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By R. Loney, M. Militzer

There is a significant demand for new high strength steels with fine grain sizes for structural applications. One approach in this regard is to develop hot-rolled HSLA steels where refining the microstructure leads to increased strength levels, e.g. 700 MPa yield strength, that can be attained by suitable modifications of chemistry and processing. Here, an HSLA steel is investigated that contains 0.05wt%C-1.65wt%Mn-0.20wt%Mo¬0.07wt%Nb-0.02wt%Ti and approaches the above strength class. The ability to control and predict the mechanical properties of hot rolled steel depends strongly on the thermomechanical processes, which the steel undergoes. The final microstructure and, thus, the properties of the hot-rolled steel are a function of the austenite decomposition obtained during accelerated cooling on the run-out table and precipitation during coiling. The austenite-to-ferrite phase transformation under run-out table conditions has been investigated using a Gleeble 3500 thermomechanical simulator equipped with a dilatometer. The effects of cooling rate and initial austenite microstructure including the degree of work hardening on austenite decomposition kinetics and ferrite grain refinement have been quantified. Results show that grain refinement can be optimized by the presence of work hardened austenite and accelerated cooling. Based on the experimental results, a model is proposed to predict the transformation start temperature and the resulting ferrite grain size for run-out table cooling conditions.

Jan 1, 2004

By Robert E. Green, T. Hinton

The velocities of the three possible modes of elastic-wave Propagation have been calculated for single-crystal aluminum at 1-deg intervals throughout the standard steveographic triangle. The results are presented as isospeed contours. The deviations between the direction of maximum energy propagation and specirzen axes are presented as arrows drawn within the standard triangle. The orientation factors associated with dislocation nzotion on the primary slip system only and also on all twelve slip systenzs have been calculated for all three elastic waves. The orientation factors associated with a longitudinal standing--7aue resonant specivnen hazle also been calculated. The relevance of these results to ultrasonic attenuation measurements is discussed. DUE to the widespread use of ultrasonics in the investigation of the properties of solids a number of authors15 have discussed in detail the theory of elastic-wave propagation in solids. In this paper the modes of wave propagation are evaluated according to the procedure suggested by reeen' for the case of single-crystal aluminum at 1-deg intervals throughout the standard stereographic triangle. The wave speeds are presented in the form of contour diagrams within the standard triangle. The deviations between the direction of maximum energy propagation and the normals to the wave fronts are presented as arrows drawn within the standard triangle. The orientation-de pendent factors (orientation factors) associated with dislocation damping as derived in the preceding paper6 have been calculated for the case of aluminum at 1-deg intervals throughout the standard triangle. The orientation factors for dislocation motion on the primary slip system only and on all twelve slip systems are presented in the form of contour diagrams, for both the traveling- and the standing-wave conditions. The relevance of these results to ultrasonic attenuation measurements is discussed. ELASTIC-WAVE PROPAGATION Three waves can be propagated in a linear elastic homogeneous anisotropic medium. The velocity of propagation v of each of these waves in a medium of density p can be obtained from the determination of the eigenvalues and eigenvectors of the matrix equa- The A's are a series of moduli which are functions of the elastic constants cij and the direction cosines 1, m, and n of the specimen axis. In the case of cubic single crystals where there are only three nonzero elastic constants cll, c12, and C, the A's are, The solution of Eq. [I] will give the wave speeds (eigenvalues) and the direction cosines a, 0, and y of the particle displacements (eigenvectors). To obtain the direction of maximum energy flux requires the calculation of the energy-flux vector ET with com- w is the angular frequency, A, the amplitude, and v the velocity of the wave. The direction cosines a, b, and c of the energy flux vector are then given by

Jan 1, 1967

By I. M. W. Preston

A new shaft system was required to replace stope face for the North Section of Harmony Mine and to allow for systematic opening up of the North Eastern Section. Owing to the economic circumstances at the time the project started, it became vital to alter the original planning and to sink the service shaft first. The MATLA coal-sinking headgear, a novel presinking arrangement, allowed sinking to continue to 108 m concurrently with the erection of the permanent sinking headgear and sinking winders. It is estimated that this arrangement resulted in a saving of two months on the overall project.

