Search Documents

By Raymond Mancha

The number of installations of propeller mine fans completed during the years of 1936 and 1937 is evidence of the increasing popularity of the propeller fan with the American mining industry. During the period from 1931 to 1936, there were several different low-pressure, low-efficiency propeller fans available, which filled a definite need in replacing inefficient centrifugal fans operated at comparatively low pressure by means of purchased power. Since 1936, however, the trend toward the propeller fan has greatly increased, as propeller fans are now available practically without pressure limitations and capable of efficiencies high enough to warrant replacement of efficient centrifugal fans in many instances. Few manufacturers of propeller mine fans base their fan-operating characteristics upon similar test methods, primarily because of inadequate facilities for testing in the factory and the need of a test code incorporating a calibrated duct or nozzle that makes possible the testing of large propeller fans quickly, accurately and without prohibitive expense and space requirements. As a result, fan manufacturers have resorted to various methods for testing large propeller fans in the factory, and different yardsticks have produced uncomparable and often inaccurate performance data. It is the purpose of this paper to describe and discuss in detail the test procedure of the Jeffrey Manufacturing Co., which has been proved both accurate and practical. Fig. 1 shows a plan, a side elevation and two end elevations of the test duct with a propeller fan of the exhaust type in place. Testing propeller fans exhausting permits greater accuracy than testing these fans blowing, because in the former uniform flow conditions are more easily established at Pitot tube stations where fan pressure and air-volume measurements are desired. Any residual rotation remaining in the air discharged from a propeller fan blowing into a test duct must be removed before an attempt is made to obtain accurate pressure and volume readings. Although various devices for straightening the air may be placed between the blowing fan and the volume-measuring station without resulting complications, uniform flow so obtained at the pressure-measuring station necessitates corrective calculations to compensate for duct resistance

Jan 1, 1940

By Jerry H. Service, F. L. Partlo

The following investigation was undertaken to develop a method for determining with reasonable accuracy the depth of overburdens of 100 ft. or less. Seismic methods seemed to offer good possibilities. The problem differed from that of the familiar salt-dome location in that the depth of overburden to be determined is much less than is encountered in oil prospecting. This means that a much shorter time interval must be measured with accuracy. Refraction methods seem at present to offer greater possibilities than reflection. The air sound persists for from 0.1 to 0.5 sec., because of echoes, and seismic reflections coming during this time are difficult to detect. A seismometer sensitive to vertical vibrations only offers possibilities and has been used here with some success. It is hoped that the application of this type of seismometer to reflection shooting in this region may be investigated still further. The apparatus used consisted of a carbon-button seismometer followed by a three-stage, transformer-coupled, vacuum-tube amplifier and a General Radio string oscillograph. Time marks are provided by a 1000-cycle, 600-r.p.m., synchronous motor provided with five spokes which intercept the light to the camera at 1/50 sec. intervals. This motor is driven by a two-stage vacuum-tube amplifier of 3 watt output, actuated by a tuning fork. The power supply for the seismometer amplifier is one 2-volt storage and one 45-volt B battery. The motor amplifier is powered by a 6-volt storage battery and 6 to 225-volt, 15-watt motor generator. The temperature-frequency characteristics of the tuning fork have been determined and for ordinary working temperatures the error in time that would be introduced is less than M millisecond for time intervals up to 100 milliseconds. The impact is produced by a sledge blow for surface distances less than 100 ft. and dynamite for greater distances. Two steel balls with wires attached form an electric circuit through a 1-ft. piece of railroad rail upon which they rest. When the rail is struck by the sledge the balls rebound, opening the circuit and indicating the time of impact by a break in the oscillograph record line as at A, Fig. 3. When dynamite

