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By Gheorghe Vieru

Security and safety due to environmental impact as well as the radiological consequences during the uranium mining operations, tailings management, uranium processing, disposal of waste in conventional landfill sites are matters of great importance. The Uranium National Company (CNU) from Romania is responsible for all aspects belonging to the management of the entire Romanian uranium industry- the uranium ore extraction, transport and processing of uranium ore, concentrates processing, as well as disposal of sterile ore and waste. The paper will presents specific safety problems related to the identification and evaluation of potential environmental risks, as well as possible radiological consequences associated with the disposal of sterile and the uranium processing waste resulting from processing of the uranium ore. Computer codes will be used, such as IAEA INTERTRAN II and RADTRAN 5. It is also to be noted that this paper considers the main results of the scientific research carried out by the main author as CSI (Chief Scientific Investigator) for Romanian Research Contract on NORM concluded with IAEA Vienna.

Aug 1, 2010

By M. Scobie, T. Atkinson

"This paper reviews the development of new designs in extensible and high angle conveyor systems. These aim to overcome the limitations of prior alternative concepts in design. The application of such systems in strip, terrace, open pit and mountain mining is reviewed. IntroductionTruck haulage costs have tended to escalate in recent years. This has been primarily due to operations generally moving to greater depths with associated increases in haul distances . Periods of high inflation rates have also been experienced for diesel fuel oil, tires and other petroleum based products. Recent international political events have tended to regenerate concerns over future oil supply and price stability. For such reasons, conveyor based transport is becoming increasingly attractive. Truck haulage maintains an inherent flexibility and improvements continue to be made in performance and capacity. Doubts must exist, however, over the extent to which further economies of scale may be made. Conversely, belt conveyor systems do not suffer this constraint and have the following advantages:• Electrical power is used and the specific energy consumption is at least half that required for truck haulage.• Operating costs and skilled labour requirements are lower.• Equipment has superior longevity and is ""inflation proof"" .• Access roads can be steeper and narrower in most mine environments, reducing construction and maintenance costs.• They are less prone to breakdown and bad weather delays .• In long haul, high capacity operations conveyors can save substantially on capital cost.• Environmental impact is improved with reduced noise level, dust and atmospheric pollution. Although conveyor systems are less flexible in operation than truck haulage and although a breakdown in any part of the system can immobilize the total system, mechanical availabilities of + 80% are constantly reported by large operators. There would appear in the past to have been some prejudice against conveyor systems in hard rock mines due to lack of experience. Apparent reservations would apply equally 10 underground coal mines, yet practically all of these mines (and some underground hard rock mines) find conveyor systems more economical than other transport systems."

Jan 1, 1991

By L. M. Ame, W. D. Harwood

"This paper outlines a management philosophy aimed at promoting employee involvement, quality and process improvement at Inco 's Thompson operations. It describes the use of statistical process control techniques, lessons learned and examples of progress.IntroductionThis paper provides an overview of the Manitoba Division's performance through the promotion of greater employee involvement, quality and process improvement. Having learned from other practitioners o f quality management, the Manitoba Division believes its experiences are applicable to all mining and other businesses.The Thompson operation consists of two underground mines, an open pit, a mill, a smelter and an electrolytic refinery. The workforce consists of 2000 members. The main products are electrolytic nickel slab and proprietary nickel rounds. Production levels are currently at capacity in response to heavy market demand.Paralleling much of the mining industry the corporation was faced with six years of decreasing nickel prices (Fig. I). Inco Limited survived by focusing on productivity and cost improvement. Manitoba Division productivity improved 32070 over three years beginning in 1982-the worst financial year in the company's history (Fig. 2). A real unit cost reduction of 20%, net of inflation, was also achieved (Fig . 3)."

