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By F. C. Blake

The apparatus which I shall describe in this paper has been in ase for some time at the laboratory of the Pennsylvania Lead Company's works, and has been found to give good results, and to be simple and convenient. Steam Bath.—This steam bath is shown by Figs. 1, 2,3 and 4. It is made of sheet copper, about one-twelfth of an inch thick, the joints being brazed, and is used for heating the bottles in which the silver samples are dissolved,-previous to the fineness determina-

Jan 1, 1882

By Edward Richardson

As DEVELOPED up to the end of the Great War, an airplane was essentially a mechanism of wood and fabric, joined and held together by metal fittings and, fastening. The engine and accessories, wire for wheel spokes and other tension members, and the occasional use of metal for interplane struts and the shafts of surface controls required some metal, but essentially it was a. wood and fabric structure. Attempts had been made to use metal for other purposes, such as struts in the drag-trussing of wing panels and for short interplane struts, and Junkers had produced an airplane of iron in 1915. By 1917 he was using steel tubes and duralu-min sheets, securing noteworthy advantages aerodynamically and from the standpoint of weigh PRINCIPLES OF AIRPLANE CONSTRUCTION The loaded weight of airplanes ranges from 500 lb. for the light plane of which we heard so much a short time ago, to about 40,000 lb. The great majority of planes range from 2000 to 10,000 lb. Of this weight from 15. to 30 per cent. is for the dividend-earning load. This percentage is so low that every per cent. saved on the rest of the weight increases the pay load from 3 to 6 per cent. The economic value of every pound that can be saved in designing or constructing a plane is sufficiently great to warrant spending money on refined methods of structural analysis, materials of superior strength properties for a given weight, methods of manufacture which may make possible the use of refinements in structural design, and the like, to an extent unknown heretofore.

Jan 1, 1928

By H. F. Moore

AT PRESENT, I am connected with an investigation of the so-called fatigue of metals under stress. So far we have studied the more fundamental and simple case of the repeated stress, without the additional complexity of impact, which might bring in other factors. We feel that this investigation, which has been in active progress for a little over a year, has shown more conclusively than has been shown before that steel under repeated applications of stress, reversed from positive to negative, will not fail below some fairly clearly defined limiting stress that,, so far we can see, does not bear any definite relation to the ordinary elastic limit, being as large as the elastic limit in some cases and about one-half the elastic limit in others. I might be asked, first, what is fatigue. The old view is summed up "in the word "crystallization." The idea was that under repeated stress the material changed its crystalline structure. I do not know of any evidence in favor of the theory that metals materially change their crystalline structure under repeated stress. The crystals are broken under repeated stress. The second theory, advanced by Bauschinger, the German scientist, is that under repeated stress some inherent property of the material changes its elastic limit; it is an inherent property of the material, possibly some property of the amorphous cement between the crystal. The third view is that all fatigue of metals is the result of the spread of damage from little localized overstresses. I do not feel justified in stating my positive belief in the third view as against the second, but I have yet to run across a case of failure of steel or other metal, either in the laboratory or in service, that could not be explained by the gradual spread of damage from some nucleus. We have found, for example, that it is possible to subject a homogeneous steel, like Armco iron or a 0.90 per cent. carbon steel, that hag been thoroughly annealed, to one hundred million reversals f stress as high as the elastic limit of the steel with no sign of failure. We stopped the test at one hundred million because the machines Were required for other work. Forty-five days, continuous running at 1500 revolutions a minute is required to produce one hundred million repetitions. On the other hand, a complex structured steel, like a chrome-nickel steel that