Jan 1, 1934

By B. M. Larsen

AN increasing amount of attention is being paid to the possible influence of oxygen, in its several modes of occurrence in steel, upon some of the properties of the metal; but clearly investigations along this line are unlikely to yield significant results until reliable analytical methods for the determination of oxygen have been established. This paper presents some results of a study of an improved Ledebur method which aims to determine a definite portion of the oxygen; namely; that which presumably is present in diffusible form in the. solid steel. These more or less preliminary results lead us to believe that the oxygen so determined has some significance; their presentation at this time will, we hope, stimulate discussion of, and focus attention upon, certain rather neglected aspects of the problem. Considerable work has been done recently on methods of estimating inclusions and on the vacuum-fusion method for oxygen; with results which, however, are of somewhat questionable significance. It is commonly presumed that the oxygen in a bath of molten steel in a furnace is present partly as a separate phase consisting of suspended particles of oxides or silicates, partly in solution, the latter being probably the more important. Upon addition of a deoxidizer, it reacts with some portion of the dissolved oxygen and precipitates it as additional suspended particles; the oxygen not eliminated in this way, which remains in solution in the liquid steel, may be regarded indifferently either as dissolved oxygen or as dissolved FeO. When the steel is poured, some of the suspended particles rise towards the surface, others remain trapped in the finished steel, appearing as nonmetallic inclusions in amounts corresponding usually to about 0.01 to 0.03 per cent 02 in the steel. The dissolved oxygen may be partly eliminated as CO during freezing of the ingot, but some remains either in solution or in part precipitated as FeO. Finished steels may thus contain oxygen in several forms: (1) In non-metallic inclusions which are probably quite insoluble in the solid metal at all temperatures; (2) in solid solution which at lower temperatures may be supersaturated; (3) in FeO particles produced by relief of this

Jan 1, 1932

By B. M. Larsen, T. E. Brower

An increasing amount of attention is being paid to the possible influence of oxygen, in its several modes of occurrence in steel, upon some of the properties of the metal; but clearly investigations along this line are unlikely to yield significant results until reliable analytical methods for the determination of oxygen have been established. This paper presents some results of a study of an improved Ledebur method which aims to determine a definite portion of the oxygen; namely, that which presumably is present in diffusible form in the solid steel. These more or less preliminary results lead us to believe that the oxygen so determined has some significance; their presentation at this time will, we hope, stimulate discussion of, and focus attention upon, certain rather neglected aspects of the problem. Considerable work has been done recently on methods of estimating inclusions and on the vacuum-fusion method for oxygen; with results which, however, are of somewhat questionable significance. It is commonly presumed that the oxygen in a bath of molten steel in a furnace is present partly as a separate phase consisting of suspended particles of oxides or silicates, partly in solution, the latter being probably the more important. Upon addition of a deoxidizer, it reacts with some portion of the dissolved oxygen and precipitates it as additional suspended particles; the oxygen not eliminated in this way, which remains in solution in the liquid steel, may be regarded indifferently either as dissolved oxygen or as dissolved FeO. When the steel is poured, some of the suspended particles rise towards the surface, others remain trapped in the finished steel, appearing as nonmetallic inclusions in amounts corresponding usually to about 0.01 to 0.03 per cent Oz in the steel. The dissolved oxygen may be partly eliminated as CO during freezing of the ingot, but some remains either in solution or in part precipitated as FeO. Finished steels may thus contain oxygen in several forms: (1) In non-metallic inclusions which are probably quite insoluble in the solid metal at all temperatures; (2) in solid solution which at lower temperatures may be supersaturated; (3) in FeO particles produced by relief of this

Jan 1, 1932

By Ivette E. Torres

World investment 10 all mineral and mining industry sectors is not available. However, partial information available provides some information useful for analysis. Information available in this section covers limited geographic information on investment in the steel industry, limited information for petroleum industry capital spending, and total U.S. foreign investment in comparison to the mineral-related sectors (tables 13, 14, and 15). Annual steel industry investment is available for the European Community, almost all countries within the European Free Trade Association (EFTA), Latin America, and other countries with significant mineral industries, such as Canada, Japan, and the United States. Although information was not available for 1992, data for 1991 indicate that for those countries aforementioned, total investment increased by 8 %. However, investment patterns were very different within the different groups of countries. While the European Community had a net increase of 12 %, dominated by an almost °40 % increase in Germany, EFTA member countries had a 26 % decrease in investment for the same period. Investment in EC countries was almost seven times that of EFT A countries. Japan's investment in the iron and steel industry, by far the largest of those available, almost twice that of the EC and almost four times that of the United States, increased by more than 20 %. In North America, investment in Canada and the United States decreased. Almost all of Latin America decreased investment in the sector. The notable exception was Mexico, with a 60 % increase. Changes in Mexico's investment policies of the recent past, its economic growth, and privatization of its iron and steel industry are some of the reasons for such an increase. The other country covered individually in Latin America, where investment in the iron and steel industry increased, although slightly, was Argentina. This limited information does not allow a comprehensive analysis of global industry trend, which in turn impacts many other mineral commodities, and with the transition in many countries within Europe and Central Eurasia that are now effecting the steel industries of the countries that were members of the U.S.S.R. and its CMEA partners, it is most regrettable that comprehensive and comparable data, both current and historic, on investment in this area are not available.