Jan 1, 1983

By Dieter Loh, Mathias Knoll, Florian Werres

When a new tunnelling project starts, it has been a vital tradition for decades to cast and erect master rings horizontally on a flat surface to demonstrate the compliance with dimensional tolerances. Some tenders ask for the erection of two or even three rings upon each other or repeated master ring erections at intervals throughout the project. Especially for large diameters, this is a challenging and risky task for the workforce in the segment factory. A truck-mounted crane is often necessary, and in some cases it can take up to a week to complete a master ring. The concept of virtual rings has the potential to replace this tradition by assembling master rings digitally instead of physically. This is based on a best-fit approach, considering the 3D coordinates from laser tracker measurements of segments or segment moulds. Building a virtual ring, a sub-millimeter accuracy can be achieved, the alignment of neighboring circumferential and ring joints observed, and the fit of bolt holes checked. The traditional method, on the other hand, is discussed controversially despite the significant amount of work and risks—particularly as the horizontal position of the ring and absence of gaskets do not simulate the reality in the excavated tunnel. This paper will highlight the technical aspects of virtual rings, as well as their pros and cons, illustrated by a case study from London Thames Tideway where a total of 30 physical master rings could be replaced by virtual rings.

Jun 13, 2023

By Wei Sun, Jaewon Choung, Zhenghe Xu, Zhangming Cui

"High intensity conditioning has been demonstrated in a number of cases to enhance fine particle flotation. The improvement could be attributed to the enhanced formation of particle aggregates. However, the understanding of aggregation mechanisms remains rather limited. Recently, an enhanced particle aggregation was observed by the formation of small air bubbles resulting from high intensity agitations (HIA). In this study, a novel visualization system is designed and constructed for characterizing the fine bubbles formed in an HIA cell. The new design allows determination of gas evolution and bubble size distribution. With this system, the effect of dissolved air on fine bubble generation by HIA is investigated. The results show that HIA creates a favorable environment for the formation of gas nuclei and small size bubbles due to hydrodynamic cavitation.INTRODUCTIONFlotation is a dominant separation technique employed by mineral industry to recover the valuable mineral particles. However, in general, particles finer than approximately 10 µm are not effectively recovered by conventional froth flotation technique due to their low inertia and high specific surface area (Fuerstenau, 1988). Therefore, the fine particle flotation has been considered as the central challenge of flotation research. Substantial advances have been made for fine particle flotation from both a theoretical and technological point of view (Fuerstenau et al., 1979; Song and Lu, 1990; Subrahmanyam and Forssberg, 1990; Sivamohan, 1990; Sedat and Barry, 1991; Matis, 1995). High intensity agitation (HIA), for example, has found some success to improve fine particle flotation kinetics in laboratory tests (Chen et al., 1999a and 1999b; Valderrama and Rubio, 1998; Rubio and De Brum, 1994).The effect of mechanical agitation on flotation kinetics has been recognized for many years. In mid-1970s, Warren (1975) reported that increasing the shear rate of the pulp could improve the efficiency of ultra fine particle flotation. He attributed this improvement in flotation to the formation of aggregates. This concept of aggregation has been extended by Rubio (1978), and Bulatovic and Salter (1989), who employed high intensity agitation (HIA) method to promote aggregation. They found that HIA with the addition of collectors, frothers and suitable modifiers significantly improved both the flotation recovery and selectivity of ultra fine sulphide minerals. The improvement was explained by warren’s shear flocculation theory. Till now, many studies (Chen et al., 1999a and 1999b; Valderrama and Rubio, 1998) have been undertaken to improve fine particle flotation by HIA. However, most of these studies were focused on the relation between energy input and flotation efficiency. Less information was available for describing how the aggregate formed during HIA process."

