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By R. B. Lincoln

THE function of a pyrometer protecting tube is to maintain an atmosphere about the thermocouple most favorable to its continued accuracy and long life, and at the same time permit the weld of the couple to attain the full temperature of the area or object being measured. In addition to protecting the thermocouple from the chemical or alloying effects of the products of combustion or bath being measured, the tube must also protect the couple from mechanical injury. The conditions met in practice vary so much that no one material is suitable for all applications. The usefulness as well as the expense of maintenance of a pyrometer system are influenced greatly by a choice of the most suitable protecting tube. The tube must protect the couple without itself becoming too great an expense item. The protecting tube should have the following qualities: (1) A melting point well above the highest temperature to be encountered. (2) Sufficient strength through the entire range of temperatures to hold up its own weight and resist such shock and jar as are unavoidable. (3) It must be impervious to the atmosphere or bath to which it will be subject. (4) It must not give off any vapor injurious to the couple. (5) It must not form any oxides fusible below the highest temperature to be measured. The proper location of the tube in the furnace is almost as important as the choice of material. The tube must be placed as near to the work to be heated .as possible. It must be kept out of the direct path of flame, both because that would give too high temperature readings and because partly burned fuel will destroy the tube faster than the quiet products of combustion.

Jan 9, 1919

By M. R. Tek

General equations relating the pressure drop necessary to sustain the flow of a fluid through a porous matrix at a given rate have been developed. The results indicate that at high values of flow rate the pressure-flow behavior may not necessarily satisfy the usual Darcy equation. The mathematical analysis, carried through the micro-pore geometry and extended through the macro-reservoir scale, indicate that Darcy's law, of limited applicability to certain ranges of Reynolds numbers, can be generalized through the inclusion of some additional parameters. The "generalized Darcy equation" has also been formulated in dimen-sionless form permitting the evaluation of its predictive accuracy with regard to literature data. A comparison between predicted and experimental values indicates that the generalized Darcy equation predicts the pressure drops with good agreement over all possible ranges of Reynolds numbers. INTRODUCTION The limits and the nature of validity of Darcy's law' has been a subject of every-day interest to the industry for many years. It is well known that as the Reynolds number, characteristic of the fluid flow through porous media, becomes large, Darcy's law gradually loses its predictive accuracy and ultimately becomes completely void. For the last 20 years much has been said and written on this subject. Unfortunately little has been accomplished to bring about a satisfactory agreement, at least on the nature of the threshold of validity of Darcy.'s law. Fluid dynamists, geo-physicists, and engineers all had their individual views, explanations, interpretations and concepts on the subject. To some, a mechanistic analogy with pipe-flow proved a satisfactory explanation.' To others,' turbulence, in its random character, was incompatible with the geometric structure of consolidated porous systems. To some,4 turbulence merely represented a factor influencing the permeability measurements and again to others5,6,7 em-pirical or semi-empirical correlations proved satisfactory from an engineering viewpoint. Deviations from Darcy's law at high flow rates have been studied by systematic experiments by Fancher, Lewis, and Barnes.' In an article on the flow of gases through porous metals, Green and Duwezs conclude that the onset of turbulence within the pores appears unsatisfactory to explain deviations from Darcy's law. This view is held by many others. While the subject remained controversial for many years, the development of vast natural gas reserves throughout recent years further justified considerable interest on this problem from the standpoint of gas reservoir behavior. As large amounts of field data became available from the operation of many gas fields, it became evident that the steady-state behavior of gas wells was not, in general, in agreement or compatible with Darcy's law. This suggested a careful reconsideration of all mechanisms which may account for pressure drops in addition to viscous shear. In a series of articles9,10 . Hou-peurt indicated that deviations from Darcy's law may be explained on the basis of kinetic energy variations and jetting effects without resorting to assumptions on turbulent flow conditions. Another article by Schneebeli11 indicates that special experiments by Lindquist clearly demonstrated that the onset of turbulence does not necessarily coincide with conditions of deviation from Darcy's law. This view is also held by M. King Hubbert.12 Starting with the basic pressure-flow relations suggested by Houpeurt, the derivation, development and extension of analytical expressions to -supplement and generalize Darcy's law has been the objective of this work. MATHEMATICAL ANALYSIS Derivation of Dimensionless Pressure-drop, Flow-rate Relations In considering the flow of a fluid through a porous matrix geometrically represented by a succession of capillary passages in the shape of truncated cones,810 an approximate expression may be derived relating viscous and inertial, i.e., total pressure drop to the physical properties of the fluid, geometric properties of the rock matrix and the rate of flow: ?P/?r = µ/k V [ 1 + c(m4 - 1) p V/16n" mµ w] ..........(1) Let us formally set: c (m4 - 1) / 16n" m = a d ......(2) Such a representation is equivalent to assert that the term [c(m4 — 1)/ 16n"m], variable with various porous media and probably highly variable within a given porous medium, may be macroscopically defined as equal to a lithology factor times the aver-age grain diameter d. In view of the usual grain and pore size distribu-

