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By Mohammad. M. Khajeh

Rock mechanical properties are important parameters in geomechanical simulation. Considering stochastic heterogeneous models rather than conventional homogeneous layer cake models leads to more realistic simulation results and uncertainty assessment. These heterogeneous models are usually fine scale models generated by geostatistical techniques. Although considering high resolution property models is desirable, geomechanical simulation with a fine scale model is not computationally feasible for full?field, coupled geomechanical-flow simulation. Upscaling of property models is necessary to move from fine scale/high resolution property models to coarser scale/low resolution models appropriate for simulation. Local numerical upscaling was proposed by Khajeh et al. (2012) to describe the macroscopic elastic behavior of complex heterogeneous media and is expanded upon in this work. This numerical technique is not restricted to specific geologies as typical analytical techniques are. Moreover, transversely isotropic deformation is considered rather than the usual assumption of isotropic deformation. To compare the accuracy of the upscaling methodology, in this study shear strain is considered as the geomechanical response of a synthetic facies model and the response of the coarse scale model is compared to other conventional analytical averaging techniques. It is found that the numerical upscaling technique better approximates the geomechanical response of the fine scale model.

Jun 1, 2012

By M. Gimpel, R. Galler, T. Antretter, H. Kargl, R. Tichy, W. Ecker, M. J. Mikl-Resch, G. Pittino

"A computational method based on a continuum-mechanical approach to simulate rock cutting is developed and evaluated. The aim is to obtain the local loading acting at the cutting pick during operation. The explicit FEM is chosen to model the pick-rock interaction. The presented method takes advantage of (i) an advanced material model (ii) a robust contact algorithm and (iii) fast calculations due to parallelization. A damage-plasticity law is chosen and modified with user-subroutines. A user integrated element deletion routine evades critical mesh distortions. Infinite elements at the model boundaries avoid unrealistic deformation wave reflection.INTRODUCTIONExcavation in mining and tunneling is a costly and complex process. Special equipment such as the roadheader (Figure 1) is employed to cut the rock in the excavation process but high material strengths limit their usability (Tockner 1999). Nowadays a challenge is to extend their field of application to harder and more abrasive rock materials. The forces on the pick (Figure 2) are of great importance and determine wear and especially the efficiency of the machine. Figure 2 shows the principle of cutting and the predominant forces. The variation of pick geometry, cutting depth or attack angle will result in an alteration of these forces and determine the efficiency of the process (Tockner 1999). The mechanisms of rock cutting follow the principle of indentation (Kou et al. 1999). Directly under the indenter a hydrostatic stress state evolves causing the material to fail only due to crushing and fragmentation mechanisms. In the close surroundings large strains emerge and tensile cracks are formed but in a further distance the material behaves elastically."

Jan 1, 2015

By M. Gimpel, R. Galler, T. Antretter, H. Kargl, M. Mikl-Resch, R. Tichy, W. Ecker, G. Pittino

"A computational method based on a continuum-mechanical approach to simulate rock cutting is developed and evaluated. The aim is to obtain the local loading acting at the cutting pick during operation. The explicit FEM is chosen to model the pick-rock interaction. The presented method takes advantage of (i) an advanced material model (ii) a robust contact algorithm and (iii) fast calculations due to parallelization. A damage-plasticity law is chosen and modified with user-subroutines. A user integrated element deletion routine evades critical mesh distortions. Infinite elements at the model boundaries avoid unrealistic deformation wave reflection.INTRODUCTIONExcavation in mining and tunneling is a costly and complex process. Special equipment such as the roadheader (fig. 1) is employed to cut the rock in the excavation process but high material strengths limit their usability (Tockner 1999). Nowadays a challenge is to extend their field of application to harder and more abrasive rock materials. The forces on the pick (fig. 2) are of great importance and determine wear and especially the efficiency of the machine. Figure 2 shows the principle of cutting and the predominant forces. The variation of pick geometry, cutting depth or attack angle will result in an alteration of these forces and determine the efficiency of the process (Tockner 1999). The mechanisms of rock cutting follow the principle of indentation (Kou et al. 1999). Directly under the indenter a hydrostatic stress state evolves causing the material to fail only due to crushing and fragmentation mechanisms. In the close surroundings large strains emerge and tensile cracks are formed but in a further distance the material behaves elastically."

