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By N Weerasekara, M Powell, P Toor

The effect of liner wear on SAG mill performance has gained much attention in recent years. It is commonly observed that the three key performance criteria of SAG milling; throughput, power and product size all improve as the liner wears.The increase in throughput is generally ascribed to the increase in the grate apertures and the increase in mill volume due to the wear of these components. Whilst the decrease in product size is attributed to the reduction in lifter height and angle, resulting in more breakage by means of attrition and abrasion.Though it is widely acknowledged that the wearing of liner components such as Lifters, Plates and Grates have a significant impact on mill performance, their individual contribution to changes in mill performance has been unclear, and resultantly lead to questions like; what percentage of the throughput increase can be attributed to the increase in mill volume (plate wear)? and how much can be attributed to the increase in grate aperture (grate wear)?It has been found that through the use of grinding surveys, analysis of production data and JKSimMet it was possible to separate the effects of changing liner profile, increasing mill diameter and increasing grate aperture on the mill performance allowing for the quantification of each.The outlined methodology allows for both troubleshooting of problem liner components which reduce milling efficiency in their wear life as well as providing a basis for a more quantitative approach to liner design and reline scheduling.CITATION:Toor, P, Powell, M, Hilden, M and Weerasekara, N, 2015. Understanding the effects of liner wear on semi-autogenous grinding mill performance, in Proceedings MetPlant 2015, pp 150–161 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

By B. M. McKay

The Walnut Creek Mine was developed in 1989 to supply lignite to the Texas-New Mexico Power TNP-ONE power plant. Being new, we had the opportunity to start from scratch and rethink many of the traditional methods of managing a mine operation. We had the opportunity to create a team environment, encouraging people to get involved and make decisions. The founding philosophy of the mine, "A Quality Product by Quality People", acknowledged that the key to a productive, quality operation was the people. This paper will explore methods employed by Walnut Creek in selection of team members, building the team and the relative success of these methods.

Jan 1, 1993

By M. C. Bleiweiss

Various light sources were evaluated for use in a fiber optic lighting system for mining machines. It was determined that a metal halide arc lamp was best because of its resistance to damage from shock and vibration and the high luminance of the arc. Measurements were made of the percent transmission of the ½ inch thick glass window and the fiber bundles, the total lumen output of the diffuser assembly with a known input and of the average surface luminance of the diffuser assembly. These data were then used to calculate the theoretical output of the system given an estimated input from the source. A prototype 55 watt, single-ended metal halide source was then developed. In order to provide greater efficacy and higher throughput through the fiber optic cables, a variation of the lamp with thallium iodide added to the fill was developed. The lamp was modified and a ballast was developed to allow it to hot restrike.

Jan 1, 1986

By J T. Woodcock, G J. Sparrow

A sample of pyrrhotite flotation concentrate pulp assaying 15.3 g/t Au, which had been prepared from an old tailing dump, was treated to extract the gold. Examination of the concentrate with an SEM showed that exposed or free native gold, 5- 40 ¦m in diameter, was present but no locked gold was observed. Direct cyanidation of the concentrate to extract the gold showed that the flotation reagents present inhibited gold extraction. A range of pre-treatments was used to overcome these effects. Direct cyanidation for 48 h extracted only 26 per cent of the gold, indicating possible contamination of the gold in the concentrate with flotation reagents. Pre-treatment of the concentrate pulp by aeration for 24 h, or by 72 h aeration with an addition of 3.65 kg/t of sodium sulphite, gave little improvement in gold extraction by subsequent cyanidation. Pre-treatment by filtration, or by aeration with 12.5 L/t 100 volume hydrogen peroxide, followed by cyanidation for 48 h gave gold extractions in the range 67-77 per cent. Combining filtration and an aeration period with hydrogen peroxide addition raised the subsequent cyanidation extraction of gold to 88 per cent, giving a tailing assaying 1.5 g/t Au. Re-cyanidation of some of the dried tailings from the initial tests extracted most of the remaining gold giving a tailing assaying 0.5 g/t Au. This indicated that most of the gold was available for dissolution by cyanide. The poor dissolution of gold by cyanidation of the untreated concentrate was attributed to the presence of flotation reagents. It was shown by UV spectrometry that xanthate-containing compounds were present in the solids fraction of the original pulp and that they were partly removed by pre-treatment. MIBC was also present, and dithiophosphate, which was used in the flotation step, was also probably present. The results indicated that the improvement in gold extraction after filtration and oxidation of the original pulp was due to partial removal of the flotation reagents, and illustrates the detrimental effects that residual flotation reagents can have on the extraction of gold by cyanidation of a flotation concentration.

