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By Paul Billingsley, Augustus Locke

The mining districts of the first order' of the western United States (and borders) are those named on Fig. 1. These fall into four groups: (1) in the eastern outliers of the Rocky Mountain system; (2) in the Rocky Mountain system itself; (3) in the Great Basin; and (4) in the Sierras and Coast ranges. Of these four groups, the first three are almost entirely of Tertiary age and are within a belt of compressive folding which we shall call the Rocky Mountain-Great Basin thrust arc. The backbone of this belt is shown by the line BAC. The position of the ore districts in this belt indicates a conformance to linear elements of the continental pattern. These are additional to the peripheral elements emphasized by Butler.2 Nature of the Thrust Arc The thrust arc separates regions of contrasted kinds. To the east of it are flat-lying plateaus interrupted by earlier mountain folds; to the west, sunken basins, in which block-faulted ranges lie like an anchored fleet in a sea of desert wash or lava. The. cross-sections are as shown in Fig. 2. The backbone of the belt is the upward and eastward moving block represented by the Glacier Park, the Wasatch, and the Virgin mountains, successively. The structure represented on these sections is the culmination of events which began far back in geologic time and throughout which a contrast has existed between the regions east and west of the backbone line. Before the Pennsylvanian, as Fig. 3 shows, there was a shallow shelf on the east and a deep marine trough on the west; after

Jan 1, 1935

The mining districts of the first order' of the western United States (and borders) are those named on Fig. 1. These fall into four groups: (1) in the eastern outliers of the Rocky Mountain system; (2) in the Rocky Mountain system itself; (3) in the Great Basin; and (4) in the Sierras and Coast ranges. Of these four groups, the first three are almost entirely of Tertiary age and are within a belt of compressive folding which we shall call the Rocky Mountain-Great Basin thrust arc. The backbone of this belt is shown by the line BAC. The position of the ore districts in this belt indicates a conformance to linear elements of the continental pattern. These are additional to the peripheral elements emphasized by Butler.2 Nature of the Thrust Arc The thrust arc separates regions of contrasted kinds. To the east of it are flat-lying plateaus interrupted by earlier mountain folds; to the west, sunken basins, in which block-faulted ranges lie like an anchored fleet in a sea of desert wash or lava. The. cross-sections are as shown in Fig. 2. The backbone of the belt is the upward and eastward moving block represented by the Glacier Park, the Wasatch, and the Virgin mountains, successively. The structure represented on these sections is the culmination of events which began far back in geologic time and throughout which a contrast has existed between the regions east and west of the backbone line. Before the Pennsylvanian, as Fig. 3 shows, there was a shallow shelf on the east and a deep marine trough on the west; after

Jan 1, 1935

By Augustus Locke, Paul Billingsley

The mining districts of the first order' of the western United States (and borders) are those named on Fig. 1. These fall into four groups: (1) in the eastern outliers of the Rocky Mountain system; (2) in the Rocky Mountain system itself; (3) in the Great Basin; and (4) in the Sierras and Coast ranges. Of these four groups, the first three are almost entirely of Tertiary age and are within a belt of compressive folding which we shall call the Rocky Mountain-Great Basin thrust arc. The backbone of this belt is shown by the line BAC. The position of the ore districts in this belt indicates a conformance to linear elements of the continental pattern. These are additional to the peripheral elements emphasized by Butler.2 Nature of the Thrust Arc The thrust arc separates regions of contrasted kinds. To the east of it are flat-lying plateaus interrupted by earlier mountain folds; to the west, sunken basins, in which block-faulted ranges lie like an anchored fleet in a sea of desert wash or lava. The. cross-sections are as shown in Fig. 2. The backbone of the belt is the upward and eastward moving block represented by the Glacier Park, the Wasatch, and the Virgin mountains, successively. The structure represented on these sections is the culmination of events which began far back in geologic time and throughout which a contrast has existed between the regions east and west of the backbone line. Before the Pennsylvanian, as Fig. 3 shows, there was a shallow shelf on the east and a deep marine trough on the west; after

