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By Robert T. Pring

In addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of employees, with a consequent decrease in labor turnover rates. One progressive mining company' estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination decreases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor, Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flowsheet. Exhaust ventilating systems are now afforded equal care in design and maintenance to that given other machinery more closely related to the Process. Methods of Dust Control "Dust control" is a general term descriptive of a number of methods used singly or together to prevent particulate atmospheric contamination. These methods are: in order .of their desirability, as follows: 1. Change of process. 2. Isolation of process. 3. Wet methods. 4. Ventilation. a. Local exhaust ventilation. b. General ventilation. 5. Personal respiratory protection. In ore-concentration plants it is seldom prac tical to change a process to eliminate the dust it creates It is possible in some cases to isolate a particular dust-producing operation from the rest of the plant, provided that constant attention on the part of the operators is not required. Frequently water is used in fine crushing and fine grinding, primarily to facilitate the processing of the ore and incidentally to allay the dust produced. Wet methods, however, are not feasible in coarse and secondary crushing operations, because of the relatively great volume of water required in instantly wetting each freshly fractured rock surface. Such quantities of water would entail conveying and storage difficulties. Local exhaust ventilation is the most effective and most commonly applied control measure, wherein directional air currents through the zone of dust production draw the contaminants into a duct system. Unfortunately, only a limited amount of reliable information on exhaust ventilation is available.2-5 of necessity these publications are rather general, being primarily concerned with engineering fundamentals. While many organizations have successfully

Jan 1, 1943

By Robert T. Pring

In addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of employees, with a consequent decrease in labor turnover rates. One progressive mining company' estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination decreases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor, Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flowsheet. Exhaust ventilating systems are now afforded equal care in design and maintenance to that given other machinery more closely related to the Process. Methods of Dust Control "Dust control" is a general term descriptive of a number of methods used singly or together to prevent particulate atmospheric contamination. These methods are: in order .of their desirability, as follows: 1. Change of process. 2. Isolation of process. 3. Wet methods. 4. Ventilation. a. Local exhaust ventilation. b. General ventilation. 5. Personal respiratory protection. In ore-concentration plants it is seldom prac tical to change a process to eliminate the dust it creates It is possible in some cases to isolate a particular dust-producing operation from the rest of the plant, provided that constant attention on the part of the operators is not required. Frequently water is used in fine crushing and fine grinding, primarily to facilitate the processing of the ore and incidentally to allay the dust produced. Wet methods, however, are not feasible in coarse and secondary crushing operations, because of the relatively great volume of water required in instantly wetting each freshly fractured rock surface. Such quantities of water would entail conveying and storage difficulties. Local exhaust ventilation is the most effective and most commonly applied control measure, wherein directional air currents through the zone of dust production draw the contaminants into a duct system. Unfortunately, only a limited amount of reliable information on exhaust ventilation is available.2-5 of necessity these publications are rather general, being primarily concerned with engineering fundamentals. While many organizations have successfully

Jan 1, 1943

By Robert T. Pring

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

Jan 1, 1940

By H. H. Vogel

THIS paper describes the milling practice and operating results of the recently installed heavy-media separation plant of Barton Mines Corporation, the world's largest producer of garnet. This pioneer application of heavy-media separation (sink-float) processes for the beneficiation of a nonmetallic ore is unique in many respects, the details of which will be apparent from the following presentation. CHARACTERISTICS OF THE ORE The property is on Gore Mountain, 5 miles west of the village of North Creek, New York, and 11 miles by road. The altitude of the mine is approximately 2800 feet. The valuable mineral, garnet, occurs in a surface deposit, the ore body being about ¾ mile long and varying in width from 50 to 300 ft. The garnet, principally almandite, Fe3A12 (Si04)3, occurs in a metamorphic rock of uncertain origin. The gangue mineral is principally hornblende, which constitutes from 40 to 80 per cent of the rock. The remainder of the gangue is divided between plagioclase feldspars and hypersthene, with smaller amounts of biotite, apatite and pyrite. The garnet content of the ore body varies from 5 to 20 per cent of the mass and averages about 10 to 12 per cent. The garnet occurs as crystals, mostly imperfectly developed, known locally as "pockets." These crystals vary in size from a fraction of an inch to a foot or more in diameter. Occasionally crystals have been found up to 30 and 36 in. in diameter but they average 4 to 6 inches. Nearly every crystal of garnet is surrounded by a rim of coarsely crystalline hornblende. The quarry faces are striking in appearance, showing crimson-red garnet crystals with their coal black rims scattered over a grayish black background. The specific gravity of the garnet is 3.8 to 4.1 while that of the hornblende ordinarily is 3.07 to 3.24. Some specimens of very dense hornblende have been found with a specific gravity as high as 3.40. The garnet crystals are laminated in structure, and readily cleave into flat, tabular pieces with sharp, chisel-like edges. Even when crushed to a very fine size, the garnet retains this flat, sharp, slivery grain shape. This characteristic, together with its hardness and toughness, gives it its value as an abrasive. FORMER OPERATIONS Mining operations have been carried on for 60 years. Until 1023, only the oxidized (soft rock) section of the ore body was mined. The oxidation, which affected the garnet only slightly, made possible the removal of the garnet from the rock by hand after it was blasted down, using small hand picks. In 1923 a mill was erected on the property, and was rebuilt and redesigned in 1928. Before the adoption of heavy-media separation, concentration was effected by

