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The AMIRA Code of Practice and Guidelines for Metal Accounting was developed in response to demand from a number of sponsor companies, including one major platinum producer. Since its publication in 2007, the Code has become widely accepted in the mining industry world-wide as a guide for best practice in metal accounting. With the changes in the structure of the platinum mining industry in South Africa over the last 10?15 years, in particular, the starting up of a number of small platinum producers who must have their concentrate smelted and the contained valuable metals refined by third parties, the need for metal accounting systems that are accurate and have an acceptable level of precision has become even more critical to the success of a platinum-producing operation. The current state of metal accounting in the industry is discussed, and possible areas for improved accounting and associated metallurgical efficiencies are identified.

Jan 1, 2013

By T. Frömmer, H. Wagner

An inter-disciplinary geotechnical study has been carried out in an Austrian magnesite mine. The paper describes the how geological data, in situ and laboratory tests as well as subjective, empirical, geophysical and numerical methods have been used to identify critical areas in the mine. In einem österreichischen Magnesit Bergbau wurde in den letzten Jahren eine interdisziplinäre geotechnische Studie durchgeführt. Der Vortrag beschreibt den Einsatz subjektiver, empirischer, geophysikalischer und numerischer Methoden zur Identifikation geotechnischer Problembereiche Ces dernières années des études géotechniques interdisciplinaires sont effectuées dans une mine souterraine de magnésite en Autriche. Ce rapport trace l’application des méthodes subjectives, empiriques, géophysiques et numériques pour identifier les zones problématiques dans la mine

Jan 1, 2003

By M. Arlandi, J. C. Monge

In this paper, the finite element method is used to obtain deformations of a rock tunnel. More than 3,000 numerical simulations and calculations were carried out. The analysis of this results has allowed to achieve mathematical formulations and graphs, to obtain in advance support monitored displacements in tunnelling construction, so they can be predicted before excavation and supporting woks. The application of the presented formulations and charts will aid engineers to control tunnel monitoring, reducing decision time when problems occur. The analysis is limited to cases involving elastic behaviour of the terrain for tunnels of average to good quality in rock, and to excavation sections of average or smaller dimensions for road tunnels. The results show that, in all cases, mathematical expressions to obtain induced displacements around tunnel excavations, have similar pattern than Kirsch (1898) expressions for circular excavations. As corollary of the achieved results, a method to estimate in situ natural geostress ratio K0=sh/sv , by means of convergence measurements, is presented. In diesem Beitrag wurden die Verschiebungen eines Tunnels durch die Methode de Finiten Elemente berechnet. Mehr als 3000 numerische Simulationen und Berechnungen wurden ausgeführt. Die Analyse dieser Resultate hat es ermöglicht, mathematische Formeln und Grafiken zu entwickeln, die zur Voraussage der Verschiebungen in Tunnel dienen, auch unter Betrachtung der verschiedenartigen Abstützungen. So können die Verschiebungen vor den Erdarbeiten und dem Bau der Abstützung abgeschätzt werden. Die abgeleiteten Formeln und Grafiken werden vor allem einen grossen Dienst für Ingenieure bei der Mithilfe zu zeitsparenden Entscheidungen im Tunnelbau und bei der Tunnelkontrolle leisten. Die analysierten Fälle sind auf eine elastische Modellierung des Baugrunds beschränkt, sowie auf eine mittlere bis gute Qualität des Felsens und auf die Aushebung von Abtragungsabschnitten mittlerer oder geringer Grösse für den Strassenverkehr. Die Resultate zeigen, dass in allen Fällen die hergeleiteten Formeln zur Berechnung der durch den Tunnelbau verursachten Verschiebungen um den Tunnel die gleiche mathematische Struktur haben wie diejenigen von Kirsch (1898) für kreisförmigen Bodenaushub. Als Korollarium der ausgeführten Berechnungen wird eine Methode zur Abschätzung der vorherrschenden in situ Geospannungs-Verhälniss K0=sh/sv angegeben, die von den Messungen der Verschiebungen im Tunnel ausgeht. Dans cet article, la méthode des éléments finis est utilisée pour obtenir les déformations d’un tunnel creusé dans la roche. Plus de 3000 simulations numériques et calculs ont été effectuées. L’analyse de ces résultats a permis de définir des modèles mathématiques et des abaques afin de prédire, avant l’excavation et les travaux de soutènement, les déplacements auscultés pendant la construction du tunnel. L’application de ces modèles et abaques permettra donc aux ingénieurs de contrôler les déplacements durant l’auscultation du tunnel et de réduire le temps de décision lorsque des problèmes surviennent. L’analyse est limitée au cas du comportement élastique du terrain pour des tunnels creusés dans de la roche de moyenne a bonne qualité, et à de sections d’excavation de petites à moyennes dimensions pour des tunnels routiers. Les résultats montrent que, dans tous les cas, les expressions mathématiques permettant d’obtenir les déplacements induits autour des excavations de tunnel, présentent des similitudes avec celles de Kirsch (1898) pour des excavations circulaires. Comme corollaire aux résultats obtenus, une méthode pour estimer le rapport des

