Search Documents

By J. Downie, H. A. Kendall, G. H. F. Gardner

Some cases of the motion of two miscible fluids in uniform linear models are discussed. There is no bulk flow through the models, and the convection currents are caused solely by density gradients. Horizontal, vertical and inclined positions of the models are treated separately. Analytical formulas for the motion of a narrow transition zone between the fluids are obtained and compared with measurements, and the limitations are discussed. Observations of the ultimate stabilizing effect of diffusion on the motion me compared with the theory. It is shown that fluid motion in an inclined model with a constant rate of bulk flow can be directly deduced from the cases discussed, provided the viscosity ratio is small. INTRODUCTION In some reservoirs, convection currents caused by variations in the fluid densities may be significant. For practical purposes it may be desirable either to minimize the effect, particularly in miscible displacement, or to maximize the effect as in some schemes for the production of heavy crude oils by combustion. Experiments by Craig, et al,l have shown the effectiveness of gravity in reducing the efficiency of a miscible displacement when the mixed zone between the displacing and displaced fluids is narrow compared with the height of the system. The presence of a board transition zone from one fluid to the other has been shown by Perkins, et al,2 to nullify considerably the influence of a difference in density. Indeed, the theoretical discussion given by Perrine3 has shown that when the transition zone exceeds a certain critical length the efficiency approaches 100 per cent. Many additional results 495 have been published on miscible and immiscible displacements which show the importance of density difference and also mobility ratio. The aim of the present paper is to discuss some cases of gravity segregation of miscible fluids in linear models such as are often used in the laboratory to evaluate recovery processes, and to supply additional experimental evidence in support of the conclusions. An attempt is made to calculate simply the magnitude of the fluid motion caused by density pdients and mobility ratios, and to quantify the modifications in the fluid motion produced by the combined effect of molecular and convective dispersion. However, it should be pointed out that the uniform permeability of the models and the use of only a single pair of fluids (whereas several pairs of fluids may be employed in a recovery scheme) severely restricts direct conclusions about natural reservoirs. For conciseness, the motion generated by density gradients is emphasized for the case of no bulk flow through the models. This is not a drastic limitation because, as shown in Appendix A, a fluid motion with a constant bulk flow through any linear model is equivalent to a fluid motion with no bulk flow in the same model inclined at a different angle to the horizontal, provided only that the density is a linear function of the viscosity of the fluid mixture. HORIZONTAL MODEL In this case the model is assumed to have a rectangular cross-section with a horizontal breadth b, vertical height and a great length L. Throughout.the paper it will be assumed that x-axis points along the length, the y-axis along the width and the z-axis along the height. Thus, in the present case the x, y plane is horizontal. Initially, the transition zone between the fluids is assumed to be thin and parallel to the y, z plane. An example of this situation in a practical problem arises in a scheme for using air for cushion gas in the storage of fuel gas in aquifers. 6 With the passage of time the denser fluid sinks and spreads along the bottom of the model while the lighter fluid rises. The interface extends from the top plane of the model to the bottom. Experiments have shown that for practical purposes this interface may be treated as a plane surface at all times. The surface is significantly curved, however, for viscosity ratios greater than about 10. Other complications arise with large viscosity ratios because of the nonlinear dependence of the viscosity on the composition of the mixture, so that the simple results given here are restricted to fairly low viscosity ratios.

By T. J. Neil, C. B. Manula, O&apos

This paper describes a simulation model developed to analyze truck haulage problems as they are found in the open pit mining and construction industries. The model, using a computer, cycles trucks between their assigned loading and discharge points over a measured haulage route. Required parameters for model operation include the number and type of operating trucks and loading units, maximum truck acceleration and velocity, a realistic vehicular deceleration rate, and the ratio of ore to total material loaded at each origin. Equipment performance characteristics, system profile characteristics, and service time distributions are also included. Records are kept of all waiting times at the loading and discharge points and of any truck interference on the haulroads (moving queues), and a current journal of ore and waste production is maintained. In the pursuit of reduced truck haulage costs, management is confronted with three particular problems in truck and shovel mines. 1) What is the best assignment of trucks to shovels in the system? 2) If new equipment is needed, which new shovels and trucks will operate most effectively in the system? 3) Are any physical changes in the haulage layout warranted to increase productivity? For small open-pit mines the answers to these questions may be obvious. However, for larger operations complex problems are encountered with production and system configuration relationships usually being unknown. The mining simulator discussed here was developed to aid management in evaluating alternative pit-haulage schemes to reduce the risk involved in the selection and assignment of equipment in open-pit truck and shovel mining systems. There are two fundamental differences between this model and other truck haulage simulators: one is a difference of degree, the other a difference of kind. This model can simulate more complex systems than previous models by allowing transportation of material from multiple mine faces to multiple mine destinations and by being readily adaptable to a wide variety of mine layouts. The second difference that characterizes the model is the standard simulation of truck movements. This technique enables each vehicle to perform according to its mechanical capabilities and the physical profile of the haul road. Among the similarities between other truck haulage simulators and this model are the recognition of the probabilistic nature of certain service times in the system and the use of a digital computer to operate the model. The computer inherits the staggering computational and bookkeeping work loads and provides a means for compressing the time scale by allowing several days' operations to be simulated in a matter of minutes. DISTRIBUTION SYSTEM Basic aspects of the system analyzed here may be brought into focus by referring to Fig. 1, a schematic of the typical open pit truck-shovel operation programmed into the simulation model. A single stage materials handling scheme is employed to transport both ore and waste. Loaded trucks are directed to a crusher or stockpile if ore is being mined, while overburden is conveyed to a waste dump. Each shovel has a given number of assigned trucks and has two associated haulage routes, one for waste and one for ore. Up to 5 shovels and as many as 10 trucks per shovel (or a total of 50 trucks) can be operated in the model. Essentially the model, using a computer, cycles trucks between their assigned shovels and the proper discharge points over measured haulage routes. Required input parameters for model operation include the number of shifts to be simulated, operating time per shift, number and type of operating trucks and shovels, maximum truck acceleration and velocity, a realistic vehicular deceleration rate, and the ratio of ore to total material loaded at each shovel. Equipment performance characteristics, system profile characteristics, and service time distributions are