Jan 1, 1994

By T. Egleston

The necessity of using a refractory material capable of much greater resistance to chemical action and having a far higher melting-point than those which contain silica, which melt and sweat off in the furnace even when not exposed to bases forming with silica more or less fusible compounds, has led to a careful practical study of all those materials which contain very refractory bases. The results of these researches, extending over several years, and made on a very large scale in many of the largest works in Europe, are of the highest interest, not only considered as a step in the progress of the study of the materials themselves, but in the application of refractory materials to metallurgical uses in general. The result of the experience of the last seven years with these basic materials, as in general with all such substanccs, is that natural products cannot be used as such. They are either too uncertain in their quality, contain substances which may in certain cases be very injurious, or, when in a condition in which they might be used, are so rare as to become practically unavailable for employment on a large scale. The materials that may he used are therefore not only limited in number. but they must be prepared artificially. When the use of basic artificial material is further extended, no doubt the number of these substances will not only be greatly increased, but the methods of preparation will be both perfected and cheapened to such an extent as to permit their application in processes for which they have hitherto proved too expensive. The quantity of refractory materials required for making ingots will he from 130 to 150 Ibs. per ton, or between 6 and 8 per cent. of the metal produced. In an establishment producing 2000 to 3000 tons of steel per week, considerable space is required to handle the basic materials properly. It is proposed in this paper to briefly discuss these basic materials and their application in the only two metallurgical processes where they have as yet been applied. These are the basic Bessemer and the basic open-hearth process, known as the Thomas-Gilchrist processes.

Jan 1, 1886

By P. V. Faragher

A metal or alloy finds its place in commerce in proportion to its ability to serve certain purposes better and more economically than other materials. While there is some overlapping of the fields of application of the various metals under discussion in this symposium, each one has its uses for which it is especially adapted. While aluminum is the most recent of the metals to enter the field, the development of the industry has been based on its peculiar properties, by virtue of which new uses for non-ferrous metals have been created. There has been substitution of this new metal for other members of the group but there has been a far greater development in entirely new fields. In common with the other non-ferrous metals, aluminum is resistant to atmospheric corrosion. It also withstands the action of many of the common chemical reagents, strongly alkaline substances being the notable exceptions. The outstanding properties on which the application of aluminum is based are its low specific gravity and its ease of fabrication into the forms in which it is used. It is noteworthy that this property of specific lightness is retained in all the commercial aluminum-base alloys. This statement does not apply to aluminum bronze; this is more properly a copper-base alloy, since aluminum enters into its composition to the extent of only about 10 per cent. None of the commercial casting alloys of aluminum has a density exceeding that of the parent metal by more than about 10 per cent., and some are actually lighter. In the so-called "strong alloys" of aluminum in which strengths comparable to that of mild steel are developed by heat treatment, the greatest increase in density is only slightly more than 3 per cent., and one of these, also, is lighter than aluminum. This property of lightness combined with the desirable mechanical properties of the alloys, makes aluminum especially suited for parts of moving assemblies where saving in power, as well as a decrease in stresses resulting from inertia and vibration, are of importance.

By Y. C. Liu, R. H. Richman

From rolling textures of polycrystalline AgCl determined as a function of temperature, changes in the amounts of the individual textural components are correlated with temperature-dependent changes in glide geometry. The preferred orientations are influenced by the slip behavior as follows: 1) pencil glide, characterized by (110) slip directions and a greater participation in the deformation the higher the temperature, leads to a(012) fiber texture; 2) low-temperature deformation, primarily on (110) (110) systems, generates the {237}-(11, 9, 7) component; and 3) slip on {111}(110), comprising a significant portion of the room-temperature deformation, generates the {135}(211) and {110}(112) components. Typical re crystallization textures are also presented and briefly discussed. SPECIFIC relations between flow mechanisms in crystals and the individual orientations or components in deformation textures are necessary for a thorough understanding of the origin of such textures. Within each ordinary class of crystal struc- tures there is insufficient variety in the observed preferred orientations to permit direct and unambiguous correlation between flow mechanism and texture. A second approach to this problem is the correlation of textural changes with some known variation in glide geometry within one substance,1 In this paper, the latter approach is applied directly to a material in which there are distinct changes in the character of glide with changes in temperature. Silver chloride, although a nonmetal, is reported to exhibit slip,2,3 fiber textures,4 and rolling textures5,6 crystallographically similar to those of the well-studied fcc metals;7,8 in addition, there is a marked temperature sensitivity of the glide planes upon which flow occurs.3 Previous investigations of textures in AgCl unfortunately did not employ methods sufficiently sensitive to define possibly important minor components in the texture, nor did they utilize the temperature dependence of the glide systems. Thus, in order to clarify the effects of changes in slip mechanism, this paper reports a survey, using semiquantitative methods, of preferred orientations in rolled AgC1. Inasmuch as the influence of prior deformation texture upon preferred orientations after annealing is also of interest, some representative annealing textures are presented.