Jan 1, 2006

By A. Wahib Khair

"This article first describes the impact of respirable dust on the health of miners in underground coal mines in the United States of America. Second, it identifies the major sources of dust generation, namely cutting tools in the road headings. Two surveys associated with cutting tools were made to determine the useful life of these cutting tools, and to determine the effect of cutting tool wear on productivity of the continuous miners. Third, this article presents the results of a series of experiments carried out in the Rock Mechanics Laboratories at West Virginia University in order to study: 3.1 the effect of cutting tool rate of wear on respirable dust generation, 3.1.1 the effects of rock materials on tool wear and respirable dust generation, 3.1.2 the effect of cutting tool geometric parameters on respirable dust generation, and 3.1.3 the effect of tip materials used in the cutting tool on respirable dust generation. Recommendations in regard to cutting tool design are also presented in this paper.Silica and coal dust are the two major elements affecting the health of underground miners. According to Lemen [1] approximately 1,500 men died due to breathing in silica dust in 1936 while tunneling through a mountain of mostly silica, near the town of Gauley Bridge, West Virginia. Coal dust resulting in lung diseases in one of the major health hazards in underground coal mines. The impact of black lung on miners, coal workers' pneumoconioisis (CWP), has ranged from 16,000 to 23,000 each year since 1982 [1].The trend for conventional mining to continuous machine cutting of coal, using more productive machinery, is inexorable. Intolerable level of dust generated at the face is an indication of inefficient coal/rock cutting by these machines. The federal goverment of the United States paid about 11.7 billion dollars in workmen's compensation to more than 470,000 miners with CWP [2]. Bieniawski and Zipf [3] reported that annual benefit payments were about 2 billion dollars. The enactment of the Health and Safety Act in 1969 in the United States triggered the initial investigation into coal cutting mechanisms and cutting tool designs.The surveys concerning the utilization of cutting bits and performance of continuous miners in underground coal mines were made in order to have first hand information about bit consumption and coal produ¬ction.Three types of used bits, commonly utilized cutting tools on continuous miners, were collected from different coal mines. The used bits were grouped into symmetrically and asymmetrically worn bits. Distribution analysis for weight loss and conical height loss was done. Details of the results are presented elsewhere [4], here the results are summarized briefly. The analysis shows that approximately 50% of the collected bits have worn asymmetrically, which shows that many bits do not rotate properly during cutting. Analysis of the distribution of bit wear showed that the degree of bit wear varied from one type to another and with mining conditions. On average, the weight loss of the used bits was 4% to 7% with a maximum of 31%. Correspondingly, the loss of the conical height was observed to vary between 11% and 23% with a maximum of 71%. Figure 1 shows typical data associated with some of the used bits."

Jan 1, 1998

By Robert D. Brown, Robert B. Parsons

"The mining industry may have survived the October 28 federal budget relatively unscathed, but the same certainly cannot be said of the petroleum sector-and many mining men are left wondering if their industry will be the next one to be singled out for special attention, as federal and provincial governments seek additional revenues and pursue nationalistic or provincial policies.Higher taxes, higher prices, a potpourri of ""incentives"", and a -""Canadianization"" policy mark the principal features of the new National Energy Program released by the government along with Finance Minister MacEachen's budget address.This month, Tax Notes examines the federal budget. with appropriate emphasis on the National Energy Program and its possible future implications forthe Canadian resource industries.IntroductionMost of the Canadian mining industry (tar sands miners excepted) heaved a sigh of relief on the evening of October 28, 1980, as Finance Minister MacEachen confounded the prophets in his budget address by not raising personal or corporation taxes and by making only relatively modest changes in the general tax system. Instead, he concentrated on a sweeping new energy policy. Unfortunately for that important sector of Canada's mining industry which is involved in mining the country's vast tar sands reserves, either now or in the future, the National Energy Program that was introduced along with the budget 'has serious implications."

Jan 1, 1981

By K. S. Raja, B. McNall, B. Pesic

"High-level radioactive wastes are stored in large underground storage tanks made of low-carbon steel. The wastes consist of concentrated solutions of sodium nitrate (NaNO3) and sodium hydroxide (NaOH), and the radionuclides 137Cs, 99Tc, and 90Sr. The corroding steel microenvironment may produce localized reducing or oxidizing conditions that affect the solubilities of the species such as Tc(VII) and Tc(IV), which in turn modifies the kinetics of corrosion of the storage tank. To understand the influence of technetate ions on the corrosion of steel, electrochemical polarization studies of A 537 steel samples were carried out in 1 M NaNO3 + 0 .05 M S r(NO3)2 + 0.1 M NaOH with and without addition of HReO4 at different temperatures (24 – 85 °C). The concentration of HReO4 was varied from 0.014 – 0.04 M.INTRODUCTIONAqueous processing of spent nuclear materials generates a large amount of high-level radioactive wastes. The wastes are primarily salt solutions of sodium hydroxide and sodium nitrate which also contain fission products such as 137Cs, 99Tc, and 90Sr. Among the high level radioactive fission products, Tc-99 is of great importance because of its high concentration, long half-life (2.1 x 105 years), high solubility in geologic waters as technetate, and rapid diffusivity through the geologic systems. The solubility of technetate ions varies depending on the oxidizing conditions prevailing in the storage containers. High level radioactive wastes are stored in single shell or double shell tanks made of low carbon steels such as ASTM type A15, A516-70 and A537. Most of the available literature on corrosion of steel in simulated radio active waste environments pertains to nitrate induced stress corrosion cracking (Subramanian & Mickalonis, 2005). The corroding steel microenvironment may produce localized reducing or oxidizing conditions that affect the solubilities of the species such as Tc(VII) and Tc(IV). Corrosion of steel and formation of Fe(II) and Fe(III) will affect adsorption and reduction of Tc species. The radioactive species can irreversibly be sorbed on the steel surface by oxidation of Fe(II) to more stable Fe(III) and fixed as less soluble Tc(IV)/Fe(III). The solubility of Tc species is also affected by other factors such as dissolved oxygen, local pH, temperature etc. How the corrosion behavior of steel will be affected in the presence of Tc species is not clearly understood.Cartledge (Cartledge, 1960) demonstrated that passivation of iron can be achieved in the presence of oxygen along with suitable inhibitor ions/molecules of the general formula XO4 n-, such as pertechnetate (TcO4 -). The pertechnetate ion is univalent. Since it is derived from a strong acid, no buffering action can be expected from this ion. The redox potential of the reaction (1) is 0.738 VSHE (Pourbaix, 1974)."

