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By E. L. Mann

Asbestos is the generic name given to a group of fibrous mineral silicates found in nature. They are all incombustible and can be separated by mechanical means into fibers of various lengths and cross sections, but each differs in chemical composition from the others. The commercial grades of asbestos consist of a spectrum of lengths and sizes and are not definitive as are most organic fibers. It is generally recognized that there are two main groups of asbestos. The first only contains the fibrous serpentine called chrysotile and comprises about 94% of the world production of asbestos. The second group contains five minerals in the amphibole series-crocidolite, amosite, anthophyllite, tremolite, and actinolite. The latter two have no commercial importance. Properties Physical The structures of asbestos fibers have been studied intensively over a number of years. X-ray diffraction patterns have been used as a means of identification and classification. Low angle X-ray scattering techniques have shown that chrysotile fibers are "hexagonally close packed" and parallel to each other, having cross-sectional diameters varying from 18Å to 300 Å units, while the amphibole fibers are many times larger in cross section, have considerably smaller surface areas, and the fibers are less symmetrical than those of chrysotile. Electron micrographs of the more common types of asbestos are shown in Figs. 1-4. Fig. 1 illustrates the softness and flexibility of chrysotile which make it suitable for textile-type products. For a number of years there was considerable controversy over the exact nature of chrysotile fiber, but the photographic evidence in Figs. 5-7 clearly show that it is tubular in structure. The curvature is the result of the mismatch in the dimensions of the silica [Si2O5] and brucite [Mg(OH)2] layers which are on the inside and outside, respectively, of a double sheet. This curvature had been predicted by Pauling (1930) years ago based on the molecular dimensions of the two component structures. In contrast to this, the structure of the amphiboles consists of two ribbon chains based on Si4O11 units separated by a band of seven cations with two hydroxyl groups attached to

Jan 1, 1983

By C. L. Shapiro, R. Schempp

DuRing the past few years, general interest in the steel-producing and steel-consuming industries has been centered on the so-called "inherent characteristics" of steels. While often vaguely described, these characteristics are known to influence the response to heat-treatment and the hardening characteristics of the material. Although most of the recent papers and discussions have associated the "inherent characteristics" with the austenitic grain size and emphasized the importance of it, comparatively little is known of the variables that may affect the size of the austenite grain. The work to be described in this paper was carried out during the course of a study on the inherent characteristics of tool steel containing one per cent carbon. The discrepancies encountered in the determination and classification of the austenitic grain size led to an investigation of some of the variants influencing the austenitic grain size as determined by standard methods. Methods of Determining Austenitic Grain Size The present methods used for the determination of the austenitic grain size may briefly be classified in two groups: 1. Etching at room temperature to reveal the austenite grain size prior to cooling. 2. Etching at elevated temperatures, cooling to room temperature, and observing the structural conditions that existed at the temperature from which cooling occurred. The outstanding methods of the first group are: (1) the McQuaid-Ehn test, (2) optimum rate of cooling, (3) quenching and etching. McQuaid-Ehn Test.—This established and accepted test does not need much elaboration. It consists of pack carburizing at a definite temperature for a standard period of time and slowly cooling in the furnace. The temperature is 1700" F. (925' C.) and the time is 8 hr. The interpretation and evaluation of this test are fairly well defined in the A.S.T.M.

Jan 1, 1937

By W. E. Bearce

The recent concern for the recovery of even the finest fractions of coal preparation plant feeds has created needs for new equipment. Thermal dryers currently available have difficulty reducing the filter cake moisture on down to the desired point. This difficulty involves 1) the physical problem of handling this wet, sticky material and making each particle accessible to the hot gases, and 2) removing the extremely fine dried particles from the cooled gases. The dryer described in this paper handles the first of these problems, and eliminates the second by the substitution of steel balls for air as the heat transfer medium. As a general statement, the cost of preparing coal for market is inversely proportional to the size of the lumps or particles. In the not too distant past the finer sizes were discarded as being uneconomical to treat and this practice might be still continuing if it were not for the insistence of the public that this material be kept out of our streams. This being the only cost-free outlet, the disposal of fine refuse became a significant item of expense in every preparation plant. When this happened it was only reasonable to look to the recovery of the values in this material, not only to defray this expense, but to reduce the tonnage which had to be wasted. There seemed to be no device available suited to reducing the moisture in this material to what the market requires. All of the fine coal dryers commonly employed make use of air to bring the heat of combustion into contact with the coal particles. Any device employing air as a heat transfer medium, has the following two strikes against it in attempting to handle 28 mesh by 0 filter cake: 1) It is practically impossible to bring the hot air into intimate contact with the enormous number of fine particles stuck together in the cake. 2) Even if this can be effected, it is impossible to remove the dried coal from the air. A wet scrubber must be employed, the discharge of which must go back to the filter and dryer as a circulating load of the most objectionable sort, being the extreme fines. Various compromises have been used to cope with the problem of drying this relatively small tonnage of high moisture coal. Often some of the dried coal is mixed back with the feed to the dryer in an attempt to make the mixture more handleable and more available to contact with the hot air than the filter cake alone would be. This may help to some extent with the first problem but it does nothing about the second and a dryer operated in this way has to be oversized. Sometimes the filter cake is mixed with a coarser fraction for the same reason. Here again, while this may make a mixture (the particles of which are more readily brought into contact with the hot air), the problem of getting the fine coal out of the air remains and a larger percentage of the total coal to be dried is handled by the most expensive means. Mechanical dewatering has accounted for more and more of total coal drying lately and in many cases would satisfactorily handle the whole load, down to 28 mesh, if there were a means available for doing a good job on the —28 mesh by itself. The dryer which is the subject of this paper was designed expressly for doing this job — drying fine material by itself regardless of how wet it may be to start with, how fine it may be, or how gummy and sticky these properties in combination may make it. The essential features are depicted in Fig. 1. A rotating cylinder is supported on a frame in such a way that one end may be raised or lowered by hy-

