Search Documents

"With millions of dollars and thousands of lives at stake, the Iron Ore Company of Canada (IOC) turned to a private wireless network for help.IOC needed a network that possessed the ability to adapt to changes in a nanosecond and to function seamlessly in the most rugged of environments.Canada’s largest iron ore producer required a private wireless network powerful enough to support all mine applications and deliver all data to one central point — without any existing cellular/3G/Wi-Fi coverage.Operations at IOC, a leading global supplier of iron pellets, involved dispatch, drill management and equipment monitoring, pump control and remote video that must service three distinct pits. Due to its setup, the facility does not offer a great deal of flexibility for transmitting signals.IOC serves a robust customer base made up of North American, European and Asian steel producers. It also employs nearly 1,900 people. Catastrophic death and destruction are two very real potential consequences of system communication failure.Technology for tough terrainKinetic mesh technology was born in the wake of the 9/11 terrorist attacks on the United States, one of the most high-stakes emergency situations in U.S. history. The failure of the communications infrastructure on a massive scale that day underscored the need for networking technologies that could provide service even in the most chaotic of conditions.Kinetic mesh networks allow organizations to deploy networks at sites where communications infrastructure has been compromised, as well as quickly establish networks in places where they did not previously exist. Kinetic mesh networks have also demonstrated a better ability to adapt to network changes on-the-fly versus other types of networking technologies."

Jan 1, 2015

By M. S. Celik, H. Du, J. D. Miller, F. Cheng, O. Ozdemir

"In this paper, recent progress with respect to the flotation chemistry of soluble salt minerals is reviewed, and some of the more relevant issues including the hydration states of ions, the interfacial phenomena of salt surfaces and the flotation behavior of selected soluble salts are discussed. Due to the high solubility, the flotation of most soluble salts has to be carried out in their saturated brines. Anecdotal evidence has suggested that the hydration states of the ions have significant influence on the physicochemical properties of the solutions, the surface charge and wetting characteristics of the minerals, the collector adsorption states and, further, the flotation behavior of the soluble salts. In this regard, reviewing past research findings, efforts are made to establish a correlation between the ion hydration states with the flotation behavior of the soluble salts. Further, advances in understanding the significance of colloid adsorption involved in the soluble salt flotation process are addressed, and future research efforts to understand the soluble salt flotation chemistry are suggested.IntroductionSoluble salt minerals are essential raw materials for the production of a variety of commodities, fertilizers, potassium hydroxide, soda ash, magnesium compounds and other chemicals. These soluble mineral resources can be processed using flotation technology and, currently, more than 80% percent of the world’s potash is produced by the selective flotation of KCl crystals (sylvite) from other salt crystals, predominately NaCl (halite) and other more complex salts (Searls, 1990). Despite the successful application of flotation technology in the potash industry, the mechanisms for collector adsorption on soluble salts have not yet been fully understood and, therefore, have been of considerable interest to flotation researchers for many decades."

Jan 1, 2015

By F. Hassani, J. Peck, D. J. Lucifora

The performance of a rotary blasthole drill is heavily dependent on the material being drilled. This material is a microcosm of the in-situ geology that makes up the surface mine in which the rotary blasthole drill is deployed. The performance metrics that are influenced by the in-situ geology are penetration rate (distance drilled per unit time), rotary torque and to a lesser extent rotary speed and vibration. For simulation and testing purposes it is useful to have a validated plant model based upon the application of study. Once validated, a plant model can be used to perform simulation based testing as a supplement and possibly in place of more expensive and logistically complex field testing. Previous studies in the field of rock mechanics have supplied proven models that relate the performance of a rotary blasthole drill to the material being drilled for a given rock type with a given drill bit. In this study, field based experiments were conducted in an active surface mine on a working rotary blasthole drill and the corresponding monitoring while drilling (MWD) data was recorded. Data analysis was then performed on the collected field data. The techniques used successfully fit the collected MWD data to the previously proven rock mechanic models. This paper explores the theory relating rotary blasthole drill performance to the material being drilled, illustrates the required data collection and data analysis techniques, and demonstrates the ability of these techniques and the known rock mechanic models to provide a simulated plant model for the drilling process that can then be validated. This validation is also discussed.