Jan 1, 2012

By P. W. Bennett, E. M. Elkin

A new technique for the recovery of palladium and platinum and sludge from go12 electrolyte eliminates many of the drawbacks of the zinc-dust cementation process. In the electrolytic refining of gold by the Wohwill method, the electrolyte contains about 100 gpl gold as AuCl, and 100 gpl free hydrochloric acid. Any palladium and platinum contained in impure gold dissolve and accumulate in the electrolyte. When their concentration approaches that of gold, it becomes desirable to discard the electrolyte and to recover the gold and the palladium and platinum. As practiced at Canadian Copper Refiners until recently, discarded electrolyte was treated with sulfur dioxide to precipitate the gold. 2AuCl3 + 6H2O + 3SO2 —2Au + 6HC1 + 3H2SO4 The gold precipitate was filtered off, washed with water, and melted with scrap anodes. The wash water was added to the gold-free filtrate and treated with zinc dust to cement the palladium and platinum. PdCl2 + Zn — Pd + ZnCl2 PtCl4 + 2Zn—Pt + 2ZnCl2 The precipitate was separated and sold as Pd-Pt concentrate, and the barren filtrate and wash water were discarded. The receipts of palladium and platinum at this company were too small to warrant their refining. The process suffered from a number of disadvantages. Handling the gold-free solution was disagreeable, as it was laden with sulfur dioxide even after blowing with air overnight. Subsequent treatment with zinc dust was also troublesome. A large excess of zinc dust was required. Spray, acid mist, and vigorous evolution of hydrogen accompanied the reaction. The Pd-Pt precipitate was grossly contaminated with occluded unreacted zinc and with yellow granules of sulfur, thought to be formed by the reduction of sulfur dioxide and its derivatives. Repeated boiling of the precipitate with hydrochloric acid and washing with water decreased somewhat, but did not eliminate, the zinc. After drying overnight, the precipitate hardened to a clinkerlike mass that was difficult to grind. Grinding, handling, and packing created heavy dusting. Even weighing in an analytical balance generated dust, indicating that the powder was easily charged with static electricity. The total palladium and platinum content of the powder varied from 56 to 72 pct, with an average of 65 pct. The powder dissolved in aqua regia with difficulty, leaving a small amount of insoluble residue. However, the main drawback of the process was the strongly hygroscopic Pd-Pt product. The powder showed a marked though erratic increase in weight and a corresponding decrease in assay on exposure to air, even during the course of laboratory analysis. Such changes were the source of disagreement between Canadian Copper Refiners and the buyers of concentrate. The cause of the change in weight is believed to be hydrogen, liberated by the action of zinc dust on hydrochloric acid. Some of this hydrogen was adsorbed so strongly by the precipitate that it could not be driven off during the drying. On exposure to air it oxidized catalytically, forming water. Experiments soon showed that the entire process of treatment of discarded electrolyte then in use would have to be changed. A small quantity of apparatus was moved into the gold room, and experimentation was held to a minimum compatible with the development of a new process. PALLADIUM AND PLATINUM PRECIPITATION It was thought that zinc could be replaced with a reagent other than a hydrogen-evolving metal. Semiquantitative experiments showed that platinum and palladium could be precipitated completely from the gold-free solutions with such well-known reagents as sodium formate, formic acid, formaldehyde, and paraformaldehyde. Sodium formate was the preferred reagent, since the other three are volatile and somewhat toxic. The gold-free solutions used were those saturated with sulfur dioxide, partly freed of sulfur dioxide by aerating overnight, completely freed by boiling, as well as strongly and weakly acidic, neutral, and alkaline solutions. The reactions are complex and can be represented by these over-all equations: PdC1, + HCOONa — Pd + NaCl + HC1 + Co2 PtCl4 + 2HCOONa — Pt + 2NaCl + 2HC1 + 2CCX, Strongly acidic solutions required as much as five times the theoretical amount of sodium formate as did solutions neutralized to pH 4.5. Increasing the pH decreased the consumption of

