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By Barbara J. Arnold

The Electric Power Research Institute (EPRI) and six EPRI-member utilities are sponsoring research to define relationships between coal properties and coal handling behavior. Deratings and outages caused by plugged chutes or bunkers or frozen coal can cost utilities millions of dollars annually in lost energy production as well as in manpower to restore coal flow. There is also the added expense of maintaining redundant equipment to assure a continuous coal feed to the boiler, a common practice for utilities. Over the past two years, researchers at CQ Inc. and Iowa state university have collected and analyzed coal samples to develop a coal handleability index for utilities to use when specifying coals for their power plants. These coal samples cover ranges in ash content, rank, grindability, size distribution, and moisture content--properties that affect the handling behavior of coals. Other properties, such as the washability and ash composition, are measured as well. Over the remaining two years of the project, all of these analyses will be correlated to handling behavior, measured using a triaxial shear tester that determines the strength of a coal under compression. An index will be developed and validated at host utility power plants.

Jan 1, 1991

By A. Paviani

The subject of this session is "Equipment Installa­tion, Recent Developments". This is a subject which is not usually addressed at conferences of Foundation Engineering. It is rare to find sessions dealing with the technological side of deep foundations, a subject which only recently seems to have aroused sufficient interest at national and international conferences. It is therefore natural for the subject of "Equipment", or the tools used to implement the various "technologies", to be over­looked or mentioned only occasionally during the discussion of other issues. At conferences, most of the attention is attached to research and to the theoretical interpretation of the performance and behaviour of deep foundations, as well as to establishing the most suitable calculation algorithms and approaches for the study, design and control of foundation structures. It is almost as if the subject of equipment is felt to be less important or, perhaps, that it is considered to belong more strictly to mechanical engineering than to civil engineering.

Jan 1, 1994

By L. Chunpongtong

Compared to equipment used in hard rock mines, the lifespan of equipment deployed in oil sands operations tends to be shortened due to the abrasive nature of the material and soft ground conditions in which it operates. One of the challenges of oil sands mine planning is to determine the most cost-effective replacement time for aging equipment. For cost engineers dealing with aging equipment, the options become an economic trade-off between taking the chance of higher frame failure or buying new equipment. Therefore, the ultimate question is: “When is the best time to replace the equipment?”

Jan 1, 2012

By Dirk Bleazard

Barrick Goldstrike Mines is improving the reliability of mining and processing equipment through the use of failure analysis and condition monitoring activities. Program results include an increase in equipment capacity and an overall reduction in operating costs. Identifying equipment failure modes and developing associated capital asset management practices can minimize failure consequences. Successful programs have included alterations to management practices, equipment modifications, and/or the implementation of condition monitoring programs. By controlling or minimizing the effects of incipient equipment failures, corrective actions can be taken earlier in the failure cycle. This results in an associated reduction to repair costs and equipment down time. Mining companies invest in their capital assets to provide the capacity necessary to meet operational needs. Over time, functional failures occur that reduce this productive capacity. Diagnostic technologies now exist that allow the condition of equipment to be monitored. Early response to this information minimizes the effects of functional failures and restores equipment re- liability. Reliability is a performance indicator of overall equipment condition. It is most often expressed in terms of mean time between failures. When the established objectives of a capital asset management program include the maximization of this failure interval, trailing indicators, such as availability and operating cost improve. The probability of equipment failure is influenced by engineering design and operating conditions. The performance level resulting from this operating environment is expressed as "inherent reliability." Without maintenance intervention, equipment will ultimately fail to perform its intended function and become less reliable. Therefore, maintenance must be managed as the supplier of reliable operational capacity. Maintenance can only supply equipment performance that approaches the level of inherent reliability. Actually achieving inherent reliability requires that all maintenance decisions are made at the economically optimal time. Enhancing performance levels beyond inherent reliability can only be achieved by altering operating conditions or practices or through physical equipment modifications. An evolution in maintenance management philosophy has been under way since the beginning of the industrial revolution. As equipment has become more sophisticated, so have maintenance practices. At the beginning of the industrial age, equipment tended to be over designed and slow moving. The first maintenance philosophy was one of reactive maintenance. Maintenance intervals were dictated by the operational status of the equipment. As a result, production interruptions were common and capacity needs were met through an investment in redundant capital assets.

