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By N. Watson

Historically the insurance industry's involvement in any project has been relatively late in the process. Often it was a case of the last item to be ticked off the checklist has been to ensure that the insurance is in place. However, in more recent times insurers have imposed more restrictions on the cover they are prepared to provide, which has in some cases necessitated a change in the contracting structure to accommodate the insurance policy(ies). In addition, changing contractual practices have changed the allocation of risk between the various parties involved. This calls for a more proactive approach to the design and implementation of an insurance program for both the construction and operational phases of any resource project. This paper explores how a risk managed approach to the design and implementation of an insurance program for a resource project can align itself with current management approaches to project development. From the authors' experience, this approach is best adopted early on in the project (often in conjunction with the bankable feasibility study) and follows AZ/NZS4360 to objectively examine and compare a wide range of risk exposures of the project in a time-effective manner across the following areas: ? personnel; ? environment; ? general management; ? compliance - legislation, systems, protocols; ? asset management; ? change management; ? financial impacts to the organisation; ? products/services; ? service delivery; and ? technology. Having identified and then analysed the risk exposures according to common consequence and likelihood ratings the next step is to develop a risk map of all considered exposures. The true value of this approach lies in the development and implementation of a risk treatment plan for identified exposures where the exposure is unacceptable. The plans will lead to the optimal solution to the appropriate risk prevention, risk mitigation and risk transfer options available. This paper also examines other benefits to the project that may arise from adopting a risk managed approach in addition to the ability to design an insurance program which recognises the exposures and the ability of the organisation (and other project parties) to retain risk.

Jan 1, 2007

By T. L. Joseph

BLAST furnaces are most efficient thermally when the C02 in the top gas is highest. Oxygen introduced in the air blast is converted to CO in the combustion zones. The extent to which CO, generated in front of the tuyères, is converted later to C02 depends upon the ratio of ore to coke in the charge and the degree to which C02, formed by reduction of iron oxides with CO, reverts to CO by the secondary reaction C + C02 = 2C0. About 300 to 400 lb. of carbon1 per ton of pig iron is normally involved in the solution-loss reaction or direct reduction of FeO with carbon, which produces the same over-all results; that is, lower C02 in the top gas. Riche has recently reported a reduction in fuel consumption at slower rates of blowing on two furnaces in spite of higher heat losses per ton of iron. Lower fuel consumption at slow operating rates was due to more complete reduction of the ore that resulted in higher C02 in the top gas and consequently more efficient use of carbon. Kinney3 has reported substantial savings in fuel as a result of crushing and sizing the ore charge. Improvements in practice brought about by sintering magnetite concentrates, flue dust and fine ores have been due to the establishment of conditions favoring more complete reduction of the ore in the upper part of the furnace. The extent to which oxides and fluctuations in composition in pig iron affect the quality of steel and finished product needs further study. There is evidence that more thorough preheating and reduction of the ore in the upper part of the furnace tend to give a better quality of iron. Bogatzkii4 found from laboratory work that the amount of oxygen enter-

Jan 1, 1936

By J. Eldridge, K. L. Komarek

Activities of aluminum in solid Fe-Al alloys have been determined between 0 and 75 at, pct Al and 1100" and 1400°K by an isopiestic method in which iron specimens, heated in a temperature gradient, are equilibrated in a closed all-ceramic system with aluminum vapor. The activity of aluminum in these alloys shows a strong negative deviation from Raoult's law at low concentrations but increases rapidly above 40 at. pct Al. The enthalpy and entropy of mixing me both negative. For an alloy with equiatomic composition the values are: HM = -7300 cal and SM = -0.85 eu. Sodium chloride has been added at lower temperatures to accelerate the evaporation of aluminum. Equations have been derived to calculate activities of aluminum from experimental data. THE Fe-Al system has been the object of a great number of investigations.' Most of these studies have been concerned with the phase diagram and specifically with the order-disorder reactions in the range of solid solutions of aluminum in iron. The results have been compiled by Hansen2 and presented as a complete phase diagram, Fig. 1. More recently, Taylor and ones' have found that both ordered and disordered alloys can exist in the a field up to the solidus curve separated by a line starting at 18.75 at. pct Al at room temperature up to 37 at. pct Al at 1375°C. Chipman and coworkers4-7 have studied repeatedly the activity of aluminum in liquid dilute Fe-Al alloys. They have measured the distribution equilibrium of aluminum between liquid iron and

