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By Dennis R. Dolinar

Screen material in the form of welded wire mesh and geogrids are used in underground coal mines to prevent the fall of small pieces of rock from the roof between roof bolts. Further, if the screen is installed during the production cycle, roof fall injuries can be reduced significantly. Therefore, the National Institute for Occupational Safety and Health (NIOSH), because of the safety implications, conducted an evaluation of screen materials commonly used in U.S. coal mines to determine their support characteristics and identify the parameters that could affect their performance with respect to controlling the fall of rock from the roof surface. To evaluate the load and stiffness characteristics of the screen, a test frame was designed and installed in the Mine Roof Simulator (MRS) at the NIOSH Pittsburgh Research Laboratory (PRL). With this test set up, the screen is bolted at four corners of the frame and a center load is applied. The test set up allows for up to 20 in of screen deflection while the load and screen defection are continuously recorded. A series of tests were conducted to evaluate the effects of various parameters such as bolt tension, the type of load bearing surface and the size of bearing plates on welded screen performance. The most common screen material used in U. S. coal mines is an 8-gauge wire welded in a 4-by-4-in spacing or aperture. The peak screen load was normally limited by wire breakage. The conditions at the bearing plate influence the nature of the wire breakage. However, the screen stiffness was controlled by slippage at the bearing plates, and by weld and wire failure. The size of the bearing plate had a significant effect on the performance of the welded screen. Therefore, the design capacity of the 8-gauge screen is evaluated based on plate size. For a 6-by-6-in bearing plate the average peak load is 2,900 lb with a stiffness of 250 lb/in. For an 8-by-8-in bearing plate, the average peak load is 4,500 lb with a stiffness of 430 lb/in. These test results are based on a 4-by-4-ft bolt spacing. A geogrid mesh was also tested.

Jan 1, 2006

By Tom Shumka

"All mineral processing facilities that use girth gear driven mills need to inspect the gear teeth on a routine basis, whether it be every six months to every three years. The inspection frequency depends on gear tooth condition, and the objective is to ensure the operational integrity of the gear teeth. Conventional methods such as magnetic particle testing, visual inspection or dye penetrant examinations rely heavily on operator interpretation. At best, these techniques can determine whether a defect exists, but are unable to provide information on defect severity. This paper describes the use of combining combined eddy current array (eca) and alternating current field measurement (acfm) to provide a complete survey of all surface breaking indications on the whole gear tooth depth. This method accurately determines the size, length and depth of any cracks found on the surface.INTRODUCTION In order to gain a fundamental understanding of the evolving operational and production behavior of a piece of machinery over a specified time period as part of an effective condition monitoring program, a robust data collection process must be firmly established and adhered to. To be effectively implemented within an organization, a condition monitoring program must have support of not only the maintenance, production and engineering staffs, but also executive management support to ensure successful roll out to realize the maximum productivity of the machinery and subsequent cost-savings. One of the key elements of a mineral processing facility that use gear driven SAG Mills as a primary stage for grinding solution, is the integrity of the critical gear unit that drive the mill. For the maintenance team, condition monitoring on the gear unit is crucial for preventative maintenance. A catastrophic failure in the critical gear unit would require a minimum of ten days to replace the gear set, depending on the damage occurred. This, of course, would only be applicable if the client had a spare critical gear set in inventory. If a gear set had to be ordered, it could take from four months to two years to receive a new gear set. For example, in 2007, there was a global backlog of these types of gears sets resulting in a two year delivery. The maintenance costs associated with a catastrophic failure of this type would easily cost in the millions."

Jan 1, 2012

By Maya Kamenetsky, Khoi Nguyen, Natalee Bonnici, Steve Walters, Claire McMahon, Julie Hunt, Ron Berry

