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By D. K. Ingram, P. Jurovcik

The National Institute for Occupational Safety and Health (NIOSH) identified hearing loss as the most common job-related disease in the United States in its 1996 National Occupational Research Agenda. Previous studies by NIOSH have shown that operators of surface drill rigs without cabs are commonly exposed to A-weighted sound levels exceeding 90 dB. During hammer-drilling, A-weighted sound levels exceeding 100 dB were recorded at the operator station. NIOSH collaborated with a local drilling company to design and install a partial cab between the operator and the drill steel in an effort to reduce the sound level at the operator station. Sound level measurements in the field show the partial cab reduces the A-weighted sound level by 5 to 9 dB at the operator’s left ear and 2 to 5 dB at the operator’s right ear while hammer-drilling. This paper briefly discusses the preliminary design of a cab and the testing of materials for construction of the prototype. An explanation of the ideas behind the prototype design and fabrication are covered. Finally, the field test method and results are discussed in detail.1

By Jean-Sébastien Kroll-Rabotin, Éric Climent, Florent Bourgeois

"Falcon concentrators are enhanced gravity separators designed for concentrating fine and ultrafine slurries. The Falcon UF model is unique in that it is dedicated to beneficiation of ultrafines, one key feature being that it does not make use of any fluidisation water. In a former study, we investigated the physical mechanisms that govern the transport of ultrafine particles (in the range 10 to 80 µm) inside Falcon UF concentrators, and concluded that separation efficiency is governed by differential settling. Initially, we derived and published a predictive model of the partition function under dilute conditions. The present paper proposes an extension of the initial model to concentrated ultrafine suspensions for application to industrial scenarios. The paper discusses how hindered settling has been added into the initial model to account for solid concentration effects. The modified model is tested against experiments carried out with a laboratory scale UF Falcon concentrator from dilute conditions up to 30 vol%. A good agreement between measurements and model predictions is obtained, which confirms that our hypotheses about the physics of separation inside a UF Falcon separator remain valid even at high concentrations.INTRODUCTIONThe Falcon concentrator is a fast spinning bowl that is fed at its centre of rotation. It uses centrifugal force to separate particles that are transported inside a thin liquid film that flows upward along the inclined wall of the bowl (McAlister and Armstrong, 1998). Due to differential settling, dense and coarse particles are concentrated inside the bowl whereas light and fine particles are rejected with the overflow stream. The fast rotation speed of the bowl yields high centrifugal force several hundred times the attraction of Earth. Despite the thinness of the liquid film (between 100 µm and 1 mm with a Falcon L40) where separation takes place, the Falcon concentrator can treat high flowrates (up to 30 L/min). At the bottom of the bowl, an impeller transmits the bowl rotation to the feed, which drains upward by centrifugal force as soon as it hits the base of the spinning bowl (Figure 1)."