Jan 1, 1990

By Grant L. Anderson, Richard C. Rice, Richard L. Jentgen

"Data for underground mine-hoist ropes determined in the Ontario Special Rope Tests were obtained, encoded and analyzed statistically. Prior 10 refined statistical analyses, these data were subjected la characterization studies and preliminary analyses to allow trends to emerge that could be used to guide and facilitate the refined analysis. The data were characterized by determining distribution s for a wide range of variables including remaining strength, service life in terms of lime and hoisting cycles, outer-wire torsion values, elongation during tensile testing, diameter reduction, location of strength loss and the strength lasses associated with corrosion rating and lubrication rating , This paper describes the more important relationships between remaining strength (or, conversely, strength loss) as the dependent variable and some of the principal independent variables mentioned above.IntroductionBoth productivity and safety in underground mines could be improved if mine-heist rope Iife and reliability could be predicted more accurately . As a result, hoist-rope failure processes and their effects on rope life and remaining strength need to be quantified and related in such a way that improved retirement criteria can be developed. This is true whether the failure is incipient or actual or whether the failure mode is by corrosion , wear, fatigue or a combination of these factors."

Jan 1, 1984

By E. G. Parker

"Sherritt's zinc pressure leaching process converts zinc sulphide concentrates directly to zinc sulphate solutions and elemental sulphur. Thus, one pressure process step replaces both the roasting and leaching operations of the conventional roast-leach route. In addition, high single-pass extractions eliminate the need for residue treatments to recover unleached zinc. Because pressure leaching produces elemental sulphur, rather than sulphur dioxide, acid plants and smoke stacks are not required, and air pollution control and work-place hygiene are greatly improved. .In 1977, Cominco Ltd. and Sherritt Gordon Mines Limited jointly operated a three-tonne-per-day pilot plant to demonstrate pressure oxidative leaching of Sullivan zinc concentrate and the subsequent separation of elemental sulphur. The process consisted of regrinding the concentrate, continuous leaching at 150°C at elevated oxygen pressures in a four compartment autoclave and the subsequent recovery of elemental sulphur, either in the molten liquid form from a decantation autoclave or as a flotation concentrate. Of the zinc contained in the concentrate, 97% was extracted in 90 minutes, and 96% of the sulphur was converted to the elemental form.Following the successful pilot campaign, Cominco began building the world's first commercial zinc pressure leaching plant. This plant, which was in operation by late 1980, will eventually treat about 25% of Cominco's planned zinc capacity of270,000 tonnes per year.This paper describes the general process principles, the results obtained from the pilot plant and the integration of the process into Cominco's operations at Trail. The application of pressure leaching to a ""grass-roots"" plant is also discussed, and compared with conventional roast-leaching."

Jan 1, 1981

?NWCC has the highest number of Aboriginal students of any post secondary institution in BC and the region served includes 25 bands ? Chair of the Board of Governors is Irene Seguin (Hagwiloo K?am Saxwhl Giis) from Gitwinksihlkw ? FN council ? 39 First Nations Members * focus is to develop policy recommendations to increase student success rates

May 1, 2009

By Richard S. Allen

"The casual visitor is not apt to think of the Adirondacks as a one-time hive of mining and manufacturing activity. However, where there are mountains there are usually minerals and northern New York State is no exception.The Adirondacks are a rocky shield, a great stone cap pulled down over what is now northern New York. The bedrock consists of layered metamorphic rocks which were once sandstones or limestones on the bottom of a shallow sea that covered the region 1000 million years ago. The highlands are composed for the most part of the igneous rock anorthosite. Ancient earth upheavals at temperatures of at least 750°C mixed molten masses of anorthosite and the minerals it contained with the older metamorphic rock, resulting in deposits of iron-titanium oxide s, red garnet and other valuable minerals. Of these, the most readily recognizable was iron.The first hint of the existence of iron ore in the Adirondack Lake Champlain region of upper New York State seems to have come from a Swedish naturalist, Peter Kalm (1716-1769), who travelled through French Canada and visited the military outpost of Fort St. Frederic in 1749. In July of that year, Kalm wrote:""Among the kinds of sand which are found on the shores of Lake Champlain; one is black and the other garnet-colored... and they sparkle when the sun shines. All the grains of this sand without exception are attracted to the magnet, the uppermost or black sand being about a quarter inch deep...""Concerned primarily with the fur trade, the officers and men who occupied this remote bastion of La Belle France were apparently unaware of the industrial and commercial possibilities beneath their feet. No deposit of iron was then known to exist any closer than the Three River s area in Lower Canada."

