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By Leslie Burris, J. C. Hesson

The diffusivity of uranium in liquid cadmium has been measured as a function of temperature by the capillary -bath technique. The diffusivity measurements were made at 4509 500°, 575º, and 650°C, over which temperature range the diffusivity of uranium varied from 1.3 to 2.3 x 10-5 sq cm per sec. The diffusivity of uranium in cadmium was less than that predicted by the Einstein-Stokes equation. VERY little information is available on the diffusivity of uranium in liquid metals. Bonillal has reported a single measurement of the diffusivity of uranium in bismuth. Measurement of the diffusivity of uranium in cadmium was undertaken, not only to supply data in an area in which a dearth of information exists, but also because of a need for this physical property measurement in connection with mass transfer studies now underway in the U-Cd system at Argonne National Laboratory. The capillary-bath method used in this work has been successfully used by other workers2"4 to obtain diffusivities in liquid metal systems. Although considerable experimental technique is required to obtain reliable diffusivity measurements, the basic information required is only that of temperature, capillary tube length, the initial and final compositions of the alloy in the capillary tube, and the composition of the bath into which the solute element is diffusing. From these measurements, diffusivities may be calculated using Fick's law. The diffusivity equations are presented in the Appendix. Equations which are often used to predict diffusivities in dilute solutions5 are the Einstein-Stokes equation: D= (kT)/(6pµr) and the Eyring equation: D = (?,kT/?y?zp), where D= diffusivity (sq cm per sec), k = Boltzman's constant, T= temperature ("K), p = viscosity (poises), r = radius of diffusing molecule or species (cm), and A,, Ay, and A, are the diameters of the diffusing molecule in the three axial directions. For round molecules, the Eyring equation gives values which are 37r times larger than the Einstein-Stokes equation. In this work, the experimental values were compared to the Einstein-Stokes equation. Experimental values of diffusivities in liquid metal systems usually lie between those predicted by the Einstein-Stokes and Eyring equations. The viscosity values for cadmium were obtained from the Liquid Metals Handbook.6 EXPERIMENTAL APPARATUS AND PROCEDURE The general procedure employed consisted of rapidly immersing in a molten cadmium bath containing a negligible amount of uranium a capillary

Jan 1, 1963

By G R. Ballantyne, M S. Powell, M Tiang

This paper reviews the proportion of energy attributable to comminution within the Australian gold and copper mining sector. The need for this is motivated by inconsistencies in the quoted energy usage data and the lack of a common basis for reporting the fraction of energy in mining that is attributable to comminution. This study should form a reliable basis from which to assess both demand and opportunities to reduce energy consumption.The proportion of milling energy was calculated for the major producers in the Australian gold and copper sector. A sampling methodology created by Powell et al (2003 - 2010) was initially used to provide an accurate and meaningful measure of the energy used in the comminution process. However, no useful method for grouping similar mines was found. Fortunately, a surprisingly large amount of high quality data was found from a number of different sources, allowing the development of robust relationships to be used to estimate a high proportion of the unknown values. The fraction of energy attributable to comminution was found to be dependent on how the total energy consumption was defined. For instance, comminution accounted for 52 per cent of the electrical energy, but only 21 per cent of the total energy publicly reported by the mines because a substantial proportion of energy used on a mine is in the form of transportation fuel (mostly diesel). Critically, the measured electrical energy consumption does not account for transmission and generation losses, while diesel energy usage is typically quoted according to its calorific value. This review proposes that diesel should instead be converted via the mechanical efficiency factor for diesel engines. Using this conversion, comminution was found to account for 36 per cent of the available energy on average. This approach allows a useful basis of comparison for mines regardless of whether milling energy is obtained from electrical or diesel generation. A summary of the results are shown in Figure 7 with other values obtained from literature. The total comminution energy assessed in this study accounts for 1.3 per cent of AustraliaÆs electricity consumption, this figure will increase as the other mineral commodities are added to the study.CITATION:Ballantyne, G R, Powell, M S and Tiang, M, 2012. Proportion of energy attributable to comminution, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 25-30 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By Erich Hovestädt, Hans-Jürgen Odenthal, Christian Wuppermann, Herbert Pfeifer, Antje Rückert