Jan 1, 2015

By R. L. Grayson, S. S. Eslambolchi

"In making strategic economic decisions, it is important for a mining company to gain insights on the impact of significant political, social and economic issues when planning for present and future mines. The size of any mine, measured by the average number of employees working in the mine, will likely vary according to the pressures generated by the significant issues from one year to another. The objective of this study is to develop a model that represents U.S. underground coal mine size transitions during the period 2002-2012 using data derived from the MSHA databases. Coupled with information on significant issues over the past ten years, this model is used to gain insight on the impact of the issues on mine sizes. Results indicate that the structural impact of the combined driving pressures can be discerned by examining the year-to-year stability of mine-size categories. The effects of The MINER Act, the Obama Administration environmental policies on coal, and the coal market are evident. The lessons learned from these analyses give good insights on what the industry and market responses have been on the structure of the underground coal industry over the period of study. INTRODUCTION It is apparent that key driving issues affect the structure and viability of the coal industry. The driving issues may be political, social, and/or economic in the final analysis, but are generally rooted in reaction to dramatic and publicized events or movements. Mine disasters, an increase in miners’ disease prevalence, strife in the coal fields, and negative environmental impacts on air, land or water can capture the attention of the media and the public. Some of the issues occur over a long period of time, like the current global climate change movement. The coal industry veteran can sense the changes in political and social sentiment, and attempt to react to the economic repercussions; however, the insights from the media and from unique combinations of driving pressures are difficult to fathom. Thus decisions made on inadequate information related to the driving pressures and their likely impacts could lead to missteps in corporate and market restructuring. One way to gain some more insight on the potential impacts is to examine the complicated restructuring of mine operations in reaction to the driving pressures of the recent past. This paper examines an 11-year history of the changes in the underground coal industry structure, as reflected by changes in the numbers of mines in various statuses by mine-size categories. Superimposed on the results of mine-size changes is a mapping of the key driving pressures that occurred over the same period, 2002-2012. It is assumed that using this methodology, some important insights can be gained on the immediate and delayed responses to the driving pressures during that period."

Jan 1, 2015

By C. Musingwini, M. Mohutsiwa

"SynopsisCapital cost estimates are important in decisions on whether a project will be approved, mothballed, or abandoned. In South Africa, junior coal miners do not have extensive databases of historical projects from which to estimate capital costs. The purpose of this paper is to establish formulae that can be used for estimating capital costs of developing coal mines in a coal-producing country, using South Africa as a case study. The costs are estimated to an error of magnitude level of -30% to +50%, which is suitable for a concept study level, using a parametric estimation technique. The study uses data from completed coal mining projects from selected coal-producing countries. Three formulae are developed and presented for estimating capital costs of underground bord and pillar, surface shovel and truck, and dragline operations.IntroductionCapital cost estimates play a critical role in deciding whether projects will proceed, be delayed, or abandoned. It is therefore important that capital cost estimates are carried out accurately as determined by the estimation guidelines based on the level of estimation conducted (Shafiee and Topal, 2012). The lack of literature on estimation of capital costs in many coal mining countries is adversely affecting junior coal miners, since they do not have an extensive database of historical projects on which to base estimations. In South Africa, the difficulty in estimating capital costs is attributable to lack of publicly available data on completed South African mining projects (Hall, 2013)."

Jan 1, 2015

By P. Carlone, A. Astarita, F. Rubino

Cold gas dynamic spray is an innovative technology allowing the deposition of thin metallic layers on a bulk or sheet substrate. Titanium on aluminum deposition is very attractive to the aeronautic industry, due to the enhanced corrosion resistance and wear properties of titanium coating as well as its improved compatibility with CFRP, preserving the reduced cost of aluminum substrate. One main drawback, however, is related to the micro-porosity of the deposed layer, negatively affecting the corrosion barrier performance. In this paper, the effect of selective laser post-treatment on pure grade 2 titanium coatings on AA2020-T3 sheets was experimentally and numerically investigated. Morphological features, microstructure and chemical composition of the treated zone were assessed by means of optical microscopy, scanning electron microscopy and energy dispersive X-ray spectrometry. Microhardness measurements were also carried out to evaluate the mechanical properties of the treated coating. A numerical model of the laser treatment, based on a finite volume scheme, was implemented and solved to simulate the process and discuss the experimental outcomes. Obtained results highlighted the key role played by heat input and dimensional features on the effectiveness of the treatment.

