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By Juliana Porto Guimarães

A crescente demanda por aços galvanizados com alta lubricidade tem impulsionado o desenvolvimento de pós-tratamentos que, aplicados sobre a superfície dos revestimentos, reduzem o atrito entre o ferramental e a chapa durante o processo de estampagem de peças críticas na indústria automotiva. Diante disso, a Usiminas desenvolveu, em parceria com a Quaker, a aplicação do pós-tratamento tipo microfosfato denominado Primecoat Z Auto, com a função de melhorar a estampabilidade de aços galvanizados a quente do tipo GI (Zn puro). Nesse estudo foi avaliada a Razão Limite de Estampagem (RLE) de um aço GI destinado a produção de peças críticas, após aplicação desse pós-tratamento em escala de laboratório. Adicionalmente, foram caracterizadas a morfologia e a constituição química do microfosfato, e o desempenho do aço quanto à fosfatização, à pintura automotiva e à resistência a corrosão. Concluiu-se que o filme de pós-tratamento é amorfo, constituído por Zn, P, Al e Mg, promovendo um excelente ganho de lubricidade ao aço GI, sem interferir nos processos subsequentes de fosfatização e de pintura nas montadoras. Além disso, o material apresentou excelente desempenho quanto à resistência à corrosão.

Jul 30, 2018

The Morley Coal Measures (Upper Cretaceous) at Ohai Coalfield were deposited in an intermontane basin alluvial environment of entirely terrestrial aspect. Within this regional setting, three distinct types of depositional environment are recognised; these are: (i) a sand-dominated (South Saskatchewan type) braided river system characterized by channel-bed dunes and possibly compound bars; (ii) a well-drained floodplain environment frequently subject to crevasse-splay and overbank-flow sedimentation; and (iii) a poorly-drained, commonly peat-accumulating backswamp environment locally traversed by tributary drainage systems and occasionally inundated by crevasse splays and overbank flows. All major coal seams of the Morley Coal Measures originated within forest moors under predominantly telmatic (periodically inundated) conditions. The peat-forming vegetation comprised largely arborescent forms (dominantly conifers), in addition to pteridophytes and bryophytes. In-seam vertical variations in coal type indicate groundwater levels initially decreased and then increased during the lifetime of a particular peat swamp, possibly in response to a change in the migration direction of an adjacent fluvial system. The proposed depositional model for the Morley Coal Measures has the potential to be utilised during exploration programmes and mine development to impart greater objectivity to predictions concerning seam geometry and continuity, trends in coal type and quality, and likely roof and floor conditions.

Jan 1, 1985

By Kevan Ford, Getulio Junior, Rob Henderson, Wayne Philips, Chris Martin, Rob Thorpe

"Plant 2 at the Kinross Paracatu gold operation in Minas Gerais State, Brazil, was commissioned in late 2008. Designed to be the largest tonnage, lowest grade gold milling operation in the world, Plant 2’s throughput has steadily increased towards its design capacity of 5087 tons per hour.The plant employs a gold-specific flotation scheme to recover the majority of gold, which is present as discrete free gold particles. Additional gold is recovered by jigs in the grinding circuit, and the jig concentrates are reground, upgraded and subjected to intensive cyanide leaching. The flotation cleaner concentrate is reground and leached using a conventional CIL circuit.One year after start-up, with the plant stabilizing operationally, plant circuit surveys were completed by a joint team from Kinross Paracatu and Blue Coast Metallurgy Ltd. The surveys audited the flotation and concentrate treatment circuits to investigate the metallurgical performance.This paper describes the Plant 2 operation and how the surveys were designed and executed. Some of the quality control systems that were employed to provide meaningful data from such a low grade gold ore are described and findings and actions taken to improve metallurgy as a consequence of the surveys are discussed.INTRODUCTIONThe Paracatu mine is located two kilometres north of the city of Paracatu, in the north western portion of the state of Minas Gerais, Brazil, 230 km southeast of the national capital Brasília (shown in Figure 1). The present day Paracatu mining operation, fully owned by Kinross Gold, through its Brazilian subsidiary Rio Paracatu Mineração (RPM) is designed to be the largest tonnage, lowest grade free milling gold operation in the world.The deposit currently hosts some 1.2 billion tonnes of ore at a grade of ~0.41 g/t gold, hence contains a total gold reserve of over 20 million ounces. At a designed plant throughput rate of 61 Mt/year the mine life goes beyond 2030."