Jan 6, 1921

By R. C. Ku, R. G. Davies

The stress-strain behavior of Fe-C and Fe-Ni solid-solution alloys has been investigated at 25°C. It is found that the rate of solid-solution strengthening is dependent upon the strain at which the yield stress is measured, the macroyield stress being much more concentration-dependent than the microyield stress. In fact the addition of nickel does not lead to any increase in the microyield stress of iron. The primary effect of increasing the carbon or nickel content is to increase the slope of the stress-strain curve in the microyield region; this effect has been correlated, by means of transmission electron microscopy, with a decreased ability of the dislocations to cross-slip. It is concluded that the Mott-Nabarro theory is a good description of true solid-solution hardening in these and other iron-base alloys. A.LL theories of the solid-solution strengthening1-4 indicate that the flow stress of an alloy increases both with solute concentration and "misfit" between the solvent and solute atoms. The functional relationship between strength, solute concentration, C, and misfit depends upon the particular theory. Mott and Nabarro1,2 and Schoeck and Seeger3 both predict a linear increase in strength with concentration, while Fleischer4 indicates that the strength should be proportional to C1/2; there are in the literature experimental observations to support both these compositional dependencies.1'8 The experimental evidence used to support the theories is the change in macroscopic yield stress (strain, e, = 10-3) with composition. However, recent investigations have revealed that solid-solution strengthening in a Cu-Al single crystals7 and in Fe-V polycrystal-line" alloys depends upon the strain at which the flow stress is measured; a flow stress in the microplastic range (e = 10-6 to 10-5) is much less concentration-dependent than the macroyield stress. Since the theories of solid-solution strengthening are concerned in particular with the stress to move a dislocation in a dislocation-free matrix, they should only be compared with microyield-stress data; it will be shown that in a material deforming homogeneously the microyield stress (e = 10-6) is approximately the stress to move through the matrix those dislocations which have been nucleated by stress concentrations such as particles or grain boundary ledges.9-11 In contrast, the macro-yield stress is more complex in that it is affected by several phenomena: dislocation multiplication, dislocation interactions, and the ease of propagating slip across grain boundaries. For example, it is experimentally observed that when long-range order12'13 or solute effects10 restrict cross alip the grain boundary

Jan 1, 1967

By D. W. Loucks

There is plenty of evidence to indi-cate that at least one of man's chief interests in life is to make himself as comfortable as possible. If you doubt this, just watch the fellow next to you for the next half hour trying to find the most comfortable position that a hard chair has to offer. Comfort, however, does not always mean an easy chair. To some, it may mean a wealth of money; to another, freedom from worry. But to most of us, it means first of all a comfortable atmosphere in which to live, and to a great many of us it probably also means freedom from that annoying task of firing the furnace. Today more than ever before. automatic heat is one improvement that is placed high on everyone's list. Perhaps this is because automatic heating is becoming relatively cheaper. Perhaps it is because of a good publicity campaign on the part of the oil and gas men or maybe it is just that we are getting lazier day by day. At any rate, almost every issue of Better Homes and Gardens, House Beautiful, or your other favorite home magazine carries an article extolling the virtues of this or that automatic heating system. If I were to ask you to name the first thing that came to your mind when I said automatic heat, you would prob-ably say either gas furnace or oil burner. Or if you had just been studying heating systems, you might possibly say heat pump. But chances are you would not mention anything about coal, and yet coal is the most common source of the greatest automatic heat of them all. I say this because coal is the fuel used almost universally by the district heating industry in producing and delivering to certain heavily populated areas heat ready to use at the touch of a valve or the click of a thermostat. Although the industry is over a half century old, it has not experienced the widespread development of other utility industries because of certain limitations which I believe you will realize from the next few minutes discussion. District Heating Operations We may define district heating as any operation where two or more buildings are heated from a central heating plant. The method of heat transfer may be hot water or in some cases warm air, but generally the medium of heat transfer is steam. So universally is steam used that the industry is frequently referred to as the district steam industry. The Allegheny County Steam Heating Co. which operates the district heating system in downtown Pittsburgh is a subsidiary of the Du-quesne Light Co. Although organized in 1912 primarily as a means of securing the electric load of downtown buildings, the service has now become so valuable and so popular that it is no longer considered a necessary adjunct to the electric business but rather a separate business standing on its own feet. Fig 1 shows the layout of the plants and distribution system of downtown Pittsburgh. Two generating plants, one known as the Stanwix and the other as Twelfth Street, supply the area. Each has two boilers with capacity totaling 1,350,000 lb per hour. The Stanwix Plant is supplied coal by truck. The coal is pulverized at the plant and burned as powdered fuel. Coal is supplied to the Twelfth Street Plant also by truck but the boilers arc stoker fired. Over 1 1/2 miles of tunnel house a portion of our main lines, but it requires over twelve miles of pipeline, ranging in size from 32 down to 1 in. in diameter, to supply all our customers. The distribution system consists of two systems in a sense, one high and one low pressure with certain interconnections between the two. Our high pressure system supplies steam up to 125 Ib to some but not all customers, while the low pressure system operates in the range of 10 to 20 psi. Note that the two plants are tied together through large steam mains and that the system to some extent is a loop system, making it possible to have a portion of the line shut, down without interrupting service to any customer. Fig 2 conveys a picture of the extent to which steam service is used in the downtown triangle. The black area indicates the buildings which now use district steam. The dotted area indi-

