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By André de Albuquerque Vicente

Foram estudadas as camadas de óxidos formadas nas superfícies de um aço inoxidável austenítico laminado do tipo 22.12, após oxidação ao ar a 800, 900, 1000 e 1100 °C, dentro de um projeto que visava uma melhor compreensão da oxidação a altas temperaturas ao ar de aços inoxidáveis resistentes a altas temperaturas. Utilizou-se o aço inoxidável austenítico microligado ao cério (253 MA®), que é um aço projetado para trabalhos a altas temperaturas. Várias técnicas complementares de análise microestrutural foram utilizadas, tais como difração de raios X e microscopia eletrônica de varredura com EDS acoplado. Observou-se a formação de uma camada não protetora de óxidos de ferro (Fe2O3, Fe3O4 e FeO) e posterior formação de uma camada protetora mais espessa de crômia (Cr2O3). Mais internamente observou-se a formação de SiO2.

Oct 30, 2017

By Tamara Caroline Guimarães Vilela

Neste trabalho foi avaliado o comportamento de propagação de trinca por fadiga de cinco aços utilizados na fabricação de trilhos empregados na construção e manutenção de vias permanentes brasileiras, por meio da realização de ensaios de propagação de trinca por fadiga (da/dN x ?K), utilizando-se a razão de tensões de carregamento R = 0,7 e comparação com os resultados obtidos com R = 0,1. Vários modelos de previsão do comportamento em fadiga foram avaliados. Observou-se a influência de R nos valores mais próximos ao limiar ?KTH, com diminuição considerável no valor de ?KTH para R = 0,7. Dentre os modelos matemáticos usados no ajuste das curvas sigmoidais da/dN x ?K, o que forneceu melhor ajuste foi o ajuste de Hartman e Schijve. O parâmetro K? proposto por Kujawski reduziu os efeitos de R na tentativa de unificar os dados em uma única e estreita banda de dispersão, porém, na Região I da curva, os dados ainda ficaram bastante dispersos.

Aug 17, 2017

In line with DML Resources continual forward management policies, the Roscommon Quarry operation has recently installed and commissioned a Nordberg 7 ft Symons cone crusher and a HP 300 cone crusher. Both machines have enhanced the production capabilities and quality control of the Roscommon comminuition circuit and they will provide efficient and reliable crushing well into the next century.

Jan 1, 1994

[JOSEPHSON, W. G.: The Argonaut Mine of Today, M88, 475 JOUET, C. H., biography, M29, 258 Joule-Thompson effect, 98, 381 JOWETT, J. H., biography, M83, 276 JUDSON, S. A.: Operations in the Gulf Coast of Texas and Louisiana for 1926, G26, 659 JUDSON, S. A., EASTON, H. D. JR. AND SCHAEFFER. W. A. JR.: Estimation of Petroleum Reserves in Prorated Fields 114, 11. Abs., YB35, 50 JULIHN, C. E.: Copper---An Example of Advancing Technology and the Utilization of Low-grade Ores. Brookings Lecture, in Mineral Economics (1931 volume, B. W. Mudd Fund)]

Jan 1, 1936

By T. G. Carter, R. I. Miller

First, the influence of variation in the

Apr 1, 1995

By Raymond W. Henn, Kent A. Pease, Glen J. Rorison

The paper focuses on construction of a 2.55-km (8,365-ft) long, 2.4-m (8-ft)diameter storm drain tunnel in Evansville, Indiana. The tunnel was driven through saturated soft ground varying from clay to fine sand. The paper presents: an overview of design and design rational including specific EPB machine requirements; the contractor’s proposed and accepted alternative construction methods and TBM design; and construction issues and performance. Some of the key points discussed are the use of the TBM in different operational modes for alternative ground conditions, the effectiveness of dewatering systems, production rates, and issues such as surface settlements and gas.

