE MINING AND METALLURGICAL INDUSTRIES Rapporteur: J. Laschinger A colloquium and general meeting of the Institute held jointly with the Instrument and Control Society of Southern Africa at Kelvin House, Johannesburg on 18th October, 1972, had as its theme "Practical Applications of Instrumentation in the Mining and Metallurgical Industries" Dr J. P. Hugo (President) was in the chair and about 200 members and visitors were present.

By P. van Niekerk, V. J. Solomon

Improvements in the drilling and blasting techniques used in the stopes of narrow reefs have caused the clearing of broken rock to become the major cause of delay in the achievement of a regular cyclic operation. This paper discusses the development of a scoop in accordance with a predetermined set of performance parameters. The test results obtained to date have shown that the basic objectives have been achieved within tolerable limits of variation.

Jan 1, 1979

By M. G. Demmer

South Africa ranks among the top three mineral producing countries in the world, and yet the country's teaching and student population have a very limited knowledge of the mining and metallurgical industry. This is probably one of the major reasons why so few scholars elect to study mining-related disciplines at local universities, or to consider a career in the industry. Small mines Much interest in the development of small mines has been evident in the past few years, with junior companies taking the bull by the horns and moving in where larger companies found it uneconomic to tread or, indeed, where large companies are foresighted enough to see the advantage of smaller operations. Examples of small mines are to be found from Europe to Australia, in the Americas, and in

Jan 1, 1986

By R. Hemp

The first part of this paper describes the collection of barometric pressure measurements in a mine and their statistical analysis, which shows the effect of variations in barometric pressure, both on the primary emissions of methane gas into the workings (whether from fissures or from the surrounding strata), and on the flow of air to and from large unventilated, or poorly ventilated, areas. The second part of the paper deals with a study, based on computer simulations, of leakage flows of air into and out of sealed areas, and the reduction of such flows by the use of adequate seals.

Jan 1, 1994

By H. J. E. Hamel

Some aspects of the deformation behaviour and temperature rise during instantaneous compression loading of high purity aluminium By H. J. E. HAMEL The influence of deformation speed on the deformation behaviour of high purity aluminium was investigated. By varying the initial height-to-diameter ratio a considerable influence on the deformation behaviour could be noticed. Lubrication of the specimen end faces was found to have an influence on the flow behaviour and on the roughness of the specimen interface at pressing platens. The results of temperature measurements during deformation agree with work-hardening behaviour of the specimens. Flow curves calculated with the measured temperature rises do not agree with results obtained at lower strains by other workers. The possible reasons are discussed.

By A. L. Painting

A study of the end effects in specimen cores under compression tests, with a view to the elimination of these effects by A. L. PAINTING (Student) It is well known that a cylindrical rock specimen tested under uniaxial compression in conventional fashion is subject to end effects; that is, towards the end of the core, the stress and strain distribution becomes non-uniform. The experiment described illustrates such end effects with an aluminium core between steel platens. An attempt was then made to nullifythese effects by compressing the core between pads of mercury. The resulting stress and strain distribution was significantly more uniform, but a slight over-correction was introduced.

Jan 4, 1974

By L. Cornish, P. A. Olubambi, J. H. Potgieter

Four 22%Cr series duplex stainless steels alloys containing varying nickel contents of approximately 5, 7, 9 and 13% were melted in a vacuum induction furnace, hot rolled, solution annealed and water quenched. Their corrosion behaviour was investigated in sulphuric acid and sodium chloride solutions using a potentiodynamic polarization technique. Increasing nickel contents have appreciable influence on their corrosion behaviour. Polarization curves show similarities in the uniform corrosion behaviour of the alloys in the solutions and a significant difference in their pitting behaviour in chloride environments. Alloy 2209 generally exhibited highest resistance to uniform corrosion while 2213 displayed distinct and best pitting corrosion resistance. Their corrosion behaviour were attributed to the influence of nickel on phase modification, microstructural refinement, and the probably types of films formed in different environments. Keywords: Duplex stainless steel; Nickel; Microstructure; Phase modification; Corrosion