Jan 1, 1968

By R. S. Busk, E. G. Bobalek

THE relation between gases and metals has been a subject of increasingly active investigation during the past years, principally devoted to the study of metal-hydrogen systems. It has been found that hydrogen is soluble in most molten metals to an appreciable extent and somewhat soluble in most solid metals.1,2 In every known case there is a sudden decrease in solubility at the melting point. Thus a freezing mass of metal containing hydrogen in excess of the solid solubility must in some way expel that excess during the freezing process. This leads to internal blowholes, and such effects as pinhole porosity. Gas trapped in metal that is to be fabricated by a working process such as extrusion or rolling may be the cause of blisters. For some cases, notably in copper and iron alloys, the presence of hydrogen can lead to extreme embrittlement of the metal. The aluminum-casting industry has long recognized the importance of hydrogen in its techniques. Excess gas in molten aluminum alloys often leads to the formation of "pinhole porosity" in the solid casting.3 To prevent this hydrogen pickup it is necessary to avoid overheating the melt and to protect it from such sources of hydrogen as water. In spite of all precautions, it is sometimes necessary to extract hydrogen from the melt just before pouring by bubbling with a gas such as chlorine or nitrogen. Recently it has been found that somewhat similar effects are possible with magnesium alloys, in that the presence of hydrogen can induce or aggravate microporosity.4-6 This paper is primarily concerned with a presentation of some facts concerning the solubility of hydrogen in magnesium and its alloys, with some discussion of the significance of these facts in a practical sense. In any study of gas-metal systems it is important to bear in mind a clear distinction between adsorption on surfaces and absorption within the lattice.1 Considerable attention has been directed toward determining whether hydrogen is truly soluble in any solid metal, or whether the gas extracted from a sample was present at surfaces (external and internal) only.7 Most present day evidence supports the idea of true solution in addition to adsorption. A second important factor when dealing with gas solubility is the dependence of such solubility on external pressure. For diatomic gases such as H2, solubility in both liquid and solid metals apparently is proportional to the square root of the pressure, indicating a breakdown to a monatomic gas before diffusion into the lattice .2 For true equilibrium values of solubility, therefore, the pressure at the metal surface must be constant and, preferably, known. Very little has been published concerning the hydrogen-magnesium system. Winterhager has presented the most

Jan 1, 1946

By Robert Bell

The Tar-Sands" is the name which has been given to the extensive horizontal deposit of fine Cretaceous sand, blackened by tarry petroleum, which forms the banks of the last or lowest 130 miles of' the Athabasca river before it terminates in Athabasca lake. The Cretaceous strata, to which these sands belong, extend northwesterly from Dakota all the way to this lake and for 500 miles beyond it. The Athabasca river forms the uppermost section of the Athabasca-Mackenzie, one of the great rivers of the world. It rises on the Pacific side of the Rocky mountains, westward of Edmonton, and flows north of east to a point called Atha-basca Landing, 100 miles north of Edmonton, where it turns northward and runs about 280 miles before it falls into the west end of Athabasca lake. The section of this river-system which discharges the lake just named into Great Slave lake, is called Slave river, and below the latter lake it becomes the Mackenzie river. Along the section of 280 miles of the Athabasca river above mentioned, the Cretaceous strata consist of bluish-gray and drab-gray marls, on top, from Athabasca Landing to Drowned rapid, 110 miles down stream; then heavily bedded gray sandstones, 225 ft. in greatest thickness, underlying these, form the banks for about 40 miles further. The strata appear to be horizontal, but they really dip very slightly to the southward. At Drowned rapid, we see the first of the tar-sands resting on almost horizontal beds of bluish-gray limestone of Devonian age. In some places the limestone is associated with shaly or marly bands. Notwithstanding the great hiatus between the two series, the horizontal tar-sands lie conformably upon the almost level upper beds of the limestone wherever the two formations are seen together, all along the river, throughout a

Jan 1, 1908

By R. S. Archer

THE binary aluminum-silicon alloys have certain characteristic advantages which are now well known, and these alloys have come into considerable use during the past several years.1 Their field of application has been limited to a certain extent, however, by their low yield point and hardness, low endurance limit, and relatively poor machining characteristics. These properties are improved by the addition of copper, and the ternary aluminum-silicon-copper alloys constitute an important class. The addition of copper decreases the corrosion resistance of the aluminum-silicon alloys and increases specific gravity. Magnesium is a hardening addition which seems to have relatively little effect on corrosion resistance, and which, of course, reduces specific gravity. The object of the work described in this paper was the development of alloys and heat treatments for the production of sand castings and permanent-mold castings having substantially all the advantages of the binary aluminum-silicon alloys together with mechanical properties improved to a degree permitting wider application.

