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Jan 1, 1884

By John H. Bassarear, A. A. Dor

INTRODUCTION Primary grinding mills as defined in this paper, are autogenous or semi-autogenous rotating, tumbling mills having a coarse feed with a top size usually varying from 150 to 300 mm (6 to 12 inches). Most frequently, the feed to these mills is the product of primary crushing plants but in some cases run of mine ore is used as feed such as at Benguet, McDermitt, L-Bar Sohio, Bear Creek and others. The size of the largest lumps in the mill feed is principally determined by limits set by the mill feed trunnion diameter and by the type and size of conveying equipment used for handling and of bins and stockpiles used for storage. The use of primary mills in mineral processing plants has expanded very significantly in the last twenty years, and they have been successfully applied to the treatment of a wide variety of ores in both wet and dry grinding applications. In the present state of technological development for primary grinding mills, there is a wide choice of acceptable options with respect to type and size, grinding flowsheet and grinding media. The choice of the optimum combination which would result in the most satisfactory condition of operation, from the standpoint of both metallurgical results and costs, depends on the nature of the ore, the required characteristics of the grinding products and on various geographic and economic circumstances. The effects of such factors and considerations on the choice and sizing of primary grinding mills and flowsheets are reviewed and discussed in the following pages. PRIMARY MILLS SELECTION Inherent Characteristics of Primary Grinding Primary grinding is complex because it involves several comminution mechanisms which occur simultaneously and to some degree interfere with one another. These mechanisms of impact, attrition and abrasion have been described earlier. The relative importance of these three main grinding actions and their mutual balance resulting in a continuous uniform operation of the mill depend to a very large extent on the nature of the ore and its physical properties. Homogenous, single mineral ores will behave quite differently from heterogenous ores consisting of different minerals bound together along defined

Jan 1, 1982

By Mark J. Klein, Robert A. Haggins

The pesence of a small amount of oxygen was found to cause significant grain growth restraint in 99.99 pct Ag. This behavior does not seem to be due to the presence of an oxide dispersion, but instead, to be related to the existence of minute amounts of oxygen m solid solution. In the amounts necessary to cause the observed effects it was found that oxygen migrates with extreme rapidity, probably along extended structural imperfections, such as dislocations and grain boundaries. A number of years ago, hastton' observed that the presence of small amounts of oxygen caused a retardation of grain growth in silver. He attributed this behavior to the formation of a fine dispersion of oxide particles by the internal oxidation of trace impurities. More recently, wood2 also found that oxygen caused grain growth restraint in copper. Experiments using both copper and a dilute solution of aluminum in copper led to the conclusion that the effects observed in copper were due to oxygen in solid solution, rather than an oxide dispersion. During the course of a study of the influence of several solutes on the recrystallization of Silver, the presence of minute amounts of oxygen was found to exert a very significant influence on grain growth. The experiments reported here were undertaken to determine whether the grain growth restraint observed in silver due to the presence of oxygen is related to oxygen in solution or to an oxide dispersion. Because of the difficulty in measurement and control of the very small oxygen concentrations causing the observed effects no attempt was made to treat the data in a quantitative manner. EXPERIMENTAL PROCEDURE AND RESULTS Silver of 99.99 pct purity was melted and cast into slabs in a vacuum of better than 0.1 p. These slabs were reduced 50 pct by cold rolling to a thickness of approximately 2.5 mm. Samples cut from this material were annealed in vacuum for a series of different times at 803°C. Another group of samples was similarly annealed in air. This temperature is well above the recrystallization range for silver of this purity (150" to 200°C). The mean grain diameter of these samples was measured, both in the center and near the edge, using the line-intel-cept method, and is shown as a function of annealing time in Fig. 1. The grain size in the centers of the samples annealed in air was found to be larger than that of the surface regions, while the grain growth behavior of the edge and center regions annealed in a vacuum was approximately the same. he edge measurements were taken at a distance of 0.2 mm from the surface.) A few samples were annealed in nitrogen. Their behavior was identical to that of the vacuum-annealed samples. Samples annealed in oxygen had approximately the same grain growth behavior as those annealed in air, leading to the conclusion that this behaviouer is due to oxygen. The microstructure of a sample annealed in air at 803" for. 30 minutes is shown in Fig. 2. The smaller grain size near the surface is characteristic of the iir-annealed specimens. Possible causes of this grain growth restraint in the air-annealed specimen are the formation of an im-