Jan 1, 1943

C. Q. Payne, New York City: Prof. Blake's inference that magnetic separation may be successfully employed upon smithsonite and iron oxide, after a preliminary roasting, is confirmed by the fact that this separation has been carried on with entire success for over a year at the works of the Wythe Lead and Zinc Mine Co., Austinville, Va. The ore mined on this property is a mixture consisting chiefly of galenite, smithsonite and limonite. The crude material is crushed, screened and washed in log washers for the removal of clay, and then jigged for the separation of the galenite. The zinc-and iron-ores are then roasted in reverberatory furnaces, being turned and moved towards the bridge-end of the hearth by manual labor. The roasted material contains from 20 to 26 per cent. of metallic iron. The slight difference in the specific gravities and the friable condition of the ores after roasting prevent the separation of the oxides by means of jigging. It was therefore the practice, previous to the use of magnetic separation, to charge the roasted material directly into the retorts of the zinc-furnaces. The rapid cutting of the retorts under this practice proved a serious inconvenience and expense. In the spring of 1892, the writer built for the Wythe Lead and Zino Mine Co. a magnetic separator which embodied several novel features and which was designed to treat the roasted zinc- and ironoxides. This separator has proved entirely successful for the purpose for which it was designed. During the first nine months of its operation, 1415 tons of 2240 pounds of roasted material were passed through the separator, producing about 675 tons of heads carrying from 50 to 55 per cent, of metallic iron, which are sold to a neighboring blast-furnace. The tailings, which contain the zinc, carry from 4 to 6 per cent. of metallic iron. For magnetizing the iron-ore previous to separating it from the zinc-ore, no change whatever mas made in the form of the reverberatory furnace previously employed. It was found that, by charging near the bridge-end of the hearth, toward the end of the roast-

Jan 1, 1894

By J. J. Gilman

The data presented indicate that the critical shear stress and strain-hardening Thedatapresentedrate of a zinc monocrystal depend on the orientation of its slip direction with respect to its external boundaries. The tendency of a crystal to form deformation bands also depends on its shape. THE plastic behavior of pairs of zinc monocrystals in which both members of the respective pairs had the same orientation with respect to the longitudinal axis, but each had different orientations with respect to their rectangular external shapes, were compared in this investigation. The purpose of the investigation was to see what influence the shape or surface of a zinc crystal has on its mechanical properties. In a previous investigation of triangular zinc monocrystals,1 anomalous axial twisting was observed which seemed to be related to the triangular shape of the crystals. Wolff,' in 400°C tensile tests of rectangular rock-salt crystals bounded by cubic cleavage planes, found that, of the four equivalent slip systems, the two with the "shorter" slip directions yielded and produced slip lines at lower stresses than the other two. This observation and the work of Dommerich³ as formulated by Smekal4 as a "new slip condition" for rock-salt: "among two or more slip systems permitted by the shear stress law, with reference to the formation of visible slip lines by large individual glides, that slip system is preferred which has the shortest effective slip direction." More recently, Wu and Smoluchowski5 reported essentially the same effect for ribbon-like (20x2x0.2 mm) aluminum crystals at room temperature. Experimental Chemically pure zinc (99.999 pct Zn), purchased from the New Jersey Zinc Co., was the raw material. Glass envelopes, containing graphite molds and zinc, were evacuated while hot enough to outgas the graphite but not melt the zinc. At a vacuum of about 0.2 micron the envelopes were sealed off and then lowered through a furnace at 1 in. per hr so as to melt and resolidify the zinc and produce mono-crystals. One-half of one of the molds is shown in Fig. la. Each mold consisted of four pieces from a cylindrical graphite rod that was split longitudinally and transversely at its midpoints. Rectangular milled grooves 0.050 in. deep and % in. wide formed the mold cavity when the split halves were assembled with twisted wires. Fig. lb shows the specimen shape obtained when the top and bottom mold-halves were rotated 90" with respect to each other. Good fits prevented leakage and excess zinc was necessary to provide enough liquid head to fill the mold completely. In removing soft crystals from the molds it was impossible to avoid small amounts of bending. However, manipulations were carried out whenever possible with the crystals protected by grooved brass blocks. All specimens were annealed prior to testing. From the top and bottom sections of each crystal, X-ray specimens and tensile specimens 7 to 8 cm long were sawed. The tensile specimens were annealed inside evacuated tubes for 1 hr at 375°C. Next the crystals were cleaned and polished by 2-min dips in a solution of 22 pct chromic acid, 74 pct water, 2.5 pct sulphuric acid, and 1.5 pct glacial acetic acid.' Cleaning was followed by a 10-sec dip in a 10 pct caustic solution, then washed in water and alcohol, and dried. This treatment results in a bright surface covered by an invisible oxide film. The testing grips were a slotted type with set screws and were supported in a V-block during the mounting operations in order to avoid bending the crystals. A schematic diagram of the recording tensile-testing machine is shown in Fig. 2. The machine has been described elsewhere.' The head speed was 0.3 mm per sec for all tests. The crystal orientations were determined by the Greninger X-ray back-reflection method with an estimated accuracy of 1. Description of Crystal Geometry A schematic picture of a rectangular zinc mono-crystal is shown in Fig. 3. ABD designates the front edge of a basal plane (0001) of the crystal, the only active slip plane for zinc at room temperature. Of the three possible (2110) slip directions, the active one is indicated by an arrow. Cartesian coordinates are taken parallel to the specimen edges. The normal, n, to the basal plane (n is parallel to the hexagonal axis) has the direction cosines a, ß and ?. X0 = 90 — y is the angle between the longitudinal axis and