Jan 1, 2001

By Charlie Adcock, Rob Farnfield, Andy Wetherelt

The ISEE Blasters Handbook gives guidance on the level of air overpressure likely to cause occasional window breakage (151dB) and general window breakage (171dB). A long-term safe level of 140dB is also suggested. This guidance is widely used by demolition and other contractors to assess damage zones in the region of explosive applications employing unconfined charges. Other reference material gives more detailed guidance relating to window area, aspect ratio and glass thickness. Despite the guidance given in these references, complaints by members of the public regarding window breakage continue to be received by explosives engineers from air overpressure levels well below the longterm safe limit. Such complaints are not limited to the use of unconfined charges but can even be generated from the highly confined use of explosives in quarry blasting. This paper describes a series of experiments with explosive charges fired in unconfined conditions close to various window configurations. The aim of the work was to test the existing guidance levels and to extend the knowledge base in this area. Topics covered include the role of differential pressure across windows in the walls of an enclosed space such as a room.

Jan 1, 2006

By N. A. D. Parlee, I. D. Shah, W. C. Phelps

THIS note reports on a continuation of a program on the thermodynamics of Fe-S-X systems in the "steel-burning" temperature range begun by Bock, Barloga, and parlee.' Small coils of 0.039-in.-diameter pure iron (Ferrovac-E) wire were equilibrated with Fe-S-0 melts in ingot iron crucibles under argon at 1324°C in the assembly shown in Fig. 1, the lower part of which was heated in a large Globar furnace. Fig. 1 shows (R) the coiled iron wire sample, (M) the Fe-S-0 melt prepared from desired proportions of ferrous sulfide and ferric oxide, (K) the iron crucible, (I) a mullite guide tube, (J) an alumina crucible, (L) alundum sand, (N) crushed mullite, (Q) hollow cylinders of K30 brick, (C) a steel rod, (B), (El, (F), (G), (P), and (O), details of brass water-cooled head, and (H) a mullite tube 2-3/4 in. ID and 26 in. long. The rod (C) bearing the sample could be removed at will and be replaced by a tube for sampling the melt, or by a thermocouple for comparing the melt temperature with a control thermocouple not far from the 2-3/4-in. mullite tube. After equilibration the iron coils were treated with acid to remove the outer layer of metal and then they were analyzed for sulfur by a standard combustion method. The melt samples were analyzed for oxygen by a variation of Lander's2 hydrogen-reduction method for mattes, and for sulfur by the ASTM combustion-iodometric method NO. E 30-47. When the results of some forty-two runs were examined it was found that the sulfur and oxygen contents of the equilibrated melts showed good consistency, in that the plotted compositions fell along the smooth curve shown in Fig. 2. The points on this curve represent the experimental compositions of melts in equilibrium with ?-iron (Fe-S-0) solid solutions. These solid solutions are saturated with sulfur and oxygen with respect to the melt and therefore have the same sulfur and oxygen activities as the melt. The curve drawn through the points therefore delineates the ? liquidus. It falls in such a position as to roughly confirm the liquidus curves of Hilty and crafts3 at 1200" and 1300°C which are

Jan 1, 1965

By John E. Shively, Tracy K. Lundin, Francis Fong

The Superconducting Super Collider (SSC) features two 20 TeV counter rotating proton beams which will be housed in 87 km (54 miles) of tunnel. Four additional lower energy particle accelerators will be housed in 26 km (16 miles) of tunnel and underground structures. Physics experiments will be conducted in two underground detector halls approximately 67 m (220 feet) deep with footprints measuring about 30 m (100 feet) by 100 m (330 feet). Definition and design of underground facilities is advanced with construction of approximately one-third of the SSC program underway. This paper presents an overview and status of the SSC project.

Jan 1, 1993

By M J. Begbie, K B. Sporle

The Golden Cross low sulfidation epithermal deposit produced approximately 750,000 ounces of Au from two ore zones: the underground Empire Vein System and the open pit stockwork. The Empire Vein System has at least eight stages of vein formation: (1) sulfide veins, (2) black veins, (3) massive veins, (4) banded veins, (5) thin white veins, (6) crumbly veins, (7) massive/platy calcite veins, and (8) flattened rhomb calcite veins. Gold mineralisation occurred relatively early in the lifetime of the system, dominantly during 2 through 4. The late calcite veins (7 and 8) and early sulfide veins (1) are barren. The vein system formed in a dominantly extensional environment, though some compressional faulting may have also existed during vein formation. There is no evidence for significant strike-slip faulting during vein formation, highlighting the fact that explorationists should pursue on-site structural patterns rather than fashionable models.