Jan 1, 1962

By W. H. Adams

Virginia, a store-house of metals, is more and more a surprise to the present generation. With her enormous available mineral wealth, worked upon steadily for over a century, exploited SUEciently to demonstrate beyond question costs and values, reported upon by our most eminent scientists, written up by thoroughly earnest correspondents, we yet find her little understood by capitalists or practical men, and until very lately overlooked by the advanceguard of pioneers in metallurgy, whose restless energy conquered the wilderness of Northern Michigan years ago, and has written a new and startling history for almost impenetrable Western territories. The world is learning through the mouths of giant furnaces lately put in blast at Lowmoor, Goshen, and Roanoke, more of this wondcrful State. It is becoming plain that nearer home, amid all the surroundings of civilization, under an equable climate and with the advantage of a minimum cost for fuel and labor, there are stores of mineral, varied in character and deposited over a wide area, which exceed all ordinary calcnlations. Principal among these minerals, iron ores have been, and will probably continue to be, the leading product and the source of greatest revenue. My attention has been called during the past year to one particular section of the iron-belt, where for forty years charcoal-furnaces were successfully operated, the ores being mined in open pits, as can so frequently be seen from the Connecticut line southward into Georgia. There is, however, a significant peculiarity in the character of these deposits of Louisa county warranting special mention, as it is thought that nowhere on the earth's surface, within so moderate a distance of tidewater, can their like be fouad. Probably half a million tons of lump and wash-material have been taken from pits

Jan 1, 1884

By John D. Sullivan, Edwin J. Rogers, Chester R. Austin

THE problem of making a building unit combining the necessary physical and mechanical properties and good thermal insulation has been foremost in the minds of architects and ceramic and construction engineers for many years. This paper presents the results of studies on thermally expanding shales or clays to produce light-weight cellular products suitable for making building units. An expanded clay block suitable for building purposes should be large enough so that substantial savings may be effected in labor costs in laying the wall. The permeability should be low and it should have sufficiently good "dry-wall" characteristics to permit exposing the exterior surface to the elements, and to permit plastering directly the inside wall surface. The thermal conductivity should be low and the mechanical properties should be adequate. Obviously, a unit possessing satisfactory qualities for constructing an outside wall would be satisfactory for interior walls and for back-up purposes. The results of studies on bloating various shales or clays† and the properties of the expanded products are reported. In another paper1 basic factors involved in bloating of clays are discussed. Manufacturers of ceramic products, particularly structural clay, may encounter bloating of the ware during burning, and precautions must be followed to avoid this phenomenon. About 1927 the C. F. Burgess Laboratories, Madison, Wis., while carrying on an investigation for the American Face Brick Research Corporation, conceived the idea of intentionally bloating clay while holding it in a restrained condition, with the hope of producing a unitary cellular mass. Work was carried on until about 1931, when studies were terminated because of business conditions. These studies were continued later by The Western Brick Co., Danville, Ill., which developed a process of "inwardly expansive bloating." The major purpose of the latter investigation was to produce back-up tile to compete with concrete blocks made from Haydite or cinder aggregate. Haydite is a light-weight aggregate formed by heating certain clays or shales rapidly in a rotary kiln. While the investigations at the C. F. Burgess Laboratories or at Western Brick Co. were not carried far enough to lead to the commercial production of material for the construction of walls, particularly outside walls, they showed that certain clays could be thermally expanded and that it was possible to produce a material of low permeability with a large percentage of the total voids or cells closed. Commencing in 1939, the Ozark Chemical Co. sponsored a research program at Battelle Memorial Institute for the purpose of determining whether it is technically feasible to make thermally expanded building units, and specifically to get answers to the following questions:

Jan 1, 1942

By R. W. Guard, W. R. Hibbard

As part of a program to determine the deformation characteristics of pure metals, the tensile creep properties of high purity aluminum (99.994 pct Al) have been determined using a constant stress loading. The effects of prior annealing temperature, stress, and temperature were studied. These data have been examined on the basis of present-day theories. None of the methods was found to give an accurate representation of the data over all conditions studied. The structures of several specimens after creep were examined by optical and X-ray metallography. Marked changes in the grain size were found and it was substantiated that the magnitude of these changes was greatly influenced by the applied stress (or creep strain). The changes in fiber texture which occur on creep deformation are shown to be consistent with those observed on deformation at lower temperatures. UNDERSTANDING the properties of new mate-*-J rials under different experimental conditions must be based on considerable knowledge of the mechanisms involved in plastic flow and how to control them. Tension and creep tests have been carried out on a number of pure metals in order to document their deformation characteristics. It is hoped that a comparison of these data with theory will indicate those areas where work on mechanisms and their relation to metallurgical variables may be most fruitful. Since aluminum has often been used for studying the qualitative aspects of creep behavior, it was chosen for detailed study. The effects of annealing temperature, stress, and test temperature on the constant stress creep behavior were studied. Although most of the tests were made above one half the absolute melting temperature, a few tests were made at lower temperatures to give qualitative comparisons. Some specimens were examined metallo-graphically and by X-ray diffraction techniques after creep. Since only a limited number of specimens could be made from the available material, no effort was made to study detailed changes in sub-grain structure or other metallographic features. Servi and Grant3 nd Dushman et al.' have previously published studies of high temperature creep of high purity aluminum. In both cases, a great deal of emphasis was placed on the minimum creep rate.

Jan 1, 1957

By Colin J. Dixon

The full realization of the potential of computers in geological in- formation system demands new approaches to the machine representation of information. At the same time, the feasibility of such a system, particularly in commercial field, demands greater freedom in input preparation and a degree of standardization in the arrangement of subject matter system. The paper describes some of the basic notions of project "GEOSEMANTICA 70". The aim of the project is to devise means of storing real geological informations in a machine rather than the representation of the information in human language form. This is seen as the only long-term solution to the problems of the complex vocabulary of geology and the complex syntax of geological description. Effectively, a machine language is being defined, consisting of a set of symbols and a date structure for representation of geological and related information. Beyond this, is the definition of a set of rules allowing the use of constrained text as an input/output medium. The investigation is oriented primarily to the representation and handling of information about mineral deposits and the associated geographic, economic and engineering information.