Jan 1, 1958

By C. Schlumberger

LAST year the authors presented a paper that discussed the various electrical measurements they perform in drill holes, which they name "electrical coring."' The object of the present paper is to give a brief account of the points of scientific interest that have been elucidated by further field work and laboratory research, as well as the economic, results that have been attained recently. The practical examples given in this paper are drawn, for the most part, from the field work performed in Russian oil fields during the years 1931 and 1932. This is due to the fact that, thanks to the comprehensive cooperation of the Russian geologists and scientists, the authors are allowed to make public a large amount of recent information. In other countries in which the authors are engaged in similar work, the competi¬tion between private companies makes it imperative, for a considerable lapse of time, to avoid publication of the results obtained. The following points will be discussed successively, under sepa-rate headings: 1. Electrochemical phenomena in drill holes. 2. Stratigraphic correlations and tectonic studies. 3. Relations between the productivity of oil horizons and their electrical resistivity. 4. Location of coal seams. 5. Summary and conclusions.

Jan 1, 1933

By C. Schlumberger

LAST year the authors presented a paper that discussed the various electrical measurements they perform in drill holes, which they name "electrical coring."' The object of the present paper is to give a brief account of the points of scientific interest that have been elucidated by further field work and laboratory research, as well as the economic results that have been attained recently. The practical examples given in this paper are drawn, for the most part, from the field work performed in Russian oil fields during the years 1931 and 1932. This is due to the fact that, thanks to the comprehensive cooperation of the Russian geologists and scientists, the authors are allowed to make public a large amount of recent information. In other countries in which the authors are engaged in similar work, the competi-tion between private companies makes it imperative, for a considerable lapse of time, to avoid publication of the results obtained. The following points will be discussed successively, under sepa-rate headings: 1. Electrochemical phenomena in drill holes. 2. Stratigraphic correlations and tectonic studies. 3. Relations between the productivity of oil horizons and their electrical resistivity. 4. Location of coal seams. 5. Summary and conclusions.

Jan 1, 1933

By N. F. Fiore, M. F. McGuire

THIS communication describes a series of experiments in which dislocation etch pitting was used to ascertain the depth of damage in crystals which were mechanically polished or which were cut with either a commercial metallographic cut-off wheel,* a com- All specimens were cut from single crystals of American Smelting and Refining Co. 99.999+ pct pure copper which were grown from the melt by the Bridge-man technique. The test specimens were disks, with faces being (111) planes and the disk axis a (111) direction. The disks were annealed in a vacuum of 10-5 Torr for 24 hr at 950°C prior to cutting or polishing and were given a light electropolishing in an ortho-phosphoric acid bath before etch pitting. Both Youngs1 and Livingston's2 reagents were used for etch pitting and the reagents gave identical quantitative results; however Livingston's reagent produced less staining and so all photomicrographs shown are of {111) surfaces etched with this solution. The surface of the annealed crystals showed well-defined subboundaries and a density of dislocations of about 1 X 106 per sq cm excluding those present in subboundaries, Fig. 1. The depth of cold work produced during mechanical polishing was determined after an annealed specimen was mounted in a paraffin holding block to protect it from extraneous damage. The exposed (111) surface was ground on metallographic papers and then polished on billiard cloth through 0.05-p alumina abrasive. It was necessary to remove about 0.3 mm (-0.01 in.) to obtain a structure representative of the annealed sur- face, indicating that the crystal was damaged to this depth during mechanical polishing. The cold work caused by standard cutting methods was measured in another series of tests in which cuts

