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By M. J. Little

Potgietersrust Platinums Ltd is Anglo Platinum?s only open pit operation and annually extracts 57 million tonnes of rock from 2 open pits. Over the past 3 years ~220 km of exploration drilling has been done, ~1000 km of rock face have been exposed for face mapping and over 7000 laboratory and field tests have been conducted. This has produced large amounts of geotechnical data to be utilised for feasibility studies, initial slope design and ongoing slope optimisation. It was necessary therefore to develop geotechnical databases to manage the vast amounts of data collected. SABLE and MineMapper 3D databases were created for logging and mapping respectively, with rock testing data incorporated into both. A pit inspections database was developed in MS Access and the existing groundwater and slope monitoring database was improved. The databases were linked to AutoCAD and Datamine to ensure that the latest geotechnical data is used for planning, draughting and modelling. The use of geotechnical databases ensures that no data is lost, standards are maintained and analysis can be easily performed. This increases the confidence of the analysis and allows the geotechnical engineers to optimise slope designs and blast designs on a regular basis. This reduces the risk of slope failure thus making the open pits more economical and safe.

Jan 1, 2006

By G. S. Littlejohn

In anticipation of the flooding of an adjacent dolomitic groundwater compartment, five rough parallel sided boundary plugs at 58 and 50levels have been designed to resist safely hydrostatic heads of 1500and 1250 metres, respectively, over a service life of 100 years. Following a description of the engineering properties of the surrounding rocks, the paper details the design considerations relating to structural length and strength, hydraulic gradient, rock mass watertightness, constituent materials of mortar intruded concrete, pregrouting of permeable discontinuities within the surrounding rock mass, a bentonite barrier to resist aggressive mine water, plug tightening and design performance requirements. Routine quality control tests include permeability of the rock mass, fluidity, bleed and strength development of the intruded mortar, and temperature of the intruded concrete during curing. A special test programme includes determination of strength and stiffness of cored concrete and rock samples, shear strength of the rock/plug interface and associated in situ contact stress in order toe stimate the load safety factor against plug failure by shear.

Jan 1, 2006

By D. Van Dyk

Horizontal rotating mills are being used all over the world in different mineral and power generation industries. David Brown South Africa, with over 140 years of experience in gear manufacture and design, has been supplying these industries with innovative designs at exceptional quality. The gearing systems associated with these industries are challenged daily with operating conditions that are not always fully understood. Failures are therefore experienced, over time in the industry, which cannot always be fully explained. David Brown South Africa has developed a gear monitoring system, the Intelligent Gearing System, in association with Transmission Dynamics (UK), in order to monitor and analyse these operating conditions in real time. The system has been designed on the principles of Six Sigma, incorporating Design for Six Sigma. The purpose with this system design is to monitor the operating conditions on the pinion, record the information and analyse the data in relation to the rate of fatigue damage to the girth gear and pinion. This is done in real time and unattended. The output from the Intelligent Gearing System can be fed back into the operating system of the mill user, in order to display an alarm for operating conditions exceeding the design criteria as well as information on the rate of fatigue damage due to these operating conditions. When the mill operating and the effect on the fatigue life of the mill gearing components, conditions are better understood, mill users can forecast critical spare holding levels with an increased accuracy. The Intelligent Gearing System also allows early actions to remove reasons for system overloads.

Jan 1, 2006

By D van der Merwe

Tracers of known densities are used world wide in coal processing plants to evaluate plant performance. Tracers are added to the feed stream and are counted after being recovered from the product and discard streams to determine partition curves. The need to recover the tracers can be eliminated by adding radio frequency identification tags to the tracers. Readers mounted on the product and discard streams record the passing RF tracers and produce the partition curve instantly. Tests were performed with three different shaped tracers at different collieries on cyclones ranging from 510mm to 800mm in diameter. Sink and float analyses of coal samples were used to compare conventional partition curves to partition curves obtained by using RF tracers. The average amount of tracers recorded was 78% of tracers in the feed. The results indicate that the stone shaped tracers represent the results from the sink-float analyses the best. The results suggest that RF tracers can be used to evaluate cyclone circuits in the coal industry and will make it possible to evaluate a coal circuit?s efficiency without stopping a plant and waiting for laboratory analyses. Keywords Coal tracers, partition curve, radio frequency tracer, RFID

Jan 1, 2006

By D. Brazier, W. Laing, D. Nixon

Keywords: Pyrometallurgy, furnace, smelter, copper, Palabora The Palabora copper smelter has operated for the past 38 years, treating concentrates produced at the mine site. Palabora has reduced captive material by almost 40 per cent with the transition from a large open-cast to a smaller underground mine. The smelter and refinery complex was designed to treat 120 kt contained copper units per annum, with the underground only supplying 70 per cent of the feed. The agreed strategy was to import enough concentrates to maximise production and reduce operational unit costs. This transition has presented the Palabora management with new challenges both in technical and financial aspects.

