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By J. C. Todd

The volume of air needed to move the combustion wave through each acre-foot of the reservoir is a very important quantity for engineering economic analyses. A new method, which involves backflowing the injection well, has been developed for determining the air requirement .for the forward combustion thermal pilot in the Delaware-Childers field. The method depends on measurement of the total volume of air injected and measurement of the pore volume in the zone swept out by the combustion front. The basic premise of the method is that the pore volume of the swept zone contains air, while the formation around this zone contains flue gas, oil and water. The pore volume of the swept zone is determined by blowing down the pilot section of the formation through the injection well after the pilot is shut down. Oxygen balance is used to differentiate between air from the swept zone and flue gas from the surrounding formation. Data indicate that air'is produced from the swept zone by relatively efficient miscible displacement by the flue gas. The pore volume occupied by the air in the swept zone is determined by simple PVT relationships. The average temperature of the swept zone is calculated by heat balance from the total amount of heat generated during the pilot and losses to the surrounding formation. The new method was applied successfully at the conclusion of the pilot in the Delaware-Childers field; the air required for the reservoir conditions involved was calculated to be 19.2 MMscf/acre-ft of reservoir swept. INTRODUCTION One of the most important pieces of information to be found from a forward combustion pilot is the air requirement; that is, the volume of air needed to move the combustion wave through each acre-foot of the reservoir. Compression costs per barrel of oil recovered, which are a direct function of the air requirement, are a large portion of the expenses incurred in the thermal recovery process. Thus, the profitability of thermal recovery depends largely on the air requirement, which is a measure of the amount of fuel deposited and burned in the thermal recovery process. Several attempts have been made to correlate crude oil properties with fuel deposition and, hence, air requirement.l*2 Other attempts have been made by our laboratory to find the air requirement by material balance, gravity survey, pressure transient analysis,3 magnetic survey and the poten-tiometric model. Better methods are needed to predict more accurately the economics of fieldwide application of the process. Another method of finding the air requirement consists of operating a pilot thermal project for several years. This is followed by an extensive coring program to define the volume swept by the combustion wave. The air requirement is found from the total injected air divided by the volume of the swept region found from the coring operation. This method is costly; an adequate coring program usually costs several hundred thousand dollars. A thermal pilot was operated in a watered-out portion of the Delaware-Childers field, Bartlesville sand, from Nov., 1960, until May 3, 1965. One of the primary purposes of this pilot operation was to determine the air requirement for economic calculations which determine the advisability of expanding the project to the entire 128,000 acre-ft field. Barnes4 has described the result of this pilot operation,, including calculation of the air requirement from limited coring data. The value obtained, as calculated, was 15.8 MMscf/acre-ft. One purpose of this report is to describe a new method of finding the air requirement from a thermal pilot operation. A second purpose is to describe the application of this method to the Delaware-Childers thermal pilot. THEORY AND DESCRIPTION OF THE METHOD The combustion zone in the forward combustion process is propagated from injection w producing

Jan 1, 1970

By P. L. De Bruyn, R. J. Charles

THE transfer of kinetic energy of translation into other forms of energy by impact is a fundamental process in most crushing and grinding operations. During and after the impact process the original source energy may be accounted for in any of the following possible forms: 1) Kinetic energy of translation of both the impacted and impacting objects. 2) Kinetic energy of vibration of the components of the impact system. 3) Potential energy as strain energy of the components of the system or in the form of residual stresses. 4) Heat generated by internal friction during plastic deformation or during damping of elastic waves. 5) New surface energy of fractured materials. At any instant during the impact process only the strain energy of the components of the system can contribute directly to the brittle fracture process. If fracture is the desired result, as in comminution, it would seem advantageous to choose or arrange the conditions of impact so that a maximum amount of the original kinetic energy could be converted to strain energy at some moment during a single impact. The present work deals with determination of these desirable conditions for a simple case of impact and application of the principles involved to general cases of impact. Experimental Method: Longitudinal impact of a rod with a fixed end was chosen as the impact system for investigation. The rod was mounted horizontally and the fixed end was formed by butting one end of the rod against a rigidly mounted steel anvil. The rod, of pyrex glass, was 10 in. long by 1 in. diam with both ends rounded to a 6 in. radius. The rounded ends permitted reproducible impacts on the free end of the rod and assured a symmetrical fixed end. Pyrex was selected as the rod material because of the marked elastic properties of such glass and the similarity of fracture between pyrex and many materials encountered in crushing and grinding operations. The frequency of natural longitudinal oscillation of the rod was 10 kc, and thus simple electronic equipment could be used for observation of strain changes occurring in the rod at this frequency. As shown in Fig. 1, impacts on the free end of the rod were obtained either by a pendulum device or by a spring-loaded gun. Relatively heavy hammers (100 to 600 g) of mild steel were used in the pendu- lum impacts, while fairly light projectiles (20 to 80 g) were fired from the spring-loaded gun. One of the main objects of the experimental work was to obtain the strain-time history of the rod as a function of the mass and kinetic energy of the impacting hammers. For this purpose a technique involving wire resistance strain gages and a recording oscilloscope was employed. Five gages were applied at equidistant sections along the rod, and by means of a switching arrangement the strain-time history at any section, and for any impact, could be obtained in the form of an oscillograph with a time base. The equation relating strain and voltage change across a strain gage through which a constant current is flowing is as follows: e = ?v/iRF [1] ? = strain, ?v = voltage change, i = gage current, R = gage resistance, and F = gage factor (from manufacturer's data — SRA type, Baldwin Lima Corp.). With the above equation an oscillograph depicting voltage change vs time on a single trace can be converted directly to a strain-time diagram if a calibration of the vertical response on the oscilloscope screen for specific voltage inputs is available. In the present case the calibration was obtained by photographing precisely known audio frequency voltages on the same oscillograph as that on which a voltage-time trace from a strain gage had been made. Synchronization of the beginning of the single trace with the beginning of the impact was accomplished by permitting contact of the impacting objects to close an electrical circuit from which a voltage pulse, sufficient to initiate the trace, was obtained. The struck end of the rod was lightly silvered for purposes of electrical conduction so that it would form one of the electrical contacts. Markers every 100 micro-seconds on the traces served for a time base calibration. Determinations of the kinetic energies of translation prior to impact were made in the case of the pendulum hammers by measuring the height of fall of the hammer and in the case of the projectiles by measuring the exit velocity from the gun barrel by means of an electrical circuit employing light sources, slits, and phototubes.' During the experimental work it became evident that the time of contact between the impacting object and the rod was an important variable in the impact process. Measurements of the times of contact were made, therefore, for every impact for which a strain-time record was obtained. The time of contact was determined by permitting the impacting components, when in contact, to act as a closed switch and discharge a condenser at relatively constant voltage. The discharge was observed and photographed with a time base on the oscilloscope screen.