Jan 1, 2015

By E. C. Grunsky, B. W. Smee

"The development of low-cost, rapid multielement analytical techniques has generated large geochemical databases in many exploration programs. When a sampling program consists of several thousand samples, the resulting data matrix is enormous and effective interpretation using all of the elements individually becomes burdensome. However, the application of multivariate statistical techniques can extract geochemical patterns related to the underlying geology, weathering, alteration and mineralization. Imaging the results over topography enhances the interpretation of these patterns. Examples of this approach are shown from mineral exploration programs in Canada and Mexico. IntroductionThere has been a dramatic change in the effectiveness of using geochemical survey data in the past ten years. This is mostly due to:• lower cost of geochemical analysis;• lower detection limits;• new methods of multi-element analysis;• a marked decrease in the turnaround time;and• the intelligent use of computers in presenting geochemical data.Geochemical surveys commonly have two objectives: locating abnormal concentrations of ore-forming or pathfinder elements and characterizing the underlying host lithologies. Geochemical surveys often employ a wide range of sample media that may typically include whole rock lithogeochemistry, various soil horizons, till and basal till sampling, stream sediments, lake sediments, and various forms of weathered regolith. Each of these sample media will exhibit a unique element distribution that must be factored in the interpretation phase of a geochemical survey study. This can become a cumbersome process if univariate data handling methods are employed."

Jan 1, 2003

By Georges Houlachi, Akram Alfantazi, Maysam Mohammadi

Manganese ions in zinc electrowinning electrolytes form a protective MnO2 layer that ultimately decreases Pb contamination in the zinc product. In this study, the effect of dissolved Mn2+ on the electrochemical performance of Pb, Pb-Ca and composite Pb-MnO2 anodes was investigated. The properties of the MnO2 layer formed on these anodes were studied and compared. Potentiodynamic polarization and cyclic voltammetry experiments were performed in 180 g L-1 sulphuric acid to study the electrochemical reactions occurring on the anodes. The anodes were subjected to galvanostatic polarization at 50 mA cm-2. The morphology and uniformity of the MnO2 layer on the anodes were examined using scanning electron microscopy (SEM). Experimental results revealed that the MnO2 layer formed on the composite anode was more compact and uniform compared to that formed on the Pb and Pb-Ca anode. It was also observed that the cell mud formation rate, and consequently manganese ions consumption, depended on the anode type. Although initial formation of the MnO2 layer decreased the oxygen evolution overpotential, its growth might negatively affect electrocatalytic activity of the anodes.

Jan 1, 2014

By J. Lammers, D. Adams

Most pressure oxidation operations introduce oxygen through a large multi-use nozzle in the vapour space of the autoclave. Sparge pipes extend inside the vessel to the point of discharge below the compartment agitator. However, two zinc pressure leach operations have successfully used a bottom entry oxygen sparge system for a number of years. Recently, the concept has been used in a whole ore gold pressure oxidation operation as well as a copper pressure leach plant. Both of the latter operations also introduce cooling water for temperature control through the same sparge pipe. This paper addresses the benefits of the bottom entry system with regards to autoclave performance and the positive effects on agitator performance.

Jan 1, 2004

By Joanne G. Petrini

ISO 26000 Unique Process Unique Personality ?Almost 10 years in the making ?What type of standard is this? Different type of ISO Standard ISO 26000 Structure and Substance ?Principles ?Core Subjects ?Implementation Guidance ISO 26000 Impact ?Same old, same old? ?So Is there really anything NEW? ?Should I care??

May 1, 2011

By Chris Cross

A working group from Anglo American, BHP Billiton, Rio Tinto and Xstrata reviewed supply and demand for graduates from mining education departments in countries where they normally recruit: Australia, Canada, Chile, Western Europe, South Africa and USA. Departments are typically small and increasingly unsustainable, resulting in a steady rate of closure. Supply and demand for graduates in the minerals industry is cyclical, with supply lagging behind demand and trending downwards. Currently, supply is tight and the industry is trying to expand with an ageing workforce. Greater collaboration between universities and within the industry is recommended to address these issues.