Jan 1, 1998

By W. L. Cooley

Electrical accidents occurring in coal mines from 1975 through 1979 were categorized and analyzed. The data was searched for common electrical hazards, common activities on the part of those injured, and common negligent or careless behavior. The most common electrical hazard was abnormal arcs or sparks, the most common injured activity was handling energized trailing cables, and the most common careless behavior was failure to de-energize circuits before working on them. The accident data was combined with mine production statistics to form a normalized electrical accident rate. It was found that some mines have consistently more lost workdays per man-hour worked than do other mines. Bureau of Mines electrical safety research contract expenditures were reviewed to judge whether the research effort was directed to those areas which are related to the most accidents. In some cases it was not. A method was devised and utilized to estimate the relative cost to the mining industry to implement certain safety measures developed through Bureau research, and also to estimate the potential safety benefits. Some safety changes are recommended, others are not. MSHA regulations were reviewed for effectiveness in preventing electrical accidents, and suggestions were made for discontinuing, clarifying, or otherwise modifying the regulations.

Jan 1, 1981

By Mohammad Eslami

The Tabriz-Urmiyeh Highway shortens the distance of north-western cities of Iran by about 130 km, resulting in improved access and efficient transit between Iran and Europe through Turkey. The highway crosses the Urmiyeh Lake, an inland lake surrounded by mountains. Due to the circulation of salt-water in the lake and the necessity to continue shipping between adjacent ports, a waterway should be kept open. Consequently, a bridge was built to provide access of marine traffic. A causeway bridge had a length of 1,260 m, comprising of 19 spans. In construction of the bridge, more than 400 piles having a total length of 32 km have been driven. For design of piles different methods have been used such as static analysis, dynamic testing, and correlations to in situ tests, such as cone penetration test (CPT). This paper presents construction of bridge substructure, full-scale piling tests, and methods of analysis used in the evaluation of the deep foundation capacity. The presentation includes an assessment of four current direct CPT and one CPTu methods to calculate the bearing capacity of the piles. It was found that the CPTu and dynamic testing are two suitable tools for rapid and optimum pile design and verification.

Jan 1, 2010

By S. Titkov

At present, Russia is engaged in processing, 3new plants of hard-to-process potash ores with increased content (up to 10 - 12%) of insoluble impurities (insoluble residue ? I.R.). This required additional research to improve the process of potash ores flotation. Based on the study of the effect of dispersive properties of frother and its flow rate on the efficiency of aliphatic amines with different length of the hydrocarbon radical (as sylvite collector) there was showed the possibility to apply high molecular amine with length of hydrocarbon radical C20 ? C26 by normal temperature of circulated plant salt solution (saturated solution KCl ? NaCl ? H2O). There was designed and tested in plant conditions the modified amine collector with the length of the hydrocarbon radical C16 - C26, improving flotation of Sylvite under normal temperature of circulating salt solutions at potash flotation plants. There was made the study of the influence of the hydrocarbon radical length of alkylmorpholine on the Halite flotation from intermediate products of sylvite recleaner flotation with different content of I.R. (silicate-carbonate slimes), at normal and elevated temperature of salt solution. On the basis of the application of modified alkylmorpholine for Halite flotation, there was developed the process of further beneficiation for the intermediate products of sylvite recleaner flotation from potash ores with increased content of insoluble impurities, which can eliminate the circulation of the intermediate products in the process flow sheet of sylvinite ore processing and increase the KCl recovery into the finished product. Keywords: flotation, potash, halite, alkylamine, alkylmorpholine

Sep 1, 2012

By Jim Belous

Fluid Dynamic Modeling (FDM) was used to develop solutions how to eliminate the fugitive emissions from the meltshop building and to comply with the EPA “6% opacity from the furnace operations” rule. Secondary Emission Control (SEC) system performance was simulated by an inverted 1:96 scale Plexiglas model of the entire meltshop, utilizing the negative buoyancy effects of saline solution in water. Test results show that with the installation of the internal partition wall which separates furnace aisle from the caster aisle, significant improvement of the SEC system is achievable, thereby avoiding large expenditure for the expanding a fume collection system capacity.