Jan 1, 1967

By E. A. G. Colls

IN all branches of the chemical industry, corrosion plays a very costly part unless it is suitably com-batted, and as a result it is probably correct that chemical and design engineers are more corrosion conscious in the field of chemical industry than in others. Most metals occur in nature in combination with other elements. The refined or reduced state to which man converts them for his use, by removing the combining elements, leaves them in an unstable condition. Therefore in most of the media to which the metals are exposed they are constantly combining with the constituents of their environment, or in other words they are continually being corroded. Similarly, nonmetallic materials are corroded by undergoing chemical change. The rate at which corrosion takes place varies widely from metal to metal and medium to medium. In practically all cases the corrosion of metals in solutions (electrolytes) is electrolytic in nature and the rate of corrosion is dependent on many factors such as temperature, pressure, internal stresses, galvanic action, metal-ion concentration, and so on. In the chemical industry substances must be handled which are particularly corrosive to materials of construction. At the chemical plants of The Consolidated Mining and Smelting Co. of Canada, Ltd. (otherwise known as Cominco), situated at Trail, B. C., Canada, the following are some of the materials that have to be handled: Gases. Sulphur dioxide, sulphur trioxide, carbon dioxide, carbon monoxide, oxygen, hydrogen fluoride, ammonia, hydrogen sulphide, and oxides of nitrogen. Liquids. Solutions of ammonium sulphate, ammonium sulphite, ammonium nitrate, caustic soda and potash, sulphuric acid, nitric acid, hydrofluo-silicic acid, hydrofluoric acid, phosphoric acid, aqua ammonia, and formic acid. Solids. Gypsum (containing phosphoric acid), ammonium sulphate, ammonium nitrate, phosphate rock, caustic soda, potash, and phosphate fertilizers.

Jan 1, 1951

By E. A. G. Colls

IN all branches of the chemical industry, corrosion plays a very costly part unless it is suitably com-batted, and as a result it is probably correct that chemical and design engineers are more corrosion conscious in the field of chemical industry than in others. Most metals occur in nature in combination with other elements. The refined or reduced state to which man converts them for his use, by removing the combining elements, leaves them in an unstable condition. Therefore in most of the media to which the metals are exposed they are constantly combining with the constituents of their environment, or in other words they are continually being corroded. Similarly, nonmetallic materials are corroded by undergoing chemical change. The rate at which corrosion takes place varies widely from metal to metal and medium to medium. In practically all cases the corrosion of metals in solutions (electrolytes) is electrolytic in nature and the rate of corrosion is dependent on many factors such as temperature, pressure, internal stresses, galvanic action, metal-ion concentration, and so on. In the chemical industry substances must be handled which are particularly corrosive to materials of construction. At the chemical plants of The Consolidated Mining and Smelting Co. of Canada, Ltd. (otherwise known as Cominco), situated at Trail, B. C., Canada, the following are some of the materials that have to be handled: Gases. Sulphur dioxide, sulphur trioxide, carbon dioxide, carbon monoxide, oxygen, hydrogen fluoride, ammonia, hydrogen sulphide, and oxides of nitrogen. Liquids. Solutions of ammonium sulphate, ammonium sulphite, ammonium nitrate, caustic soda and potash, sulphuric acid, nitric acid, hydrofluo-silicic acid, hydrofluoric acid, phosphoric acid, aqua ammonia, and formic acid. Solids. Gypsum (containing phosphoric acid), ammonium sulphate, ammonium nitrate, phosphate rock, caustic soda, potash, and phosphate fertilizers.