Jan 1, 1935

By R. H. Walpole, J. M. Kane

IN all probability the mining and metallurgical industry as a whole can demonstrate a larger ecorlomic return from installation of dust-control equipment than any other major industrial group. This fact has partially accounted for the marked increase of dust-control installations made during the past decade. While the primary objectives for installation of dust-collecting systems are improved working and operating conditions for men and equipment, the fact that an economic return can be anticipated on salvageable materials is an added advantage which shows in partial or complete equipment write-off. The conditions apply to most phases of the mining, milling, and smelting industry, both non-metallic and metallic. As with any mechanical devices, selection of suitable dust collector equipment involves evaluation of available products with characteristics most nearly meeting conditions of the application at hand. When there is valuable product to be collected, and/or when there are possibilities of air pollution or public nuisance, collector selection is often guided by the maxim of "highest available collection efficiency at reasonable cost and reasonable maintenance." A brief review of dust collector designs will permit outlining of major characteristics of each group. Final selection will involve detailed data against a background of the problem under consideration. The dry centrifugal collectors, see Fig. 1, represent a group of low cost units with minimum maintenance. They are subject to abrasion under heavy abrasive dust loads and to plugging with moist materials. Efficiency drops off rapidly on particle sizes below the 10 to 20 micron group. Because of the large amounts of —10 micron particles in most mining dust problems, they will normally be used as primary collectors and will be followed by high efficiency units. This combination is cspecially popular where the bulk of material is desired in a dry state with wet collection indicated for the final cleanup portion. In remote plant locations, dry centrifugal~ can be used alone if product in dust form has no value or if dust loading is light enough to eliminate a nuisance in the plant area. Where high efficiency dust colleotion equipment must be selected, choice will normally involve fabric arresters, wet collectors, or high voltage Electro-Static precip-itators. Fabric arresters, see Fig. 2, rely on the passing of dust-laden air at low velocity through filter fabric. Velocity ranges from 1 to 3 fpm for the usual installation and may be as high as 10 to 20 fpm in arrangements where automatic frequent vibration or continuous cleaning of the filter media is employed. Fabric is normally suspended in either stocking type or in an enlvelope shape. Collection efficiency is excellent even on sub-micron particle sizes. Equipment is bulky, must be vibrated to remove the collected dust load, and is restricted in applications from temperature and moisture standpoints. Condensation of moisture on the fabric filter mcdia causes plugging of the passages with great reduction in air flow. Temperatures for the usual medias of cotton or wool are 180" and 200°F maximum, although the introduction of synthetic materials such as nylon, orlon, and glass cloth have increased the possibilities of this type of collector for higher temperature applications. The wet-type collector may employ a number of different principles so that entering dust particles in the gas stream are wetted and removed. Principles usually include impingement on collector surface or water droplets, often in combination with centrifugal forces. Variety of wet collector designs is indicated by typical collectors illustrated in Figs. 3 and 4. Collection efficiency is a function of the particular design, although the better collectors will have high collection efficiency on particles in the 1-micron range. Wet collectors have the advantage of handling hot or moist gases, take up small space, and eliminate secondary dust problems during the disposal of the material. At times collection of the material wet is a disadvantage. Wet collectors may also be subject to corrosion and freezing factors. The high voltage Electro-Static precipitator, see Fig. 5, is probably the most expensive type of high efficiency collector. It finds its applications generally in problems in which collectors previously discussed cannot be employed. Its collection efficiency is based on its design features and can be excellent on the finest of fume particles. Material is normally collected dry. Gas temperatures are of no great concern as long as condensation does not occur within the dry type of precipitator and the temperatures do not exceed the limits for materials used in its construction. As with the fabric arrester, provisions