Jan 1, 1983

By D. Laguitton

"Mathematics, process theory, process practice and computer applications are the main disciplines that contribute to developing useful techniques for computer simulation of mineral and coal processing plants. As in any multidisciplinary effort, communication or transfer mechanisms must be developed to facilitate the flow of experience between participants of different backgrounds. These mechanisms include written reports, verbal communications, workshops and transfer of computer programs. The SPOC project at CANMET is devoted to computer simulation and as such has addressed, or will address in the near future, problems inherent to methodology transfer. The first major output of the project was the material balance program, MATBAL2, which has been acquired by over 30 organizations. Program documentation, industrial workshops and summer student programs have been used to effect the transfer. This experience is discussed and the future outlined.IntroductionComputer simulation has become a common tool in many different fields of human activity during the past two decades, as illustrated in Figure 1. The total number of articles abstracted in Chemical Abstracts under the general subject entry of “Simulation"" has been following a pseudo-exponential growth since 1972 and was approaching 5000 in 1980, whereas no such entry was even used prior to 1967. This represents over a dozen papers published daily on the subject and should continue to grow to higher figures. Still, progress toward accepting modelling and simulation in mineral and coal processing has been very slow. It will be shown later that this slow acceptance is a cause rather than a consequence of the limited success of the various attempts made so far to draw unambiguous benefits from simulation applications. The real cause of the difficulties in fully accepting the new methodology lies in the multidisciplinary aspect of modelling and simulation, which does not suit the traditionally conservative approach that prevails in designing and operating large and costly processing plants."

Jan 1, 1982

By W. H. Hodgson, A. R. Preston

"Improved rail production techniques provide new options for the rail user. Steelmaking improvements offer tighter composition control, lower oxide and sulphide counts, greater control of segregates and freedom from hydrogen problem s. New ultrasonic, laser and eddy current equipment gives printout information on surf ace flatness, straightness and internal condition. These have come along at a time when dramatic changes have occurred on the rail heat treatment scene. Rails can now be deep hardened on or offline in ways which should eventually result in a complete rewrite of the world's specifications. Rails of simple composition can be produced in the hardness range 2801400 BHN as required. The rail user can choose the hardness within this range according to requirement without the necessity for any step changes in the process routes.It is suggested that this is the pattern f or the next decade.IntroductionRails have been the subject of very slow improvement over many years but developments gathered momentum in the early seventies. Recent improvements in quality and properties have provided dramatic increases in rail life under the more severe service situations. Rail profile grinding, lubrication and other track improvements have greatly added to expectations of even longer life. All of this, coupled to even newer mill heat treatment developments, tilt both technical and economic advantages away from tradition to the point where specifications will need to be rewritten so that railroads can take full advantage of these new products."