May 1, 2006

"The Detour Lake Mine is located in northeastern, Ontario, approximately 300 kilometres northest of Timmins and 185 kilometres by road northeast of Cochrane. The mill processes a free milling gold ore using both gravity circuit and leaching with a state-of-the-art carbon-in-pulp circuit. The grinding circuit is a conventional SABC circuit with a tonnage of 55,000 mtpd at 95 microns with the addition of pre-crushing upstream of the SAG mill.The present paper will describe the methodology used to successfully prove that gold of the Detour Lake Mine ore is mostly concentrated into the fine size fraction of the blasted rocks. It will describe the various options possible to create value from this ore property.IntroductionThe purpose of this test work was to determine the grade of the pebbles and consider if there was value into discarding the pebbles and replacing the material by fresh feed.1. Pebble samplingThe pebbles were sampled and assayed for grade every day for 3 months. After 3 months of sampling, the results showed that the pebbles only carried 28% of the fresh feed grade. This phenomenon can possibly be explained by the fact the gold is located into area of fracture in the rocks.January-March 2014 – Pebble assay average• Line #1 = 0.222 g. Au/t• Line#2 = 0.275 g. Au/t• Head grade = 0.88 g. Au/t2. Crushing and grinding circuit surveysWith the above information, a grinding circuit survey was planned. The purpose of the survey was to build a JKSIMMET model of the grinding circuit for mill optimization but also to understand the deportment of gold into various size fractions that may explain why there is so little gold in the pebbles. All streams and size fractions was analysed for particle size analysis and for gold.Since Detour has dual grinding lines, both circuits were sample at the end of May. Two supplemental survey of the secondary crushers were also done and a survey of the gyratory crusher."

Jan 1, 2016

By K. C. Corin, M. S. Manono, J. G. Wiese

Depressants play a crucial role in the flotation of PGM bearing ores as they prevent naturally floatable gangue (NFG) from reporting to the concentrate. This action is regarded as critically important because less dilution of the concentrate means lower costs for downstream processes. However, abnormal water conditions (such as high concentrations of ions) in the flotation system can modify the selectivity of these depressants. It is well known that the existence of selected electrolytes in water can alter the behaviour of some polysaccharide depressants by enhancing their adsorption onto gangue minerals and thereby prevent naturally floatable gangue from moving into the froth phase. Concurrently these same electrolytes may enhance frothability, owing to their stabilising effect on the bubbles within the system. Plant water at various ionic strengths was investigated against depressant type and dosage in order to understand electrolyte-depressant interactive effects during the flotation of a Merensky ore, using entrainment, rate of NFG recovery, and total gangue recovery as proxies. The study showed that the rate of NFG recovery per unit mass of water decreased with increasing ionic strength at all dosages, however the total amount of gangue reporting to the concentrate increased with increasing ionic strength at all depressant dosages. Thus, this paper attempts to consider the effects of both ionic strength and depressant dosage as individual factors within flotation. It further looks to investigate whether any interactive effects exists between these two factors when considered simultaneously.

Jan 1, 2016

By X. Yuan

"The processing behaviours of ores such as their liberation characteristics in comminution and their response in separation processes are affected by their mineralogical characteristics. Key ore characteristics which are relevant to processing, such as mineral proportions, mineral grain size, grain shape and mineral associations are routinely measured at the micro-scale in polished section using optical microscopes and SEM-based automated mineralogy systems. The application of X-ray micro-tomography to mineral processing provides the means to quantify these important micro-textural characteristics in three dimensions, removing the stereological issues encountered when measuring volumetric information in two-dimensional polished sections. In this paper we present several examples of ore textures to illustrate where X-ray micro-tomography can be applied successfully to obtain quantitative measures of ore characteristics which are useful in a variety of process modelling applications.INTRODUCTION X-ray tomography has been used as a tool in medicine for some years and is being applied in a wider range of fields including geology, palaeontology and mineralogy. In this paper we present some applications of X-ray tomography in mineral processing applications being developed at JKMRC. The availability of SEM-based automated mineralogy systems such as MLA and QEMSCAN has seen the increased use of quantitative mineralogical data measured in two dimensions in the design, operation and simulation of mineral processing plants. When the ore is amenable to measurement by X-ray tomography this technique can provide quantitative data for characteristics such as mineral grain size, shape, mineral associations and liberation in three-dimensions. The advantage of measuring these characteristics in three-dimensions is that the stereological issues which bias measurements made on polished sections are removed. X-ray tomography also quantifies the location of mineral grains relative to one another in space - a useful descriptor of ore texture. Like many measurement techniques X-ray tomography has advantages and disadvantages when compared to other techniques. One limitation is that the ability of the X-ray tomography system to discriminate between minerals is a function of the X-ray attenuation of those minerals. While the X-ray attenuation of many common minerals is sufficiently different for X-ray tomography to distinguish between them, there are some where the overlap in X-ray attenuation makes discrimination on the basis of this characteristic alone impossible. An example of this would be chalcopyrite and magnetite. However where the ore mineralogy is suitable to apply X-ray tomography, the technique provides some exciting opportunities to explore the relationship between texture and ore processability."