Jan 1, 2003

By L. K. Witika, J. H. Masinja

"Investigations of flotation characteristics of Lumwana and Kansanshi ores using formulated frothers were carried out. Of the six frothers tested, two came from the alcohol family, two from the glycol family and last two were formulated products. The initial work involved determining the optimum mesh of grind and frother dosage for Lumwana and Kansanshi ores. Further work involved carrying out surface tension, bubble size and froth stability measurements. Finally, water recovery tests were conducted at Lumwana and Kansanshi mine sites. For froth stability tests, six frothers were tested on a two-phase (water–air) system using the Bikerman column flotation cell, while water recovery tests were conducted using a total of seven frothers, including the standards for each plant. The results of the testwork showed that (i) although a stable froth is essential for optimum recovery of valuable minerals, a higher molecular weight frother, like Dowfroth 250, caused poor selectivity when used on fine ores and (ii) a lower molecular weight frother was suited for Lumwana ore, while a mid to higher molecular weight formulated product was suitable for Kansanshi sulphide ore. INTRODUCTION Investigations of flotation characteristics of Lumwana and Kansanshi ores using formulated frothers were carried out. The initial work of this project involved determining the optimum mesh of grind and frother dosage for Lumwana and Kansanshi ores. Further work involved carrying out surface tension, bubble size and froth stability measurements. Finally, water recovery tests were conducted at Lumwana and Kansanshi mine sites. In order to investigate the gangue entrainment levels in the Lumwana and Kansanshi sulphide ores, two well-known methods (froth stability and water recovery) were used. Firstly, froth stability tests were conducted using six frothers, two from the glycol family (Dowfroth 200 and Dowfroth 250), two from alcohol family (MIBC and pine oil) and other two from the formulated family (Betafroth 20 and Betafroth 245), at the University of Cape Town’s Centre for Mineral Research (CMR) laboratories. Froth formation and stability measurements were conducted using the Bikerman column flotation cell."

Jan 1, 2015

By L. Arnberg, E. Ott

The microstructure of ferrosilicon is important since it controls the disintegration of the material during crushing and thus the generation of fines. Therefore a study of the microstructure formation during solidification of pure FeSi(75wt%Si) and FeSi(75wt%Si) containing 1.2wt%Al and 0.2wt%Ca has been initiated. The material has been cast into rods of 8mm diameter, which have been remolten by induction heating and directionally solidified in a Bridgman apparatus. This allows the temperature gradient and the growth rate to be controlled independently. The temperature history during solidification has been recorded by a thermocouple in the melt. Growth rates have been varied between 5 and 400µms-1 and temperature gradients between 3 and 14°Kmm-1. The microstructures show a large dependence on the solidification conditions. The crack formation in the alloys has been studied and found to be strongly related to the microstructure.

Jan 1, 2004

Quantitative seismology is an important tool for investigating mineinduced seismicity and the quantification of the seismic rock mass response. The spatio-temporal interpretation of seismic data within an ever-changing three-dimensional mining environment provides some challenges to the interpretation of the rock mass response. A grid-based approach for the interpretation of spatial variation of the rock mass response provides some benefits compared with approaches based on spatial filters. This paper discusses a grid-based interpretation of seismic data. The basic methods employed in the evaluation of the parameter values through space are discussed and examples of applications to different mine sites given.

Jan 1, 2014

By M. Abdellatif

Keywords: Magnesium, pyrometallurgy, Mintek Extensive testwork on atmospheric thermal magnesium production has highlighted certain important fundamental and operational factors that have a major influence on magnesium extraction and its extraction rate, the condensation efficiency of magnesium, as well as on the quality of the condensed metal. The possible impact of these factors on the selection and preparation of raw materials, recipe choice, furnace electrical energy consumption, and on the refining requirements of the crude magnesium is discussed. Selected pilot plant operational and metallurgical data are also presented.