Jan 1, 1968

By William Rawles

THIS report is the first of a series planned by The Mineral Inquiry, organized by the American Institute of Mining and Metallurgical Engineers to make factual studies of the world's mineral resources in their political and international relations. The efforts of The Inquiry are directed toward filling certain notable gaps in available information, without duplication of many other investigations touching this field which are being conducted by other organizations, public and private. Much of its work is indirect-suggesting topics for study by other individuals and organizations and aiding in their planning and correlation. The present report is designed to show the nationality of the commercial control of mineral resources, in addition to the geographic distribution of production by nation-in other words, the overlapping of political and commercial control. Detailed accuracy cannot be claimed for the figures presented. For some companies division of ownership by nationality has been very difficult to ascertain, as many companies are reluctant to dis-close the extent of their holdings in other corporations, and the impossi-bility of tracing all stock ownership is obvious. Also there are frequent changes in the distribution of stock control. The percentages given rep-resent only the participation that has been identified definitely, even though it is known in some cases with fair certainty that larger interests exist, as, for instance, American participation in foreign chromite companies. In bringing together these figures we have had the cordial co-operation of the United States Bureau of Mines, the United States Geologi-cal Survey, the Mineral Division of the Bureau of Foreign and Domestic Commerce, the Brookings Institution, and of many specialists connected with the mineral industries covered. The report does not cover the entire list of minerals. Coal, although it is one of the most important minerals, was omitted because, not more than one or two per cent of the world's production comes from mines that are owned by companies foreign to the countries where the coal is produced. Others, such as gold, are omitted because sufficient data have not yet been accumulated. It is hoped that some of these may be covered in subsequent reports. It is not our purpose here to discuss the significance of the figures sub-mitted, but only to point out the general nature of the problems on which they have a bearing.

Jan 1, 1933

By J. W. Snavely

THE high tension belt conveyor is introducing a new and tremendously expanded era of low cost bulk material handling. High tension belt conveyors are generally those installations involving very long centers, high lifts, or drops, in which the belts are stressed up to their maximum tension values, and further, where the belt construction provides tension capacity far beyond what is possible with conventional belt constructions. With these high tension installations, the magnitude of the forces involved demands careful refinement of accepted design practice in order to achieve optimum balance of all factors. No attempt will be made to evaluate the relative merits of belt conveyor haulage with other means of transportation. For present purposes, it is assumed this has already been done in favor of belt conveyor. Neither will any attempt be made to evaluate the various conveyor belt constructions now available or to balance the advantages of various types of mechanical equipment. It is also assumed that the basic haulage information on which the conveyor design is based is accurate and complete. A sustained maximum, uniform load on the belt at all times must be achieved through proper feed control and the use of adequate surge storage to level the peaks and valleys of any varying demand for the material being handled. General Belt Capacity Considerations The belt conveyor capacity tables published by various belting and conveyor equipment manufacturers vary to a considerable degree, and the ratings given are quite conservative. Of necessity, these published ratings are based on the handling of average materials under average conditions. In applying a high tension belt, all possible capacity from the belt must be obtained in order to hold its width to a minimum and thereby limit the initial cost. Two factors are involved, loading to maximum cross section area and traveling at a maximum practical speed. Belt Loading: Proper treatment of the loading of the belt will result in maximum cross section to the load, and published capacity ratings can be exceeded, sometimes by appreciable margins. On the 10-mile conveyor haul used in the construction of Shasta Dam, California, although the rated capacity of the belt line was 1100 tons per hr, at times the system handled peak loads of 1400 tons per hr, almost 25 pct better than the rated capacity. One of the large coal companies has been able to exceed rated capacity by as much as 50 pct. Loading conditions which must be controlled are: 1. Large lumps must be scalped off and rejected or the load must be primary crushed before being placed on the belt. 2. The material weight per cubic foot must be accurate, must be known for all the materials being handled, and must be known for the complete range of conditions of the individual material being handled. Long centers and high lifts magnify small differences into serious proportions. 3. Uniform feeding to the belt is most important. Various types of feeders are available, which can be used to place a constant predetermined volume of material on the belt, or, where an appreciable range of material weight exists, through electrical control actuated by current demand, to place a predetermined uniform tonnage on the belt. One long slope belt in a coal mine in Pennsylvania is being fed at three separate stations with the controls so arranged that whenever the maximum load is going onto the belt from the first station, the other two stations automatically cut out. Whenever the load from the first station drops back, the other two stations again automatically cut in. 4. Careful design of the chutes and skirts is necessary to get the load centered on the belt with a minimum of free margin along each edge. Some free margin at the edge of the belt is necessary to prevent spillage, but if the load can be kept accurately centered, this free margin area can be reduced, and more material can be carried on the belt. What can be accomplished in this respect will vary widely, depending on the nature of the material being hauled. The chute and skirt design must also protect the belt. 5. The design of chutes and skirts should also get the load traveling in the same direction and close to belt speed, so that the load comes to rest on the belt as quickly as possible. The design of the chutes and skirts is worthy of careful study, and after a system is put into operation it should be experimented with to get the best results. Belt Speed: High belt speeds should be used in high tension work. Obviously, high belt speeds enable haulage on a narrower belt, reducing initial cost. The major portion of belt wear takes place at the loading point and around the terminal pulleys. The