Jan 1, 1998

By Max B. Holfeltz

[Many factors impact the selection of one mining method over another for deep seated, thick seam coat deposits. Generally if an operating mine is recovering coal at high volumes from thick seams then a truck/shovel fleet is required for coal loading. The next consideration is how to remove the associated burden. If an operation has relatively small amounts of burden associated with the coal then a truck/shovel fleet may be employed for burden removal simply to standardized the entire mine equipment concept. On the other hand large amounts of burden associated with the coal can justify employment of draglines for burden removal. Specific economic, productive, and physical factors contribute to the final decision.]

Jan 1, 1983

By G. R. Waters

NMR360 is developing a suite of chloride-based metals extraction processes, with the first commercial operation scheduled for commissioning late in 2018. It is critical, therefore, that with the introduction of any new technology, that the circuits do not suffer from mechanical failures which will compromise the operation. Although chloride leaching is at atmospheric pressure and relatively low temperature, the main challenge is preventing corrosion, since the high proton activity makes even a small amount of acid behaves as though it were concentrated. An additional challenge in concentrated chloride circuits is the potential for solids precipitation. In this context, therefore, correct valve selection is crucial, and NMR360 has partnered with CGIS to ensure that the Severe Service Valves (SSVs) needed will perform over and above the definitions of the Manufacturers Standardization Society (MSS) of the Valve and Fittings Industry. This paper outlines what the minimum requirements are for SSVs in chloride leaching applications, drawing on five decades of industry experience from one of Canada’s leading valve experts.

By J. K. Lemley

The human element in large measure dictates success in contracting relationships. Because of our professional backgrounds, we view contracts primarily as either engineers, contractors or owners. A beneficial contractual environment--one in which decisions, risks and benefits are shared--demands equal consideration of all three points of view. Most of the older cities in the United States, for example, suffer from bad contracts--generalized, patched-together documents that represent an accumulation of modifications originally written to compensate for specific situations that have occurred over the years. Because such documents lack coherence, they often present conflicting instructions which lead to defensive, ultimately destructive attitudes among the parties involved in the day-to-day administration of the project. Good contract development begins with a strong central philosophy to which the details of the contract can be related. First, the owner should establish a comprehensive philosophy in which risks between the parties are identified. Following this, a specific contract document can be written to satisfy this established philosophy. The contrast between two opposed contractual situations, NYC Water Tunnel Number Three and the Seabrook Nuclear Power Plant Cooling Water Tunnels, illustrates how comprehensive, well-written contracts--contracts which share both risks and benefits--provide the basis for achieving quality construction that will reward engineer, contractor and owner.

Jan 1, 1983

By Diego José Inforzato

Hot tensile data were correlated with creep data, in Aluminum Alloy AL7475-T7351, as part of a broader research program, aiming at the validation of a methodology that proposes an equivalence between the two kind of results, for metallic materials in general. The methodology is based on a criterion that establishes correlation among the following parameters from each test: the strain rate, ultimate tensile stress, and time to reach the ultimate tensile stress, in tensile tests, are equivalent respectively to the: minimum strain rate, applied stress and rupture time, in creep tests, for a given test temperature. The present material was tested at 3 temperatures: 133,166 and 193ºC, using 3 nominal tensile strain rates in the hot tensile tests: 3.2x10-6, 1.6x10-4 and 6.4x10-3 s-1 and 9 applied stress levels in the creep tests, varying from 140 to 400 MPa. The conversion of the hot tensile data to creep-like data allowed performing the analysis of all the results together according to the traditional creep relations proposed by different authors, namely: Norton, Arrhenius, Zener-Hollomon and Monkman-Grant, with the determination of the corresponding parameters in each case. The equivalence between hot tensile and creep data is also confirmed for this aluminum alloy.