Jan 1, 1951

By John L. Schroder

In selecting the best system of mining for a particular operation, many different factors must be considered. The system to be finally selected should be that which provides: 1) The highest possible degree of safety for mine personnel. 2) The lowest cost per ton of product. 3) The maximum coal production per man-shift. 4) The most suitable quality of final product, considering its intended use. 5) The maximum percent recovery of coal per acre of reserve consistent with cost and subsidence rights. 6) Consideration for the ecology of the area. Some of the important factors to be considered when choosing a method of mining are: 1) Amount of cover over the coal seam. 2) Type of the rock in the overburden. 3) Characteristics of the coal seam including: (a) the thickness of the coal seam; (b) the nature and location of any impurities or irregularities; (e) the dip (or pitch) of the coal seam; (d) the nature and direction of any definite cleavage ill the czoa1 seam; (e) the hardness of the coal; (f) the structural strength of the coal; and (g) the presence, anti amount, of explosive gas (methane). 4) Quantity of water likely to be encountered in the mining operation. 5) Nature and strength of the roof (top) over the coal seam. 6) Nature and strength of the floor (bottom) under the coal seam. 7) Any previous or concurrent mining in seams above or below the coal seam to be worked. Information on items 1-7 may be obtained in several ways. Topographical and geological reports and maps of the area are generally available

Jan 1, 1973

By H. R. Banks

The Sullivan concentrator has completed 20 years of operation. During this period a considerable amount of data has been accumulated concerning the characteristics of several types of flotation machines in their application to the problem of the differential separation of the lead sulphide, zinc sulphide and, in more recent times, iron sulphide, in the ore from the Sullivan mine. It is the author's intention to sketch briefly experiences encountered when the several types of flotation machines were introduced into the flow. Original Flotation Equipment and Ore The original flotation equipment consisted of four 18-cell lead-roughing machines, whose concentrate was cleaned in an 8-cell and recleaned in a similar 8-cell machine. Zinc concentration was carried out in four 18-cell machines. One 8-cell zinc re-treatment machine received the reground zinc middling. The 168 cells handled some 3000 tons of original daily feed. These cells were of the standard Minerals Separation type, equipped with 24-in. impellers. Spindles were driven through geared line shaft at a speed of 255 r.P.m. The impellers were the 45' type, except for the last three cells of the zinc-rougher machines, which were of sub-aeration type, with full bottom shroud and half shroud for the top side of the impellers. Four-pound air was introduced. This recognition of the benefit of intensified flotation operation for "gleaning" was an important phase in the early operation and will be discussed further on in this paper. Sullivan ore during this period is described as a finely disseminated mixture of four sulphides, totaling go per cent made up of 13.6 per cent galena, 14.4 per cent mar-matite, I per cent pyrite and 61 per cent pyrrhotite. The specific gravity of the ore was approximately 4.4. There has been a gradual change in the ore content. The 10 per cent of nonsulphide constituents has increased to between IS and 20 per cent and all three sulphides have dropped somewhat. Added equipment and changing technique have made possible the treatment of 8000 tons per day of mill feed instead of the 3000 originally handled. Special Features of Flotation at Sullivan Sullivan flotation differs greatly from customary practice. The very heavy return of lead rougher middling and lead cleaner tailing, totaling at times 125 per cent of the new feed tonnage, has been the subject of much investigation. The practice is still employed. This operating condition is mentioned because it is the author's belief that the in-