Jan 1, 1930

By Dirk A. Benham, William A. Warfield

INTRODUCTION Whenever a mine operator is faced with a decision between various mining methods or even equipment selection, he must be assured that his decision will have a positive effect on his economic operating goals. For instance, if a mine operator has a choice of using an LHD mining system or a slusher mining system, then his decision to use either must not only fit within the operational limitations of the mining plan (such as production requirements, physical features of the ore body, mine plant facilities, manpower requirements, etc.), but also assure that the ore is being extracted at the least possible cost. To aid in his decision making process, the operator will commonly compare acquisition costs, operating costs, maintenance costs, and the operational advantages and disadvantages of each system in addition to considering his personal observations and feelings. A decision to select a mining system using only those criteria aforementioned will not necessarily lead the operator down the path to maximizing profits. In addition, the operator should also compare the economic effects of each system upon the overall mining operation. A relatively simple method for determining the economic effects is to calculate and compare the break-even grades for each system under consideration. By implementing such an analysis, the operator can now select a mining system which can operate within the limits of the mining plan as well as extract the ores at the least possible cost, thus yielding maximum profits. This paper will present the geologic and physical conditions of a mine being operated by the Hypothetical Mining Company in the Grants Mineral District. An LHD and Blusher mining system are under consideration and are compared by examining operating costs, equipment availability, and the conventional operational advantages and disadvantages of each. Finally, the economic effects of each system upon the overall mine's operation are compared by utilizing break-even grade analysis. DESCRIPTION AND MINING METHODS The Hypothetical Mining Company has located an ore body in the Grants Mineral District. After extensive surface exploration drilling and cost considerations are evaluated, it is decided to open a mine. The following tasks must now be performed: 1. outline ore body and it's basic characteristics, 2. look at mining methods currently in use in the area, and 3. determine mining techniques and methods for exploitation of the ore body. For the sake of argument, the newly discovered ore body is located towards the western edge of the Grants Mineral Belt. The host rock for uranium mineralization is the Westwater Member of the Morrison Formation. The Westwater Canyon sands are overlain by the Brushy Basin Member of the Morrison Formation and underlain by the Recapture Member, all of Jurassic Age. Westwater Canyon sandstone is a fine to very course grained subarkosic sand with interbedded green and red mudstone. The Brushy Basin Member consists predominantly of greenish-gray mudstones and contains thin lenses of sandstone and a few thin beds of limestone. The Recapture Member consists of alternating thin beds of reddish brown, grayish red, and light gray sandstone and siltstone. The Recapture interfingers with the Cowsprings Sandstone in the area of the mine. The mineralization is based on the groundwater flow within the Morrison Formation. Primary ore distribution is based on three basic parameters: ore migration in a geochemical cell, lenticular mudstone interbedding, and enrichment along fault zones. In areas where two fault systems intersect, ore thicknesses of up to 30 m (100 ft.) are encountered. In those areas where the ore is well defined and thicknesses facilitate full face mining, the mining methods are determined more by ground or operating conditions, equipment availability, and access to working areas than they are in the fringe areas of the ore body where grade control is more important and split-shooting and break-even grade determines the mining technique. If a modified room-and-pillar mining method using systematic development is selected, better control of the ventilation, equipment utilization, and mining plan can be obtained. Figure I shows a typical mining area where the ore is thick,

Jan 1, 1982

By F. W. Lee

Historical-From the beginning of time, all ingenuity of mankind has been concentrated upon the methods of finding gold and unusual deposits in the earth. An illustration (Fig. 1) from the old treatise by Agricola, "De Re Metallica," published in 1580, will serve to show the im-plicit faith of that generation in divining methods. However, it was not until 1920 that real progress was made in prospecting by using the latest advances of the physical sciences. The public interest was stimulated by the successes of these methods on the part of commercial oper-ators, and governmental agencies received many requests for information concerning their relia-bility. There were also, in the late 1920's.high- pressure mine-promotion schemes which used geophysical methods in a very questionable manner, symbolized in Figure 2 as of 1928 by an elec-trified forked stick. Authoritative information concerning such practices for public protection was needed to curb such notorious undertakings. Dr. Scott Turner, then Director of the United States Bureau of Mines, thoroughly understood the situation and was first in the governmental de-partments to recognize the possible value of a study of modern prospecting methods. The Bureau of Mines began this investigation by employing Drs. A. S. Eve and D. A. Keys of McGill University for short periods in the summer in 1927. Their first publication [see 1 of "References" at end of paper] served to illustrate the fundamental scientific principles which underlie geophysical prospecting. This was followed by a second publication [21 giving the results of field-tests. In the light of the rapid improvements during the intervening ten years, these two papers take a historical position. Later a full-time position under Civil Service was planned by the Bureau of Mines for con-tinuous investigations and research concerning geophysics and its applications to prospecting. It was Turner's idea that. since the oil-industry had been making very rapid progress with good results, if mineral mining could also benefit to the same degree, it would be of great help to that industry.