Jan 1, 2011

By W. T. Bell, M. P. Lebourg

The perforating of multiple tubingless completions, in which two or more strings of 27/8-in. OD casing are installed in the same borehole, presents two basic problems. First, good completion practices require an eficient perforator that leaves no debris to interfere with subsequent completion operations. Second, and of more complicated nature, a system is needed for controlling the direction of fire so that adjacent strings are not damaged. Development of of a 2-in. OD, steel retrievable, shnped-charge gun has solved the first problem. The second was resolved through development of three different devices to provide directional perforating for the two types of completion methods being employed today. These include a mechanical orienting device and two self-orienting radiation devices. Conceivably, the latter methods could be adapted to the directional perforating (of .upper zones) of conventional dual and triple completions without removing production tubing and packers. INTRODUCTION The recent trend to multiple tubingless completions,' wherein two or more strings of 27/8-in. OD casing are installed in the same borehole, has presented two basic perforating problems. The first problem to be overcome was the design of a gun that would result in efficient perforations without causing debris to bridge in these small-diameter casings. The second problem was, of course, to devise a system for controlling the direction of fire such that adjacent strings would not be damaged. The problem of gun debris in slim-casing completions has been well defined in the numerous 27/8-in. single tubingless completions which have been effected during recent years with the expendable-type perforators. Failure of expendable-gun debris to settle out properly, even with good gun break-up, has resulted in bridging inside these small-diameter casings. This, in turn, has interfered with completion and re-conditioning operations. The past two years have clearly shown, in fact, that debris problems are not confined to this small range of casing with most designs of expendable-type guns. A high incidence of bridging has even been reported in 4%-in. OD casing. The perforating of multiple tubingless completions has entailed, therefore, the development of a completely debris-free gun of adequate performance, as well as the necessary devices to provide positive directional perforating in the two completion methods presently being employed. THE GUN —DESIGN CONSIDERATIONS The design of a shaped-charge gun for slim-casing perforating has presented a maze of interrelated prob-lems. Since the primary specification has been leveled at efficient charge performance with complete elimination of gun debris, it has been necessary to develop a retrievable steel-carrier gun of tubular construction to house the charges. The carrier must be retrievable through 2.29-in. API pump-seating nipples which are usually installed in 2 7/8-in. strings. To provide for recovery of the gun from the well, swelling of the carrier on firing must be carefully controlled. Control of swelling automatically means control of explosive weight in the shaped charge which, in turn, influences charge performance. Carrier swelling also depends upon the confinement pressure at the level being perforated, which imposes a hydrostatic pressure-depth limitation. Burr interference on the wall of the carrier, resulting from passage of the jet through the carrier wall, must be eliminated by suitable design. Clearly then, a satisfactory shaped-charge gun design for slim-casing operations represents a fine balance between carrier swelling, hydrostatic pressure, explosive weight and charge performance. Additionally, to lend itself to directional perforating, the gun design must provide a positive locking mechanism for individual charges within the gun carrier. This fixes charge orientation within the carrier and prevents

Development of a permanent human base on the Moon for exploration requires a self sustaining system. This entails production and processing of limited amounts of raw material on the Moon. Any mining and construction activities on the Moon can only be performed by a robust excavation machine that can excavate a variety of material from loose surface regolith to consolidated (frozen) regolith with embedded rocks in the mixture. Meanwhile, limited amount of information on lunar regolith is available to develop and optimize a machine for given lunar ground conditions. Therefore, any excavator designed for use on the lunar surface should have the ability to adapt to a wide range of operating conditions. A prototype cutterhead for the lunar excavator was built and tested at the Kennametal facility in Latrobe PA A. This paper discusses the results of initial material characterization as well as full scale tests of a prototype cutterhead inrelevent material. A brief review of anticipated production rates under various assumed ground conditions will also be presented.

Jan 1, 2009

By Mishark Nnabuchi

A heterojunction of PbS - CuS thin film has been grown on glass slides by SGT. The films were annealed for 1hr at temperature of 373K and 423K respectively. The optical properties were characterized using a UNICO UV - 2102 PC Spectrophotometer at normal incidence of light in the wavelength range of 200 - 1000nm. The minimum percentage transmittance was observed to be 34% for sample A and 25% for sample B within the same optical region. The band gap energy was determined from the spectra to be 2.05eV for sample A and 1.85eV for sample B which gave a band shift of 0.20eV. It can thus be concluded that the optical properties of the films within the VIS - UV - NIR can find application in solar thermal technology, particularly as antireflection coating, window materials and as good materials for selective solar cell fabrication.

Jan 1, 2010

By William Gleason

The mining industry is at a crossroads. Currently, there is an estimated $25 billion worth of projects around the world that have been stopped as the consequence of a dispute or disagreement with their communities, the government or some other stakeholder. Anglo American chief executive officer Mark Cutifani is one who sees the mining industry in need of change and on Dec. 12, he gave the keynote address for the launch the Kellogg Innovation Network?s Mining Company of the Future Initiative?s Development Partner Framework (DPF). The launch was held at the Ford Foundation building in New York City. The DPF seeks to inspire and support the mining industry to adopt a new way of thinking and a new approach to how it secures, nurtures and revitalizes its social license to operate. Working with a diverse group of people from faith-based organizations, nongovernmental organizations (NGO) and other stakeholders, Cutifani often had the rather uncomfortable position of representing the mining industry in a room full of people who are far from the industry?s biggest fans.