Jan 1, 1965

By Leonard W. III Joseph, William H. Buttermore

Noise control is an important consideration in the design and operation of coal preparation plants. It is essential to understand and control noise sources to provide a safe environment for operating personnel. The average noise exposure levels in a typical coal preparation plant generally range between 95 and 100 db. An operator should not be exposed to noise levels of this magnitude for more than 4 and 2 hr, respectively, according to MSHA (Mine Safety and Health Administration) regulations. The major noise sources in a coal preparation plant include noise from impacting the inside surfaces of steel chutes, vibrating screens, coal crushers, pumps, motors, fans, and blowers. The magnitude of noise varies considerably from one situation to another. NOISE EXPOSURE IN COAL PREPARATION PLANTS Noise regulations established by the Occupational Safety and Health and- ministration (OSHA) are accepted by MSHA relative to coal preparation plants. Fig. 14-43 shows a graph of the time of noise exposure in hours per day to which a worker can be exposed for each A-weighted sound level. According to this graph, a worker is permitted to spend 8 hr in a 90-db noise environment, but that time must be halved when the A-weighted sound level increases 5 db. The noise dosage a worker receives is determined by the ratio of the length of time the worker spends in a particular noise environment divided by the length of time he is permitted to spend in that environment. If the worker is exposed to several different sound levels, his total dosage would be the sum of each of the individual dosages. The equation for determining the dosage is: where C is the actual duration of exposure at a given steady state noise level and T is the noise exposure limit for the level present during the time C According to MSHA regulations, the dosage, D, should not exceed one (1) for any worker for a full day of work. As an example of typical plant noise levels, vibratory screens and crushers emanate noise levels in excess of 90 db at a distance of 3 ft (0.9 m) with no material flow. With material flow, noise level increases 1 to 10 db depending

Jan 1, 1991

By P. V. Faragher

A METAL or alloy finds its place in commerce in proportion to its ability to serve certain purposes better and more economically than other materials. While there is some overlapping of the fields of application of the various metals under discussion in this symposium, each one has its uses for which it is especially adapted. While aluminum is the most recent of the metals to enter the field, the development of the industry has been based on its peculiar properties, by virtue of which new uses for non-ferrous metals have been created. There has been substitution of this new metal for other members of the group but there has been a far greater development in entirely new fields. In common with the other non-ferrous metals, aluminum is resistant to atmospheric corrosion. It also withstands the action of many of the common chemical reagents, strongly alkaline substances being the notable exceptions. The outstanding properties on which the application of aluminum is based are its low specific gravity and its ease of fabrication into the forms in which it is used. It is noteworthy that this property of specific lightness is retained in all the commercial aluminum-base alloys. This statement does not apply to aluminum bronze; this is more properly a copper-base alloy, since aluminum enters into its composition to the extent of only about 10 per cent. None of the commercial casting alloys of aluminum has a density exceeding that of the parent metal by more than about 10 per cent., and some are actually lighter. In the so-called "strong alloys" of aluminum in which strengths comparable to that of mild steel are developed by heat treatment, the greatest increase in density is only slightly more than 3 per cent., and one of these, also, is lighter than aluminum. This property of lightness combined with the desirable mechanical properties of the alloys, makes aluminum especially suited for parts of moving assemblies where saving in power, as well as a decrease in stresses resulting from inertia and vibration, are of importance.