Jan 1, 2012

By Robert B. Parsons

"It is easy to throw darts at government - and government often deserves to be a target. This month, Tax Notes examines tax legislation from a different angle, and sees some bright spots.The following article is based on a paper presented by the author at the International Gold Symposium in Rio de Janeiro in August 1989Introduction""No man's life, liberty, or property are safe while the Legislature is in session.”With one federal government, ten provincial governments, and two territorial governments all claiming to have constitutional rights to tax and otherwise regulate Canada's mining industry, and with each of these thirteen governments pursuing their respective rights with some vigor, government involvement in one way or another is an accepted way of life in the industry. While one's initial reaction to government involvement in an industry might be one of scepticism or fear, generally speaking the federal, provincial, and territorial governments in Canada tend to be pro-mining. They recognize the importance of the mining industry to Canada, especially in terms of job creation and exports. It is not surprising, then, to find that an array of valuable fiscal incentives are available to the industry through federal and provincial legislation.This paper summarizes the principal incentives that are inherent in Canada's tax legislation, as well as the Canadian Exploration Incentive Program. Although it is beyond the scope of this paper to deal with all of the incentives that are available, it is noted that various forms of federal or provincial assistance are also available outside of specific legislation, through negotiation with government departments. This latter type of assistance is generally directed toward helping with the cost of infrastructure such as roads or hydro lines, or Jess often toward loan guarantees or similar financing assistance."

Jan 1, 1990

By W. J. Wolfe

"Quartz Hill is a large, low- to moderate-grade quartz vein stockwork porphyry molybdenum deposit, discovered in 1974 during a regional stream sediment geochemical reconnaissance survey of southeast Alaska conducted by United States Borax and Chemical Corporation. Mineralization is localized in the upper parts of an Upper Oligocene (30 Ma) composite quartz monzonite stock which is emplaced discordantly into older Cretaceous to Early Tertiary terrain of the Coast Range igneous metamorphic complex of the northwest North American Cordillera. Subsequent fault-controlled, complex multi-stage intrusion, concentrated in the core of the Quartz Hill stock, produced successive pulses of hydrothermal alteration and molybdenum mineralization at about 27 Ma. Overall, the deposit is tabular and flat-lying and well suited to open pit mining. The 0.05% MoS2 grade limit covers an area of approximately 1500 m by 2750 m and extends to a maximum depth of 520 m below surface. Details of grade distribution show two separate lobes of higher grade material within the larger low-grade deposit.A ten year program of exploration drilling, underground development, sampling and metallurgical testwork led to a 1983 feasibility study based on a resource of 1600 million tonnes grading 0.127% MoS2 at a 0.08% MoS2 cutoff The large size of the deposit and its homogeneous grade distribution, typically showing gradual outward decrease of grade, makes in pit grade selection practical at several cutoff levels. Cominco Ltd. now reports a Probable Resource of 210 million tonnes averaging 0.22% MoS2 with a further Possible Resource of 1100 million tonnes averaging 0.12% MoS:z. At low molybdenum metal prices which have persisted for 10 years since the molybdenum price spike of the late 1970s and early 1980s, the Quartz Hill deposit is sub-economic."

Jan 1, 1995

By P. Pal Roy, R. B. Singh

"This paper focuses on a number of interesting results to establish the theory and principle of air-deck blasting. It also gives the mechanism of breakage that takes place in air-deck blasting under varying charge load conditions. With these aspects in mind, the mine management can implement this up-coming technology to enhance safety and higher productivity. IntroductionThe method of air-decking has become an increasingly popular technique in production and presplit blasting. In the blasthole, an explosive column is combined with an airchamber. The main aim of the technique is to control breakage through effective distribution of explosive energy and thereby enhance uniform rock fragmentation. An air column lowers the initial pressure of the explosive products and simultaneously increases the time of interaction for the detonation front with the surrounding rock, which enhances rock breakage.To study air-deck blasting, CMRI initially conducted experiments using indigenously developed, low-cost wooden spacers of different sizes and strengths. Air-deck blasting was first tried using these spacers in 1993 at Jambad OCP, ECL and Chasnalla OCP, IISCO. The experiments were extended in 1994 at Bermo Mine, DVC. The results were subsequently published by Pal Roy et al., in 1995. It is worth mentioning that the performance of air-deck blasting during this period was only compared with conventional blasting practices without going into detail of the theory behind the process."