By Evangelos Petrakis, Kostas Komnitsas

This study investigates the evolution of dimensional properties of grinding products, namely, the mass, the surface area, the length, and the number of particle distributions with the energy input in a ball mill. The size analysis of the mill products enables the calculation of the mass distribution of each material at predetermined size classes and then the determination of the other dimensional properties by taking into consideration the geometry of the particles. Based on the distribution of dimensional properties, an effort was made to determine whether the grinding products are fractal in nature. The effect of material type and grinding conditions on the relationship between the dimensional properties and the specific energy input was also investigated. Special importance was assigned to the study of the specific surface area and the surface area production rate, both during the initial grinding stages and at higher energy levels. The determination of the surface area production rate allows the identification of the grinding limit and the maximum specific surface area which could theoretically be achieved. This approach has as ultimate objective the maximization of energy efficiency and subsequently the minimization of the high grinding cost.

By Evangelos Petrakis, Kostas Komnitsas

This study investigates the evolution of dimensional properties of grinding products, namely, the mass, the surface area, the length, and the number of particle distributions with the energy input in a ball mill. The size analysis of the mill products enables the calculation of the mass distribution of each material at predetermined size classes and then the determination of the other dimensional properties by taking into consideration the geometry of the particles. Based on the distribution of dimensional properties, an effort was made to determine whether the grinding products are fractal in nature. The effect of material type and grinding conditions on the relationship between the dimensional properties and the specific energy input was also investigated. Special importance was assigned to the study of the specific surface area and the surface area production rate, both during the initial grinding stages and at higher energy levels. The determination of the surface area production rate allows the identification of the grinding limit and the maximum specific surface area which could theoretically be achieved. This approach has as ultimate objective the maximization of energy efficiency and subsequently the minimization of the high grinding cost.

By J. A. Burkhardt

Field measurements and theoretical studies have been made of pressure surges—momentary variations in fluid pressure—produced by movement of pipe in mud-filled boreholes. Pressure measurements were recorded by five pressure gauges located at various positions in the borehole. An important positive pressure peak was found to occur as the casing moved with maximum velocity. Important negative peaks were found as the casing was lifted from the slips and as brakes were applied to stop pipe movement. A rigorously formulated theory has successfully predicted the sequence and magnitudes of these positive and negative surges and has established a basis for understanding how they occur. Both the measurements and theory indicate that the most important pressure surge is usually due to viscous drag of the flowing mud. The theory of viscous-drag pressure surges has been approximated by simplified graphs and calculation procedures to facilitate ready use in field operations. Comparison of measured results with those predicted by the simplified theory shows that the magnitude of this surge can be predicted accurately. INTRODUCTION It is widely recognized that raising or lowering pipe in a fluid-filled borehole produces momentary variations in fluid pressure, commonly called pressure surges. Both negative (or "swabbing") surges and positive (or "fracturing") surges may occur. In 1934, Cannon1 measured the negative surges and showed that they could be large enough to cause flow of formation fluids into the well-bore and, in extreme cases, lead to blowout conditions. Later, Coins2 measured the positive surges associated with lowering pipe. His results and subsequent field operations strikingly demonstrated that pressure surges could be an important factor in some cases of lost returns. In addition, although the evidence is less clear than in the case of blowouts and lost returns, other investigators 3, 4 feel that pressure surges probably play a part in many instances of minor gas cutting, salt-water flow and other hole trouble. The importance of pressure surges in drilling operations led naturally to attempts to explain the physical causes, nature and magnitude of the surges. Cardwell5 was the first to publish a theory which allowed the quantitative prediction of momentary pressure variations. He assumed that the drilling fluid was a 300-cp Newtonian fluid in turbulent flow. Most field muds have a considerably lower viscosity and are generally believed to be Bingham plastic in nature.6 However, card-well's results were useful because they were presented in a form convenient for field use and, in some cases, gave a reasonably accurate predicted value for the maximum pressure surge. Subsequently, Ormsby7 published a more comprehensive theory of pressure surges. He discussed both laminar and turbulent flow and considered the theory of mud-bypass devices for reducing pressure surges. As a consequence of his more rigorous approach, his results were more accurate but more complex and difficult to use. Further, both Ormsby and Cardwell considered only the pressure surge arising from viscous drag of the moving mud. Clark later published idealized graphs of surges and presented equations for predicting their magnitudes. In addition to pressure variations arising from viscous drag, he considered those caused by inertial effects. His theory was in this respect more complete than those of Cardwell and Ormsby, although he did not discuss pressures due to breaking of the gel. Furthermore, his equations, while not exceptionally complicated, were too complex for ready use at a drilling location. One difficulty common to all three theories is that none was tested rigorously by direct comparison with measured pressure surges. Their accuracy, therefore, could, not be demonstrated. Further, the two theories based on most realistic assumptions (Ormsby and Clark) required the solution of one or more rather complex algebraic equations. The research described in this paper was undertaken to supplement that described and to overcome some of the difficulties noted. It seemed obvious that a fully satisfactory study of pressure surges should encompass three main phases. 1. A valid theory useful in all field situations must be developed. This theory must be based upon realistic assumptions, must be formulated rigorously and should lead to clear concepts whereby the nature of pressure surges can be easily understood. 2. The theory, however complex and involved, ultimately must be presented in simplified form for convenient field use. This may involve extensive machine computations and the use of figures and empirical equations. 3. The accuracy of the simplified equations must be established by comparing measured pressure surges with those predicted by the theory. These must agree both in their characteristic nature and in magnitude. 'This means that careful measurements of surges occurring in actual field operations must be made.