Jan 1, 1954

By C. G. Durdaller, W. H. Robinson, G. M. Pound

The nucleation rate of the a (pay) to 0 (white) tin transformation was measured as a function of temperature and a tin particle size using an X-ray diffraction technique. The powder specimens of a tin were essentially monodisperse and the small dinzension of the particles of these specimens was varied from 13 to 75 p. Several types of nucleation sites of differing potency were fbund to be operative in the nucleation process, but it could not be determined whether these sites were on the free surface of the tin particles or within the volume. Assuming that they were on the free surface, the average density of the most potent sites was calculated to be 2.5 to 5.3 x 10' sites per sq cnz through the application of a Poisson distribztion finction to the isothermal data. Analysis of the temperature dependence' of the rate constmts at a given fraction transformed suggests that the active sites are regions of higher free energy and not catalytic interfaces. Appreciable induction periods were observed at the lower temperatures of transformation. Experimental studies1 of solid-solid phase transformations have led to the belief that the new phase nucleates at structural imperfections. The purpose of the present work was to learn more about the mechanism of nucleation in solids and the nature of the singularities at which nucleation occurs. In this investigation nucleation rates in the isothermal transformation of gray to white tin were measured by an X-ray diffraction technique using essentially monodisperse powders of gray tin. This particular phase transformation was chosen for study because it presented fewer experimental difficulties than most others. The experimental temperature-control problems were minimal because the two phases coexist in equilibrium at 13.3"C, and measurable transformation rates occur at temperatures only slightly above room temperature. The growth rate of the P phase into the a2 is sufficiently fast to make the measured transformation rate equivalent to the nucleation rate, provided that the particle size of the samples is small enough; for the experimental temperatures used in this study, the particle diameter must be less than 100 p. EXPERIMENTAL TECHNIQUE The P tin used in this study was obtained from Capper Pass and Son Ltd., North Ferriby, Yorkshire, England, and was of 99.999 pct purity. It was transformedS to the a phase and ground into a fine powder in an agate mortar. This powder was separated by a Roller air classifier into seven fractions whose dimensions, as determined by microscopic measurement of many thousands of particles, are given in Table I and whose distribution of size within each fraction is given in Figs. 1 and 2. The shape of the particles was roughly that of an oblate spheroid,

Jan 1, 1964

By C. W. Spencer, J. Singer

A PARTIAL phase diagram for the As-Te system is given in Hansen.' The only compound reported is As2Te3, melting at 362°C. Stoichiometric quantities of reagent-grade elements were reacted in evacuated quartz and directionally cooled. The resulting ingot consisted of very thin threadlike crystals from which only very small single-crystal fragments were isolated. A powder diffraction diagram disclosed nonisomorphism with the analogous V-VI compounds insofar as these have been reported; Sb2S3, As2S3, Bi,S,, and Bi2Te3 data in the ASTM index of powder patterns, together with the single-crystal data on Sb2Se3,2 were used for the com- parison with the observed spacings. Single-crystal data confirmed the uniqueness of the As2Te3 structure. Single-crystal Weissenberg diagrams have so far yielded the following data: As2Te3 is monoclinic, space group C-m (OkO data still lacking), a = 14.4A, b = 4.05A, C = 9.92A, ß = 97". The cell volume is about 5802. The set of isomorphous ortho-rhombic cells of Sb2Se3, Sb2S3, and Bi2S, are apparently related to As,Te, in having one lattice constant close to 4.0 and with cell volumes as large as 540A8. Assuming Z = 4 for As2Te3 also, the density is calculated as 6.1 which agrees well with a roughly determined value of 6.0. A complete structure analysis is under way.