Jan 1, 1988

By George J. Cymerman

Since 1978, Syncrude Canada Ltd. has been expanding steadily its oil sand mining and processing capacity while reducing unit energy requirements. At the current rate of ~180 M tonne/year oil sand, the originally adopted Karl Clark?s 80°C version of the Hot Water process would require some 53 PJ (53 x 1015 Joule) heat. If this amount of heat were to be derived from burning natural gas it would cost $369 M/y (at $7/GJ). Fortunately, effective recovery of waste heat from the upgrading operations at the Mildred Lake site obviated the need for water heating with natural gas. The oil sand hydrotransport technology, first utilized commercially in the mid-nineties at Syncrude?s North Mine, reduced slurry temperature from ~80°C to ~50°C, cutting the unit heat requirement from 293 MJ/tonne to 183 MJ/t. However, in the new 100 Mt/year Aurora Mine even a 50°C process temperature would still require 18 PJ of heat energy per year. Only limited quantity of 65°C water could be imported from Mildred Lake site and some waste heat would be available from Gas Turbine Generators. A new, Low Energy Extraction (LEE) process was developed to minimize heat requirements by further reducing process temperatures to 25°C in the slurry pipeline and 35°C in the Primary Separation Vessels (PSV). Unfortunately, when applied to certain ore facies in Aurora, the LEE process yielded disappointing bitumen recoveries, necessitating an increase in slurry temperatures from 25°C to 35°C in the pipeline and from 35°C to 42°C in Primary Separation. In 2004, an Optimized Low Energy process (OLE) was developed and piloted at Syncrude Research using a 2000 kg/hour pilot plant. In the OLE process, most available heat is applied up-front to produce 45°C pipeline slurry at a density of 1.58 kg/l. Once the pipeline conditioning process is completed, the slurry is flooded with cold (10°C) water, resulting in PSV temperature of 34°C. The overall heat and water requirements are the same, or slightly lower, compared to those of the LEE process ? but without the penalty in bitumen recovery. Processing 100 Mt oil sand at 34°C (96 MJ/t), rather than at 50°C (183 MJ/t), will save $61 M/y (@ $7/GJ) and reduce green house gas emissions by ~47 %. The OLE process is currently being implemented at the Syncrude Aurora Mine.

May 1, 2006

By M. J. A. Ruszala

Aggregates production is a huge global industry which uses an enormous amount of energy and produces a massive amount of unsalable fines. Reducing the amount of energy used per tonne of product and/or the amount of fines produced, would make a quarry more efficient. This reduction would make the quarry more environmentally friendly and profitable. This research looks at modelling Mountsorrel Quarry, a granite quarry in the United Kingdom (UK), using JKSimMet and Split-Desktop software packages in conjunction with the European Union (EU) project, EE-Quarry. Samples submitted to drop weight tests confirmed Mountsorrel Quarry granite as an extremely hard granite. Rock fracture data (t10) and energy of comminution (ECS) data were obtained from analysing the results. Split-Desktop image analysis software was utilized to determine the particle size distribution (PSD) of the primary crusher feed, as it contains particles too large to screen manually. It was also found that <1% of the feed is fines, which at Mountsorrel Quarry are classed as particles smaller than 5 mm, and that no particles were larger than 3,810 mm. JKSimMet was used to create a flowsheet of Mountsorrel Quarry. The crusher product PSDs were simulated and found to have strong correlations with experimental data, calculated by screening samples from conveyor belts, especially in the fines region, with a mean difference of 1%. The simulated primary crusher product PSD showed that it contains ~6% fines. A simulation over the entire quarry showed the product to be within the size range produced at Mountsorrel Quarry, and with a simulated fines content of 13%. When the CSS on the primary crusher was altered from 165.1 mm (the operating size on site) to 100.0 mm, it increased the overall percentage of fines produced by 3%, increased the power draw by 140.6 kW, but reduced the overall plant production percentage of fines by 2%. Two blasts were analysed on adjacent rock faces. They had identical blast designs, but the order of deck detonation varied; the first blast detonated the bottom deck before the top and vice versa in the second blast. For each blast, measurements of the feed PSD to the primary crusher, the number of particles that required secondary breakage on the quarry floor, acoustic levels and vibration readings were measured. No significant difference was identified between the two blasts in any of the parameters measured. In conclusion, a working model of Mountsorrel Quarry has been made in JKSimMet that has been validated against data from site and Split-Desktop has been used to simulate the primary crusher feed PSD, something that was previously unknown. The effect of reversing the order of deck detonation in a two deck blast was also analysed but with no significant difference between the two blasts found.