Jan 1, 2015

By J. E. Sepulveda, R. Morrow

"In full scale mineral grinding operations, the steel balls normally utilized as auxiliary grinding media get to be consumed at different specific rates, as determined by 3 basic mechanisms: abrasion/corrosion (wear), impact ball breakage and impact surface spalling, the latter relating to the removal of rather small pieces of steel coming off the exposed surface of the balls due to repetitive impact with other balls in the charge or the surrounding mill liners. In conventional ball milling applications, the clearly predominant mechanism is gradual wear by abrasion/corrosion. In the case of SAG mills, where the make-up balls may be as large as 6”f diameter, breakage and spalling mechanisms are significant contributors to total ball consumption, although not to the extent of overriding wear mechanisms.Ball wear has been well characterized by the Linear Wear Theory, as presented at the last CMP 2014. Impact breakage has been customarily monitored, at the ball manufacturing site, via Drop Ball Tests (DBT) consisting of repeatedly dropping balls from a standard height and accounting for the number of broken balls and the weight loss (spalling) of the remaining unbroken balls. When properly conducted, DBT’s should provide meaningful indications of the breakage and spalling resistance of large diameter balls. The current publication is focused on the interpretation and projection of DBT results to full industrial scale, taking into account all 3 mechanisms of grinding media consumption in SAG mills.INTRODUCTIONA thorough, quantitative understanding of the independent contribution of all active grinding media consumption mechanisms is of the highest practical relevance, particularly in semiautogenous (SAG) milling operations where ball breakage and spalling can not be ignored or neglected, as it has been normally acceptable for conventional ball milling processes. The high severity impact conditions currently imposed in typical SAG mill environments create serious challenges to the manufacturers and suppliers of large diameter (5”–6”) SAG balls, whose products must be capable of surviving such harsh operational conditions with minimum breakage or spalling."

Jan 1, 2015

By G. J. McTeer, D. L. Verhelst, D. J. Rioux

Teck Metals Ltd. operates an integrated zinc-lead complex at Trail, British Columbia, Canada. Since 1997, KIVCETTM flash smelting technology has been utilized for the treatment of zinc plant residues and lead concentrates. Trail Operations’ furnace uses four water-cooled jackets for bullion tapping. This paper provides an overview of KIVCET bullion tapping for the past 16 years, and discusses successes and challenges encountered with respect to operations, training and monitoring.

Jan 1, 2015

By Rob Boom, Yasuyuki Tozaki, Frank M. Wheeler

Selection of a suitable site for a metallurgical plant is crucial for the success of the business case. For a brownfield project, with the decision to locate the project on a site with existing production facilities and activities, the selection of the site has been made. For a greenfield project, important economic and logistical considerations include proximity to primary and secondary resources and/or to the market, infrastructure, and access to energy and water. National and regional aspects, including the social license to operate, can be decisive in final site selection. Key to recruiting and retaining a labour force are proximity to urban areas, along with weather and health conditions at the site. Risk factors include site geotechnical parameters and topography, contamination, as well as probability and types of potential natural disasters.

Jan 1, 2015

One of the seminal pioneering papers in reserve evaluation was published by Danie Krige in 1951. In that paper he introduced the concept of regression techniques in providing better estimates for stope grades and correcting for what later became known as the ‘conditional bias’. In South Africa, the development of this approach led to the phenomenon being dubbed the ‘regression effect’, and regression techniques ultimately formed the basis of simple kriging in Krige’s later papers. In the late 1950s and early 1960s, Georges Matheron (1965) formulated the general theory of ‘regionalized variables’ and included copious discussion on what he termed the ‘volume-variance’ effect. Matheron defined mathematically the reason for, and quantification of, the difference in variability between estimated values and the actual unknown values. In 1983, this author published a paper that combined these two philosophies so that the ‘regression effect’ could be quantified before actual mining block values were available. In 1996 and in some earlier presentations, Krige revisited the regression effect in terms of the conditional bias and suggested two measures that might enable a practitioner of geostatistics to assess the ‘efficiency’ of the kriging estimator in any particular case. In this article, we revisit the trail from ‘regression effect’ to ‘kriging efficiency’ in conceptual terms and endeavour to explain exactly what is measured by these parameters and how to use (or abuse) them in practical cases.