Jan 1, 2001

By O. Hungr, V. Gischig, G. Preisig

Deep-seated landslides are characterized by slow time-dependent movements induced by constant gravitational creep, and periods of acceleration associated with stress changes within the rock and the preexisting fracture network. Natural stress changes are typically caused by seasonal variations in surface temperatures and groundwater pressures, but also by rare and more violent events such as earthquakes. These processes are responsible for cyclic loading and unloading that leads to rock mass damage, fatigue and progressive failure with time, and may explain sudden, unexpected rock slope acceleration phases. In this work, we present a set of distinct-element models to investigate and compare the role of hydromechanical fatigue and seismic fatigue in the history of a deep-seated landslide. Hydromechanical fatigue arises from the fluctuation of pore pressure in fractures accompanying periods of significant groundwater recharge. In alpine areas, there are usually one or two cycles per year associated with snow melt and intense rainfall periods. In the presence of a deep confined aquifer within the rock slope, the amplitude of pressure fluctuations may reach values of 0.25-0.5 MPa. Hydromechanical models considering such pressure changes are able to reproduce observed slope accelerations-decelerations phases. Substantial accelerations may occur even in the absence of a cycle of exceptional amplitude, depending on the current state of fatigue. At a given time, one or more fractures may be critically-stressed, and a small change in applied stress is enough to cause local failure and induce a crisis of enhanced slope acceleration. This is augmented if the rock slope contains planes of weakness associated with its tectonic history, glacial debuttressing, etc. The corresponding behaviour is analogous to laboratory experiments on rock and metal fatigue. Similar fatigue effects have also been proposed for repeated earthquake events in seismically active regions. Unlike hydromechanical stress changes that occur in a more localized portion of the rock slope, those induced by passing seismic waves involve the entire rock mass. Moreover, the frequency and amplitude of stress perturbations due to earthquakes are different than those induced by pore pressure variations, although both likely contribute in combination to the degradation and progressive failure of large deep-seated landslides when both are present. The results presented illustrate that: (1) assessment of slope stability near critical infrastructure (e.g., hydroelectric reservoirs) should not only consider static stability, but also failure mechanisms related to fatigue that evolve over time and may result in an apparently stable slope progressing towards a critical state due to relatively small but repetitive stress changes; and that (2) characterization of fatigue processes affecting a deep-seated landslide requires multiparametric continuous monitoring at different observation points.

Jan 1, 2015

By K. Ilankoon, I. M. Saman, S. J. Neethling

In heap leaching the transport of the acid from the drippers to the surface of the ore particles is a major factor in the overall performance of a heap. This flow behaviour is complex as the flow is unsaturated and occurs along a tortuous set of inter-particle channels and connections. The particle properties such as size, shape and porosity are very important when modelling the liquid holdup and flow within heaps, since the dominant mechanisms at work are quite different. This paper investigates the effect of these particle properties experimentally on heap flow behaviour using a 1-D column leaching system consisting of non-porous glass beads with a system of actual ore particles. The similarities and differences between the two systems on flow behaviour are described using an inter-particle flow model. In addition, the applicability of positron emission particle tracking (PEPT) for laboratory column leaching will be detailed to calculate hydrodynamic dispersion in packed beds compared to more conventional residence time distribution (RTD) tests and also to obtain the time averaged rivulet flow paths through the particles of the bed for the better understanding of heap hydrodynamics.

