Search Documents

By A. C. Heath, E. H. Dix

The importance of aluminum-silicon alloys in thc light alloy field is now generally recognized. Where silicon was once considered detrimental to the properties of aluminum, useful alloys now contain as much as 13 per cent. Furthermore, silicon is present as an impurity in aluminum of even the purest grades. Iron is another important impurity in aluminum and likc silicon is found in small quantities in the purest aluminum available today. The manner of occurrence of iron and silicon in commercially pure aluminum and many of its alloys exerts a very pronounced influence upon their properties. The effect of large quantities of iron in aluminum-silicon alloys is so detrimental that it has been found necessary to limit the allowable maximum percentage to as low a figure as is consistent with quantity production and satisfactory physical properties. The intimate relation existing between iron and silicon in aluminurn and alurninum alloys makes necessary a more complete knowledge of this ternary system. This paper is divided into two principal parts, dealing respectively with aluminum-silicon solubility equilibria and the constitution of aluminum-iron-silicon alloys. Part I.—Aluminum-silicon Alloys The early work on this system was largely confined to determining the general form of thc diagram and in this respect the results are in good agreement. Briefly, alulninunl and silicon form a simple eutectifcrous series without compounds. Until recently the solid solubility of silicon in aluminum had not been accurately determined. Ipraenkell (1908) stated that aluminum will retain 0.5 per cent. silicon in solid solu-t'ion. Rosenhain, Archbutt and Hanson2 gave the maximum solubility as about 1.50 per cent. and added that "this solubility docs not appear

By John F. Walker

WITH an estimated production of over 936,000,000 for the first six months, the gross value of mine production for 1937 in British Columbia should exceed $70,- 000,000. This figure, if attained, will establish an all-time record for the Province. Great changes have taken place in the different divisions of the mining industry since 1929, the previous peak year of mineral production. A brief review of the earlier history of mining in the Province will also be given.

Jan 1, 1937

By M. G. Corson

UNTIL recently, the characteristics of cast copper have seldom been studied and such study as has been made has been inadequate. The prevailing idea seems to be that since pure copper is infrequently used in the cast state, there is no reason for trying to establish precise data regarding the properties of the metal in that condition. On the other hand, wrought copper either in the shape of sheets or wire rarely fails in service, except as a result of the action of reducing gases at the annealing temperatures, so there is little incentive to study the properties of the cast shapes -cakes, bars, ingots and billets-for the sake of tracing the causes of failures of the wrought metal to the cast stock. However, about a decade ago, wirebars of American origin often cracked badly while being hot-rolled in mills in Germany. This led to four investigations: by E. Seidl and E. Schiebold,1 by P. Siebe,2 by 0. Bauer and G. Sachs,3 and by G. Welter.4 These authors came to the conclusion that failures in hot-rolling were due essentially to the presence of a' wide zone of columnar crystals between the thin layer of fine crystals near the surfaces of the bars and the large but more nearly: equiaxed grains of the central core. This macrostructural defect was explained in turn by the probable upward deviation in the temperature of the metal while it was being poured into the molds of the casting machine. More recently, cast shapes of copper were investigated by N. P. Allen5 and by C. Blazey.6 Allen examined vertically cast wirebars and horizontally cast wedge cakes of electrolytic tough-pitch copper, but only for the distribution of densities; i.e., porosity. Blazey was interested mainly in the mechanism of the variations in electrical conductivity due to cold-work and anneal, but gave introductively an account of the composition and average densities of the tough-pitch horizontally cast wirebars used. As far as the present writer can tell, no investigation was undertaken for the sake of presenting a picture of the distribution of mechanical characteristics in the wirebars of copper, tough-pitch or otherwise.