Jan 1, 1965

When a company has an effective hearing loss prevention program, everyone wins-the employers, the employees, and the safety and health professionals who implement the program. This guidebook is not about minimal programs that meet only the letter of the law. It is concerned with programs that are effective as well as efficient: those optimizing program elements that succeed in preventing hearing loss in a practical and cost effective manner.

Jan 1, 2006

By Andrew W. Jenike

The first significant studies of problems related to the handling and storage of bulk solids were reported at the end of the nineteenth century. Early work originated from the necessity to store large quantities of grain and was concerned mainly with pressures affecting the structural design of silos and bins. The Janssen formula (about 1898) and the work of Ketchum [1] form the highlights of that period. In more recent years, progress in mechanization, increasing plant capacities, and rising costs of labor have focused the attention of engineers on the problem of gravity flow of bulk solids. A great deal of work has been done with models, and flow patterns obtained in small scale bins have been described in several publications, for example [2, 3]. An attempt to develop a theory of flow of bulk solids was reported in 1954 [4, 5, 61 and presented to the in a paper [7] in the same year. AIME recommended the continuation of this work and, as a result, Engineering Foundation granted a sum of money to set up a Bulk Solids Flow Laboratory. Two and a half years ago the project gained the support of the University of Utah and a laboratory was set up on the campus of the University. This project is now in progress, it has received the support of the American Iron and Steel Institute and of Kaiser Engineers, Division of Henry J. Kaiser Company. The results obtained to date are summarized in this report.

Jan 1, 1959

By S Brochot

During the development of a mining project, samples are taken for metallurgical tests. The sample can be a composite sample made of material coming from a selection of various drilling products or a sample coming from a mining test. This sample can represent several tonnes of material which are analysed and split to be used in various tests.In the current case, a composite sample is dedicated to semi-autogenous grinding (SAG) pilot plant tests. The property of interest is then the size distribution of the material. The sample is mixed and a subsample is taken to measure the size distribution which is considered as the feed size distribution. Then the remaining material of the sample is divided in several subsamples for batch grinding tests at different operating conditions. The product of each grinding test is then analysed to measure its size distribution.The grinding performances are analysed at the light of the measured size distributions for feed and product. But what is the accuracy of the measurement of these size distributions? What is the variability of the feed knowing each feed is just a subsample of the initial sample?The Pierre Gy theory of sampling answers these questions.The current paper presents, through a real example, the calculation of the measurement error of the size distributions and the variability of the feed between the different tests. The uncertainties of the grinding performances are then calculated and their impact on the results interpretation is then analysed.CITATION:Brochot, S, 2012. Sampling for grinding pilot plant test - the effect of size distribution variability, in Proceedings Sampling 2012 , pp 127-134 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 21, 2012

By G. E. Blight

Several aspects of the behaviour and properties of backfills consisting of cemented cyclone underflow tailings are illustrated by means of examples, and guidelines are given on the optimization of the performance of cemented fills. The stretch characteristics of the geofabric used to contain freshly placed backfill are described, as well as the relationship between these characteristics and the forces acting on retaining barricades. The properties required to achieve a self-supporting, stable free face in cemented backfill are explored, and a graphic relationship between stable height and shear strength is presented and compared with that for uncemented (classified) tailings. After a description of the characteristics of Witwatersrand quartzite gold-tailings backfill and commonly used cements, the process of drainage and air entry into backfill is outlined. Following this, the early-age gain in strength and the shear-strength characteristics, as well as the compressibility characteristics of cemented backfill, are described. Two phenomena that are potentially damaging to cemented backfill are seismic effects (or blasting acceleration) and the closure that takes place during the curing of cement. Investigations show that neither of these phenomena is actually significantly deleterious to gold-tailings backfill: liquefaction does not Occur as a result of seismicity, and hydration of cemented fill is not significantly impeded by closure.