Jan 1, 1956

By H. E. Rorschach

Oil-field activities in Oklahoma made 1936 the best year since 1930. Approximately 2800 wells were completed, an increase of about 20 per cent over 1935. Purchasers' reports filed with the Corporation Commission showed a total of 200,240,252 bbl. of oil purchased from leases in 1936. The assembly of a complete table of the oil fields of the state was not achieved, as many of the early records of operators and pipe-line companies are not complete, and data for the older fields will perhaps never be fully tabulated. Table 1 includes all of the new fields and most of the important fields of the State of Oklahoma. The outstanding developments of the year were: the discovery of rich Wilcox-sand production in the Moore pool; the spectacular drilling campaign in the Capitol or Mansion extension in the Oklahoma City pool; the surprising extension of the Olympic pool and the Hunton lime zone in the Fitts pool; and the failure to find more Ordovician production in southern Oklahoma. Wildcat discoveries, which were on a par with 1935, resulted in the discovery of such promising pools as Billings-Wilcox, North Bethel, North Earlsboro and North Lucien. The Fitts-Upper Simpson, Edmond, Jesse, Keokuk Falls and South Burbank pools underwent considerable development. Fitts Pool.—The Fitts area in Pontotoc County was greatly extended during the year and was the leader in drilling activity in the state. The producing limits were pushed to the east and north and the development of the Hunton lime horizon was outstanding. In the Upper Simpson zone 162 wells were completed; 137 in the Hunton lime zone and 26 in the Wilcox zone. The Oil Creek zone, a sand body below the Wilcox member, was discovered by the Magnolia-Statler No. 3 well located in the 1/4. 1/4 of sec. 28-2N.-7E. Moore Pool.—The Moore pool, in Cleveland County, which was opened in 1935 by the Sinclair Prairie-Franklin Community No. 1 well, surprised the oil industry when the Sinclair Prairie-Marvel No. 1 well, on Apr. 1, 1936, discovered a rich body of Wilcox sand below the distillate

Jan 1, 1937

THE slag performs two useful functions in open-hearth steel- making. First, it is the means of disposal of all the impurities, save carbon, which are removed from the charge materials in refining the steel, so it must be suited to receiving and retaining as much as possible of undesirable elements with minimum loss of iron and useful alloying elements. Second, the slag serves as a buffer between the flame and the bath and transfers oxygen to the metal at a measured pace contrasted with the violent and difficultly controlled oxidation of the bessemer process. At the same time, the slag is a thermal insulator that limits the rate at which heat can be delivered to the metal from the flame, and a heavy slag blanket thereby serves as a brake on production rates. It has been said with justification that the secret of good steel- making is to make a good slag and the steel will take care of itself. In a broad sense, the subject of slag control includes not only the adjustment of the composition of the slag but also of its relative weight in terms of percentage of the metal-bath weight. The slag is made up essentially of: (1) oxides formed by oxidation of silicon, manganese, phosphorus, and iron in the charge, (2) Si02, MnO, MgO, and other oxides charged as such or introduced incidentally with ores or fluxes or by refractory erosion, and (3) lime charged or fed to the heat to neutralize the "acidic" oxides present (Si02 and P205). Obviously, if practically perfect control were possible over the composition of the charge as well as over the oxidation process during the melting period, both slag weight and composition would be very nearly predetermined; and the control problem would be solved. Unfortunately, only a somewhat imperfect control over these factors is possible, so the operator must begin during the lime boil and continue through the refining period to discover and correct departures from the normal pattern of slag development. To do this as the heat progresses, the first helper must be able to make quick estimates of the composition and physical state of develop-