Jan 1, 1938

By Cyril Smith

SEVERAL investigators, mainly concerned with the mechanical proper-ties of the alloys, have studied the so-called aluminum bronzes after various quenching and reheating treatments. Of these works, perhaps the most complete is that of Bouldoires,1 who studied changes of length, electrical conductivity, thermoelectric force, hardness and micro-structure oh tempering quenched alloys containing 5 to 20 per cent of aluminum, although the work of Carpenter and Edwards,2 Curry,3 Greenwood,4 Braesco,5 Matsuda;6,7 Grard8 and others has added much to our knowledge of the changes occurring during tempering. The so-called acicular ß decomposes on tempering at temperatures between 350° C. and the eutectoid, giving rise to a Widmanstätten structure of a needles in a matrix of d or fine a + d, associated with an increase in hardness and almost complete loss of ductility. Matsuda, studied the' eutectoid transformation by means of dilatation and electrical "conductivity measurements during cooling at different rates. He found that on cooling at the rate of 10° C. per minute there was a decrease in electrical resistance and in length instead of the usual increase which occurred with slow rates of cooling. On tempering the rapidly cooled samples, the increase commenced at about 400° C. and at 520° C. the resistance and length had reached the equilibrium values. These peculiarities he accounted for as being due to a transitional phase ß' being formed, ß having an electrical resistance and volume less than either ß or a + d.

Jan 1, 1933

By A. W. Ashbrook

There are essentially three main classifications for extractants: acidic, basic, and neutral. The acidic and basic are also referred to as cationic and anionic, respectively. Some extractants are shown in Table 11-1. Acidic Extractants Acidic extractants which are of use, because of cost and/or insolubility in water, are alkylphosphoric, sulphonic, aliphatic monocarboxylic acids and naphthalene derivatives.

Jan 1, 1978

By J. A. Herbst, K. Rajamani, Y. C. Lo

In spite of potential theoretical and economic advantages of large-diameter ball mills, many manufacturers elect not to build them owing to what is perceived as an excessively large design risk. This is because traditional predictions for mill scaleup to large diameters are not always accurate. Alternative methods of analysis and scale-up are required. Recent studies have shown that detailed population balance models which account for important grinding subprocesses (grinding kinetics, material transport, and classification) are capable of predicting the performance of small- and intermediate-diameter mills (up to 4.3 m, or 14 ft) from small-scale batch tests. These same models are used in the current study to predict the performance of a "borderline "large ball mill (4.7 x 5.5 m, or 15 x 18 ft) at Asarco's Sacaton operation, a ball mill (5 x 5.8 m, or 16.4 x 19 ft) at Kennecott's Chino operation, and one of the world's largest ball mills (5.5 x 6.4 m, or 18 x 21 ft) at Cities Service Pinto Valley operation. Model parameters required for scale-up have been estimated in a 380-mm-diam (15-in.-diam) batch mill. Predictions are compared with the results of detailed plant sampling in the three plants. For the Sacaton and Chino operations, the error of the predictions was found to be less than 2.5%, while the corresponding error for the Pinto Valley operation was less than 2.7%. It is concluded that proper representation of the major subprocesses of grinding in the model equations is the key to achieving accurate scale-up. Of special importance is the need to account for the size distribution of the grinding media and the influence of the size distribution environment in the mill on grinding kinetics.

Jan 1, 1986

By J. E. Hanlon, J. D. Wolf

The relaxation peaks observed in plastically deformed materials at low temperatures have been reviewed by sack1 and Niblett and wilks. 2 In particular, the dislocation-relaxation in columbium has received considerable study.3-6 The present work deals with the lower-temperature dislocation-relaxation peak (referred to by Chambers and Schultz as the a peak) in columbium and Cb-5 pct Zr. The columbium and Cb-5 pct Zr specimens were machined to 3/8-in.-diam by 7-in.-long rods from bars hot-extruded at 1200°C. The internal friction and resonant frequency of the samples were measured in torsion at kilocycle frequencies at a maximum strain amplitude of -10-6. The interstitial content of both materials was approximately 70 ppm N and 200 ppm 0. The dislocation-re laxation peaks were measured in the hot-extruded state and after successive anneals. Fig. 1 is a compilation of the data. The resonant frequencies for the columbium and Cb-5 pct Zr samples were, respectively, 5.5 and 6.5 kc. Other workers have noted that the dislocation-relaxation peaks in columbium are not characteristic of a single relaxation time. As can be seen in Fig. 1, the zirconium addition further broadens the spectrum of relaxation times. The magnitude of the modulus defect as computed from resonant-frequency data also reflects this extension. The occurrence of the low-temperature a peak at a position 20°K higher in Cb-5 pct Zr as compared to pure columbium, in the hot-swaged state, suggests a decrease in the average dislocation mobility for the alloy. The authors do not feel that these data are sufficient to permit an interpretation in terms of any detailed models.