Jan 1, 1957

By H. A. Jr. Koch, C. A. Hutchinson

Miscible phase displacement of oil from reservoirs has been emphasized in the past few years. The reason for this emphasis lies in the high oil recovery attainable by this process. Removal of capillary effects in the reservoir leads to recoveries approaching 100 per cent in the area contacted by the miscible phase. The miscible slug process is one means of obtaining a miscible displacement. Here a band or slug of I,PG is injected into the reservoir prior to gas injection. The idea is to maintain the band of LPG "wedged" between the gas and oil phases and thus achieve a miscible phase displacement. A second method lor achieving miscibility is through the injection of a gas which is not miscible with the reservoir fluid but which develops a zone of miscibility in [he reservoir through mass trans-ier with the reservoir oil.' This mass transfer results in either an enrichment of the lean injected gas by intermediates from the oil or an enrichment of the oil by intermediates from a rich injection gas or one that has been enriched on the surface by LPG addition. We are interested here in discussing the process in which miscibility is developed at the displacement front by the evaporation of interrnediatcs from the oil phase into the gas phase. This process "builds up" its own slug of miscible material at the displacement front and therefore does not require the injection of LPG to obtain miscibil-ily. Each process has its own area of applicability. Generally, the high pressure gas process is applicable only with reservoir fluids which con-!ain a high concentration of inter- mediates. If the high pressure gas process is technically feasible at pressures less than 4,500 psi, it is probably more desirable economically than the slug process. The slug process has broad applicability in the shallower reservoirs and with reservoir fluids which contain a relatively low concentration of LPG and natural gasoline constituents. This paper deals with some new concepts of the high pressure gas injection process where it is proposed that flue gas can be substituted for hydrocarbon gas without sacrificing our goal of miscibility. MECHANISM Introduction Considerable effort has been devoted to study of the mechanics ot the high pressure gas injection proc-one generalization result-ing from some of these studies was that the composition of the injected gas is relatively unimportant in establishing the miscibility pressure* for a given reservoir fluid. This generalization is correct for the composition range of gases typically encountered in the field. Two such gases are a gasoline plant tail gas containing 85 per cent methane and 15 per cent ethane, and a field separator gas containing 70 per cent methane and 30 per cent heavier components. The most important factor which sets the miscibility pressure in the operation is the reservoir fluid composition, particularly the concentration of LPG-natural gasoline constituents. The injected gas is the agent by which the LPG-natural gasoline constituents are concentrated at the displacing front to create a miscible displacement. Based on these results, it appeared feasible that some inexpensive gas, such as flue gas, might be substituted for hydrocarbon gas for use in the high pressure gas process. A re-examination of the phase relations of the high pressure gas injection process should clarify the principle behind using flue gas (essentially nitrogen) as an injection gas. Three Component Diagram The phase relations of the high pressure gas injection process have been illustrated by the use of the three component diagrams.'," In Fig. 1 we have arbitrarily represented the multi-component reservoir system by three components; methane, ethane through hexane, and heptanes plus. The solid curve ABC is the phase boundary curve. It represents the locus of compositions which have fixed saturation pressure at a fixed temperature; the lower branch AB shows bubble point compositions, the upper branch BC, the dew point compositions. Point B is the coniposition of the critical mixture at this temperature and pressure. The dashed lines (tie lines) connect vapor and liquid compositions which are in equilibrium. Let us consider Reservoir Fluid D which we wish to displace in 21 miscible manner by gas injection. Let us further restrict the discussion to the case where miscibility between an injection gas and the reservoir fluid at the displacement front is developed by gas enrichment in the reservoir. For this case, any gas whose composition lies between Points C and E on the right side of the three component diagram can be used to give a miscible displacement of Reservoir Fluid D. This is true because the more mobile injected gas moves faster than the displaced oil and is in continuous contact with virgin oil at the displacement front. This leads to a continuing enrichment 01' the gas at the displacement front by evaporation of the C, - C,

By F. D. Rosi

The slip and twinning behavior in extended titanium crystals were studied in some detail. The formation and appearance of coarse kink bands are discussed. Their crystallographic geometry was determined by X-ray analysis. A phenomenological interpretation of the complexities in kink band development is also presented. The critical resolved shear stress, coefficient of shear hardening, and plane of fracture were determined for several crystals extended at room temperature. THE slip and twinning elements observed in the room-temperature deformation of titanium were enumerated in a previous paper1 in which considerations were advanced regarding the nature and selection of these elements and their effect on the known mechanical properties of this metal. The present study concerns the crystallographic, microscopic, and mechanical aspects of flow in relation to the slip and twinning elements, and includes a prediction of slip systems, nature of slip and twin markings, inhomogeneities of plastic flow, and stress-strain characteristics. Unless otherwise noted, arc-melted titanium sponge (99.77 pct) was used in these experiments. The method of production of crystals, their dimensions, and the surface preparation for micrographic examination have been reported.&apos; For obtaining stress-strain characteristics, only those crystals which traversed the entire width of the specimen and were at least 8 mm in length were used. Tensile deformation of the crystals was performed with conventional grips for sheet specimens and a constant-stress loading beam, designed after the method of Andrade and Chalmers.&apos; The specimens were loaded by allowing sand to flow from a reservoir into a bucket suspended from the longer end of a balanced 6:1 lever arm at a rate controlled to load the specimen approximately 2 kg per min. Strain measurements were made using the Baldwin SR-4, bonded, resistance-wire strain gage, Type A-8, which permitted a reading accuracy of 2 microinches per inch. The formulas used in the evaluation of shear stress and shear strain, as in deriving the coefficient of shear hardening, are given by Schmid and Boasv n terms of the original orientation and change in length of the crystal. For calculating the critical resolved shear stress, the standard equation was used. The crystallographic nature of the unpredictable slip observed in a number of specimens was determined by the single-surface X-ray method of analysis as described in ref. 1. Experimental Results Prediction of Slip System: It was reported&apos; that room temperature slip in titanium takes place predominantly on {10i0} and in a <1120> direction, giving three potential slip systems. Hence, it should be possible to predict the operative primary system in the manner used by Taylor and Elam&apos; for alu- minum (i.e., the one with the greatest component of shear stress in the direction of slip). The stereo-graphic construction in Fig. 1 shows that this is true. In all cases, slip was found to occur initially on the (0110) plane and, in a number of cases, in the [21f0] direction. (The direction of slip was not determined for all orientations.) It follows that duplex slip can be expected when two slip systems are geometrically equally favorable for slip, as demonstrated in Fig. 2. In both crystals slip took place simultaneously on the (1700) and (olio) prismatic planes, as indicated by Fig. 2a and b. In the case of crystal B the movement of the specimen axis with increasing extension was toward the (10i0) direction, which represents the stable end orientation resulting from alternate slip on the [2ii0] and [1120] directions. This is analogous to the duplex slip process in face-centered cubic metals." Unpredictable Slip: In a number of crystals whose orientations were well within the operation of a single slip system, secondary slip occurred on planes not predicted by the criterion of maximum shear stress. Examples are shown in Fig. 3. In addition to