Jan 1, 1964

By G. Sandoz, D. A. Meyn

The fracture surfaces of specimens of titanium a1loys which exhibited susceptibility to subcritical crack growth in a wide variety of environments, including aqueous solutions, alcohols, hydrocarbon gases, carbm tetrachloride, and dry air, were examined. The dominant and characteristic fracture mode was cleavage. which became mixed with an increasing porportion of ductile fracture modes (dimples. and so forth) as the applied KI was increased. The cleavage plane in all the alloys was oriented at 15 deg from (0001) of the a phase. No indices could be assigned to the 15 deg cleavage Plane because of uncertainty as to which zone it belonged to. SLOW crack growth and delayed fracture take place in certain titanium alloys at stress intensity (KI) lower than the critical values for complete fracture (KIc) found in short-time tests for plane strain fracture toughness.' Such crack growth may take place in very dry air on sustained loading if the alloy contains a sufficient amount of hydrogen and if the stress intensity factor is higher than a threshold value designated KIH.2 Similarly, a number of environments such as water, alcohols, and hydrocarbons may cause slow crack growth provided the stress intensity factor exceeds the threshold value KISCC. In this paper it is intended to examine some fracto-graphic and crystallographic details of this subcritical crack propagation process as related to alloy composition, environment, and stress intensity. It has been previously reported that subcritical crack growth takes place in titanium alloys in aqueous environments by cleavage.2"6 The observations to be described here indicate that in the alloys investigated the mode of subcritical crack propagation is more dependent on the stress intensity during cracking than on the environment. The fracture mode is illustrated with photographs of the fracture surfaces at a wide range of magnifications. The crystallographic character of the cleavage mode is also presented and the results discussed. EXPERIMENTAL APPROACH The studies were made on four titanium alloys— Ti-8A1-1Mo-lV, Ti-5A1-2.5Sn, Ti-7Al-1Mo-lV, and Ti-0.350. Of these four alloys the first two were mill annealed and fine grained. The latter two were noncommercial and coarse grained, having been prepared for other experimental purposes. The crystallographic studies required a large-grain size. Consequently the fine-grained alloys were an- nealed in a vacuum at 1950°F and furnace cooled to produce samples for these studies. This treatment did not alter the microstructure significantly except for grain size. All the aluminum-containing alloys showed primary a with a network of ß-phase particles within the a grains; Figs. 1 and 2 show this microstructure for the specific case of fine-grained Ti-8A1-1Mo-1V. The cracks in the figures will be discussed later. Fractographic studies were made on all the alloys, but the electron fractographs displayed herein are from the Ti-8A1-1Mo-1V alloy in the fine-grained condition. Emphasis was placed on this commercial alloy because considerable information was available on the stress-corrosion cracking characteristics in a variety of environments. Sufficient supplementary studies of the alloy after the anneal to produce large grains were conducted to establish that the stress-corrosion cracking susceptibility and fractographic characteristics were not changed significantly. Thus it could be inferred that the crystallographic data obtained exclusively on large-grained specimens would apply also to fine-grained specimens. Fracture surfaces for study were obtained using precracked cantilever beam specimens loaded as described by Brown. The precracked section of a specimen was immersed in the environment of interest. Values of initial stress intensity factor Kli were chosen slightly higher than KISCC in order to obtain a fairly extensive region of slow crack growth. Fracture surfaces representative of a variety of stress intensity levels could then be examined because in the cantilever beam test KI increases as the crack propagates.

Jan 1, 1970

By James Humes

The active mines in the Park City district at the present time are the Silver King Coalition, Daly-Judge, Daly West, and Silver King Consolidated. Several other companies, such as the Daly, American Flag, Ontario, etc., are doing considerable development work. In the Silver King Coalition mines the ore is a replacement of a dark siliceous limestone bed, varying in .thickness from 18 in. to several feet. In places the ore has reached a thickness of 25 ft. This limestone bed lies within 100 ft. of the underlying Weber quartzite. There are other lime beds, similar in appearance to this one, in the Park City formation, which is approximately 700 ft. thick; but not one of them has been found to contain any traces of ore. Directly under and in contact with the ore-bearing bed is another, composed of gray lime well studded with dark concretionary nodules; and this one is an unfailing indication of the proximity of the ore-bearing bed. These ore deposits make out from or have connection with some one of the ore-bearing fissures, which were undoubtedly the channels for the circulation of mineral-bearing solutions. It is therefore proper to run prospecting drifts in the fissures, although they seldom contain much ore. As a general rule, drifting in the fissures is not costly. Mining and mucking cost from $2.50 to $4 per foot, and very little timber is required. There are instances, as in the Daly fissure in the Daly-Judge mine, where the expense of keeping drifts open in the fissure is so great that it has proved economical to make the drifts in the foot-wall rock and run crosscuts into the fissure at short intervals. In the Park City mines it is not easy to determine beforehand the best method fir extracting the ore from a newly discovered ore shoot in the bedded deposits. While we may get one dimension from the drift run in the fissure, that will not give us a correct idea as to the other dimensions of the orebody. The fissures here referred to have a N. 35" E.