Jan 1, 2011

By Sam Ammermann, William Heasley

"The mining industry is on an ever accelerating path to complete mechanization. As companiesutilize more sophisticated and efficient methods of blasting, a more thorough look should begiven to the pros and cons of mechanized shaft sinking. Historically, Vertical Shaft SinkingMachines (VSSM) have been capital intensive, making it hard to enter lowest bidder marketssuch as the United States. As advances in safety and technology have occurred, VSSM methodsare becoming increasingly common in many countries outside the United States. Decreasedcapital requirements, a greater amount of competition within the VSSM market along withgreatly improved safety practices, have made it more competitive with traditional drill and blast(D&B) methods. However, VSSM technology has yet to be embraced by the United States. Alarge culture shift will have to occur before VSSM technology will become common in theUnited States. The history, and advent, of raised boring machines will be discussed and how itrelates to the current development of VSSM technology. The researchers will analyze the uniquerisks of D&B methods and how they compare with the unique risks of VSSM technology. Theresearchers will put an emphasis on risks directly affecting the safety of personnel working onthe shaft sinking operation. Many of these risks are identified by contracting companies withregards to geology, relative location of resources and the chosen shaft sinking method. Theresearchers will discuss specific risks a given shaft sinking company will want to consider whenchoosing between D&B and VSSM methods."

Jan 1, 2016

By J Belke

Murrin Murrin Operations have not had a successful beginning. Numerous reliability and operability issues, many of which are the result of design decisions, have been addressed through mechanical and operational changes and the CCD circuit is no exception. Four design aspects of the CCD circuit that have caused and continue to cause operational problems are: the inclusion of solution neutralisation gypsum in the CCD circuit feed which was designed solely for HPAL residue without proper investigation of its impact on the achievable underflow density and resulting wash efficiency; the decision to construct the thickener base from thickened solids; the lack of redundancy in the overflow, underflow and tailings pipe work; and the lack of thickener operational flexibility in the central rake-lift and feedwell dilution system. In November 2002, the lack of operational flexibility in the rake-lift and the feedwell dilution system was improved through mechanical modification as follows:CCD1 rake mechanism was modified to allow central vertical lift of 600 mm; and CCD1 changed to forced dilution using the Outokumpu TurbodilRântechnology by replacing the E-DucânRtechnology of Eimco. The installation and the results of the CCD1 rake-lift mechanism and feedwell dilution system changes are discussed in this paper.

Jan 1, 2004

By Charles F. Seemann

It is with considerable trepidation that I set out to defend "litigation" to Design Professionals (DPs), as a better method of resolving disputes than arbitration, in the light of my personal feeling that an increasing amount of America's productive process is being squandered in litigation. Newer methods of dispute resolution, particularly arbitration, are fashionable, and opponents of these schemes risk being viewed as cynical or self-serving. My quandary is heightened since for some smaller disputes, arbitration seems clearly the better choice. I must concede, for example, that when the cost of dispute resolution--i.e., the cost of the process (such as arbitrators fees, attorneys fees, etc.), plus the cost impact of the non-productivity of involved employees--approximates the amount of the dispute, controlling that cost may be as important as a correct resolution. This principle is particularly true for small disputes arising during the progress of a project; it is probably more cost-effective for all parties to resolve their disputes quickly than permitting the dispute to drag out.