Aug 17, 2017

By Witold J. S. Ostrowski

The shaft structure being part of an underground mine, depends on programned functional duties, and on geological and hydrological conditions. The majority of Canadian metal mine shafts are in hard competent igneous rocks, which are in an elastic state of equilibrium around the excavation. Others penetrate soft sedimentary or very weak water-bearing rock formations in which the equilibrium varies from plastic to hydrostatic. Knowledge of how to interpret the underground conditions, determine acting forces and design proper structures is essential for the production and safety of the future mine.

Jan 1, 1973

By H. G. Naidu, Raj K. Singhai, S. P. Singh

Introduction The economics of open-pit mining de¬pend heavily on the cost of overburden removal. It is necessary to maintain a pit slope as steep as possible. Steeper slopes lower the volume of overburden to be handled, thus lower the cost of material handling. There is, however, a limit to which the pit slopes in any given situation can be steepened. Steepening beyond this point could jeopardize the pitwall stability, ren¬dering it unsafe. It might even result in curtailment of pit production. Several factors affect the stability of pitwalls. Some are natural, such as topogra¬phy and regional and local geology. Others are man made, such as pit geometry, ground water management, equipment, drilling and blasting, and the type of excavation. Greater control can be exercised in the latter with proper planning and by following a set of procedures based on field experiences. This article deals with one such control¬lable factor - drilling and blasting. The eco¬nomics of steeper pit slopes is discussed, followed by a record of drilling and blasting practices in western Canadian surface mines. Microprocessor-based instrumentation and its application to blasthole drilling is also described. Economics of steeper pit slopes The economics of steeper pit slopes is not a new issue. It should be reinforced, though, that pit slopes must be as steep as possible to ensure maximum recovery of minerals at a minimum stripping ratio. For operating, economic, and safety reasons, different pit slopes are maintained during different phases of pit development. Figure 1 shows a hypothetical ore body, cylindrical shape, with a radius of 225 m (740 ft) and located 30 m (100 ft) beneath the surface. The mining operations are planned at two different slope angles of 25° and 40°. The ultimate pit depth was established on the basis of the criterion of "break even pit." The variation of the stripping ratio at differ¬ent mine levels is shown in Fig. 2. Table I summarizes the eco¬nomics involved for two pit slopes, 25° and 40°. Figure 3 presents the profits during the life of the mine for these two pit slopes. This study shows that steeper slopes for an open pit operation are far more advanta¬geous than flatter slopes. But, what is the optimum slope at any one point in the life of a moving pit? And how can the stable slopes be maintained over the short- and long-term? Canadian blasting practices A survey of blasting practices in western Canadian surface coal mines revealed that, at most mines, hard consolidated overburden is drilled and blasted. Blastholes are drilled with rotary crawler-¬mounted rigs using bits in the 220 to 310 mm-diam (8.5 to 12 in.-diam) range. Typi¬cal hole depths are 12 to 18 m (40 to 60 ft) to accommodate the pit bench heights of 12 to 15 m (40 to 50 ft). For a 12-m (40-ft) high bench, a typical hole will be 14.6 m (48 ft) deep including the subgrade drilling of 2.6 m (8.5 ft). Half of this hole will typically be a powder column and half will be stemmed. For a 15-m (50-ft) bench, a typical hole will be up to 18 m (66 ft) deep including the subgrade drilling. Drilling patterns are usually 9 m (29.5 ft) spacing and 9 m (29.5 ft) burden. De¬pending on local geology and hole diameter selected, drilling patterns of 8 x 8 m, 8.5 x 7.3 m, and staggered patterns of 11 x 5.5 m