Jan 1, 2006

By Chris Ringas

The safe operation of gas transmission pipelines is increasingly coming under the spotlight. Increasing environmental pressure is also forcing pipeline owners and operators to ensure the integrity of their pipelines. The integrity of a pipeline is usually determined using intelligent pigging, often referred to as In Line Inspection (ILI). However, in many cases, gas pipelines cannot be pigged for a variety of reasons. The National Association of Corrosion Engineers (NACE) has recently published Recommended Practice (RP) 0502, referred to as the External Corrosion Direct Assessment (ECDA) Methodology to assist pipeline owners with assessing the condition of pipelines that cannot be pigged. 2. External Corrosion Direct Assessment - NACE RP 0502 The ECDA Methodology is conducted in four phases as follows: ? Pre-Assessment ? Indirect Inspection ? Direct Examination ? Post-Assessment In the Pre-Assessment Phase, all the relevant historical and current data relating to the pipeline in question is reviewed. This covers pipeline, construction, soils/environmental, corrosion control and operational data. The aim of the Pre-Assessment Phase is to determine whether ECDA is feasible, and if so, to define the ECDA Regions and finally to select the Indirect Inspection Tools that will be used for each region. Typical overline techniques used for overline surveys include the following: Voltage gradient surveys ? DCVG or ACVG

Jan 1, 2006

By J. Morkel

During research on mainly the weathering of kimberlite, it became evident that its mineralogical composition is an important factor in the complex process of physical and chemical disintegration. The mineralogy of tuffisitic kimberlite breccias from two localities, the Cullinan and Venetia mines, is compared with special reference to the occurrence of associated clay minerals. The clay mineral composition influences the engineering properties of these rock types. It is illustrated how the presence of swelling clay components can be confirmed by ethylene glycol treatment and chlorite minerals by heat treatment using X-ray diffraction. Smectites are present in both tuffisitic kimberlites, dominant at Venetia while chlorite is more frequent at Cullinan. More tuffisitic kimberlite breccias samples from venetia were also characterized. It was found that kimberlite disintegration is correlated with the presence and abundance of smectite.

Jan 1, 2006

By D. J. H. Walker, W. H. Gibson

The inclination of any pit wall composed of stacks of benches is limited by the overall quality and structural complexity of the rock mass in which the slope is situated. For a bench stack angle that satisfies the stability criteria, various combinations of bench height, bench face angle and berm width can be used in the slope design. The bench face angle and berm width geometries must be chosen to fit the bench stack angle but must provide a berm that will be capable of catching the volume of failed wedge material from the bench faces above. Other considerations for bench height and berm width are equipment size, ore selectivity and blasting design. This paper studies the effects of different slope configurations on slope performance as it relates to wedge stability, volume of rock safely contained on berms, and rockfall. Optimisation of the geometry is carried out based on the need to minimise the volume of failed material which limits the effectiveness of the berm. This will reduce the number of rocks that can continue to fall further, reaching geotechnical safety berms or pit ramps, that put safety of personnel and equipment at risk. For general study it is most effective to investigate and compare the performances of each of a wide range of geometrical combinations of bench height, bench face angles and berm widths that fit a variety of different bench stack angles. These analyses were conducted for a predetermined bench stack height and three different bench stack angles.

Jan 1, 2006

By P J. Grobler

The current commodity boom is depleting the ore bodies at a rate not seen in the past. As the existing ore bodies get depleted, only the more inferior bodies are left for exploitation. This places an emphasis on beneficiation to upgrade the lower grade ore to high-grade feedstock for downstream processes. This paper discusses the role of dense medium separation in this quest for high-grade feedstock for the future. It covers the production and utilization of ferrosilicon and gives a future perspective of the technology. It concludes about the way ahead and the challenges facing the processing fraternity and mining industry.