Jan 1, 1967

By Charles L. Thomas

A novel, highly sensitive, and reproducible nzetlzod for the determination of hydrogen in solid materials is presented. The procedure requires equilibration of the specimen with hydrogen gas, rapid quenching, and hot vacuum extraction of the dissolved gas with subse-quent quantitative analysis by mass spectroscopy. Good linearity is obtained for the Arrl~enius plots of the investigated metals. The advantages in the use of this method over that of Sieverts aye discussed. The solubility data for copper are in reasonable agveewzent with a considerable number of other inuestigations, wllile those fov silver are considerably lower than previously reported. The first known solubility data for gold are presented. Solubility equations and heats of MUCH of the data which are available on the solubility of hydrogen in various metals and alloys have been obtained by the classical Sieverts method.' The method involves the measurement of a decrease in pressure of a gas in a calibrated system, and the calculated contraction in volume is attributed to the solubility of the gas in the metal sample. The procedure requires several corrections, such as the solubility of the gas in the container walls and the diffusion of the gas through these walls, as noted by Steacie and .Johnson2 and others. In addition, errors may be incurred due to reactions between metal surface impurities, such as oxides, and the saturating gas. The precise calibration of the measuring system where large thermal gradients exist can present additional difficulties. Also, accurate volumetric measurements of small quantities of gas are difficult. Many of the objections to the Sieverts method were overcome on solid materials by Ransley and ~eufeld,~ who first saturated the metal with hydrogen and performed a subsequent extraction and measurement of the gas by chemical means. Eichenauer and pebler4 and Eichenauer, Kiinzig, and pebler5 measured the diffusion coefficient and solubility by following the degasification of a sample as a function of a rate of increase in pressure in a previously evacuated system. Here again, however, the procedure involves many of the corrections of the Sie-verts method. The present investigation deals with the solubility of hydrogen in solid copper, silver, and gold by a technique which eliminates many of the aforementioned corrections and possible errors. This procedure requires equilibration of the specimen with gas, rapid quenching, and hot vacuum extraction of the dissolved gas with subsequent quantitative analysis by mass spectroscopy. EXPERIMENTAL Two completely separate systems were employed to accomplish first, the equilibrium saturation of the sample and second, the extraction of the dissolved gas. Saturation Apparatus. The saturation apparatus, illustrated in Fig. l, consisted of a vertically mounted quartz tube with a three-way valve for vacuum or hydrogen near the top and an outlet near the bottom leading to a butyl phthalate seal. The bottom end of the tube was terminated with a joint accommodating an O-ring sealed "Asco Stirring Gland" (The Emil Greiner Co.). This gland facilitated movement of the thermocouple without introduction of air into the system. The upper portion of the tube (above the furnace) was water-jacketed. A Welsh 1405-B mechanical pump provided the necessary system evacu-