Aug 8, 2018

By Gilmar Ferreira Bataglia

The possibility of parameterization of hot tensile data together with creep data is investigated, for Aluminium Alloy 7475-T7351. This study represents part of a broader research program aiming at the validation of a methodology recently proposed for analyzing both kinds of data together, considering different metallic materials. The results presented in Part 1 of this work, were analyzed according to 4 traditional methods of the literature for parameterization of creep data, namely: Larson-Miller, Orr-Sherby-Dorn, Manson-Succop and Manson-Hafferd. The compatibility of the hot tensile test results with those of creep is remarkably good, indicating the possibility of using both kind of data together also in extrapolation schemes. The criterion proposed for equivalence between hot tensile and creep data is verified to work well also for this kind of material, under the present experimental conditions.

Aug 8, 2018

By Cindy Schiewek

Industrial injury occurrences are an ongoing concern for Mine Operators. Along with the personal suffering of injured workers comes an increase in compensation and productivity costs. Growing recognition of repetitive stress and bodily injuries, accompanied by recent studies, validates the assumption that a relationship exists between ergonomic injuries and machine design. Intuitively, there is a belief that an ergonomically designed machine will reduce repetitive stress injuries through design and education however; quantifying this belief has been a challenge for Mine Operators. Sandvik Tamrock has undertaken a project aimed at developing a business model to assist in quantifying the benefits of ergonomic intervention. This model focuses on distinguishing and quantifying this method of intervention to allow for a better evaluation of the machine. For simplicity, the project initially focused on the Face Drill Jumbos. The target of the project was three fold: !" Recognition of the cost drivers for compensation; ergonomic injuries !" Identification of the relationship between ergonomic machine design, and the decrease of the negative effects associated with the cost drivers !" Systematic prioritization for ?prevention by design? The project findings substantiate the expected reduction in injuries and compensation claims. Based on all ergonomic intervention studies conducted, each case showed a reduction in compensation cost; through prevention by design, one can reduce the amount of potential risk. The paper addresses the resources and methodology used, along with the findings and its relevance to the issues that face the Mining industry.

May 1, 2003

By M. Z. Emad, M. U. Khan, A. ur Rehman

Stemming plugs are used as an accessory in drilling and blasting industry. They supplement conventional stemming material (i.e. drill cutting) with retention of gases in the drill hole that result in better fragmentation of rock and improved explosive utilization. Better fragmentation and explosive utilization along with economic benefits enhance efficacy of the project. Incorporation of stemming plugs in drilling and blasting industry is in exercise for about thirty years. The efficiency of stemming plugs is a key factor in their rising induction in mining industry. Different studies have been conducted on the economic viability of these plugs. The focus of this paper is the selection of stemming plugs for a bench blasting operation and the examination of blasting operation efficiency based on ergonomics and human factors. Three types of stemming plugs were evaluated during multiple blasts at a limestone quarry. Their performance was evaluated using split desktop software. Based on the human factors plastic molded stemming plug (stemming plug-1) was found to be the best among all selected plugs. INTRODUCTION Surface mines and quarrying operations heavily depend on bench blasting to achieve high volumetric targets and production demands. Use of explosives is the most economic method adopted for rock breakage and movement. Extensive research had been performed to enhance explosives energy utilization. This include changing the drilling pattern, application of air decks, stemming plugs, and use of other supportive devices. Optimization of explosive energy has been a major concern in those mines that rely on drilling and blasting operation to carry out main production. Due to continually increasing cost, efficient mining demands, and associated hazards of using explosives, it is necessary to utilize explosives at their best. Efficiency of a blasting operation is generally evaluated by the fragmentation size. From post blast conditions at blasting site to efficiency of processing plant, anything can be affected due to improper blast resulting in bad fragmentation. Better fragmentation is necessity for better operation of the system along with consideration of the safety of operation, environmental issues and related costs. For developing a blast design, an engineer should always attempt to minimize the cost of operation without compromising with acceptable technical and safety necessities [1]. Blast performance is dependent on many different factors associated with the process. These factors have been gauged as blast geometry, explosive specification, and rock mass properties [2]. Similarly, in 2013 Mohammad et al. concluded that fragmentation dynamics depends on blast hole diameter, primer, spacing, stemming, burden, and delay timing for blasting operation [1]. At the work site where this study was performed, blast holes were filled by drill cuttings and muds to help in confining gases. In a blast hole, gas confinement helps in better rock fragmentation along with reduced flyrocks. This practice is most common in many countries including Pakistan. Due to lack of homogenized particle size, the effectiveness of confinement is variable and majorly based on the size of stemming. Extremely small sized drill cuttings often result in hole blow out along with flyrocks from the collar. This improper blast energy will result in poor blast, bad impacts on environment, and reduced operational efficiency. In addition to the stemming material, the length of stemming is also a prime consideration. The decrease in stemming length will increase the quantity of explosive in the blast hole and an increase in stemming material generally improves stemming performance.