Jan 1, 1955

By W. J. Maraman, D. R. Harbur, J. W. Anderson

A device for rapidly quenching liquid metals into thin platelets has been developed at the Los Alamos Scientific Laboratory. This rapid quenching equipment is built around the technique of catching a molten drop of metal between a rapidly closing plate and a stationary plate. The design and operation of this unit are described. The closing speed of the smasher plate at impact is 12.6 ft per sec. The quenching rate for this device is controlled by the interface resistance between the plates and the platelet, and is dependent upon the heat content and density of the material being quenched. The initial quenching rate down to the freezing point of the platelet material is lo5º to 106ºC per sec. After an isothermal delay, which is poportional to the heat of fusion of the platelet material, the final cooling rate down to the temperature of the smaslier plates is l04ºto 105cº per sec. RAPID heating of metals by capacitor discharge and other methods has provided the metallurgist with a useful tool for probing into the kinetics of phase changes and the many nonequilibrium phenomena which occur during rapid temperature changes. Equally interesting studies can also be made on metals and alloys which are rapidly cooled from the liquid state.&apos; Studies in this field have been limited, however, because the rates at which metals could be cooled were many orders of magnitude slower than the rates possible for heating. In recent years many new laboratory methods have been developed to rapidly cool metals from the liquid state to ambient temperature and below.2"4 All of these methods involve spreading a liquid drop of metal into a thin foil in a very short time. The methods developed have varied from ejecting a drop of molten metal at the inside surface of a rotating cylinder or stationary curved plate to catching a falling drop of molten metal between rapidly closing plates. The equipment which has been developed at the Los Alamos Scientific Laboratory for rapidly cooling molten materials uses the latter of these two approaches. The basic design, operation, and initial results of this rapid quenching device are given in this report. APPARATUS The drop smasher, which is now being used to obtain rapidly cooled metal foils, is shown in Fig. 1. Basically the device consists of a smasher plate which is driven by a solenoid into a stationary plate. The solenoid is activated by a drop passing through the photoelectric cell and is powered by discharging an adjustable 350-v capacitor bank with a 66-amp peak current into it. This power supply is designed so that the solenoid is powered for 2 m-sec after plate closure to minimize the rebound effect. There is an adjustable time-delay mechanism between the photoelectric cell and the solenoid. Both smasher plates have changeable inserts so that a variety of materials can be used to smash the molten drop. The shaft of the moving plate is guided in an adjustable housing which has ball-bearing walls. The cabinet shown to the left of the drop smasher in Fig. 1 contains the power supply and receiver for the photoelectric cell, the time delay mechanism, and the capacitor bank. The drop smasher can be placed inside a vacuum chamber, for use with radioactive materials, with the upper plate forming the lid, as shown in Fig. 2. On top of the vacuum lid is an induction coil, powered by an Ajax induction generator, which is used to melt drops from the end of the rod extending through the vacuum seal on top the quartz tube. OPERATION The drop smasher shown in Fig. 2 is operated in the following manner. The smasher plates are separated and the unit is lowered into the vacuum chamber using a pressurized cylinder. The induction coil, quartz tube, and lid with sliding vacuum seal are then assembled on top the vacuum chamber. A rod of the material for rapid quenching studies is connected to the rod extending through the sliding vacuum seal. The vacuum chamber is then evacuated and the desired atmosphere established. The photoelectric cell is turned on, and the capacitor bank is charged and armed. Power is supplied to the induction coil, and the rod of material for rapid quenching studies is lowered into the induction field. A molten drop forms on the end of the rod, drops off, falls through the light beam of the photoelectric cell, and is then caught between the smasher plates. .

Jan 1, 1970

By W. M. Robertson

The rate of crack Propagation thvough a solid meta1 in the presence of a liquid metal has been calculated. The crack is assumed to propagate by solution of the solid in the liquid under the influence of an applied stress, with volume diffusion of the dissolved solute through the liquid controlling the propagation. The calculated velocities can be tens of centimeters per second or higher. THE embrittlement of normally ductile solid metals by liquid metals has been the subject of extensive study, as summarized in the book by Rostoker, McCaughey, and arkuus.&apos; In experimental studies of liquid-metal embrittlement it is usually concluded that the observed crack-propagation rates are too high to be accounted for by diffusion processes. Diffusion is considered to be an unimportant factor and various other mechanisms are invoked to account for the experimental observations. The similarities of liquid-metal embrittlement to stress-corrosion cracking, to hydrogen embrittlement of steel, and to low-temperature embrittlement of bcc metals are frequently used as analogies for these mechanisms.1"3 The present paper assesses how rapidly a crack could propagate by a mechanism of volume diffusion through the liquid metal. We assume that the crack propagates by solution of the solid in the liquid at the crack tip under the influence of the applied stress and diffusion of the dissolved solute away from the crack tip. The model uses only macroscopic thermodynamic, kinetic, and elastic concepts. The calculations indicate that this dissolution-diffusion mechanism can give high crack velocities. In some previous treatments4&apos;&apos; of crack propagation in a liquid-metal environment the fundamental step has been the breaking of atomic bonds at the crack tip. The liquid greatly decreases the energy necessary to break these bonds. The present model assumes the crack is filled with liquid metal; the presence of the liquid is essential because diffusion through the liquid is assumed to control the rate of propagation. With proper modification this model could also apply to stress corrosion in a liquid environment. THEORY Consider a crack in a homogeneous elastic continuum, ignoring all the structural details of the solid. This neglects a host of metallurgical details which can be significant in the problem of liquid-metal embrittlement;&apos; but this simple assumption is a useful approach in evaluating the role of diffusion through the liquid. The stress distribution around the crack tip establishes a gradient in the chemical potential at the tip, which causes a diffusion flux through the liquid away from the tip. The solid-liquid interfacial tension works against crack propagation, since propagation requires creation of interfacial area. From these two considerations we derive the diffusion flux, which then yields an expression for the velocity of the crack tip. The concentration of the solute in the liquid, C, is equal to the equilibrium concentration in the presence of an unstressed, flat surface, Co, plus the excess concentration due to the stress, AC(a), plus the excess concentration due to capillarity, AC(y): We calculate AC(o) and AC(y) and then obtain the diffusion flux. Consider (Fig. 1) a long flat crack of length 2L, thickness 2r, and tip radius r, where r remains constant as the crack propagates in the positive x direction. There is no stress ay in the y direction across the flat surfaces of the crack. The magnitude of the stress at the crack tip due to the applied stress, a,, is given by the relation6 ^=^[l-2^] 12] which, for long narrow cracks, becomes The stress increases the chemical potential in proportion to the strain energy.? The excess chemical potential due to the stress, Ap(a), is given by where 52 is the atomic volume of the solid and E the Young&apos;s modulus. Inserting Eq. [3] gives Now consider the crack to be filled with a liquid metal. The excess solubility due to stress, hC(a), is given by the excess chemical potential due to capillarity, Ap(y), is given by8 where y is the solid-liquid interfacial energy, and v1 and YZ are the two principal radii of curvature of any surface point. At the crack tip, r1 = -r and vz = m, so TRANSACTIONS OF THE METALLURGICAL SOCIETY OF AIME