Jan 1, 1990

By W. F. M. GOSS

For the purpose of procuring data that could be used in estimating the value of the briquetting process as applied to American fuels, the United States Geological Survey, in cooperation with other interests, began in 1904, at the Louisiana Purchase Exposition, certain experiments involving the production and use of bituminous-coal briquets. It installed at St. Louis, and later at Norfolk, machines for the manufacture of such briquets, and the output of these machines has been tested in locomotive service on several different railroads in comparison with natural fuels. An elaborate and carefully executed series of tests involving the use of natural coals and of briquets made from the same coal, previously crushed, was carried out on a locomotive mounted at the testing plant of the Pennsylvania Railroad Company at Altoona, Pa.; and some preliminary experiments involving the use of briquets in marine service were made in connection with one of the Government's torpedo boats. A description of these tests is presented herewith. The results sustain the following general conelusions: 1. The briquets made on the Government's machines have well withstood exposure to the weather. and have suffered but little deterioration from handling. 2. In all classes of service involved by the experiments, the use of briquets in the place of natural coal appears to have increased the evaporative efficiency of the boilers tested. 3. The smoke produced has in no test been more dense with the briquets than with coal; on the contrary, in most tests the smoke density is said to have been less when briquets were used. 4. The use of briquets increases the facility with which an even fire over the whole area of the grate may be maintained.

Jan 1, 1911

By Steve Colburn

The CRITERION Survey Systems utilize both theodolite mounted and hand held reflectorless distance meters. These are eye safe, easy-to-use, and specifically designed to endure the harsh environments characteristic to the mining, quarry and explosives industries. Survey data collected by the systems is digitally stored in a ruggedized data collector and then processed with a specialized, Windows-based, interactive software program which can be run on any standard PC.

Jan 1, 1997

By Susan M. Moore

Many challenges are faced by workers in lower-seam (42 inches or less) mines. The lower-seam heights confine mine workers to their knees as they perform their daily tasks such as installing roof bolts, delivering supplies, repairing belt, or cutting coal. Miners working in these lower seams often consider kneepads to be their only line of defense against knee injuries. However, healthy knees do not start and stop with kneepads. Other interventions such as changing postures, proper hygiene, and work station design may also be used to reduce mine workers? risks for developing knee injuries. Incorporating these and many other interventions into a mine worker?s ?way of life? is an important step to ensuring a long, healthy career and retirement. Keeping knees healthy is also a key aspect to reducing costs in low-seam mines as the industry battles rising health care costs, and training/recruitment of replacement workers is time-consuming and costly. Educating the workforce about the possible interventions to reduce knee injury risk is a primary objective for the National Institute for Occupational Safety and Health?s (NIOSH) Pittsburgh Research Laboratory (PRL). Therefore, NIOSH researchers, along with industry and academia, developed a training package to educate the mining community about some possible interventions beyond kneepads that may be used to help decrease knee injury rates. Increased awareness and simple changes are the first steps to reducing knee injuries.

May 1, 2008

Mineral deposits in New Zealand whose origin can be ascribed to primary magmatic segregations are associated with mafic-ultramafic complexes related to two orogenic episodes which took place during Palaeozoic and Mesozoic times. These mafic-ultramafic complexes are essentially of two types. One is ophiolitic and has podiform chromite mineralisation presumably formed below a spreading ridge. The other type occurs as intraplate layered intrusions in which Fe-Cu-Ni sulphides and Fe-Ti-V oxides have formed as a result of liquid immiscibility with the host magma, and have subsequently accumulated by gravity means. Generalised descriptions are given for some deposits in NW Nelson, Fiordland and Marlborough districts.