By L. Andrews

Nickel is recovered as a by-product of the platinum-producing process operated by Anglo Platinum. The metal is mined mainly as sulphide minerals contained in platinum ores. These pass through the concentrating, smelting and converting process route and nickel is finally recovered by electrowinning. Smelting of the concentrated ore in the electric furnace produces a melt with a high slag to matte ratio. The resulting furnace slag is granulated and later milled and floated to recover matte. A project was initiated to investigate the distribution of nickel in the slag in order to improve recovery. Slag samples were examined using a combination of chemical and mineralogical techniques. The granulated slag was found to consist mainly of a silicate glass phase, which reflects the composition of the molten slag in the furnace. Nickel occurs as free matte granules, as matte phases locked inside the glass, and in the glass phase itself. Whereas nickel in the matte is as sulphide, most of the nickel in the glass phase appears to be oxide- bound(i.e. in solid solution). Milled slag as flotation feed showed recovery-limiting features such as free matte with oxidized surfaces and unliberated matte inclusions in the slag. The biggest nickel losses, assuming no tapping problems, are in the glass phase solid solution. Only around 40% of nickel would be recovered from the slag, even under ideal conditions. Spoon and pot slag samples were also examined to see if casting and crushing would improve recovery. Although larger and therefore more easily recovered matte phases formed, nickel partitioned into crystalline silicate phases, limiting the maximum theoretical nickel recovery to 70%.

Jan 1, 2004

By J. C. Bothan

A program to provide technical in-formation on the use of fuels in pyro-metallurgical processes, from the Canadian fuel viewpoint, was initiated about five years ago by a Canadian Institute of Mining and Metallurgy liaison grou1> composed of members from the Coal Research Committee of the Coal Division and the Iron and Steel Committee of the Metallurgy Division. This paper is another of a series prepared for this program. Previous papers included a review of pyrometallurgical processes of Canadian interest, a survey of ferrous processes relevant to the development of an integrated steel industry in western Canada and a survey of the fuel requirements of the non-ferrous metals industry in Canada. It is widely recognized among per-sons familiar with the Canadian coal industry that, because of the large resources of coking coal in western Canada, the