Jan 1, 1950

By Francis Donaldson

The direct injection of cement grout into water-bearing fissures as a means of checking or stopping the flow of water into shafts and tunnels has been experimented with for a decade or longer and seems to have been first attempted in Europe. The earliest application of which the writer has found a record was at a shaft sunk by the Mining Society of Lens; this is described by C. Dinoire in the Transactions of the Institution of Mining Engineers.1 It is only lately, however, that the process has been entirely successful. This success has been accomplished on the Catskill Aqueduct, now under construction by the city of New York. This aqueduct includes a number of deep pressure tunnels, reached by shafts for both waterway and construction purposes. In portions of these shafts and tunnels considerable underground water was met. The contract for the first of these deep pressure tunnels was let to the T. A. Gillespie Co.; this section is known as the Rondout Siphon. It leads under the Rondout valley at a depth of from 400 to 800 ft. and is about 5 miles long. The engineers expected that considerable water would be encountered, but fortunately this was not the case except at one shaft, known as No. 4, which penetrated the rock at a junction between limestone and conglomerate. Water-bearing fissures were encountered almost immediately. At a depth of about 200 ft. a flow of 1,500 gal. per minute was struck. The. shaft then contained as many pumps as could be used, and it seemed impossible to sink it further. After vain efforts had been made to proceed, John P. Hogan, a division engineer of the Board of Water Supply, suggested that cementation of the fissures be tried. The process was attempted for the first time in this country. Since the shaft was partly full of water it was necessary to drill grout holes with a diamond drill. Platforms were placed on the timbers at the water level, the diamond drill was installed and six 90-ft. holes were drilled in the bottom of the shaft. Several car loads of cement were pumped through these holes into the fissures, the drill casings being used for grout pipes. This largely cut off the flow of water from, the bottom and sinking could then

Jan 1, 1915

By W. T. Hicks

Visual observation of the oxidation of columbium shows that the protective behavior noted previously in gravimetric work in the early stages of the reaction below 600°C and throughout the reaction at 640°C is associated with an adherent oxide. The fact that the oxide is seen to move outward from the metal at temperatures from 550° to 935°C implies that the reaction takes place at the oxide-metal interface throughout this temperature range. THE work described in this paper further clarifies the complex oxidation kinetics of Cb revealed, for example, by the continuous gravimetric studies of T. L. Kolski.1 Time-lapse motion picture studies reveal details of the reaction not provided by a study of the combustion products. EXPERIMENTAL PROCEDURE Cb specimens were prepared from material with the following typical analysis: 0, 0.03 pct; N, 0.002 pct; C, 0.006 pct; Ta, 0.04 pct; Fe, 0.01 pct; Ni <0.003 pct; and Cr <0.003 pct. Arc-cast ingots were swaged and cold rolled into slabs. These slabs were machined into blocks 7/16 by 7/16 by 7/16 in; 1/16-in. holes were drilled through the large face of the blocks for suspension. The samples were then de-greased and annealed 1 hr at 1200°C in vacuum. The sample was suspended by a platinum and Pt 10 pct Rh thermocouple inside a 1-in. quartz tube in a Kanthal wound furnace (2 in. OD by 4 in. long) equipped with windows 1/2 in. sq. A Cine-Kodak Special II 16 mm motion picture camera was trained on the sample through a Spencer microscope adjusted so that a magnification of X1.5 resulted on the film. Super Anscochrome film was used to record the events in color. Argon was flushed through the furnace while the sample came to temperature. The argon was then replaced by a stream of dry oxygen at 1 atm. Pictures were taken at the rate of eight per second for about 20 sec during the change of atmosphere. Then by use of a Stevens time-lapse device pictures were taken at the rate of four per minute starting within 1 min of the initial oxygen flow. In this manner continuous visual records of the oxidation of pure Cb