Jan 1, 1947

By H. R. Banks

The Sullivan concentrator has completed 20 years of operation. During this period a considerable amount of data has been accumulated concerning the characteristics of several types of flotation machines in their application to the problem of the differential separation of the lead sulphide, zinc sulphide and, in more recent times, iron sulphide, in the ore from the Sullivan mine. It is the author's intention to sketch briefly experiences encountered when the several types of flotation machines were introduced into the flow. Original Flotation Equipment and Ore The original flotation equipment consisted of four 18-cell lead-roughing machines, whose concentrate was cleaned in an 8-cell and recleaned in a similar 8-cell machine. Zinc concentration was carried out in four 18-cell machines. One 8-cell zinc re-treatment machine received the reground zinc middling. The 168 cells handled some 3000 tons of original daily feed. These cells were of the standard Minerals Separation type, equipped with 24-in. impellers. Spindles were driven through geared line shaft at a speed of 255 r.P.m. The impellers were the 45' type, except for the last three cells of the zinc-rougher machines, which were of sub-aeration type, with full bottom shroud and half shroud for the top side of the impellers. Four-pound air was introduced. This recognition of the benefit of intensified flotation operation for "gleaning" was an important phase in the early operation and will be discussed further on in this paper. Sullivan ore during this period is described as a finely disseminated mixture of four sulphides, totaling go per cent made up of 13.6 per cent galena, 14.4 per cent mar-matite, I per cent pyrite and 61 per cent pyrrhotite. The specific gravity of the ore was approximately 4.4. There has been a gradual change in the ore content. The 10 per cent of nonsulphide constituents has increased to between IS and 20 per cent and all three sulphides have dropped somewhat. Added equipment and changing technique have made possible the treatment of 8000 tons per day of mill feed instead of the 3000 originally handled. Special Features of Flotation at Sullivan Sullivan flotation differs greatly from customary practice. The very heavy return of lead rougher middling and lead cleaner tailing, totaling at times 125 per cent of the new feed tonnage, has been the subject of much investigation. The practice is still employed. This operating condition is mentioned because it is the author's belief that the in-

Jan 1, 1947

By J. F. Lewis

BELIEVING that one of the essential points in mining, as in all other business, is to know the expense incurred in each particular department, I have carefully kept an account with each department for the past three years; and, as it may be of interest to some of our members, I herewith present it to the Institute, reduced to percentages of the total yearly expense, showing the cost for materials, repairs, expenses, tools, team accounts, powder, oil, and fuel, also for labor under its several heads :

Jan 1, 1878

By Willard H. Tracy

The method of seismic reflection prospecting has many times been compared to sound ranging, a process that became familiar to many during the World War. According to this very simple theory, the dynamite goes off and sends out a compression wave, which meets a reflecting horizon and returns to the surface, where it is recorded and the elapsed time of its travel in the earth accurately determined. Computations are then made on the general theory that the longer the elapsed time, the greater the depth of the reflecting bed. While this serves to give an idea of the fundamental basis of the process, it suggests a simplicity that does not exist in the life history of the various waves set up by a dynamite explosion in the earth. To begin with, a seismic wave in the earth does not obey the same simple laws of propagation that apply to a sound wave in the air. The property of strength in shear possessed by solids introduces a factor that sets such waves apart from the ordinary air waves. Also, the transmission charactcristics of the earth vary widely from place to place, and a fairly accurate knowledge of the space relationships of these variations is necessary if the final results are to be understood. Besides the waves recorded and used in the reflection computations, there are many

Jan 1, 1940

By Willard H. Tracy

The method of seismic reflection prospecting has many times been compared to sound ranging, a process that became familiar to many during the World War. According to this very simple theory, the dynamite goes off and sends out a compression wave, which meets a reflecting horizon and returns to the surface, where it is recorded and the elapsed time of its travel in the earth accurately determined. Computations are then made on the general theory that the longer the elapsed time, the greater the depth of the reflecting bed. While this serves to give an idea of the fundamental basis of the process, it suggests a simplicity that does not exist in the life history of the various waves set up by a dynamite explosion in the earth. To begin with, a seismic wave in the earth does not obey the same simple laws of propagation that apply to a sound wave in the air. The property of strength in shear possessed by solids introduces a factor that sets such waves apart from the ordinary air waves. Also, the transmission charactcristics of the earth vary widely from place to place, and a fairly accurate knowledge of the space relationships of these variations is necessary if the final results are to be understood. Besides the waves recorded and used in the reflection computations, there are many