Jan 1, 1928

By Shiro Ban-ya, John F. Elliott, John Chipman

The activity of carbon in Fe-C austenite at 1150°C has been determined for concentrations up to about 2.1 pct C using the equilibrium: C + COz = 2CO; equations have been derived expessing the activity as a function of carbon content on the basis of twelve mathematical models. Several of these represent the data satisfactorily. ACCURATE information on the thermodynamic properties of austenite in the binary system Fe-C is needed as a basis for studies of transformation and precipitation in steels of all sorts, alloy as well as plain carbon. The many attempts to approach this problem through statistical thermodynamics require sound and dependable experimental data in order to evaluate the several models which have been suggested. In this paper we are concerned with the experimental determination of the activity-composition relation in austenite at the temperature of its widest range of stability, approximately the eutectic temperature (1153°C). Accurate investigation of the activity of carbon in austenite may be said to have begun with the work of Dunwald and wagner.' A more detailed study was carried out by R. P. smith2 on the two equilibria: More recent work on these two equilibria has been reviewed by Chipman,3 who pointed out the experimental hazards associated with studies of Eq. [I]. Studies of this reaction involve rather small values of the ratio these are susceptible to errors due to traces of moisture in the apparatus according to the reaction: Ellis, Davidson, and Bodsworth4 evaluated K, for their experimental temperatures and used desiccants to control water vapor pressure. While they were able in this way to obtain consistent values for K1 it cannot be said that all of the uncertainties of the method have been overcome. Results by both methods reported by Schurmann, Schmidt, and wagener5 appear to be consistent except at very low carbon content. Reaction [2] was employed in the experimental work reported here. It is to be recognized, however, that it is not applicable to projected studies of certain alloy steel compositions involving stable oxide-formers.

Jan 1, 1970

By Edwin R. Phelps

In the year 1900 about 212 million tons of bituminous coal were produced in the United States. Almost none of this was produced by surface mines (Fig. 1), because there was no large equipment suitable for stripping overburden at that time. By 1915 the surface mines had built up their capability largely through use of the steam shovel to the point that they produced 2.8 million tons of the nation's total production of 443 million tons. Over the intervening years between 1915 and 1970 surface mining provided a continually increasing percentage of the nation's bituminous coal, stimulated by the growing availability of giant surface mining machines, some of which are presently capable of removing 220 cu yd of earth with one bite of their mighty buckets. In 1970 the nation's surface mines produced 244 million tons of bituminous coal, over 40% of the total national production. On the other hand, the nation's underground mines hit a peak of 560 million tons in 1920, dropped to a low of 273 million tons in 1961, and are presently on a very slow rise. Environmental pressures generally oppose surface mining, and have forced coal companies to consider more underground mining in future planning. Also, since strippable reserves are decreasing in the eastern states, an increase in underground mining is expected over the coming years. However, in the western states there are enormous reserves to be extracted by surface methods. Why has surface mining increased, while underground mining has decreased? It's largely a matter of economics. The cost per ton is greatly reduced by surface mining because of the relative ease of obtaining the coal. Also, there is a much greater percentage of coal recovery-nearly 85% in surface mines within the minable area, as compared to an average of about 50% in underground mines. Much surface mining recovers coal that could not be extracted by underground methods because of coal bed thinness, or multiple beds close together, split seams, the nature of the roof, and other geologic conditions. What are some of the limitations of surface mining? First of all, with presently available machinery it is difficult to surface mine at depths

Jan 1, 1973

By R. S. James, E. J. Gleim

Not long after electrically driven equipment was introduced into coal mines it became apparent that the spark-producing parts, such as controllers and motors, required safeguards to prevent the ignition of mine gas that might come into their vicinity. Many of the early designs attempted to provide protective enclosures having ventila¬tion and relief for pressures if ignition should occur within. The principal feature of the Davy safety lamp, namely, the wire gauze, was employed widely for this purpose. Other devices were developed to reduce the temperature of products of combustion escaping through the protected openings to a value below that which would cause ignition of surrounding explosive atmospheres. Although many such devices performed their intended function satisfactorily under laboratory conditions they were not so satisfac¬tory when subjected to the rigorous conditions encountered under¬ground. Corrosion, mishandling, and accumulations of grease and dirt reduced or destroyed their protective qualities after a period of service in the mines. In the United States this has led to abandon¬ment of special devices in favor of what is called " total enclosure " which means that no regular provision is made for ventilation and release of pressure but rather that the housings or enclosures are built strong enough to withstand the explosion pressures without rupture. As a further protection the joints usually are made of broad, closely fitting surfaces. It is impractical to make such joints absolutely gastight in ordinary machine practice when provision must be made for partial or complete disassembly to facilitate ad¬justments and repairs. Therefore, when an explosion occurs within such enclosures flames may escape through the joints. If the latter are broad enough and not separated too widely, however, the flames will be cooled by contact with the metal surfaces (flanges) of the joints, by rapid expansion, or by both cooling and expansion, with the result that an explosive atmosphere surrounding the enclosure will not be ignited. This is termed " flange protection." In testing parts of cutting machines and other equipment for coal mines, with the ultimate object of approving the equipment for use