Jan 1, 1988

By M Scott, J J. McEwan

Silver and silver alloys tarnish readily by the formation of tarnish on the surface when exposed to a wide range of sulphur-containing atmospheres. This tarnish is unsightly and undesirable and can be removed either with a silver polish or a chemical dip. Polishes are, however, not suitable for irregular and embossed surfaces such as on coins, medallions and jewellery items, because of uneven removal of the tarnish layer and excessive wear. Successful tarnish protection can be achieved by either storing the items away from the aggressive atmosphere or by coating/treating the exposed surfaces with a protective layer. Storage is feasible for collections but is not suitable for items that are handled or worn regularly, such as jewellery. A number of commercial coatings and treatments have been developed, but to date there has not been a systematic evaluation of tarnish protection. This paper details the performance of a range of generic coatings in an accelerated tarnish test. The degree of tarnish was evaluated by means of loss in reflectivity and change in colour. Four coatings/treatments improved the tarnish resistance of silver by more than tenfold. These include an organic lacquer, rhodium electroplating and an organic self-assembled monolayer (SAM) conversion coating. Research is continuing to optimise these coatings. Keywords: silver alloys, tarnish resistant coatings, silver polishes.

Jan 1, 2006

To provide a flexible, low-maintenance, low-cost continuous mine air monitoring system as an alternative to conventional fixed-point, electronic monitoring systems. Background Continuous monitoring of mine air is highly desirable (and often required) not only to improve miner safety, but also to increase mine productivity. Continuous air monitoring systems can provide earl" warning of developing fires, excessive methane accumulation, reduced oxygen levels, and other developing problems in remote, inaccessible or sealed areas, and in active workings. Fixed-point, electronic systems require one Sensor for every gas to be measured at every defined monitoring location. As the number of monitoring locations increases, so does the cost, along with increases in the time required for routine maintenance and calibration of the sensor System cost also increases when monitoring locations are identified for mine areas requiring permissible electrical equipment.

Jan 1, 1988

By Harold A. Watson

A method for measuring leakage of vapors into a chemical-cartridge half-mask facepiece during simulated use is described. The respirator, fitted with high efficiency cartridges, is worn in a dichlorodifluoromethane (CC12F2)--air test mixture while a series of timed activities (facial movements, varied breathing, exercise, etc.) is performed. Complementing other tightness tests, this method is useful particularly for studying face fit and the effect of facial movements on leakage. The concentration of CC12F2 within the facepiece is monitored continuously to observe the immediate effect of physical activity on leakage. A composite sample is collected simultaneously in a plastic bag as a measure of average leakage during the 18-minute test period. Leakage, reported as percent, is calculated from the concentrations of CC12F2 within the facepiece and in the test atmosphere.

Jan 1, 1970

To be able to continuously monitor the noise to which underground workers are exposed as a better way to help prevent hearing damage. The Approach: The Bureau of Mines has developed a Time-Resolved Audio Dosimeter which can be worn by miners to record noise level every 30 seconds and store It in a miniature solid state memory. Figure 1 is a photo of the dosimeter. [ ] How It Works: Acoustical noise is picked up by a micro-phone and fed to a sound level meter which produces a d-c voltage proportional to the A-weighted sound pressure level. (As specified by federal regulations, the A-weighted sound pres-sure level approximates the response of the ear by discounting the higher and lower frequency components of the noise.) This d-c voltage controls an oscillator which, together with related circuitry, produces a pulse train having a frequency that's proportional to the noise level.

Jan 1, 1975

By O. Dojcar

The results of a laboratory investigation of rock fragmentation conducted with a model material were partially verified under field conditions. The object of the investigation was to study the qualitative and quantitative relations between the parameters of the primary blast and fragmentation to enable the planning of an economically efficient degree of disintegration with optimum utilisation of the blast energy. The three blast parameters that were considered were burden, specific charge and the ratio of spacing to burden