Jan 1, 2006

By D. S. Loubser

The technique of backfilling in the gold mining industry is dependent on the dewatering of slurry to form a solid support system. In many cases flocculants are added to the slurry to increase the rate of dewatering. To ensure that a stable support is obtained it is important that the chemistry, application and limitations of these flocculant additives are understood. Flocculant additives have to be added at a point where minimum shear will occur. (Shear occurs when a flocculant is exposed to excess energy resulting in breakdown, of the floc.) To ensure that optimum results are obtained it is important that personnel involved are trained to use the flocculant additives and dosing equipment correctly.

Jan 1, 1988

By L. A. Vermeulen

Electronic circuits were developed and successfully utilized to record, store, and continuously transmit to a remote station physical information relating to the impacts of pebbles on the shell liners of an industrial pebble mill, and of electrical conduction in the mineral pulp. The information was obtained by the instrumentation of some of the bolts that are used to clamp the liner blocks and litter bars to the mill shell. The features associated with the impact and conduction signals have been interpreted, and it is shown that such signals can lead to continuous measurements of the volume of the load in an industrial mill. Information is given regarding the angular distribution of direct impacts of the pebbles onto the shell liners, the power required to promote impacts, the amount of material in flight, the impact velocity, and the average number of direct impacts with the shell liner that any given pebble undergoes in unit time in the given mill.

Jan 1, 1984

By G. Whittle

An important aspect of the project evaluation process is the achievement of a clear and quantitative understanding of the primary drivers influencing project value and risk. A business scenario-based approach is required to ensure that the project meets value and risk hurdles over the short, medium and longer term. Adopting an optimising approach can aid significantly in the development of a project concept into a business that is optimal and sustainable in the longer term. Through the application of case studies, based on work performed with various mining organisations during the last five years, this paper will demonstrate how project value and robustness can be optimised. Experience has demonstrated that applying this approach results in significant value improvements and risk reduction - primarily by application of a rigorous, fact-based analysis and optimisation process that rapidly increases management team understanding and insight of key driver of value and risk.

Jan 1, 2007

By N. Saldía, C. Riveros, R. Hills, S. Barrera

The transport of tailings composites provided by different sources is a field of study where a limited amount of research has been conducted. Nevertheless, such systems are important sources of operational difficulties, especially in the case of high clay content tailings. The case presented in the present paper consists of a free surface flow pipeline transporting a composite of two different tailings with high clay content. It has presented operational difficulties such as partial blockages and upstream box and air intake overtopping events. In the present paper, the causes of these difficulties are identified. These include lack of complete mixing of the different tailings, multi-layered flow with low velocity and high yield values with high frictional losses. The pipeline characteristics and performance are analysed in three stages: design, initial operation and enhanced operation, the latter accomplished by means of increasing turbulence in the box located upstream from the pipeline. The last section of the pipeline and another distribution pipeline system located downstream from the pipeline have performed well. The cause of different behaviour of both systems is also assessed.

Jan 1, 2007

Project evaluation is completed through individual studies covering technical and financial aspects of the mine to market. These studies are completed at various levels of detail depending on where the project evaluation is in the project's life cycle. The competency of the studies varies in relation to the quality of data, level of the skills employed, control, management and reporting structure. The focus of this paper is managing elements of the study, looking at the cost of opportunity to influence the project, against the value added. Selection of the study manager and study teams is central to getting an integrated project evaluation addressing the correct issues completed on time. Retention of key personnel can reduce rework which, in turn, can reduce time and cost impacts. It is important to have a work breakdown structure at the outset so that the study teams have a common numbering and naming system that will integrate areas, equipment, budgets estimates and accounts. Having set up the evaluation groups and provided training in the study procedures, understanding the scope and schedule are vital elements in producing a project evaluation that addresses the opportunities and the risks of the final project. Arriving at an accurate capital budget requires integration of the research controlled through common systems. Project evaluation process must also address how the project is to be delivered.