Jan 1, 1940

By G. R. St. Pierre, R. D. Blackburn

Oxygen contents of' liquid-iron alloys saturated with oxides are analyzed. Minimum points observed in particular Fe-X-O systems can be predicled by a simple extension of first-order interaction methods. If minimum oxygen content occurs at N; where r is the ratio of metal to oxygen in the oxide phase. RECENTLY, wisher' reported on solubility measurements of A1203 in liquid iron at 1580°C which support the earlier work of d'Entremont, Guernsey, and chipman2 and Gokcen and Chipman. Swisher's diagram is reproduced in Fig. l. Minimum points in oxide solubilities have also been found in the Fe-Cr-0 system,4 Fig. 2, and the Fe-Ti-0 system,' Fig. 3. Minima positions can be used to confirm approximately the measured first-order interactions, &, cgr, and E&~, in liquid iron and to deduce compositions of components of constant activity in the oxide phases. Consider the solution of Alz03 in liquid iron: for which an equilibrium constant can be written as: differentiating Eq. [2] with respect to Na~, the atom fraction of &l in the metallic solution, and noting that If the activities of Al and 9 are expanded by a first-order interaction model, then:

Jan 1, 1969

By G. Donald Emigh

Nothing is more important to life-plant and animal-than phosphate. Its compounds are essential to the energy functions of all living systems and for the formation of bones and teeth. Animals get their phosphate from eating plants and other animals, or domestically from feed supplements. Plants get their phosphates from the soil. Man's most important use of phosphate is for fertilizer; approximately 95% of the world's phosphate rock production is consumed by fertilizers. Most of the balance is processed in electric furnaces into elemental phosphorus, the important raw material for making industrial phosphates. Recovery of uranium from phosphates has been possible but not widely used. However, recent significant developments have generated interest in such recovery in the US and elsewhere. Phosphate occurs in all igneous and sedimentary rocks, and in all fresh and salt water. However, economical recovery is limited to deposits where natural concentration of the phosphate mineral has occurred. Occasionally natural concentration is great enough that the material can be used as mined; generally, however, the ore is low grade_ and must be concentrated. Phosphate rock is produced in 31 countries. Fig. 1 shows the location of major phosphate rock producers as well as some of the known phosphate deposits not yet in production. In the last decade the world phosphate industry has experienced steady growth. World production rose from 98 Mt of phosphate rock in 1973 to 140 Mt in 1982. Fig. 2 shows the growth curve of rock production and graphically illustrates the almost straight-line rise since 1945 in both US and world production. Table 1 gives the breakdown, by countries, of world rock production, 1974 through 1979. Table 2 shows US rock production by producing areas. Definitions of Terms Used in the Phosphate Industry Phosphate Rock: Commonly called rock in sedimentary deposits and apatite in igneous deposits. Those expressions generally include any mined, or mined and beneficiated, fluorine-containing calcium phosphate used as the raw material for the next stage of manufacturing. The average phosphate content in rocks is 0.1 to 0.2% P2O5, as documented by McKelvey (1973). About 200 minerals contain more than 1 % P2O5. However, the important mineral in igneous rocks is fluorapatite, [Ca5 (PO4),3 F], containing about 42% P205 and 3.8% F2; in sedimentary rocks the important mineral is francolite, a carbonate fluorapatite containing up to 2% molecular CO2. Both are in the apatite family of minerals. Most phosphate rock, whether beneficiated or not, is a fine-grained material. The expression phosphate rock has no relation to its phosphate content. For example, phosphate rock from Idaho used in the production of phosphorus may contain about 24% P205, whereas rock from Morocco may contain 36.6% P2O5. Phosphorite: A deposit of phosphate directly or indirectly of sedimentary origin, which is of economic interest. Grade of Phosphate Rock: The calcium phosphate content of phosphate rock is expressed in different world areas by one of the following terms: BPL (bone phosphate of lime) TPL (triphosphate of lime) P2O5 (phosphorus pentoxide) P (phosphorus-not commonly used) An illustration of relationship is: 80% BPL = 80% TPL = 36.6% P5O2 = 16% P