Jan 1, 1968

By R. I. Jaffee, F. C. Holden, H. R. Ogden

Ti-Mn alloys were studied in order to determine the factors affecting the mechanical properties of &stabilized titanium alloys. The principal compositional factors have been found to be solid-solution strengthening, the martensitic transformation, and instability of the P phase. Structural factors, such as grain size and shape, were found to have more influence on ductility and toughness than on strength. THE alloys of titanium with the &stabilizing elements offer the chief hope for developing useful heat treatments. Conversely, the heat-treatment response possible with the p-stabilizing elements causes difficulties such as weld embrittlement and thermal instability during service at elevated temperature. Therefore, it is of considerable technical importance to understand the factors that govern the heat-treatment responses in these alloys, so as to be able to soften the alloys if they are embrittled by an adventitious heat treatment, to render them stable in service, or to harden them while maintaining adequate ductility and toughness. The Ti-Mn system is a good example with which to demonstrate the factors that govern strength and heat-treatment response in. a P-stabilized system. The region of the a-j3 transformation, after the work of Maykuth, Ogden, and Jaffee,' is shown in Fig. 1. The a solubilities are low. This means that, in the two-phase a-p field, partition of manganese between the two phases occurs practically only to the P phase. The solid-solution effects are therefore chiefly the result of solution in the ,8 phase. The eutectoid occurs at 20 pct Mn and 550°C, and proceeds very sluggishly. It can be ignored in heat treatments in hypo-eutectoid alloys, except for long-time storage at low temperatures below the eutectoid temperature. Even here, there is some question that diffusion proceeds far enough to involve eutectoid decomposition. Three compositional factors bear on the mechanical properties and structure of titanium a-P alloys. These are: 1—solid-solution strengthening, 2—mar-tensite transformation, and 3—P instability. Combined with the purely structural factors of grain size and shape, these govern the properties of the alloys. Perhaps the most important factor is solid-solution strengthening. The facts that manganese dissolves in a titanium to a maximum of only 0.5 pct and most of the manganese partitions to the p phase dominate the structure and properties of the a-/3 alloys. Because of the overwhelming preference of manganese for the ,3 phase, the P phase is harder and the a phase is softer. The relative amounts of both phases may be modified by heat treatment in the a-P field as application of the lever rule in the two-phase field clearly shows. A critical temperature in the Ti-Mn diagram is 800°C. This is the P transus temperature of the 6.4 pct Mn alloy, which has the lowest manganese content which will form all retained-P phase on quenching to room temperature. Any quench performed from below 800°C will produce a structure consisting of only a, a plus retained P, or retained p, for alloys of the compositions used in this work. For alloys containing less than 6.4 pct Mn, any quench from above 800°C will always result in structures

Jan 1, 1955

By F. Clerf

BLAST-FURNACE practice in France is determined more or less by the character of the ores used. Some French ores are siliceous and others are calcareous, therefore by proper burdening a self-fluxing mix can be used. This is not always clone, as, for instance, at the Caen furnaces of the Société Métallurgique de Normandie, where the Soumont ore of Normandy is used, which is a carbonate. This ore is crushed and calcined at the mines, yielding a product that is porous and well sized for blast-furnace consumption. The lines of the Caen furnaces are given in Fig. 1. Originally these furnaces had 16 tuyeres; six are plucked and these tuyeres are set in the lower part of the bosh. Operating data on these furnaces are given in Table 1.