Jan 1, 1969

By J. Geertsma

In order to obtain a better insight into the pressure-volume relationship of reservoir rocks a theory of pore and rock bulk volume variations is presented. The theory is independent of the shape of the pores but is restricted to isotropic porous media built up of continuous homogeneous matrix material. The main conclusion obtained from this theory is that only three elastic constants and three viscous constants are required for describing pore and rock bulk volume variations if the porosity is explicitly introduced into the treatment. In addition, reasonable approximations are introduced for various types of reservoir rock, e.g., sandstones, limestones, and shales, which lead to further simplifications of the basic formulas. In consequence there is then a further reduction in the number of deformation constants which have to be determined experimentally. It is shown how measurements of these remaining deformation constants can be performed most conveniently. Finally the application of the theory to reservoir studies is discussed and the translation of experimental results obtained in the laboratory into reservoir behavior is considered. INTRODUCTION The decline of fluid pressure in connection with the withdrawal of fluid from an underground reservoir gives rise to a change in volume of both reservoir fluids and reservoir rock. The volume variation of the reservoir rock results in a decrease of both the pore volume and the total volume of the fluid-filled formation. Whereas the variation in volume of the reservoir fluids with pressure is usually known from PVT analysis, that in the volume of the porous medium is rarely measured, as it is considered of minor importance in reservoir engineering. Nevertheless, certain experimental results' suggest that in a number of cases the neglection of the variation in pore volume may introduce errors into material balance calculations of reservoirs producing above the bubble point. Only a few experimental results on the compressibility of porous rocks have been published. The compressibility of pure quartz and of calcite can be found in a paper by Adams and Williamson'. Botset and Reed' carried out some experiments on the compressibility of loose sands, while Carpenter and Spencer' measured the compressibility of a number of consolidated sandstones, which data were supplemented by Hughes and Cooke5. Hall' finally reported a number of experiments designed to study the influence of the porosity on the compressibility of oil-bearing formations, from which it appeared that, particularly in the low porosity range, the compressibility of the pore volume is important enough to be taken into account. Difficulties, however, arise in applying these experimental results to field cases. This is partly due to the fragmentary nature of the published data. Yet even if more complete data were available, the need for a theoretical background would be strongly felt. Such a background can be partially found in studies carried out by Biot,6,7 who published a theory of elastic deformations of porous materials and their influence on fluid displacement within the pores, by Lubinski8, who studied the stress distribution in an elastic porous medium neglecting pore compressibility, and by Gass-mann" who mathematically analysed the elasticity of packings of spheres. The contributions of Biot intro-duce a number of deformation constants which are impractical for reservoir rocks from an aspect of experi-mental determination. The theory developed by dass-mann is correct but difficult to read. It appeared, how-

Jan 1, 1958

By W. E. Remmers

The defect in wire known as "cuppiness" has appeared and disappeared from time to time but the exact cause of its appearance or disappearance has not heretofore been known definitely. This defect is not limited to one particular metal or alloy but seems to be found at various times in all of the materials that are drawn into wire. Fig. 1 represents cuppy wire made from an aluminum alloy and Fig. 2 illustrates copper wire that became cuppy in drawing without intermediate annealing. Differences of opinion are current among the manufacturers of wire and in the literature (see bibliography at end of paper), some believing that the source of the trouble lies in segregation in the wire rod, oxides, sulfides, slag, etc.; others that the trouble is created by an unevenness of stress distribution across the section of the wire, usually thought of as being a function of die shape. All of the published work is of a qualitative rather than a quantitative nature. With this in mind, it was deemed advisable to make a study of the shape of the wire-drawing dies, as well as the oxygen content of the copper to be drawn. Experimental After several methods were tried, it was found that by studying the contour of the butt-end of the rod after drawing a measure of the "working" across the section of the wire could be made. The butt-end of the annealed rod was not sheared but was sawed off. The end was then smoothed with a fine file so that the plane of filing was perpendicular to the drawing axis. It is to be noted that this method is not an absolute measure of the distribution of cold working but is a very good indicative means of studying comparative values. The method of examining a tension break in wire was found to be the most sensitive in detecting cuppiness. Other methods, such as microscopic examination of longitudinal sections, X-ray radiographic studies, etching away of outer layers with nitric acid, and fracture by bending, can all be used to identify cuppy wire but the tension break will give the fracture characteristic of cuppiness before any of the other methods can

Jan 1, 1930

By F. G. ROCKWELL

ALTHOUGH the diamond as a gem stone dates back many hundreds of years its use industrially, at least to any extend is recent. The old adage: "Use a diamond to cut a diamond" indicates that some industrial use was made of this material in cutting and polishing many years ago. It also put to various other industrial by the Romans. General industrial use however was never developed to any considerable extent until about the time of the first World War. It is definiely known however, that a Swiss watchmaker, M. Leschot by name, invented a diamond drill in or about the year 1862, Today, some 75 or 80 per cent of the total didamods produced are used in industry. There are two main classifications of diamonds : (1) carbonados or "black diamonmds," and (2) diamonds proper.