Jan 1, 1954

By J. S. Osoba, J. G. Richardson, F. M. Perkins

Laboratory experiments have shown profound diffcrences in the behavior of so-called "fresh cores" from the East Texes field and of the same cores after ex~ractio~l with organic solvents. The residual oil satura/ion remaining after waterflooding fresh cores was appreciably lower than the corresponding saturations after flooding extracted cores. This behavior was also reflected in the water-oil relative permeability-saturatiorl relations, which were more favorable for high oil recovery from the fresh cores. These differences were evident not only in the amount of residual oil left after wafer flooding, but also in the saturation water remaining in the core after displacernent by oil. Residual water saturation after displacernetzt of water by oil was higher in the fresh cores than in the extracved core,. Capillary pressure-saturation relations were also different for the fresh crnd extracted cores. Imbibition experiments indicated that both fresh and extracted Bast Texas cores imbibed water spontarteOLISIY, but- the rate of imbibition of water was higher for samp1es after. extraction than it was for fresh core. material. INTRODUCTION Several years ago a series of waterflooding tests was made in the laboratory on a number of Woodbine core samples from the East Texas field. These samples had been stored in containers open to the air and were extracted with organic solvents before they were subjected to the laboratory tests. After water flooding, the residual saturation of kerosene, which was the oil used in the tests, was found to average about 30 per cent. This saturation was higher than expected. In investigating the circumstances which might have been responsible for such a high residual oil saturation, attention was given to possible changes in wetting properties of the rock brought about by the procedure employed in extracting the cores. Preliminary results indicated that the explanation for the high residual oil saturation lay in the wetting behavior of the cores, though what effect extraction had on this behavior was not clear. In consequence, the work described in this report was undertaken in an attempt to investigate the mechanism responsible, and to ascertain the actual residual oil saturation to be expected in the reservoir after water flooding. It was soon found that there were profound differcnces in the behavior of so-called "fresh cores" from the East Texas field and of the same cores after extraction with organic solvents. These differences were evident not only in the amount of residual oil left after water flooding, but also in the saturation of watet remaining in the core after displacement by oil. The complete explanation of this behavior is not yet apparent. The description of work and results described in following sections, therefore, must be considered as an interim report presenting facts which must await additional information before they can be fully interpreted.

Jan 1, 1956

By K. H. Nimerick, G. P. Laflin

Laboratory data and field tests indicate that substantial losses of valuable coal can be caused by wind erosion. Wind tunnel tests show the effects of wind velocity and particle sizing on the amount of coal lost while in transit. Different coals were evaluated to determine the variables associated with wind erosion. The erosion losses can be substantially reduced by using a binder, or crusting agent, to consolidate the surfaces of the coal into a solid mass which resists erosion. This not only reduces economic loss but minimizes polllution.

Jan 1, 1980

By H. I. Aaronson, S. M. Kaufman, G. M. Pound

WHETHER the carbides associated with bainite precipitate from the ferritic component of bainite, as originally suggested by Davenport and Bain, or from the adjacent austenite at aus-tenite:ferrite boundaries, as proposed by Hultgren, 2 remains in dispute.3-5 A recent metallographic investigation in this laboratory has shown that the bainitic carbides formed in a plain carbon hypo-eutectoid steel nucleate entirely within ferrite at higher reaction temperatures3 and in both ferrite and austenite at lower temperatures." The present investigation was undertaken to ascertain the effects of alloying elements on the nucleation sites selected by bainitic carbides. The compositions of the steels studied were as shown in Table I. Specimens of these steels were

Jan 1, 1958

By Robert U. King

The Climax Molybdenum Company's mine is situated on the Continental Divide at Fremont Pass in Lake County, Colorado. Elevations at the mine range from 11,000 it. to over 12,000 ft. The ore body is on the south flank of Bartlett Mountain, a prominent peak in the Ten Mile Range. A horizontal section of the mine, such as the Phillipson level (Fig. I), shows the outer ore zone as an annular ring varying in width from 300 to 800 ft., surrounding barren silicified rock. In vertical section the outer ore zone is dome shaped (Figs. 2 and 3), the apex of which is truncated at the surface by glaciation, exposing part of the ore body. The outer ore zone overlies the barren core and is itself overlain on the flanks of the dome with unmineralized rock. An ore zone of similar shape underlies the barren core of silicified rock, known as the Central Ore Zone (Figs. 2 and 3). Molybdenite is distributed uniformly through a zone of moderately silicified granite, schist and quartz monzonite (early) porphyry, around a highly silicified core. The molybdenite occurs in veinlets associated with fine granular quartz and pyrite, replacing altered and fractured granite, schist, and porphyry, and as coatings on numerous fractures cutting these rocks. Intense fracturing of all rocks is a characteristic feature of the Climax ore body. Most fractures are mineralized and no longer represent planes of weakness. Much fracturing is postmineral, however, and these fractures are generally filled with sericite or gouge, or remain as unmineralized joints separating otherwise massive rock into blocks of various size. Study and Mapping of Caving Characteristics Important differences in the behavior of caving of various blocks of ore at Climax have been recognized, involving arching of the rock over caved stopes, tendency of caved rocks to funnel, and size of caved rocks. Also, new problems have arisen associated with future mining on the Phillipson level, and may occur with proposed development of lower levels, such as excessive stress on mine pillars caused by large masses of overlying stable rock, and higher costs in maintenance of mine workings in soft, weak rock. To explain the differences and to provide solution for these problems, a study of geologic structure was undertaken early in 1944, to determine whether it would be possible to map cavability of rock from physical features exposed in mine workings and in diamond-drill cores. A comparison of known caved areas was made and rocks were classified structurally according to strength or degree of cavabil-ity. As nothing of this nature had been done before at Climax, the approach to the problem was rather indefinite. Several trials were made with negative results, but collectively indicated a suitable method. This was to examine all mine workings and diamond-drill cores, record-