Jan 1, 1964

By N. J. Grant, A. W. Mullendore

Three aluminum alloys of 0.94, 1.92, and 5.10 pct Mg, prepared from very high purity metals, were tested at 500°, 700°, and 900°F in creep rupture. The degree of strengthening through solid-solu-tion alloying and the effects on the deformation characteristics and fracture were examined. The ductility of the alloys as a function of stress and temperature was closely followed. STUDIES of the creep process in pure metals in recent years have done much to expand the understanding of the fundamental deformation and recovery processes that contribute to overall creep behavior. In order that this knowledge may be applied to commercial alloys, it is necessary to know the principles governing the effect of alloying on the mechanisms of creep. A limited amount of work has been performed in this field, but few investigators have attempted to follow the changes in particular creep mechanisms with alloying. Recently, studies of the effects of solid-solution alloying on the plastic properties of aluminum have been conducted by Dorn, Pietrokowsky, and Tietz,1 Sherby, Anderson, and Dorn,2 and Sherby and Dorn.3 This paper presents the results of an investigation of the effect of solid-solution alloying of high purity aluminum with magnesium on the creep-rupture properties, and correlates these observations with changes in the creep mechanisms. This work is thus an extension of the creep-rupture observations of Servi and Grant4,5 and the deformation studies of Chang and Grant.6,7 Experimental Procedure Three alloys of aluminum containing approximately 1, 2, and 5 pct Mg were tested. These alloying additions are all within the solid-solubility limit at the testing temperatures.' The analysis of the materials is presented in Table I. The tests fall into two categories: l—creep-rup-ture tests at 500°, 700°, and 900°F, and 2—structure study tests performed primarily at 700°F. Speci-mens of 0.160 in. diameter with milled flats for metallographic observations" ' were utilized for the structure studies. All specimens were annealed in one step to give the desired grain size for the tests. Table II presents the annealing data and final grain sizes. The specimens were polished electrolytically before testing with Jacquet solution (2/3 acetic anhydride, 1/3 perchloric acid) at 25" to 30°C, and 15 to 20 v. Creep-rupture testing was performed under constant load with the apparatus previously described." Results and Discussion Creep-Rupture Properties: The log-log plots of creep-rupture data are presented in Figs. 1 and 2. For these very pure single-phase alloys, the minimum creep rate and the rupture life both exhibit straight-line dependence on stress in this method of plotting as they have for commercial alloys0,10 and for pure aluminum." Curve breaks, based on the use of straight-line segments, at 500°F have been found by metallographic study to correspond to a transition from low to high temperature behavior and so represent zones of equicohesion. Specimens on the high creep-rate side of the break showed normal granular deformation processes whereas those on the low creep-rate side showed rapidly increasing grain-boundary sliding and migration with extensive evidence of intercrystalline cracking at 500°F. Two micrographs of the 0.94 pct Mg alloy, Fig. 3, show the increased participation of the grain boundary in the deformation process at 500°F with decreasing stress. In Fig. 3a is shown the structure of a specimen which exhibits little deformation along the grain boundaries and failed transgranularly; in Fig. 3b is shown the increased deformation along the grain boundaries at a lower stress for a specimen which showed appreciable intercrystalline cracking. The severity of intercrystalline cracking increased with increasing magnesium content at 500°F. Intercrystalline cracking disappeared in most of the specimens at 700°F and persisted only in the 5 pct Mg alloy at high creep rates. At 900°F all of the specimens deformed with extensive grain-boundary participation, including extensive grain-boundary migration. None of the alloys at 900°F showed intercrystalline cracking.

Jan 1, 1955

By Victor L. Stevens

The Oso tunnel is one of three tunnels located on the San Juan-Chama Project in south-central Colorado. The purpose of the tunnel is to carry water from the upper San Juan watershed through the Continental Divide into the Rio Grande watershed. The Oso tunnel contract was awarded by the U.S. Bureau of Reclamation to a joint venture of Boyles Brothers Drilling Co., Gibbons & Reed Co., and Cimco in February 1966. The Oso tunnel is 26,660 ft long and has a rock section of 10 ft, 2 in. with a lined diameter of 8 ft circular. The main portion of the rock formation was in the Lewis shale. This formation is quite consistent in hardness and texture with exception of localized limestone concretions and sandy siltstone inclusions. The job was bid on the basis of using a James S. Robbins mole of the P221 series. The decision for using a mole was predicated on the geology and the experience of the same joint venture on the adjoining Azotea tunnel where a mole was successfully used. The Robbins P221 series mole is capable of cutting from 9 ft, 11 in. to a 10 ft, 7 in. diam without any major change. It is 40 ft long and weighs 60 tons. The cutting head has 22 disk-type cutters and one center pilot (standard 9 7/8 -in.) tricone bit. The head is powered by four 75 hp electric motors. Gripper pads at about the midway point on each side of the machine are pushed into the tunnel ribs and thrust-cylinders in front of each gripper apply pressure to the face as the head rotates. The regripping cycle is 3 ft and then the grippers are retracted and advanced. Each cutter on the perimeter of the head is followed by a bucket which scoops up the cut material, almost in the same manner as a water wheel, and dumps it into a conveyor situated along the top of the mole. The muck from the mole conveyor is dumped into a gantry-type conveyor. The gantry conveyor is 350 ft long and is pulled