Jan 1, 2006

By E de Villiers

Several methods exist by which the capacity of a dense media separation (DMS) plant can be improved: 1) Increase the feed rate in spite of efficiency 2) Replace with bigger equipment 3) Add whole new module 4) Replace total plant 5) Change over to four shift/ seven days per week roster 6) Replace with alternative process 7) Increase the availability and utilization Options 1 ? 6 have varying degrees of cost implications. The seventh option would seem to be the easiest. Normally it is also the function of the plant operating and maintenance team to maximize this. Usually higher operating and maintenance cost are associated with an increase in these parameters. A general principle that is applicable to plants and systems is that as the complexity increases, the total availability decreases. By simplifying the flow line it may be possible to reduce cost while at the same time increase the availability and utilization. The typical standard DMS flow line contains components that compensate for the variance in pump performance or for the inefficient recovery of ferrosilicon with additional equipment. Things have changed though: 1) Advanced electronic control and monitoring is possible 2) More efficient magnetic separators are available 3) New more user friendly densifiers are available ORIGINAL FLOW LINE In principle the process consists of four flow lines or streams 1) Ore flow ? the feed is divided into a waste and product stream by means of the separating vessel

Jan 1, 2006

By H. Immink

Keywords: Kyoto Protocol, carbon credits, global warming, energy, auditing Climate change is nowadays being taken increasingly seriously, and the link between global warming and the carbon dioxide released in the generation of energy is coming under increasing scrutiny. The Kyoto Protocol was signed in 1997, after five years of negotiation. So far, about 84 countries have ratified this agreement, under which terms developed countries have strict targets linked to their 1990 level of emissions. However, ?greenhouse gas? (such as carbon dioxide) emissions continue to rise alarmingly. According to the World Resources Institute, greenhouse gas emissions in the USA increased 13% from 1990-2002, while Australia recorded a 22% increase. In contrast, the European Union, a Kyoto signatory, has seen a small decline in its emissions during the same period. This is led by the UK and Germany, who reduced their emissions by 15% and 19% respectively. The concept of ?carbon credits? provides a funding mechanism for companies in the developed world to compensate for some of their CO2 emissions by paying companies (trading credits) elsewhere in the world to undertake projects to bring about reductions in emissions. In the southern African mining industry, it will be possible to get refunded for undertaking voluntary emission-reduction projects. Concern about the environment is creating business opportunities. A preliminary calculation has shown that various projects in South Africa (those in the pipeline, with quite a high likelihood of coming off) could earn a combined total of about R2.5-billion, under the initial phase of the Kyoto Protocol's carbon-credit scheme, which allows developed-country companies to trade credits with developing countries. A number of local companies are planning projects that could comply with the Clean Development Mechanism (CDM), in which they will implement techniques to achieve certified emission reductions (CERs) of greenhouse gases. In order to prevent abuse of such a system involving vast sums of money, vigorous audits need to be carried out. A company has to prove it has made real changes and is not simply conducting business as usual under a cloak of claimed environmental improvements. PricewaterhouseCoopers has applied to become one of only a few international agencies that will be accredited to conduct validation and verification of the credits, by auditing what is called the ?designated operational entity?. An independent validator needs to confirm that the project meets the strict requirements of the Kyoto Protocol. The company has to demonstrate that it?s not business as usual. So, if you refurbished every five years, the next refurbishment is not a good CDM project, unless you can demonstrate that you will do something beyond the maintenance - that is what can be registered. So, Kyoto intends to get additional projects going, and the money for that is actually quite good - prices of 14 euros per ton of carbon dioxide not emitted have been seen. The price depends on who takes the risk for non-delivery if a project doesn?t deliver the emission reductions on time. The highly energy-intensive South African mining industry is heavily dependent on coal. There should be many opportunities for the pyrometallurgical industry to come up with creative ideas to reduce emissions, and there is now an additional financial incentive to encourage this. Companies can actually get money in return for doing these types of projects, in addition to the contribution to corporate social responsibility.