Jan 1, 1962

By A. A. Venghiattis

A rational approach to the selection of the appropriate perforator to use in each specific zone of an oil well is presented. The criteria presently in use for this choice bear little resemblance with actual down-hole condilions. These environmental conditions affect the elastic properties of rocks. One of these elastic properties, acoustic velocity, is suggested as the leading parameter to adopt for the choice of a perforator because, being currently measured in the natural location of the formation, it takes into account all of the effects of compaction, saturation, temperature, etc., which are overlooked in the laboratory. Equations and curves in relation with this suggestion are given to allow the prediction of the depth of perforation of bullets and shaped charges when an acoustic log has been run in the zone to be perforated. INTRODUCTION When an oil company has to decide on the perforator to choose for a completion job, I wonder if it is really understood that, to date, there is no rational way of selecting the right perforator on the basis of what it will do down-hole. This situation stems from the fact that the many varieties of existing perforators, bullets or shaped charges, are promoted on the basis of their performance in the laboratory, but very little is said on how this performance will be affected by subsurface conditions such as the combination of high overburden pressure and high temperature, for example. The purpose of this paper is to show the limitations of the existing ways of evaluating the performance of perforators, to show that performances obtained in laboratories cannot be extended to down-hole conditions because the elastic properties of rocks are affected by these conditions and, finally, to suggest and justify the use of the acoustic velocity of rocks, as the parameter to utilize for the anticipation of the performance of a perforator in true down-hole environment. EVALUATING THE PERFORMANCE OF A PERFORATOR It is natural, of course, to judge the performance of a perforator from the size of the hole it makes in a predetermined target. Considering that the ultimate target for an oilwell perforator is the oil-bearing formation preceded in most cases by a layer of cement and by the wall of a steel casing, the difficulties begin with the choice of an adequate experimental target material. For obvious reasons of convenience, the first choice that came to the mind of perforator designers was mild steel. This is a reasonable choice for the comparison of two perforators in first approximation. Mild steel is commercially available in a rather consistent state and quality, and is comparatively inexpensive. The trouble with mild steel is that it represents a yardstick very much contracted; minute variations in depth of penetration or hole diameter and shape may be significant though difficult to measure. The penetration of projectiles in steel being a function of the Brinell hardness of the steel (Gabeaud, O&apos;Neill, Grun-wood, Poboril, et al), it is often difficult to decide whether to attribute a small difference in penetration to a variation on the target hardness or to an actual variation on the efficiency of the projectile. Another target material which has been widely used for testing the efficiency of bullets or shaped charges in an effort to represent a formation—a mineral target as opposed to an all-steel target—is cement cast in steel containers. This type of target, although offering a larger scale for measuring penetrations, proved so unreliable because of its poor repeatability that it had to be abandoned by most designers. The drawbacks of these target materials, and particularly their complete lack of similarity with an oil-bearing formation, became so evident that a more realistic target arrangement was sought until a tacit agreement was reached between customers and designers of oilwell perforators on a testing target of the type shown on Fig. 1. This became almost a necessity about seven years ago because of the introduction of a new parameter in the evaluation of the efficiency of a perforator, the well flow index (WFI). The WFI is the ratio (under predetermined and constant conditions of ambiance, pressure and temperature) of the permeability to a ceitain grade of kerosene of the target core (usually Berea sandstone) after verforation. to its vermeabilitv before perforation. The value of this index ;or the present state if the perforation technique varies from 0 to 2.5, the good perforators presently available rating somewhere around 2.0 and the poor ones around 0.8, There is no doubt that, to date, the WFI type of test is by far the most significant one for comparing perforators. It is obvious that a demonstration of a perforator

By R. H. Wightman

The following paper describes current mining practices of the Riverside Cement Co. at its Crestmore plant, Riverside, California. For a number of years the Riverside Cement Co. obtained its raw materials by surface quarry operations but after these deposits were exhausted for equipment available at that time, the company started underground mining. Mine workings were begun in 1927 to 1930 for the recovery of limestone by block-caving methods. Geology The bed of limestone that is being worked is a metamorphosed and recrystallized limestone, which is generally white in color and from medium to coarsely crystalline. This bed is fissured by water courses that vary from minute cracks to large areas. The bed has also been cracked by intrusions along the footwall and hanging wall. These walls are coarse-grained, gray, quartz granodiorite. The strike of the deposit is north and south and it dips to the east at an angle of approximately 50°. The bed is approximately 1700 ft. long, 270 ft, thick at right angles to the dip at the middle of the deposit and tapers to a thickness of approximately 100 ft. at each end. Mining Methods The mine layout consists of four main levels with elevations as follows: 892 Collar of shaft. 800 Manway level used for ventilation, prospect purposes and as an entrance into the stopes. 700 Mining level where all material is extracted and on which are located the tapping grizzlies. This is the elevation from which all main cutoff stopes and undercutting work is started. 660 Haulage level where the limestone is drawn from transfer raises into the cars and is transported to the tipple by electric locomotives. 633 Level where all water is collected and which keeps the general water table below the working levels. A detailed description of the mine was given in U. S. Bureau of Mines Information Circular No. 6795, in June 1934. Current Block Development The first blocks to be caved were developed very much after the procedure followed in the copper mines of Arizona. This paper covers the ninth block to be caved. with a hard, tough rock like our limestone, it was found that some alterations in the development and control of dm, i, caving were. necessary to secure better crushing effect and provide more safety for such secondary blasting as is required. Sequence of Block Development 1. The fringes of the 800-ft. manway level are driven to confirm the diamond-drill information and serve to determine the final location and development required for the block (Fig. I).