Jan 1, 1991

By O. A. Lima

Effective solids suspension is a necessary precondition for particle collection, and solids suspension is largely dependent on the hydrodynamics of the flotation cell. This study attempted to correlate the status of the suspension of apatite particles of different sizes in a Denver laboratory flotation cell versus the impeller rotational speed (N) adopted to operate the machine. The latter variable (N) influences the impeller capacity to lift the particles from the bottom of the tank and also to disperse them throughout the volume of the vessel. Such an impeller capacity can be characterized by the critical impeller speed for the accomplishment of solids off-bottom suspension (Nz) and also by the velocity of the radial water flow discharged by the impeller (U) divided by the particle terminal settling velocity (Us). This way, the status of the suspension of apatite particles inside the flotation cell can be characterized by one of three categories: ?segregation? (N/N2 < 0.60 and Us/U > 0.08); ?suspension? (0.60 = N/N2 < 1 and 0.06 < Us/U < 0.10); and ?dragging? (N/N2 = 1 and Us/U = 0.03). The range of impeller rotational speed (N), which was able to suspend the finest particles (Dp = 90 µm), was unable to suspend the coarsest particles (Dp = 254 µm). Conversely, the high value of N (N > 1,300 rpm), which is adequate to suspend the coarsest particles, may promote the entrainment of the finest particles to the froth layer.

Jan 1, 2009

By Lloyd Williams

1. The investigation shows that the Coal Creek has been the most productive, bed in Campbell County and contains the largest recoverable reserves of coal. The Pewee, Red Ash, and Jullico have been relatively productive beds and contain appreciable recoverable reserves of coal. The Blue Gem also has been productive in the past, but available information indicates that most of the remaining coal is Less than 28 inches thick. The Big Mary has relatively large reserves over 28 inches thick, but the coal is high in ash and sulfur. Thick partings in the Windrock bed have discouraged mining in that bed. The Poplar Creek and Rex beds generally are below drainage, and large areas have been excluded from the reserve estimate, Reserves in the Walnut Mountain bed will be difficult to mine due to the irregu¬lar thickness and lack of continuity of the bed. Estimated coal reserves are- small in the remaining five beds. 2. Known measured and indicated reserves of coal, based on a minimum bed thickness of 14 inches and on 1,800 short tons per acre-Foot of coal in place, are estimated to be 398 million tons as of January 1, 1953, o? this total, 267 million tons is in beds 28 inches and more thick. Areas in each bed were omitted from the estimate because available data relative to the bed characteristics are too meager to make an estimate that conforms with the definitions of measured and indicated coal adopted for this study. Should future drilling or development prove reserves in these areas, these should be added to the total estimated reserves.

Jan 1, 1956

By A. B. Cecala

It has long been known that ventilation is a cost-effective method to lower respirable dust concentrations in all types of mining applications. The National Institute for Occupational Safety and Health has been working on a number of different research techniques that use ventilation as a critical component to lower respirable dust levels at surface and metal/nonmetal operations in the United States. This article presents five such research efforts. The first research area discusses how improving the ventilation flow patterns in an iron ore mill facility lowered respirable dust concentrations by 31 pct throughout the primary grinding area. The second research area examines how respirable dust levels were lowered at a dimensional stone shop by using air cleaning units suspended from the ceiling. A third area discusses how improvements in ventilation at underground limestone mines lowered respirable dust concentrations. The fourth area examines how improvements in dust filtration and pressurization systems significantly impacted the air quality in enclosed cabs of surface mining equipment. The last area presents a newly developed clothes cleaning technique. This technique uses an air spray manifold to blow dust from a worker?s clothing in an enclosed booth, which confines the dust for capture and removal by a baghouse dust collector. These research areas represent an array of different control technologies to lower respirable dust concentrations. Ventilation is an integral part of these control technologies.