Jan 1, 2015

By Saeed Zhandi, Behdeen Oraee

"Rock bursts remain an important problem in longwall coal mining. These bursts are due to a sudden and severe failure of rocks from a high stress concentration in deep underground excavations that occur with the instantaneous release of strain energy stored in the rocks. They can potentially cause irrecoverable damage to equipment and personnel, thus accurate rock burst prediction and control is expected to be carried out by the mine design engineer. As a result, this can constitute major challenges for said engineer. In this paper, forensic engineering has been used to evaluate the possibility and extent of rock bursts in deep coal mining. For this purpose, established mining engineering principles, including factors influencing the severity of rock bursts, have been incorporated in the forensic engineering technique. The analyses took place in five steps:• Assessment of regional and local conditions prior to the event• Assessment of conditions after the event• Hypothesize plausible ways in which pre-event conditions can become post-event ones• Search for evidence that either denies or supports various hypotheses• Apply engineering knowledge to relate the various facts and evidence into a cohesive scenario of how the event may have occurred.The paper concludes by demonstrating a method for predicting rock bursts and preventing their reoccurrence. The methodology used in this paper, together with the results obtained, can serve as useful tools for the coal mine design engineer in the primary evaluation of rock burst potential in underground coal mines.INTRODUCTIONA rock burst is defined as the sudden and great failure of rocks due to a high stress concentration in deep underground mines. This phenomenon occurs with the instantaneous release of strain energy that is stored in the rocks, and can cause irrecoverable damages to both equipment and personnel (see Figure 1). Rock bursts pose a hazard owing to their lake of predictability; in fact, research into understanding rock burst mechanics and implementing techniques for their monitoring and prediction has been taking place for over 50 years."

Jan 1, 2015

By Franz-Werner Gerressen, Manfred Schoepf

"Diaphragm walls are known as underground structural elements commonly used as retention systems for excavation pits and shafts and permanent foundation walls or elements. It can be anticipated that, with the increasing trend of utilizing more and more underground space to accommodate environmental considerations and urban/suburban development, there will be an increasing requirement for diaphragm walling in even more complex conditions. Complex and/or challenging conditions in terms of ground conditions have a major impact in regards of choosing the right tools for excavation purpose. Complex conditions in terms of space limitations, especially for inner city job sites, require specifically adapted solutions for slurry, spoil, reinforcement and concrete handling and the related logistic to ensure smooth production. Furthermore, one focus will be given to the QA/QC topics of the production process. Real time installation control, data transfer and reporting systems become more and more important ensuring the five dimensions of a jobsite. Therefore, the paper will describe the construction method and the sequence of activities required for the construction of diaphragm wall systems with the focus on the cutter technology. It will describe also the main equipment which will be needed to execute these works under the various conditions INTRODUCTION Diaphragm walls are known as underground structural elements commonly used as retention systems for excavation pits and shafts and permanent foundation walls or elements. It can be anticipated that, with the increasing trend of utilizing more and more underground space to accommodate environmental considerations and urban/suburban development, there will be an increasing requirement for diaphragm wall usage in even more difficult conditions. Of course diaphragm wall can also be used as deep groundwater barriers (Cut-Off-Walls). This market has shown that the demand for these types of walls is reaching more and more difficult soil conditions or required depths which are surpassing the current standard. The trench cutter is the most important tool for performing this work. The trench cutter itself is a reverse circulation excavation tool. It consists of a heavy steel frame with two drive gears attached to its bottom end, which rotates in opposite direction around horizontal axis. Cutter wheels are mounted onto the drive gears. As they rotate, the soil beneath the cutter is continuously being broken up, removed, mixed with the bentonite slurry in the trench and moved towards the opening of the pump suction box. The slurry loaded with soil and rock particles is pumped by a centrifugal pump which is located right above the cutter wheels, up through a hose system up to a desanding plant where the slurry is cleaned and returned into the trench."

Jan 1, 2015

By Steven D. Sandbrook

A man by the name of Louis Binstock once said, “Too often the shortcut, the line of least resistance, is responsible for evanescent and unsatisfactory success.”