Jan 1, 2006

By A. S. Macfarlane

Mineral resource management (MRM) practice has developed in South Africa over the course of the last ten years, with the purpose of integrating previously isolated technical functions into a value chain aligned, process organization, responsible for mine planning and optimization. The implementation of MRM within various companies has met with varying degrees of success, often resulting in incremental improvements in the planning process and, conversely, often becoming the scapegoat for poor delivery on plans and projects. The reason for this has been, amongst others, a lack of a suitable metric to define the success rate of MRM in the business at hand, in terms of its contribution to the bottom line. This paper is the result of extensive research by the author into this subject, which has resulted in the conclusion that economic value added is an appropriate measure that will lead to real optimization and value creation in mining companies, if applied within a new, holistic model

Jan 1, 2006

By Darelle T. Janse van Rensburg

Some of the more recent developments in Paint Technology are solvent free materials. These coatings have mainly been formulated to overcome the negative attributes of solvent-based coatings, i.e. environmental, safety and health risks, potential for solvent entrapment and osmotic blistering, as well as the formation of micro-pores during the curing process. Two solvent free liquid epoxy coatings have been used extensively on power generation plant. However, very little is known regarding their long-term performance under different exposure conditions, as well as whether these coatings actually perform better than their solvent-borne counterparts. In addition, solvent free materials are generally used where outage periods are restricted and coatings need to be applied within a very short period. Though these materials have reportedly much shorter curing times than other conventional solvent-borne coatings, little is known regarding their limits with respect to maximum film thicknesses and being put into service while still being wet/partially uncured. The latter has become common practice at many power stations in the past two years or so. In addition, the application and curing methods of solvent free materials are different to that of solvent-borne materials, and may require equipment and application process changes. This paper covers the application and performance properties of solvent free coatings in comparison to solvent-borne materials primarily intended for immersion service. Numerous coatings were evaluated under immersed static and cyclic hydrostatic pressures. Other tests included short curing / early immersion tests, dry-to-touch and dry-through curing times, adhesion tests, surface tolerance tests, etc. The results show that the solvent free materials have clear benefits with respect to safety, health, environmental and long-term performance, but will be more difficult to apply compared to solvent-borne materials.

Jan 1, 2006

By A. J. Potgieter, C. Hill, A. Humpel, D. S. Magudulela, V. Scholtz, A. Coetzee

Keywords: Pyrometallurgy, long steel products, coke, sinter, blast furnace, steel plant Located in Northern KwaZulu Natal, Mittal Steel South Africa Newcastle works produces roughly 1.8 million tons per annum, supplying long steel products, locally and overseas. The great extent of local raw material availability and low conversion cost ensures that Mittal Steel South Africa is among the lowest cost, high quality producers of steel. MSSA Newcastle works can be subdivided into two main sections: The iron making side, comprising the coke ovens, sinter plant and blast furnace, and the steel making side, comprising the basic oxygen furnace, ladle furnace, continuous casters, and the medium, rod, and bar mills.

Jan 1, 2006

By H Möller

The purpose of this paper is to give an overview of the corrosion behaviour of steel in seawater. It is shown that the corrosion products (oxy-hydroxides and calcareous deposits) that are formed during corrosion in seawater have a significant effect on the corrosion behaviour of steel. The chemical composition of the steel determines how protective the oxy-hydroxide corrosion product is. The composition of the seawater influences the nature of the calcareous deposits. This needs to be considered when artificial solutions are used to simulate the corrosion behaviour of steel in seawater. A 3.5% NaCl solution is used frequently for this purpose, but because no calcareous deposits can be formed in this solution, erroneous results in terms of corrosion rates are obtained. The more complex ASTM D1141 artificial solution can be used to include the effects of ions other than Na+ and Cl- in synthetic seawaters. The importance of these other ions on the formation of calcareous deposits is discussed. Keywords: Steel, corrosion, seawater, calcareous deposits, oxy-hydroxides

Jan 1, 2006

By P. R. Brenchley

Main ore pass systems should last the life of a mine, and too often expensive and hazardous remedial measures are required to repair a damaged ore pass in an attempt to extend its life. In order to maximize the life expectancy of all ore passes at Moab Khotsong, ?wearing blocks? and ?softer support? systems, combined with basic rock engineering principles, have been implemented. Failure of an ore pass can have severe financial implications, both indirectly because the ore pass cannot deliver the broken rock either from level to level or directly in the shaft ore pass system to the required level for tramming to take place, and directly due to the cost of the repair work that is required. Several factors need to betaken into consideration so that production interruptions are eliminated or minimized. Investigations of damaged ore passes at Moab Khotsong and surrounding mines revealed some interesting mechanisms of damage, and some innovative methods of reducing or eliminating the damage have been implemented at Moab Khotsong. The system design was based on 30 years, experience in main shaft rock passes. The design was to counteract scaling, hang-ups and dust problems associated with main rock passes, and the objective was to increase the life of rockpasses. These problems, including the initial design aspects to try and eliminate the repair measures, are discussed in detail.