Jan 1, 1967

By J. B. Conway

Stress-vuptuve data for several of- the refractory metals are frequently found to yield a linear relationship between the Larson-Miller parameter and the logarithm of the applied stress. In such cases linear stress-rupture isotherms result with slopes bearing a definite relationship to the temperature. It also follows that the stress to produce rupture in a certain period of time will be linear in temperature. Data for several refractory metals have been reviewed and excellent linearity is shown in this type of isochronal plot. In addition, the af ore - mentioned lineavity leads to a linear relation between the log of the stress to produce rupture in a certain time and the homologous temperature. This has been illustrated for the Group VI-A metals, tungsten and molybdenum. EXTENSIVE use has been made of the Larson-Miller&apos; parameter in the interpolation and extrapolation of stress-rupture and creep data. In those cases where this particular parametric approach is applicable a convenient and fairly straightforward procedure is made available for the correlation of experimental stress-rupture data. It is quite common to employ this parameter in the form of a master rupture plot in which the parameter, T(C + log tr), is expressed as a function of log stress. In many cases this functional relationship in log stress is linear within acceptable accuracy and hence the following relation results: where P is the parameter, C is the Larson-Miller constant, T is the absolute temperature, t~ is the rupture time, a is the stress, and a and b are constants. Examples of such a relationship are contained in the work of Green, Smith, and 01son2 dealing with high-temperature rupture behavior of molybdenum and in the work of Green&apos; dealing with the high-temperature behavior of tungsten. In addition, pugh4 has shown a similar linearity for some fairly low-temperature data for molybdenum. It can be shown that when the relationship in Eq. [I] is exhibited certain generalizations can be made concerning the form of the stress-rupture isotherms. For example, rearranging yields: For a given material (constant C) at a given temperature the first term on the right-hand side of Eq. [2] is a constant and hence this equation defines a straight line when log stress is plotted as a function of log-rupture time. This is recognized as the standard form usually employed in this type of data presentation. Such linearity then suggests the linear form of the Larson-Miller parameter. Or, in other words, the linear parametric relationship in Eq. [2] results only when the stress-rupture data are linear on a log-log plot of stress vs rupture time. Another interesting observation can be made in regard to Eq. [2]. It can be noted that the slope of the stress-rupture isotherms is given by - T/b and hence a direct calculation of the constant b is available. It also follows that since the value of b is the same for all temperatures the slopes of the various isotherms on the log-log stress-rupture plot cannot be the same. Indeed, the existence of the relationship in Eq. [2] precludes a system of parallel lines on this common stress-rupture plot. As a matter of fact it further specifies that in addition to being nonparallel the slope of these isotherms must decrease (i.e., become more negative) with increasing temperature. Such a condition is indeed found to exist in the case of the stress-rupture data reported for molybdenum.&apos; As a corollary to the above, it may be stated that stress-rupture data which do not lead to a linear log-log stress-rupture plot or whose isotherms do not exhibit a decrease in slope as the temperature increases will not yield the linear relationship of Eq. [I]. Applying Eq. [2] to two different temperatures and solving for C yields: Eq. [3] affords a simple and rapid method for calculating the Larson-Miller constant from the log-log stress-rupture plot. The slope of a given linear isotherm is measured and the value of "b" calculated based on Eq. [2] as: slope = - -Tb Then at an abscissa value of 1.0 hr (making log tr in Eq. [3] equal to zero) read the stress corresponding to rupture for two different temperatures. Substitution in [3] yields: A value of the Larson-Miller constant can thus be calculated from a few simple mathematical procedures employing data read directly from the log-log plot of the stress-rupture data. Of course, it is not to be overlooked that the above reasoning has been based on the linear relationship of Eq. [I] being applicable. However, if as mentioned above the log-log plot is

Jan 1, 1967

By D. P. Harris

The construction of a model to associate probability of occurrence of some measure of mineral wealth with the geology for each subdivision (cell) of the area is postulated. The questions (1) are the observations made in reconnaissance geology sufficiently related to mineral wealth to distinguish the cells of high value from those of low value, and (2) can this geology be related mathematically to mineral wealth and probability are answered in a case study of 97,000 square miles in Arizona and New Mexico. Measurements on mineral wealth and geologic variables of 243 cells were made. The geologic variables, valued in counts, percentages and lengths, quantified the theoretical concepts of the model. It was found that multiple discriminant analysis and classification analysis by Bayesian statistics and multivariate normal probability function constitute a two-phase probability model that associates probabilities with geologic information and mineral wealth. The cells of explored area must be allotted the value class indicated by their cumulative production and estimate reserves (given well-defined geological relationships in a mineral wealth area), and a discriminant and classification analysis must be performed in which probabilities of the cell belonging to each of the value groups are generated as a function of the geologic variables. This determines whether high value cells can be distinguished from low value cells by their geology as well as indicating those cells misclassified by the model into a higher value group than warranted by their known mineral wealth. The second use of the model is for extrapolation. It is demonstrated how geologic information on an explored area can be utilized in guiding exploration in an unexplored area. Exploration decisions can be predicted on explicitly determined measures of uncertainty (the probabilities). SUMMARY This study postulates the construction of a model to associate probability of occurrence of some measure of mineral wealth with the geology for each subdivision (cell) of the area. Such a model will distinguish those cells deserving further exploration on the basis of their geology: The basic postulates of this study are as follows: v = Q(R,S,F,A) P(V) = G(R,S,F,A,V), where V = a measure of mineral wealth P(V) = the probability of occurrence of V R = age and type of rock F = rock fracturing A =age of igneous activity and contact relationships. There are really two questions to be answered: 1) are the observations made in reconnaissance geology sufficiently related to mineral wealth to distinguish the cells of high value from those of low value, and 2) can this geology be related mathematically to mineral wealth and probability? In order to answer these questions, an area of about 97,000 square miles situated chiefly in Arizona and New Mexico was selected as a case study. This case study area was divided into 243 cells, each 20 miles square, and measurements were made on mineral wealth and geologic variables. Crude geologic variables valued in counts, percentages and lengths are constructed to reflect the above postulated variables. These measurement variables thus provide quantified values defining the theoretical concepts of the model. It was found that multiple discriminant analysis and classification analysis by Bayesian statistics and the multivariate normal probability function constitute a two-phase probability model that associates probabilities with geologic information and mineral wealth. Given the availability of an area that is well explored and upon which the relationships of mineral wealth to geology can be adequately defined, there are two ways in which the analysis outlined in this paper can prove beneficial. First, the cells of the explored area must be allotted the value class indicated by their cumulative production and estimated reserves, and a discriminant and classification analysis must be performed in which probabilities of the cell belonging to each of the value groups are generated as a function of the geologic variables. Such an analysis determines whether cells of high