Jan 1, 1935

By Clarence A. Seyler

The technical difficulties of cutting thin sections of coal for examination by transmitted light have hitherto restricted the investigation of the important subject of the microstructure of coal to the few possessed of the requisite skill and time. Apart from this, the method fails with anthracites and other coals rich in carbon, owing to the opacity of the material. Occasional use of the method of polishing a surface, with or without etching, has been made, but it was not until Winter' published an account of his results that attention was seriously directed to the method. In May, 1923, a specimen of dull anthracite came into my hands; I tried Winter's method on it and the presence of megaspores and other vegetable structures became clearly visible. A preliminary notice was published by me;2 but I soon abandoned the use of Schulze's solution, having found that a mixture of chromic and sulfuric acids gave far better results. In the meantime Turner and Randall, in America, had independently developed the method of flame etching, as applied to anthracite, with great success. I have spent a year studying the method of chromic etching, which gives excellent results with bituminous coals and camels, as well as with anthracite. For anthracites, I have used the chromic method and Turner's method of flame etching, whichever was the more convenient or as a check one on the other. The polishing is done, according to metallurgical practice, by the use of a polishing machine and successively finer emery paper, followed by polishing on cloth moistened with a suspension of levigated green oxide of chromium, and a final rubbing on "selvyt" (a cotton velvet polishing cloth) moistened with alcohol. The polished sample is examined by reflected light with a 2/3 and 1/6 in. objective. Bituminous coals usually show considerable structure, and even anthracites show it faintly in places. The sample is then etched by immersion in a boiling solution made by adding 10 c.c. of concentrated sulfuric acid to 30 C.C. of a saturated solution of chromic acid; enough water is then added to dissolve

Jan 1, 1925

By W. L. Fink, R. S. Archer

This paper describes results obtained on aluminum-beryllium alloys and aluminum-beryllium-copper alloys in the preparation of which aluminum of 99.95 per cent. purity was used. The constitution and structure of the high purity binary alloys are given. The aluminum-beryllium eutectic occurs at 0.87 per cent. beryllium and 645° C. The solid solubility of beryllium in aluminum at 631° C. is 0.05 per cent, beryllium, and at room temperature is less than 0.013 per cent. beryllium. The densities of the alloys are substantially the same as the values calculated on the assumption that the densities of the elements are not changed by alloying. All of the alloys age-harden at room temperature after a solution heat treatment, and the chill cast aluminum-beryllium-copper alloys age-harden at room temperature without a prior solution heat treatment. Hardness and tensile properties are given. Salt spray corrosion tests on sheet specimens are described. It is shown that beryllium docs not lower the corrosion resistance of aluminum to salt spray provided the alloy has received a solution heat treatment. Commercial Possibilities of Beryllium Alloys Beryllium has certain properties such as low density, high hardness, good corrosion resistance, low thermal expansion and fairly good electrical conductivity, which would indicate that it is worthy of consideration as an ingredient of light alloys. It was not until recently, however, that beryllium could be produced with sufficient ease to encourage research along this line. The production of beryllium by electrolysis from a fluoride bath has now developed to the stage where it could be used commercially if there were sufficient demand for the element. Claims made in certain newspapers and technical articles in regard to thc strength and corrosion resistance of thc aluminum-beryllium alloys are not justified by experimental results. Moreover, beryllium is an expensive metal ($200 a pound at the time this work was done) and, on account of the nature of its ore and the consequent difficulty of its extraction, it will in all probability continue to be a relatively expensive metal, although the cost would undoubtedly be a great deal less than $200 a