Jan 1, 1952

By H. D. Hodges, J. K. Godbey

In order to better understand the fracturing process, bottom-hole pressures were measured during a number of typical fracturing operations. A recently developed system was used that allows simultaneous surface recording of both the bottom-hole and wellhead pressures on the same chart. The results from six fracruring treatments are summarized on the basis of the pressure data obtained. Al-though no complete analysis is attempted, the value of accurate pressure measurements is emphasized. Important characteristics of the bottom-hole pressure record do not appear at the wellhead because of the damping effect of the fluid-filled column. In four of the six treatments described, the formations apparently fractured during the initial surge of pressure with only crude oil in the well. The properties of the fluids used during the treatments are given and the fluid friction losses are obtained directly from the pressure records. This technique is also shown to be adequate for determining when various fluids, used during the process, enter the formation. INTRODUCTION Hydraulic fracturing for the purpose of increasing well productivity is now accepted in many areas as a regular completion and workover practice. Numerous articles have appeared in the literature discussing the various techniques and theories of hydraulic fracturing'. In general, three basic types of formation fractures are recognized today. These are the horizontal fracture, the vertical fracture, and fractures along natural planes of weakness in the formation'. Any one or all three of these fracture types may be present in a fracturing operation. However, with only the wellhead pressure record as a guide, it is difficult at best to determine if the formation actually fractured, and is almost impossible to determine the type of fracture induced. These difficulties arise in part because the wellhead pressure record, especially when fracturing through tubing, does not accurately reflect the pressure variations occurring at the formation. Several factors contribute to this effect and preclude the possibility of using the wellhead pressure as a basis for accurately calculating the bottom-hole pressure. These factors are: 1. The compressibilities of the fluids which damp the pressure variations. 2. The changes in the densities of the fluids or apparent densities of the sand-laden fluids. 3. The flowing friction of the various fluids and mixtures, which is dependent on the flow rates and the condition of the tubing, casing, or wellbore. 4. The non-Newtonian characteristics of a sand-oil mixture and its dependence upon the fluid properties, the concentration of sand, and the mesh size used. 5. The unknown and variable temperatures throughout the fluid column. Because of these reasons it was determined that in order to obtain a more accurate knowledge of the nature of fracturing, the bottom-hole pressure must be measured along with the pressure at the surface during a fracturing treatment. Even with accurate pressure data, a reliable estimate of the nature of fracturing is still dependent upon knowledge of the tectonic conditions. However, the hydraulic pressure on the formation is basic to any approach to a complete analysis. In order to accomplish this objective a system was developed to record the wellhead and bottom-hole pressures simultaneously at the surface. By recording both pressures on a dual pen strip-chart recorder, it was possible to greatly expand the time scale so that rapid pressure variations would be faithfully recorded. By such simultaneous recording, time discrepancies inherent in separate records are eliminated, thus overcoming one of the most difficult problems associated with bottom-hole recording systems. This paper illustrates the results obtained by using this system during six typical fracturing operations. All of these tests were taken in wells that were treated through tubing. By a direct comparison of the wellhead and bottom-hole pressures, the importance of obtaining complete pressure information during a fracturing treatment is emphasized. THE INSTRUMENTATION AND PROCEDURES The bottom-hole pressure measuring instrument consisted of a pressure-sensing element, a telemetering section, and a lead-filled weight or sinker bar. The pressure-sensing element used was an isoelastic Amerada pressure-gauge element. By using an isoelastic element, no temperature compensation was necessary in the tests described, since the temperature was believed to be well below the maximum temperature limit of 270°F. The rotary output shaft of this helical Bourdon tube element was coupled to a precision miniature potentiometer. The rotation of the pressure-gauge shaft thus changed the resistance presented by the potentiometer