Jan 1, 1967

By N. Mungan

Laboratory imbibition and displacement experiments were performed using crude oil and cores drilled with water and preserved under anaerobic conditions. The purpose of these tests was to determine reservoir rock wettability and to find out if more oil could be recovered by use of NaOH solution than by conventional waterflooding. The preserved cores were found to be oil-wet. Contrary to work in the literature, these cores changed to water-wet upon contact with air. After exposure to air for a week, the cores yielded more oil by waterflooding than when preserved under exclusion of air. At reservoir temperature of 160F, flooding the preserved cores with 0.5N NaOH solution recovered more oil than an ordinary wa-terflood, and additional oil when following a waterflood. When the caustic solution was used from the beginning, all the extra oil was obtained before breakthrough; when the caustic followed a conventional waterflood, the extra oil was produced in the form of an oil bank ahead of the injected caustic. The increase in oil recovery resulted from wettability reversal. Also, use of caustic reduced the volume of injection required to flood out the cores. At room temperature, however, the caustic solution did not reverse the wettability and gave no additional oil recovery. Cores which had become water-wet by air exposure or caustic flooding were restored to their original oil-wet state when saturated with crude oil and allowed to equcilibrate at reservoir temperature for two weeks. Therefore, in the absence of preserved cores, it may be possible to restore weathered cores to their original wettability for use in laboratory floods. INTRODUCTION Waterflooding has been in use since 1865, and is by far the simplest of secondary recovery methods. Unfortunately, most waterfloods are inefficient in recovering oil, often leaving half or more of the original oil in place un-recovered. The low oil recovery generally results from low sweep efficiency and low displacement efficiency. Consequently, to increase oil recovery by waterflooding, sweep and displacement efficiencies should be improved. Sweep efficiency is primarily affected by reservoir heterogeneities and mobility ratio, while displacement efficiency is affected by the capillary forces between fluids and rock surfaces. For petroleum reservoirs, the capillary forces are expressed in terms of interfacial tension and wettability. If oil recovery is to be improved significantly in water- flooding, the capillary forces holding the oil in the raervoir porous matrix must be reduced or eliminated. One way to reduce capillary forces is to inject commercial surfactants ahead of the injection water into the reservoir. Laboratory tests of this method have shown no promise of an economical process yet, and no increase in oil recovery was obtained in the field trials which have been reported. Work is continuing in many companies to find surface-active agents which, in workable concentrations, can yield substantial added oil recovery. Another way to change capillary forces operating in petroleum reservoirs is by changing the pH of the injected water. Wagner et al.&apos; showed that change in the pH sometimes activates the surface-active materials natural to some crudes and brings about gross wettability change. Since pH alteration can be obtained with cheap chemicals, such as hydrochloric acid or sodium hydroxide, the process shows promise of being economical in a field application. Pan American Oil Corp. reported oil recovery by use of caustic solution from a flooded-out reservoir.&apos; Their test, conducted at a small additional cost, yielded results which were so sufficiently favorable and encouraging that the wettability reversal flood was expanded to portions of the field not previously flooded.13 It is important to bear in mind that changes in the pH of the water not only can reverse wettability but also can lower the interfacial tension between water and crude oil. Reisberg and Doscher4 have studied the pH dependency of the interfacial tension of Venture crude using sodium hydroxide solutions of various concentrations. Their data show that the interfacial tension was lowered from 23.0 to 0.02 dynes/cm by increasing the NaOH concentration from 0.005 to 0.5 per cent by weight. Thus, the use of NaOH may lead to additional oil recovery due to both wettability reversal and lowering of interfacial tension. Whether alteration of pH results in wettability reversal from oil-wet to water-wet and increases oil recovery depends on wetting properties of the reservoir rock and the crude. This necessitates delicate laboratory experiments, with suitable core and fluid samples from a field. Although many investigators have studied wettability reversal floods in the laboratory,1,2,5,6 these studies have been carried out with synthetic porous media, refined laboratory fluids and surface-active chemicals to simulate the process. The study presented in this paper is the first time that wettability reversal by pH alteration has been accomolished in laboratory core floods using carefully preserved natural cores, live crude and with experiments performed at reservoir pressure and temperature.