Aug 1, 2013

By W. Evans, C. E. Ells

Nuclear power reactors using zirconium alloy pressure tubes generate electricity in several countries. Such reactors are particularly important in Ontario, where CANDUs* generate about 30% of the total electricity produced in the Province. Starting with the commitment of NPD-2 in 1956, the pressure tubes of the first five CANDU reactors were made of coldworked Zircaloy-Z, an alloy of Zr and Sn. This alloy was developed by the US Navy, but the decision to use it in a cold-worked condition was based on AECL work. In 1958, the USSR published information on a new alloy, Zr-2.5 wt% Nb. The Nb promotes stabilization of the (3-phase in the material, thus presenting opportunities of exploiting metallurgically strong pressure tubes analogous to the heat-treatable cx-{3 titanium alloys. After construction of two reactors using Zr-2.5 wt% Nb in a quenched and aged condition, an extensive development program on cold-worked Zr-2.5 wt% Nb pressure tubes resulted in them becoming the reference tubes for all CANDU reactors committed since 1966. Anticipating the future needs of the domestic and export markets, AECL have pressure tubes of Zr-3.3 wt% Sn-0.8 wt% Nb-0.8 wt% Mo (Excel) in an advanced state of development. These tubes will be used in an annealed condition; our projections show that they will have improved dimensional stability over the lifetime of the reactors. These improvements result from experimental programs leading to an understanding of the relationship between microstructures and fabrication variables and effects of the environment during service in nuclear reactors.

Jan 1, 1981

By D. Kershaw

"A world-scale surface mining operation is associated with the Syncrude Oils ands Plant. Each day over 300 000tonnes of oils and are mined and transported to the process plant to produce 129 000 barrels of synthetic crude oil.Examples of research and maintenance engineering programs which have resulted in substantial gains in dragline and bucket wheel conveyor system productivities are discussed. Two central themes within these programs, which go beyond the usual technical support associated with a large surface mining operation, are pursued:1. the approach taken to determine the causes of component failures and provide Syncrude performance specifications to allow manufacturing industry to respond with more appropriate products; and2. systems and equipment studies which have led to higher productivity in the major mining equipment and the development of an auxiliary feed system.IntroductionA world-scale open pit mining operation is associated with the Syncrude Oils ands Plant located near Fort McMurray in northern Alberta. Over 300 000 tonnes per day of oils and are mined and transported to the process plant. Fifty million barrel s of synthetic crude oil were produced in 1987, which represents 10010 of Canada&apos;s crude oil requirement.following tree clearing and surface drainage, overburden is removed by mobile equipment ahead of oils and mining. Draglines excavate the 40 m depth of feed grad e oils and which is windrowed on the dragline bench. Bucketwheels reclaim the oils and from the windrows for transport by conveyor systems to the extraction plant surge pile.The Syncrude mine is operated in four essentially equal quadrants, each serviced by a dragline and a bucketwheel conveyor system. The mining face in each quadrant is approximately 2 km long and reclaimed oils and is transported by 1830 mm shift able conveyors over distances up to 6 km. Individual conveyors vary in length up to 2500 m.The Syncrude plant started operating in late 1978, and Figure I shows the mine production history through to the end o f 1987. Annual production volumes have increased from 50 million tonnes of oils and in 1979 to 105 million tonnes in 1987.The period from 1982has seen a change in operating philosophy, away from striving for very high production rates, to operating at sustained targetted levels within the measured capacity of the equipment. Higher over-all production volumes have resulted from being able to operate for more hours at these rates. This same period has also seen much greater emphasis placed on routine inspection of the equipment and planned preventive maintenance to avoid problems which could otherwise impact on production."