Jan 1, 2006

By M. Shahabi, M. Kashfi

This paper briefly describes the excavation procedure of a powerhouse, comprising of its incremental excavation, reinforcement measures, and the installed monitoring system. During the first phase of excavation, the data obtained from monitoring of the behavior of Mudstone layers were used to recommend extra support measures. These data are also used to design the support of the powerhouse during its extension phase. In diesen bericht wird die bohrmcthode von kraftwerk ecavation in stupenweise dargestelt, und in die richtung d.sicherung, Mit hilfe von monitoring systeme. Die monitoring in (mudstone) schichten ist an schutz in bohrung entworfen und montiert in diese methode in K.W. fase 1 schutzung das K.W. in erweiterung der K.W. das berte auserwelt worden ist Cet article décrit brièvement le procédé d'excavation d'une centrale électrique, comportant de son excavation incrémental, de mesures de renfort, et du système de surveillance installé. Pendant la première phase de l'excavation, les données obtenues à partir de la surveillance du comportement des couches de schiste ont été utilisées pour recommander des mesures supplémentaires de soutien. Ces données sont également utilisées pour la conception de la soutènement de la centrale électrique pendant sa phase d’extension.

Jan 1, 2003

By David Brown, Dirk van Dyk

Horizontal rotating mills are being used all over the world associated with 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 with are not always fully understood. Failures are therefore experienced, over time in the industry, which can therefore not 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 analyze 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 analyze 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 conditions are better understood, and the effect on the fatigue life of the mill gearing components, 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, 2007

By T. R. Marshall

SAMREC (The South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves) Clause 7 notes that ‘Documentation detailing Exploration Results, Mineral Resources and Mineral Reserves from which a Public Report is prepared must be prepared by, or under the direction of, and signed by a Competent Person.’ Similar statements with respect to Competent Valuators (CVs) and Qualified Reserves Evaluators (QREs) are contained in the SAMVAL (South African Code for the Reporting of Mineral Asset Valuations) and SAMOG (South African Code for the Reporting of Oil & Gas Resources) codes respectively. What does it mean to be a Competent Person (CP) in the context of compiling/signing-off on SAMCODE (South African Mineral Code) compliant documents? What do the registration and experience requirements mean? Who is ultimately responsible for the report and what does such responsibility prescribe?

Sep 1, 2021

By K. M. Phamotse, A. S. Nhleko

"*Paper written on project work carried out in partial fulfilment of BSc (Mining Engineering) degreeSynopsisLiqhobong Mining Development Company (LMDC) has been experiencing problems with boulders after blasting where the fragment sizes exceed the maximum of 800 mm as per mine standard. As a result, the mine has employed various methods to improve the fragmentation. The goal is to produce a run-of-mine (ROM) feed that does not choke the crusher and cause delays in production. In order to achieve this goal, fragmentation distribution within the fines and coarse envelope must be optimized through effective planning of blasting activities and accurate execution.The mine determined the fines-coarse envelope within which the entire crushing system can handle fragments using Split Desktop software. It is expected that both the predicted and actual fragmentation curves lie within that envelope for optimal fragmentation. The Kuz-Ram model with blast design parameters of 2.6 m for burden, 2.8 m for spacing, and 127 mm hole diameter was used to predict the fragmentation. The results show that the blast design parameters may need altering to achieve optimum fragmentation. Furthermore, the execution of the drilling and blasting may be the cause of the fragmentation problems. The mean fragmentation size (X50) differs greatly, unlike the uniformity index (n)s values which are relatively close to each other (0.6 to 2.2). The mean squared error (MSE) values have a large range. A proposed solution is a modified burden, spacing, and hole diameter. It is concluded that blast design parameters need to be reviewed in order to obtain correct predictions. IntroductionFragmentation has an impact on the mine production cycle which comprises, inter alia, drilling, blasting, loading, hauling, and crushing. Correct fragmentation as set by the plant design is important as it reduces the time lost due to secondary blasting and/or loading difficulties. In this paper we analyse blast results at Liqhobong Mining Development Company (LMDC) in Lesotho for a period of six months. This project was undertaken to observe the trends from the blasts and to identify whether any discrepancies exist in the overall blast information. The period under study included 16 blasts."

