Search Documents

By B. W. Gandrud, R. G. Meara, O&apos

In 1034 the Southern Experiment Station of the U.S. Bureau of Mines in cooperation with the University of Alabama began an investigation of the availability of kyanite ores as a source of raw material for the manufacture of refractories. Under this program, gravity concentration and flotation tests have been made on two varieties of Georgia kyariite ore, mica schist and massive. Most of the attention has been directed to the mica schist ores, as they are more widely distributed and seem to offer greater economic possibilities than the massive ores. It is evident that the preparation of kyanite for use as a refractory material involves other considerations than the mere elimination of impurities. A concentration process that eliminates impurities satisfactorily may have to be followed by some additional treatment, since the final product must be of a coarseness and size ratio that will make it suitable for refractories manufacture. So far in the investigation at the Southern Experiment Station of the U.S. Bureau of Mines only the concentration problem has been considered, and this paper is intended as an interim report. Ores The schist ores contain 1 to 9 per cent of kyanite crystals embedded in mica and quartz, with smaller amounts of graphite, garnet and iron oxide and minor amounts of other heavy minerals. The garnet content varies from a trace to a few per cent. The minerals are easily released by moderate grinding. The size of the kyanite ranges from fine needles to crystals 1 1/2 in. long, 1/2 in. wide and 1/4 in. thick. The garnet, quartz and iron oxide grains have a smaller mean mesh than most of the kyanite. The maximum size of the garnet crystals corresponds to about 14 mesh and that of the sand grains is considerably less. Most of the iron oxide is still finer, for the minus 100-mesh size is greatly enriched in Fe²O3. The massive ore consists of radiating masses of kyanite interlocked with quartz, mica, corundum and small amounts of other heavy minerals.

Jan 1, 1938

By Alexander Field

IN THE light of the experimental data on equilibrium for the reaction C + FeO = Fe + CO in molten steel recently obtained by Kinzel and I Egan,1 it is necessary to revise current theories regarding the nature of equilibrium between carbon and FeO in the basic open-hearth furnace. According to the measurements of these investigators the equilibrium constant m for the above reaction for a pressure of dissolved CO equal to 1 atm. is equal to 0.0005 at 1550° C., when concentrations of carbon and. FeO are expressed in percentages by weight. Their work also shows that, with the pressure of CO fixed at 1 atm., not only is the product of carbon and FeO constant, but carbon and FeO are each independently constant-a circumstance which might have been predicted from theoretical considerations. At 1550° C., carbon is constant at about 0.025 per cent. and FeO at about 0.020 per cent., with the pressure of dissolved -CO equal to 1 atm., the product of these two constants being equal to the originally mentioned constant of 0.0005. Available data on the dissolved FeO content of samples taken from the metal bath at practical slag-metal equilibrium prove that this FeO content is determined solely by temperature and the effective FeO content of the slag. The distribution constant r at 1550° C., as determined by Herty, Gaines, Larsen, Simkins, Geruso and Watkins2 is equal to 0.0086. A slag would have to contain 0.020/0.0086 = 2.3 per cent. effective FeO or less in order to prevent the metal from containing more dissolved FeO than that required for equilibrium with CO at 1 atm. pressure. Such low percentages of FeO are never found in basic open-hearth slags at the completion of a heat when rate of carbon drop has become practi-

Jan 1, 1930

By Haakon Styri

IN discussion of Dr. Fitterer's paper on electrolytic separation of slag inclusions, some results from experiments on electrolyzing high-carbon steels at the SKF Research Laboratory were given.1 We had been working for a number of years on chemical methods of separating the inclusions but could not find any solvent that would dissolve the steel without attacking some of the inclusions, particularly the sulfides in which we were mostly interested at the time, nor any that would dissolve all sulfide or silica in filings as fine as 300 mesh without attacking the iron. Electrolytic methods had also been tried without any real progress until we learned from the Bureau of Mines about the use of the collodion membrane around the anode. Our early difficulties were to some extent different from those of the Bureau of Mines, perhaps because of experimenting on steels of higher carbon content, but most of our difficulties were of the same nature as those of the Bureau. Formation of large quantities of basic hydroxides use of impure and oxidized ferrous sulfate. To protect from oxidation from the atmosphere during electrolysis, after purer chemicals were obtained, a thin layer, 1/8 in. or less, of molten paraffin was poured over the surface of the cathode liquid, where it solidified. It was found desirable also to hold the cathode chamber slightly acid by initial addition of 0.1 per cent acid (sulfuric or hydrochloric) to prevent precipitation of the hydroxide. This acidity would decrease gradually and the cathode chamber would become neutral before the end of the electrolyzing. The increase in acidity in the anode chamber during our early experiments had appeared to cause attack of the precipitated sulfides in the residue, which originally was analyzed by volumetric method for sulfur, and for this reason a 10 per cent sodium citrate solution was substituted for the sulfate in the anode chamber.