By R. W. Raymond

Richard Pennefather Rothwell, was born May 1, 1836, at Oxford, Upper Canada (now the province of Ontario). His father, Rev. John Rothwell, was a native of County Meath, Ireland, where the family (originally, no doubt, a Scottish one) still holds large estates, under a grant from William and Mary. John Rothwell was graduated at Trinity College, Dublin, and became a clergyman of the Established Church. He married Elizabeth Garnett, of Athearn Castle, Ireland, and subsequently came to Canada. It is said that he was a man of liberal views combined with sterling piety, an enthusiastic sportsman and yachtsman, and a pastor who refused for many years to accept any remuneration from his parishioners. After preliminary education, the subject of this sketch entered Trinity College, Toronto, with the intention of studying law; but a year later he resolved to become a civil engineer, and entered the Rensselaer Polytechnic Institute at Troy, N. Y., where he was graduated, with high standing, as civil engineer, in 1858. He then went to Paris, and entered the Imperial School of Mines, where, by reason of the proficiency he had already acquired in civil engineering, he was able to finish in two years and a half the full three-year course, and to take the degree of Engineer of Mines. In 1861 he took the "practical courses" in mining and ore-dressing at the Mining Academy of Freiberg, Saxony. After traveling in Italy, etc., he went in 1862 to London, where, for the purpose of familiarizing himself with business methods, he entered the offices of W. T. Henley, a manufacturer of wire

Jan 1, 1902

By W. C. Maurer

A study of bit-tooth penetration, or crater forniation. under simulated borehole condirions has been made. Pressure conditions existing when drilling with air, water and mud have been sirnulated for depths of 0 to 20.000 ft. These crater tests showed that a threshold bit-tooth force must he exceeded before a crater is .formed. This thresh old force increased with both tooth dullness and diflerenrial pressure between the borehole and formalion fluids. At low differential pressures, the craters formed in a brittle manner and the cuttings were easily removed. At high differenlial pressures, the cunings were firmly held in the craters and the craters were formed by a pseudoplas-tic mechanism. With constant farce of 6,500 16 applied to the bit reeth, an increase in differential pressure (sitnulated mud drilling) from 0 to 5,000 psi reduced the crater volumes by 90 per cent. A comparable increase in hydrostatic fluid pressure (simulated water drilling) produced only a 50 per cent decrease in volutne while changes in overburden pressure (simulated air drilling) had no detectable effect on crater volume. Crater tests in unconsolidated sand subjected to differential pressure showed that high friction was present in the sand at high pressures. Similar friction belween the cuttings in craters produces the transition from brittle to pseudo plastic craters. INTRODUCTION The number of wells drilled below 15,000 ft increased from 5 in 1950 to 308 in 1964. Associated with these deep wells are low drilling rates and high costs. High bottom-hole pressures produce low drilling rates by increasing rock strength and by creating bottom-hole cleaning problems. This paper describes an experimental investigation of crater formation under bottom-hole conditions simulating air, water and mud drilling. Although numerous investigators have studied bit-tooth penetration (cratering) at atmospheric pressure conditions, only limited work has been done on cratering in rocks subjected to pressures existing in oil wells. Payne and Chippendale2 have studied cratering in rocks subjected to hydrostatic pressure using spherical penetrators. Garner et aLJ conducted crater tests in dry limestone by varying overburden pressure and borehole fluid pressure independently and using atmospheric formation-fluid pressure Gnirk and Cheathem4,5 have studied crater formation in several dry rocks subjected to equal overburden and borehole pressure and atmospheric formotion pressure. Podio and Gray studied the effect of pore fluid viscosity on crater formation using atmospheric borehole and formation-fluid pressurc and varying overburden pressure. Although these studies have provided useful information on crater formation under pressure, they were limited in that the three bottom-hole pressures could not be varied independently and, therefore, that many drilling conditions could not be simulated. The prersure chamber used in this study allowed visual observation of the cratering mechanism and independent control of the borehole, formation and confining pressures. By using different fluids in the chamber, pressure conditions existing in air, water and mud drilling to depths of 20,000 ft were simulated. The mechanisms involved in cratering at these different pressure conditions were studied for teeth of varying dullness and at different loadins rates. High-speed movies (8,000 frames/sec) and closed-circuit television were used to visually study the crater mechanism under pressure. EXPERIMENTAT PROCEDURE PRESSURE CHAMBER The Pressure chamber in Fig. I was used to simulate bottom-hole pressure conditions. This chamber has been pressure-tested to 22,500 psi and is normally operated at pressures up to 15,000 psi. The chamber contains four lucite windows' used for illuminating and observing the crater mechanism under pressurc. A closed-circuit television and a Fastax camera (8,000 frames/sec) have been used in these studies. Cylindrical rock specimens (8-in. diameter X 6-in. long) were subjected to three independently controlled pressures simulating overburden, borehole fluid and formation-fluid pressures. Overburden pressure, which corresponds to the stress induced by the overlying earth mass, was applied by exerting fluid pressure against a rubber sleeve surrounding the rock. Borehole pressure, which is the pressure exerted by the column of mud in the wellbore, was simulated by applying pressure to the fluid overlying the rock in the chamber. Formation pressure was simulated by applying pressure to the water saturating the rock. The borehole and formation pressures were equal except when mud was used in the chamber, in which case the differential pressure between these fluids acted across the mud filter cake.