Jan 1, 1967

By C. S. Giggins, F. S. Pettit

The oxidation properties of Ni-Cr alloys with fine grains, coarse grains, and deformed surface layers have been studied at temperatures of 900" and 1100°C in 0.1 atm of oxygen. The oxidation rates of alloys containing between 10 and 30 wt pct Cr have been found to be dependent upon the grain size of the alloy. Finegrained alloys had smaller oxidation rates than coarsegvained alloys because of the selective oxidation of chromium at alloy grain boundaries. In this compositional range alloys with deformed surface layers behaved similar to fine-grained alloys due to recrys-tallization of the deformed surface layer. In the preceding paper1 it was found that during the oxidation of Ni-Cr alloys, the volume fraction of precipitated Cr2O3 could be greater at alloy grain boundaries than at other areas of the alloy surface. In the case of alloys with chromium concentrations equal to or greater than 30 pct,* the volume fraction of Cr2O3 *AIL compositions are given as weight percent unless specified otherwise. precipitated at grain boundaries and within grains on the alloy surface both exceeded the critical amount required for lateral growth of the Cr2O3 particles and the surfaces of these alloys were completely covered with a continuous, external layer of Cr203 during oxidation. However, in the case of alloys with chromium concentrations between approximately 5 to 30 pct, the volume fraction of precipitated Cr2O3 exceeded the critical value required for external scale formation only at grain boundaries.but not within the interior of the grains. Consequently, the surfaces of these alloys had external scales of Cr3O3 over the grain boundaries but internal Cr2O3 subscales with external scales of NiO away from the grain boundaries. Under these latter conditions, it was found that chromium could diffuse laterally in the alloy from those areas covered with an external layer of Cr2O3, i.e., grain boundaries, to areas where the Cr2O3 was present as a subscale. This diffusion of chromium resulted in an increase in the volume fraction of Cr2O3 precipitated in the sub-scale zone and continuous layers of Cr2O3 could be formed at the subscale front in these regions. For the alloys used in the previous studies,&apos; continuous layers of Cr2O3 were formed on Ni-20Cr alloys in the subscale regions after approximately 30 hr of oxidation at 900°C. For shorter periods of oxidation, the Cr2O3 layer was semicontinuous with the continuous portion at the subscale front emanating from points where the Cr2O3 had been formed as an external scale over alloy grain boundaries. Some lateral growth of a Cr2O3 layer in the subscale region was observed on Ni-15Cr and even Ni-10Cr alloys but this layer was never continuous after 30 hr of oxidation. These results indicate that the selective oxidation of chromium in Ni-Cr alloys with chromium contents between 5 to 30 pct may be dependent upon the grain size of the alloy. Fine-grained specimens in this compositional range should have a larger fraction of the surface covered with external Cr2O3 than coarsegrained specimens and the subscale areas required to be sealed via lateral diffusion of chromium should be smaller. It is therefore to be expected that a continuous layer of Cr2O3 can be formed on alloys in this compositional range after short periods of oxidation providing the alloy grain-size is sufficiently small. bo studieS2,3 have established that the oxidation behavior of alloys can be significantly influenced by pretreatments which produce mechanically deformed surfaces. It has been found that deformed surfaces usually promote the selective oxidation of elements in alloys and it is believed that these effects are due to rapid diffusion of elements in the deformed layer. In view of the previous results,&apos; which showed that alloy grain boundaries may play an important role in the selective oxidation of chromium in Ni-Cr alloys, deformed surfaces may promote the selective oxidation of elements in alloys as a result of the numerous grain boundaries formed on the alloy surfaces via recrys-tallization during heating to the oxidation temperature. The purpose of the present studies was to determine the effect of alloy grain size and surface deformation on the selective oxidation of chromium in Ni-Cr alloys at temperatures of 900" and 1100°C in 0.1 atm of oxygen. EXPERIMENTAL The average grain diameter of the alloys used in the previous studies1 was not less than 0.04 mm and alloys with compositions between 5 and 30 pct chromium had average grain diameters between 0.04 and 0.14 mm. Since the oxidation kinetics were already available for these relatively coarse-grained alloys, it was desirable to use these same alloys in the present studies. The surfaces of the alloys listed in Table I of the previous paper were deformed by using a Model F S.S. White Industrial Airbrasive Unit, which delivered a controlled mixture of 25 µ Al2O3 particles in a stream of dry air at high velocity against the surface of a specimen. The amount of surface deformation produced by this treatment was not determined but a re-crystallized layer about 15 µ thick was formed upon annealing deformed specimens. The grain size at the surface of the specimens was reduced to an average grain diameter of 0.01 mm by annealing the deformed specimens, i.e., grit-blasted,

Jan 1, 1970

By P. L. Hendricks, J. W. Spretnak

The interstitial atom principally responsible for the yield point and strain aging in electron-beam-melted tantalum is identified by analysis of the kinetics of the return of the yield point after an increment of plastic deformation. Two sets of specimens contained two levels of oxygen with very low hydrogen contents and the third set had comparable oxygen and hydrogen contents. The activation energy for the return of the yield point agrees well with that for diffusion of oxygen for the first two sets of specimens. For the third set of specimens, the activation-energy value lies between those for diffusion of hydrogen and for diffusion of oxygen. The advent of the dislocation model of plastic deformation in metals has revitalized interest in the yield point and strain aging in bcc metals containing a certain minimum content of interstitial solute elements. Much theoretical and experimental work has been performed in recent years to elucidate the detailed mechanism of these phenomena. The purpose of this investigation is to attempt to identify the principal interstitial element responsible for the yield-point phenomenon in electron-beam-melted tantalum by analysis of the kinetics of the return of the yield point after an increment of plastic deformation. Some of the earlier theories of the yield-point phenomenon proposed a grain boundary film of iron carbide. Such models could not satisfactorily explain all features of strain aging and the yield-point phenomena. The most widely accepted explanation is that of Cottrell,1 later extended by Cottrell and Bilby.2 Strain aging is ascribed to "locking" of dislocations by interstitial solute "atmospheres". The yield-point phenomenon results when the dislocations are torn away from their atmospheres. The strain-aged condition is re-established after sufficient time to allow the interstitial atoms to diffuse to the dislocation lines and re-establish the locking atmospheres. Clearly, the Cottrell-Bilby model is concerned with the bulk of the grain and does not specifically involve the grain boundary. The recent modification of the Cottrell-Bilby model is a redirection of attention to the role of the grain boundary and the possibility of multiplication of a limited number of free dislocations rather than unlocking all of the dislocations. Theories have been advanced by Hahn3 and conrad4 which are modifications of the Cottrell-Bilby theory. The model proposed by Hahn indicates that, although the possibility of un- locking anchored dislocations is not excluded, it implies that unlocking is not necessarily required to explain yield drop. Locking of dislocations during the aging treatment is a necessary part of the theory; however, it assumes that dislocations once locked remain locked. It is suggested that the yield drop observed is a result of the following factors: 1) the presence of a small number of mobile dislocations initially, 2) rapid dislocation multiplication, 3) the stress dependence of dislocation velocity. In the case of bcc metals, locking is considered to be the means by which dislocations are immobilized. Cold working of the metal results in the generation of larger numbers of new dislocations and the stress dependence of the dislocation velocity accounts for yield drop observed. Conrad&apos; has proposed a model similar to the one just described which applies to strain aging of iron and steel and which logically could be extended to other bcc metals. This model also does not require large-scale unlocking of dislocations. It is proposed that, during initial loading of a specimen below the upper yield stress, a few dislocations are torn free of their Cottrell atmospheres at regions of stress concentrations. With an increasing stress, some multiplication of dislocations occurs by a double cross slip mechanism, thus giving a preyield microstrain. At some critical stress represented by the upper yield stress, sudden profuse multiplication of dislocations occurs, enabling plastic flow to proceed at a lower stress. In this model, microstrain, preyielding, and flow represent the movement of free dislocations. It should be noted that this model also requires the locking of dislocations by interstitial solute atoms for the occurrence of a yield point; however, unlocking of large numbers of dislocations is not required. If it is assumed that the yield point will return when some fraction of free dislocations produced during pre-straining are pinned, the number of solute atoms required to pin unit length of a dislocation line can be calculated when prestrain and reloading are done at the same temperature and strain rate. Since the migration of solute atoms back to the stress fields of dislocation lines is controlled by the diffusion rate of interstitial solute atoms, it is to be expected that the activation energy for strain aging would be identical to the activation energy for diffusion. It would also be expected that the strain aging observed will be controlled by the fastest diffusing species capable of producing locking over the temperature range investigated. The rate of yield-point return has been found to be adequately expressed by an empirical rate equation of the form: rate=Ae-Q/RT [1] where A = constant, Q = activation energy, R = gas constant, and T = absolute temperature. Cottrell and Bilby2 have expressed the number of atoms per unit length of dislocation line which arrive