Jan 1, 1983

By Simon D. Strauss

The world appetite for minerals in the, third quarter of this century grew at a higher rate than had been anticipated. To illustrate, consider the experience of four, commodities. Excluding the Communist bloc, sometimes referred to as the centrally planned economies, demand for aluminum increased at a compound rate of 8.6% between 1950 and 1975,; copper rose by 4.4%; iron ore by 5.5%; and tin, the laggard in the group, by 2%. Except for tin, the figures are substantially greater than growth rates anticipated in 1950 in the Paley Commission report and other studies. The growth rate was not evenly distributed in geographical areas. Professor Wilfred Malenbaum of the University of Pennsylvania did an interesting study breaking these figures down as among three principal sources of demand -- the United States, other industrialized nations (which he referred to as the "rich lands"), and the developing world (which he referred to as the "poor lands").

Jan 1, 1982

By E. W. Parker

THE anthracite region, from which there is produced annually about 80,000,000 tons, or approximately 15 per cent. of the total coal supply of the United States, has a combined area of a little less than 500 sq. mi. The total area occupied by the bituminous fields (including the sub-bituminous and lignite fields) is in the neighborhood of 400,000 sq. mi., so that 15 per cent. of the total output comes from this small area of only a little more than 0.1 per cent. of the coal-producing territory. of the United States. The productive anthracite area is divided into a series of basins or troughs, roughly parallel, extending. in a northeast-southwest direction through the. Counties

Jan 1, 1921

By A. V. Deforest, C. W. Macgregor, A. R. Anderson

One of the important problems in the design of structures and machine parts subjected to rapidly applied loads is the determination of the strength and ductility of the material itself under such conditions. Realizing the need for such information, many investigations have been carried out in the past. Most of these experiments have been made using notched bars in bending either with the Charpy or Izod impact machine. While yielding valuable data on the effect of notches in the energy absorption of the material and on the condition of heat-treatment, this form of test does not lend itself readily to a determination of fundamental stress-strain relations. For this and other reasons, more attention has been paid recently to the tension impact test. An extensive literature already exists on the subject and only those investigations somewhat closely related to the present paper will be mentioned. For a more comprehensive list, the reader is referred to the Symposium on Impact Testing or the A.S.T.M., 1938. The work of Mann.' Clark and Dätwyler,2 Nádai and Manjoine,3 Winlock and Leiter,4 Deutler,5 and Brinkmann,6 however, deserves especial mention. In most of the previous investigations on the subject, when stress-strain relations were obtained under high rates of loading, it was the common procedure to determine stresses based on the original area and strains based on the original length. Stress-strain curves were then constructed by P ALo plotting So = 1/A0 as a function of eo = ALr,o where A0 and Lo refer to the original area and gauge length, respectively. At present there exists a paucity of true stress-strain data in the impact problem. The advantages of constructing so-called true stress-strain curves in order to reveal the fundamental physical properties of the material for the tension test were discussed recently by one of the authors.7'8 It was shown that the true physical behavior of the material in the tension test could best be represented P by plotting the average true stress, S = 2P as a function of 6 = q' = log —r = log ~9L where P, A, L, S, E, and q' refer to the load, the cross-sectioned area while the load P is applied, the actual gauge length, the average true stress, the true strain and true reduction in area, respectively. Besides giving a better physical representation, the method has certain additional advantages in that the stress-strain curve so plotted becomes a straight line from the maximin load point to fracture. The construction of such curves, however, while comparatively simple for the slow rates of loading customarily used in the tension test, presents certain dificulties for tensile impact in that both loads and diameters are required throughout the test. The continuous measurement of test-piece diameters to fracture under impact conditions offers considerable experimental difficulty. In order to make it feasible to