Jan 1, 2006

By D. E. Pollock, Andrew B. Cecala

It has long been known that ventilation is a cost-effective method to lower respirable dust concentrations in all types of mining applications. The National Institute for Occupational Safety and Health has been working on a number of different research techniques that use ventilation as a critical component to lower respirable dust levels at surface and metal/nonmetal operations in the United States. This article presents five such research efforts. The first research area discusses how improving the ventilation flow patterns in an iron ore mill facility lowered respirable dust concentrations by 31 pct throughout the primary grinding area. The second research area examines how respirable dust levels were lowered at a dimensional stone shop by using air cleaning units suspended from the ceiling. A third area discusses how improvements in ventilation at underground limestone mines lowered respirable dust concentrations. The fourth area examines how improvements in dust filtration and pressurization systems significantly impacted the air quality in enclosed cabs of surface mining equipment. The last area presents a newly developed clothes cleaning technique. This technique uses an air spray manifold to blow dust from a worker’s clothing in an enclosed booth, which confines the dust for capture and removal by a baghouse dust collector. These research areas represent an array of different control technologies to lower respirable dust concentrations. Ventilation is an integral part of these control technologies.

By D. J. Dollhopf

This research was part of an effort to investigate means of reestablishing non¬polluted hydrological systems in areas where surface mining directly impacts shallow ground-water resources. Chemically undesirable overburden material was selectively backfilled with the intent that it would be below the future root zone, be above the reestablished aquifer, and would not be leached as a result of deep percolation. After 2 years the buried material remains above the spoil aquifer and below the maximum rooting depth. Unsaturated water flow from the land surface to the buried material occurred during wet climatological periods. No significant leaching of buried material was observed, however. Overburden sample contamination from drill stem joint grease with Pb, Zn, and Cu additives caused substantial error regarding DTPA extractable trace metals. A grease with teflon and talc additives was recommended for use in future sampling programs. DTPA extractable trace elements in overburden material had no statistical relationship to post-mine ground-water quality. Overburden columns leached with water produced leachates comparable to overburden and spoil ground-water trace metal quality. A depositional model described the Rosebud Coal overburden as a fluvial system with distinct units of sand, silt, and clay, with distinct chemical properties. Physical and chemical characteristics of the model were comparable to the in situ geochemical system, a relationship which may aid in locating overburden materials unsuitable for reclamation.

Jan 1, 1979

By Gao Zhizhong, Zheng Shibo, Gu Zhengxing

Extensive research on the beneficiation of Florida dolomitic phosphate pebble has been carried out by Lianyungang Design and Research Institute of China (CLDRI) in recent years. Test results indicate that the fine-particle flotation process could be used to effectively recover the phosphate values from Florida high-dolomite phosphate resources. With the CLDRI fine-particle flotation technology, a phosphate concentrate with 31% P2O5 and less than 1% MgO could be obtained from a flotation feed containing 25.8% P2O2 and 2.2% MgO at an overall P2O5 recovery of up to 85%.

Jan 1, 1999

By Pedro Lilienfeld

This report describes the development, design, fabrication and testing of a port-able, battery-operated, light scattering monitor (henceforth to be designated as ILSDM) for the rapid measurement of the concentration of respirable dust in mining environments. This instrument incorporates state-of-the-art design characteristics and makes use of advanced solid-state components both for light emission as well as for its detection. The use of a pulsed light source combined with synchronous signal detection minimizes drift problems and optimizes the sensitivity of the measurement. Simplicity of operation, reliability and ruggedness, light weight as well as improved performance were salient objectives of this instrument development program. Continuous clean-air flow screening of all critical optical surfaces, and optimized optical detection and electronic signal processing design resulted in about a hundred-fold decrease of noise and drift with respect to precursor instruments. Equivalent mass concentration measurements 88 low as 10 micrograms per cubic meter can be routinely performed with time constants of about 2 second.