"The analysis of meso- and micro-scale textural attributes has been undertaken on ore samples from the Ernest Henry iron oxide-copper-gold (IOCG) deposit in NW QLD. Quantified textural data including grain size, shape and mineral association have been extracted from classified images of core with the aim to better predict potential mineral processing behaviours such as comminution, liberation and flotation. Data have been extracted from images of intact core at meso- and micro-scales using high resolution continuous images collected using automated core-logger technology, SEM-based and optical microscopy platforms.The results of this study will show examples of quantified size, shape and mineral association data from meso- and micro-scale classified images. Analysis of the data shows that there are domains of variable grain size and mineral association that can potentially be related to crushing and liberation behaviour. The trends that are observed at the drill-core (meso-) scale are consistent with those at the micro-scale. The results from the micro-scale analysis show that the domains defined at the core-scale have clearly different chalcopyrite sizes and shapes as well as variable bulk mineralogy.INTRODUCTIONInnovations in technology have allowed automated extraction of information about mineral shape, grain size and mineral association, i.e., texture, from meso- and micro-scale images of intact rocks. The overall aim of this research is to investigate trends in quantified textural data that can potentially give an early view of processing parameters such as predicted grind size and liberation behaviour."

Jan 1, 2009

By L. G. Marshall

This report is one of a series published by the Federal Bureau of Mines, describing mining methods and performance at individual mining operations throughout the United States. The objective of these papers is to promote development and conservation of our mineral resources by disseminating reliable technological information on mining methods, practices, and performance. Limestone deposits in Iowa are extensive and reserves are large. Most of the past production came from the eastern third of the state, although over half of the counties in the state have produced, or are now producing limestone. The stone is used as aggregate, road metal, agricultural lime, riprap, fluxing stone, railroad ballast, and in the manufacture of cement and lime.

Jan 1, 1962

By M Bourke

Modern computers and software provide powerful tools for the geologist to construct reliable models of geological resources, and the mining engineer to produce accurate and workable mine plans. Over the years many people have developed a phobia of computers, especially for geological analysis, modelling and mine planning. This phobia is often caused by a lack of knowledge, poor training or a bad experience. The adoption however of computers for geological modelling and mine planning is now becoming mainstream. With the correct training, a good understanding of input data, and detailed knowledge of the required results, the phobia can safely be overcome to provide mining operations with increased productivity.

Jan 1, 1999

By J. E. Crawshaw

"The few previous observations of the effect of turbulence on limits of inflammability have been made on a small scale in turbulence produced either by a fan or by movement of the mixture.By a suitable amount of turbulence from a fan the lower limit of methane was 5 per cent as compared with 5 per cent observed for quiescent mixtures in the same vessel.3 With a streaming movement of the gas mixture within the range of speed from 35 to 65 centimeters per second (69 to 128 feet a minute) the lower limit was approximately 5 percent,4 For a quiescent mixture of ethane the lower limit was 3.10 per cent ethane, but with fan running at a moderate speed a 3 per cent mixture exploded.5The object of the tests herein reported was (1) to determine the lower limit of natural gas in a mixture of natural gas and air Which would be ignited and propagate violently when the turbulence was produced by explosives fired from a cannon into the mixture; (2) to observe the behavior when the mixture contained less than this low limit; and (3) to determine how turbulence produced by a fan affects thin limit.Four series of tests were run, three of which were to determine the effect of different sources of ignition: Tests with (1) an electric igniter; (2) 3F black blasting powder stemmed with 2 pounds of dry fire clay stemming used to ignite the mixture, and (3) 40 per cent straight nitroglycerin dynamite unstemmed. The fourth was made to study the effect of turbulence produced by a two-speed electric fan, using an electric igniter as the source of ignition.In both series of tests with explosives, charges of 50 and 200 were used to determine the effect of increased quantity of explosives on the lower limit of natural gas."

Jul 1, 1930

By D. He

In China, the total reserves of vanadium, reported as V2O5, in stone coal is 118 Mt (130 million st). Recovering vanadium from such a large resource is very important to China?s vanadium industry. The technology now being used to recover vanadium from stone coal has the following two problems in the leaching process: a low recovery of vanadium and high acid consumption. To resolve these problems, a new leaching technology is proposed. The effects of factors such as H2SO4 concentration, liquid-solid ratio, temperature and time, and the types and additions of additives were studied. By adding 1.5% (by weight) CaF2 and leaching the roasted residue of stone coal with 5.4% (by weight) sulfuric acid at 90°C for 12 hours at a liquid-solid ratio of 2 mL/g, the leaching degree of vanadium reached 83.10%. This proposed leaching technology gives a feasible alternative for the processing of roasting residue of stone coal and can be applied in the comprehensive utilization of stone coal ores in China.