Jan 1, 1980

By E. E. De Beer

This paper describes a method for the determination of the settlement of an individual H-bearing pile, based on the results of CPT-tests. As implied by the nature of the problem, no analysis performed on one pile can be regarded as generally valid for a whole piling foundation project because, even on one site, the pile behaviour varies from one pile to another. Consequently, no precise mathematical analysis has been established; the proposed procedure represents a simple model for the determination of the probable settlement behaviour of an H-pile under a compressive load. Prior to the settlement computations, the rupture load and the resistance distribution along the pile have to be determined. Since the method for the determination of the H-pile bearing capacity from the results of CPT tests has been described elsewhere (de Beer, 1971, 72; de Beer et al., 1982; Arbed, 1985), no details will be given in this paper. The proposed method is valid for both uniform and non-uniform H-piles. The computed results have been satisfactorely compared to the static loading tests performed on different types of piles in clayey and sandy soils during an ECSC research program on H-bearing piles (1983-1987).

Jan 1, 1987

By François G. Bernardeau

Cement-bentonite (C-B) slurry walls have been used for ground water cutoff in deep excavations, contamination containment, and other applications. Hydraulic conductivity is of great concern for cement-bentonite slurry walls. The quality control program usually specifies permeability and strength tests to be performed in a laboratory on samples cast in the field and cured for a certain time. Currently there is no widely accepted in-situ test method for the performance of the constructed slurry wall. A recently constructed cement-bentonite slurry wall in South Carolina included a 200-foot-long test section done in advance of the production of an 8,300 foot-long wall. Intensive tests and investigation were conducted during and after the test section construction: Monitoring piezometers were installed using wet insertion method and packer tests were conducted in boreholes drilled in the post-28-day-cure slurry wall. The permeability measured from the packer tests was about two orders of magnitude higher than the design and the laboratory test values. Additional investigation was performed using a video camera to inspect the borehole walls especially the packer test sections. Test pits were excavated to observe both sides of the cement-bentonite slurry wall. A thorough inspection was conducted to evaluate the integrity of the wall. The lessons learned and issues regarding the disturbance effects of in-situ testing of cement bentonite slurry walls is presented and discussed.

Jan 1, 2008

By Antonio Lourenço Batista de Souza

A simulação da evolução microestrutural, durante a etapa de acabamento, na laminação de tiras a quente de aços carbono, através do software DEFORMTM3D, foi estudada para prever a carga de laminação, distribuição de temperatura, de deformação e de tamanho de grão. A boa concordância dos valores da carga e temperatura na simulação com os valores da literatura, mostra que o presente modelo é viável para representar o processo de laminação. A deformação acumulada próximo à superfície foi maior quando comparada a da região central da tira laminada, indicando uma distribuição heterogênea da deformação, que diminui com a evolução do processo. O aumento da fração de recristalização dinâmica (DRX) e a diminuição do tamanho de grão foram mais significativos nos primeiros passes. Além disso, houve uma fração de DRX maior e um tamanho de grão menor próximo a superfície da tira, esta diferença no tamanho de grão, no sentido da espessura, também diminuiu com a evolução do processo. Estes resultados sugerem que múltiplos passes podem diminuir a não homogeneidade microestrutural da tira. Assim, este estudo mostra a eficácia do modelo microestrutural em predizer o comportamento do material em um processo de laminação a quente.

Jul 30, 2018

By Stephen C. Tadolini, Thomas M. Barczak

A critical safety component for all underground mining is intrinsic and standing support systems. Specifically, tabular hardrock mining exploits a wide variety of deposits that require various methodologies to safely mine the ore material. Several new support systems have been developed in recent years for hard rock applications which have been modified or applied in a variety of ground control applications. These include prestressing devices, improved cribs, and free standing supports. Various standing support and prop-type systems have been designed for hardrock applications with seismic loading conditions to accept prestressing. The prestressing, using water-filled cells, creates an active load upon installation and is considered essential to maintain support during and after the blasting of the mine faces. Heavy seismic activity is also present in these mines and the prestressing units can provide some energy absorption capability to help preserve the integrity of the support. This paper presents an overview of these innovations in support technology.