Jan 1, 1990

By J. W. Hendry

"This paper will discuss the application of tools and the evolution of computer-assisted procedures in the production planning process at Quintett e Coal Limited (QCL). In 1986, QCL produced 5.3 Mt of clean coal from their surface mining operation located in north eastern British Columbia. The structural complexity of the sedimentary deposit and high rate of mining necessitate the consideration of large amounts of geological information which continually updates the interpretation. There are multiple unit operations required during the process of mining through a given multi-seam sequence, which results in many interdependent faces, and multiple iterations of scheduling sequences in order to satisfy a given set of objectives. In order to facilitate these activities in a timely fashion, it was recognized that a computer systems&apos; capability needed to be developed which could increase the efficiency of information input, manipulation and output. IntroductionQuintette Coal Limited (QCL) has been operating a large metallurgical open pit coal mine in northeastern British Columbia, since 1982. The mine produced 5.3 Mt of clean coal in 1986 for export to Japan. Throughout the start-up period and the subsequent build -up of production levels, it became evident that the primary producing area was comprised of extremely complex faulted structures. This has resulted in development and modification of specialized mining methods employed to effectively recover the resource. Similarly, the planning and engineering techniques employed have been evolved over the same period of time. The implementation of computerized methods has been one of the major developments in this process, including geology interpretation, modelling, reserve definition, quantification, production planning and scheduling, and graphical plan presentation. These capabilities have been employed, in various forms, for project scale feasibility work and long range planning for some time, however, the use of computer tools for short-term, detailed production planning of a complex mining environment presents a different set of problems. It is hoped that a presentation of the current state of evolution and future plan s for development will be of interest to organizations considering implementation of a similar system."

Jan 1, 1988

By Jean-Yve Tremblay, Michel Prud'homme

"Industrial minerals include a group of more than fifty minerals which are marketed into almost all the sectors of industry; they are the backbone of many manufacturing industries. Table I shows major end-uses for industrial minerals in manufacturing sectors. At Energy, Mines and Resources, industrial minerals are divided in three major categories: (I) agro chemicals and chemicals, (2) construction mineral s, and (3) ceramics and specialty minerals. A listing of the major groups of minerals is shown in Table 2. Agro-chemicals and chemicals are sold on the basis of their chemical content and purity. Construction minerals or structural minerals are distinguished by their performance as low cost and bulky commodities. Ceramics and specialty minerals are performance-specific and are sold for their property on imparting functions on end-products. Industrial minerals have unique characteristics that are useful in many stages of processing; from crushed size to micronized fillers a single mineral ca n serve a broad range of industries because of its intrinsic properties."

Jan 1, 1988

By K. R. Wood, G. W. McDonald

"The tailings disposal system at Les Mines Selbaie includes dewatering of tailings in a high-capacity thickener, followed by point discharge of the thickened solids to form a stable conical pile. Tailings water drains to ponds formed behind engineered dams, prior to either recycling f or process use or discharge to the environment. Design and economic considerations of the system are discussed. Construction, start-up and operating experiences are also presented.Introduction Les Mines Selbaie is located in the Abitibi region of northwestern Quebec, approximately 700 km north of Toronto and 150km south of James Bay. More locally, the Detour gold mine is 60 km to the west while the Noranda smelter is 220 km to the south.The deposit was discovered as a result of a Questor INPUT Mark VI geophysical survey in 1973, followed by diamond drill programs from 1974 to 1976. Three mineralized zones were delineated and underground exploration was carried out on all three. A production decision for the &apos;B-zone&apos; copper-gold-silver orebody was made in July 1979. The underground operation started in July 1981, with full production of 1500 t/d being achieved in May 1982.During the planning phase, every effort was made to ensure that the operation would be environmentally sound . The design included the provisions of the then newly proposed provincial environmental guidelines. The tailings disposal system formed the most significant part of the environmental program due to the large volumes of solids and water effluent. In addition, the design allowed for future expansion of the system to accommodate mining of the other zones, thus minimizing future costs and disruptions."