"During the argon oxygen decarburization (AOD) process high-chromium steel melts are decarburized by oxygen and inert gas injection through sidewall nozzles and a top-lance. Due to the large amount of the injected processing gas, low frequency oscillations of the vessel can be observed. It is suspected that these oscillations can influence the converter's structure. The exchange of forces between fluid and the surrounding vessel is the focus of this study. An oscillation model was developed and tested, one objective being to limit the computational effort which is necessary for fully coupled and time resolved CFD and FEM simulations. Experimental results obtained from water-model studies as well as from on-sight measurements are available and were used in order to validate the numerical results. The authors' intention is a contribution towards a more in depth understanding of the factors influencing vessel vibration during the AOD process.IntroductionDuring the last four decades the AOD process has been established as a reliable and efficient refining process in stainless steel making. The injection of process gases (O2, N2, Ar) through sidewall nozzles shows advantages in mixing effectiveness compared to other injection geometries e.g. bottom blowing [1]. Stainless steel grades contain usually more than 10% chromium. With decreasing carbon content during the decarburization periods the tendency of chromium oxidation increases according to the varying chemical equilibrium which depends on the partial pressure of carbon-monoxide (CO) in the gas phase. That's why oxygen is gradually replaced by inert gases, usually argon or nitrogen, in order to lower the CO partial pressure and thus to minimize chromium oxidation. Despite the high injection velocity of approximately Ma = 1, the kinetic energy of the gas jets is consumed within a short distance from the nozzle exits due to the large density ratio between gas and melt of approximately 1:8000. With increasing distance to the nozzle exit, the initial horizontal velocity of the gas jet decreases and due to buoyancy force motion of the detached bubbles turns into a vertical direction. Subsequently a gas plume develops with its typical conical shape described by various authors [1-4]. Due to the drag force between gas bubbles and melt also the liquid phase is forced into a vertical motion. Near the free surface and the wall regions the melt flow is deflected in different directions. Subsequently, the typical flow pattern in the AOD vessel arises, as sketched in Figure 1 and described in literature [5-9]."

Jan 1, 2012

By John Henry Harden

IN 1874, with Mr. H. Y. Attrill, of Baltimore, Md., I made an examination of some property at Goderich with reference to sinking for and mining salt. With this end in view we visited all the wells in the neighborhood, but the information sought being of so unreliable a character I advised the putting down of a borehole on the property. This has since been done, the result of which has lately been published by Dr. T. Sterry Hunt in the Toronto Globe. From this there appears to have been passed through six beds of salt of an aggregate thickness of 123 feet. Rock-salt was known to exist, for, by the boring of existing wells, small crystals had been brought to the surface in the dirt, but no attempt had before been made to obtain a reliable sample or to prove the number and thickness of the beds. The question now remaining for discussion is, shall the present method of obtaining the salt be continued, or shall the beds be won by a shaft in a regular mining fashion, by which means the salt may be gotten in a condition almost ready for the market? The present mode of obtaining salt is by boreholes from 6 inches to 8 inches in diameter drilled to the beds, into which is inserted a pump. The "feeders" of fresh water intersected in drilling the well are allowed to descend on the outside of the pump-tube to the salt beds and there become saturated, when, on use of the pump, brine is obtained for evaporation. In the beginning brine can only be had in limited quantity, but by the daily application of the pump, and the gradual solution of the salt, a larger surface becomes exposed to the action of the fresh water, and a continuous supply of brine is obtained. It will then be understood that the supply of brine is dependent upon the feeders of fresh water intersected in boring the well, which, we are told, have never shown any sign of diminution, and this is the water that must be encountered in sinking a shaft. There are ten wells in operation at Goderich, the most important one to the present project being known as the Hawley Well, located at an elevation a few feet above Lake Huron at the mouth of the river Maitland, at a much lower level and nearer to the proposed shaft than any other well in the district. At this well the feeders