Jan 1, 1966

By W. C. Hagel, H. J. Beattle

DURING an earlier examination of high-temperature alloy, A-286, the presence of an unknown intermetallic compound was verified by X-ray diffraction. Owing to its prominent appearance at grain boundaries, the arbitrary name of G phase was assigned.' Low-silicon, vacuum-melted heats were found to contain no G phase, and this investigation was initiated to determine the influence of silicon on G-phase formation; additional work was undertaken to extend existing data on other intermetallic compounds and the aging reactions in this group of alloys. Taylor and Floyd2-4 observed that the Ni3Al phase (y') and the Ni8Ti phase (7)) are the only equilibrium intermetailic compounds in nickel ternary alloys containing up to 25 pct Cr and 10 pct Ti or Al. They found that y' can dissolve considerable nickel, chromium, and titanium, although the stoichio-metric composition of 7 remains fixed. Nordheim and Grant5 confirmed that age hardening of 80 pct Ni-20 pct Cr alloys of the Nimonic-80 type is due to precipitation of y', where aluminum is partially replaced by titanium. They suggest that optimum hardness and ductility result from increasing the titanium to aluminum ratio toward the end of the y' solubility range and from increasing total titanium and aluminum content to the maximum limit permitted by processing. Such information is necessary for those seeking to improve the service-temperature range and long-time structural stability of high-temperature components. Experimental Methods Compositions of materiais studied. are listed in Table I. Alloys D, E, and F possess representative A-286 analyses; silicon increases from less than 0.02 to 1.75 pct in alloys A to H; in alloys I to K, titanium decreases from 2.24 to 0.39 pct, and aluminum increases from 0.1 6 to 240 pct. Alloys A and D were solution heat treated for 4 hr at 1700°F, oil quenched and aged for 0.5, 2, 6, 12, 30, 70, 200, and 1000 hr at 1200°, 1300°, 1400°, and 1500°F. Therefore, a total of 33 specimens was required for each

Jan 1, 1958

By J. Volney Lewis

The following paper is based chiefly on work done for the North Carolina Geological Survey, and is presented here by permission of Professor J. A. Holmes, State Geologist. It represents, in a very general way, the field-results obtained during the summer months of 1893, and 1894, and part of 1895; and the portions pertaining to North Carolina are, to a certain extent, abstracts of a report shortly to be published as Bulletin No. 11 of the State Survey. Less emphasis, however, is here laid on the petrographic descriptions of the peridotites, and more detailed treatment is given to subjects pertaining to methods of mining, cleaning, and utilization of the commercial product, corundum. Some of the most extensive fields for investigation which this subject presents have been scarcely more than suggested.

Jan 1, 1896

By R. Taggart, R. H. Ericksen, D. H. Polonis

MarTENSITIC a has been observed to form spontaneously from the retained ß phase during the preparation of thin foil specimens of metastable Ti-Cr alloys containing from 6.9 to 20 wt pet Cr. Similar spontaneous martensite reactions have been reported in thin foils of 0 brass' and other alloys.2 4 The absence of retained austenite in iron-based alloys has also been attributed to spontaneous decomposition during thinning.5 The present work indicates that a unique situation occurs during which the spontaneous transformation takes place when the transitional ? phase is present in the as-quenched or partially aged ß phase. Alloys containing 6.9, 7.0, 8.0, 12.0, and 20.0 wt pet Cr were prepared by the levitation melting of "io-chrome" chromium and iodide titanium. The 0.5-in.-diam ingots were vacuum-annealed at 1000oC, and wafers 0.020 in. thick were then cut from the ingots. These wafers were wrapped in molybdenum foil, encapsulated in Vycor under a reduced pressure of purified helium, and then held for 30 min at 1000°C. The specimens were quenched in water to retain the metastable high-temperature ß phase. The quenched alloys were thinned by mechanical grinding to about 0.005 in. thick, then electropolished in a solution of 300 ml methyl alcohol, 175 ml n-butyl alcohol, and 30 ml perchloric acid at a temperature of -40°C. Needle specimens 0.005 to 0.010 in. diam were taken from each ingot and heat-treated with the foil specimens. X-ray diffraction patterns indicated the structure of the 6.9, 7.0, and 8 wt pet alloys to be a