Jan 1, 1932

By Fred A. Krafft

The time allotted to this paper will permit only the sketching of general principles and practice as generally employed in the industry to maintain and preserve the physical well-being of the miner and his family. Let it be emphasized on behalf of the industry that coal opera- . tors, individually and collectively, have given primary consideration to the appointment of a mine or community physician who is charged with the responsibility of caring for the sick and injured. However, it too frequently happens that with the selection or appointment of the camp doctor many operators wash their hands of further responsibility toward the health and the working efficiency of their employees. The coal industry is so organized in most of the coal-producing areas that not only is the health of the individual miner an important production problem but the collective health of the entire mining community is a fundamental operating problem. This is particularly demonstrated when epidemics of communicable diseases attack entire communities, with resultant loss of life and production and general community distress. The problem and responsibility of maintaining high health standards among miners and their families should be given as much consideration as safety, economical production and efficient distribution are given in the successful operation of coal mines. Company Policy In the inauguration or administration of a medical program for a large mining operation or for an individual mine, the first question to be solved is what the company policy is to be with respect to the following factors pertinent to a medical program: 1. On what basis will the company and the employees finance the program ? 2. Should a contract doctor or a full-time doctor on salary be employed ? 3. What measure of service is to be rendered the employee and his family in return for his monthly contribution to the medical program?

Jan 1, 1936

By James Norman, Oliver C. Ralston

DIATOMACEOUS earth occurs in deposits widely distributed throughout the nation. The chief producing areas are in the Western States, where many high-grade deposits are known. Eastern deposits of diatomite are unsatisfactory for many purposes either because of impurity or because of the extremely fine particle size. Eastern users of diatomite, on the whole, must pay for transportation of the material from the west coast. The freight rate is necessarily high because of the great bulk of the diatomite. A satisfactory process of purifying the diatomaceous earths of Maryland and Virginia, which are unsuited for wide use only because of impurities, should be of value to eastern users. In the past, benefication of diatomite by wet processes has been limited to classification or sedimentation for the removal of sand from diatoms. Calcination with salt is used to produce a white diatomite when iron is present in the impurities, and small amounts of clay are rendered inactive in the process. No treatment has been developed whereby a large proportion of clay can be removed from a low-grade diatomaceous earth to give a diatomite of very high purity. In August 1937 the Federal Bureau of Mines, in cooperation with Dr. R. C. Williams, of Baltimore, undertook the problem of purifying low-grade Maryland diatomite by Froth flotation. Work was done at the Eastern Experiment Station, College Park. Unless otherwise stated, the crude diatomite used was from the Patuxent River deposits near Dunkirk. This material, consisting of roughly one-third each or clay, quartz sand and diatoms, was representative of the usual low-grade marine diatomite found in the Coastal Plain Miocene beds of Maryland and Virginia and sporadically in other Atlantic coast states. As received, it contained 50 to 60 per cent moisture and probably had been wet since its formation.