Jan 1, 1996

By F. M. Doyle, S. Duyvesteyn, K. Sreenivasarao

Toxic metals entering surface or ground water from sources such as metal finishing shop spills and abandoned mines can pose a significant threat to public health and the environment. Ion flotation and similar foam separation techniques show great promise for treating dilute, metal-contaminated solutions, and could also be used to treat effluents from many minerals and metallurgical processing operations prior to discharge. In ion flotation, an appropriate collector is added to the solution to form hydrophobic complexes with the metal ions. These metal-bearing species are then removed by flotation, usually with trace addition of a frother to stabilize the foam. In an effort to better understand the underlying scientific and engineering principles that determine the performance of ion flotation, the removal of Cu(II), Pb(II), Cd(II), Cr(II) and Cr(VI) has been studied using laboratory scale flotation columns in batch mode. The effects of the superficial air velocity, solution and froth height, nature of the collector, collector: metal-ion ratio, ionic strength and several frothers at low concentrations on the flotation kinetics are reported. Finally, results are presented on methods that might allow regeneration of collector and recovery of by-product metal from the foam product.

Jan 1, 1995

By R. H. Kolb

A long term project at Shell Development Co.'s Exploration and Production Research Laboratory has been the improvement of the accuracy and the ease of BHP measurements. As a result of these efforts, two complete and separate systems have now been built for the automatic logging of BHP variations. The first of these is a small-diameter instrument suitable for running through production tubing on a single-conductor well cable. During the development of this instrument, as much emphasis was placed on providing a high degree of usable sensitivity and repeatable accuracy as on obtaining the advantages of surface recording. The second system combines the benefits of automatic, unattended recording with the convenience of a permanently installed Maihak BHP transmitter.' THE CABLE INSTRUMENT For many years the standard instrument for BHP determination has been the wireline-operated Amerada recording pressure gauge or one of several other similar devices. This gauge records on a small clock-driven chart carried within the instrument, and although relatively precise readings from the chart are possible, they are difficult to ob-tain. a Both the maximum recording time and the resolution of the time measurements are limited by chart size, and when a slow clock is required for long tests, the precision of the time measurement is often inadequate. Since it is impossible to determine the data being recorded until the gauge has been returned to the surface, wasted time often results when a test is protracted beyond the necessary time or when it is terminated too soon and must be re-run. Clock stoppage or other malfunctions which would be immediately apparent with surface recording remains undetected with down-hole recording; the test is continued for its full term with a consequent loss in production time. As new uses for subsurface pressure data evolved, the shortcomings of the wireline instrument became increasingly apparent, and the concurrent development of a surface-recording pressure gauge and the associated high-pressure well cable service unit' was undertaken. Description of the Instrument Because of its ready availability and advanced degree of development, the Amerada bourdon-tube element was chosen as the basic pressure-sensing device. This element converts a given pressure into a proportional angular displacement of its output shaft, and a suitable telemetering system was designed to measure accurately the extent of this displacement and to transmit the measurement to the surface and record it. The telemetering system furnishes a digital record printed on paper tape by an adding machine-type printer. The present arrangement provides a resolution of one part in 42,000 over the angular equivalent of full-scale deflection, giving a usable sensitivity of better than 0.0025 per cent of full scale. An additional refinement simultaneously records on the tape the time or the depth of the measurement, also in digital form. When the instrument is placed in operation, an adjustable programer can be set to initiate a read-out cycle automatically at selected time intervals. When subsurface pressures are changing rapidly, readings may be recorded as frequently as once every 10 seconds; when pressures are more nearly stabilized, the period between readings may be extended to as much as 30 minutes. Because the instrument is surface-powered as well as surface-recording, the maximum period of continuous logging is (for all prac. tical purposes) unlimited. The subsurface instrument is a tubular tool, 1 1/4-in. in diameter and 6.5 ft in length, operating on 12,000 ft of conventional 3/16-in. IHO logging cable. The transmitting section, mounted above the bourdon-tube element in place of the regular recording mechanism, contains no fragile vacuum tubes or temperature-sensitive transistors. This unit has been laboratory-tested to 1 0,000 psi and 300°F and has performed dependably during a number of field operations. The down-hole transmitting arrangement can be fitted to any standard Amerada pressure element, regardless of range and with no modification of the element itself. Calibration To obtain a repeatability commensurate with the sensitivity and resolution of the instrument, it was necessary to develop a special calibrating technique. The manufacturers of the Amerada recording pressure gauge claim an accuracy of only 0.25 per cent of full scale, which is a realistic figure for normal calibrating and operating procedures. An exhaustive investigation was made of the errors inherent in the bourdon-tube element, itself, independent