Jan 1, 2008

By D. Rendini, R. D. Gutridge

INTRODUCTION Gwinnett County, Georgia, is a part of the rapidly expanding metropolitan Atlanta Georgia area. Located approximately 48 km (30 miles) northeast of Atlanta, Gwinnett County has a current population in excess of 600,000 and is projected to reach a population of 1,200,000 by 2025. As a part of the County’s master plan to supply drinking water for the expanding population and to increase system reliability, the Gwinnett County Public Utilities Department undertook the Shoal Creek Raw Water Intake and Pump Station Project. Figure 1 shows a vicinity map for the project. Prior to construction of the Shoal Creek Raw Water Intake and Pump Station Project the County had a single raw water intake to feed water from Lake Sidney Lanier (Lake Lanier) into a filter plant for processing into potable water. This project together with a newly constructed water filter plant provides Gwinnett County additional capacity and system redundancy to prevent interruptions to the drinking water supply. Lake Lanier is a man made reservoir with over 800 km (500 miles) of shoreline and was constructed by the Army Corps of Engineers in the 1950s for hydro electric power generation, flood control, and navigation benefits for the Chattahoochee River. Over time, Lake Lanier has become an increasingly important source of drinking water for the metropolitan Atlanta area. This paper focuses on the primary underground construction and lake tap components of the project including a 42.7 m (140 ft) deep pump station shaft 24.4 m(80 ft) in finished diameter transitioning to a 6.1 m (20 ft) finished diameter shaft, a3.05 m (10 ft) finished diameter by 19.8 m (65 ft) deep intake shaft constructed in an average of 21.3 m (70 ft) of water, and a 190.5 m (625 ft) by 3.05 m (10 ft) finished diameter modified horseshoe tunnel connecting the two shafts. This raw water intake system, in conjunction with the incorporated pump station with 8 pumps and dual1,829 mm (72 inch) pipelines, provides a system capacity of 1,091,062 m3/day(240 MGD) to two water filter plants and is expandable by the addition of pumps to1,500,210 m3/day (330 MGD). Parsons provided design and construction management services for the project. The $29.6 million contract to construct the project was awarded to W.L. Hailey &Company. Notice to proceed was given August 6, 2001 and substantial completion was achieved on January 20, 2004. Value engineering changes adopted for the project contributed to completing the project at a final cost of $28.8 million.

Jan 1, 2005

By H. J. de Haan, L. Schenk

Scope for Thermal Recovery in Shell's Heavy Oil Fields in Venezuela The main heavy oil reservoirs on the East coast of Lake Maracaibo (Fig. I), known as "Bolivar Coast", initially contained some 20 billion bbl of oil in place with gravities in the range of 10 to 15° API. The current total production rate is about 400,000 B/D. Since the recovery to date is on an average only 12.5 percent of the initial oil in place, these fields offer a vast potential for secondary recovery methods. The reservoirs are characterized by moderate depth (generally 1,000 to 3,000 ft; maximum 5,000 ft), good formation properties such as net oil sand thickness (50 to 300 ft), high porosity (30 to 40 percent) permeability (1 to 3 darcies) and oil saturation (initially about 80 percent) and high oil viscosity (100 to 10,000 cp in situ), all of which are favorable for the application of thermal recovery processes. Since 1957, steam drive, steam "soak" and underground combustion have been tested or are being tested in this area.1-3 This paper deals with a major steam drive test in the Tia Juana field. The test was commenced in Sept., 1961, on the basis of encouraging results of laboratory experiments and pilot field tests, which will be discussed briefly. Early Laboratory Investigation of the Steam Drive Process In 1956 a series of model experiments was carried out in the Koninklijke/Shell Laboratorium, Amster- dam, to investigate the displacement of heavy oil by steam.' The prototype studied was a horizontal, un-consolidated heavy oil reservoir, subjected to a linear steam drive. The model, representing a slab from this reservoir along the main flow direction, consisted of a steel tube filled with oil-saturated sand, provided with layers of rock at the top and bottom to simulate conductive heat losses to cap and base rock. Lateral heat losses, perpendicular to the main flow direction, were minimized by insulating the sides of the model. Heat flow and viscosity and gravity forces were scaled by taking the steam injection rate and sand permeability inversely proportional to the geometric reduction factor of the model, and using materials (oil, steam, cap rock, etc.) identical with those of the prototype. The main feature of the process was a frontal displacement mechanism that was observed within wide ranges of injection pressure and rate, oil viscosity, initial oil saturation and sand permeability. The high stability of this front can be attributed to the high volumetric steam flow rates, combined with the reduction in oil viscosity. High recoveries were obtained due to the low residual oil saturation of about 15 percent in the zone swept by steam. The latter value pertains to the specific test conditions (heavy oil, uncon-solidated sand) and may be lower for light oil, due to the effects of steam distillation. The applicability of this experimental approach is limited, as it does not take into account the fact that