Jul 1, 2019

By J. J. Dekker

Controlling noise has proven difficult in mining, and noise-induced hearing loss (NIHL) remains common. In 2008, a South African Mine Health and Safety Council study focused on small- to medium-sized mines in relation to the milestones set by the industry to prevent NIHL. An evaluation of the compliance of ten diamond, sand, aggregate and Ready mix concrete mines and production sites with standards, legislation and best practice guidelines relating to NIHL prevention was conducted, using a noise compliance audit tool. The findings indicated that all mines surveyed had poor compliance with the international standards, compliance with International Standards Organization standards being the poorest. There was a clear distinction between the small and the medium-sized mines in their compliance with local standards and legislation (ranging from 14 per cent to 66 per cent). The areas of best compliance were audiology and medical examinations. The lower-than-expected compliance was largely attributable to shortcomings in hearing conservation programmes for occupational noise. Initiation of remedial practices in the small- to medium-scale mining sector to facilitate improvements in NIHL prevention and compliance with standards and legislation is recommended. Keywords Hearing conservation, small-to-medium mines.

Jan 1, 2011

By Z. W. Nkosi, M. Sephton, J. H. Potgieter

The exhaust system is a complex assembly of various components performing important tasks in harsh environments. Carbon steels have been used extensively in exhaust systems, but pressure for lower cost, increased fuel efficiency; lower hazardous emissions, weight savings and increased life expectancy have shifted the emphasis to stainless steels. In response to the growing consumption of stainless steels in automotive exhaust systems, the need to properly evaluate their corrosion resistance properties in order to ensure their appropriate use, has increased substantially. This paper evaluated the most common corrosion and oxidation tests developed that are used and applied it to four common stainless steels often employed in hot end exhaust components. In a summary considering the weight loss of an alloy, it general corrosion rate and pitting resistance under all the test conditions for hot end exhaust components, results indicate that 434 was by far the most corrosion resistant alloy, followed by 1.4509 and 321, and lastly 304 was the least corrosion resistant. In general, the ferritic stainless steels, especially 434, outperformed the austenitic ones under all the test conditions.

Jan 1, 2006

By N. M. Skarbøvig

Safety nets have been used selectively in several South African mines over the years. Recently, however, an increased emphasis on mine safety has seen a resurgence of their utilization underground. This renewed interest has, however, also raised questions about the design and performance of these nets and their practical applications underground; these are the subjects of this paper. Generally, mine safety nets are used to protect personnel from falling rock in temporarily supported development ends, tunnels, ASGs and stopes. These diverse applications each require specific net designs, resulting in a wide product range. As a rule, however, mine safety nets need to carry specified static or dynamic loads with the least possible deformation. Because of the application-specific characteristics of mine safety nets, there is no South African national standard for them. Consequently, neither the SABS, nor the CSIR, performs standard tests on these components. In 2007, therefore, SIMRAC made available their Savuka facility for the testing of mine safety nets; the Savuka drop test became the accepted industry test standard for mine safety nets. From late 2007 to mid 2009, Norsenet, in collaboration with SRK Consulting, the designated operators of the site, conducted approximately 200 tests, which formed the core of Norsenet's database of safety net performance under various loading conditions. The test specimens comprised a wide range of net materials and config¬urations; the materials included: high density polyethylene, polypropylene, polyester, nylon, as well as a blend of polyester and polypropylene used primarily for reinforcement ropes. Net configurations encompassed the following parameters: net type, i.e., knotted nets or sewn nets; net strand type, i.e., braids, twines, or webbing; strand size; mesh size; mesh orientation, i.e., parallel or oblique to the net edge; net edge reinforcement, i.e., knotted, tied, with or without reinforcement ropes; internal reinforcement ropes, i.e., diagonal ropes and/or orthogonal ropes; as well as net attachment options, including loops and chainlinks. From the number of variables listed above, and the limited number of tests available, it can be appreciated that the findings of the test series required careful scrutiny. Nevertheless, principal performance factors clearly emerged: besides the obvious net mesh variables, such as net strand material, strand diameter and mesh size, it was the configuration of the reinforcement ropes and their attachment to the net panel which had the strongest influence on net performance. All the structural elements of a safety net need to work together to transfer the imposed load from the net panel, through the reinforcement ropes, to the net attachment points. In this load transference chain, the weakest link limits the strength of the structure. From this development work, Norsenet has gained valuable expertise to custom-design and manufacture nets to clients' specifications. The examples presented in the paper will also show the experience acquired in the installation of nets underground. Future work will include the establishment of a state-of-the-art net testing facility at Norsenet's factory in Vredenburg.. Keywords Mine safety net, safety net, protective device, mine safety, safety net design, safety net performance, safety net applications.