Jan 1, 1946

I have attended these meetings, every year, since 1926 and have served on both the Pittsburgh and the National Executive Committees, so that I am fully aware - of the ruling of this organization regarding, "No Papers by Vendors". Since I am now classified as a VENDOR, I wish to express my sincere appreciation for the invitation to formally discuss these very interesting papers --all of which herald the coming of an entirely new era in the manufacture of quality steels. I also appreciate the references by Mr. Mosser and Dr. Swinkels to my first paper on the oxygen probe which was presented at the meeting of this group, here in Chicago, in 1966 and was subsequently published in the NOH Proceedings of that year. (1)

Jan 1, 1972

By W. W. Smeltzer

The linear formation rates of wustite films have been determined over the temperature range 590° to 1030°C using a vacuum microbalance technique. These rates are dependent directly on the partial pressure of carbon dioxide, Activation energies for film and scale formation in carbon dioxide and oxygen atmospheres are equivalent to either the dissociation energies of carbon dioxide and oxygen, or the activation energy for the diffusion of cation vacancies in wustite. Of the metals, iron is the most widely used basic constituent of durable alloys despite its intrinsic property of converting at a relatively rapid rate to the oxides from which it is derived. This property has accounted partially for many investigations on the oxidation of iron at low and high temperatures. Interpretation of the results have been complicated by formation of multilayers containing the various oxide phases. To aid in elucidation of the oxidation kinetics, measurements have been carried out in this investigation on the growth of the wustite surface layer. There are several studies directly related to the objective of this investigation. The growth of multilayer scales has been demonstrated to be diffusion controlled in oxygen at atmospheric pressure over the temperature range 450" to 1200°C by Davies, Simnad, and Birchenall.' To gain an insight into the diffusion mechanism, Himmel, Mehl, and ~irchenall' determined the self-diffusion coefficients of iron in wustite, magnetite, and hematite. These results were used to evaluate the oxidation rates of iron and its oxides, taking as a basis the theoretical parabolic rate equation developed by Wagner., The evaluations were compared to experimental data and were shown to provide essential confirmation of this theory. Fischbeck, Neundeubel, and salzer4 have demonstrated that the oxidation of iron in carbon dioxide and other atmospheres at high temperature obeys a linear relationship. Because the Arrhenius temperature coefficients of the reaction rate constants changed at the A, point they concluded that the passage of iron into the oxide controlled the reaction. This viewpoint has been accepted by Benard and ~albot' to explain the occurrence of linear rates in oxygen before the onset of diffusion-controlled parabolic oxidation. This basic premise of a rate-controlling reaction at the iron/oxide interface has been questioned recently by Hauffe and Pfeiffer.' Since the formation of wustite may follow a linear or parabolic relationship depending on the pressure of the gaseous re-actant, they propose that linear oxidation is determined by a chemisorption reaction while parabolic oxidation is controlled by diffusion. As confirmation of this viewpoint, Hauffe and pfeiffer6 and Pfeiffer and ~aubmeyer' have established that the linear scaling constants of wustite formation at 1000°C in carbon-dioxide or low-pressure oxygen atmospheres