Jan 1, 2015

"Gravity concentration remains the main separation method for fine iron ore and is used extensively for treating various minerals. Gravity concentration methods separate minerals of different specific gravity by their relative movement in response to gravity and one or more other forces, the latter often being the resistance to motion offered by a viscous fluid, such as water or air (Wills, 2006).Spirals concentrators are one of the gravity concentration equipment used for beneficiation of minerals. Spirals are typically used for processing of fine minerals (-1mm) size fraction. The main operating variables for a spiral concentrator are the feed rate, the solids concentration, the wash water addition and the position of the cutters or splitters used to separate the tailings, middling and concentrate streams (Sadeghi, Bazin & Renaud, 2014).The aim of this study is to investigate the effect of feed rate, solids concentration and wash water on grade and recovery on iron ore material. The Multotec SC20HC/7 WW spiral was used for the experimental test work. The spiral was tested at varying solids concentration and feed rate. The wash water rate was also varied to establish the best washing rate. The splitter positions were kept constant. Optimization of these variables is expected to provide optimum conditions for a good compromise between grade and recovery.INTRODUCTIONSpiral concentrators are simple low energy consuming devices that separate minerals mainly on the basis of density. Spirals are widely used in mineral processing as a method for preconcentration and have proven to be metallurgically efficient and cost effective.Spirals have a wide application, they are used in iron ore processing, coal, gold, chromites, mineral sands, glass sands, and in soil cleaning.Separation on a spiral is achieved through a combination of forces that act on particles as they move down the trough of the spiral. The main forces known to act on the particle on a spiral are the gravitational forces, centrifugal force, hydrodynamic drag, and lift and friction forces (Kapur & Meloy, 1998). Apart from the forces acting on a spiral, the properties of the slurry flowing on a spiral including, solids concentration, feed rate and wash water also plays an important role in the separation on the spiral.The relationship between separation efficiency and feed rate was shown to be linear, with a decrease in efficiency at higher flow rates. Previous work on flow profile by Holland - Batt (1990) indicated that any increase in the feed rate to a spiral results in a greater part of the additional flow volume reporting to the outside of the trough. The flow on the outside of the trough becomes energized and consequence to that the heavy particles find it hard to settle and escape this region to the inner region. This effect has a high impact on recovery of heavy minerals, since any increase in volumetric flow on the spiral is not made available for recovery in the inner region of the spiral."

Jan 1, 2015

By Michal Topolnicki

"Discussed is the use of wet Deep Soil Mixing, generally executed with single mixing tools 0.8 to 1.6m in diameter, employed in the foundation of viaduct supports. The applications involve economical patterns of ground improvement, covering in average about 40% of the foundation area or less, which contribute to the competitiveness of DSM solutions when compared to traditional piling. The focus is on selected aspects of the geotechnical design, applicable for geo-composite systems in which the interaction between the stabilised and the native soil should also be considered. Evaluation of settlement can be carried out with simplified methods, accounting for punching effects, or with more advanced FE models in case foundation tilt or differential settlements become important. Potential bending of DSM columns should be considered when evaluating column stresses, especially when dealing with deep deposits of soft soil and/or foundations loaded with overturning moments and/or high horizontal forces. Statistical evaluation of UCS data using lognormal distribution is recommended, and a new classification system for DSM application is proposed. Field investigations and monitoring data from completed projects are also presented.INTRODUCTIONThe first applications of wet Deep Soil Mixing in foundation of road viaducts constructed across and along the newly built A2-highway in Poland took place in 2002. Following detailed analyses, it was concluded that 39 viaducts, originally designed to rest upon large diameter piles in order to reduce excessive settlement of individual supports, could also be founded directly on the ground improved with DSM columns, fulfilling all relevant requirements of serviceability and ultimate limit states (SLS and ULS, respectively). It was also noticed that shorter construction times and lower costs of ground improvement with DSM contributed to substantial economical savings as compared to classical piling. Since then, more than 250 road and railway viaducts have been successfully founded on DSM treated ground in Poland, and wet soil mixing is now seen as a reliable and widely accepted technology for this purpose. These applications, together with a parallel use of wet DSM for foundation of buildings, industrial halls and wind turbines, have drawn international attention to the state of practice of wet DSM in Poland for foundation of engineering objects. What follows is an attempt to summarise experience gained during planning and execution of DSM works for foundation of the majority of road and railway viaducts constructed in the last 13 years, with emphasis on selected design aspects and evaluation of collected data and observed performance.The design process of DSM treatment is iterative, as described e.g. in Annex B of EN 14679, and typically involves two main steps, i.e., the selection of the design strength of cemented soil, called soil-mix design, and the adoption of suitable column pattern, referred to as geotechnical design. Soil-mix design was initially based on purposely arranged simple laboratory tests, involving mixing of soil specimen with different cement types and dosages and subsequent strength testing. However, with a growing number of completed projects the accumulated field strength data of different stabilised soils have been more and more frequently used, reducing the need for preceding laboratory testing of soil-mix to special projects only. Information on cement factors utilised in Poland and the range of recommended compressive strengths for different stabilised soils, as well as on mixing tools and characteristics of the wet method applied, can be found in Topolnicki (2008). Consequently, soil-mix design is not further discussed herein. Selected aspects of the geotechnical design are the main focus."