By Victor E. Kral

"SUMMARYA preliminary examination of the Buena Vista iron deposit was made in June 1942 by Paul E. Pesonen, mining engineer of the Bureau of Mines. Subsequent examinations were made by D. W. Butner, of the Bureau, in March 1943, and by the author in July 1944, who recommended exploration by diamond drilling, trenching, and sampling. Work on the project was done during the period March 28 to May 26, 1945.Property holdings, comprising 16 claims known as the Buena Vista group, are situated in sec. 4, T. 24 N., R. 34 E., Mount Diablo base and meridian, north Churchill County, about 37 miles east of Lovelock, Nev.Three diamond-drill holes totaling 575 feet were drilled; 45 small pits and ten trenches, totaling 435 linear feet, were excavated, and 84 channel samples totaling 862 feet were obtained under supervision of the Bureau.Purpose of the project was to determine the possible downward extension of the mineralized sections exposed in the outcrops and to determine grade of the ore.Bureau work was confined to one claim only - the Iron Mountain."

Jun 1, 1947

By Lays Augusta Leal Carvalho, Alex Milton Albergaria Campos, Paulo Santos Assis

A presente pesquisa dedica-se a analisar a adição de biomassa de serragem, que é uma matéria-prima carbonosa que pode ser utilizada nas misturas de carvão para produção do coque metalúrgico, preservando a qualidade exigida, com menor custo. A qualidade do coque metalúrgico pode ser determinada por meio da efetividade das suas funções químicas, físicas e térmicas no interior do alto-forno. Para produção de ferro gusa, qualquer modificação nos constituintes das matérias-primas pode ter influência direta na produtividade do alto-forno e na qualidade final do aço. A partir das análises de degradação térmica como reatividade do coque (CRI) e resistência do coque após reação (CSR), resistência a frio (DI) e análises imediatas, pode-se definir a qualidade do coque metalúrgico produzido com serragem. Assim sendo, o objetivo é relacionar estes parâmetros com as particularidades do material e suas funções no alto-forno. Os resultados mostram que tecnicamente é viável a utilização de até 2% de serragem de eucalipto na mistura de carvões.

Oct 1, 2019

By Milton B. Hall

This report discusses in detail laboratory and pilot-plant tests conducted from January 1951 until January 1955 at the Northwest Electrodevelopment Experiment Station of the Bureau of Mines, Albany, Oreg., on defluorination and recovery of evolved fluorine from phosphate rock. Results of use tests of defluorinated phosphate rock by cooperating agricultural colleges and the United States Department of Agriculture are also included. In 1954 the consumption of fluorspar, the only domestic fluorine-bearing mineral of commercial importance, was approximately 478,000 short tons; 245,000 tons was from domestic mines. The production of marketable phosphate rock in the same period was about 13,800,000 long tons. Of this total amount, approximately 15 percent was produced in the West. From the viewpoint of conservation and utilization of fluorine as a natural resource, it is interesting to note that the total estimated quantity of fluorine in domestically produced phosphate rock is more than double that present in domestically mined fluorspar.

Jan 1, 1958

By Ta M. Li, Russell A. Carter

The first century of mining in northern Idaho's Couer d'Alene District will soon he drawing to a close. Like so many other great raining districts, it has been a period accompanied by a rich and colorful history. From its early days as a gold rush camp, the district has evolved into the leading silver producer in the US, but the going has not been easy: early-day labor disputes, the challenge of mining for profit in some of the deepest mines in the Western hemisphere, and the constant search for new reserves at great depths have taken their toll of mines-and miners-along the way. To these traditional mining problems have of late been added the burden of inflationary cost increases, pollution control, and reclamation. A recent visit to the district by MINING ENGINEERING, how ever, revealed that the deep commitment of the operating companies and the quiet competence and vitality of their engineering personnel are key factors in the continued prosperity of the district.