Jan 1, 1970

"Each and every flotation plant must produce daily/weekly/monthly production reports in which metal balances for payable and penalising elements are presented. Several factors including ore heterogeneity and harsh production environment affect the reproducibility of the reported data. Best practices of metal accounting thus prescribe that production reports be accompanied by measurement quality reports quantifying the reproducibility (a data quality metric often expressed as a relative standard deviation) of each data reported. Ignoring the irreproducibility of measurements may lead to the perception that random errors have been totally eliminated through statistical data reconciliation, which is wrong. This paper aims at explaining the full lifecycle management of reproducibility estimation from the outset at the measurement process to its reporting after having been through the statistical data reconciliation process. Indeed, the reproducibility of reported data can be obtained by performing a sensitivity analysis. Necessary conditions for obtaining a truly representative assessment of measurement reproducibility are stated. Typical levels of measurement reproducibility found in operating flotation plants are also reported. These numbers can be used as benchmarks for reproducibility levels that can be realistically expected.IntroductionEach and every flotation plant must produce daily/weekly/monthly production reports in which metal balances for payable and penalising elements are presented. Such production reports are the most expected output from a metal accounting system (MAS). The duly recurrence of this task combined with an insufficient level of automation has somehow contributed to the misleading perception that it is mainly a clerical work. However, as shown in Figure 1, a MAS encompasses way more than just a reporting system. Acknowledging that the content of production reports indubitably origin from raw measurements has important implications for how both the reports and MAS should be monitored."

Jan 1, 2016

By C. E. Wood

[Because of the renewed i~,ortanc of the strate ic netal ~ngane8e the Bureau of Mines is conductin further ro~aarch on pyrometallurgica1 ~ethods of boneficiating 0 ngani.foro'l iron ores nnn lo\,f-~~r de oanganesc ores. Published data on .the l2~roI'let llurgica.l treatnent of tl::1.nganse8 ores have been revi .. \-'en by Jose-ph ? .2]

Jan 1, 1940

The GPS and information technology industries are now applying considerable development effort to what is being termed machine control and machine information systems, in particular focusing on the industries the of mining construction and agriculture. GPS based systems are demonstrably finding common acceptance and adding commercial value to many machine applications in industry. This has been the first step in the evolution of the information age that is now reforming mining practices. Adding the technologies of wireless data communication, modem computer databases, and networked PC's mining is on the verge of a new era in overall process management. This paper is a general discussion of what the information age means to miners and a general description of new mining operation technologies available to day from the Caterpillar technology alliance.

Jan 1, 1999

By J. C. Poulos

The West Elk Mine is located near Somerset, Colorado approximately 70 miles southeast of Grand Junction, Colorado and 72 miles southwest of Glenwood Springs, Colorado on state highway 133 (Figure 1). The West Elk Mine was opened January 20, 1982 as the Mount Gunnison #1 Mine operated by the West Elk Coal Company, a division of ARCO Coal. In the early 1990?s ARCO changed the mine name to West Elk Mine and the operating company was renamed Mountain Coal Company. Arch Coal, Inc. purchased the West Elk Mine in 1998. West Elk Mine has produced coal from three different seams. Coal was first mined from the F Seam, the upper most seam in the stratigraphic sequence, from 1982 through 1991. Coal was produced from the B Seam, the lower most seam, starting with continuous miners in 1991 and transitioning to longwall mining in 1992and continued on through October 2008. The development of the E Seam, which is the middle seam in the stratigraphic column, started in 2004 with longwall production commencing in 2008. The ventilation conversion from exhausting to forcing for the E Seam portion of the West Elk Mine was implemented in late October 2009.