Jan 1, 2011

By A. Haque

The shear behaviour of infilled joints produced from ordinary gypsum plaster (gyprock) and bentonite was investigated in the laboratory under Constant Normal Stiffness (CNS) conditions. Shear tests were performed on saw-tooth profiles having Joint Roughness Coefficients (JRC) of 4.75 and 9.25 under an initial normal stress (sno) of 0.30 to 1.10 MPa, and at a normal stiffness (kn) of 8.5 kN/mm. Test data under the same sno and infill thickness to asperity height ratio (t/a) were analysed for two different sets of JRC. The peak shear stress plotted against the t/a ratio under constant sno revealed an increase in peak shear stress with the increase in JRC, up to a t/a ratio of about unity. The effect of roughness on the peak shear stress was observed to be minimal when the t/a ratio exceeded 1.40. A mathematical model for the prediction of peak shear stress due to the increased infill thickness has been developed based on a hyperbolic stress-strain relationship and energy balance principles. The model predictions are in good agreement with the laboratory observations. Le comportement de cisaillement des joints remplis produits à partir de plâtre ordinaire et de bentonite a été étudié dans le laboratoire sous des conditions de rigidité normales constantes. Des essais de cisaillement ont été réalisés sur des profils en dents de scie ayant des coefficients de rugosité des joints (CRJ) variant de 4,75 à 9,25 sous un effort normal initial (sno) de 0,30 à 1,10 MPa, et une rigidité normale (kn) de 8,5 kN/mm. Le résultat des essais conduits sous la même contrainte et épaisseur de remplissage au rapport aspérité/hauteur (t/a) ont été analysés pour deux ensembles différents de CRJ. La variation de l'effort de cisaillement maximal contre le rapport t/a sous une contrainte normale constante a indiqué une augmentation de l'effort de cisaillement maximal avec l'augmentation du CRJ, jusqu'à un rapport de t/a proche de l'unité. L'effet de la rugosité sur l'effort de cisaillement maximal a été minimal quand le rapport t/a a excédé 1,40. Un modèle mathématique pour la prévision de l'effort de cisaillement maximal dû à l'épaisseur accrue du remplissage des joints a été développé sur la base de la variation entre contraintes hyperboliques et déformation et sur des principes de bilan énergétique. Les prévisions du modèle sont en bon accord avec les observations de laboratoire. Das Scherverhalten in mit gewöhnlichem Gips und Bentonit gefüllten Klüften wurde im Labor unter Bedingungen konstanter Normalsteifheit (CNS) untersucht. Scherversuche wurden durchgefürt für Sägezahnprofile mit Werten des Fugenrauhigkeitskoeffizienten (JRC) von 4.75 und 9.25 unter Normalspannungs-werten (sno) von 0.30 bis 1.10 MPa, und bei Normalsteifheit (kn) von 8.5 kN/mm. Testresultate für gleiche Werte von sno und Verhältnis Fülldicke zu Rauhigkeit (t/a) wurden untersucht für zwei verschiedene Werte von JRC. Die Beziehung zwischen maximaler Schubspannung und und t/a Verhältnis unter konstantem sno zeigte einen Anstieg der maximalen Schubspannung mit zunehmendem JRC, bis zu einem t/a Verhältnis von etwa 1.0. Der Einfluss der Rauhigkeit auf den Maximalwert der Schubspannung war minimal solange das t/a Verhältnis den Wert von 1.40 überstieg. Ein mathematisches Modell wurde entwickelt für die Vorhersage der Schubspannung die von zusätzlicher Fülldicke erwartet werden kann, ausgehend von einer hyperbolischen Spannungs-Dehnung Beziehung und dem Energiegleichgewichts-prinzip. Die Modellvorhersagen zeigten gute Uebereinstimmung mit den Laborbeobachtungen.

Jan 1, 2003

By A. J. Lynch

Mineral processing models have been discussed for many years but it was not until digital computers became available about 1960 that serious attempts at circuit simulation could be carried out. Even then the work was primarily academic until PCs could be used by engineers in plants and design offices in the mid-1980s. Since then simulation has moved quickly and it is now at the point that most processes can be simulated reasonably accurately for purposes of design and optimization. There are still some significant deficiencies, notably in dry grinding and separation, and in the chemical interactions in flotation. Future work will involve: ?improvements of existing models ?dynamic simulation for automatic control and, in particular ,for training which is a weak link ?using advanced simulation models to predict liberation and separation from data acquired from SEM-based liberation analysers. Eventually mineral processes models will be part of total simulation systems which will incorporate mining and downstream processes including all environmental impacts.