Jan 1, 1915

By John E. Sherborne

Much valuable scientific research has been performed in recent years on the subject of phase behavior of hydrocarbons.l-11 Engineers employed in petroleum production are interesting themselves in this work as well as in methods of applying the fundamental data available to the solution of their various problems. Recently a number of papers have been published in which applications of phase behavior have been made to specific cases pertaining to critical phenomena.l2-16 Little effort, however, has been made in the literature to show the relation between changes occurring in the critical region and the more common phase behavior, therefore it is believed that a presentation of the fundamentals of phase behavior with reference to hydrocarbons is timely. Study of phase behavior is not new. In the metallurgical field, knowledge of heterogeneous equilibria has advanced tremendously, particularly with reference to solid-solid and solid-liquid behavior. Much is known about vapor-liquid equilibria too, but few engineers are familiar with this subject. Definition of Terms In a discussion of this sort, a definition of terms used is most important. Such terms as "pressure," "temperature" and "volume" need little definition other than mention of the units in which they are considered. Pressure is expressed in pounds per square inch absolute. Temperature is usually expressed as degrees Fahrenheit or degrees Rankine. In considering thermodynamic and phase behavior, the use of the absolute, Rankine, scale is desirable. Volume is expressed as specific volume, such as cubic feet per pound. This will be recognized as the reciprocal of the specific weight. In considering systems composed of more than one component, it is sometimes desirable to consider molal

Jan 1, 1940

By John E. Sherborne

Much valuable scientific research has been performed in recent years on the subject of phase behavior of hydrocarbons.l-11 Engineers employed in petroleum production are interesting themselves in this work as well as in methods of applying the fundamental data available to the solution of their various problems. Recently a number of papers have been published in which applications of phase behavior have been made to specific cases pertaining to critical phenomena.l2-16 Little effort, however, has been made in the literature to show the relation between changes occurring in the critical region and the more common phase behavior, therefore it is believed that a presentation of the fundamentals of phase behavior with reference to hydrocarbons is timely. Study of phase behavior is not new. In the metallurgical field, knowledge of heterogeneous equilibria has advanced tremendously, particularly with reference to solid-solid and solid-liquid behavior. Much is known about vapor-liquid equilibria too, but few engineers are familiar with this subject. Definition of Terms In a discussion of this sort, a definition of terms used is most important. Such terms as "pressure," "temperature" and "volume" need little definition other than mention of the units in which they are considered. Pressure is expressed in pounds per square inch absolute. Temperature is usually expressed as degrees Fahrenheit or degrees Rankine. In considering thermodynamic and phase behavior, the use of the absolute, Rankine, scale is desirable. Volume is expressed as specific volume, such as cubic feet per pound. This will be recognized as the reciprocal of the specific weight. In considering systems composed of more than one component, it is sometimes desirable to consider molal