By T. P. Lim, N. K. Davé

"A modified accumulator method was devised to measure surface radon flux from porous media. It consists of a collector hood type of accumulator with a homogenizer pump and a pressure balancer. The latter was used to compensate any pressure changes produced during sample withdrawal and hence eliminate additional radon transport from the media. Errors resulting from radon back diffusion due to decreasing concentration gradient with time across the interface were also eliminated by measuring radon concentrations in the accumulator for two different periods of time and calculating the true radon flux, J(o), from the solution of a time-dependent radon transport equation in the absence of any pressure and temperature gradients.Core samples from the observation site were also withdrawn for laboratory determination of porosity, moisture content, bulk and grain densities, Ra-226 source concentration and the fraction of Rn-222 produced in the void volume. The data were used to calculate the radon diffusion coefficient for the media.Using the present method, the true value of surface radon flux for an abandoned uranium tailings pile was obtained as J(o) = 2020.2 mBq/m2/sec (54.6 pCi/m2/sec) compared to the value J = 1406.0 mBq/m2/sec (38.0 pCi/m2/sec) obtained by the conventional method. The bulk diffusion coefficient of radon for the media was obtained as 1.2 x 10-7 m2/sec.IntroductionRadon-222 (hereafter called radon) released from uranium mill tailings is a continuous source of environment radioactivity in terms of its transport as an airborne gas and its decay products. The particulate daughter products readily attach to aerosols or dust particles and can further be transported by various other environmental pathways. Typical radon release rates from existing tailings piles vary between 740 and 14,800 mBq/m2/sec (20-400 pCilm2/sec), depending on the nature of the tailings material, moisture content, etc. The United States Nuclear Regulatory Commission (NRC) is proposing radon release rates of 74 mBq/m2/sec (2 pCi/m2/sec) above that of background."

Jan 1, 1982

By Rayner J. G, Leckie J. F, Moorehead C. F

The Coronation Hill gold-platinum-palladium prospect is located in the valley of the South Alligator River (latitude 13'35'S, longitude 132'36'E), about 80 kilometres east of Pine Creek in the Northern Territory. Coronation Hill was one of thirteen sites in the South Alligator Valley at which uranium was mined between 1955 and 1964 after initial discovery by the Bureau of Mineral Resources in 1953. Most of the mines were operated by United Uranium No Liability. The Sleisbeck mine 25 kilometres south of Coronation Hill was operated by North Australian Uranium Corporation and the group of mines at Rockhole about 20 kilometres to the north-west of Coronation Hill was operated by South Alligator Uranium No Liability. The uranium mine at Coronation Hill produced about 26000 tonnes of ore averaging 2.6 kg/t U308 with an estimated average gold grade of 10.4 g/ gold. Gold was commonly associated with the uranium mineralisation and was recovered at the gravity treatment plant at El Sherana. Gold was also recovered in 1986 by Pacific Gold Mines Limited by treating the tailings from the Moline and Rockhole uranium leach plants at a CIP plant at Moline. With the completion of uranium contracts in 1964 mining in the South Alligator Valley ceased. Exploration for uranium continued in the area during the 1960s and 1970s with no success. The Coronation Hill Joint Venture (BHP Gold Mines Limited 45 per cent, Pioneer Minerals (Gold) Pry Ltd 45 per cent, Notgold Limited 10 per cent)carried out the first exploration specifically targetted at gold in 1984 with the drilling of five vertical drill holes which indicated high potential for a substantial gold resource at Coronation Hill with no associated uranium. The Joint Venture has sub- sequently drilled about 25000 metres of diamond drill holes at Coronation Hill alone. Analytical results from 1985 drilling established that platinum and palladium were associated with gold. An indicated resource of 3.49Mt at 5.12g/t Au, 0.21g/t Pt and 0.56g/t Pd has been calculated using a lg/t Au cut off.