Jan 1, 2006

By R. E. Wilmot

This paper is based on the experiences, over many years, on the part of numerous authors in the South African mining industry and that of the hot dip galvanizing process and its application as a corrosion protection system. The paper sets out the extensive development, financial resources and stringent operating requirements of the South African mining industry. After many years of research and operational experiences, hot dip galvanizing and when necessary, duplex systems, have been found to meet the demanding requirements of this particular industry. The paper sets out the requirements from the standpoint of corrosion criteria and is followed with a practical example; ?case history? where the corrosion protection properties of hot dip galvanizing are demonstrated. This case history traces the early investigation of the expected corrosive conditions to be encountered in a new mining operation (now 10 years on) and concludes with two follow up visits to the mine in order to examine actual performance of the corrosion protection system after ten years in service.

Jan 1, 2006

By M. J. Little

Potgietersrust Platinums Ltd (PPRust) is Anglo Platinum?s only open pit operation. The major slope stability concern at PPRust is rapid, small-scale brittle failure on the west wall of Sandsloot open pit. In order to improve safety and mine more economically, a comprehensive slope monitoring strategy has been implemented. In the last 3 years four new state-of-the-art monitoring systems have been installed namely an ISSI microseismic monitoring system, a GeoMoS automated prism monitoring system, prismless Riegl laser scanners and a GroundProbe slope stability radar (SSR). Groundwater monitoring and visual monitoring have also been improved over the same time period. To complement the visual inspections, SiroVision digital photogrammetry is now used for predicting where future failures may occur. All these monitoring tools provide primary monitoring which is used to identify high risk areas. The SSR is then set up in that area to provide early warning of failure so evacuation can be successfully done. Fault tree analysis has proved that with this comprehensive slope monitoring strategy the geotechnical risk at PPRust is greatly reduced, allowing mining to continue safely and economically in challenging conditions.

Jan 1, 2006

By S. A. Forrest, B. Clarke

Trends in PGM demand?The conference paper will cover a concise analysis of demand trends, which will include the major PGM end-use sectors (autocatalysis, jewellery, glass, petroleum, nitric acid, medical/dental) and will touch on the investment sector. Reference will be made to environmental legislation affecting global emission standards, trends in PGM loadings and the substitutability of platinum and palladium in this end-use sector. Observations will also be made on the jewellery sector, and the development of Chinese and Japanese demand. Trends in primary and secondary PGM supply?Similarly the paper will summarize historic and current global mine supply and primary production trends for PGMs, referencing recent expansions, their deliverability, and other projects coming on line. Consideration will be given to the grade and geology of PGMs worldwide and metallurgical developments. PGMs produced as by-products of base metal production and early PGM recycling estimates will also be appraised. In order to gain a wide-ranging appreciation of the industry?s long-term cost trends of producing virgin PGM metals, the paper will look at the cost and profit dynamics of global production on a regional basis (Western Bushveld, Eastern Bushveld, Northern Bushveld, Zimbabwe, USA, Canada and Russia). Extrapolating tomorrow?s PGM market and forecasting metal prices?Based on established industry trends and market practices Stephen Forrest will conclude by unveiling a variety of thought-provoking extrapolations of today?s and tomorrows platinum, palladium and rhodium markets to conference delegates. Importantly, having highlighted major developing PGM market trends in end-use (specifically on the elasticity of demand to high metal prices), primary and secondary PGM supply trends, in addition to presenting a carefully reasoned forecast of industry supply costs and margin trends, Stephen Forrest will conclude by estimating long-range PGM metal price trends. Other relevant market factors including industrial production, global currency rates and regional political factors will be deliberated.

Jan 1, 2006

By A. Moss

The Palabora Mining Company has successfully extended the life of its operation by developing a 30 000 tpd block cave underground mine below the now closed open pit. The process of transitioning from surface to underground mining has been technically, operationally and managerially challenging. This has been due to a number of factors, in particular, the development of a block cave in a very competent rock mass. The competence of the rock mass is clearly demonstrated in the open pit that preceded the block cave, one of the steepest deep open pit excavations in the world. With cave breakthrough, however, the pit was ?instantaneously? deepened by 400 m causing a major failure of the north-west wall involving close to 100 Mt of waste material.

Jan 1, 2006