Jan 1, 1942

By C. N. Schuette

THE producers of this liquid metal call it quicksilver, while the consumer generally refers to it as mercury. It is one of he seven metals that were known to the ancients. These seven were gold, silver, iron, copper, quicksilver, lead, and tin. Other metals were sometimes accidentally alloyed with some of these, but it was not until 1490 that antimony, for example, was discovered and identified as a separate metal. It is not surprising that quicksilver should have been known in ancient or even in prehistoric times, as globules of the native metal often occur in the outcrops of the ore. Furthermore, the first man to build a fire on an outcropping of quicksilver ore would probably have found globules of quicksilver in the cold ashes of his fire after it burned out. The inability to pick up the globules with the fingers would excite interest and an attempt to gather it in shells or gourds to be exhibited and traded. The ore of quicksilver is the red sulfide, cinnabar, which has been mined and used as the pigment vermilion since before the beginning of written history. In recorded history, quicksilver is first mentioned in documents by Aristotle, 384-322 B.C. Theophrastus, in 315 B.C., credited the Athenian, Callias, with the invention of methods to beneficiate cinnabar in 415 B.C. In China also there are records antedating Christ which mention both vermilion paint and the fluid metal. From these early records, it seems certain that not only was cinnabar used as a pigment in those days but also that the metal was reduced from the ore and was used for amalgamation, for gilding, and for medicinal purposes. Quicksilver mining and metal-

Jan 1, 1953

By Oliver C. Ralston, James Norman

DIATOMACEOUS earth occurs in deposits widely distributed throughout the nation. The chief producing areas are in the Western States, where many high-grade deposits are known. Eastern deposits of diatomite are unsatisfactory for many purposes either because of impurity or because of the extremely fine particle size. Eastern users of diatomite, on the whole, must pay for transportation of the material from the west coast. The freight rate is necessarily high because of the great bulk of the diatomite. A satisfactory process of purifying the diatomaceous earths of Maryland and Virginia, which are unsuited for wide use only because of impurities, should be of value to eastern users. In the past, benefication of diatomite by wet processes has been limited to classification or sedimentation for the removal of sand from diatoms. Calcination with salt is used to produce a white diatomite when iron is present in the impurities, and small amounts of clay are rendered inactive in the process. No treatment has been developed whereby a large proportion of clay can be removed from a low-grade diatomaceous earth to give a diatomite of very high purity. In August 1937 the Federal Bureau of Mines, in cooperation with Dr. R. C. Williams, of Baltimore, undertook the problem of purifying low-grade Maryland diatomite by Froth flotation. Work was done at the Eastern Experiment Station, College Park. Unless otherwise stated, the crude diatomite used was from the Patuxent River deposits near Dunkirk. This material, consisting of roughly one-third each or clay, quartz sand and diatoms, was representative of the usual low-grade marine diatomite found in the Coastal Plain Miocene beds of Maryland and Virginia and sporadically in other Atlantic coast states. As received, it contained 50 to 60 per cent moisture and probably had been wet since its formation.

Jan 1, 1942

By Fred A. Krafft

The time allotted to this paper will permit only the sketching of general principles and practice as generally employed in the industry to maintain and preserve the physical well-being of the miner and his family. Let it be emphasized on behalf of the industry that coal opera- . tors, individually and collectively, have given primary consideration to the appointment of a mine or community physician who is charged with the responsibility of caring for the sick and injured. However, it too frequently happens that with the selection or appointment of the camp doctor many operators wash their hands of further responsibility toward the health and the working efficiency of their employees. The coal industry is so organized in most of the coal-producing areas that not only is the health of the individual miner an important production problem but the collective health of the entire mining community is a fundamental operating problem. This is particularly demonstrated when epidemics of communicable diseases attack entire communities, with resultant loss of life and production and general community distress. The problem and responsibility of maintaining high health standards among miners and their families should be given as much consideration as safety, economical production and efficient distribution are given in the successful operation of coal mines. Company Policy In the inauguration or administration of a medical program for a large mining operation or for an individual mine, the first question to be solved is what the company policy is to be with respect to the following factors pertinent to a medical program: 1. On what basis will the company and the employees finance the program ? 2. Should a contract doctor or a full-time doctor on salary be employed ? 3. What measure of service is to be rendered the employee and his family in return for his monthly contribution to the medical program?