Jan 1, 1961

By K. H. Ribe

Water often enters an oil reservoir during completion or workover operations on a well and forms a partial "water block" to oil production. A mathematical study of radial two-phase flow, neglecting capillary effects, has been employed to study the formation of such a water block and subsequent re-moval by production from the well. The effects of reduced oil permeability about the well on the well productivity were studied. The fluid saturation distributions about the well during formation and removal of the water block have also been computed. Several relative permeability relations and viscosity ratios were employed. If water has invaded the formation, its influence through relative permeability effects alone can cause the following. 1. Oil productivity will be depressed for extended periods after production is resumed and will build up only gradually as the water is removed. 2. Oil injected for treatment of water blocking will delay rather than promote restoration of full well productivity by enlarging the region invaded by water. Thus, unless the specific action of chemicals contained in the oil is needed, oil injection appears undesirable. INTRODUCTION During oilwell workover operations, water may enter the oil-bearing formation from the wellbore. When production is resumed, oil must flow through the region invaded by this water. The presence of this region can cause both well productivity and oil production rate to be low and oil to be produced with high water-oil ratio for some time after production is initiated. This situation is sometimes described as a water block. The introduction of water into the formation may result in other actions which also lead to reduction in well productivity and which are also usually included in the connotation of the broad term, water block. Often considered, for example, are the possibilities of clay swelling by contact with fresh water and the formation of emulsions with the formation oil. If it is suspected that such specific actions have taken place, remedial treatments are undertaken which usually involve the injection of chemicals in oil. Since the introduction of water, even in the absence of specific interactions with the formation or oil, will cause a temporary water block (which might be misinterpreted as evidence of a more severe situation), it is of importance to evaluate the magnitude and duration of this blocking which results purely from the reduction in relative permeability to oil in the vicinity of the wellbore. It is also of interest to evaluate the effect of oil injection on the productivity of a well blocked by water in this manner. Inasmuch as this unfavorable condition may persist for some time, it may lead to premature condemnation of a workover or premature abandonment of a potentially productive pay zone. A quantitative evaluation of the influence of water entry on the oil productivity through changes in relative permeability was made by solving a radial form of the Buckley-Leverett equation. The distribution of water saturation around the wellbore during the entry of water was calculated and was followed by a similar calculation of the saturation distribution during the period of resuming production. At any stage in the removal of the invading water, knowledge of the distribution of its saturation permitted calculating the attendant loss in oil productivity. The influence of the shape of the relative permeability relationships was also evaluated by carrying out the calculations for two hypothetical cases. Further, the effect of the oil-water viscosity ratio was examined by repeating the calculations, for several ratios of unity and greater, with the same relative permeabilities. Fi-nally, results are presented to show how the length of time a well must be swabbed to resume production depends on the length of time it has been subjected to invasion by water. STATEMENT OF THEORY Differential Equations Water is assumed to enter a producing formation which is initially at the connate-water saturation and contains no gas. The water and oil are treated as in-

By K. K. Rao, M. E. Nicholson

IN a recent paper on the solubility of carbon in Ni-Cu alloys,' Nicholson reported that the carbon solubility appeared to be limited by the electronic structure of the alloys and that the solubility was propor- tional to the density of states at the Fermi surface of the "3d" band. In order to determine whether or not this relationship is a general one, the study has been extended to other systems. One of these is the CO-Ni system. This system was chosen for study because 1) it is adjacent to Ni-Cu system in the periodic table, 2) the alloys of cobalt and nickel do not form stable carbides at 1000°C, and 3) the system exhibits no pronounced change (less than 1 pct) in lattice parameter from cobalt to nickel,' see Fig. 1. The alloys were prepared from -200-mesh 99.92 pct Ni furnished by the International Nickel Co. and spectroscopically pure -200-mesh cobalt sponge obtained from Johns on-Matthey and Co. The powders were weighed, mixed, and pressed using a pressure of 40,000 psi. The samples were sintered for 24 hr at 900° C in dry hydrogen and then cold rolled to a thickness of 0.010 in. (Samples containing more than 70 wt pct Co had to be annealed after cold reductions of about 20 pct to avoid cracking.) The alloys were carburized at 1000°C in an alun-durn boat containing Acheson AUC powdered graphite in an atmosphere of carbon monoxide cylinder gas which had been passed through Ascarite to remove carbon dioxide. After carburizing for either 12 or 24 hr the samples were moved to a cool zone of the furnace to cool. Cooling required about 5 min. The samples were filed to remove about 0.005 in. from the surface and then analyzed using a conventional combustion-gravimetric analytic method. The results of this investigation are shown in the lower portion of Fig. 1 and Tabulated in Table I. The nickel percentages for these alloys were determined from the weights of the powders from which the alloys were made. The solubility of carbon in pure cobalt at 1000°C (fcc) is 0.25 wt pct. This is somewhat less than the 0.33 wt pct measured by Boecker.3 From his data, it would appear Boecker's samples were supersaturated before the equilibrating treatment and that a 20-min treatment was not long enough to achieve equilibrium. Since in the present investigation the 12 and 24 treatments produced essentially equal carbon contents, our figure is presumed to represent more nearly the equilibrium value. The solubility of carbon in nickel of 0.19 wt pct agrees quite well with the value of 0.21 wt pct