Jan 1, 1940

By John F. Blandy

IT is not my intention in this article to consider this subject in the light of the geographer or geologist, but rather in that of the mining engineer, and to endeavor to show the necessity and value to him of studying the minor details of the field or district in which he may be engaged. I t has been said by a distinguished geologist that "the natural boundaries of the geographer are rarely described by right lines. Whenever they occur, however, the geologist may look for something remarkable." And again : " Physiognomy is no idle or doubtful science in connection with geology. The physiognomy of a country indicates almost invariably its geological character." Our country furnishes examples enough of the truth of these remarks, and in no part of it is it so beautifully illustrated as in our own State, which has been so ably described by Prof. Lesley in his admirable little work on the "Topography of Coal." As the great mountain lines become guides to the geologist in determining and mapping out the geography of the formations, so do the minor details of topography become guides to the mining engineer in conducting his explorations, discovering of dislocations, and determining the character of the deposits which are the object of his search. I t is therefore requisite that he should, whilst making his surveys, pay the strictest attention to every variation of the landscape and surface of the ground. Until he has mapped out every feature he may be unable to read the geological changes which may have

By AIME AIME

The following persons have been proposed for election as members or associates of the Institute during the period, March 16 to May 1, 1907. Their names are published for the information of members and associates, from whom the Committee on Membership earnestly invites confidential communications, favorable or unfavorable, concerning these candidates. A sufficient period (varying in the discretion of the Committee, according to the residence of the candidate) will be allowed for the reception of such communications, before any action upon these names by the Committee. After the lapse of this period, the Committee will recommend action by the Council, which has the power of final election. The names of candidates were formerly published in the various circulars of the Institute, issued from time to time to the members. Hereafter, they will appear regularly in the Bi-Monthly Bulletin, each number of which will contain the names received since the issue of the preceding Bulletin.

May 1, 1907

By Frederic P. Dewey

By the old method of determining platinum in ores and bullion, the silver-alloy first obtained in the regular course of assay is parted in strong sulphuric acid and the residual metal weighed. This is re-alloyed with silver by a second cupellation and parted in nitric acid, the residual metal being again weighed. Any difference shown between the two weighings is assumed to be, and is called, platinum. Sometimes it is SO, and if any considerable amount of platinum be present, there will be a decided difference between the two weighings; but a slight difference is no real evidence whatever of the presence of platinum. On the other hand, the second weight may equal or possibly exceed the first, even when traces of platinum are present. Again, other members of the platinum group may go into solution in nitric acid more or less. If present, these would be called platinum and escape detection. The method does not provide any direct tests whatever as to the presence or absence of platinum. It is often indecisive, and sometimes gives erroneous results. It is, therefore, quite unsatisfactory. Being called upon many times to determine platinum in a wide variety of materials, particularly when present in very small amounts, I have realized the disadvantages and defects of this old method. In an article on the solubility of gold in nitric acid,' I have briefly outlined a method of gathering a little gold out of a solution containing much silver, which furnishes the basis of

Jan 1, 1913

By E. Martinez, M. L. Hollander

Sulfurization of copper oxides was investigated using differential thermal analysis (DTA) and thermal gravimetric analysis (TGA). When mixtures of cuprous oxide and sulfur were heated, the surface of the cuprous oxide was converted to cupric sulfide at the melting point of sulfur (119°C); additional sulfuriza-tion took place when the sulfur vaporized above 200°C. Cupric oxide also reacted with sulfur to form cupric sulfide but the starting temperature was approximtely 225°C. When the cupric oxide and sulfur were physically separated, sulfurization still occurred indicating a reaction with the vapor phase of sulfur. Sulfurization was obtained in runs with cuprite, chrysocolla and basic copper carbonate. Further decomposition of cupric to cuprous sulfide was noted at somewhat higher temperatures. The DTA-TGA data made it possible to set up postulated reactions in each system. These techniques were found to be well suited for studies of this type. Because of the difficulty encountered in flotation of many metallic oxide minerals, efforts have been made to find suitable reagent combinations to sulfi-dize these minerals in the flotation circuit. Recently Bautista and Sollenberger,1 using a different approach, showed that the surfaces of many oxide minerals can be converted to sulfides by heating them with sulfur to temperatures between 150° and 225°C. This technique was effective even with chrysocolla, a mineral which is very difficult to sulfidize. The primary objective of the present study was to obtain information on the reactions between the oxide minerals and suIfur. A better understanding of the mechanisms involved might prove useful in pointing the way to improvements in the process. A secondary objective was to demonstrate the value of thermo-analysis in investigations of this type. Bollin and Kerr2 have reported the use of a modification of differential thermal analysis to study the thermal reactions which occur on heating elemental constituents in a closed system to synthesize copper sulfides and iron sulfides. Differential thermal analysis (DTA) was used to detect enthalpic changes as mixtures of minerals and sulfur were heated. The DTA indicated the temperatures at which reactions started and whether they were exothermic or endothermic. Weight change data were obtained by thermal gravimetric analysis (TGA). These data could often be used to support postulated reactions and to eliminate consideration of other possible reactions. EQUlPMENT Differential thermal analysis (DTA) involves measuring the temperature difference between the sample being tested and a thermally inert reference, generally aluminum oxide, as both are heated at a uniform rate. Series connected thermocouples in the sample and reference are used to detect the temperature differences that occur as the sample undergoes enthalpic changes.3 Crystalline transitions, fusions, vaporizations, dehydrations, decompositions and many solid state reactions can be detected. A DTA unit manufactured by the Robert L. Stone Co., Austin, Tex., was used in this investigation with a temperature rate increase of 10°C per min. The samples and reference were placed in Inconel cups with wells in the bottom into which the differential thermocouples fit, and run in a nitrogen atmosphere. Thermal gravimetric analysis (TGA) measures the changes in weight that a sample undergoes as it is heated. A Chevenard thermobalance converted electronically for graphic recording was used with a heating rate of 5°C per minute. An X-Y recorder plotted temperature on the X axis and weight changes on the Y axis. A flow of 250 ml per min of nitrogen was streamed through the furnace. Samples were placed in a porcelain crucible open at the top, unless otherwise noted. EXPERIMENTAL RESULTS Sulfur: Two sulfur samples from different sources were tested. The DTA of a high purity sulfur and a reagent grade sublimed sulfur are shown in Fig. 1. Nearly all the tests were run with the sublimed sulfur due to the difficulty in grinding and high electrostatic charge encountered with the high purity sample. Sulfur undergoes three endothermal reactions below 200°C. The first is a solid-solid crystalline transi-