Jan 1, 1986

By V. S. Sastri, G. R. Doey, R. W. Revie

"Different forms of corrosion, the various corrosive environments encountered, the mining equipment subject to corrosion and the methods to control corrosion in the mining industry are briefly reviewed along with the savings that could be achieved by corrosion control. IntroductionCorrosive conditions in mines and metallurgical plants, lead to deterioration and wastage of equipment and of materials. The cost of corrosion in the mining industry can be significant, and measures to minimize corrosion must be taken to reduce this cost(l-3). Although the data in Table I are twenty years old they indicate the significance of corrosion costs in four industrialized countries. The costs of corrosion in the U.S. metallic ores sector and in the Canadian mining industry are presented in Tables 2 and 3, respectively. Significant savings in the mining industry can be achieved by using corrosion control methods. For example, corrosion in the Canadian mining industry in 1991 cost $1460 million of which $97 million was avoidable. Indirect costs of corrosion associated with plant shutdown, lowered efficiency of equipment and overdesign are additional to the direct costs cited here."

Jan 1, 1994

By E. E. Mueser

As Mr. Lundberg has already ably covered the theory of various methods of electrical prospecting, I shall confine my remarks to a consideration of the features which must obtain in an electrical prospecting method in order that it may be useful from a practical standpoint. These remarks I shall make with particular reference to the Elbof method. The successful application of all these methods rests, in the first place, upon the possibility of correlating theory, or empirically established facts, with the field data. Their practical usefulness, however, requires that the technique of making the field observations, and the procedure itself, be such that the method may be applied to large areas, under normal average conditions. The method, therefore, should not involve excessive preliminary labour costs to prepare the ground for actual prospecting work, nor should the prospecting work itself be so slow that its cost, when applied to extensive areas, becomes prohibitive. Moreover, it should be possible to apply the method even under difficult terrain conditions, such as rough topography and dense vegetation. It may be said of most of the methods referred to in the preceding paper, that, while they are interesting and theoretically sound, they fail to meet such practical requirements as I have outlined.

Jan 1, 1926

By J. R. MacDonald

MINING literature contains very few descriptions of operations producing as little as 25 to 30 tons of ore per day. The purpose of this paper is to discuss the gradual development of a mining method for such a small-scale operation at the No. 2 mine of Central Patricia Gold Mines, Limited, and in doing so to review several systems of stoping applicable to narrow ve1ns. MAIN ECONOMIC FACTORS TO BE CONSIDERED (1) Overhead.-The outstanding feature of most mines operating on a single narrow vein is chat of small daily tonnage. The reason for this low output can be readily understood. The strictly limited ore-reserves present a condition unfavourable for a policy of large initial expenditures, with the result that the capacity of the plant provided must be governed by the? amount of ore in sight at the time when mill construction is planned. This is immediately reflected in the cost per ton, there being relatively few tons over which to distributed the more or less static charges, such as hoisting, heating, supervision, administration, pre-production expenses, and other write-offs. (2) Development.-In mining this type of orebody, the main factor contributing to high costs is unquestionably the small tonnage of ore made available by a given amount of development. Thus, for example, from the data tabulated below it can be seen chat, assuming a 12-in. vein and a drifting cost of $9.00 per foot, the development charge for this item alone would be 71 cents per ton. Add to this the charges for raising, cross-cutting, shaft-sinking, and pumping, besides charges arising from development in waste, and the figure will be very considerably higher than 71 cents.

Jan 1, 1941

By S. Amira

In the last two decades, many new creep-resistant magnesium alloys have been developed for high temperatures applications. Their mechanical performance and corrosion behaviour were reported for various experimental conditions. However, these conditions often led to uneven comparison basis. In the present study the microstructure, mechanical properties and corrosion performance of four of these newly developed creep-resistant magnesium alloys were systematically compared. Specimens were obtained from experimental box-like components that were die-cast and thixocast in comparable conditions. Their mechanical and corrosion properties were compared using similar testing conditions. Results show that the creep resistance, strength and impact resistance of specimens are comparable but systematically lower compared to specimens cast under optimized conditions. The reduced concentration of elements such as Al, Ca, Sr and Ce lead to a decrease of the corrosion resistance of the magnesium alloys in 3.5% NaCI solution.

Jan 1, 2007