Jan 1, 1970

By Charles E. Lundin

The character of the Er-D system was established by determining pressure-temperature-composition relationships. A Sieuerts&apos; apparatus was employed to make measurements in the temperature range, 473" to 1223"K, the composition range of erbium to ErD3, and the pressure range of 10~s to 760 Torr. The system is characterized by three homogeneous phase regions: the nzetal-rich, the dideuteride, and the trideuteride phases. These phases and their solubility boundaries were deduced from the family of isotherms of the system zchich relate the pressure-temperature-composition variables. The equilibrium plateau decomposition relationships in the two-phase regions were determined from can&apos;t Hoff plots to be: The differential heats of reaction in these two regions are AH = - 53.0 * 0.2 and -20.0 *0.1 kcal per mole of D2, respecticely. The differential entropies of reaction are AS = - 36.3 * 0.2 and - 31.0 * 0.2 cal per mole D2. deg, respectively. Relative partial molal and intepal thermodynamic quantities were calculated from the pure metal to the dideuteride phase. The study of the Er-D system was undertaken as a logical complement to an earlier study of the Er-H system.&apos; The primary interest was to compare the characteristics of the two systems and relate the difference to the isotopic effect. Studies of rare earth-deuterium systems by other investigators have been very limited in number and scope. Furthermore, there is even less information available wherein an investigator has systematically compared a binary rare earth-hydrogen system with the corresponding rare earth-deuterium system. The available information consists primarily of dissociation pressure measurements in the plateau pressure region of a few rare earths. Warf and Korst&apos; determined dissociation pressure relationships for the La- and Ce-D systems in the plateau region and several isotherms for each system in the dideuteride region. They compared these data with those of the corresponding hydrided systems. The study of these systems as a whole was very cursory and did not give sufficient data for a thorough comparison of the effect of the hydrogen vs the deuterium in the respective rare earths. The heat capacities and related thermodynamic functions of the intermediate phases, YH, and YD2, were determined by Flotow, Osborne, and Otto,~ and the investigation was again repeated for YH3 and YD3 by Flotow, Osborne, Otto, and Abraham.4 This investigation studied only these specific phases. Jones, Southall, and Goodhead5 surveyed the hydrides and deu-terides of a series of rare earths for thermal stability including erbium. They experimentally determined isotherms of selected hydrides and plateau dissociation pressures for deuterides. These data allowed comparison of the enthalpy and entropies of formation of the dihydrides and dideuterides. To date, no one rare earth has been selected to thoroughly establish the complete pressure-temperature-composition (PTC) relationships of binary solute additions of hydrogen and deuterium, respectively. The objective in this investigation was to provide the first comparison of a complete family of isotherms of a rare earth-deuterium system with those of a rare earth-hydrogen system. This would allow one to determine what differences exist, if any, in the various phase boundaries and the thermodynamic relationships in various regions of the systems. I) EXPERIMENTAL PROCEDURE A Sieverts&apos; apparatus was employed to conduct the experimental measurements. Briefly, it consisted of a source of pure deuterium, a precision gas-measuring buret, a heated reaction chamber, a mercury manometer, and two McLeod gages (a CVC, GMl00A and a CVC, GM110). Pure deuterium was obtained by passing deuterium through a heated Pd-Ag thimble. A 100-ml precision gas buret graduated to 0.1-ml divisions was used to measure and admit deuterium to the reaction chamber. The reaction unit consisted of a quartz tube surrounded by a nichrome-wound furnace. The furnace temperature was controlled by a recorder-controller to . An independent measurement of the sample temperature in the quartz tube was made by means of a chromel-alumel thermocouple situated outside, but adjacent to, the quartz tube near the specimen. Pressure in the manometer range was measured to k0.5 Torr and in the McLeod range (10~4 to 10 Torr) to *3 pct. The deuterium compositions in erbium were calculated in terms of deuterium-to-erbium atomic ratio. These compositions were estimated to be *0.01 D/Er ratio. The erbium metal was obtained from the Lunex Co. in the form of sponge. The metal was nuclear grade with a purity of 99.9+ pct. The oxygen content was reported to be 340 ppm and the nitrogen not detectable. Metallographically the structure was almost free of second phase (<i vol pct). A quantity of sponge was arc-melted for use as charge material. The solid material was compared with the sponge in the PTC relationships. They were found to be identical. Therefore, sponge material was used henceforth, so that equilibrium could be attained more rapidly. The specimen size was about 0.2 gr for each loading of the reaction chamber. The procedure employed to obtain the PTC data was to develop experimentally a family of isothermal curves of composition vs pressure. First, a specimen

Jan 1, 1969

By Herbert H. Uhlig

ALTHOUGH the mechanical properties of high-carbon manganese-iron alloys, particularly the Hadfield manganese steels, have been established, the literature discloses discrepancies in the reported properties for the low-carbon alloys. Hadfieldlo summarized the existing data up to 1927, including the investigations of Guillet, Arnold, Strauss, Burgess and Aston, and reported his own values for alloys containing for the most part from 0.06 to 0.15 per cent carbon. He noted: From these comparisons it will be seen that while there is a broad and general agreement as to the character of the alloys at the different manganese percentages, there are disparities in individual cases, especially as regards the degree of toughness or brittleness displayed by an alloy with certain percentages and with particular types of treatment. These differences are not always readily explainable. Ib His data showed that alloys containing 4 to 10 per cent manganese water-quenched from 1000°C. were brittle and hard with maximum brittleness at about 7 per cent. Slight improvement in ductility was obtained with compositions from 10 to 17 per cent manganese. Alloys containing up to 17 per cent manganese slowly cooled rather than quenched from 870°C., he found, were slightly improved in ductility with significant improvement in alloys analyzing 4.1 and 4.8 per cent manganese. Recently Walters, Kramer and Loringa reported mechanical properties for alloys made up from electrolytic manganese and ingot iron and containing from 0.02 to 0.04 per cent carbon. They showed that a tempering treatment at 540°C. (1000°F.) for one hour significantly improved the ductility of compositions ranging from 6.7 to 20.7 per cent manganese. The differences of these compared with Hadfield&apos;s results they considered to originate in this tempering treatment plus the fact that Hadfield&apos;s alloys contained higher carbon and phosphorus (0.06 to 0.15 per cent C; 0.06 to 0.07 per cent P compared with 0.02 to 0.04 per cent C, <0.001 per cent P). In this paper it is shown that of the low- carbon alloys (0.02 to 0.03 per cent) containing from 3.3 to 21.5 per cent manganese moderately or rapidly quenched from 1000°C. some are brittle or ductile, depending on presence or absence of hydrogen. Hydrogen is readily absorbed at high temperatures, and much of it is retained when the alloys are cooled to room temperature. The presence of hydrogen in the range of composition from 10 to 18 per cent manganese is a major factor in determining relative ductility. At 22 per cent manganese, and also at compositions below 10 per cent manganese, factors other than or in addition to hydrogen play a role. These are discussed. Also data are presented to show that hydrogen absorbed by the high-carbon alloys of Hadfield composition is without effect on their mechanical properties.