Jan 1, 1967

By P. R. Sahm, T. V. Pruss

Mixtures of fine GaSb and Gds as well as preal-loyed GaSbl,As, powders were hot-pressed at 690°C and 25,000 psi. Dense alloys with compositional gradients of less than 5 pct were obtained from mixtures containing about 20 mol pct GaAs. For x < 0.2, there were increasing compositional gradients, and for x > 0.2 a GaAs-rich second phase appeared in the microstructure. Densification as well as alloying wlechanisms were enhanced by dissociation and, possibly, oxidation reactions of the powders. Densification of coarse prealloyed material, however, primarily depended on plastic flow phenomena and required temperatures just below solidus and pressures of 50,000 psi Thermal and electrical properties were measured. Although in no case was the figure of merit of melt growth materials approached closer than to within 25 pct, the better overall thermoelectric properties were found in coarse-grained, prealloyed materzals which had been compacted to near theoretical density and where grain regrowth had been induced. Similar results are believed to hold in other binary 111-V compound systems if processed under similar conditions. The densification of unalloyed GaSb powders during pressure sintering (= hot pressing) was shown to depend strongly on powder particle size.&apos; Fine powders displayed a "liquid skin effect" that enhanced compaction through the presence of liquid gallium, whereas coarse powders compacted predominantly by plastic flow. The liquid skin effect, in particular, appeared attractive for alloying GaSb with other, higher-melting, III-V compounds, and to densify these in a one-step operation. This is of special interest in the case of III-V compound alloys as the conventional techniques of melt growth or long-time annealing of powders2 is very time-consuming, especially in cases where a large separation of liquidus and solidus can be expected, such as in GaSbl alloys.2 It was felt that experimentation with this system, a particularly unfavorable example, would allow us to extrapolate to several other, more favorable, cases. Uses of Ill-V alloys are most evident in thermoelectric energy conversion devices.&apos; For this reason certain thermal and electrical properties were measured and compared to those of melt-grown material and to hot-pressed prealloyed powders. EXPERIMENTAL PROCEDURE The pressure-sintering apparatus has been previously described.&apos; Using this equipment, both powder mixtures of GaSb with GaAs and prealloyed GaSbl-,As, powders were hot-pressed. The mixtures were pre- pared from cast GaSb and melt-grown GaAs. The prealloyed material was obtained from stoichiometric melts, initially heated to 1200°C in an evacuated quartz ampoule, and then annealed in the solidus-liquidus interval. A typical annealing cycle consisted of a heating to 850°C (1 hr), extended successive annealing at 750°C (65 hr), and slow stepwise cooling (25 hr) to below solidus. The GaSb, GaAs, and GaSbl-,As, materials were ground in a vibrational mill to particle sizes below 500 . A jet mill reduced these further where necessary. Fine powders were analyzed by Coulter counting for their size distribution. Average sizes by volume were calculated from the data. Mixing of the powders, where necessary, was carried out through rapid vibrational motion. The hot-pressing operation consisted of a degassing period of 15 hr, in most cases at 690°C, followed by several hours of compression, normally 25,000 psi at 690°C for powder mixtures and 50,000 psi at 710°C for prealloyed powders. The chemical compositions were confirmed by X-ray fluorescence analysis. To estimate the degree of solid solution achieved, lattice parameters were determined and interpreted according to Vegard&apos;s rule. In addition, optical microscopy helped to correlate the relative amounts of the phases present as well as the degree of porosity to the measured density. To reveal grain boundaries, polished surfaces were etched4 with H 2 O:H 2 O:HCl = 2:l:l. In several cases microscopic concentration gradients were monitored by electron-probe analysis-. RESULTS AND DISCUSSION Alloying and Densification of GaSn-GaAs Powder Mixtures. After preliminary experiments showed that no appreciable alloying took place in mixtures of coarse GaSb (22.5 p) and fine GaAs (2.5 p) powders, hot pressing of mixtures was confined to fine powders only (3.1 and 2.4 p, respectively). Alloying and densification apparently occurred simultaneously with a grain regrowth mechanism which depended on the presence of a liquid phase.&apos; The liquid phase was provided by the dissociation of GasbS particles into liquid gallium and antimony above 555°C. This not only enhanced grain regrowth and densification, as in unalloyed GaSb,&apos; but took on additional importance here for the alloying process. Alloying was speeded up by the resulting liquid-solid interaction as compared to the very slow solid-state diffusion process normally expected at these temperatures.&apos; The results obtained with a series of powder mixtures have been compiled in Table I. It is seen that for mixtures with less than 20 mol pct GaAs, x < 0.2, the compositional ranges increased and for x > 0.2 a GaAs-rich phase and free antimony appeared in the microstructure in sizable amounts.

Jan 1, 1968

By J. Gordon Parr, D. H. Polonis

High purity alloys of titanium and iron, made by a technique of levitation melting, have been investigated with particular reference to martensite formation and decomposition in the hypoeutectoid range. A preliminary study has been made of the occurrence of the phase corresponding to the structure Ti2Fe. MANY of the previous investigations of Fe-Ti alloys have been made using Kroll sponge as a source of titanium; and the subsequent heat treatments to which alloys have been subjected has, on occasion, led to further contamination. Worrier,&apos;,&apos; who suggested a part of the equilibrium diagram for the binary system, and Wallbaum and coworkers,3-5 who worked largely with iron-rich alloys, all used Kroll sponge. Van Thyne, Kessler, and Hansen,6 in their determination of the equilibrium diagram, used iodide titanium for alloys up to 30 pct Fe. Duwez,7 who measured the M. temperature of titanium binary alloys with many solute elements, used iodide titanium in all cases except in his work on Ti-Fe alloys for which he used Kroll sponge. The investigation of the supposed phase Ti2Fe by Rostoker8 nvolved the use of iodide titanium. A section of the constitutional diagram, after Van Thyne et al., is reproduced in Fig. 1. Frequently too much stress is placed on the effect of contaminants in equilibrium and nonequilibrium systems, but there is no doubt that titanium alloys are extremely susceptible to interstitial atoms. Consequently, the main purpose of the work to be described was to determine those features of phase transformations in pure Ti-Fe alloys that were considered of importance in commercial heat treatments. For, although commercial alloys may not be of high purity, the investigation of a system uncomplicated by traces of impurity is a desirable starting point. Another incidental feature, the occurrence of Ti2Fe, was also investigated. The entire study was carried out using powders obtained from alloy ingots, for diffusion reactions are often more rapid in small particles than in bulk specimens. The frequently adopted practice of ascertaining phase constitutions by X-ray analysis of powders, and relating these to the microstructures and mechanical properties of bulk specimens, is considered by the authors to be open to criticism. In the martensite reactions in the Fe-Mn system, for example, it has been shown- hat similar phase distributions in solid and powder may result in different hardness values and appearance under the microscope; and it is possible that similar anomalies might occur in the Ti-Fe system. Consequently, in order to