L. S. Austin, Denver, Colo. (communication to the Secretary) : Mr Hartman says (p. 4 of the pamphlet) that the penetration of air into the crucible of the blast-furnace " is, of course, a function of the diameter of the nozzle." To this I would emphatically take exception. Fig. 1 represents a vertical ideal section of tuyere, cruciblewalls and charge, immediately at the tuyere, in which the currents of air are represented, both in quantity and in direction, by the tortuous black-lines emanating from the nozzle-opening and passing through channels of the least resistance. As an electric current, flowing by various conductors to a common point, is carried in quantity inversely as the resistance of those conductors, so here the air ramifies through the most open cavities or channels, relatively little of it passing where the resistance due to fine materials is great. This figure represents the course of currents in the vertical plane only. As a matter of fact, they pass away in every plane, as opportunity offers. The effect of blocking or decreasing the area of the nozzleopening would certainly only decrease the quantity of air entering by that particular tuyere, without assisting penetration. The large channels (b, b, Fig. 1, for example) would still carry the larger part of the air, while again the smaller channels (a, a, a) would continue small and take no larger percentage of the air than before. These channels momentarily change, however, with the slow descent of the coke. Further on (p. 5), Mr. Hartman describes the dispersive effect of a single lump of fuel. He has only to conceive the entire spaces before the tuyere-nozzles as filled with such lumps, in order to parallel the condition of affairs I have just explained. It is where the large pieces of the charge come down, that the mass is the most open, and the blast passes most freely. On the other hand, wherever the fine ore collects combustion proceeds slowly, because of the smaller supply of air. The

Jan 1, 1899

Depressed prices for minerals will force the mining industry to became more efficient. The continuous conveying of pit product is one area in which savings can be made. Conveyors are available, or can be adapted to provide the flexibility and reliability required. Each conveying system will need to be custom designed to suit the particular requirements of the mine. The Australian mining industry must take the initiative and accept the challenge of the new technology.

Jan 1, 1986

By Jon C. Volkwein

The U. S. Bureau of Mines investigated a method of using inert gas to prevent the formation of explosive gas mixtures in auger highwall mining of coal. A combination of gasoline and diesel engine exhaust gases was introduced into the auger drill hole using a short section of pipe located at the collar. Gas samples were taken and analyzed on site with infrared detectors for oxygen, carbon dioxide, methane, and carbon monoxide. Evacuated bottle samples were also taken and analyzed by gas chromatography at the Pittsburgh Research Center. These gas results were analyzed for explosibility. Personal exposure to carbon monoxide was also monitored. The highest methane level observed was 9.55 pct. The Inert gas levels, (carbon dioxide and nitrogen) were sufficiently high to prevent any ignition of the methane. Results showed that for all conditions during mining, gas concentrations were non-explosive. The maximum personal time weighted average sample for carbon monoxide was 20 ppm. This system provides a safe, inexpensive, simple method for preventing explosions during auger mining. INTRODUCTION The auger highwall mining method is an effective method to recover coal from a reserve when removal of the overburden by surface mining equipment becomes uneconomical. In this method of mining, a horizontal auger enters the coal seam from the surface mine bench under the highwall and the coal is drilled in a series of parallel holes. Historically, coal mined from the surface is relatively shallow, and over time, methane associated with the coal has dissipated through the surface. In most circumstances, little methane has been found associated with auger mining. However, mining technology has enabled surface mining of deeper reserves of coal. Furthermore, environmental constraints have forced the highwall extraction method to be used to remove coal under wetlands, further increasing the chances of encountering methane. Recently incidents of methane explosions at a few auger mining operations have resulted in injuries and increased testing for methane at the collars of auger holes. The fuel source of the reported explosions was not necessarily limited to methane, but may also have involved coal dust. The Mine Safety and Health Administration (MSHA) met with the Bureau to discuss what technology might be available to enable the safe resumption of mining. The discussion included the difficulty of ventilating through the solid shafts of the augers, that steel bits probably created the ignition source, and that perhaps inerting the holes with low oxygen and high carbon dioxide concentrations from the machine's diesel exhaust was a potential solution. Considering the ventilation aspects of the problem, it was not clear If ventilation could be reliably established. If some degree of ventilation to the front of the mining head is achieved, it may combine with methane to bring the hole atmosphere from a rich, nonexplosive mixture to an explosive mixture. Furthermore, it may not prevent a dust explosion in such a mining configuration. Lack of access through the shafts of auger type mining machines further limits the ability to add water or air to cool bits to prevent an ignition source from developing. Either of these approaches would also be expensive. The process of mining coal In an inert atmosphere has been considered in the past, but to our knowledge, never implemented (Department of Interior, 1970). Clearly, implementation in underground mining would be more complicated. On a mine bench open to the atmosphere, however, adding inert gas to the mining head could provide a quick, feasible method to prevent explosions at auger highwall mining operations. Also the problem of how to move the inert gas to the cutting head of the machine had to be considered. Preventing explosions on auger mining machines using inert gas requires three primary considerations: first is the source of inert gas; second, placing the inert gas at the cutter head; and third, monitoring the hole atmosphere. Any gas source having an effective inert gas concentration of 34 volume pct or greater will prevent methane from Igniting (Zabetakis, 1965). Sources of inert gas considered for this application included liquid nitrogen, modified shipboard inert gas generators (for hydrocarbon shipping and transfer), jet turbine engine (Paczkowski, et. al., 1982), the auger's diesel engine and a gasoline engine. Operation cost, purchase cost and availability limited our testing to the diesel and gasoline engines. This work tested each engine, separately and combined. To ensure effectiveness, both company and enforcement personnel need to know how to monitor the condition of the inerted hole. Measurements at depth inside the hole are possible by remote sampling through rigid tubing, but this method is Impractical for routine monitoring. Continuous monitoring of the exhaust gas stream is an alternative. The U. S. Bureau of Mines evaluated an inert gas system at an auger mining operation at a surface mine near Owensboro, KY. Coal was mined from the Number 9 Coalbed in Henderson Co. KY. Tests were conducted in January and March of 1992.