Jan 1, 1944

By John E. Lanning

During the last decade, since most smelters have included Cottrell plants as standard equipment for the removal of dust from furnace gases, it has become apparent that smeltermen have had a new problem slowly developing. This problem has manifested itself in accelerated destruction of, or serious injury to, the masonry of flues and chimneys. The masonry either spalls, if the material is of low strength, or acquires large major cracks, either of which conditions attains such proportions that renewals or reinforcing become necessary to maintain the structure in satisfactory condition. This paper describes the failure of a large modern brick chimney to such an extent that its safety was vitally impaired; the investigation of its condition; the methods of restoring satisfactory strength to the structure; and the installation of an acidproof lining. Plant History The Clarkdale smelter of the United Verde Copper Co., which was put in operation in 1915, was primarily a blast-furnace plant. The smelter at Jerome had utilized blast furnaces exclusively, and in the design of the new (1915) plant, blast-furnace smelting evidently was considered of major importance, the smelting equipment consisting of four blast furnaces 48 in. by 26 ft. 8 in. and three reverberatories, each 19 by 101 ft. The latter, supplemented by roasters, were intended mainly for handling dust and fine ore resulting from the crushing operations. The original roasting equipment consisted of six six-hearth Wedge roasters, six more being added in 1917. All gases from blast furnaces, reverberatories, roasters and converters were conducted by means of suitable flues and dust chambers to one central chimney. This chimney, 30 ft. inside diameter by 400 ft. high, is a self-supporting steel structure, lined with 4-in. brick supported on steel shelf angles, riveted to the shell, spaced about 15 ft. vertically. The bricks were of local manufacture, not particularly hard-burned, and were laid in ordinary cement-fireclay-sand mortar. No record is available to indicate that any particular effort was made to secure an acidproof mortar. The same materials were employed in the construction of the reverberatory and roaster flues, and the roaster dust chamber. Parenthetically, it may

Jan 1, 1934

By C. S. Anderson

Georgia, since 1829, has produced nearly $18,000,000 from her gold mines, but in late years the output has dwindled to insignificance. In view of present universal efforts to increase gold production, it seems pertinent to record some recent observations in that field, briefly review its past and weigh probabilities of reviving gold mining there. Little in this paper can be claimed as new or original, and it does not present results of a detailed or profound investigation of the whole region. The Allatoona gold mine was reopened in January, 1932, and explored at greater depth during the period from January to June of that year. A number of other abandoned mines were visited, but since the workings, in common with most such mines in Georgia, were flooded or caved, underground conditions could not be examined. For a wider knowledge of the subject, a search was made through available pertinent literature and statistics, a bibliography of which is appended hereto. To all the sources obligations are gratefully acknowledged. Production The discovery of gold in Georgia, in 1829, led to an influx of 6000 to 7000 miners and a production of over $200,000 in the following year. A branch of the United States Mint, established at Dahlonega in 1838, accounted for $6,115,569 up to the time of the Civil War. The output fluctuated greatly from year to year, with an all-time peak of $582,782 in 1843. In only one other year, 1845, was the half million mark exceeded. After the war mining began again, but 1883 is the last year for which an output of $200,000 is reported. Placers, always the main source of production, were yielding less and less, and in spite of increased quartz-mining activities the downward trend continued. The last year in which there was a production of $100,000 was 1902. In 1914, $16,270 came from 26 placers and 11 deep mines, with the latter reporting 1750 tons of $3 average value. In 1925, one placer and four lode mines that mined 8100 tons assaying $1.19 per ton produced $9500. One placer and one quartz mine, operating in 1930, reported a total output of $4194. Table 1 pictures the waning output.