Jan 1, 2019

By P Christen

The Ernest Henry Copper gold mine situated in North West Queensland, Australia, is owned and operated by Xstrata Copper. Currently the open pit produces 11 Mtpa of ore. With open pit mining ceasing in mid 2011 development has begun on an underground sublevel cave mine to extend the life of the operation by another 12 years. When completed the open pit will be 530 m deep and 1.5 km in diameter. The orebody dips at approximately 45° and has been outlined a further 450 m below the base of the pit. This provides some challenges for the Ernest Henry underground mine which is designed to initially truck development and production ore from the end of the pit until a hoisting shaft is commissioned in 2013. Production will then increase to 5.0 Mtpa on its way to an ultimate rate of 6.0 Mtpa in 2016.This paper will focus on the capital development and infrastructure requirements for the underground mine. Areas covered include mine accesses, ore handling system, accommodations for the dip of the orebody, primary ventilation design, dewatering systems and selection of an underground workshop over surface only maintenance.Discussions include the complications arising due to the mine being located directly below a large open pit and the combination of first principle cost analysis and risk assessment which has been used to safely optimise the feasibility study designs.

Mar 21, 2011

By R. S. Shoemaker

Environmental and regulatory authorities are increasingly requiring that precious metals heap leach piles be contoured before they are abandoned so they may present a more "natural" look to the eye. Depending on the ore type, many of these contoured heaps will be subject to substantial erosion by precipitation events, native plants will have difficulty in establishing themselves and slimes be washed onto surrounding areas or into watercourses. This paper presents the argument that the results of contouring heaps are counter to good environmental practice. Calculations which have been made demonstrate that leveling and berming the heap tops as well as berming the edge of each lift or setback will effectively prevent water erosion and promote the growth of native plant species.

Jan 1, 1993

By Henry Fay

THE erosion of guns is a complex problem which can be solved only by a detailed study of all the factors involved. In the present paper it is proposed to submit the results of observations and experiments which have extended over several years. Certain facts have been established and preliminary reports have been published.' Conclusions have been reached since then which, it is believed, are worth presenting for the purpose of promoting discussion, and with the hope that ultimately the whole truth will be known. The particular phase of the problem which will be presented here is the hardening of the inner surface of the gun tube. It has been known for a long time that after firing a large caliber gun for some time, the surface of the metal becomes hard and brittle, cracks, and wears away.2 The character of this phenomenon may be learned by an examination of some results which are typical, obtained from a detailed study of a 12-in. gun. The gun was trepanned and rings representing various sections of the gun were cut out for examination. The first ring represented the metal at the muzzle end, and the other rings were removed at approximately 120, 240, 325 and 337 in., respectively, toward the breech end. The appearance of the surface of the metal in the different sections is shown in Fig. 1. The greatest amount of wear and maximum amount of hard surface layer was found in section marked E, which is nearest the powder chamber and at the beginning of the rifling; the maximum amount of cracking in D; the maximum amount of copper deposition in C. Section B showed heat cracks on both lands and grooves, and section A showed heat cracks on the driving edge of the lands only. There was much flow of metal in both sections E and D, and there was progressively less effect noticeable toward the muzzle end. The polished cross-section of these same pieces is shown in Fig. 2. The