Jan 1, 1979

By Mônica Aline Magalhães Gurgel

Nas últimas décadas o setor siderúrgico vem desenvolvendo aços com maior valor tecnológico, surgindo assim várias classes, entre elas os aços avançados de alta resistência, onde encontra-se o aço bifásico ou “Dual Phase” (DP). Este aço é caracterizado por uma microestrutura ferrítica-martensítica, associada a uma matriz ferrítica com ilhas dispersas de martensita. Neste trabalho utilizou-se amostras de um aço baixo C e Mn, com micro adição de Nb e Mo, em desenvolvimento, onde se propôs uma avaliação da evolução microestrutural e propriedades mecânicas das amostras extraídas após a laminação a quente, a frio, seguida de recozimento intercrítico, em escala laboratorial, com auxílio de forno Mufla e um equipamento de análise termomecânica (TMA), resultando em taxas de aquecimento distintas, onde selecionou 7 temperaturas de encharque distintas e subsequente resfriamento com patamar isotérmico a 600°C por 20 minutos, onde observou-se que para esse ciclo a microestrutura com aspectos mais característicos de um DP se deu em tratamentos com temperatura de encharque entre 760 e 800°C.

Aug 17, 2017

By Wojciech Klecan

Cobb County, located on the northwest side of Atlanta, GA, is continually growing and, like many other metropolitan areas, it needs to increase the capacity of its waste water system to meet future demand. The Cobb County Water System (CCWS) is the responsible agency for water distribution, waste water collection and treatment in most areas of the county. CCWS, one of the most progressive agencies in the metro-Atlanta area, is addressing its future waste water capacity needs in the southern part of the county with the construction of the South Cobb Tunnel and Pump Station. This project consists of an 8.8-km- (5.5-mile-) long, 8.2-m- (27-ft-) diameter, tunnel boring machine (TBM) excavated waste water storage and conveyance tunnel; six tangential vortex-flow intakes ranging from 1,533 to 5,700 L/s (35 to 130 mgd) peak flow capacity, two construction shafts, six 1.8-m (6-ft) finished diameter connecting tunnels ranging in length from 6 to 975 m (20 to 3,200 ft) and a 5,700-L/s (130-mgd) wet/dry pit pump station. The pump station will have a semi-circular wet well with a dividing wall that extends almost to the top of the shaft and a spilt dry well for reliable operation. Roller gates will control the flow to the wet well from the tunnel. The pump station will have six 1,420 L/s (32.5 mgd) pumps and two sets of stair wells and elevators. With a finished diameter of 32 m (104 ft) and a depth of 62 m (204 ft), this is the largest pump station shaft constructed so far in Georgia for the dewatering of a waste water tunnel. The pump station shaft was also the highlight of the well attended and successful 2009 Shaft Design and Construction Short Course held in Atlanta, Sept. 10-11. The two-day course was sponsored by the Underground Construction Association of SME and Pennsylvania State University and concluded with a field trip to the pump station shaft. The tunnel starts south of the city of Austell and finishes at the South Cobb Water Reclamation Facility (WRF), located on the banks of the [ ] Chattahoochee River just north of Interstate 20 (Fig. 1). The South Cobb Tunnel will run 30 to 137 m (100 to 450 ft) below the surface, with an average depth of about 91 m (300 ft), through metamorphic rocks (Fig 2). The construction contract was awarded to Shea-Traylor JV with the lowest bid price of $305 million and notice-to-proceed was given on July 14, 2008. Jordan Jones & Goulding, Inc. (JJG) is the project designer and performed the geotechnical investigations. Parsons/Jacobs Associates is the construction manager. The South Cobb Tunnel is CCWS?s second deep hard rock tunnel. The 15.3-km- (9.5-mile-) long, 5.5-m- (18-ft-) diameter TBM excavated the Chattahoochee Tunnel was the first deep tunnel to be construced in Cobb County. Construction began in 2000 and the project was completed four years later. It is located about 16 km (10 miles) northeast of the South Cobb Tunnel in similar geology. It was designed by JJG to meet east Cobb?s long-term waste water capacity needs and provide flow equalization to the R.L. Sutton WRF. The Chattahoochee Tunnel was named ?Outstanding Civil Engineering Project of the Year? by the Georgia Sec-tion of the American Society of Civil Engineers in 2006.

Jan 1, 2009