Jan 1, 1964

By C. R. McEwen

This paper presents a technique for calculating the original amount of hydrocarbon in place in a petroleum reservoir, and for determining the constants characterizing the aquifer performance, based on pressure-production data. A method for doing this based on a least-squares line-fitting computationwus proposed by vanEverdingen,Timmerman andMcMahon in 1953. We found that their method would not work when there is error in the reservoir pressure data — even moderate error. The technique presented here appears to give reasonable answers when pressure data are uncertain to the degree expected in reservoir pressure determinations. The major change introduced in the present analysis is to limit the least-squares line-fitting to yield only one constant— the amount of hydrocarbon in place. The water-influx constant is then taken as proportional to the oil (or gas) in place. The constant of proportionality can be computed from estimates of effective compressibility and reservoir water saturation. It is also pointed out that the commonly used least-squares analysis assumes all of the uncertainty to be in the dependent variable. The material balance should be arranged so that this condition is fulfilled if correct inferences are to be made from statistical calculations. Examples are shown of the application of the new technique to gas reservoirs—both hypothetical and real—and to the oil-reservoir example of van Ever-dingen, Timmerman and McMahon. INTRODUCTION The amount of hydrocarbon originally in place in a petroleum resenroir can be estimated by means of the material-balance calculation. Simultaneous observations of pressure and amounts of produced fluids are required, together with the PVT data applicable to the reservoir fluids. If water encroachment is occurring, it is desirable to try to infer the behavior of the aquifer, as well as the original hydrocarbon in place, from the pressure-production data. This imposes additional demands on the method of calculation, and uncertainty in the data can result in large uncertainty in the answer. In addition, if the size of a gas cap is to be established, the whole problem becomes indeterminate, as pointed out by Woods and Muskat.1 Brownscombe and Collins2 simulated a gas reservoir and its aquifer on a reservoir analyzer and derived quantitative information on the effect of uncertainty in pressure and aquifer permeability on computed gas in place. Among the various techniques of estimating the performance of an aquifer, the method of van Ever-dingen and Hurst? based on compressible flow theory, seems to have been the most generally successful (see Ref. 4, for example). In this paper we shall confine ourselves to their representation of the aquifer. In 1953,' van Everdingen, Timmerman and McMahon5 introduced a statistical technique for deriving the amount of oil originally in place and the parameters which describe the aquifer. (We shall refer to this technique as the "VTM method'', as suggested by Mueller.6) Their example reservoir had no gas cap. It has been our experience that the VTM method gives a reasonable answer when the data are very accurate, but that inaccuracy (particularly in pressure) can cause the method to break down. The effect was first observed in gas reservoirs, but has since been seen in oil reservoirs also. In this paper we present another statistical method which has been successful in achieving a reasonable answer where the VTM method has failed. In the new method, one less parameter is derived from material-balance computations. It is assumed that values can be established for effective compressibility in the aquifer and reservoir water saturation independently of the material-balance calculation. The water-influx constant can then be obtained from these data and the quantity of hydrocarbon in place.

By L. C. Armstrong

A. E. ROSS*—Mr. Armstrong in his paper stated that they had experienced considerable difficulty in drilling the quartz-feldspar intergrowths. The dia-mor~d loss was excessive and the diamond bits polished quite rapidly. Mr. Davidson, who presented the paper, stated that bortx stones in the range of 20 to 30 per carat had been used in the bits on this job. I would like to suggest the use of bits employing stones in the range of 60 to 100 per carat, an average of possibly 80 per carat. If these stones had been used the bits might have lasted longer and not polished so quickly. As a basis for this suggestion I would like to point out that in northern New York State we had at least two examples where bits employing stones in the range of 80 per carat had solved a difficult problem. Bits set with stones in the range of 20 to 30 per carat had been used previously and had failed. With the finer stones, the cost per foot of drilling decreased material1y. It should also be noted from a technical standpoint that the smaller stones require higher drilling speeds than the larger stones. Greater pressures are not normally necessary, and it is the higher speed which seems to be the major factor of importance. It should also be noted that the finer stones afford a greater number or cutting surfaces for the same carat weight in a bit. Then too, the smaller stones, by virtue of their size, serve as sharper cutting edges than larger stones. There is no doubt that the diamond bit employing smaller stones costs more to set than the bit using larger stones. However, with the technique developed at the shops of Sprague and Henwood, Inc., we feel that the relatively slight additional cost required to set these bits is more than paid for by the resultant lower drilling cost. We feel that the highest quality stone available is the most economical to use when hard fine grained rock is encountered. In summary, I would suggest that it might be possible to solve the problem presented in this paper by using a diamond bit employing stones at least as small as 80 per carat of the highest grade possible and by using the diamond bit at the highest speed available with modern drilling equipment. L. C. ARMSTRONG (author's reply) —It is generally agreed that the use of smaller, high-grade diamonds and of higher drilling speeds, as suggested by Mr. Ross, may be the best approach to the solution of the problem.