Jan 1, 1940

By E. W. Stewart, G. P. Conard, J. F. Libsch

The effects of several additives upon the reduction characteristics of hydrogen-reduced ferrous formate are described. The various additives inhibit sintering of the reduced iron particles by apparently different mechanisms. The magnetic properties of the low density compacts produced from the resulting ultra-fine iron powders were improved markedly. THE permanent magnetic characteristics of ultra-fine iron powder prepared by various means have been a subject of considerable interest and experimentation in the past few years. When such particles are small enough to show single domain behavior, they possess' 1—permanent saturation magnetization, and 2—high coercive force. In the absence of domain boundaries, the only magnetization changes in a particle occur through spin rotation which is opposed by relatively large anisotropy forces. With decreasing particle size, the coercive force tends to increase to a maximum and then decrease because of the instability in magnetization associated with thermal fluctuations. Kittel' has calculated the critical diameter at which a spherical particle of iron can no longer sustain domain boundaries or walls to be approximately 1.5x10-' cm. Stoner and Wohlfarthr in England and Neel4,6 in France have shown from purely theoretical calculations that the high coercive force expected from single domain particles is dependent upon crystal anisotropy, shape anisotropy, or strain anisotropy contributions. Further work by Weil, Bertaut,' and many others has contributed much to the understanding of fine particle theory. Neel and Meikeljohn" have demonstrated that a decrease in particle size below a critical value of approximately 160A leads to a quite rapid decrease in coercive force because of the prevention of stable magnetization by thermal agitation. Lih1, working with powders prepared by the reduction of formate and oxalate salts of iron, has shown the marked influence of powder purity upon magnetic properties. Maximum coercive force was obtained in powders of approximately 65 pct metallic iron content while the maximum energy product, (BxH) occurred in powders of 85 pct metallic iron content. Careful consideration of the preceding theoretical considerations and experimental results has led to the manufacture of permanent magnets from ultra-fine ferromagnetic powders by powder metallurgy techniques. Such work has been done by Dean and Davis," the Ugine Co. of France, and Kopelman." The aforementioned work of Kopelman and the Ugine Co. was concerned somewhat with the effect of various additives upon the properties of hydrogen-reduced ferrous formate. Virtually no work, however, has been published on the effects of additives on the reduction rates of metal formates, although unpublished work by Ananthanarayanan16 howed promise of improved energy product in ultra-fine iron compacts prepared by the hydrogen reduction of a coprecipitated mixture of magnesium and ferrous formate. After consideration of the preceding information, it was hoped that a better balance between the metallic iron content and particle size of the reduced iron powder could be accomplished by a prevention of the attendant sintering of the partially reduced iron powder during the reduction reaction. It appeared possible that magnesium oxide might interpose a mechanical barrier between adjacent iron particles and prevent their sintering together, while metallic cadmium and metallic tin would interpose a liquid barrier which might accomplish the same purpose. The degree to which these materials were effective in accomplishing the foregoing objective and the experimental details associated with the work are reported in the following sections of this paper. Experimental Procedure Preparation of Formate and Oxide Mixtures: To obtain ferrous formate of reproducible reduction characteristics, a slight modification' was made in the technique of Fraioli and Rhoda." A supersaturated solution of ferrous formate was mixed with an equal volume of 95 pct ethyl alcohol and the formate crystals precipitated by stirring and screened to —325 mesh. These crystals were in the shape of elongated hexagons, approximately 4x10 micron in dimension. Various preparations of such ferrous formate, designated as lot 111, were reduced for 2 hr, yielding ultra-fine iron particles of exceedingly reproducible size, metallic iron content, and magnetic properties. The magnesium and cadmium formates were prepared by the reaction of dilute formic acid with their respective carbonates, while the tin formate was prepared by the reaction of dilute formic acid with stannous hydroxide. To evaluate the effect of metallic formate additives in intimate mixture with the ferrous formate, varying amounts of magnesium, cadmium, and tin formates were coprecipitated with the latter. The designations of these materials and their chemical compositions are given in Table I. Due to the differing solubilities of the various formates in aqueous media,

Jan 1, 1956

By Benjamin LeRoy Miller, Joseph T. Singewald

The ore deposits at Firmeza have been worked continuously since 1884; those at Daiquiri since 1895. It is surprising, therefore, that they have not been the object of careful geologic study until quite recently. It is true that considerable attention was paid to these deposits by A. C. Spencer, in 1901, in the report on the geology of Cuba, by Hayes, Vaughan, and Spencer,l but this was only incidental to a hasty general reconnaissance of the Island. As far as the Daiquiri deposits are concerned, this gap has been filled by the appearance of the two papers by Prof. James F. Kemp2 and by Prof. Waldemar Lind-gren and Clyde P. Ross respectively.3 Max Roesler, first holder of the Emmons fellowship, made a detailed study of the Firmeza deposits during the past summer, so that soon we can expect a full description of them. Consequently, there is no, demand at the present time for a description of the deposits from other sources, and that is not the purpose of this paper. The papers on Daiquiri, however, leave unsolved problems in regard to the age of the rocks of the district and certain phases of the genesis of the deposits, and it is with the hope of aiding in the solution of some of these problems that this contribution is offered. Kemp, and Lindgren and Ross agree in assigning these deposits to the type of contact metamorphic deposits. They disagree in part on the question of their localization. The deposits occur in an extensive area of diorite which includes numerous blocks of limestone, and sometimes are found in the contact zones between these blocks and the diorite, and in other instances are completely enveloped in the diorite, showing no apparent connection with the limestone. The latter class includes