Jan 1, 1937

By C. S. Matthews, M. Prats, R. I. Jewett, J. D. Baker

By mathematical analysis it was found that injectivity history of a uniform five-spot pattern can be calculated by rather simple formulas. These calculated injectivities were found to agree rather well with injec-tivities measured in a potentiometric analog. With this as a basis, a simple method was finally developed which allows prediction not only of rate of injection but also of rate and kind of production at the production well, for a uniform five-spot. Using this method formulas for the eflective injectivity and production behavior of a waterflooded reservoir having a wide range in permeability can be calculated by considering that the reservoir consists of several layers, each having a uniform but different permeability. Rather good agreement is shown by a comparison of the observed production history of a field in the Illinois basin and that calculated by the methods just described. INTRODUCTION The importance of being able to predict the injection rates for a water flood is well known, for upon injection rate depends the life of the flood, the size of pumping and treating facilities, and the rate of oil recovery. One method of determining rates of injection is through a pilot flood. However, it appears that even if a pilot flood is resorted to, a theoretical method for calculating injection rate will be valuable in extending field results to times after inter- ference and to locations of other five-spots. It is also important to be able to predict the production history of a flood. Such prediction must generally be done by theoretical means, since in general a small pilot flood will not furnish much quantitative information in this regard because of the distortion after oil-bank interference. Methods for predicting the behavior of five-spot water floods have been proposed by Yuster and Cal-houn' and by Hurst.? However, these methods do not consider the effect of the mobility of the different fluids in the reservoir. Other investigators3,4,5,6 have determined the effect of the water-to-oil mobility ratio on the production history by means of different experimental techniques. Most of the published work applies to homogeneous sand bodies, does not provide information for determining the injection requirements of a flood, and seldom considers the rate of build-up of the oil bank as it fills up the partially depleted reservoir.* The present work was undertaken because of the lack of predictive method which takes into account mobility ratio and the rate of buildup of oil bank resulting from the void space in a partially depleted reservoir. As water is injected into the reservoir, which contains oil, water, and gas in macroscopically homogeneous saturation, it forms several banks ahead of the injection well. In each bank or region there is assumed to be only one mobile phase—water in the water bank, oil in the oil bank and gas in the gas region. The saturation in each region and a plan view of the banks are shown in Figs. 1 and 4, respectively. FACTORS AFFECTING INJECTION AND PRODUCTION RATES Results in this report are determined as functions of the three parameters, F, M, and M, , and of a fourth parameter, r,/L** which relates the size of the well to the flood spacing. The parameter F is the displacement factor defined by Hurst in Ref. 2. It determines the rate of build-up of oil bank as it fills up the partially depleted reservoir. When gravity effects are neglected, the four parameters just given are sufficient to describe the waterflood behavior for horizontal and homogeneous reservoirs having incompressible liquids. Definition of InjectIvity The dinlensionless injectivity (or injection rate) used in this report is defined by

By William Fink

NICKEL is used as an alloying element in several complex commercial aluminum alloys, among which are found some very interesting proper-ties, such as relatively high strength at elevated temperatures, relatively low coefficient of expansion, the absence of permanent growth, ability to take a good polish, and a bright, pleasing as-cast surface. For that reason the aluminum-nickel system was included in the list of binary aluminum systems that are being studied as a preparation for the investigation of more complex commercial alloys. This paper is the fifteenth of a series from the Research Laboratories of the Aluminum Company of America reporting the results of investiga-tions of equilibrium relations in aluminum-base alloys of high purity. The aluminum-nickel equilibrium diagram from 0 to 18 per cent nickel was determined, using the purest material available.

Jan 1, 1934

By G. Sachs, E. J. Ripling, J. J. Lynch

It is general practice to evaluate the strength properties of a particular metal from its stress-strain (s1 — el) curve obtained by means of a conventional tension test. Such a stress-strain curve, Fig I, illustrates two important properties of a metal, its ability to strain harden, and its ability to withstand a certain limiting stress, the "fracture stress," (s), and a certain limiting strain, the "ductility" (es), before it fails by separation. These two fracturing characteristics are the coordinates of the point of fracture in Fig I. In the case of a metal which necks in a tension test, both the fracture stress and the ductility (measured in a tension test) are dependent upon (I) the shape of the neck and (2) average values of the stresses and strains over the cross-section at the moment of fracture. However, for the pur. pose of this investigation, these average quantities, rather than the actual values, may be considered for reasons of simplicity. It appears that the conclusiom also hold true if the analysis were carried out for actual values of fracture stress and ductility at the locos of failure. In this paper, the effects of straining (at room temperature) by various methods on the above metal characteristics, which were determined by subsequent tension tests will be discussed. According to Our present knowledge, any such prestrainitlg results in a stress-strain curve (in subsequent testing by tension), Fig 2, the general shape, or flow characteristics, of which can be derived from the original stress-strain curve of the unstrained metal minus a certain portion exhausted by the initial straining. This phenomenon is called strain hardening, and may be measured by the magnitude of the cut-off, or the "effective strain,'' from which the new curve must start in order to coincide in its plastic branch with the original stress-strain curve.