Jan 1, 1993

By T. V. Vijaya Kumar

Most of the iron ore washing plants set up in India consist of sizing of the ore by dry / wet screening, washing and classification by screw classifiers followed by multi-stage hydrocycloning of screw classifiers? overflow. The underflow of the hydrocyclones forms the concentrate which is used for pellets making. As the cut-point of hydrocyclones is generally at 20 microns, relatively lower diameter cyclones in a cluster with parallel feeding are used. This is found to, often, result in choking of the spigots, at times, by extraneous material as well reporting along with the slurry. It is observed to lead to sub-optimum performance of the cyclones with loss of iron values into cyclone overflow and thereafter into tailings. Analysis of data of an operating beneficiation plant (Beneficiation Plant - 1, BP - 1) of M/s Jindal South West (JSW) Steel Limited, Karnataka, India over a period of one year indicated that weight recovery of the concentrate from two-stage hydrocycloning was 45% (with respect to feed to the cyclones) and assaying 63.43% Fe, 4.43% SiO2 and 2.32% Al2O3. CSIR - National Metallurgical Laboratory - Madras Centre (NML - MC), India developed flotation process for processing screw classifier overflow with a view to improve the recovery of ultrafine iron values from it. Detailed investigations at laboratory scale flotation column and on-site pilot plant trials proved that the production of the concentrate and productivity of the plant could be enhanced by adopting reverse cationic column flotation technology. It was established that a typical screw classifier overflow analyzing 60.54% Fe, 5.95% SiO2 and 3.67% Al2O3 could be upgraded to 64.21% Fe, 2.64% SiO2 and 2.20% Al2O3 with 82.7% weight and 84.7% Fe recovery. This translates into an increase of 80% in weight recovery of the concentrate compared to what is being obtained, at present, by two-stage cycloning. It had an added advantage of reduced SiO2 in the concentrate. Thus, SiO2 in the final concentrate could be reduced to 2.64% from 4.43% by adopting column flotation. The concentrate so generated meets the stringent specifications, especially in terms of alumina in it(should be less than 2.50%) for pellets making. Later, JSW Steel Limited set up the flotation plant in BP - 1 based on the process developed by NML - MC and was commissioned in 2010. Keywords: iron ore, washing, ultra fines, alumina reduction, column flotation

Sep 1, 2012

By J. C. Bowling

The services provided by consulting engineers to the mineral process industry are briefly described. The organization of a multi-discipline consulting firm is outlined. Finally, the role of a consulting engineering firm is amplified by a description of its activities in the design and construction of a mineral process plant from inception to start-up.

Jan 1, 1978