Jan 1, 1946

By D. L. Albright, R. W. Kraft

Solidification experiments were conducted with the objective of testing the theory of eutectic colony formation. Appropriate control of variables in tests on a series of high-purity aluminum-copper specimens of eutectic composition resulted in the observation of three types of eutectic microstructures, these being a unique structure consisting of lamellae essentially parallel to one another, a banded structure, and the colony structure. Lamellar faults, which are morphologically similar in many respects to edge dislocation models in crystals, produced a complex substructure in these specimens. SOLUTE rejection at the advancing solid-liquid interface of a unidirectionally solidified single-phase metal can cause the liquid immediately in front of the interface to become constitutionally super-cooled below the equilibrium liquidus temperature. Constitutional super-cooling occurs if the solidification rate, R, is too rapid, or if the thermal gradient in the liquid at the interface, G, is too low. 1 This constitutionally supercooled layer in turn stabilizes a cellular rather than a planar interface.&apos; A similar cellular interface has been observed when lamellar and other types of eutectics were unidirectionally solidified, and it has been shown that the cellular interface led to the formation of eutectic colonies.&apos; The lamellar structure is fan-shaped at the edges of colonies (which correspond to valleys or grooves in the cellular interface) because the lamellae grow normal to the local interface. One of the possible mechanisms which might cause the formation of the cellular interface, in the case of solidifying eutectic alloys, is constitutional supercooling of the liquid with respect to a third component rejected by both phases of the eutectic.3,4 On the basis of the analogy between the solidification of single-phase metals and binary eutectics, a eutectic alloy should solidify with a planar interface if the ratio of G/R is sufficiently high to compensate for any impurity which might be present and causing constitutional supercooling. The fan-like microstruc-ture of eutectic colonies should not occur under these conditions and the lamellae should be parallel to one another and to the solidification direction for extended distances. The experiments conducted in this investigation were designed to test these ideas. Following a resume of the experimental procedure, the various microstructures observed during the study are described, and their relationship to the growth conditions which produced them is discussed. EXPERIMENTAL PROCEDURE The eutectic between an aluminum solid solution and 0 phase (approximate composition CuA12) was chosen for this work for the following reasons: it was known that a lamellar structure forms, the eutectic temperature is low enough to facilitate experimental work, and the components can be procured commercially in a very pure form. High-purity copper (est. 99.999 pct Cu, obtained from National Research Corp.) and spectrographic aluminum rods, having impurities other than copper estimated to be Zn-15 ppm, Mg-10 ppm, Fe-3 ppm, Na-2 ppm, Cd-1 ppm, and Mn < 1 ppm, were melted in a stabilized zirconia crucible in a vacuum induction furnace at a pressure of 10 pof Hg. The melt was superheated to about 1000°C to assure mixing, cooled to 780°C and cast into an investment mold which yielded sixteen cylindrical specimen blanks 1/2 in. in diam and 5 1/2 in. long. The casting was allowed to solidify under vacuum. This master heat had an analysis of 32.6 wt pct Cu and 67.4 wt pct A1 by difference. The cylindrical specimen blanks were remelted and solidified unidirectionally in an apparatus illustrated schematically in Fig. 1. An RF induction coil heated

Jan 1, 1962

By J. Phillip Neal, Kefton H. Teague, Carroll P. Rogers

Feldspars, the most abundant minerals of the igneous rocks, occur in numerous forms and mixtures. The feldspars of commercial significance are found in widely distributed pegmatites as large crystals usually free of iron-bearing impurities and thus suitable for hand-cobbing, and also in larger bodies where the ore contains various types of feldspar intermingled with quartz and relatively free of iron-bearing impurities, or at least readily unlocked from impurities present at relatively coarse mesh. The latter type of ore includes some pegmatites, and the "alaskite" bodies so common in the Spruce Pine district of North Carolina. On the west coast of the US and in Oklahoma there is-or has been-commercial recovery of natural feldspathic sand as a source of alumina in glass and ceramics. "Aplite" in commercial terminology is a light-colored igneous rock with a granitic composition and a fine sugary texture, often banded with readily removable iron impurities. Only one area in Virginia produces aplite for the glass industry; it is located near Montpelier in Hanover County. According to Deer et al. (1966) the word feldspar derives from the Swedish feldt or jolt (field) and "spath:" chunks of rock appearing in tilled ground overlying granite. Castle and Gillson (1960) indicate a Germanic origin, citing "spat," which is said to refer to any transparent or translucent material which is readily cleavable. The term "spar" has in the past been applied to minerals other than feldspar, such as barite, calcite, and fluorite. It is correct to call the latter "fluorspar." There is a true barium feldspar, but it is rare and of no present economic importance. What is recognized as feldspar or "spar" by present producers and consumers consists of three silicate minerals which, if pure, would have the formulas KA1Si3O8 (microcline or orthoclase), NaAlSi3O8 (albite), and CaAl2Si2O8 (anorthite). These are almost never found in pure form in nature, but occur together in great abundance in a three-component system. A considerable number of different combined ratios of these three exists, with the exception that isomorphism between potassium spar and calcium spar is very limited. User specifications for feldspar products are largely built around the prevalent naturally occurring ratios. Passages following will refer to "K-spar," "Naspar," or "Ca-spar." Nomenclature and Descriptive Terms Relating to both the mineralogy and the economics of feldspar are certain terms whose coverage it is useful to specify. Commercially, aplite is a feldspathic rock mined and beneficiated in one location in Virginia, in which both titanium and feldspar minerals are present-the latter now being the major, if not the only, economic product. Technically, the term aplite when applied to this rock is of questionable accuracy. But, in light of accepted commercial usage, the term will be here used to designate it. Regarding the Virginia rock, Ross (1941) is cited. Alaskite is another term requiring understanding if not precise use. A distinctive rock type customarily called by this name is found near Spruce Pine, Mitchell County, North Carolina. An important major feldspar source, it contains somewhat higher levels of plagioclase feldspar and quartz than alaskite as defined in the Glossary of Geology and Related Sciences, which states that `orthoclase, microcline, and subordinate quartz are the principal