Jan 1, 1949

By Robert Glass Cleland

FROM the time of its organization down to 1917, a period of more than eighty years, Phelps, Dodge & Co. was seldom involved in what could be called a major labor difficulty. Behind this remarkable record lay both a philosophy and its practical application. The philosophy was an attitude toward society called the Golden Rule. That philosophy had been a living principle in the lives of the founders of the company, Anson Phelps, Daniel James, and William E. Dodge. Their successors, William E. Dodge, Jr., and Daniel Willis James, accepted the same philosophy. Dr. James Douglas governed his life by it. All of these men and their families had given tangible expression to that conviction in benefactions of great magnitude and variety-churches, hospitals, educational institutions, libraries, missionary undertakings, and other organizations for human betterment, such as the Young Men's and Young Women's Christian Associations, and the development of model communities about their mills and factories. According to the best standards of their generation, they had sought to improve the condition of labor,

Jan 1, 1952

By B. K. Larkin, H. R. Bailey

A model Of heat flow in an underground combustion process is studied. This model includes convection effects and thus is more general than previous studies which considered conduction as the only mechanistn for heat transfer. Both linear (tube run) and radial (field application) geometries are considered. The effects of ignition heaters, vertical losses and finite source width are considered for the linear case. The results are in the form of equations and are presented in graphical form for a number of cases. Convection effects increase frontal temperatures about 25 per cent over those computed for conductive transfer for typical field operating conditions. This increase in temperature is a result of heat being transported toward the front by the injection gas. Even greater temperature increases are realized as the per cent oxygen in the injection gas decreases. It is well known that compression costs are of considerable importance in estimating the economic feasibility of underground combustion. By assuming an ignition temperature for the combustion fuel, predictions of limiting conditions on fuel density and injection rate necessary to sustain the combustion zone are made. For typical field conditions, at least 0.75 lb/cu ft of fuel are needed with air as the injection gas. If the injection gas is 10 per cent oxygen and 90 per cent nitrogen, this figure is 0.69 lb/cu ft. INTRODUCTION The possibility of increasing oil recovery by underground combustion has been considered for many years. Recent field tests indicate that the underground combustion process is technically feasible. The economic feasibility depends to a large extent on the amount of air which must be injected to sustain combustion. Prediction of the success of employing underground combustion in a particular reservoir must be based on existing field tests, laboratory tube runs"' and solutions of mathematical or analog models. Vogel and Krueger5 devised an electrical analog of the heat transfer problem in an underground combus-ion process. They considered the problem of heat conduction from a cylindrical source with increasing radius assuming no vertical losses. Bailey and Larkin and Ramey solved the corresponding problem including vertical losses by considering a mathematical model of the conduction process. Ref. 9, 10 and 11 also present information related to the subject study. The present paper generalizes these results to include both conduction and convection mechanisms for heat flow. A model of the conduction-convection process is described. The partial differential equations governing this model are written and solved for a number of cases of interest. The formulas are evaluated and the results are presented graphically. A CONDUCTION-CONVECTION MODEL Description of the Model A number of models are employed in this paper, each of which approximate a particular physical situation depending on the geometry, i.e., linear or radial flow, the type of vertical heat losses, the nature of the source, etc. The geometry for both the linear and radial case is shown in Fig. 1. A particular linear model is described in this section, and variations from this model are described in later sections of the paper. Consider a homogeneous, semi-infinite porous prism with lateral sides insulated as shown in Fig. 1. The left end, x = 0, is heated for a time t, with a plane heater supplying a constant heat flux and during this time; gas (nitrogen) is passed through the pores of the prism at a constant mass flux. At time t, the heater is turned off and air is injected in place of the nitrogen. This causes combustion to take place, and a uniform source of width 1 is formed which moves at a constant velocity v, to the right. The frontal velocity v, is related to the gas velocity v,, through stoichiometric considerations