Jan 1, 1877

By James R. Oehler

Progress, future challenges, and the continual search for more efficient and rapid methods of excavating underground openings and shafts were main themes at the 1983 Rapid Excavation and Tunneling Conference (RETC) held June 12-16 in Chicago, IL. The event, jointly sponsored by the Society of Mining Engineers, the American Society of Civil Engineers, the Canadian Institute of Mining and Metallurgy, and the Engineering Institute of Canada, offered a diverse program for both civil and mining engineering disciplines. Although all papers given at the three-day conference were noteworthy contributions, and each is included in the conference proceedings currently available from SME, there were a few sessions that had particular mining-related interest. Research, Acceptance Needed for Water-Jet Technology Water-jet-assisted rock excavation is seen by some as a technology moving from the prototype phase to a fully developed, accepted system within the next decade. For an industry that is traditionally fairly slow in accepting significant changes, this development appears especially noteworthy. However, speakers at the water-jet technology session generally agreed that many large US manufacturers are not viewing water-jet-assisted equipment as viable replacements for all-mechanical systems. This, they fear, may mean some US manufacturers will lose a significant share of certain equipment markets to foreign competitors who are moving aggressively ahead in this area. Despite the advantages of increased cutting rates, reduced power requirements, less dust, prolonged bit life, and reduced sparking in many cutting situations, water-jet technology applied to mining is apparently having some acceptance problems in the US. R. J. Evans, professor of industrial engineering at the University of Pittsburgh, noted that there are several perceptual barriers to water-jet coal cutting; such as uncertainties concerning the fu¬ture demand for coal and the reliability of equipment, apprehensions that jet-assisted equipment will make the mine operator dependent on specific types of hard-to-obtain equipment, and fears about accessibility of the equipment for repairs. Evans also said numerous parameters need defining before taking advantage of water-jet-assisted cutting systems in under-ground coal mining in the US. For the cutting head, information must be obtained on optimum bit geometry and spacing, and maximum and minimum torque requirements. For a complete US water-jet cutting system, Evans added, research is needed to establish optimum jet pressures, jet powers, number of jets per bit, and location of jets relative to the bit. One research project making progress towards optimizing parameters for a water-jet-assisted drag bit cutting system for coal mining was described by Levant Ozdemir, director of the Earth Me- .

Jan 8, 1983

By G. Thodos, E. M. Phillips

A reduced density correlation for the gaseous and liquid regions of ethane has been developed from all the experimental PVT data available in the literature for this substance. Saturated vapor and liquid densities reported for methane, propane and n-butane were utilized to establish the rectilinear-diameter line for ethane. This line was then used with the saturated-vapor data for ethane to produce the saturated envelope for this substance. Most of the saturated liquid data reported for ethane were found to be inconsistent with the saturated-liquid curve resulting from this study. The correlation covers the regions 0.65 < TR <6.0 and 0 < PR < 15. For regions for which no experimental data have been reported, the isobars of the correlation were extended by the use of the theorem of corresponding states. This correlation is presented both on rectilinear and log-log coordinates. INTRODUCTION At the present time, there is considerable interest in the exact PVT behavior of pure hydrocarbons. Matschke and Thodos12 recently have developed a comprehensive compilation of experimental vapor and liquid density data for methane. Similar studies have been conducted for other pure substances.4, 7 In the present study the density data available in the literature for gaseous and liquid ethane have been critically reviewed and utilized to develop a reduced density correlation for this substance. SATURATED LIQUID AND VAPOR DENSITIES The rectilinear-diameter rule proposed by Cailletet and Mathias5 states that the sum of the saturated liquid and vapor densities of a pure substance is a linear function of temperature which passes through the critical point. This law, although empirical, has been well established by continued verification since its conception in 1886. This rule has been applied to the saturated density data of methane,6 propane 17 and n-butane8 to produce the straight lines presented in Fig. 1 which pass through the critical point TR = 1.00, Pr = 2.00. The rectilinear-diameter relationship for ethane was established from the lines for the other substances in Fig. 1 by plotting the quantity p~, + PR against zc for different reduced temperatures. A critical analysis of the saturated vapor and liquid densities reported for ethane by Kuenen,10 Maass and McIntosh,11 and Sage, Webster and Lacey18 revealed that the values of PR1 + pr resulting from these studies were inconsistent with the rectilinear-diameter line obtained from the reliable density data of the other substances, as shown in Fig. 1. In the analysis of these data, reduced quantities were calculated using the critical con-