Jan 1, 1963

By A. J. Bartlett

Island Creek conditions are generally referred to as ideal; yet, as at all other properties, there are all known hazards of coal mining. The hardest of these hazards to combat is the human element. The basic thought in the minds of the management of these properties is to produce coal with the utmost safety, and it has impressed upon its supervisory force that it does not want a ton of coal unless it can be produced safely. This company has instituted a mine inspection department, which reports direct to the general manager, arid all matters pertaining to safety come under the direction of this department. Through the medium of the inspection department, the management is kept in touch with the actual conditions existing in general at all mines. Inspections are made regularly arid continuously; that is, at all times while the mine!: are in operation some sections of some mines are being examined. These inspections cover all active and inactive workings. Miners are contacted in their working places and other employees at their respective, work. A thorough check is made to see that the state mining laws are complied with and that company safety rules arc being observed. Night shifts receive the same attention as day shifts. All violations and dangerous practices are brought to the attention of the plant supervisory force with suggestions and recommendations; major hazards of emergency nature are taken up immediately with the management. Periodical inspections are also made of all tipples, preparation plants, dumping and hoisting equipment, to see that all machinery is properly guarded, and walkways and platforms properly fenced; conditions of equipmcnt and mechanical defects are also reported. Reports of inspection are written in letter form and in such a manner as to give the management a picture of the existing conditions at the time of inspection. Copies of inspection reports are forwarded to the superintendents with the general manager'? comments. It has been said, "There is nothing under God's heaven that justifies. your creation or your citizenship but this gospel: ' That the next greatest

Jan 1, 1938

By A. J. Bartlett

Island Creek conditions are generally referred to as ideal; yet, as at all other properties, there are all known hazards of coal mining. The hardest of these hazards to combat is the human element. The basic thought in the minds of the management of these properties is to produce coal with the utmost safety, and it has impressed upon its supervisory force that it does not want a ton of coal unless it can be produced safely. This company has instituted a mine inspection department, which reports direct to the general manager, arid all matters pertaining to safety come under the direction of this department. Through the medium of the inspection department, the management is kept in touch with the actual conditions existing in general at all mines. Inspections are made regularly arid continuously; that is, at all times while the mine!: are in operation some sections of some mines are being examined. These inspections cover all active and inactive workings. Miners are contacted in their working places and other employees at their respective, work. A thorough check is made to see that the state mining laws are complied with and that company safety rules arc being observed. Night shifts receive the same attention as day shifts. All violations and dangerous practices are brought to the attention of the plant supervisory force with suggestions and recommendations; major hazards of emergency nature are taken up immediately with the management. Periodical inspections are also made of all tipples, preparation plants, dumping and hoisting equipment, to see that all machinery is properly guarded, and walkways and platforms properly fenced; conditions of equipmcnt and mechanical defects are also reported. Reports of inspection are written in letter form and in such a manner as to give the management a picture of the existing conditions at the time of inspection. Copies of inspection reports are forwarded to the superintendents with the general manager'? comments. It has been said, "There is nothing under God's heaven that justifies. your creation or your citizenship but this gospel: ' That the next greatest

Jan 1, 1938

By Nicholas J. Grant, John S. Benjamin, Bill C. Giessen

In the course of a study of hard particle-duc tile binder composite alloys, interest arose in the nature of the products of the reaction between the inter metallic compound NiAl and the binder niobium. No published information was then available. A program to

Jan 1, 1967

By W. R. Bendy

GRINDING is a large and costly part of Portland cement manufacture. Prior to clinkering in the rotary kiln, raw materials are ground to a fineness of 80 to 90 pct passing 200 mesh. Then, after burning and cooling, the resulting clinker is ground to about 92 pct passing 325 mesh. In the cement industry the most favored method of grinding has always been by impact and attrition of a ball charge in a rotating mill. Other types of mills, in which materials are ground between die rings and rollers, or between die rings and large balls, are sometimes used for single-stage grinding and often for preliminary grinding followed by grinding in ball-type mills. Their efficiency is usually high, but maintenance and repair costs are high also, and the ball-type mill continues to be the most widely used.