Jan 1, 1968

By P. J. Carroll, H. Colijn

Feeders must be considered an integral part of the over-all bin and feeder system. Improper design of either one of these parts will affect the performance of the whole system. Feeder load, material properties, feed rate, physical layout, and environment as well as first cost determine the selection of feeder type. This paper provides a new method of calculating feeder loads with some experimental data as verification. General design criteria for belt and apron feeder, rotary table and plow feeders are discussed and a special section is devoted to vibratory feeders. Feeders are used to provide a means of control for the withdrawal of bulk materials from storage units such as bins, bunkers, silos and hoppers. This control function can only be performed properly as long as the bulk materials flow by gravity to the feeder in a uniform and uninterrupted fashion. During the past few years various papers have been written and presented on feeders and their application.1-9 This paper will be confined to some specific bin-feeder design criteria such as feeder load and power requirements. Special attention is given to the basic design criteria for vibratory feeders. HOPPER AND BIN DESIGN Feeders must be considered an integral part of the over-all bin and feeder system. Improper design of either one of these parts will affect the performance of the whole system. A lot of effort has been devoted in the past decade to the development of functional design criteria for hoppers and bins.1,10 The integrated concept of bin and feeder design requires quantitative analysis of the bulk material characteristics before the design and the selection of components can be attempted. The design of a feeder system must begin with the proper dimensioning of the hopper outlet to prevent arching or ratholing. The hopper opening should be large enough to allow passage of the bulk solid at the required maximum discharge rate." A feeder can only throttle the flow. FEEDER LOAD DETERMINATION Over the past ten years, there have been various attempts to determine the exact load or pressure on feeders mounted directly under hopper openings. Many designers, however, still consider this pressure equal to the hydrostatic head of material above the opening, and because such pressure would be very

Jan 1, 1969

By M. Sagheer

This paper gives a report of the laboratory work investigating the fundamental flotation characteristics of chromite and its commonly associated mineral, serpentine. Floatability curves, showing floatability of chromite at different concentrations of sodium oleate and pH, were obtained by pick-up method. One of the difficulties encountered in flotation of chromite in presence of serpentine has been attributed to dissolved metal ions. The influence of metal ions, dissolved in pulp filtrate, on floatability of pure chromite and serpentine has been studied and it has been shown that Mg, Ca and Fe ions depress chromite. A considerable amount of work applying bubble pick-up method was carried out to counteract the depressing action of metal ions. Various methods and reagents were applied in this connection. Validity of each method and reagent has been discussed. Probably due to the abundance of high-grade chrome ores, very little has been published concerning the flotation of chromite. As improvements in mineral beneficiation are realized, more attention is being directed to low-grade ores previously considered unusable. Currently, gravity concentration is the principal process applied to upgrade chrome ores, but this cannot be used for finely disseminated ore because of the substantial losses in the fines,1,2,3 To avoid these losses, flotation can be applied to material which is too fine for satisfactory gravity concent ration, and it is probable that a combination

Jan 1, 1967

By L. L. Wyman

SINCE the presentation, by the writer, of the initial paper on the embrittlement of copper,1 the subject has been investigated further along two separate lines. The first series of investigations involves the "double-deoxidized" copper, while the second series is devoted to single deoxidizers other than those used in the investigations reported upon last year. The object of these experiments is to develop a type of copper that will show the minimum of detrimental effects after having been exposed to alternate oxidation and reduction. The fabrication of this material necessitates the use of alternate oxidizing and reducing atmospheres, at temperatures ranging up to 900° C. Following this treatment it is essential that the soundness and strength of the copper be unimpaired, even in sections of only a few thousandths of an inch in thickness.

Jan 1, 1932

By Thomas A. Read

The internal friction of single crystals of metals is affected markedly by a variety of factors, which, according to the literature, are without influence on the internal friction of polycrystalline metals at strain amplitudes less than 10-5. For example, the internal friction of a suitably oriented zinc single crystal is multiplied by a factor of ioo when the vibration amplitude is slightly increased, and the internal friction of a copper crystal is markedly increased by the application of a stress of 30 lb. per sq. in. for one minute. In this paper it will be shown that these, together with the other phenomena associated with the damping of mechanical vibrations in metal single crystals, can be satisfactorily explained, at least qualitatively, in terms of an atomic mechanism that has been proposed for quite another purpose—that of accounting for slip in metals. The extraordinary agreement between the observed behavior of the metal single crystals and the behavior that could be predicted on the basis of this atomic mechanism leads to the belief that the latter is probably essentially correct. If this is so, it follows that valuable information about the slip process in metals may be gained from measurements of internal friction on single crystals. In this paper the results of the only study to date on the damping of mechanical vibrations in single crystals of metals mill be presented. Experimental Procedure The internal friction of a material is a measure of the rate at which the energy of mechanical vibrations is converted into heat. The measure of internal friction used in the present paper is the decrcment A, which is defined as the fraction of the energy of vibration lost per half cycle. The measurements described here were made for longitudinal oscillations at a frequency of 33.5 kc. for the copper crystals, and at a frequency of 39 kc. for the zinc crystals. The method used is that of the composite piezoelectric oscillator. The single-crystal specimens are in the form of circular cylinders M in. in diameter and I 1/2 to 21/2 in. long. The crystal rods are waxed in a V-block and sawed to the proper length with a fine jeweler's saw. The ends of the specimen are ground flat, and one end is cemented with a very thin film of beeswax and rosin to the end of an x-cut quartz rod which is 1/4 in. in diameter and 3 in. long. The length of the specimen rod is determined by the condition that its natural frequency for longitudinal vibration be the same as that of the quartz rod, within 0.5 per cent. The lengths of the specimens are thus different for different orientations of the cylinder axis with respect to the crystallographic axes. When the specimen and quartz rods are thus matched in frequency the adhesive is at a node of stress, and it has been shown experimentally that under these circumstances