Sample preparation for gold samples, where the distribution and size of gold particles is often irregular, usually demands that a relatively large sample weight is taken to produce a representative sample for analysis. Traditional sample preparation of gold samples incorporated multiple stages of coarse particle size reduction followed by subdivision of the sample prior to final fine pulverising. This technique developed because of the limited equipment options available to laboratories. As a result significant errors are introduced and the final sample size being pulverised is a small fraction of the original sample weight. Three significant developments have occurred in the last 25 years to significantly improve sample preparation of gold samples: 1.&nbsp; large capacity fine pulverising,2.&nbsp; fine jaw crushing, and3. &nbsp;whole sample coarse pulverising. In the mid-1980s an Australian manufacturer developed large capacity pulverising bowls which had the ability to reduce samples with a mass of 1.5 - 3.5 kg to a nominal 0.075 mm product in approximately three to five minutes. Laboratories were able to produce a large homogeneous pulverised sample which significantly reduced the error in sampling. However, exploration and mine samples are usually 7 to 10 kg and the sample requires a subdivision stage following crushing to produce the 3.5 kg for the pulverising step, thus introducing potential for significant error. The development of fine jaw crushing allowed particle size reduction to -2 mm which reduced the subdivision error of the bulk sample prior to fine pulverising. Subdivision of the crushed sample at -2 mm still results in potential sampling errors, where the gold particles are not sufficiently liberated to be representatively sampled. Clearly the best option would be to reduce the particle size small enough to ensure a representative sample prior to final pulverising. Continuous mills offer a partial solution but are relatively slow and subject the sample to differential pulverising prior to subdivision. Clearly this does not provide the best solution for routine laboratory applications where high volumes of samples are to be processed. The recent development of a large capacity coarse pulverising system allows samples of up to 10 kg to be reduced to -0.25 mm prior to subdivision, and fine pulverised to -0.075 mm. Laboratories now have the necessary equipment to perform reliable large capacity sample preparation of gold samples. The exact choice of a sample preparation scheme may still depend on particular ore types but the need for multiple crushing and subdivision stages is redundant.

Jan 1, 2008

By John Henry Harden

IN 1874, with Mr. H. Y. Attrill, of Baltimore, Md., I made an examination of some property at Goderich with reference to sinking for and mining salt. With this end in view we visited all the wells in the neighborhood, but the information sought being of so unreliable a character I advised the putting down of a borehole on the property. This has since been done, the result of which has lately been published by Dr. T. Sterry Hunt in the Toronto Globe. From this there appears to have been passed through six beds of salt of an aggregate thickness of 125 feet. Rock-salt was known to exist, for, by the boring of existing wells, small crystals had been brought to the surface in the dirt, but no attempt had before been made to obtain a reliable sample or to prove the number and thickness of the beds. The question now remaining for discussion is, shall the present method of obtaining the salt be continued, or shall the beds be won by a shaft in a regular mining fashion, by which means the salt may be gotten in a condition almost ready for the market? The present mode of obtaining salt is by boreholes from 6 inches to 8 inches in diameter drilled to the beds, into which is inserted a pump. The "feeders" of fresh water intersected in drilling the well are allowed to descend on the outside of the pump-tube to the salt beds and there become saturated, when, on use of the pump, brine is obtained for evaporation. In the beginning brine can only be had in limited quantity, but by the daily application of the pump, and the gradual solution of the salt, a larger surface becomes exposed to the action of the fresh water, and a continuons supply of brine is obtained. It will then be understood that the supply of brine is dependent upon the feeders of fresh water intersected in boring the well, which, we are told, have never shown any sign of diminution, and this is the water that must be encountered in sinking a shaft. There are ten wells in operation at Goderich, the most important one to the present project being known as the Hawley Well, located at an elevation a few feet above Lake Huron at the mouth of the river Maitland, at, a much lower level and nearer to the proposed shaft than any other well in the district. At this well the feeders