Jan 1, 1950

By E. S. Machlin, C. W. Chen

RECENTLY Chen and Machlin' proposed a mechanism for intercrystalline cracking in metals during high-temperature stressing. According to this mechanism the formation of voids at grain boundaries is primarily responsible for intercrystalline cracking. A model has been provided to demonstrate the initiation of submicroscopic cracks and voids at jogs of grain boundaries where grain boundary sliding is inhibited. Submicroscopic cracks can grow as a result of either further grain boundary sliding or localized tensile stress. In the former case, it is believed that grain boundary sliding produces more voids which link together to produce macroscopic cracks and which may lead to the eventual failure of the metal. Concurrently, Nield and Quarrell2 reported their interesting results obtained in a systematic investigation of intercrystalline cracking in two aluminum alloys under various creep conditions. Their observations are generally in agreement with the above mechanism, especially the conclusion that voids are formed as a direct consequence of grain boundary sliding. On the basis of the volume fraction occupied by voids, they could find no confirmation of vacancy condensation as the mechanism for void growth. Furthermore, an important feature of intercrystalline cracking has been likewise pointed out by them that the majority of cracks are not formed at grain corners. Nield and Quarrel1 meanwhile emphasized the importance of grain boundary migration by designating it as one of two main processes operative in the mechanism of crack formation during creep. The designation seems unnecessary because overemphasis of grain boundary migration only complicates the mechanism of void formation. There are two reasons which militate against the inclusion of grain boundary migration in the mechanism of void formation. In the first place, the formation of intercrystalline voids per se does not require grain boundary migration. Secondly, in addition to grain boundary migration, void formation may be minimized by any other process such as plastic deformation which is capable of relieving localized stresses around jogs. Chang and Grant3 have shown that intercrystalline cracking is prevented in aluminum by lattice bending in high stress regions. The influential role played by grain boundary migration in creep has also been realized in our studies. In several cases, voids did not appear at all in grain boundaries whenever grain boundary migration took place prominently during creep. The purpose of this paper is to discuss the effect of grain boundary migration on the formation of intercrystalline voids and other related rupture properties. Experimental evidence indicates that in an unstable grain structure void formation may be markedly modified by structural changes. The abnormally high ductility and the transcrystalline mode of fracture observed in copper at elevated temperatures reveals that effective grain boundary migration minimizes void formation. Grain boundary migration has long been known as a common high-temperature phenomenon in metals with the grain configuration in a nonequilibrium state. Its effect on ductility and mode of fracture has not been recognized until recently.4 Since the introduction of the term "Equicohesive Temperature," the conventional belief has been that below the equicohesive temperature the ductility of metals increases moderately with decreasing temperature until the ductile-to-brittle transition temperature of fracture is reached. In this temperature range, metals fracture in a ductile mode with a "cup-and-cone" fracture surface. Above the equicohesive temperature, ductility remains invariably low and decreases slightly with increasing temperature. The mode of fracture is strictly brittle and intercrystalline. Typical examples have been shown for a brass and copper in Fig. 1 and 9, respectively, in the paper by Greenwood, Miller, and Suiter.5 The observation in the upper temperature range that ductility of metals is low and insensitive to temperature may be explained in terms of void formation at grain boundaries. It is also in accordance with the findings of McLean6 and Fazen, Sherby, and Dorn7

Jan 1, 1961

By J. D. Doherty

That America's great coal deposits eventually will be our principal source of liquid as well as solid fuels is generally accepted. Moreover, the day when synthetic oil from coal will begin to supplement our petroleum supplies does not appear to be far off. The American petroleum industry has not spared effort or expenditure in its attempt to keep pace with the demand for oil, and recent production has exceeded expectations. However, the rapidly rising demand for liquid fuels plus the increasing difficulty of finding and developing the new oil needed even to maintain present production rates make it highly unlikely that oil from domestic wells can fully meet future oil requirements. Therefore, it appears that one or more of the following courses must be followed: 1. Curtail oil consumption. 2. Incr ase imports. 3. Develop new sources such as synthetic liquid fuels. All three courses may well be needed, as it is doubtful that any one of the three alternatives alone can satisfactorily solve the problem indicated by the prevailing trend in demand for oil. Curtailment of oil consumption is not a constructive policy, except where oil is being wasted or coal can be readily substituted as in stationary steam plants. Reduced oil supplies for most uses will curb our economic advancement and, in addition to inconveniencing consumers, will have a pronounced adverse effect on American industry. The oil-burner-manufacturing industry already has been dealt a hard blow. Shipments in the first 5 months of 1948 decreased 70 pct from those in the same period in 1947.1 The effect of a similar cut in the automobile industry can be imagined. A severe prolonged shortage of gasoline could seriously disturb our present economic well-being. It might be pointed out also that even the prospect of a shortage or lack of assurance for the future can discourage buyers of equipment, as occurred in the case of oil burners. An increase in our imports of oil seems to be a necessary expedient for the immediate future. Its advantages are that it will require a minimum of manpower and steel in a time of critical shortages and will conserve domestic reserves. Any major dependence upon foreign sources for our oil supplies should be avoided, however. Other nations are increasing their oil consumption more rapidly percentagewise than the United States and eventually will compete with us for the not unlimited world supplies. In peacetime, foreign countries might restrict ship- ments of oil to this country or impose exhorbitant prices. In the event of war, there is serious danger that such sources would be cut off, and American-developed oil fields overseas might even be used against us. Although synthetic fuels cannot relieve any oil shortage that might develop within the next year or two, an immediate start toward a substantial synthetics industry to supplement petroleum not only could help relieve shortages several years hence but also would help establish the much needed "know-how" for large-scale production. By assuring ample future supplies, such a start would permit sound planning by industries dependent upon oil and maintain or restore the confidence of prospective customers for oil-con-suming equipment. If it is agreed that domestic production of crude oil cannot be expected to meet future domestic demands, that oil rationing in general is undesirable. and that too great dependence on foreign oil should be avoided—and the weight of the evidence supports such conclusions—it is inescapable that commercial synthetic fuel production should be developed to supplement domestic petroleum supplies, which, of course, will furnish the bulk of our requirements for yean to come. Sources of Synthetic Oil The three principal sources of synthetic oil are natural gas, oil shale, and coal. A commercial plant using natural gas is under construction, and expansion of this industry is expected.