Jan 1, 1934

By Victor A. Phillips

A series of specimens of a Cu- 3.23 pct Co alloy were prepared with particle diameters from zero to 590A. The samples were then cold-rolled 95 pct and the effects of the particle size on the behavior on annealing for hr at temperatures between 100" and 900°C were studied (by hardness, light, and electron metallography). Particles, particularly for d r 105 to 590A, greatly impeded softening and vecvystallizn-tion, and tended to give elongated grains. Particles deformed fairly homogeneously with the ,matrix, be- IN a previous study by the author,&apos; the growth of cobalt-rich precipitates was followed electron microscopically in Cu-3.12 Co alloy as a function of aging, typically at 650°C. The coherent spherical precipitates grew to 520 + lOOA average diam before spontaneously losing coherency and developing (111) facets. Stretching a few percent after precipitation 2aused loss of coherency to occur sooner at about 220A average particle diam. The particles apparently retained their fcc structure after loss of coherency. coming lau2ellae. For d = 55 to 180A, these lamellae gave streak-contrast effects apparently due to coherency strains , and spheroidized on annealing at 600" to 650°C, forming coherent particles. Particles of d = 250 ov 320A lost coherency during t-olling, giving incoherent lamellae. Recrystallization apparently occured by growth of new grains into unrecrystallized (recovered) material at temperatures below that at which cobalt atoms had much mobility. The present study was undertaken to explore the effect of cobalt-rjch particles of various average sizes from 50 to 600A diam on the isochronal annealing behavior of copper after heavy cold rolling. The previous work&apos; was used as a guide in preparing the two-phase series of prerolling structures. The solution-treated alloy was also rolled for comparison. A further question of interest in the present study was whether dislocation and particle hardening were additive, since the prerolling structures covered the full range unaged - peak aged — overaged, and further precipitation might occur on annealing after cold rolling. Although there have been exhaustive studies of the isothermal2"6 and is~chronal annealing behavior of

Jan 1, 1967

By H. Landsberg

SUBSIDENCE caused by mining operations has been a matter of interest for the mining engineer for just 111 years, since the Belgian Committee for study of subsidence in the city of Liege submitted its first report in 1825. This interest is fairly expressed in the enormous amount of literature that has since appeared on this subject. A bibliography, probably far from being complete, which preceded this study as a pre-liminary survey, comprises more than 800 titles. In spite of this fact the problem remains today as acute as it has ever been. The questions of as good a recovery as possible of the national resources, the safety of the operations, and the protection of private and public property are the important angles from which to look at the problem.

Jan 1, 1936

By Ira B. Jorafemon

In the interesting Institute symposium of the preservation of peace by force, through mineral control, one important aspect of the question was not presented. This is the responsibility the United Nations, and particularly the United States, will incur the through limitation of the economic activities of nations that are now friendly to us, as well as of nations that are enemies or are under the control of enemies. After the war all nations, friends as well as enemies will be poor. Hunger and bankruptcy will, will like the sword of Damocles, hang over the heads of all of us on this blundering planet. When the actual fighting is over, there will be a universal attempt to squirm out from under the sword by resuming production of peacetime goods, for trade as well as immediate consumption.

Jan 1, 1944

By Reynold Q. Shotts

The small domestic underfeed stoker as now designed is unusually sensitive to the coking and plastic properties of coals, and when the attempt is made to burn the high rank coking and caking coals of the Appalachian fields, serious trouble may occur. Part of the trouble may be caused by the ash content and clinkering characteristics of the particular coal in use, but more often it is the result of an excessive ac-in of coke in the form of &apos;&apos;trees,, or masses in the fuel bed. Often the zone of burning becomes so restricted that the fire goes out, and in extreme cases the fire may be lifted completely out of the fuel bed and away from the air ports. Even if the fire is preserved, excessive coking may cause response to subsequent heat demand to be slow and irregular. Coke trees seem to grow most readily during periods of hold-fire operation, so that in order to preserve the fire in mild weather it is often necessary to set the timer for such a long operating period each hour that much unneeded and unwanted heat is developed, causing discomfort. During demand periods the fire may pick up so slowly that the intense burning which develops just before stoker cut-off causes a serious overshooting of the thermostat. Stoker coal performance tests which have been made in a number of labora- tories1,2,3,4,5 are one method of approach to the problem Of selecting stoker coals- As yet these tests have not been standardized and they are expensive and time-consuming. The value of the results probably increases with the length of the test. Sherman and co-workers at Battelle Memorial Institute believe that even a one-week test is not too reliable a trial2 and it is quite likely that Others will agree. A great advantage of such tests is that characteristics of coals, other than the tendency to form coke masses, may be evaluated from them. The selection of stoker coals would be greatly facilitated if there existed some simp1e measure Of the tendency Of a a to form coke in a fuel bed. Although possessing all Of the disadvantages Of any small-scale laboratory test, the test for the free-swelling index of coal has been found useful for evaluating the probable effects Of swelling properties upon combustion.7 Ostborg, Limbacherand Sherman, have shown that the test can Predict, roughly, the tendency Of coke to accumulate in the fuel bed Of a domestic stoker. They also gave instances of its value in predicting combustion behavior in some large installations. The use of the test for free-swelling index has become well established and has been adopted as a standard by the American Society for Testing Materials.8 When domestic stoker coal investigations began at the State Mine Experiment Station in the summer of 1944, it was decided

Jan 1, 1949