By M Titley, E Maidens

Many gold deposits were mineralised by fluids and processes that also altered the host rocks. This alteration may often be a useful visual aid that distinguishes barren, low-grade from high-grade regions in a rock mass. Alteration intensity is commonly used in gold deposits as a visual tool, along with face sampling or grade control support, to define oreblocks and guide excavation in underground and open pit mining. However, alteration is not often used at the resource estimation stage. Mineralised lodes are usually defined by geologists using a ægeo-grade envelopeÆ, where a number of constraints are considered, including an (arbitrary) cut-off grade; the ænaturalÆ grade break between high- and low-grades; and geological features including structural, lithological or alteration continuity. The geo-grade envelope is usually thought to satisfy the requirements of stationarity for grade estimation, and is considered a single domain. This paper examines a modelling technique combining gold grade and alteration, applied to the Wallaby deposit in Western Australia, to imbue a greater level of detail to the grade estimation in a region tested by relatively sparse drilling. This was achieved by utilising the correlation of gold grade and alteration, along with the spatial characteristics of the alteration, when estimating grades within a number of lodes. The alteration-driven estimation was utilised in conjunction with an unfolding approach, and the use of probability estimates, to overcome geometric data constraints. This technique allows greater control and most likely provides a more reliable estimate of the mineable resources than a global grade cut-off when visual control is to be a major vector in grade control.

Jan 1, 2003

By Thomas P. Kwiatkowski, Len Cobb, Christopher D. Orlandi, Judith H. Jones

The Inland System supplies raw water to the industrial and domestic users in the City of Birmingham, Alabama. The Inland System, which is nearly 60 years old, consists of an approximately 57.9m (190 feet) high earthen dam across the Blackburn Fork of the Black Warrior River, a 39.6m (130 feet) high reinforced concrete intake structure, a 1524mm (60inch) diameter Dresser coupled steel transmission pipeline, and various distribution lines extending into Birmingham. The Inland System was owned, operated and maintained by the Industrial Water Board (IWB) of the City of Birmingham, an agency of the city government, from 1958 until 1994. In 1994, the City of Birmingham consolidated all water and distribution functions under the Birmingham Water Works Board (BWWB). In 1988, the IWB determined that the Inland System had reached a point where its reliability could not be assured without an in-depth evaluation and renovation. The IWB engaged Christy/Cobb, Inc. (CCI) of Birmingham as its consultant for the renovation work. CCI evaluated the Inland System and submitted a report to the IWB in April, 1992. The report contained several recommendations for capital improvements to the system including increasing the emergency spillway capacity, reconstructing the fuse plug, relocating public access to the lake away from the dam area, constructing a new intake structure, and constructing a tunnel through the dam abutment to deliver the water from the proposed intake structure to the existing 1524mm (60 inch) diameter supply line. The new intake structure and tunnel would provide for a future maximum demand flow rate as well as provide bypass and level control capabilities. CCI was authorized in 1992 to proceed with the engineering design for the renovation of the Inland System with emphasis on the spillway and intake structure. PROJECT DESCRIPTION The major component of the renovation of the Inland System was the new intake structure and tunnel through the dam abutment. CCI engaged Jenny Engineering Corporation (JEC) of Springfield, New Jersey as a consultant for the tunnel design. JEC was responsible for the design of the tunnel, the connecting shaft between the intake structure and tunnel, and the steel pipe final lining, while CCI was responsible for the intake structure and the connection to the existing supply pipeline as well as overall project management. CCI and JEC evaluated the project site in order to select the location for the new intake structure and set the alignment for the tunnel. A factor in the evaluation process was that the level of the lake could not be lowered to construct the new intake structure since the supply of water from the Inland System had to maintained. Therefore, a location was required which was

Jan 1, 1997

By Robert T. Pring

IN addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of employees, with a consequent decrease in labor turnover rates. One progressive mining company1 estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination decreases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor. Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flowsheet. Exhaust ventilating systems are now afforded equal care in design and maintenance to that given other machinery more closely related to the process. METHODS OF DUST CONTROL "Dust control" is a general term descriptive of a number of methods used singly or together to prevent particulate atmospheric contamination. These methods are, in order of their desirability, as follows: I. Change of process. 2. Isolation of process. 3. Wet methods. 4. Ventilation. a. Local exhaust ventilation. b. General ventilation. 5. Personal respiratory protection. In ore-concentration plants it is seldom practical to change a process to eliminate the dust it creates It is possible in some cases to isolate a particular dust-producing operation from the rest of the plant, provided that constant attention on the part of the operators is not required. Frequently water is used in fine crushing and fine grinding, primarily to facilitate the processing of the ore and incidentally to allay the dust produced. Wet methods, however, are not feasible in coarse and secondary crushing operations, because of the relatively great volume of water required in instantly wetting each freshly fractured rock surface. Such quantities of water would entail conveying and storage difficulties. Local exhaust ventilation is the most effective and most commonly applied control measure, wherein directional air currents through the zone of dust production draw the contaminants into a duct system. Unfortunately, only a limited amount of reliable information on exhaust ventilation is available.2-5 Of necessity these publications are rather general, being primarily concerned with engineering fundamentals. While many organizations have successfully