Jan 1, 1944

By Richard Kunter

INTRODUCTION Additional work has been done on the CIP circuit at Creede, and a brief description of this work is presented in this paper. DREDGE The original dredge for the Bulldog was built by Al Hack, Inc. of Denver. The dredge cutter head is mounted on a boom made of 6-inch diameter pipe which is raised and lowered by a cable-pulley system. Maximum cutting depth is 8 feet. Slurry from the dredge flows through a floating 6-inch diameter pipe supported on 55-gallon drums which runs from the dredge to the shore and then to a trash screen and pumping system. See Figures 1 and 2. The cutter head, suction pump, winches for dredge movement, and all other operations are controlled from a small operations house located toward the rear of the dredge. All of the basic dredge equipment is mounted on a chassis about 8 ft x 16 ft in size. Additional buoyancy was originally provided by sealed 55-gallon drums supported along the sides of the chassis by a small wooden framework. Additional framework and barrels on the front of the chassis on either side of the cutter boom provided additional stability, particularly when digging in hard material. The dredge was quite stable, but two problems were apparent. For one, it could have been sunk by someone from the shore firing a rifle into all of the barrels. In prime deer-hunting and sportsman country

Jan 1, 1983

NEW MEMBERS The following list comprises the names of those persons who became members during the period Nov. 9, 1918, to Dec. 10, 1918. ALBERT, EDWARD J 235 E. Upsal St., Philadelphia, Pa. BARRY, D. A Supt. of. Mines, The Big Five Min. Co., Idaho Springs, Colo. BATON, GEORGE S., Cons. Min. Engr., Baton & Elliott, 2412 First National Bank Bldg., Pittsburgh, Pa. BAXTER, HAROLD ALEXANDER, Met. Engr. & Operation Supt., Tacony Ordnance Corpn., Philadelphia, Pa. BENNETT, JOHN S., Chem. and Min. Engr Copiap6, Chile, South America. BOWDEN, MALCOLM, Min. Engr.; Efficiency Engr., Elm Orlu Min. Co., Butte, Mont. BROWN, HAROLD C 2d Lieut., A. S. A. P. BROWN, THOMAS ALBERT, Min. and Met. Engr.; Supt., The Royal Tiger Mines Co., Breckenridge, Summit Co., Colo. BROWN, WALTER S., Investigator, New Jersey Zinc Co. (of Pa.), Palmerton, Pa. BURDETTE, R.. S Capt., Ord. Dept., U. S. A. CALLANDER, IRA C., Asst. Supt., Gauley Mountain Coal Co., Jodie P. 0., Fayette Co., W. Va. COLLINS, J. W., Foundryman, The Aluminum Casting's Co., "L" Plant, Cleveland, Ohio,

Jan 1, 1919

By Henry M. Howe

The object of the present paper is to suggest injecting into the hearths of iron blast furnaces, whose temperature has become unduly lowered, some form of fuel whose calorific intensity, under the peculiar conditions existing there, is considerably higher than than of liquid petroleum, the rose of this substance for melting out chills having grievonsly disappointed the high hopes which were at first entertained of it. A chill being a fall of the temperature below that needed for the complete liquefaction of the slag, which requires, according to Plattner, about 1800' C., one would suppose that the chief thing to be accomplished in curing it would be to raise the temperature in the crucible of the furnace. The most obvious ways of doing this seem to be to raise the temperature of the blast, and to increase the amount of fuel in the crucible itself. Simply increasing the rate at which the blast enters the furnace, if carried beyond a certain point, should lower the temperature in the crucible. The existence of a chill shows that the fuel is arriving too slowly at the tuyeres. If air be introduced so rapidly as to he in excess of that required for the combustion of the fuel, all that excess will simply lower the temperature around the tuyeres, carrying the region of intense heat upwards, and weakening its intensity by increasing its size. Up to a certain point, increasing the rate of introducing the blast will increase practically pari passu the rate at which the fuel reaches the tuyeres. But when mechanical obstructions, which so often accompany chills, retard the descent of the fuel, there must be a point beyond which this does not hold good, and beyond which farther