Jan 1, 1983

MAY 17-The last bit of verbal sod had hardly come to rest on the grave of the coal industry-which grave was being eagerly dug with typewriters and microphones by administration hangers-on and even an operator or two-when its leaders gathered for the 1950 Coal Convention of the AMC in Cincinnati on April 24. Surprisingly, mourning clothes were not being worn but the boys had on their diggers preparatory to digging their way out from under the muck. High costs created by wage and welfare demands, together with work stoppages, have caused markets to shrink, but even so, an optimistic air still prevailed as new techniques were disclosed at technical sessions. The administration, however, came in for its share of knocks.

Jan 6, 1950

NEW MEMBERS The following list comprises the names of those persons who became members during the period Jan. 1, 1917 to Feb. 10, 1917. ALLEN, ROBERT SEXTON, Chief Chemist at Concentrator, Inspiration Cons. Copper Co. Globe, Ariz. ALTIO, KARL FREDRIK, Min. Engr., The Sissert Mining District Co., Ltd., Polefskoy Zavod, Perm Government, Russia. ARGALL, PHILIP HENRY, Mgr., Ozark Smelt. & Min. Co., Magdalena, New Mexico. BAILEY, MARC Supt., Wolverine & Arizona Min. Co., Bisbee, Ariz. BAKER, DAVID FRANKLIN, Asst. Supt. of Blast Furnaces, Alan Wood, Iron and Steel Co., Swedeland, Pa. BATES, BENNETT R, Min. Engr 1025 Peoples Gas Bldg., Chicago, Ill. BECK, HOWARD A Shift Foreman, Aurora Cons. Mines Co. Aurora, Nev. BELL, LEO RICHARD Casilla 270, La Paz, Bolivia, South America. BENJAMIN, FLOYD SHAW, District Mgr., Aetna Explosives Co., Inc., 800 Torrey Bldg., Duluth, Minn.

Jan 3, 1917

By Edwin Ludlow

For many years, coal has been known to exist in the valley of the Sabinas river, in the State of Coahuila, and for about 15 years it has been worked by the Mexican International Railway Co., which opened mines for its own fuel-supply when the railway was built, and has been mining continuously ever since. The coal-basin worked by this company lies along the Sabinas river, principally on the SW. side. It covers a wide area and has been carefully prospected, but only in a few parts have the beds been found sufficiently thick and regular for economical operation. This Sabinas basin was considered the only one in this field, until, in the Spring of 1899, the Las Esperanzas basin was found by Messrs. J. L. Elliot and E. D. Peters, who were in Mexico looking after some copper-properties. After a further examination by Mr. James T. Gardiner, of New York, the Mexican Coal & Coke Co. was organized in June, and active work was begun on Nov. 5, 1899. The coal-field of Las Esperanzas, situated in the State of Coahuila, about 85 miles SW. of Eagle Pass, Texas, adjoins and runs parallel with the Sabinas basin—an anticlinal separating the two outcrops by about 2 miles. Fig. 1 is a sketch-map of a part of the basin. The coal-formation is in the Upper Cretaceous, and corresponds with the Laramie measures of the United States. The following geological section, taken in Nogales canon, shows the measures between the massive limestones forming the Sierra de la Santa Rosa and the outcrop of the coal: Section. Feet. Limestone,...Unknown. Blue shale,.........110 Shale and sandstone,.. 60 Bed of fossiliferous shale,. 60