Jan 1, 1950

HAVING told you of the practices of the arts involving other metals, I wish to tell you also of the practice of that of tin.* Indeed, since this is an easily melted metal, in common use for the utensils which are made for human needs, it is an art known not only to skilled men but also almost to children, wherefore I could proceed with- out telling of it. However, besides the production of plates and bowls and many other dishes for eating from and keeping things in, this embraces two other arts, both of which you should know about because they are useful and beautifid. One of these is the art .of making the letters with which books are printed, and the other is that of making the sheets from which organ pipes are built. The vessels, as perhaps you have seen, are cast one by one in moulds made of white tuff. Several pieces fastened together are then put on the iron axle of a wheel rotated by hand, and [138v] they are turned with a slightly bent tool which has a cutting edge. In this way they are made thin and of a good shape. Then they are polished with a piece of linen cloth and a little powdered tripoli, and thus they are finished. The letters for printing books are made of a composition of three parts of fine tin, an eighth part of black lead, and another eighth part of fused marcasite of antimony.t The desired quantities of these metals are melted

Jan 1, 1942

By Leslie W. Austen

ROTARY kiln operators will agree that some of the most severe conditions a refractory must stand occur in the hot zone of a kiln burning Portland cement, dead burn dolomite, magnesite, peri-clase, and similar materials. Frequently the operator is faced with factors beyond his control which drastically shorten the life of refractories. Shutdown due to mechanical failure can be serious if the period is of sufficiently long duration to cause the dropping of coating or the loosening of the lining. A change in slurry can affect the coating and cause ring buildup. A change in type of fuel and its effect upon the flame can cause a shift in location of the hottest zone. Weekend shutdowns or any other interruption can cause the operator trouble and may damage the refractories, since stopping and starting a rotary kiln is certainly more difficult than stopping and starting a motor. Some operators have tried to set an estimate of damage for each shutdown in equivalent days of running time. Conditions affecting the refractory may be roughly grouped in four classes: chemical attack, mechanical stress, thermal shock, and abrasion. Chemical Attack: The drive to obtain maximum production through a kiln demands maximum operating temperatures, temperatures which are limited more by the ringing up or melting of the clinker. This can cause interface temperatures at the junction of coating and refractory which require the use of a basic kiln block to withstand the chemical attack. Chemical changes take place within the refractory itself, especially in chemically bonded or unburned kiln blocks. These changes cause the formation of the ceramic or burned bond. Migrating liquids or fluxes from the kiln charge have an effect within the refractory and lead to mineral or glass formation. The alkalies, sodium and potassium, migrate into the refractory as silicates, chlorides, sulphates or other salts. They may move under capillary action or may be caused to move by volatilization with condensation in the cooler portion. Mechanical Stress: Concentrated stress may be caused by several factors or combinations thereof. I—The rings of refractories must be kept tight and rigid within the kiln, and this alone demands considerable force to hold the blocks in place. So that the force will not be concentrated, the blocks should fit the circle as perfectly as possible, with the faces in contact overall. 2—As the kiln is heated, thermal expansion takes place at the hot end of the kiln block. Since this disturbs the plane face it too can cause a concentrated stress at the two ends of the block, and shearing stress can be set up within the brick itself because of the difference in expansion between the two ends. 3—If a lining becomes loose and moves in the shell very severe stress can be set up, and as the kiln rotates this load changes and gives the effect of repeated loading. Permanent expansion of the refractory can also cause severe loading. 4—Not least important, flexing of the kiln is frequently the cause of concentrated stresses. Thermal Shock: Thermal shock, the result of heating and cooling too rapidly, occurs on starting and stopping or when a large patch of coating drops, exposing the bricks. Again, its destructive effect is often the result of phase change, liquid to solid or the reverse; dense refractories loaded with glass-forming impurities are particularly susceptible. Thermal shock is a. problem with refractories set in the wall or roof of a stationary furnace, and becomes even more serious in a rotary kiln, the tendency to spa11 being magnified with movement and concentration of stress. Uniform rate of feed and loading insures both better coating and a more uniform stress. Abrasion: If the refractories do not take a coating, abrasion can become a most destructive factor. Movement of the lining in shell or movement of loose blocks causes abrasion, which is also most destructive if the refractories do not take a coating. An analysis of the problem of basic lining for the hot zone reveals, therefore, a number of desirable characteristics: high refractoriness, basic chemical reaction, resistance to spalling, good strength at all stages, ability to take coating, true sizing, volume stability, and abrasion resistance. Increased demand