Jan 1, 1989

By George Weaton

Two years ago the general features of the St. Joseph Lead Company's zinc-smelting process were described.1 At that time the discussion was limited to a description of the production of high-purity electrothermic zinc oxide. The present paper will describe the commercial production of electrothermic zinc metal. Since a fairly complete description of the plant of the Josephtown smelter was given in the earlier paper, the brief recapitulation given here will be limited to mention of additional equip-ment recently installed and a bare outline of the preparatory process. The raw material is zinc sulphide concentrate received from the com-pany's mines in St. Lawrence County, New York. An average dry-weight analysis of this material is: Zn, 58.28 per cent; Pb, 0.56; insoluble, 1.6; Si02, 1.12; Fe, 6.4; CaO, 0.47; MgO, 0.27; S, 31.9; Cd, 0.1; Cu, 0.06; Mn, 0.24. Moisture content is usually about 3 per cent. Three 21-ft. 6-in. diameter, 12-hearth Nichols-Herreshoff furnaces roast the concen-trate to a calcine of average composition (first 10 months of 1938) : Zn, 67.69 per cent; Pb, 0.06; insoluble, 1.75; Si02, 1.26; Fe, 7.24; CaO, 0.47; MgO, 0.36; S, 1.88; Cd, 0.1; Cu, 0.07; Mn, 0.27. The sulphur dioxide gas, after passing through a waste-heat boiler, proceeds through a recently redesigned low-resistance gas-purification assembly to the contact sul-phuric acid plant, of which the capacity is 200 tons of concentrates per day. The calcine is mixed with a portion of returned furnace residues and sintered on 42-in. by 44-ft. Dwight-Lloyd sintering machines, gas-fired. Wind-box gases pass through air coolers before filtering in a 1440-bag Dracco unit, and thence to stack. The Dracco fume is mixed with Cottrell dust, from roaster gas cleaning, and sent to the leach plant, where it is roasted (SO2 to acid plant) and leached with sulphuric acid to recover, as end products, lead sulphate, zinc sulphate and cadmium.

Jan 1, 1939

By Staff

The goal of the U.S. Bureau of Mines diesel engine research program is to reduce exhaust emissions from diesel-powered equipment used in underground mines. This research has led to significant advances in aerosol measurement and to the development of more effective emission controls. This Information Circular contains reports of some of the presentations made at the Bureau's Information and Technology Transfer Seminar on Diesels in Underground Mines given in Minneapolis, MN, on September 29-30, 1992. The seminar emphasized the measurement and control of diesel particulate matter emissions. Topics covered include a discussion of the health issues associated with the use of diesel equipment underground, an overview of regulations, measurement techniques for diesel exhaust aerosol, levels of diesel exhaust pollutants found in mines, and modern emission controls. An appendix is included that contains a report describing the capabilities of the Bureau's diesel emissions research laboratory, two papers describing the effects of engine maintenance or: emissions, a paper describing the monitoring of carbon dioxide in mine air as an indicator of air quality, a glossary, and a list of abbreviations and acronyms.

Jan 1, 1992

By J. Temporal

An introduction to the conference material in this issue is given together with the issue contents list, closing remarks by its chairman Dr. J. Temporal, the list of contributors and their companies, and the information that the 26th Sir Julius Wernher memorial lecture had had to be presented by the lecturer's wife, M. Biggart, in his absence due to site problems on the Storebaelt project

Jun 16, 1905

The Aredor mine employs conventional dragline methods to exploit alluvial diamond deposits. Production began in 1984 with the policy of mining in the terrraces during the wet season and in the river flats during the dry season. Early production failed to meet predicted grades. A major geological programme to re-evaluate existing reserves was undertaken. This resulted in considerable increases in reserves in the river flats. Many of the reserve blocks included flats on both banks of the Baoule river. Methods of access into the river flats, normally flooded in the wet season, were developed to allow mining throughout the year. River diversions have been the main method used to provide access into the reserve blocks and, most importantly, to remove the risk of flooding. Aredor has carried out six main river diversions with a total length of 12 km. The diversions allowed production planning to be made on the basis of the economic evaluation of the reserve blocks, without undue regard to natural ground conditions or to seasonal factors. The Manning equation was used for the calculation of channel dimensions and gave satisfactory results. The practical aspects of the diversion preparations and flooding prevention are described

Sep 1, 1991