Jan 1, 2014

By T. W. Wong, M. A. Whitney, A. Hadadzadeh

Uniaxial compression tests were performed on cylindrical specimens, 10mm in diameter and 15mm in height, machined from an extruded AZ31B magnesium billet. The tests were conducted under isothermal conditions to a true strain of 0.5. The study compares macroscopic flow anisotropy between the extruded (ED) and transverse (TD) directions in the temperature range of 300°C to 500°C, and strain rate range of 0.001s-1 to 1s-1. Compression of ED specimens at low strain rate (0.001s-1) exhibited axisymmetric flow, and no significant differences were observed between geometries of specimens deformed above 350°C under the same strain rate. Deformation of TD specimens at low temperature and/or low strain rate resulted in elliptical cross-sections, with the anisotropy of flow being less significant at higher temperatures. Other studies performed using rolled plates have proposed that pyramidal slip and cross-slip at higher temperature eliminate the effects of initial texture, while the dominance of prismatic slip at lower temperatures will result in anisotropic flow. It is believed that the initial fiber texture common among extruded HCP-structured materials plays a role in the anisotropic deformation behaviour observed in the extruded specimens

Jan 1, 2015

By P. Radziszewski

"The comminution energy curve is a profoundly simple graphical technique that displays detailed operating efficiency information for industrial comminution processes. The database underlying the methodology has recently more than doubled, to now contain a substantial fraction of the international comminution output (1.7 billion tonnes of rock per year) across more than 8 major commodities. This increase has deepened the analytical capabilities and effectiveness for assessing comminution circuit performance in relation to comparable operating mines. This paper will explore how the energy curve methodology can be used to examine the ability of stirred mill technologies to increase efficiency.Specifically, this paper explores how the energy curves methodology can be used to present energy efficiency gains achieved at three mines employing a stirred mill technology under different duties. The first of these cases studies was conducted by Rosa (2014) who compared the performance of two ball mills operating in parallel with a Vertimill in the regrinding circuit at the Samarco Iron project in South East Brazil. The Vertimill was found to achieve the same product specification while consuming 40% less energy. Brissette (2010) investigated the impact of grinding media on the performance of both ball mills and Vertimills. The energy savings achieved varied from 10% to 40% for the ball mills and 30% to 60% for the Vertimills. Lastly, Bergerman (2012) investigated the operating conditions of the Sossego regrind circuit from 2006 to 2011 against design specifications and laboratory testing. The operating work index of this circuit varied from 5.2 kWh/t to 44 kWh/t over this 5 year period. The full suite of energy curves"

Jan 1, 2016

By V. ?. Chanturiya, G. P. Dvoychenkova, ?. Ye. Kovalchuk

"Several mineralogical investigations have revealed the composition of modified kimberlites and the mud generated during treatment of diamonds, which contains up to 50% clay minerals (e.g., talc, talcsaponite, chlorite-saponite, Na-saponite) and X-ray amorphous phase. We investigated the composition of the natural diamond surface in relation to the diagnosed minerals and established the sequence and conditions for mineral formation on the crystal surface under kimberlite processing conditions. This article suggests a method to destroy and further dissolve minerals on the crystal surfaces using water system electrolysis products, which makes it possible to restore the diamond hydrophobic properties. The application of chemically treated water in the foam separation cycle under the conditions of high recovery of diamonds made it possible to increase the content of the factory concentrate by 8.0%.INTRODUCTIONThe high content of the modified minerals in the kimberlite ore results in the formation of hydrophilic slicks on the surface of the crystals which decreases the diamond’s hydrophobic properties and increases the losses thereof in the process of grease and foam separation to 20-30% (Kurenkov, 1957; Chanturiya et al., 1998, 1999, 2005; Duikarev et al., 2000).The previous researches have revealed the fact that the prospective way of solving the problem of intensity of mineral impurities formation on the surface of the crystals and the increase of concentration parameters is reached due to application of physical and chemical stimulation techniques on the solid and liquid pulp (Stricland-Constable, 1971; “Improvement of the technology…”, 2006; Makarskii, Adodin & Tarasova, 2011; Chanturiya, Dvoychenkova & Trofimova, 2012). However, the main task of investigations to stipulate the objective achievement is the studying and justification of the reasons of the diamond surfaces covering by the mineral slicks"

Jan 1, 2016

By C. E. McCoy

This paper will discuss briefly loader shovel requirements and then present a detailed survey of electrical drive systems to meet these requirements. The survey in general will deal with the various electrical provisions for shovel drives, along with the advantages and disadvantages, and in particular will discuss the MG set and static D. C. drive systems. Also included will be some insight into the requirements for optimum electrical power at the shovels.

Jan 1, 1979