Feb 27, 2013

By Robert J. Dompe

The objective of this program was to develop a cost effective microprocessor-based electronic image sensor system for monitoring pit slope displacement to detect and/ or predict impending slope failure in surface mines. A background study and data analysis yielded a performance specification for candidate Video Slope Monitoring Systems. A design concept was developed based on using a pair of solid state video cameras located on precision pointing assemblies. The digital images from the cameras are compared and, using electronic triangulation, slope topology is calculated. The current and past locations of operator selected features are compared to determine pit slope displacement. A proof-of-concept test was performed using a laboratory model of a pit slope. Based on the successful results of that testing it is recommended that an in-mine evaluation be performed using a full-scale prototype Video Slope Monitoring System.

Jan 1, 1982

By M. Faraji

Inclusions formed in a high-carbon, manganese-silicon killed plain steel (Fe-0.77C wt%) were studied. Various techniques were used to characterise the inclusions, and the latter were classified according to their chemical composition, size and morphology. The main constituent elements entering the inclusions were Mn, S, Al, and oxygen. Alongside MnS and some Al2O3 inclusions many non-metallic inclusions appeared in complex forms, consisting of silicates, sulphides and oxides. Duplex oxy-sulphides, mainly MnS combined with Al2O3, or SiO2 were the most common complex multiphase inclusions in this steel. The nanoindentation technique was used to assess and rate different types of inclusions and data of the hardness and elastic modulus of individual inclusions at room temperature are presented.

Jan 1, 2010

By F. Ford, J. Dong

"Laboratory and miniplant testwork was carried out to reject uranium from an Iron Oxide Copper Gold (IOCG) deposit that contains an average of 60-70 ppm uranium with high variability. The dominate copper bearing mineral is chalcopyrite with minor bornite and trace covellite. The main gangue minerals are iron-rich chlorite, quartz and magnetite. The main uranium-containing mineral is uraninite (UO2). Downstream processes require the maximum uranium level of no more than 80 ppm in final copper concentrate.Mineralogical examination reveals that uraninite particles are finely disseminated with grain size of less than a few microns in the deposit requiring fine regrind in order to liberate uraninite from chalcopyrite particles. A lab flowsheet was developed to include ultrafine regrind of the rougher concentrate to the particle size of 80% passing 11-13 µm with up to four stages of recleaning in flotation columns. Finer regrind to 80% passing 5-6 µm may continue to improve liberation but does not decrease uranium level in the final concentrate. In each of the successive recleaning stages by flotation column after fine regrind, uraninite is rejected into the column tailings, with the final copper gold concentrate containing less than 70 ppm uranium from a feed containing 83 ppm uranium. The conceptual flowsheet was further tested in an integrated, continuous miniplant showing average 94% copper recovery with average 74 ppm uranium. The uraninite particles that report to the final concentrate are either locked with chalcopyrite or entrained as liberated particles of less than 5 µm in size.IntroductionIron Oxide Copper Gold (IOCG) deposits are copper and gold ores hosted within a large body of iron oxide and are significant ore deposits for copper and gold (Williams, et al., 2005). These deposits can also contain economic levels of other metals such as uranium and rare earth elements. The known sizes of IOCG deposits range from 10 to 4,000 million tonnes with grade of 0.2-5% copper and 0.1-3 g/t gold. One of the greatest IOCG deposits is Olympic Dam in South Australia. It is the fourth largest copper deposit and the largest uranium deposit in the world. Gold and silver in the deposit also contribute significantly to the total revenue."