Jan 1, 1916

By W. E. Ruder

It has been pointed out by Stead1 that grains of considerable coarseness may be developed in steels containing from 3 to 5 per cent. of silicon, and in a previous paper2 the present author has shown that under the proper conditions of annealing single grains having an area of 50 sq. cm. may be obtained. It is the purpose of this paper to discuss in more detail the conditions promoting the growth of these grains, in the hope that the experiments described may throw some additional light upon the general problem of grain growth in metals. These silicon steels lend themselves particularly' well to such experiments because of the ease with which the change in structure may be followed and because of the fact that the effect of the carbon present is largely obliterated by the high percentage of silicon. This forms a solid solution with the iron, which acts very much like a pure metal. This alloy has been found to have but one critical point, viz., Ar2. This point, determined by Roberts-Austen for Hadfield's 4 per cent. Si alloy, was found to lie at 703" C. Vigouroux3, in working with pure Fe-Si alloys, finds this point to rise from 750" C. for 0.5 per cent. Si to 860" for 6 per cent. alloy, with a flat region in the curve from 3 to 4 per cent. Si. No accurate determination of this point has been undertaken by the present author, but it has been roughly determined to lie between 730" and 750:. In the preliminary experiments, some of which have been described in a previous paper, it was found that practically all of these steels, when annealed to 1,200" C. or higher, showed grains of comparatively large size. These grains varied in size, however, from about 4 sq. mm. to 50 sq. cm. (see Figs. 1 and 2) under the same conditions of anneal, and it was for the purpose of determining the cause of this difference in size that the experiments herein described were undertaken. From a preliminary study of the chemical composition of the specimens

Jan 1, 1914

By Forrest V. Williams

The dislocatiorl and stacking-fault structuve of epitaxial GaAs1-,PX lms been examined by chemical etching. The layers were groun in the (100) direction and etch Pils were developed on (111} planes which nad been lapped and polished on the epiLaxia1 layevs. Tile effecL of the jollolcing cariables on the quality of the epilaxial layers has been examined: doping leuel, grouth rate, and composition. High stacking-faullL densilies weve found in the GuAsi_xpx layers. These are not observed in heavily dolled epitaxial layers tzar in layers with low phosphorus compositions. The dislocatiorz density in GuAsi-x px was highest at the sub-stvate- epilaxia1 layer interface. Composilion changes introduced dislocations in the epitaxial layers. ManY semiconductor p-n junction lasers of Group TIT-Group V compounds and their alloys have been reported in the past several years. Laser action at visible wavelengths in GaAsl-x,Px was first reported by Holonyak and Bevacqua. GaAs, a direct transition semiconductor which lases, and Gap, an indirect transition semiconductor which does not lase, form a continuous series of solid solutions.2 Laser junctions can be fabricated in GaAsl-xPx crystals with phosphorus compositions up to about 40 mol pct. In addition to the production of coherent radiation in these crystals, the efficient recombination radiation of p-n junctions in this material has equally important potential in the development of low-power semiconductor lamps. To achieve a high conversion efficiency of electrical to optical energy in p-n junctions in this material, the relation of physical properties of the crystal to luminescence efficiency must be better understood. Although the electrical, optical, and device properties of GaAsl -xPx junction lasers are understandably of considerable interest, the work to date indicates that the more serious problems are the chemical and metallurgical difficulties encountered in the growth of this material.3 In addition to the problems of chemical purity, crystal imperfections, such as dislocations and stacking faults, can be expected to affect both the efficiency of the radiative recombination process and the perfection of the p-n junction.3 The last requirement, i.c., that of the perfection of the p-n junction, is a particularly troublesome one in the fabrication of laser diodes. To obtain good laser diodes, the p-n junction must be flat, which permits the radiation to be reflected from the resonant cavity boundaries. Junction planarity is extremely sensitive to the crystal perfection of the semiconductor material. Also, it is known that at high dislocation densities (-105 per sq cm) it has not been possible to build laser junctions in GaAsl-xPx . Few studies have been reported on the crystal defect structure of GaAsl-,P,. The first serious study seems to be that of Wolfe, Nuese, and Holonyak,3 who examined the dislocation structure of monocrystalline bulk (nonepitaxial) material grown by halogen vapor transport. In this paper are reported some observations on the dislocation and stacking-fault structure of GaAsl_,P, crystals grown by a vapor transport process on substrates of GaAs. EXPERIMENTAL Crystal Growth. The GaAsl-xPx crystals were grown in an open-tube flow system, using two sets of reagents. GaAs, Pr(red), and HC1 were employed in one method. The transport reaction is =950JC GaAs+HC1 = GaCl +1/4As4 +1/2H2 and the deposition reaction is 2GaAs1-xPx +GaCl3 Composition control is obtained by the flow rate of the HC1 and the vapor pressure of the P4, which is maintained in a separately controlled furnace. The second method has been described by Ruehr-wein4 and utilizes gallium, AsH3, PH3, and HC1. The same transport and deposition reactions as above are involved. Composition control is obtained solely by the flow rates of the three gases involved. All of the crystals were grown on chemically polished GaAs substrates oriented on the (100) plane. The thicknesses of the epitaxial layers were typically 100 to 300p. Revealing of Dislocations. Dislocations were re-vealed on both the( 111 ) and { l l l }b faces by chemical etching. The specimen to be examined was mounted at 54.7 deg, lapped on glass with 3-p alumina, polished on cloth with 3-p diamond paste, and, to remove work damage, chemically polished at room temperature for