Jan 1, 1940

By David I. Hoyer

It is shown that by monitoring longwall leg pressures in real time, warning can be given for significant weighting events and the formation of roof instabilities, such as roof cavities, several hours in advance. Longwall Visual Analysis (LVA) is a software package that continuously monitors shield pressures and shearer position in longwall mines. LVA has been running on 19 Australian longwalls for up to four years, and as a result a very substantial database of shield pressure trends in a wide range of longwall situations has been collected. This database has been analyzed to develop indicators that will give operators and geotechnical engineers advance warnings of developing conditions such as weighting events and difficult roof conditions. LVA displays live charts of data, such as shield leg pressures, loading rates, and yield frequencies. Data analysis techniques were applied to historical data records from multiple longwall sites in order to develop a ?Cavity Risk Index? (CRI). The CRI indicates the risk of roof cavities developing, and it is based on pressure trends that indicate significant yielding and loading rates spanning a region of relatively low support. Case studies from different longwalls are given, showing how the CRI can give real-time advance warning of the formation of roof cavities with their anticipated location on the face. The limited number of case studies done so far indicate that the predictions have a high degree of reliability, but more work is required to quantify this.

Jan 1, 2011

By R. W. Schenker

INTRODUCTION Environmental and occupational safety and health requirements often have a major impact on the design of comminution circuits, leading to increased capital and operating costs and reduced income. A project&apos;s capital cost can be increased by environmental permitting delays and the addition of dust collection equipment. Income can be reduced by lost production during unscheduled plant shutdowns for dust collection equipment maintenance. Dust collection equipment must be carefully selected and sized to minimize impact on the project. The equipment performance must comply with environmental regulations and allow working areas to comply with occupational safety and health regulations. Unnecessary overdesign could jeopardize the project&apos;s desirability from an economic standpoint. The equipment must be sufficiently reliable to avoid interference with production schedules. This chapter provides practical information on the selection and sizing of comminution circuit dust collection equipment that is consistent with the requirements stated above. It presents information on the reasons and general principles of dust collection; various types of dust collection equipment; and design criteria for ventilation hoods, duct systems, fabric filter dust collectors, and fans. An example discussing the selection and sizing of dust collection equipment for a simple comminution circuit is also presented. REASONS FOR DUST COLLECTION Dust collection equipment should be installed in comminution circuits for a variety of reasons, some of which are discussed below. These include compliance with government regulations, minimization of housekeeping requirements, product recovery, and improvement in public and employee relations. Compliance with Government Regulations Dust emissions from comminution circuits must comply with both air pollution control and occupational safety and health regulations. The regulations that may influence the selection of comminution circuits are discussed in more detail in Chapter 2. Air pollution control regulations limit the emission of dust, as well as visible emissions to the atmosphere and the concentration of dust in the ambient air. These regulations minimize the degradation of air quality and impact to other environmental considerations such as the health of the general public,