Jan 1, 1936

By J. F. Myers, S. D. Michaelson, F. C. Bond

THIS work was undertaken with the object of collecting plant data on rod milling, making laboratory tests on representative samples of the various ores, and arriving at a basis for comparing the relative efficiencies of different mills operating on widely different materials and under varying conditions. These efficiencies consider only power consumption and do not include the other elements of operating costs. The over-all economic efficiency may be quite different from the consumption efficiencies with which this paper is concerned. It is hoped that these collected data will be of value in indicating the most favorable conditions of rod-mill operation. Operating-plant data on 14 different installations from 11 plants throughout the United States and Canada were collected, and laboratory tests were made on samples of these ores. The plant rod mills were all operated wet, and either in open circuit or with circulating loads so small as to be negligible. Data were obtained on one roll-crushing operation at the Utah Copper Co., for comparison. The rolls were operated wet in closed circuit with 10-mesh vibrating screens, and with a high circulating load averaging about 600 pct. This particular roll operation can be considered as a model of efficiency. The collected plant data are necessarily incomplete in some instances. Each ore was assigned a code number, and the name and location corresponding to the code number are listed in Table I when permitted. [ ] The power data in every instance refer to motor input. Net power was reported by the operator for samples I-39 and I-45, and this was increased by 20 pct to compensate for motor losses and power factor. The plant rod-mill data are listed in Tables 2 and 3. In Table 2 the speeds are calculated on the basis of partly worn rod-mill liners 2 in. thick. Where D

Jan 1, 1947

"Coulter's Rainbow and Crooked Falls are situated about five miles below the City of Great Falls. Coulter's, the first of the series in the course of the river, is unimportant and has been submerged by the Rainbow dam. Next below Coulter's is the Rainbow Falls, 47 feet in height. Following Rainbow Falls is the Crooked Falls, 21 feet in height. The power developed at this point is such that the one clam, power house and tail-race utilize the power from all three of the above falls.The development at Rainbow was started October, 1908, and completed July, 1910. It has a total capacity of 21,000 k-w. in generators, and 36,000 h-p. in waterwheels, and operates at 105 foot head. The general scheme of development is typical of what may be called standard practice in the west for plants of medium head, and consists of a low diverting clam, a double pipe line feeding into a balancing reservoir near the plant, and individual pen-stocks supplying the turbines from this reservoir.The dam is a rock-filled crib structure 1,146 feet long and 29 feet high, the up-stream side of which slopes at such an angle that the stability of the clam is assured even under the greatest floods, the weight of the water acting to hold it down, so that the higher the flood the greater the stability. The down-stream side is also sloping and tapers off into a long apron so designed as to take care of any overflow which may occur without shock or commotion. The clam is founded on solid rock throughout its entire length."

Jan 1, 1913

HUBERT INGERSOLL ELLIS Hubert Ingersoll Ellis, who met accidental death on Jan. 6, 1919, in eastern Washington, had already advanced far in the profession of mining engineering and gave promise of a brilliant future. He was born on the Washington coast in June, 1889, and had his preparatory schooling at Menlo, Wash. In 1905; he entered the College of Mines of the University of Washington, and at once made a high record of scholarship. After completing 3 years of his technical course, he went to the interior of Alaska, where he spent 4 years in mining. During this time he was field correspondent for technical-magazines and wrote several important articles. In 1915, Ellis completed his senior year in the College of Mines; his graduation thesis was a comprehensive paper on mining methods at Fairbanks, Alaska, which was published as a series of articles in the Engineering and Mining Journal. On July 14, 1915, he entered the employ of the Bunker Hill & Sullivan Mining & Concentrating Co., Kellogg, Ida., as an underground miner, and was soon promoted to the position of operative on experimental metallurgy and later chemist in the same work. Later, he did exhaustive work on flotation with particular attention to the use of various addition agents. For the past 212 years, his work was largely in the field, examining mining prospects and directing work of investigation, during which time, while located at Sumter Valley, Ore., in 1916, he was elected to membership in the American Institute of Mining and Metallurgical Engineers. During the same year, he was married to Miss Grace Wells, of Arkadelphia, Ark., and besides his widow leaves a young son. In Hubert I. Ellis, there was found the rare combination of executive, administrative, and business ability, together with a temperament exceptionally well adapted and trained for research work and for the careful and exhaustive examination of engineering problems, both practical, and academic. These qualities were in addition to a splendid physique and a personality that made him highly successful in the handling of sub-ordinates and in his contact with his associates and the public.