Jan 1, 1963

By M. K. Mohanty, H. Akbari, L. A. Ackah

Dry separation was the predominant method of coal cleaning in the United States from the 1930s to 1980s. The application peak of dry separators for cleaning raw coal was in 1965, when about 23.1 Mt of cleaned bituminous coal was produced. The main advantage of dry coal cleaning is the elimination RIWKH GHZDWHULQJ VWDJHV DQG VLJQL¿FDQWO\ UHGXFHG moisture in comparison to wet processing. In addition, developed dust control systems have made dry cleaning method an environmentally friendly process. The largest air-based coal cleaning plant was built in Pennsylvania in 1968 and could clean 1,272 t/h of raw coal sized smaller than 19 mm. This was followed by a decline in dry coal cleaning to less than 3.6 Mt in 1988. Some of the main reasons that shifted coal operations IURPGU\WRZHWSURFHVVLQJZHUHWKHQHHGIRUPRUHHI¿FLHQW separations with lower density cuts, increase in raw coal surIDFHPRLVWXUHVSHFL¿FDOO\LQXQGHUJURXQGPLQLQJWRFRQWURO GXVW ¿QHUSDUWLFOHVL]HUHTXLUHPHQWV LQFUHDVHLQ¿QHVLQUDZ coal from underground mines, and health and safety concerns related to dust and noise (Arnold, Hervol and Leonard III, 1991; Miller, 2011).

By Larry DeGraff

With the increase of new mine development in the past several years, many coal mines have decided to self- perform the design and construction for their slope development projects. The development process of determining the proper configuration is challenging, and a major economical consideration. Greenbrier Smokeless Minerals engineering staff and consultants, along with DSI/American Commercial, developed a support configuration that was best suited for their slope. The developmental process took into consideration the length of slope, depth of slope at the high-wall transition, economics of a single or multiple entries, waterproofing, stresses on the steel supports and lagging during the backfilling operation. This paper describes the developmental concept of using a single entry, side by side configuration, using steel ?Banjo String? supports with steel plank lagging, to develop a long term permanent installation in a cut and cover application.

Jan 1, 2009

By Özgür Bezgin

This paper presents observations on the installation of drilled shafts from two construction projects and an academic study with experimental and analytical parts. The construction projects involved the use of pressurized drilling methods. The experimental part of the academic study involved the use of the auger drilling method. The analytical part of the academic study investigated the effect of drilling methods on the soil-structure interaction and the behavior of drilled shafts under lateral loads. The concept of ?free-length? is introduced for the lateral load design of pressure-drilled shafts that are thought to be fully embedded within a soil media. The academic part of the study presented herein was conducted in Rutgers, the State University of New Jersey.

Jan 1, 2009

By J. Hollow, D. Walsh

The Fort Knox Mine is located in Alaska’s interior, where the average ambient air temperatures range from -24oC in January to 16oC in July. The mill processes a free milling gold ore utilizing both a gravity recovery circuit and a conventional cyanide leach/carbon-in-pulp circuits. Mathematical models have been developed to accurately predict the impact of leach circuit slurry temperature on gold leach, carbon adsorption and cyanide destruction kinetics. Additionally, an energy balance approach has been used to model the seasonal variations in slurry temperatures throughout the Fort Knox mill. The energy balance model, combined with the kinetics models previously developed to predict plant performance, was used to justify a tailing thickener installation at the Fort Knox Mine. This paper describes the development of the energy balance model and its prediction of plant performance assuming a tailings wash thickener to reduce heat loss from the mill. Also presented is an analysis of the post project plant performance that validates the model and shows the mine produced an additional 596 kg (19,155 ounces) of gold, while reducing mill reagent costs by $6,302,000 during the first 38 months of operation.