Jan 1, 2015

By Mike Fontaine

The success of a project is defined by meeting the financial performance objectives of the business case within a stipulated timeframe. Early in design, little information is normally available; the uncertainty introduces risk to the project outcome. Using a range of risk management tools and techniques, a project can be developed from front end loading phases 1 through 3 (FEL1–FEL3), and project implementation (FEL4) and then into operations with an optimized probability of success. For every project element, the risk management framework embodies: establishing a context; assessing risk (identify, analyze, and evaluate); and treating risk. Embedded within design activities, this process mitigates or eliminates risks. Monitoring and control, as well as extensive communication and consultation with stakeholders, is integral to the risk management process.

Jan 1, 2015

By M. Michael, A. Felber

"Mining activities, especially underground mining operations, create great demands on utilized haulage means which cover a variety of different horizontal and vertical distances. In the course of the continuous optimization of the haulage process, the application of textile machine elements, in particular synthetic fiber ropes, offers new opportunities. Therefore the current level of knowledge needs to be improved based on extensive analyses. For the estimation of the scope of these analyses, different fields of application and occurring environmental influences which have an impact on synthetic fiber ropes during their use in underground mining have to be evaluated. The Chair Underground Mining Methods of the TU Bergakademie Freiberg works on a scientific project concerning the use of synthetic fiber ropes in underground mining operations. This paper focuses on the potential application of synthetic fiber ropes in haulage systems in underground mining and exposes critical influences as an outcome of the working environment. These first investigations are the basis for the development of an appropriate experimental series. SYNTHETIC FIBER ROPES FOR UNDERGROUND MINING OPERATIONS The main idea is to optimize underground haulage means to develop even more economic systems. The new and lightweight design of single machine elements seems to be the first step to accomplish this goal. An example is the lightweight design of shaft hoisting ropes. The commonly used steel wire ropes are very heavy and are endangered to snap due to their own weight when reaching a distinguishing length. Thus they may not or only conditionally be used for deep mining operations utilizing shaft haulage. Ropes made of high-tech synthetic fibers weigh only an eighth of steel wire ropes while displaying the same tensile strength. This relation is shown in Figure 1, based on the comparison of fiber strength and density. This could offer new opportunities for deep mining operations, which are anticipated by many mining companies. /1/"

Jan 1, 2015

By S. Bentley

"Everyone has a general idea what mixing means, but describing the mixing process is not so simple. The objective of any mixing process is to distribute and blend the materials with different characteristics, different quantities as evenly as possible resulting in a homogenous mixture. Introducing proportional movement with the optimal intensity into the materials achieves effective homogeneous mixing results. A simple one directional movement with inadequate acceleration of the materials would obviously not achieve the same mixing results. This would be more like stirring than mixing. The amount of relative movement that is introduced is a decisive factor. Circumstances for successful mixing involve distribution of all materials, and achieving the highest probability that all recipe particles located in a specific position at the beginning can be found at any random location in the mixing chamber at the end of the process. This is the only way to ensure that a consistent result is achieved every time mixing is repeated.THREE-PART CYCLE The mixing cycle occurs in three phases; charging the mixer, the mixing process, and discharging. The sequence in which the individual materials to be mixed are filled into the mixer can have a huge impact on the efficiency of the mixing cycle. The mixing cycle overlaps the charging process and the discharge cycle follows the mixing cycle. To achieve optimum results, effective discharging methods should be taken into consideration to avoid risks of segregation. Costs for energy and wear should be as low as possible and finally, it is very important that the mixing cycle takes place as quickly as possible. In concrete or paste backfill production, selecting the best mixing technology is crucial for both the quality of the final product to be blended and the efficiency of the production process. The optimum mixing system is one that rapidly disperses all ingredients evenly throughout the mixing trough and completely surrounds all the course or fine aggregate particles with the slurry cement particles. Specific for paste production it’s the mixers job to also break-down unconditioned tailings to achieve consistent paste viscosity or measured spread. Many paste and concrete formulas also involve small quantities of chemical additives which also must be evenly distributed effectively. The time required per mixing cycle as well as the costs of energy, wear and maintenance will determine the economy of the concrete production."