Jan 1, 2007

By P. De Kock

Strategic mine planning is concerned with the decisions that determine the value of the business, while tactical planning deals with the tasks to realize that value. When tasked with formulating a strategic mine plan, the mining engineer often turns to commercially available software. However, these software packages have limited applicability to the RBM situation. Adopting a simpler, back to basics approach founded on a deep understanding of the economics of the orebody has the advantage of providing a clear logic to guide tactical planning. By creating a coherency between strategic mine planning, and tactical planning the likelihood of successfully executing the plans and attaining the value promised by the strategic plan is increased. This paper describes the reasons why RBM embarked on a strategic mine planning process, the rationale of choosing the process, and the process itself.

Jan 1, 2007

By J. Martinovic

The large proportion of gangue minerals present in platinum bearing ores in South Africa provides challenges to the flotation and down stream processes. In order to take effective measures to reduce their recovery in flotation an understanding of the mechanisms and factors influencing their behaviour is needed. Typical gangue minerals are pyroxene, feldspar, quartz, chromite and talc. Of these, talc is a naturally hydrophobic mineral and although it is present in relatively small quantities, it has a disproportionate effect as it has a strong froth stabilizing effect, increasing the recovery of other gangue minerals by entrainment. Talc recovery is effectively reduced with the addition of polymeric depressants. Although the other gangue minerals are assumed to be hydrophilic and their recovery by entrainment is expected to follow the water recovery, there is some evidence that they may be activated by the typical reagent suites used. Reagents such as copper sulphate, added as an activator, and collectors are used to selectively induce hydrophobicity on the sulphides. It has been shown that some of these gangue minerals can be activated. This research work investigates whether inadvertent copper activation is mineral specific and evaluates the mechanisms and factors affecting the reversal of activation with the addition of the depressants using electrokinetic measurements, adsorption and microflotation tests. Results are presented that show that the selected minerals do respond differently and that the reversal of activation is dependent on mineral type, depressant type, dosage and ionic strength of the electrolyte.

Jan 1, 2004

By E. Hakami

The objective of the study was to estimate the largest shear displacement that could be expected on a pre-existing fracture located in the repository area, due to the heat release from deposited waste. Two-dimensional numerical analyses using UDEC have been performed. The maximum shear displacement, at the fracture centre, amounts to 0.2 – 13.8 cm depending on fracture parameters. The fracture extension, friction angle and shear stiffness are found to be the most important. Le but de cette étude est de déterminer le déplacement maximal en cisaillement qui puisse se développer le long d'une fracture préexistante en réaction à la chaleur dégagée par les déchets radioactifs enfouis dans la roche. Les analyses numériques ont été réalisées à l'aide du code 2D UDEC. Le déplacement maximal en cisaillement enregistré au centre de la fracture varie entre 0.2 et 13.8 cm en fonction des propriétés de la fracture. L'ouverture, l'angle de friction et la rigidité au cisaillement semblent avoir une influence dominante sur les résultats. Zielsetzung der Studie war die Abschätzung der maximalen Scherverschiebung, die auf einer innerhalb des Endlagergebietes existierenden Rissfläche infolge der Wärmeabstrahlung des eingelagerten Materials zu erwarten war. Es wurden zwei-dimensionale numerische Berechnungen mit UDEC durchgeführt. Die maximale Scherverschiebung im Zentrum der Rissfläche beträgt 0.2-13.8 cm, abhängig von den Risseigenschaften. Dabei hat sich herausgestellt, dass Rissgrösse,Reibungswinkel und Schersteifigkeit den grössten Einfluss haben.