Jan 1, 2007

By Michael J. Jorgensen, Pranathi B. Aedla, N. K. Kittusamy

Risk factors associated with the development of muscu­loskeletal discomfort and disorders during the operation of heavy mobile equipment include whole-body vibration and awkward and sustained joint postures of the shoulders, neck, and trunk. Cab design may influence awkward postures of the joints, and task duration may influence duration of exposure to awkward and static postures and whole-body vibration. To reduce exposure to risk factors related to the interface between cab design and task, it may be necessary for manufacturers to address cab design. This study assessed the repeatability of a cab design checklist developed to evaluate various design characteristics that can influence exposure to risk factors for musculoskeletal discomfort. The ability of the cab design checklist to identify posture-related deficiencies of design was also assessed. The checklist was used by two administrators across 10 pieces of heavy construction equipment. Video analysis was performed to quantify postures of the neck, shoulder, and trunk; correlation analysis was used to determine whether specific questions from the checklist were associated with the identification of awkward postures. The repeatability assessment resulted in kappa coefficients ranging from 0.52 to 1.0 (good-to-excellent reproducibility) across each piece of equipment, and an overall kappa coefficient of 0.77 (excellent reproducibility) when considering all equipment together. Results from the correlation analysis showed that shoulder flexion posture was correlated with scores from the cab design checklist. However, results of the cab design checklist were not significantly correlated with shoulder abduction or awkward postures of the neck and trunk. Results suggest that the cab design checklist may be useful for identifying cab design characteristics that need further improvement and for identifying design characteristics that increase shoulder flexion. The strength of the repeatability assessment suggests that outcomes of the cab design checklist administered by different individuals may be consistent, independent of the type of equipment being assessed.

By Eric Low

Raising capital by issuing debt or equity is necessary in almost every corporation. In the field of corporate finance, the raising of capital is a heavily-studied topic. However, some of what is studied on this topic in corporate finance is not applicable in the mining industry. There are also many financing options that were created for the mining industry such as flow-through shares, prepaid forwards, and royalty sales. The cyclical nature of the industry makes the risk-return profile of financings more difficult to estimate than in other industries. Additionally, the methods used to assess firm value are different than other industries, as the values of orebodies are not included on balance sheets. For precious metals companies, which are a hedge against most other securities, there are additional complications with determining investor expectations and cost of equity. This thesis puts forth a decision-making framework to explain mine financing choices from the perspective of mining companies. The approach is threefold. First, all of the major equity and debt financing instruments available to mining companies are presented and analyzed. Each financing method is assessed on a wide range of criteria. Next, these concepts are applied in case studies of four companies: BHP Billiton, Barrick Gold, Teck Resources, and Noront Resources. For each company, the overall choice of financing methods is shown and analyzed. The effect of financing choices on the weighted average cost of capital (WACC) is calculated. The final section deals with case studies of individual mine finance decisions during the past two years.

May 1, 2011

By P. N. Lategan

Mining companies are challenged with increased difficulty in delivering capital projects on schedule and within budget. In 2005, PricewaterhouseCoopers global review of major capital projects in the mining industry only 2.5% of projects could be defined as successful when assessed across the four critical dimensions of scope, cost, schedule and business benefits. Thus 97.5% of major mining capital projects were not successful according to the criteria PricewaterhouseCoopers used. Normally if a project fails on all these criteria it indicates scope creep. Scope creep refers to the change in a project's scope after the project work has started. As a result, the projects drift away from their original design, timeline, and budget, and as a consequence destroy business benefits. The major reasons for scope creep are poor change control and the lack of proper front end loading. Change control and front end loading are based on project processes in the planning and monitoring & control process group of the Project Management Body of Knowledge1 (PMBOK). This paper will focus on key factors to consider during project scheduling/planning with special reference to cost and schedule (using Microsoft Project as a tool although the principal is universal)

Jan 1, 2009

By Fernando Cillóniz

Benchmarking es un proceso de comparación y medición de los procesos de negocio de una organización, con aquellos que lideran el mercado. De forma que se obtiene información para mejorar el desempeño de las empresas. En ese sentido, el presente texto señala la utlidad del Benchmarking en las empresas donde el uso de la Internet y las tecnologías de la información permiten hacer más eficiente las comparaciones e intercambio de experiencias y conocimientos, así como internacionalizar el proceso.

Aug 25, 2002

By Abdul Aziz Hanifah

A novel instrumentation and analysis technique, called GLOSTREXT method has recently been introduced for bored pile load tests in Malaysia. This technique provides an innovative and improved alternative for conventional bored pile instrumentation methods commonly practiced for the past few decades. Results for five case histories involving full scale static load tests for high capacity bored piles with both new and conventional instrumentation details placed in within the same instrumented piles are presented to demonstrate the advantages of this novel technique. Results show good agreement between the new and conventional instrumentation.

Jan 1, 2006