Jan 1, 1955

By P. A. Albert

THE to a transformation has been investigated by Newkirk1 in sponge titanium alloys which had been relatively slow-cooled so that several grains formed in a former grain. For a nucleated from , Newkirk assumed the following relationships and found them consistent with his experimental results: (00.1)a (110)Pll.01. II [111] Liu and Margolin,&apos; in their investigation, found that the habit planes of martensitic in titanium consisted of planes of the families (3341, and (3441,. Using Newkirk&apos;s orientation relationship, the (3341 habit plane is found to correspond to the (1450) plane of a.

Jan 1, 1954

By A. D. S. Gillies

The effectiveness of coal mine face ventilation and the ability of airflow to maintain satisfactory methane and respirable dust levels in the working face area has been studied through the use of scale modeling techniques and underground testing procedures. In particular, consideration has been given to examination of the effects of operation of a high airflow, machine mounted dust scrubber unit on face air patterns. Results obtained through a cooperative study with the Peabody Coal Co. demonstrate that new mining cycles can be considered that increase production efficiency while maintaining satisfactory ventilation conditions.

Jan 1, 1986

By C. H. Mathewson

MicrOscopic metallography has been exploited quite well enough to bring about a very general understanding that the typical metal or alloy is composed of minute crystalline particles blended into a coherent rnicrostructural rnosaic. One does not have to be a specialist in metallography to realize that the properties of such an aggregate are essentially a summation in appropriate form of individual effects derived from the shape, size, placement or orientation and cohesive characteristics of the component particles. It is clearly of great importance to consider the various forms of discontinuity which may occur at the boundaries between these crystalline particles. When a number of particles each possessing the same orderly arrangement of atoms are brought together into a close-fitting system of purely haphazard contacts, not unlike a handful of snowflakes compacted into a snowball, the particles are said to possess random orientation. There are no generally accepted views concerning the arrangement of the atoms or the constitutional reaction between atoms where one crystal meets another, but these contact regions are characterized by strength rather than weakness and it is customary to require the presence of many rather than few boundaries in preparing metal for useful service. Under certain circumstances all of the particles in a metal may be nearly alike in orientation. Other general tendencies of orientation may be associated with particular forms of mechanical and thermal treatment. In contrast with these cases of fortuitous or statistical diversity of orientation, we often find adjacent particles united along a plane which possesses a grouping of atoms belonging equally well to both structures. This, of course, determines a fixed relationship between the two orientatjions and it is always possible to derive one from the other by some form of- rotation or reflection prescribed by the symmetry of the crystal structure under consideration. Particles united in this manner are known as twin crystals although the term refers to the form of association rather than the number of individuals concerned.

Jan 1, 1928

By C. W. Goodale

I. INTRODUCTION. In the summer of 1909 the Boston & Montana reduction department of the Anaconda Copper Mining Co. completed a new flue system, at a cost of about $1,100,000, and -is this includes the largest and highest chimney in the world, and some new features of flue construction, a description will be of interest. At the Spokane meeting of the Institute in September, 1909, a brief mention was made of this flue system, in discussing Mr. Brunton&apos;s presidential paper on the Progress of Metallurgy in the West, and a promise was given that when a long enough time had elapsed, so that operating results could be given, a paper would be offered. The smelting plant includes blast furnaces, MacDougall roasters, gas-fired reverberatories, and converters.

Jan 8, 1913

By A. F. Taggart

This paper describes the result of a series of experiments run in the laboratory of the School of Mines, Columbia University, during the winter of 1927-28. It shows that the several operating adjustments of a pneumatic table produce effects in the action of a given coal that may be grouped into two classes, viz.: stroke length, speed and rocker-arm angle, which affect longitudinal travel; air supply and table slope (transverse and longitudinal), which determine transverse travel. The magnitude of the effect of the different adjustments varies. Some of the adjustments affect stratification of the bed, both as respects size and specific gravity of the bed components, as well as direction of travel. Operation of a pneumatic table is fundamentally different from that of a wet table in that the former exerts, through the air supplied, a force on the particles upward away from the deck which is lacking on the wet table while, on the other hand, it lacks the positive control over cross travel that is supplied by the wash and feed water. Apparatus The pneumatic table used is shown in Fig. 1. Deck A is 20 by 12 in. and consists of nainsook supported on slats that register with the riffles. Fig. 2 is a photomicrograph of the nainsook used. It shows that the cotton threads average about 0.13 mm. dia. and the apertures about 0.17 mm. The deck carries 12 riffles consisting of wooden strips, 3/16 in. wide and 1/4 in. high, laid parallel to the feed side of the table. The riffles terminate along a line starting on the feed side at a point 11 in, from the mechanism end and running to the corner formed by the coal side and slate end. Taper starts from a line that runs parallel to their terminal line through the junction of the upper riffle with the mechanism end. The height at the terminal line is about 1/32 in. The deck with its supporting slats is carried on a framework consisting of rails A, sloping end rails B, and adjustable metal strips C, which latter permit variation in transverse slope. This frame is enclosed at the edges by means of heavy canvas, indicated in the sketch by wavy lines, which makes a flexible conduit between the deck and the stationary air chamber,

Jan 1, 1930

By F. S. McNicholas

IN the first big blast at Climax, a "loop back" (three-wire system) was used (Fig. I), with the idea of securing a wiring system that would give to all series the same amount of current. Single-phase, 60-cycle, 13,800-volt [ ] power was furnished to the blasting transformers, each of which has a rated capacity of 600 amp. at 480 volts. Two blasting leads were taken from these transformers, giving a blasting current of single phase, 60 cycle, 480 volts, with an instantaneous capacity of more than 600 amp. The blasting switch was on the secondary leads from the transformers, to avoid lag in energizing them.

Jan 1, 1938

By Thomas E. Howard

Recipient of the 1975 D. C. Jackling Award - "For his vision and initiative in defining, planning, directing, and accomplishing mining research programs; for his leadership in focusing worldwide attention on the need for research to improve underground excavation for mining and civil applications; and for his lecture. . ."

Jan 1, 1976