Jan 10, 1957

ALTHOUGH everybody is familiar with coal, few persons have an exact idea of, the great impor-tance of this precious fuel. Coal is the black bread of industry. Without it, industrial activity is much restrained; and so the great industrial countries of Europe and the United States of America are the great producers of coal. The 1913 production of coal in Belgium was 22,842,-000 tons, valued at 418,700,000 fr., nearly a half billion. In 1919, it was 18,483,000 tons, about 81 per cent. of the production before the war; in 1920, it had reached 22,414,000 tons, approximately the production before the war. To show the importance of coal production of Belgium, let us say that the coal industry employed 168,000 workers in the year of 1920, the metallurgical industry only 129,000 and the textile industry 103,000. The coal industry, then, employs the greatest number of workers. The value of the coal production in 1919 is estimated at 1,121,000,000 fr. On the basis of the production before the war, the value of the production of iron in 1919 would have been 701,000,000, of finished steel 1,086,000,000, and of zinc 415,000,000; therefore, in 1919 the value of the coal industry was greater than that of the metallurgical production.

Jan 8, 1922

By Fred N. Kissell, Natesa I. Jayaraman

Introduction This paper describes a recent Bureau of Mines research project that resulted in a simple procedure for reducing the dust exposure of longwall shearer operators. This project involved the development and testing of a water spray and passive shield system to hold dust against the face and away from the shearer operators. This system is known as the Shearer- Clearer.

Jan 1, 1981

By Norman Patton

THE subject assigned is so broad that thorough discussion is well-night impossible within the space allotted, and further, few specific data are available upon which to predicate conclusions concerning the efficiency of present methods of distributing anthracite. This paper treats briefly the various agencies through which both primary and secondary distribution are effected, the methods of transportation and the general interrelation of production, demand, inventories and price. AVENUES OF DISTRIBUTION "Three distinct types of primary distribution are common in the marketing of anthracite. First, though not most important, is the sale by the producer, or operator, direct to the consumer. These sales, other than to employees and the local trade, are generally confined to steam sizes for industrial uses, and are consigned to the sidings or docks of the consumer. Sales of this type often are so closely priced to compete with oil and bituminous that the addition of even a small dealer's margin is sufficient to increase the cost to the point where the business might be lost. Second, the operator sells to a wholesaler or broker for subsequent resale, either to a retail dealer for clearance through his yard or direct to large consumers. Usually this method of distribution is employed by the smaller operators, who do not find it economically feasible to maintain extensive sales organizations. In most instances, the wholesaler retains some 5 per cent for his services, paid, of course, by the producing company whose anthracite he handles. He may, and frequently does, handle the output of several different companies, suited to the varying needs of the

Jan 1, 1935

By F. C. Dyer, H. E. T. Haultain

There has been much written on ball-mills, but no small amount of the literature is simply the expression of individual opinion without sufficient data. This is no doubt due to the complexity and obscurity of the phenomena involved. The outstanding paper is by E. W. Davis,I superintendent, School of Mines Experiment Station, University of Minnesota, which is based on a large amount of data from careful experiments with full-size apparatus, together with some mathematical philosophy. The entire philosophy is summed up in the equations given; but the present writers question the foundation upon which this philosophy is based. Encouraged by the work of Davis, the authors of this paper continued work they had been doing along this line. At first, photographs were taken of the ends of rods in a small laboratory rod mill. The mill was tilted slightly toward the feed end and the discharge end was removed. The rods remained in the mill long enough to permit good observation and good photography. Later, a mill 24 in. inside the stepped lining was constructed. It consisted of two sheets of plate glass, 1/2 in. apart, set in a cast-iron ring. It was driven by a variable speed motor and was connected to an accurate speedometer (magneto and voltmeter type). In place of balls or rods, cast brass disks were used. These were 3/8 in. thick and varied in diameter from 2 in. down to 3/4 in. Four small projections on each side prevented the disks sticking to the glass when water was used; sometimes steel balls % in. in diameter were added to the load of disks. There was also constructed a 6-in. mill with corrugated linoleum lining and containing a dry load of various sizes of steel balls. The mills were so connected to the motor that the small mill made two revolutions to one of the large mill. Many runs were made with a great variety of materials, including crushed marble, seeds of many kinds, and many mixtures (some wet and

Jan 1, 1923