Jan 1, 1999

By Q. G. Reynolds

Keywords: Pyrometallurgy, furnace, DC, reverse polarity, dual-electrode The dual-electrode direct current (DC) arc furnace uses two graphite electrodes, one connected as cathode, and one as anode. Such an arrangement avoids some of the design difficulties associated with the anode hearth traditionally used in single electrode and twin-cathode DC furnaces, but can introduce other design and operational difficulties including deflection of the arcs toward the furnace walls. Counter-intuitively, both arc jets in a dual-electrode furnace travel from the electrode down to the bath surface, despite carrying electric current in opposite directions ? this is suggested in the theory of the governing equations of arc formation, and confirmed by experiments using high-speed photography. The dual-electrode arc system at small pilot-plant scale is studied using a transient magneto-hydrodynamic model capable of predicting arc deflection and interaction from first principles, and the results are compared to the behaviour of twin-cathode systems at similar power. Finally, a simple arrangement of the furnace busbars, M configuration, is shown to provide some passive protection against arc deflection.

Jan 1, 2011

By B. W. J. van Rensburg, M. J. Schmidt

Bulk materials handling systems are extensively used in the mining and minerals industry, where a fairly high incidence of structural failure is experienced, notwithstanding design compliance with appropriate standards. A number of case studies are explored to demonstrate how insufficient controls or protection systems have contributed to structural failures on mobile bulk handling equipment. The importance of design integration across engineering disciplines is highlighted. The revision of ISO 5049-1 (1994) is proposed to provide specific rules and guidelines pertaining to machine protection systems. It is further recommended that the structural design engineer of the original equipment manufacturer(OEM) fulfils a more prominent role during the final acceptance and handover of mobile bulk handling equipment, with specific reference to protection systems.

Jan 1, 2015

By C. J. Badenhorst

The scope of this project was to research, develop and eventually produce a personal occupational hygiene and safety exposure monitor system to assist in recording and analysing various stress factors that could affect the health, wellness and safety of employees, i.e. that could result in injury or ill health of workers, create stress build-up within individual workers that could negatively affect worker alertness and safety, and, may even result in permanent disability or death. Utilized systems at the time were all reactive, whereas the DOHEMS (Proactive Digital Occupational Hygiene and Safety Exposure Monitoring) System enabled the measurement of exposure (and associated risk) in a proactive manner via real-time exposure and digitized recordings. The idea of the development was to create a unit that is so cost effective, small and light that every worker can use a system on a daily basis. The development will eventually replace current, bulky and expensive monitoring equipment. The device must be a portable battery operated device and monitor the immediate working environment by periodic sampling for vibration, noise, toxic gasses (NO/NOX/CO/VOC, etc.), body temperature and heart rate. The samples must be time and date stamped, utilizing a real-time clock (RTC) synchronized with the closest regional secondary time source and related to synchronized real-time video captured samples. These samples are then recorded onto a rugged non volatile storage device with the capacity to store a vast number of samples covering the entire working shift of eight (8) hours plus. The system has been fitted with a clear visual local alarm indication system, indicating any excessive exposures or stresses, for the worker?s supervisor to respond to. This system allows for a pro-active approach. The system is also a wireless system (to the external environment) so as to not affect the mobility of an employee and flameproof to allow for use in explosive environments. Keywords: safety, digital, exposure, monitoring, proactive.

Jan 1, 2010

By Ishwinder Grewal, Michael Fullam

Many factors affect the overall performance of a gravity circuit beyond that of the primary gravity recovery device. It is critical to examine the gravity circuit in its entirety in order to determine the dominant operating variables that affect overall performance. Knelson has developed a mathematical model which has been used to assist in the design of gravity circuits, and in particular, in making accurate predictions of plant scale gravity recovery. More recently, inclusion of recovery by particle size class and additional data from various mine sites and research studies has made the model more robust. The model is now able to predict GRG (gravity-recoverable-gold) recoveries using various devices such as centrifugal concentrators, shaking tables, jigs and flash-flotation within the grinding circuit. The benefits derived by these recent advancements in modeling capability are two-fold; the first is as a tool to assist in circuit design and correct equipment selection and the second is as an analytical tool to help to evaluate and enhance the performance of existing gravity circuits.

Jan 1, 2006