Jan 1, 1941

By Thomas A. Read

The internal friction of single crystals of metals is affected markedly by a variety of factors, which, according to the literature, are without influence on the internal friction of polycrystalline metals at strain amplitudes less than 10-5. For example, the internal friction of a suitably oriented zinc single crystal is multiplied by a factor of ioo when the vibration amplitude is slightly increased, and the internal friction of a copper crystal is markedly increased by the application of a stress of 30 lb. per sq. in. for one minute. In this paper it will be shown that these, together with the other phenomena associated with the damping of mechanical vibrations in metal single crystals, can be satisfactorily explained, at least qualitatively, in terms of an atomic mechanism that has been proposed for quite another purpose—that of accounting for slip in metals. The extraordinary agreement between the observed behavior of the metal single crystals and the behavior that could be predicted on the basis of this atomic mechanism leads to the belief that the latter is probably essentially correct. If this is so, it follows that valuable information about the slip process in metals may be gained from measurements of internal friction on single crystals. In this paper the results of the only study to date on the damping of mechanical vibrations in single crystals of metals mill be presented. Experimental Procedure The internal friction of a material is a measure of the rate at which the energy of mechanical vibrations is converted into heat. The measure of internal friction used in the present paper is the decrcment A, which is defined as the fraction of the energy of vibration lost per half cycle. The measurements described here were made for longitudinal oscillations at a frequency of 33.5 kc. for the copper crystals, and at a frequency of 39 kc. for the zinc crystals. The method used is that of the composite piezoelectric oscillator. The single-crystal specimens are in the form of circular cylinders M in. in diameter and I 1/2 to 21/2 in. long. The crystal rods are waxed in a V-block and sawed to the proper length with a fine jeweler's saw. The ends of the specimen are ground flat, and one end is cemented with a very thin film of beeswax and rosin to the end of an x-cut quartz rod which is 1/4 in. in diameter and 3 in. long. The length of the specimen rod is determined by the condition that its natural frequency for longitudinal vibration be the same as that of the quartz rod, within 0.5 per cent. The lengths of the specimens are thus different for different orientations of the cylinder axis with respect to the crystallographic axes. When the specimen and quartz rods are thus matched in frequency the adhesive is at a node of stress, and it has been shown experimentally that under these circumstances

Jan 1, 1941

By G. K. Burgess

THE question of the allotropy of iron, in spite of a vast amount of experimental work and perhaps an even greater amount of theorizing, is not yet settled. That there is a definite transformation in iron near 900,° the A3 point, is generally recognized, as well as the fact that the temperature of this transformation is lowered by the addition of carbon and metallic elements. On heating, the transformation Ac3 is always found at a higher temperature than the transformation on cooling, Ar3. Whether the A3 transformation is sharp like the melting point of a pure substance, or extends over a considerable range of temperatures, embracing perhaps as a lower limit the A2 change, appears to be still an open question for pure iron. The nature and identity of the A2 transformation, it would appear from recent publications, has not yet been satisfactorily settled. In the present paper a critical, historical summary is given of the experimental investigations of the location of A2 and A.3 in pure iron, together with brief mention of some of the theoretical aspects of the subject, and an account is given of a series ?of experiments carried out with several samples of very pure iron which were studied by two methods of thermal analysis in the range from 5000 C. to 1,000° C., and which it is believed furnish a contribution of considerable interest as to the location and nature of the A3 and A2 transformations. Great attention has been given to the details of experimental manipulation and to the preparation of the samples, as it was soon found that some of the discrepancies noted in the work of many experimenters may be traced largely to lack of precautions which we have found essential. For example, to anticipate somewhat, it is necessary to provide a suitable practically gas-free furnace, the heating and cooling of which may be regulated to a nicety. To render a minimum the deforming effects on the cooling and heating curves of the poor conduction of the sample, it must be of a form and mass to pass on its heat rapidly and completely to the thermocouple; and finally the sample itself must be freed from gases which, if present, further mask the definiteness of the heating and cooling curves. We, have also varied within wide limits the several factors which may influence the determination of the exact location and shape of the transformation ranges, especially the mass and preparation of sample, rate of heating and cooling, design of furnace; and finally, as nearly as it is experimentally possible, we have worked with a substance approaching pure iron, free from occluded gases and other impurities, and contained within a vacuum.