Jan 1, 1883

By R. O. Williams

A study utilizing neutron diffraction, electrical resistance, and chemical extraction has been carried out to clarify the chromium-rich part of the miscibility gap previously proposed for this system. This gap appears to be more symmetrical than previously supposed and is very flat. This flatness is believed to be the result of a cooperative phenomenon perhaps of magnetic origin; in particular, it is believed that the chromium-rich phase is antiferromagnetic. The presence of antiferromagnetism is believed to result in an additional strengthening mechanism very sinzilar to that for ordered precipitates. Likewise, it is proposed that the quenched alloys which are known to be ferromagnetic have antiferromagnetic regions which accounts for the maximum in hardness around 75 pct Cr. It is also believed that the existence of antiferromagnetism in other alloys of transition elements might explain some of their anomolous characteristics. THE iron-chromium phase diagram at low temper atures has recently been constructed as shown in Fig. 1(a)1 based upon that work and the work of Fisher, et al2 This system exhibits a number of extraordinary features but perhaps the most striking is the odd shape of the miscibility gap (in the

Jan 1, 1959

By Lester Uren

WITH the depletion of our older, and relatively shallow, oilfields and the necessity for securing new production from deeper horizons, much attention is being given to the improvement of oil-well pumps in order that they may function satisfactorily under the more difficult conditions imposed by increased depth. Until recently, practically all of the world's petroleum was secured from wells less than 3000 ft. deep, whereas horizons are now being explored to depths of from 5000 to 7000 ft. in some of the more prolific fields, and it seems probable that the greater part of the future supply must come from depths in excess of 3000 ft. While much of the early production in a new field is obtained by natural-flow methods, when the stimulus of high gas pressure fails, recourse must be had to some method of pumping. The perfection of a pump capable of economically and efficiently lifting oil from depths ranging from 3000 to 7000 ft. is therefore a matter of prime importance to the oil-producing industry. This paper is offered as an estimate of the present state of development of the oil-well plunger pump and as a review of the general principles involved in its operation in deep-well pumping. A design for a new type of oil-well pump embodying several novel features, is also described.

Jan 9, 1925

By F. H. Kihlstedt

The Larap iron deposits, 125 miles east of Manila, are the biggest high-grade iron deposits in the Philippines, and have in seven years produced nearly 4 million tons of 60 per cent ore. Magnetic surveying followed by churn and diamond drilling cheaply developed a score of million tons. The ore zone is a wedge of metamorphic rocks in fresh, Miocene sediments overlain by agglomerates, which seem to have filled a river valley eroded in the sediments. A mild overthrust of the competent agglomerates crumbled the shale in front. Solutions gradually turned it into more competent hornfels and deposited pyrite, then magnetite and pyrite in the pores. As the temperature rose large bodies of magnetite with some pyrite were deposited by replacement and in open cavities in tensional areas of overthrust shears. At still higher temperature magnetite and calcium-magnesium silicates formed other bodies in similar cavities, and finally the thrust zone was invaded by syenite porphyry, causing high-temperature alteration products. Possibly, as temperature abated, more high-grade ore was deposited. The complicated faulting indicates dynamic, chronological and spatial changes of mineralization rather than zoning in a static system. Noncommercial copper, molybdenum and some gold accompanied the iron mineralization. In the thirties the Philippines gained a justified reputation as a country of considerable mineral wealth. Traces of Chinese workings show that these earliest travelers and traders had in a small way exploited the latent gold resources in the Islands. The Spaniards continued this for centuries, but did not succeed in establishing any steady mining industry. Modern technology was required to get it started. The rapid development in the last decade before the war got its impetus from several financial factors, the return to sugar growers of previously collected taxes, the influx of Spanish capital during the civil war in Spain, the influx of Chinese capital when the Japanese started their "China incident," and others. Directly or indirectly much of this capital reached the mining industry; in particular, gold mining. Out of the turmoil of an exceptional mining boom emerged a sufficient number of good and well managed gold properties to send the production to a level above that of any single state in the United States at the time. Other ore deposits besides those of gold also received their share, and for a country without any heavy industries at