Jan 1, 2017

By G. C. Lammers

The object of this study was to determine the economic feasibility of hydraulically transporting Sandow (Tex.) lignite 100 miles and dewatering and thermally drying the transported lignite to a surface-dry condition. The most important factors involved in the feasibility of hydraulic transport, are the degradation incurred during transit, the length of the line, and the cost of alternative methods of shipment. In pipeline tests in which roughly 75 miles of hydraulic transport was simulated the percentage of minus-325-mesh solids increased from about 1 to 41 percent for both lignite and bituminous coal; in the micron sizes the coal fared considerably better than the lignite. Such degradation, even though it enhances flow through the pipe-line, severely aggravates the dewatering problem on lignite. Cost studies indicated that continuous vacuum filters offer the most economical means of dewatering minus-1/8-inch material. Surface moisture, if high, must be removed by relatively expensive thermal drying.

Jan 1, 1958

Water represents 80?85% of the volume of mineral pulp processed in flotation circuits. Imperatives for a more detailed focus on circuit water quality and its control have come from increasing requirements to use relatively impure primary water supplies (e.g. high salinity, treated sewage) and high proportions of recycle from tailings dams, thickener overflows, dewatered and filter products. An integrated methodology for examining process water quality and its effect on minerals separation has been developed coupled with minerals surface chemistry across the complete processing circuit. Unrecognised factors, including varying proportions of water streams (daily or hourly), colloidal precipitation, highly variable pH and Eh, reaction and dissolution of minerals, minerals surface layer coatings, residual reagents and their reaction products, and microbiological activity have been studied in eight mineral processing circuits. The methodology combines: solution survey and modelling; microbiological surveys; minerals surface analysis and modelling; and process response. It has been possible to match the predicted (model) pulp chemistry with that measured from surveys of the solution and mineral surfaces. Treatment methods have included: monitored and balanced stream combinations; organic species removal; flocculation and aggregation; induced precipitation; dissolved air flotation; ageing (oxidation, UV exposure); and chemical surface conditioning of minerals. Some specific achievements from the methodology applied in plant and laboratory testing, with examples from case studies, will be described.

Jan 1, 2001

By John E. Leitch

The cost of corrosion as measured by such cost components as the renovation or replacement of coated steel, or the use of expensive coating systems on steel, is considerable. Extrapolating from figures for the USA would place the overall cost of corrosion for South Africa as a figure of the order of magnitude of something over 1% of the GNP. This is a sizeable amount, of which costs associated with atmospheric corrosion would be a significant proportion. The corrosivity of an atmosphere can be defined as the ability of the atmosphere to cause corrosion in a given metal or alloy (International Standards Organization [1]). The ISO Standard 9223 specifies the key factors in the atmospheric corrosion of metals and alloys, and defines categories of corrosivity on the basis of these factors. Prior to the publication of that ISO standard, Callaghan published the results of his twenty-year exposure programme and his excellent corrosivity map of Southern Africa [2]. The present author published updates of the corrosivity map in 1999 [3] and again in 2003 [4]. The summary of the individual areas of corrosivity around Southern Africa was published in the latter paper, and is reproduced here as the following TABLE 1. Of significance in TABLE 1 are the numerous regions of very high corrosivity (C5 or beyond), particularly the rural West Coast shoreline, the North East Coast (KZN) shoreline, and the coastal cities Cape Town, Durban and Richards Bay. The corrosivity map as published is obviously based on much extrapolation as only a small number of points have been measured. During the past three years further measurements have been made, mostly however at the same sites in order to give greater reliability and to monitor long-term trends with changes in pollution. These two aspects are incorporated in this update. There has become available a greater amount of air pollution data for centres in South Africa than was the case some years ago. In this present paper the pollution data are used to extrapolate the corrosivity over areas where little or no direct corrosivity measurement has been made. This methodology is described in ISO 9223.

Jan 1, 2006

By M. Karimi

Artificial neural networks (ANNs) have found their applications in the modelling of unit operations of mineral processing plants. In this research, laboratory-scale tests were conducted, using a three-inch diameter Mozley hydrocyclone. Main parameters included pressure drop at inlet, solid per cent, vortex and apex diameter were adjusted. The corrected cut size (d50c) and the flow rates of underflow and overflow were determined. Multi layers perceptron (MLP) feed forward network architectures were designed to predict the responses. The results showed a good correlation between experimental and network output, for corrected cut size and flow rates. Keywords: hydrocyclone, artificial neural network, corrected cut size, flow rates.

Jan 1, 2010