Jan 1, 1968

By D Craw

Previous studies of alluvial gold in Otago and Southland placer deposits have suggested a gold-mercury association for some deposits derived from Caples Terrane schist, whereas alluvial deposits on Torlesse Terrane basement typically have no mercury. A regional study of gold from Otago Schist vein deposits from both Caples and Torlesse Terranes has revealed the presence of both Au-Ag and Au-Ag-Hg alloys in both terranes. Au-Ag alloy (3 - 4 wt per cent Ag) is typical for gold found in most Torlesse vein deposits, and Au-Ag-Hg alloy (3 - 8 wt per cent Ag, 2 - 8 wt per cent Hg) is found in many Caples vein deposits. Au-Ag-Hg alloys are not exclusive to the Caples Terrane, however, as Au-Ag-Hg alloys with up to 4 wt per cent Hg are found in vein material from the Torlesse-hosted, HydeMacraes Shear Zone. In addition, not all Caples-hosted deposits have a gold-mercury association; gold grains from the Carrick and Invincible gold fields have no detectable mercury. The present study characterises gold compositions from various hard-rock vein deposits and has potential for determining placer-source relationships.

Jan 1, 2003

By Charles Barnhart

This paper is a discussion of the causes of deflagration in cast blasting and a description of a project intended to demonstrate how changes in six critical parameters contribute to the deflagration chemical reaction. Control of these parameters is key to solving the nitrogen dioxide “orange smoke” problem. Preliminary results of an investigation into the development of a technology addressing the problem of atmospheric releases of nitrogen dioxide during cast blasting in surface mine operations are described. The project is funded by a $600,000 Small Business Innovative Research grant from the National Science Foundation and an $80,000 Abandoned Coal Mine Land Reclamation Program grant from the state of Wyoming. The presentation will address the measures required to control the blast chemical reaction so that it does not produce nitrogen dioxide through deflagration. Experimental blast data will be focused on a new shaped charge detonation system designed to instantaneously bring the powder column to maximum velocity of detonation (VOD), thus insuring efficient detonation of the entire colulnn.

Jan 1, 2003

By G. Hausen, H. Micka

"Modern signal and power electronics made adjustable-speed AC drives technically feasible and reliable and economically attractive. Cycloconverters are discussed as a proven technology for mine hoists. \IntroductionUntil rather recent technical and commercial advances in power and signal electronics, DC motors were used almost exclusively for applications requiring continuously adjustable operating speeds and torques. More recently, the significantly higher efficiency and the accordingly lower operating costs of AC motors gained importance. An effective and efficient speed control of AC motors requires the control of AC voltage and frequency. Table 1 shows typical applications of adjustable-speed AC drives.CycloconvertersOf particular interest to the mining industry are cycloconverters for hoist drives. The cycloconverter represents by far the simplest, most efficient and most economical means of converting a constant-voltage, constant-frequency supply into an adjustable-voltage, adjustable-frequency supply as required for the speed control of AC drives operating in the frequency range to half of the utility frequency.Cycloconverters feeding synchronous motors or induction motors are ideally suited for slow-speed direct-coupled drives."