Jan 10, 1913

By James Aston

INDICATIVE of the practical importance of the achievement of James Aston , recipient of the Robert W. Hunt Medal for 1930, is the following prosaic item from the financial columns of a recent issue of a New York newspaper. "According to private advices from Pittsburgh, production costs of the A. M. Byers Co. for 1929 were reduced about $5 a ton by the use of the Aston process for making wrought iron pipe. A greater saving is anticipated for 1930, when more of the company?s requirements will be produced by the new method."

Jan 1, 1930

By D. H. Yardley

GEOCHEMICAL investigation of trace elements in surface materials was begun near Ely, Minn., in 1953 along the basal contact of Duluth gabbro with Giants Range granite (Fig. 1). This article presents data on the distribution of copper and nickel in till and in stream sediments in the area and proposes an explanation for the types of distribution found. The Duluth gabbro, one of the world's largest basic intrusives, intrudes rocks which range in age from Keewatin to middle Keweenawan. Within the test area the gabbro is in contact with granite except for short sections where it is in contact with remnants of iron formation. Sulfide mineralization occurs within the gabbro, near and parallel to the basal contact for a distance of several miles. Schwartz and Davidson' have described the geologic setting of the mineralization. The sulfides, believed to be syngenetic, include chalcopyrite, cubanite, pentlandite, pyrrhotite, and minor amounts of bornite. They occur disseminated in the silicates and as small interstitial masses. The ratio of copper to nickel is about 3.8:1, based on 66 chemical analyses of rock samples from various outcrops (Ref. 1, p. 702, and Ref. 2). Test Procedures: With specified exceptions, all nickel and copper tests were made by the chromo-graph method,:' which measures the intensity of a colored spot formed by a reaction between the metal being determined and special reagent paper. The intensity is then compared to the intensity of spots prepared from samples of known metal content. Details of the test procedure are outlined in another article (Ref. 4, pp. 77,78). All soil samples tested in this investigation to date have been weighed on an analytical balance. However, a volumetric scoop designed to provide about 0.1 g of soil adds to the speed and ease of testing and has been found to give satisfactory results (Ref. 5, p. 531, and Ref. 19). The size of the samples used for the tests was 0.1 g. Whenever such small samples are used there is some question as to whether they are representative of the several grams in the field sample. Many repeat tests of the samples used in this investigation demonstrated that results can be reproduced within the limits of accuracy of the method without formal mixing beyond that inherent in screening the soil fractions. Furthermore, the 0.1 g is probably as representative of the field sample as the field sample is of its area of influence. Hawkes and Lakin (Ref. 6, p. 291), who considered the general problem, compared ground and quartered bulk samples of 500 g with 5-g grab samples. They concluded that "there is no significant loss in accuracy of data by substituting grab samples for bulk samples." The term soil implies somewhat different things to the geologist, engineer, and soil scientist.' For convenience the term as used in this article refers to unconsolidated material (the mantle) overlying bed rock. Sampling Procedure: Samples were taken at 100-ft intervals along north-south traverse lines across the gabbro-granite contact. The soil (till) samples were taken at an average depth of 1 ft, which was below the high-humus surface layer and into clean till. Samples taken at 1-ft intervals down to ledge showed as high a metal content at 1 ft below the air-surface as at greater depths and in two instances were slightly higher. The till at 1-ft depth did not appear to differ from material at greater depths. Total depth to bedrock has been tested at only a few points and where measured varied from 1 to 10 ft. Aerial Distribution Contours and Profiles: Plotting of copper, nickel, and cobalt content in contour form (Fig. 2) shows that anomalous amounts of these metal ions occur in till over and closely adjacent to mineralized areas of the gabbro. Contouring nickel content alone, or the copper content, outlines the same target area. Contours of the copper content provide a more distinct anomaly than nickel because of the higher copper concentration. The traverses are rather widely spread for interpolation; however, drilling has confirmed the target area essentially as shown.

Jan 1, 1959

By George S. Rice

MANY studies on ground movement and subsidence have been carried on by members of the Institute during the past year, but only a few papers have reached maturity. Two of the mining schools of this country have continued their interest in ground movement research. At Columbia University School of Mines, Philip Bucky has continued his investigations, employing photoelastic methods and the use of his centrifugal apparatus for testing what he termed "the strength and behavior of mining structures." Helmut Landsberg, of The Pennsylvania State College, has developed a convergence recorder similar in principle to that used by the

Jan 1, 1936