Jan 1, 1949

By F. H. Kihlstedt

The Larap iron deposits, 125 miles east of Manila, are the biggest high-grade iron deposits in the Philippines, and have in seven years produced nearly 4 million tons of 60 per cent ore. Magnetic surveying followed by churn and diamond drilling cheaply developed a score of million tons. The ore zone is a wedge of metamorphic rocks in fresh, Miocene sediments overlain by agglomerates, which seem to have filled a river valley eroded in the sediments. A mild overthrust of the competent agglomerates crumbled the shale in front. Solutions gradually turned it into more competent hornfels and deposited pyrite, then magnetite and pyrite in the pores. As the temperature rose large bodies of magnetite with some pyrite were deposited by replacement and in open cavities in tensional areas of overthrust shears. At still higher temperature magnetite and calcium-magnesium silicates formed other bodies in similar cavities, and finally the thrust zone was invaded by syenite porphyry, causing high-temperature alteration products. Possibly, as temperature abated, more high-grade ore was deposited. The complicated faulting indicates dynamic, chronological and spatial changes of mineralization rather than zoning in a static system. Noncommercial copper, molybdenum and some gold accompanied the iron mineralization. In the thirties the Philippines gained a justified reputation as a country of considerable mineral wealth. Traces of Chinese workings show that these earliest travelers and traders had in a small way exploited the latent gold resources in the Islands. The Spaniards continued this for centuries, but did not succeed in establishing any steady mining industry. Modern technology was required to get it started. The rapid development in the last decade before the war got its impetus from several financial factors, the return to sugar growers of previously collected taxes, the influx of Spanish capital during the civil war in Spain, the influx of Chinese capital when the Japanese started their "China incident," and others. Directly or indirectly much of this capital reached the mining industry; in particular, gold mining. Out of the turmoil of an exceptional mining boom emerged a sufficient number of good and well managed gold properties to send the production to a level above that of any single state in the United States at the time. Other ore deposits besides those of gold also received their share, and for a country without any heavy industries at

Jan 1, 1949

By David Cornell, Yusuf K. Sukkar

The fundamental differential equation for fluid flow has been rearranged, integrated numerically for natural gases, and the results presented in tabular and graphical form suitable for the direct calculation of vertical gas flow problems. The integration is rigorous except for the use of a constant average temperature. Both static and flowing bottom-hole pressures may be calculated by (his method without resort to trial and error procedures. INTRODUCTION Bottom-hole pressures can be determined either by direct measurement with a bottom-hole pressure gauge or by calculation. Since measurement with a bottom-hole pressure gauge is costly, calculation of bottom-hole pressures is to be preferred when possible. Calculation involves knowledge of the wellhead pressure, the properties of the gas, the depth of the well, the flow rate, the temperature of the gas, and the size of the flow line. These quantities must be combined in a suitable equation for vertical flow. Several equations have been developed for the purpose of calculating gas flow through both horizontal and vertical pipes1,2,4,5,6,7,8,9 These equations all have the basic differential equation for flow as their starting point. They differ only in the assumptions which are made in order to simplify the integration step. The bottom-hole pressures calculated using any of the better known equations are in good agreement with bottom-hole pressures calculated by a more rigorous but considerably more tedious stepwise integration method. All of these methods, however. require a trial and error solution for the calculation of flowing bottom-hole pressures. The purpose of this paper is to present a method which provides a direct solution of static and flowing bottom-hole pressures without use of a trial and error solution. At the same time the method involves fewer simplifying assumptions than any of the previous methods used, except lor the lengthy stepwise method. The derivation of any practical flow equation begins with the basic differential equation which is rigorous for almost all flow problems. The five terms in Equation 1 represent the potential energy, the potential energy of position, the kinetic energy, the shaft work done, and the energy losses due to motion of the fluid respectively. Equation 1 reduces to Bernoulli's theorem for the case of horizontal flow of an incompressible fluid, no work done, and no energy losses due to friction. In the present case, the term (v) (dv)/(g,.) can be shown to be quite negligible compared to the other terms, and is therefore neglected in the derivation. The term — dws includes work done by a pump or turbine in the system and is zero in this case. The frictional losses in the pipe are included in the term — d(lw) which is expressed in terms of the Moody friction factor as in Equation 2. (f) (v2) (dL) d(lW) = (f)(V2) (dl)/(2) (g) (d) The specific volume of a gas can be expressed in terms of the temperature, pressure, molecular weight, and compressibility factor. The velocity of the gas can be expressed in terms of the weight rate of flow, the specific volume, and the dimensions of the pipe.The reduced pressure Pr is to be used because z can be expressed as a function of Pr and Tr alone for most natural gases:

Jan 1, 1956

By Paul E. Richardson, Edwin E. Maust

Cyclic voltammetry and surface potential (photovoltage) measurements have been carried out on galena electrodes in sodium tetraborate solutions with added HC1 and NaOH to adjust the pH over the range 2 to 13. The first technique shows that the surface species formed on moderate anodic polarization and reduced on subsequent cathodic polarization are the same over the entire pH range. At anodic potentials, a soluble metal species and excess sulfur are formed; at cathodic potentials, sulfur is reduced to a soluble species. More importantly, excess surface sulfur is formed spontaneously under zero current conditions in alkaline solutions. This has been shown to occur on both polished surfaces and on virgin surfaces produced by in situ cleavage under the electrolyte. The photovoltage gives some insight into the charge and potential distribution at the galena surface. This is found to depend on past electrochemical history and the n- or p-type semiconducting character of the electrode and is interpreted in terms of changes in the surface stoichiometry that occur during reduction or oxidation. The effect of surface stoichiometry on subsequent xanthate interactions is discussed.

Jan 1, 1976

By A. S. Richardson

THE recent installation of a high-pressure propeller type fan at the Moose shaft of the Anaconda Copper Mining Co. at Butte, Mont., is of interest on account of novelty of design and also because an appreciable saving was made over the cost of a reversible centrifugal fan such as is ordinarily used where a high pressure is required. The lower cost is due solely to the fact that by means of controls on the power supplied to the three-phase, alternating-current, induction motor, directly connected to the propeller it is possible to reverse the direction of rotation of the propeller and thus reverse the direction of air flow. The extra air ducts and reversing doors required for this purpose with centrifugal fans are not necessary, and their elimination greatly reduces these construction charges, which form a great part of the total expense. The Badger State mine for which the Moose shaft is used as the main outlet air course is now being developed to the 4100-ft. level. The old centrifugal fan, formerly used at the collar of the shaft, was installed 15 years ago at a time when most of the stoping was being done above the 2400-ft. level, and when the temperature of the rock was much lower than it is now on the bottom levels recently opened. The old fan, therefore, became inadequate to maintain desirable ventilation conditions, on account of the increase in resistance to air flow incident to the greater depth of the mine workings and because a much larger volume of air is required to offset the higher rock temperatures. Propeller, or disk, fans commonly used in the ventilation of mines are not suited to high-pressure work, but economies in the cost of their installation have long been recognized. In South Africa use has been made of a number of propellers placed in series along a common shaft, the number of propellers used being varied with requirements for meeting different conditions of mine resistance, but the mechanical efficiency is described as being low. In Butte, experimental work was done by the writer along similar lines under somewhat different conditions, but with poor results as to both pressure capacity and mechanical efficiency. Tests were also made of two different types of propeller fans of moderate size, which were said by the manufacturers to be suited to high-pressure mine ventilation.

Jan 1, 1932