Jan 1, 1988

By Jeffery Leavy, Ken Davis, Kirk H. McDaniel

The Waste Isolation Pilot Plant (WIPP) is a United States Department of Energy facility located in southeastern New Mexico. It is designed for the safe disposal of transuranic radioactive waste in deep geologic salt beds. Westinghouse TRU Solutions, LLC, the managing and operating contractor, undertook a project to simulate the processes at WIPP in order to identify bottlenecks and optimize available resources. The activities simulated in the model included the receipt, processing and disposal of radioactive waste underground, the mining of new areas for future waste disposal and the transportation of salt out of the mine. The complexity of the processes and the interactive requirements between processes required the use of advanced modeling techniques. The simulation model includes a huge number of locations and path network node points, with movement to and from the locations controlled using parameters rather than explicit routing. Information for the timing and sequence of the mining and nuclear waste emplacement operations is brought into the model via spreadsheets. Arrays in the simulation model keep track of past and future events that occur. Routing to the multiple possible positions in the underground mine is done using attributes, and system functions within ProModel in order to allow for a highly flexible sequence of planned events and to reduce the level of effort in creating the ProModel processing. Considerable use of subroutines in the simulation model is utilized for parametric decision-making that is repetitive. This presentation describes the modeling techniques used to accurately simulate the surface and underground operations. The surface and underground operations are considerably different, thus they will be treated in their own sections.

Jan 1, 2002

By W. L. DeMoulin

A rather detailed description of the entire plant and leaching process was given in a paper recently presented to the Institute,I so this paper will cover briefly only the crushing practice of the New Cornelia Copper Co. for the year 1918. The ore, which is mined by steam shovels and loaded in side-dump cars, passes through two crushing plants. These crushing plants were constructed to crush the ore required by a leaching plant of 5000 tons daily capacity, during a crushing period of 16 hours. The primary plant reduces to less than 3 in. (76 mm.) and the secondary plant, to 1/4 in. (6.35 mm.), which is sufficiently fine for satisfactory percolation of solution through the ore in the leaching tanks, and to give-good extraction. The ore is then conveyed to the leaching tanks by a system of 28-in. (71-cm.) belt conveyors. On the way to the leaching tanks, it passes through an automatic sampling plant, where a 1-per cent. sample is taken. From the primary crushing plant, the ore is conveyed by two 36-in. (91-cm.) belt conveyors to a 10,000-ton steel storage bin, with a reinforced-concrete flat bottom. The ore discharges from the bottom of this' bin onto four 20-in. belt conveyors, which deliver it to the four units of crushers in the secondary crushing plant. There is no storage bin between the mine and the primary crushing plant. The ore breaks very coarse, is very hard, and contains a great many boulders, some as large as 4 1/2 by 4 1/2 by 10 ft. (1.3 by 1.3 by 3 m.). Jams form in the bowl of the coarse crusher in the primary crushing plant, as a consequence, and are freed by means of an immense steel hook operated from a 40-ton electric traveling crane. Primary Crushing Plant The primary plant consists of one No. 24 Gates, style K, gyratory crusher, followed by four Gates No. 8, style K, gyratory crushers. All

Jan 1, 1920

By J. R. Mihalisin

Phase changes in as-cast alloys in the Ni2 CoCr-Ni, Ti-NSAl system containing 0.1 wt pct C were studied after heat treatment at 1650°F. It was found that a vegion of CrCo-type s was developed in this system after I1000 hr. The tendency for s formation was dePendent upon the aluminum and litanium content, the s -forming tendency generally becoming more pro-nounced as the latter two elements are increased. s lended to form in interdendritic regioues and was associated with solutioning- of- carbide phases. Electron- vacancy computations for prediction of s formation on these alloys mere in sufficient agreement with what was observed experimentally to indicate that the method should be of value in assessing a-forming potential in cast alloys. However, the correlation of electrotz- vacancy numbers may not be as favorable in cast as cormpared to wrought alloys. THE increasing use of high-temperature alloys for longer times at higher temperatures has resulted in a real need for obtaining information on the phase changes taking place in these alloys since these changes often have a direct effect on properties. This paper reports on a study of the phase changes in Ni-Cr-Co-Al-Ti alloys after prolonged heating at 1650°F. The alloys were selected from the pseudo-ternary system Ni2CoCr-Ni3Ti-Ni3Al and this system was chosen because it is the basis of many of the newer cast commercial superalloys. The attempt here was not to define accurately the boundaries of s formation in the NizCoCr-Ni3Ti-Ni3Al system but to delineate the phase transformations taking place upon heating alloys covering a wide range of chemistries in this system. An addition of carbon was made to all alloys to further simulate commercial alloys. It was hoped that the information generated in this manner would be of more direct use to superalloy designers than an equilibrium diagram approach since commercial alloys generally have outlived their usefulness when equilibrium is attained. EXPERIMENTAL PROCEDURE The alloys were vacuum-melted from carbonyl-nickel pellet, vacuum-grade chromium, electrolytic cobalt, high-purity aluminum and titanium, and spec-trographic-grade carbon.