Jan 4, 1919

By Mary Louise Theodore, R. G. Aspden, D. A. Colling

T RACES of sulfur have a marked influence on the physical and mechanical properties of many iron-base alloys. The commonly used combustion method for the determination of sulfur content is not accurate enough at the 50 ppm level by weight and below to be useful in determining the influence of sulfur. Kriege and Wolfe' have described a method for the determination of sulfur in iron alloys in which the sulfur is evolved as hydrogen sulfide followed by reaction with N, N-dimethyl-p-phenylenediamine, and iron (111) to form methylene blue which is measured spectrophoto-metrically. This method of determining sulfur has been used to study the activity of sulfur in Fe-Si-S alloys,' but has not been previously applied to the determination of sulfur in Fe-Ni alloys because of the insolubility of nickel in dilute hydrochloric acid. Dissolution of nickel in dilute hydrochloric acid, however, can be greatly accelerated by the addition of a small amount of platinic chloride.3 By combining these two techniques in a procedure in which 0.005 pct platinic chloride in 1:l hydrochloric acid is used as the dissolving fect on the strength of the material. However, ductility is influenced by the presence of discontinuous precipitation. In Fig. 5, percent elongation data at room temperature and 1400°F is shown for two sets of specimens of Waspalloy which were solution heat treated at 1950°F and either quenched or slow cooled to the aging temperature and then aged for 100 hr at 1292" and 1598ºF, respectively. At room temperature the existence of a discontinuous precipitation cell at grain boundaries (see data point marked by arrow) has no apparent effect on ductility. However, at elevated temperatures a pronounced lowering of ductility occurs when discontinuous precipitation has occurred in the specimen. It would appear that the morphology of discontinuous precipitation "cells" at grain boundaries would be highly conducive to the initiation of cracks which in turn lead to premature "grain boundary" failure.

Jan 1, 1970

By Clemens Jones

THE analytical history of phosphorus in its relation to the metallurgy of iron is an interesting study, the progress of which runs parallel with the development of the greatest industry in the world. Without the means of finding out how much phosphorus crude pigiron contained, the Bessemer steel process would have been impossible. To do this was originally tedious and slow work. On the other hand, the " direct" process of to-day, as well as the various special processes for steel or iron, have demanded the utmost rapidity in the operations of analytical chemistry. In general, any rapid process for the conversion of unrefined metal into a product of standard composition depends upon the rapidity of some accurate means employed to control it. Moreover, in our modern practice, it is not improbable that the differences in physical properties among the various makes of iron or steel are affected, if not produced, by the use of different methods of analysis. Recourse is always had for correction to the ((standard methods," but I incline to think that these methods are susceptible to error. It is very certain that the system of duplicates would not be resorted to, if the fact were otherwise. Even when duplicated, under the most careful and skilful manipulation, these standard methods produce disagreements. In proof of statements like these, which may sound. heretical, I hope, further on, to cite some evidence worthy of attention. I do not now mean to lay claim to the distinction of discovering the ultimate corrective. That result will come, no doubt, in. time, as the product of the experience of many workers. In the case of phosphorus, as of the other ingredients of iron or steel, a great deal has been done to accommodate the methods of analysis in rogue to the growing necessity for more rapid procedures: Much of this work has concerned what might be called the incidents of method. There is no better example of the accumulation of these incidental improvements than the work done on phosphorus; and I

Jan 1, 1890

By W. T. Thom

Many able men have contributed to the subject of coal classification, and recent publications on the subject have indicated a crystallization of opinion in that connection which promises the development in the near future of a scheme of coal classification which will be of real and increasing value to coal producers and users, as well as to those interested in coal on more exclusively scientific grounds. It is obvious that such a classification must be simple; must be based upon readily ascertainable factors; and if properly developed will apply to the whole range of coals between peat and anthracite and not merely to certain types of coal. Many of the numerous schemes of classification proposed in the past have given quite satisfactory results when applied to the higher rank coals, but have broken down when applied to the younger coals of higher moisture, and, as previously pointed out by the writer,' this breakdown has been due to the practice of ruling out "moisture" as an essential component of the volatile matter reported in the customary proximate analysis of coal, whereas a review of the mode of formation and natural history of coal satisfies us that moisture is a normal and natural ingredient among its volatile constituents; and a knowledge of analytical practice shows that the "moisture" and "volatile matter" reported are both mixtures of moisture and volatile matter, rather than sharply differentiated distillation fractions. After an extended consideration of the subject the writer regards the conventional proximate analyses of coals as affording the information essential for a both practically and scientifically satisfactory c1assification—assuming that the coal samples compared have been collected and analyzed according to standard methods. Two variables are required for a workable classification, and these appear to be afforded by the calorific value and proportion of volatile constituents (including moisture) credited to the coal on an ash-free basis. The writer originally proposed that the figures used for classification purposes be those given for the "air-dried" and "ash-free" form of the proximate analysis,