Jan 1, 1902

Jan 1, 1899

By Henry N. Doyle

Basic procedures in the mining industry have changed only slightly over the centuries since metals and fossil fuels became an essential part of man&apos;s economic and cultural life. Mining techniques of the 20th century bear a close resemblance to those of the ancients: exploration, ore breakage and removal, hoisting, and processing. The great advances, however, have been in equipment and machinery of greater size and speed which allow greater efficiency in each of these operations, with a corresponding reduction in manpower requirements. Yesteryear production was measured in pounds per man-day; today a giant and complex, but highly efficient, continuous mining machine can remove as much as eight tons of material a minute from the coal face. If our energy and metal demands of the future are to be met, and at this time it can be assumed that coal will continue to supply a significant part of the energy demand, other dramatic and spectacular technologic advances must be accomplished. Along with mechanization, however, public policy will require the industry to place greater emphasis on health and safety protection, as has been well demonstrated by recent actions of Congress. Together, fossil fuels and metals formed the basis for the industrial revolution-coal to develop power and metals to transform power into useful energy. Strangely enough, however, the mining industry the world over has lagged behind the continuous social changes brought on by the industrial revolution, such as preventive health and industrial hygiene services, and other programs directed to the well-being of the worker. In some countries this resistance, to change may have led in part to the nationalization of the coal industry. Whether this disinclination to social change in the industry of the United States reflects managerial attitudes, inept labor leadership, government neglect, or economic relationship would be the subject of an interesting study. Doubtless the mores of miners and their resistance to change, as well as their geographic isolation from other industrial groups, may have had a strong influence on these factors. In every major coal mining country the accident rate in the coal industry is substantially higher than other industrial groups, and the cost of pneumoconiosis compensation in some countries is greater than the combined costs for all other occupational diseases from all other industries. The high social cost of occupational accidents and diseases may have been a factor in the closing of the industry in at least two countries. Despite diminishing manpower needs, the industry is faced with critical manpower shortages. Miners once reared their sons to be miners; now it appears that the opposite is true. This factor alone, however, does not explain an acute labor shortage in the industry. Traditionally, the industry drew much of

Jan 1, 1976

Jan 3, 1951

By R. T. Hukki

This paper presents a preliminary analysis of the fundamental relationship between the net energy used and the respective product size throughout the entire range of sizes covered by crushing and grinding, and an attempt to find a sensible correlation between the existing theories. Walker, Lewis, McAdams, and Gilliland&apos; have given the following differential equation of a general form for comminution: dE = -C§ [1] where E is the net energy required per unit weight in a certain process of comminution; x is the factor indicating the fineness of the product; n is the exponent indicating the order of the process, and C is a constant related with the material, units chosen, etc. H exponent n in the above equation is replaced by numerical figures 2, 1, and 1 1/2, the integrated form of the general equation leads to the well known fundamental theories represented by the law of von Rittinger,&apos; law of Kick, and the third theory of comminution by Bond, respectively. The total net energies (E) from infinite feed size to a product of size x are as follows: The net energy required in a certain process of comminution is proportional to the new surface developed according to the law of von Rittinger, to the weight or size of the bodies treated according to the law of Kick, and to the length of the new cracks formed which initiate breakage according to the theory and explanation by Bond. On a logarithmic paper, where particle size is presented on the abscissa and energy consumption on the ordinate (see Fig. 21, all three relationships are represented by straight lines. The slope m of the line according to the law of von Rittinger is equal to -1.0; of Kick, 0; and of Bond, -0.5. Experimental evidence in favor of the law of Rittinger has been presented, e.g., by Gross and zimmerley5 on quartz crushed in a drop weight crusher and evaluated for surface by the method of dissolution, by Dean on magnetite crushed by a similar method and evaluated for surface by the determination of coersive force, by piret7 and co-workers on a group of minerals crushed again by a similar method as well as by compression and evaluated for surface by permeability and gas adsorption methods, and by schellinger8 on a group of minerals ground in a calorimetric ball mill and evaluated for surface by gas adsorption. Experimental evidence in favor of the law of Kick seems to be scant in the field of comminution. On the other hand, in the field of mechanical engineering Kick&apos;s law seems to be of fundamental nature in processes such as cutting, pressing, shaping, and rolling of metallic substances. Experimental evidence in favor of the third theory has been provided by Bond." To a large extent, data are based on the vast amount of grindability tests performed in the laboratories of Allis-Chalmers Manufacturing Co. In addition to the devoted proponents of one or the other of the basic theories listed above, certain investigators have indicated that one of the theories might be applied for a certain range of sizes, while another theory might be used for other sizes. In a discussion of a paper by Bond," Dobie" presented a statement at the International Mineral Dressing Congress in London (1952) indicating that 1) for large particles, the law of Kick was approximately correct; 2) for finer particles, von Rittinger&apos;s suggestion was nearer to the truth; and 3) Bond&apos;s new