Jan 1, 1953

By Leslie W. Austen

ROTARY kiln operators will agree that some of the most severe conditions a refractory must stand occur in the hot zone of a kiln burning Portland cement, dead burn dolomite, magnesite, peri-clase, and similar materials. Frequently the operator is faced with factors beyond his control which drastically shorten the life of refractories. Shutdown due to mechanical failure can be serious if the period is of sufficiently long duration to cause the dropping of coating or the loosening of the lining. A change in slurry can affect the coating and cause ring buildup. A change in type of fuel and its effect upon the flame can cause a shift in location of the hottest zone. Weekend shutdowns or any other interruption can cause the operator trouble and may damage the refractories, since stopping and starting a rotary kiln is certainly more difficult than stopping and starting a motor. Some operators have tried to set an estimate of damage for each shutdown in equivalent days of running time. Conditions affecting the refractory may be roughly grouped in four classes: chemical attack, mechanical stress, thermal shock, and abrasion. Chemical Attack: The drive to obtain maximum production through a kiln demands maximum operating temperatures, temperatures which are limited more by the ringing up or melting of the clinker. This can cause interface temperatures at the junction of coating and refractory which require the use of a basic kiln block to withstand the chemical attack. Chemical changes take place within the refractory itself, especially in chemically bonded or unburned kiln blocks. These changes cause the formation of the ceramic or burned bond. Migrating liquids or fluxes from the kiln charge have an effect within the refractory and lead to mineral or glass formation. The alkalies, sodium and potassium, migrate into the refractory as silicates, chlorides, sulphates or other salts. They may move under capillary action or may be caused to move by volatilization with condensation in the cooler portion. Mechanical Stress: Concentrated stress may be caused by several factors or combinations thereof. I—The rings of refractories must be kept tight and rigid within the kiln, and this alone demands considerable force to hold the blocks in place. So that the force will not be concentrated, the blocks should fit the circle as perfectly as possible, with the faces in contact overall. 2—As the kiln is heated, thermal expansion takes place at the hot end of the kiln block. Since this disturbs the plane face it too can cause a concentrated stress at the two ends of the block, and shearing stress can be set up within the brick itself because of the difference in expansion between the two ends. 3—If a lining becomes loose and moves in the shell very severe stress can be set up, and as the kiln rotates this load changes and gives the effect of repeated loading. Permanent expansion of the refractory can also cause severe loading. 4—Not least important, flexing of the kiln is frequently the cause of concentrated stresses. Thermal Shock: Thermal shock, the result of heating and cooling too rapidly, occurs on starting and stopping or when a large patch of coating drops, exposing the bricks. Again, its destructive effect is often the result of phase change, liquid to solid or the reverse; dense refractories loaded with glass-forming impurities are particularly susceptible. Thermal shock is a. problem with refractories set in the wall or roof of a stationary furnace, and becomes even more serious in a rotary kiln, the tendency to spa11 being magnified with movement and concentration of stress. Uniform rate of feed and loading insures both better coating and a more uniform stress. Abrasion: If the refractories do not take a coating, abrasion can become a most destructive factor. Movement of the lining in shell or movement of loose blocks causes abrasion, which is also most destructive if the refractories do not take a coating. An analysis of the problem of basic lining for the hot zone reveals, therefore, a number of desirable characteristics: high refractoriness, basic chemical reaction, resistance to spalling, good strength at all stages, ability to take coating, true sizing, volume stability, and abrasion resistance. Increased demand

Jan 1, 1953

Edwin H. MessiteR, New Pork City (communication to the Secretary*):—Under the heading " Flues," Mr. Edwards refers to the Bee-hive construction, a cross-section of which is shown in Fig. 4 of his paper. A flue similar to this was designed by me about six years ago,' in which the walls though much thinner than those described by Mr. Edwards gave entire satisfaction. These walls, from 2.25 in. thick throughout in the smaller flues, to 3.25 in. in the larger, were built by plastering the cement mortar on expanded-metal lath without the use of any forms, or cribs, whatever, at a cost of labor generally less then $1 per sq. yd. of wall. Of course, where plasterers cannot be obtained on reasonable terms, the cement can be molded between wooden forms, though it is difficult to see how it can be done with an interior core only as stated by Mr. Edwards. In regard to the effect of sulphur dioxide and furnace-gases on the cement, I have found that, in certain cases, this is a matter which must be given very careful attention. Where there is sufficient heat to prevent the existence of condensed moisture inside of the flue, there is apparently no action whatever on the cement, but if the concrete is wet, it is rapidly affected by these gases. At points near the furnaces there is generally sufficient heat not only to prevent internal condensation of the aqueous vapor always present in the gases, but also to evaporate water from rain or snow falling on the outside of the flue. Further along, a point is reached where rain-water will percolate through minute cracks caused by expansion and contraction, and reach the interior, even though internal condensation does not occur there in dry weather. From this point to the end of the flue the roof must be coated on the outside with asphalt paint or other impervious material. In very long flues a point may be reached where moisture will condense on the inside of the malls in cold weather. From this point to

Jan 1, 1905

The Library of the above-named Societies is open from 9 A. M. to 10 P.M., except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information, will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will he sent more promptly and in more usable shape.

Jan 8, 1917