Jan 1, 1930

By Harrison Schmitt

IN the practice of ore finding the geologist is continually confronted with the question of oreshoot extension, so that the general problem seems worthy of systematic investigation. This problem appears when the reserves are estimated and when the advisability of deepening the shaft comes up. Moreover, there is need for lower development cost to keep pace with cost reductions in other departments, or even to offset a rising cost of ore finding or ore following. This can be gained by close geologic control of the development; and much of the geology involved is that bearing on the downward, upward, and horizontal extensions of shoots. Furthermore, the purchase of a mine or prospect often depends directly on the question of shoot extension; because it is seldom that the ore is fully developed and the purchase price is almost invariably based largely on "possible" and geologically prospective ore. Most current methods for estimating '(possible" and the more nebulous classes of ore are crude and indecisive. In the following pages the extension of oreshoots is the major theme, although the more basic subject, the general art of ore finding, is given some space. (A) Direct Methods of Extension Prediction (I) Extrapolation and Interpolation of Shoots by Use of Conventional Geologic and Assay Plans, Projections and Cross-sections There is little need for stressing the desirability of detailed geologic plans, assay plans, projections, and cross-sections as a basis for the study and extension prediction of shoots. Underground and surface mapping, in most cases, ought to be done in exhaustive detail. All features of obvious bearing should be mapped and it is good practice to record all possible details, some of which may become significant when studied in the ensemble. It should be emphasized that the mapping should be done with an impartial mind, with interpretation reduced to the minimum. The symbols of the map can be made to distinguish observed facts from interpretation.

Jan 1, 1929

By R. F. Mehl, M. Gensamer

THE stresses which initiate deformation processes in metals are fundamentally important in the study of the mechanical properties of metals. A point of inflection in the load-elongation curves obtained for single crystals1 has been rather too readily interpreted as a true yield point, and the critical resolved shearing stress on the plane of slip taken as a material constant. Even early work showed that the stress at this point varies with rate of loading, but it has not been generally appreciated that creep tests under static loads alone are suited for determining the existence or nonexistence of a yield point.2 It has now been shown by Miller that single crystals of zinc3 when loaded statically begin to yield at loads too small to measure; as a result there is no case now known, apart from that cited in the present paper, in which a true critical stress for yielding has been demonstrated for single crystals of metals. The case of iron has especial interest: the existence of an upper and lower yield point and of an elongation at the yield point in ordinary iron and steel marks this substance as unusual, though the effects have been found to a very minor degree in other metals and alloys. ‡ Most alloys do not show such marked phenomena when appreciable yielding begins, and accordingly modern practice is to speak of the yield strength of such materials, a stress read from the load-elongation curve after elongation has begun, rather than yield point. The special behavior of iron suggests that it is more likely that single crystals of iron should have a true yield point than other metals. The study of the mechanical properties of metals and alloys requires a determination of the crystallographic mechanism of deformation, whether deformation proceeds by slip, twinning, or cleavage, or a combination of these, and a determination of the stresses that induce these modes of

Jan 1, 1938

By Leo D. Jones

The use of the centrifuge for dewaxing lubricating oils grew out of the effort to secure better results than had been attained by the common "cold settling" process. This process was the only known method for dewaxing steam refined cylinder stock (600" F. fire test), the product known as "bright stock" being commonlyused for building up "pressed," i.e., dewaxed neutrals of, say, 200-sec. viscosity [to a higher value. The process consisted of mixing the cylinder stock with approximately one and one-half times its volume of naphtha, heating, to dissolve completely all the oil and wax and then slowly chilling to about 15" F. in large insulated tanks. This caused the wax to precipitate. It was allowed to settle out by gravity. The supernatant liquid was then drawn off and the naphtha distilled off, leaving a still residue of bright stock. The sediment from the settling, of a slushy nature, was withdrawn. After removing the naphtha by distillation the residue was petrolatum. At some point in the process, preferably after the dilution but before chilling, the mixture was decolored by percolation through fuller's earth. The finished bright stock produced by this process had a cold test of about 50" F. Efforts to improve this by chilling to a lower temperature resulted in a considerable reduction in yield, and increased uncertainty of settling. Even when chilling to 15" F. it was not uncommon to find that after a week's waiting a tank had not settled. It was then necessary to heat and rechill. This uncertainty was a serious problem; in one case a refinery superintendent had men riveters hold pneumatic hammers against the tank for hours, hoping thus to cause agglomeration and settling of the wax. Yields of bright stock above 70 per cent, were uncommon. History of Centrifugal Application It is not surprising, therefore, that many attempts were made to improve upon the results obtained by cold settling. George H. Taber, vice-president of the Gulf Refining Co., Pittsburgh, Pa., made a number