Jan 1, 1968

By Thomas S. Carnahan

The mining property of the Utah Copper Co. is situated in the West Mountain mining district, Salt Lake County;Utah, in the Oquirrh Range of mountains. Geology In a general way the rock formation of the district consists of a series of beds of quartzite and limestone intruded by a body of monzonite porphyry roughly elliptical in shape, with an east-west axis over a mile in length and a north-south axis of about 3,000 ft. This porphyry intrusion, accompanied by strong mineralizing action and fracturing, resulted in the formation of orebodies in the adjacent sedimentary rocks, and was itself sufficiently mineralized to make it one vast orebody. The Utah Copper Co.'s mining property comprises within its boundaries practically the entire outcrop of the monzonite mass, of a commercial grade. Genesis of Porphyry Ore Following an intricate system of fracturing, mineral solutions circulated freely through the porphyry, depositing small quantities of copper and iron, and resulting in a considerable silicification of the monzonite. The quantity of copper originally deposited was undoubtedly too small to have ever given the porphyry a commercial value, had not secondary enrichment, due to the leaching of the copper from the surface of the mass and re-deposition in the sulphide zone, been active over a long period of years. A large portion of the leached material has probably been removed by erosion, but there still remains a blanket of leached and oxidized porphyry of varying thickness covering the sulphide ore, known as capping. Over certain sections of the orebody, this capping contains commercial quantities of copper carbonates, but most of it contains little or no copper.

Jan 1, 1916

Dr. Healy's paper presents a concise state-of-the-art description of mechanistic, thermodynamic models available today for design, interpretation, and trouble-shooting flocculation processes and problems. Coagulation by manipulation of inorganic electrolyte concentrations is controlled largely by adjustment of electrostatic repulsive forces, guided by well understood theory. For simple solids in simple electrolytes, existing models are capable of predicting the influence of potential determining ion and one dominant, non-reacting, symmetrical electrolyte concentration on floc stability quantitatively. Concentration changes required to coagulate and disperse can be estimated. Convenient, easily understood means are available for summarizing the effects of key variables, (e.g., pH, ionic strength) on dispersion stability, and estimating tolerance to unintentional changes (Matijevic coagulation domain diagrams). These models have not been developed to the point that mixed unsymmetrical electrolytes can be easily handled. They are capable of describing two- solid heterocoagulation, but not “n-solid” heterocoagulation. In combination with recently developed computer codes for simultaneous computation of solution equilibria, ion exchange and electrical double layer properties (1,2), these models .should be capable of describing simple clay coagulation systems. This has not been done. Models developed for polymer flocculation are valuable interpretive tools, have some qualitative predictive value, but are less potent in quantitative needs. Most real systems probably involve more than one mechanism of floc stabilization. Little has been done toward developing combined models, even in the simplest systems.

Jan 1, 1979

By W. F. Nothard, J. R. C. Hill

The Rhodesian approach to the vegetating of slimes dams by J. R. C. HILL, B.Sc.(Agric.) (Visitor) and W. F. NOTHARD (Visitor) To prevent environmental pollution from mine dumps, it is necessary to stabilize them either mechanically or biologically. In the long term biological stabilization is more attractive because of its permanent nature. Initially, the basis of stabilization is in the correct siting and construction of the dump. The main toxic factors influencing plant growth on Rhodesian mine dumps are arsenic, antimony, copper, nickel, a high ratio of magnesium to calcium, excessive soluble salts, high pH, and Iow macronutrient content. Root-growth studies in culture solution and pot experiments are used to supplement information on the suitability of plant material obtained from replicated field trials on mine dumps. In addition to the selection of plants for toxic tolerance, it is advisable to provide multiple-layer protection with trees, shrubs, and grasses. Further, a range of different plant species gives greater biological stability. Protection must be provided for young plants against wind erosion and the abrasive effects of windblown sand. Planted wind breaks are preferred to mechanical forms; windrows of garden refuse make good wind breaks and at the same time introduce organic material to the dump and provide a good environment for seedling establishment. The use of artificial fertilizers and sewage effluent is recommended to hasten the development of a complete and protective plant cover.

Jan 12, 1973