Jan 1, 1982

By A. B. Kinzel

INCLUSIONS of nonmetallic matter have long been recognized as objectionable in steel. A complete theory of the effect of inclusions, which is consistent with that held today, was outlined in Howe&apos;s early work on the metallurgy of iron and steel. This, by analogy with wrought iron, assumes that the observed difference in properties between specimens with and across the direction of rolling is due to slag enclosures. The fact that wrought iron shatters in ballistic test is taken as an indica-tion of the effect of inclusions on the resistance to shock. Since that time, the development of the metallurgical microscope has shown the discrete nonmetallic inclusions in the iron matrix. Better resolution has, brought out the great number of inclusions, and the availability of good microscopes in steel mills and laboratories has constantly drawn more attention to these inclusions. This recent emphasis on inclusions has resulted in studies as to their nature, mode of formation and methods of elimination, such as the work of Wohrman, Dickenson, Herty, and Schenk. In addition to the published works; many investigations which have not been published&apos; have been carried out by private laboratories and have resulted in the application of specifications intended to limit inclusions in many qualities of steel. Nevertheless, a clear understanding of the quantitative effect of inclusions on the physical properties of steel has been lacking. It is the specific purpose of this study to determine the quantitative effect of inclusions on the physical properties of steel that determine its behavior under dynamic stress. The study has shown that a quantitative relation between counted inclusions and impact strength does exist in normalized steels, but &apos;that factors other than readily visible inclusions are equally important. Furthermore, the present commercial rating of inclusions is unreliable with respect to counted inclusions or dynamic tests, and this study indicates that the tensile-impact test is more reliable as a measure of quality.

Jan 1, 1931

By Graham Bright

THE rapid increase in reliability, the low cost f operation, the ready application of safety devices, and the growing availability of central-station power have made the question of installing a hoist of the electric type no longer debatable. Where adequate electric power is available, there are few cases where it would be advisable to install a steam or air hoist. The type of electrical equipment depends largely on the nature of the power supply, its capacity, and the form of the power contract under which power is purchased. In a large majority of cases, the available electric power is alternating current, three phase, 60 cycles. There is, however, considerable 25-cycle power in use; and in a few instances constant voltage direct current is the only power available for a small or an occasional medium-size hoist. Where a new hoist is to be installed, the designer of the mechanical parts can readily take care of the maximum stresses likely to be imposed by the&apos; motor. Where the hoist is already installed and operated by steam or air and it is desired to substitute an electric motor for the engine, a careful check should be made to determine the advisability of using the old mechanical parts. In most cases it is better to install a complete new hoist than to attempt to use old mechanical parts. A steam engine has a definite maximum torque, which the hoist has been designed to withstand, while a motor may be able to deliver momentary torques beyond the strength of the mechanical parts of the hoist. The selection of the proper type of electrical equipment can only be made after complete information is obtained and certain calculations made to determine the capacities required. There are several methods used in making hoist calculations, but no matter what method is utilized a fair degree of familiarity with hoists and hoisting conditions is necessary before an intelligent analysis and proper selection can be made.

Jan 9, 1921

By A E. Annels, M D. Raine, I M. Platten

Lode-gold systems are often characterised by a high to extreme nugget effect (>50 per cent), and the presence of coarse gold particles (>100 ¦m in size). They rank amongst the most difficult of ore deposits types, in terms of producing an accurate and precise resource estimate. Their effective sampling is generally difficult because of the relatively low concentrations involved and erratic nature of the gold particles. Grade continuity is usually less consistent than gross geological continuity, and is typified by the localisation of grades within discrete oreshoots. In most cases drilling, particularly diamond drilling is an effective measure of global geological continuity, whereas grade can only be reliably resolved from underground development. Depending upon drill density and geology, it is unlikely that anything above an Inferred Mineral Resource can be estimated from surface drilling alone. Underground development, in-fill drilling and, potentially, bulk sampling or trial mining will be required to delineate Indicated and Measured Mineral Resources and subsequent Ore Reserves. Grade estimation will have to account for highly skewed and often multi-modal populations, extreme values, a high nugget effect and low geostatistical ranges. A clear geological model that honours both geological and grade continuity must drive the resource estimation process.

Jan 1, 2003

By John R. Keith

Keith, John R. 1968. Relationships of lead and zinc contents of trees and soils, Upper Mississippi Valley District. Preprint, Fall 1968 Meeting, Soc. Mining Engineers of AIME. Lead and zinc contents of elm, maple, and oak trees and of soils in which the trees grew were determined in samples from the Upper Mississippi Valley mining district, and from an area outside but contiguous to the district. The lead and zinc analyses of plant materials served to differentiate the mineralized and non-mineralized areas. Stems contained about two times as much lead and about 2-5 times as much zinc as did leaves taken from the same stems. Lead and zinc analyses of all soil horizons could be used to differentiate between the two areas. Soils at most sample sites in the mineralized district seemed to be more reliable than plants for geochemical prospecting and are a more practical sampling medium. Soil samples from areas with thick loess cover, however, failed to indicate the presence of mineralized bodies whereas tree samples from the same sites contained anomalous amounts of lead and zinc. It is suggested that in areas of thick loess cover plant samples could be used in prospecting for lead and zinc.