Jan 1, 1924

By T. R. Young, S. A. Scott

9.5-1. Introduction. The use of pipelines to transport solids has been successfully accomplished with many different materials. One of the oldest applications is the dredging and placing of hydraulic fill. Many installations have been made and operated for long periods of time with excellent dependability, low operating cost, and low maintenance. It is not the aim of this chapter to give the engineer the answers from which to design a pipeline, but rather to supply helpful information from which to start the project. There are several phases of solids pipelining which as yet have not lent themselves to quick engineering answers. Investigations have been carried on by many, with several theories advanced by the various investigators. In recent years certain notable theoretical advances in hydraulic transportation have been achieved. Vertical transport, using balanced "leg" operation, now appears competitive with other forms of vertical transportation. In addition, horizontal transport utilizing capsules has been proven experimentally to be attractive because of lower pressure drop than the conventional methods of solid transport in fluid media. With the aid of the computer, the laborious calculations associated with pumping calculations have been greatly simplified; and with this tool the pipeline engineers of the future will undoubtedly be able to develop a more comprehensive understanding of solids-fluid transport. 9.5-2. Theory. There have been many excellent studies made and information is available in the literature, but a general comprehensive theory of pipeline transportation of solids has not been advanced. The existing flow theories will give approximations for minimum and optimum flow velocities, friction head losses, energy requirements, and pump and pipe size The principles of dynamic similarity and scaling laws are well understood for the flow of pure liquids. There are no firm methods of scaling slurry pipelines of small diameter to larger diameters except for a few empirical.

Jan 1, 1968

By Z. T. Bieniawski

The importance of understanding the phenomena associated with rock fracture has long been fully appreciated in rock mechanics. This is clearly apparent from the special attention paid to rock fracture in the comprehensive papers published within the past four years.l-5 These papers present a picture of how the knowledge of brittle fracture of rock was gradually enriched and also show that what was often taken for granted three or four years ago is no longer considered as valid today. The Griffith hypothesis,6 thought in the past to predict the strength of rock, is now known to be applicable to fracture initiation only. The knowledge of a failure criterion for fracture initiation is not sufficient, however, as after fracture initiation the rock is still a useful material even possessing increasing load-bearing ability. The importance of the fracture propagation process, subsequent to fracture initiation, is thus obvious. Yet, relatively little attention has so far been paid to brittle fracture propagation in rock. As it is now realized that understanding of this process is a prerequisite for practical rock mechanics applications, studies of propagation of brittle fracture in rock constitute an important aspect of rock mechanics research. It has been pointed out 4 that it is essential that the failure mechanism is fully understood before a failure criterion is postulated. Many failure criteria have been propounded in the past on the basis of theoretical reasoning alone and could not be verified by experimental evidence. Recently, a hypothesis for the mechanism of brittle fracture of rock was propounded, 4 describing the events taking place in the rock from the initial application of gradually increased load to complete disintegration of the material.

Jan 1, 1972

By L. A. Rose

AMONG the half-dozen major research search projects now being conducted at the Michigan College of Minim, and Technology under the terms of an FERA grant, an important one relates to the use of suspensions in ore dressing. The study has resulted from the constantly widening industrial use of metals and minerals. The modest demands of a few decades ago for these minerals could be easily met from richer deposits. Now, at least in some localities, the richer deposits are nearing exhaustion. Furthermore, advances in the industrial arts and the competition of other minerals and metals have changed the specifications of materials needed by the manufacturers. Premiums and penalties enter into the sale value. Hence, to meet the requirements for amount and quality, washing and other ore-dress-

Jan 1, 1935