Jan 1, 1991

By David J. Akers

INTRODUCTION The variety of uses of coal and the wide range of characteristics of coal combine to produce a need for a wide variety of laboratory analysis. Coal is used to heat homes, produce electricity, and make coke for steel manufacture. It can also be used to produce both gaseous and liquid fuels as well as a variety of chemical products. Various applications may require specialized analytical procedures. For example, some of the procedures developed for the coke industry, such as expansion or contraction during carbonization, have little value to the power generation industry. Even for a single application, the type of analysis needed can depend on the source and/or general nature of the coal. This section provides a general overview of the types of analytical procedures commonly applied to coal from the perspective of the user of this information, not the producer. The intent is not to detail laboratory procedures, but rather to discuss the application of commonly used laboratory tests in coal preparation. Accordingly, laboratory procedures are categorized by type of information produced. Gravimetric Analysis Procedures that produce weight-based information (parts per million, pounds per cubic foot, or weight percent). Such analyses can relate to the coal's physical, chemical, or mineralogical characteristics. Volumetric Analysis Procedures that produce volume-based information (amount of a mineral present as a volume percent). The primary source of volumetric information is from petrographic analysis. Application Tests Procedures that measure some characteristic of coal that has been empirically related to some application or handling or processing step. Typically, these procedures attempt to duplicate some aspect of the commercial application at laboratory scale and may produce information in the form of an index. Applications procedures do not measure a single component of the coal but infer the combined effect of multiple components. Each class of information is discussed in the order listed. References are provided as a source of more detailed information. The American Society for Testing and Materials (ASTM) publishes the most inclusive reference to analytical procedures. This publication,16 which is revised annually, provides extensive information concerning generally accepted methods of laboratory analysis. ASTM also provides standards for sampling and some information concerning sample handling.

Jan 1, 1991

By John T. Cantwell

INTRODUCTION The process engineer usually is responsible for the design operating philosophy and/or day-to-day operations of a process. Since instrumentation is an integral part of the operation, it is essential that engineers understand the general capabilities of the different types of control equipment available. Many "noncontrol" engineers have become involved with instrumentation for machinery monitoring and control as well as other plant applications. The advent of the microprocessor has led to significant changes in control, both in systems configurations and man-machine interfaces. Today's concept is called simply "distributed control." What is distributed control? Distributed control is exactly what the name implies; the control system is divided into several functional segments and spread out to cover a process. The systems are distributed for physical, functional, and risk reasons. Before delving further into the specifics of distributed control, let's look at the evolution of control systems to see how we got here. Instruments initially were located near measurement and control points in the field. Operators physically had to go to the instrument to change setpoints or take measurements. As processes became more complex, it became evident that a central control area was required. This allowed an operator to monitor and control many variables. The operator's effectiveness was increased dramatically, which resulted in greater efficiency, better quality control, and lower personnel requirements. At the same time, plants became much larger, control applications became more complex, energy became expensive, and the industry became more competitive. All of these factors placed pressure on process and production engineers to get the most for the money. The result was a continuing push to put more instrumentation into a central control room to maximize efficiency and productivity and minimize manpower. This chapter deals in some detail with devices for measuring physical and chemical properties of coal; devices for measuring the weight and weight-rate of flow of coal; devices for the monitoring and control of conveyor systems, solids inventory, fluid flow, liquid level, density, and specific gravity. These instruments have a multitude of uses throughout a coal preparation plant. The discussions cover advancements in "on-line analysis," nuclear control devices, and distributed control using microprocessors, mainframes, and soft-

Jan 1, 1991

By B. B. Bucky

THIS investigation was carried on by means of models and the applica-tion of the principles of similitude to determine the effects of props, props and cribs and sand filling in longwall mining. The geologic structure and rate of face retreat were kept constant and the only change introduced was in the method of support. It is not felt necessary to repeat a description of apparatus, or to explain the fact that a scalar model made in all parts of the same material as the prototype will behave similarly to the prototype when rotated at speeds such that the centrifugal force is as many times the gravitational force as the prototype dimension is a similar linear model dimensions. The reader is referred to earlier papers1,2 for further information regarding these statements. All models were made of sandstone and were as in Fig. 6. They are composed of a 3/16-in. ore body bed A, overlain by a 3/16-in- bed B, a 3/8-in, bed C and two 1/8 -in. beds D and E. The model was rotated at ±2350 r.p.m. equivalent to a model ratio of 1268. It was worked back 1/4 in. at a time before being replaced in the centrifuge and again rotated. Table 1 gives model and prototype dimensions occurring in this discussion, the prototype dimensions being 1268 times the model dimensions. Figs. 1, 2, 3 and 4 were taken while the model was rotating at 2350 r.p.m. One was taken for each face retreat of 26.4 ft., but for obvious ,reasons all are not presented. Fig. 1 (A-E) shows the behavior of this type of structure with face retreats of 26.4 ft, and no artificial support. Fig. 2(A-E) shows the behavior of this type of structure where breaker and face props were used. The props were exceptionally strong, being of steel 1/8 in. square in cross section, and capped with 1/16 in. ± of soft wood and paper, to allow for roof deflection. The face props were

Jan 1, 1939