Jan 1, 1961

By Ralph M. Hunter

UNTIL recent years, maintenance of surface coal handling facilities was a relatively simple task. Equipment consisted principally of conveyors, screens and crushers of comparatively simple construction. Electrical equipment consisted of motors and starters, with little, if any, interlocking. In most cases failure of any component affected only the grades of coal loaded so that even a prolonged break-down did not affect mine operation materially. However, with the introduction of modern cleaning plants, the picture has changed. The equipment is much more complex and therefore more difficult to maintain. In many cases failure of any component of the plant prevents loading of coal. Even if provision is made to by-pass, the quality of coal loaded is lowered, affecting markets. In the case of plants designed to permit full seam mining, marketable coal cannot be loaded without operation of the cleaning plant. Under these conditions it is apparent that considerable thought and effort toward better maintenance are justified. In order to assure continuous, efficient and economical operation, maintenance should receive consideration, not only after the plant is in operation, but while it is being designed. It is hardly necessary to say that the designer should strive for sturdiness and wearing qualities. It is sometimes not realized, however, that even the best parts will sooner or later require replacement or repair. The designer should, therefore, give consideration to accessibility. Anyone who has had to do with cleaning plant maintenance is familiar with installations where several hours are required to get at a part that can be repaired or replaced in a few minutes, once it is accessible. As in most cases, experience is the best guide. The men who operate and maintain this equipment know the problems encountered. Whenever available, the opinions of these men should be sought and heeded. As an example, we might consider the refuse elevator on a Chance Cone. Our company is now operating three of these cones, the first of which was installed in 1941, and the latest in 2946. Exact records are not available, but well over 50 pct of delays charged to the Chance Cones have been caused by the refuse elevator. This elevator receives refuse from the cone and carries it to a point above the water level of the cone, discharging onto a dewatering and desanding screen. Since the elevator operates under water and necessarily has close clearances in the lower boot, it tends to jam on large pieces of refuse or tramp iron. The chain, buckets and boot are also subjected to the action of water, sand and refuse, which accelerate normal wear. In case of jamming or chain-breakage it is necessary to drain the elevator and the cone so that even a minor fault in the elevator causes a considerable loss of time for the cone. In our new plant, which will contain two Chance Cones, the refuse elevator has been eliminated. This was accomplished by raising the cone so that the refuse gates could discharge directly onto the dewater-

Jan 1, 1948

A general discussion on the subject of Crushing and Grinding was held on August 24, 1927, during the meeting of the Institute at Salt, Lake City. G. H. Clevenger, Chairman of the Milling Methods Committee of the Institute, made the following introductory remarks "Several years ago, a number of us felt that the time was ripe for a fundamental investigation of crushing and grinding. At the outset, it appeared that the first thing we needed was a yardstick whereby grinding efficiency could be measured. "The U. S. Bureau of Mines has been most generous in cooperating with the Milling Methods Committee in getting this work well undrr way. John Gross, who served the committee for a year as secretary, was placed in charge of the investigation and has been ably assisted by S. R. Zimmerley. "Messrs. Gross and Zimmerley will now present the Progrcss Report covering their work to date." Progress Report J. Gross, Salt Lake City, Utah.—-This has not been a simple problem, and when I tell you that me can give you a verbal report of what we have done during three years in five or ten minutes you will realize that we have necessarily done a great deal of work that dors riot appear in the final results. We have been in a virtually new field. Therefore, we have had to feel our way at each step so as to be fairly sure we were correet. The first thing that was realized in this problem ass that unless we had some method of measuring what happened when we crushed an ore, we might as well quit and not go further. we realized that if we tried to measure the results of crushing or grinding by the ordiuary sizing test we would not get anywhere. We could sieve down to say 200 mesh fairly accurately; we could even go one sieve size further with a little less accuracy, and then we were absolutely lost, unless we went into microscopic measurement. Even this latter method would not have been satisfactory. The question was: what were we going to measure? If we were going to measure size, we might measure one particular dimension of a particle and be off 200 per cent. or more. If we tried to measure surfaee, we would have something tangible; the surface of a particle, no matter how irregular, is something definite, far more definite than any linear dimension would be. Moreover, if we could measure surface, we would immediately have a method of checking the Rittinger law as to whether it was or was not correct. So the first thing that we sought. was a method whereby we could measure surface on crushed particles or, we will sag., on particles; it would not make any difference whether crushed or not. It then became a question of what kind of particles we were going to use in obtaining a method for surface measurement. We realizcd that it would be rather a corn-

Jan 1, 1928