Jan 1, 2003

By J. W. Klokow, S. L. Mulder

Early removal of the shaft reef is usually considered necessary on deep level South African gold mines to avoid damaging stress build-up associated with traditional shaft-protection pillars. In the case of the relatively shallow Beatrix Gold Mine it was largely motivated by early access to ore and the consequent earlier return on invested capital. A number of options were considered to protect the shaft from possible damaging stress changes and to minimise deformations in the shaft-reef area. Numerical modelling was used to evaluate the options and to quantify as accurately as possible the likely deformations to be accommodated by the shaft steelwork designs. The option chosen was a combination of strategically placed satellite pillars and yield pillars, and backfill. Following the mining of a small inner cut during the shaft sinking process, full-scale mining is progressing away from the shaft. Suitable instrumentation has been installed to monitor deformations associated with the shaft reef removal. Enlever rapidement le filon du puits est en général considéré nécessaire dans les galeries de fond des mines d’or sud-africaines pour éviter l’accumulation nuisible de contraintes associée aux piliers de protection de puits traditionnels. Dans le cas de la mine d’or Beatrix, relativement peu profonde, l’enlèvement était motivé en grande partie par l’accès rapide au minerai et par conséquent un profit plus rapide sur l’investissement. Un certain nombre d’options furent considérées pour protéger le puits contre les changements de contraintes potentiellement nuisibles, et pour minimiser la déformation dans l’aire puits/filon. La modélisation numérique fut utilisée pour évaluer les options et pour quantifier aussi précisément que possible les déformations probables que la conceptualisation du puits devrait prendre en compte. L’option choisie fut une combinaison de piliers satellites placés à des points stratégiques avec des piliers de protection, et terre de remblayage. Pendant le fonçage de puits une petite coupure intérieure fut exploitée, et maintenant l’exploitation à grande échelle, au-delà du puits, est en cours. Les instruments nécessaires ont été installés pour surveiller les déformations associées à l’enlèvement du filon du puits. Die frühe Entfernung des Riffschachtes wird normalerweise bei südafrikanischen Tiefbaugoldmienen als notwendig erachtet um den zerstörende Druckaufbau zu vermeiden, welcher mit traditionellen Schachtschutzpfeilern verbunden ist. Im Fall der verhältnismäßig flachen Beatrix Goldmine war es hauptsächlich vom frühen Zugang zum Erz und dem konsequenten frühen Rückfluß des investierten Kapitals motiviert. Eine Anzahl an Optionen wurde erachtet um den Schacht vor möglichen zerstörenden Druckänderungen zu schützen und Deformationen im Riffschachtbereich zu minimieren. Um die Optionen zu bewerten und mögliche Deformationen so genau wie nur möglich quantitativ darzustellen die von den Schachtstahlkonstruktionen aufgenommen werden müssen, wurden numerische Modelle verwendet. Die gewählte Option war eine Kombination aus strategisch plazierten exzentrischen Pfeilern und Schutzpfeilern sowie Hinterfüllungen. Nach dem Vortrieb eines kleinen inneren Einbruches während des Abteufens wird der Vollvortrieb vom Schacht weg vorgenommen. Um die Deformationen, die mit der Riffschachtentfernung verbunden sind zu überwachen, müssen geeignete Instrumentenausrüstungen installiert werden.

Jan 1, 2003

By D. P. Power

The development of an accounting code for the metallurgical industry has been debated for many years. Following the series of tumultuous economic events in the nineties and earlier this century that have affected business, there was much need for legislation to be passed to minimize potential risk. One of the consequences to affect the mining industry was the enhancement of existing geological codes for reporting. In parallel the sponsors of AMIRA have taken the brave step to develop a generic code for metal accounting that embraces the full gamut of industry. In this paper the code will be reviewed in the context of metallurgical accounting as it applies to coal preparation. This paper provides the background for this development and an insight into the mechanism for the debate for the generation of this code. The key elements of the code as it applies to the coal industry are explained but most importantly the key opportunities are highlighted.

Jan 1, 2010