By J. L. Rodda

THE desirability of a uniformly sized abrasive for metallographic polishing has probably been recognized in a general way for a long time. Certainly all metallographers have recognized the damage that can be done to a polished surface by a piece of grit, especially if one of the softer metals, such as zinc or aluminum, is being polished. It is to be doubted, however, whether many metallographers have had any adequate idea of the particle size of the abrasives they were using or of the range of sizes encountered in any given grade of abrasive. At any rate, the descriptions of abrasives for metallographic work found in the literature are generally very meager. It was with the idea of securing an abrasive with a limited range of particle size that a study of this problem was commenced. Commercial abrasives, even when recommended for metallographic work, are made up of particles of varying sizes. One such abrasive contains some particles so fine that they remain in suspension for days and other particles so coarse that they settle at the rate of 3 in. per minute. It is evident that the coarsest particles are over 100 times the diameter of the smallest ones, or over 1,000,000 times the volume. The hopelessness of avoiding scratches under these conditions is evident. Vanderwilt1 has described a laboratory method for grading abrasives in which the elutriator is used. Le Chatelier's method, described by Goerens,2 also makes use of an elutriator. However, the elutriator is too slow for this purpose and requires too delicate a control for the range of sizes desired. The method of stirring up the abrasive in water, allowing it to settle for as given time, then drawing a measured depth off the top of the suspension, has been finally adopted as the simplest proce-dure. The largest particle in a given portion is. then determined by Stokes' law:3

Jan 1, 1931

By W. A. Nagel, R. P. Alger, H. Sherman, J. Tittmann

A sidewall epithermal neutron tool has been developed to substantially reduce environmental effects that have previously complicated neutron log interpretation. Designed for operation in uncased wells, the device provides increased accuracy in both liquid-filled and empty holes. A brief discussion of neutron moderation, diffusion and capture shows that logs using epithermal neutron detection depend on a smaller number of formation-characterizing parameters than those using thermal neutron or capture gamma ray detection. Thus, they come closer to providing an unambiguorls determination of hydrogen content. In this new device a directionally sensitive epithertnal neutron detection system has been incorporated in a side-wall source-detector skid to minimize borehole effects. The effects of variations in borehole size and shape, mud type, temperature and salinity are greatly reduced. Small residual borehole effects are then computationally accounted for in the surface control panel to provide a borehole-corrected neutron log. The log presents a direct recording of neutron-derived porosity on a linear scale. With corrections for borehole effects already applied, this direct recording of porosity simplifies log interpretation. Furthermore, comparison with a linear porosity presentation of a formation density log permits sandstones, limestones and dolomites to be readily identified. Thus, in complex or variable lithology, porosity is determined with greater accuracy and reliability than heretofore. Laboratory data and field results demonstrate the improvements in neutron logging afforded by this new side-wall epithermal neutron logging device. INTRODUCTION The new Sidewall Neutron Porosity (SNP) logging system, designed for use in uncased wells, provides reliability and accuracy never before achieved with neutron logs. The effects of variations in borehole diameter and shape, fluid salinity, mud weight and temperature—parameters that have long complicated neutron log interpretation— are suppressed or corrected for by this sidewall epithermal neutron detection system. Furthermore, to simplify interpretation the SNP log presents a direct recording of computed porosity on a linear scale. The performance improvements achieved by this new system arise primarily from the combination of two im- portant design features. First. though not unique to this new tool, an epithermal neutron detection system is used,',' Epithermal neutron detection substantially reduces the perturbing influences of the thermal neutron absorption properties of rock matrices and water salinity. Second, the neutron detection system is mounted in a directionally sensitive sidewall skid to greatly minimize borehole effects. The purpose of this paper is to explain briefy the advantages offered by the detection of epithermal neutrons, to describe the SNP equipment and the log, to present calibration and correction data and to give examples of interpretation methods made especially convenient by this new system. ADVANTAGES OF EPITHERMAL NEUTRON DETECTION Epithermal neutron detection, of all the neutron methods in current commercial use, provides the simplest determination of formation hydrogen content. Advantages of epithermal neutron detectors, as compared with thermal neutron and gamma ray detectors, are probably best explained by a brief review of the life of a source-emitted neutron. A fast neutron from the source will eventually be cap-tured by the nucleus of an atom. However. before capture is likely to occur, the fast neutron (energy of 100,000 electron volts (ev) or more) will be slowed down until it is in thermal equilibrium with its surroundings. The neutron is then considered to be a "thermal" neutron (average energy of 0.025 ev at 25C). The overwhelming majority of the slowing down thus occurs in reaching epithermal energies (energies just above thermal—0.5 to several ev). After reaching thermal energy. the neutron will "diffuse" through the formation with, on the average, no further energy change until capture. Upon the capture of the thermal neutron, relatively high energy gamma rays arc usually emitted. Hydrogen plays a very important role in the process of slowing down fast neutrons. On the other hand, the absorption effects of water salinity and low concentrations of other strong thermal neutron absorbers—relatively unimportant in the moderation process-—are very important in thermal diffusion, capture and the production of gamma rays. Thus, by detecting only epithermal neutrons with the SNP, spurious effects due to these thermal neutron absorbers are greatly minimized as compared to the effects on tools using thermal neutron or gamma ray detectors. The epithermal neutron detection system affords another important advantage. Log response in various litho-