Jan 12, 1916

Jan 1, 1951

Jan 1, 1951

By Randolph E. Scheffel, David C. Fitch, David K. Hogan, Mark R. Welsh

In Oct. 1981, Ranchers Exploration and Development Corp. began producing silver bullion from the Escalante mine and mill complex, located in southwestern Utah. Current in-place reserves are estimated at 2.42 Mt (2.67 million st) of ore, containing about 936 t (33 million oz) of silver at an average grade of 428.5 g/t (12.5 oz/st). The vein-type deposit is being mined underground through a decline that is currently 864 m (2,835 ft) in length, but will ultimately be at least 1.5 km (5,100 ft) long. The mine is completely mechanized with rubber-tired equipment, and is producing 680 t/d (750 stpd) of ore, five days a week, or 177 kt/a (195,000 stpy). Additional capacity is available. The cyanide leach mill and associated refinery are presently producing 4.35 t/month (140,000 oz/month) of silver bullion-an an¬nual rate of about 52.25 t (1.68 million oz). With minor modifications, the mill can produce up to about 70 t/a (2.25 million oz/year), and expansion is currently underway. History The Escalante property is located 68 km (42 miles) west of Cedar City, UT, on the west side of the Escalante Valley, where the vein forms a gentle ridge in an area of low, rolling hills. For years, the vein has been the object of considerable exploration, but never became more than a sporadic producer, primarily due to low silver prices. Heber Holt of Enterprise, UT, staked the original four claims in 1896; they were patented in 1910. During the next 48 years, limited exploration and mining activity was conducted on the property. Systematic evaluation and development did not, however, begin until March 1958, when Samuel S. Arentz, a prominent mining engineer and consultant, formed several joint ventures with mining and oil companies that conducted drilling, drifting, mining, and water drawdown tests on the property. However, it remained uneconomic, principally because of low silver prices and costs for pumping large flows of underground water. In 1975, Ranchers obtained an option on the property and in 1979 began a drilling program. As of May 1982, the company had drilled 70 core holes, bringing the number of exploratory holes drilled on the property to 138. Test mining began in 1979 as silver prices increased, and full mine development began in 1980. Mill construction began in Sept. 1980, and on Aug 29, 1981, the first ore was fed to the mill.

Jan 9, 1982

By Michael J. Brnich

On November 20, 1968, a massive explosion rocked the underground workings of Mountaineer Coal Co.?s Farmington No. 9 Mine in West Virginia. Of the 99 miners who were working in the mine at the time of the explosion, only 21 survived and escaped the mine. This group included eight who were rescued from the Mahan?s Run air shaft. Nearly 40 years after the event, researchers from the NIOSH Pittsburgh Research Laboratory conducted oral history interviews with two of the eight survivors rescued from the shaft. The Farmington No. 9 Mine disaster ultimately led to passage of the Federal Coal Mine Health and Safety Act of 1969 (amended in 1977).

May 1, 2009

By T. Marcher, C. Mathiesen, M. Allende, S. Bauer

"A unique pumped hydro storage facility using the ocean as a lower reservoir, combined with solar PV to create consistent, clean power will be presented: the Espejo de Tarapacá Project is comprised of a 300 MW seawater pumped storage hydroelectric plant using the Pacific Ocean as its lower reservoir and an existing natural concavity at the desert as its upper reservoir. The plant site is located in Chile’s northern coast 90 km south of Iquique. The site is characterized by a rocky shoreline and about 600 m of flat terrain moving inland, with an abundance of rock outcrops, after which there is a steep 700 m cliff. The power house and all waterways will be underground. The main focus is to present the rocks being expected in the underground works. As one of the actual most tectonically active regions of the world the seismic activity is particularly relevant and will be outlined in the presentation. INTRODUCTION Valhalla Energy is an independent Chilean-owned power development company. It focuses on the development, ownership and operation of renewable power projects. Valhalla was founded in 2011 with the goal of developing Chile’s natural renewable energy resources and strategically diversifies the country’s energy matrix away from an overdependence on imported fossil fuels. Valhalla began developing pumped storage hydro projects to provide scalable, clean, competitive, and reliable electricity by combining Chile’s superior solar resources with the country’s unique and extensive coastline suitable for storage.The capacity for renewable energy supply is driven by two distinct and unique natural characteristics found in northern Chile: (1) the abundant and reliable solar irradiation in the Atacama Desert and (2) a coastal site that benefits from a steep cliff and a natural concavity both within a relatively small land mass (see Figure 1). There are several potential sites in the northern part of the country that can be developed. The “Espejo de Tarapacá Project” is the first one to be built and subject of the present paper."