Jan 1, 1968

By Chu E. Ho

Current methods of determining jet grout column diameters are highly empirical and site specific, and do not take into account the jet hydrodynamics and soil parameters explicitly. A theoretical model which describes the jet excavation mechanism is introduced in this paper, with the aim of providing an improved prediction tool that can be used in jetting design. The model is based on the assumption that the velocity distribution in the cutting jet is equivalent to that of a free jet with boundaries corresponding to the dimensions of the cavity excavated in the ground. The shape of the cavity formed depends on the erosional properties of the soil and jet expansion is limited by the resistance at the jet-soil interface. The model predicts that the limit of jet penetration is reached when the average dynamic pressure at the jet tip becomes equal to the ultimate soil bearing resistance. The reliability of the model, evaluated using results from four case histories of jet grouting field trials, is within ±15%.

Jan 1, 2006

By George H. C. Norman

A NUMBER of methods have been developed for the determination of the dust concentration in air, some of which have been reported as very efficient and for research may be more satisfactory than the method about to be described. In practical mine use, however, the accurate research equipment is unwieldy and requires a high degree of technical skill to manipulate it. Also, it gives less general practical information to the operator in the same length of time than the method described here. Moreover, it is doubtful whether at the present stage of affairs the results obtained from the precise methods have any more practical significance than those obtained with simpler and more portable apparatus, which can rapidly give a sufficiently reliable indication of the relative dust hazard. HISTORY OF DUST DETERMINATION IN ONTARIO The first record of mine-dust determination in Ontario is given in an article by Dr. J. H. Elliott,&apos; in which he records a few dust counts made with the Palmer spray apparatus. There were insufficient data from which to draw any definite conclusions or reasonably compare with present-day counts using the konimeter. The first konimeter dust sampling was started in the Porcupine district in 1926, using light-field counting without adhesive and with no sample treatment before counting. A method of semidark-field counting was used from about 1928 to 1931 and dark-field illumination was adopted permanently about December 1931. The konimeter has been continued as the principal means of dust sampling in the mines of Ontario, where South African practice has been adopted because in South Africa most careful study has been given the problem of silicosis, and very complete records of work done there are

Jan 1, 1937

SPEAKING generally, it may be said that leaching is the simplest method of recovering copper from its ores. Likewise it is perhaps the oldest method of treatment used by copper metallurgists of the modern era. Reliable records indicate that as early as 1752 cupriferous pyrite was leached in the famous Rio Tinto region in Spain. Though the manipulation was quite different from that in use today at Chuquicamata, New Cornelia, Inspiration, and Andes, it resembled that employed by Phelps Dodge at Bisbee, as described in Chapter XIV. Leaching consists of subjecting ore to the action of a liquid solvent or menstruum (usually an aqueous solution) which dissolves the major part of the soluble copper minerals. The resulting pregnant solution is drained off or otherwise separated from the residual ore; and the copper in the solution is then recovered by some appropriate means of precipitation. When sulphuric acid is the lixiviant, as is usual, the simplest procedure is to pass the copper-bearing solution through large troughs containing scrap iron. The iron displaces the copper in the solution, precipitating it as a slime coating the iron and varying in color -from bright copper to a dull black. This may be washed off at intervals, collected as a sludge, dried, and melted with a little fluxing material to produce reasonably pure copper. Usually, of course, the mud is sent to a smelter where most often its destination is the converter or reverberatory furnace. Modern practice uses precipitation on iron only as a complemental process to electrolytic precipitation or deposition, wherein the pregnant copper-bearing solution, acting as the electrolyte in a cell having insoluble anodes and copper cathodes, is depleted of the copper it contains. Cathode copper, 99.5 per cent pure, is produced ready for the market as refined copper, or for a simple process of melting, fire-refining, and casting in

Jan 1, 1933