Jan 1, 1967

Jan 1, 1918

By D. H. Davis

HAND picking was the earliest form of coal preparation, first practiced to improve the outward appearance of the coal being loaded and to remove any pieces that might appear objection- able to the buyer. It is still extensively practiced on the plus 1-in. sizes and particularly on the plus 4-in. and larger sizes. The percentage of ash reduction that can be obtained by hand picking depends entirely upon the amount of free impurity occurring in the coal. In a particularly dirty seam, where a considerable quantity of rock occurs with the coal as mined, hand picking produces sizable reductions in ash. If the coal is prepared clean at the working face hand picking is a final check; in some cases, on the smaller sizes, it is practiced only to show that an effort is being made to prepare a clean product. Because of the variety and different methods of handling coal, the early plants were not always adapted for efficient hand picking. At most mines an attempt is made to remove the visual impurities at one or more of the following places in the surface plant? (1) in the tipple during screening; (a) on picking band, belt, or shaking conveyors;*(3) during the loading of the coal as it goes into the railroad car. Whatever the physical arrangements of the plant may be, the usual practice is to run the coal over the screen, picking table or boom at such a rate that each piece of impurity is exposed to the view of the picker. Coal should be uniformly sized and spread out on the table so as not to exceed one particle in depth. The flow should be even in tonnage and the speed of travel should be from 30 to 60 ft. per minute and not exceed 80 ft. per minute. The dirtier the coal, the slower the speed required for a fixed number of pickers. Actually, picking capacity depends on the number of particles per minute that can be picked out and rejected. The percentage of impurity removed is determined by this and the average weight of piece rejected. Handling a mixture of sizes from nut to the largest lump over the same picking table or conveyor is not conducive to efficient separation by hand picking because the lump hides the smaller

Jan 1, 1943

By Albert Sir Kitson

THE manganese ore deposits of the Gold Coast, British West Africa, occur in very ancient rocks, of both sedimentary and metamorphic types. In. certain respects, they strongly resemble those of India and Brazil, as contrasted with those of Tertiary age in Georgia. Viewed from the present condition of the maganiferous rocks, the oldest deposits are in the sediments. Later than these are the progressively metamorphosed representatives of these sediments; youngest are the products of decay and degradation with the concentration of manganese oxide of both areas. The oldest occurrences are in argillaceous and siliceous phyllites and slates, which show only a moderate amount of metamorphism. They belong to a series which also includes mudstones, sandstones, grits, conglomerates and subordinate limestones, with tuffs and lava-flow's largely of basic types. To this series I have given the name Birrim. Its age is unknown, for no definite fossils have been discovered in it. As the characteristics of these non-fossiliferous strata at many places are the same as those of strata in many parts of the world that are suitable for the preservation of fossils and that contain them, it is assumed that the Gold Coast deposits are pre-Cambrian. These rocks of the Birrim series have normally a northeast-southwest strike and are folded, but not to any very great degree except in certain belts. From the Eastern Province of the Gold Coast they may be traversed across their strike for more than 600 miles to the extreme northwestern corner of the Northern Territories. Thence they probably extend much further into French Territory.

Jan 1, 1927