Jan 1, 2016

By N. S. Dalal, Xianglin Shi

"Electron spin resonance (ESR) measurements provide direct evidence for the involvement of Cr(V) in the reduction of Cr(VI)· by NAD(P)H. Addition of hydrogen peroxide (H2 O 2) to NAD(P)H-Cr(VI) reaction mixtures suppresses the Cr(V) signal and generates hydroxyl (·OH) radicals (as detected via spin trapping), suggesting that Cr(V) reacts with H2O 2 to generate the ·OH radicals. Reaction between H2O 2 and a Cr(V)·glutathione complex, and between H2O 2 and several Cr(V)-carboxylato complexes also produces ·OH radicals. These results suggest that Cr(V) complexes catalyze the generation of ·OH radicals from H2O 2, and that ·OH radicals might play a significant role in the mechanism of Cr(VI) cytotoxicity. KEY WORDS: ESR. spin trapping, Cr(VI) reduction, Cr(V), hydrogen peroxide, free radicals.INTRODUCTIONThis communication reports an ESR spin trapping detection of hydroxyl ( OH) radicals.in reactions between some Cr(V) complexes containing biologically important ligands and hydrogen peroxide (H2O 2 ). This work was undertaken because while the reduction of Cr(VI) to lower oxidation states has been suggested as a key step in the mechanism of Cr(VI) toxicity, the reaction· mechanism is not yet clear. 1 Mutagencity has been well documented for Cr(VI) via various bacterial assays, while Cr(III) has been shown not to be mutagenic.2 • 3 Since it has been reported that compounds containing Cr(VI) do not react with isolated DNA,4 the reduction of Cr(VI) by other cellular constituents has been thought to be important in the mechanism of Cr(VI) induced DNA alteration.1·4 • 5 For cellular systems earlier studies include those on the reduction of C~(VI) by microsomes,6-8 rat liver DT-diaphorase,9 and aldehyde oxidase. 10 Regarding the reduction mechanism, Jennette used ESR spectroscopy to show that a long-lived Cr(V) complex is formed as an intermediate in the microsomal reduction of Cr(VI) in the presence of NADPH.8 She postulated that Cr(V) is the ""ultimate"" carcinogenic form of chromium compounds. This conclusion has led to many further investigations of the formation of Cr(V) in the reduction of Cr(VI) under biologically relevant conditions.11 - 19 More recently, however, it has been suggested that oxygen-derived radicals generated during the Cr(VI) reduction are the species responsible for the DNA alteration.20.2• To the best of our knowledge, however, no information is available on the generation of such radicals in the reduction of Cr(VI) under biologically relevant conditions, except some preliminary results on the glutathionyl (GS·) radical formation in the reduction of Cr(VI) by glutathione (GSH). 11 - 19 We, therefore, undertook a systematic investigation of the reaction of Cr(VI) with NAD(P)H, GSH, ix-hydroxycarboxylic acids, and H2O 2 • NADPH was chosen as a model reductant because of its ubiquitous existence inside the cells, its critical role in the enzymatic Cr(VI) reduction,1·6-9 its representation of important cellular Cr(VI) reductants, and its ability to reduce other metal ions.22 GSH was chosen as another model Cr(VI) reductant because GSH also exists inside cells, it represents another important category of cellular Cr(VI) reductants, the thiols, and it also plays an important role in the Cr(VI) toxicity .1• 1 ""- 19.i3.i4 For further clarification, we also studied the reaction of Cr(VI) with several '1'.-hydroxycarboxylic acids in the presence of H2O 2 since these acids are definitively known to reduce Cr(VJ) to form stable, isolable Cr(V).25 .2 6 The results obtained indicate that Cr(V) complexes, produced in the reduction of Cr(VJ) by cellular reductants, react with H2 O 2 to generate ·OH radicals, which might be the initiators of primary events in Cr(VI) carcinogenicity."

Jan 1, 1990