Jan 7, 1976

By W. W. Adams

[Sales of explosives - permissible explosives5/ other high explosives, and black blasting powder - in the United States during the calendar year 1937 reached a combined total that slightly exceeded the quantity sold in 1936. A larger output was reported for permissible and other high explosives but a smaller for black powder. Production of the three classes of explosives totaled 404,744,294 pounds, more than 3 percent over 1336. The total quantity produced included 49,579,441 pounds of permissible, 288,924,253 pounds of other high ex- plosives, 36,403,950 pounds of black powder in pellet form, and 23,836,550 pounds of black powder in granular form. Sales of granular black powder declined 26 percent compared with 1936 and of pellet black powder 12 percent; gales of permissible explosives increased nearly 4 percent and of other high explosives 10 percent]

Jan 1, 1938

By Artur Fernando de Vito Júnior

Caracterizar propriedades de resistência à propagação de trinca em aços é um elemento central em métodos de avaliação de integridade estrutural. Tal caracterização, normalmente se dá por meio da obtenção de curvas de resistência à propagação estável de defeitos (curvas J-R) do material. Sendo assim, para tornar este estudo mais amplo, serão obtidas curvas J-R de um aço estrutural com o objetivo de elaborar um roteiro metodológico para obtenção de curvas J-R. O ensaio de tenacidade à fratura para obtenção da curva J-R foi conduzido utilizando a técnica do corpo de prova único (single specimen) empregando o método da flexibilidade no descarregamento (unloading compliance), segundo a norma de ensaios ASTM E1820. Para este estudo, foram utilizados corpos de prova compactos C(T) de espessura B=10,0 mm, largura W=2B e uma relação aproximada entre o tamanho de trinca (a) e a largura, a/W=0,5.

Aug 8, 2018

By R. Shields

"Hard rock mines move large volumes of material, which can cause the conveyors that are essential to this movement to suffer lots of problems, including carryback, spillage, dust and belt wander. Many of these issues are created at the transfer points where the belts are loaded.This article provides an overview of the latest transfer point systems that incorporate safety and serviceability by design as well as a report on recent projects. One project is the Conveyor B Transfer at the Coeur Rochester silver mine near Lovelock, NV. Here, performance was improved with the installation of belt support cradles, engineered chute walls with external wear liner, and a compact dust collector. A second project is the improvement of belt support idlers and skirtboard sealing in a long loading zone of a conveyor under the concentrator at an Arizona copper mine.The importance of transfer pointsConveyors are essential in mine material handling. Their performance will often make the difference in mine productivity and profitability. A key to conveyor performance is the transfer points where the conveyor belt is loaded and discharges. At these transfer points, many of the problems encountered with the conveyor system are created.The problems that arise at the transfer stations include off-center and segregated loading, mistracking, blockages and plugging. And there are a variety of problems originating with fugitive material — cargo released in the form of carryback, spillage or airborne dust — that are created or exacerbated in the transfer points. These fugitive materials turn into other conveyor-related problems, including shortened component life, unplanned outages for conveyor maintenance, unexpectedly high labor costs for maintenance and cleanup, worker health and safety problems and issues with community relations. The U.S. Mine Safety and Health Administration estimates that 85 percent of conveyor maintenance is a result of fugitive material at conveyor transfer points.Technologies to improve transfer pointsA number of techniques to improve the performance of conveyor transfer points have been developed. They include:"

Jan 11, 2017

By R. M. G. S. Berezowsky

An atmospheric ammoniacal thiosulphate leach system was developed to recover gold and silver from residues of the ammoniacal oxidation leaching of sulphidic copper concentrates. Extractions of 88 - 95% Au and 83 - 98% Ag were attained within 2 to 4 hours at 40 - 60°C in thiosulphate leaching of the oxidation leach residues of Manitoba chalcopyrite concentrates analyzing 24.6% Cu, 0.18 oz/ton Au and 4.26 oz/ton Ag and a complex British Columbia chalcopyrite/tetrahedrite concentrate analyzing 18.5% Cu, 0.27 oz/ton Au and 276 oz/ton Ag. Parameters affecting the Au and Ag solubilization included thiosulphate, ammonia, and cupric ion concentrations, temperature, retention time and the degree of Cu extraction and sulphide oxidation in the primary oxidation leach. The precious metals were recovered from the thiosulphate liquors by zinc dust cementation.

Jan 1, 1979