Jan 1, 2015

By P. G. Martin

"As the speed of business has continued to increase over the last decade, the focus on real-time control of the performance of both stationary and mobile assets has become an increasing priority. Traditionally the maintenance team has been focused on the management of the availability of assets while the operations team has been focused on the throughput of those same assets. Typically operations and maintenance teams worked almost independently in spite of the fact that they were both working with the same assets. Part of the problem has been their traditional performance measures which have often been diametrically opposed. Recent advancements in the area of real-time performance measures and decision support have helped to drive higher levels of collaboration between operations and maintenance leading to real-time asset performance control and higher levels of business performance. This paper will explore the forces driving the need for changes, present an effective approach to the definition of the most appropriate business performance measures, and examine the effectiveness of contextualized real-time decision support resulting in asset performance control. TRADITIONAL APPROACHES TO ASSET PERFORMANCE MANAGEMENT In most industrial operations the phrase asset performance management is synonymous with maintenance of the industrial assets. This is the way industry has viewed asset management and asset performance management for decades. This is a very limited perspective that is serving to constrain the profitability of industrial operations. As industrial organizations began to form following the Industrial Revolution, the complexity of the operations forced an organizational design based on specialization. No single person could understand all of the aspects of an industrialized operation. This was particularly true at the plant floor level where the operation and maintenance of the industrial equipment required very different skillsets and training. To accommodate the vast differences most industrial organizations set up operations teams to run the equipment and maintenance teams to keep the equipment available to the operation. Both teams were dealing with the same industrial equipment but from very different perspectives and with very different performance measures. Typically the operations team was measured on maximizing the output of the equipment – or throughput. On the other hand the maintenance team was measured on the uptime – or availability of the equipment."

Jan 1, 2015

By Mark K. Larson, Douglas R. Tesarik, Heather E. Lawson

"Load transfer distance (LTD) is simple in concept and usually evident in underground coal mines. Many people in the mining industry recognize LTD as the distance from the panel to where the mine ribs and pillars show evidence of renewed spalling, floor heave, or other effects of increased weight due to longwall mining or pillaring. Barrier pillars, in particular, are designed to shield mains and other relatively permanent facilities from this loading. LTD is also important in determining the extent and degree to which mining increases the load on pillars and ribs in the gate roads. Generally, a long LTD reduces loads in gate roads, but may require larger barrier pillar widths to protect mains or adjacent panels from excessive loads. Therefore, a long LTD may make it easy or difficult to meet various objectives of mine layout design . LTD reflects overburden geology in two ways: First, overburden that is weak and readily caves will limit both the amount and distance of load transfer. Second, stronger, stiffer, sandier, and more massive overburden increases both the amount and distance of load transfer. As such, LTD is central to coal mine layout design and calibration of numerical models that seek to anticipate these transfers of load during mining. However, the term does not have a consistent definition in the literature, and various instruments and observational techniques with varying sensitivities and thresholds have been used to indicate the onset of mining-induced stress increase and, subsequently, to determine an LTD. Consistency is important for meaningful comparison of ground response between mining sites and for accurate calibration of models.This paper adds to the body of observed and reported LTDs by presenting cases with relatively sandy and massive overburden at two western coal mines. These two cases include observation and measurement of LTD with multiple methods and provide insight into how distances reported relative to different criteria and instrumentation could be adjusted for comparison against a common base. This base is the criteria used by Peng and Chiang (1984) to determine their empirical equation. In one of these two cases, LTD was recently measured at a western U.S. coal mine (Mine A) to be approximately four times that calculated using the Peng and Chiang empirical equation. LTD measurements were examined using various instruments at Mine A and at adjacent Mine B. The measurements at Mine B showed that LTD was significantly greater than that calculated by the Peng and Chiang equation. Difficulties with BPC installation and fittings at Mine B permitted only ranges of LTD to be determined from some BPCs. Even so, the LTDs and ranges of LTDs determined were consistent with the LTDs determined at Mine A."

Jan 1, 2015