Jan 1, 1942

By A. V. Deforest, A. R. Anderson, C. W. MacGregor

One of the important problems in the design of structures and machine parts subjected to rapidly applied loads is the determination of the strength and ductility of the material itself under such conditions. Realizing the need for such information, many investigations have been carried out in the past. Most of these experiments have been made using notched bars in bending either with the Charpy or Izod impact machine. While yielding valuable data on the effect of notches in the energy absorption of the material and on the condition of heat-treatment, this form of test does not lend itself readily to a determination of fundamental stress-strain relations. For this and other reasons, more attention has been paid recently to the tension impact test. An extensive literature already exists on the subject and only those investigations somewhat closely related to the present paper will be mentioned. For a more comprehensive list, the reader is referred to the Symposium on Impact Testing or the A.S.T.M., 1938. The work of Mann.' Clark and Dätwyler,2 Nádai and Manjoine,3 Winlock and Leiter,4 Deutler,5 and Brinkmann,6 however, deserves especial mention. In most of the previous investigations on the subject, when stress-strain relations were obtained under high rates of loading, it was the common procedure to determine stresses based on the original area and strains based on the original length. Stress-strain curves were then constructed by P ALo plotting So = 1/A0 as a function of eo = ALr,o where A0 and Lo refer to the original area and gauge length, respectively. At present there exists a paucity of true stress-strain data in the impact problem. The advantages of constructing so-called true stress-strain curves in order to reveal the fundamental physical properties of the material for the tension test were discussed recently by one of the authors.7'8 It was shown that the true physical behavior of the material in the tension test could best be represented P by plotting the average true stress, S = 2P as a function of 6 = q' = log —r = log ~9L where P, A, L, S, E, and q' refer to the load, the cross-sectioned area while the load P is applied, the actual gauge length, the average true stress, the true strain and true reduction in area, respectively. Besides giving a better physical representation, the method has certain additional advantages in that the stress-strain curve so plotted becomes a straight line from the maximin load point to fracture. The construction of such curves, however, while comparatively simple for the slow rates of loading customarily used in the tension test, presents certain dificulties for tensile impact in that both loads and diameters are required throughout the test. The continuous measurement of test-piece diameters to fracture under impact conditions offers considerable experimental difficulty. In order to make it feasible to

Jan 1, 1942

By W. T. Turrall, M. J. Cook

A discussion of modern developments in beneficiation of fine sizes of anthracite, this paper includes a description of the plant flowsheet, an analysis of operating results, and a summary of fundamentals of mineral separation relative to plant operation. DURING the past several years Lehigh Naviga-tion Coal Co. has installed equipment at Tamaqua and Lansford collieries for cleaning and sizing No. 4 buckwheat —3/32 + 3/64 in. and for recovering and cleaning flotation coal —20 + 200 mesh at Tamaqua colliery. Papers describing some of these installations have been presented to AIME. At Coaldale colliery, however, methods used to clean fine coal were inadequate and inefficient. Management decided upon a thorough investigation of all existing processes before building a plant to treat the combined three sizes mentioned. Investigation, carried out on company property and at other plants, entailed a study of hydrotators, hydroclassifiers, tables, spirals, flotation machines, methods of screening, and methods of dewatering. On the basis of this investigation a flowsheet was designed which necessarily excluded many processes in use, and the writers wish to emphasize that no criticism is implied by omission of processes or machines. A determining factor in selection of many machines was the policy of standardizing equipment wherever possible. Flowsheet and Operational Data The first principle to be considered in designing of any plant is efficiency of cleaning as related to laws of classification. Beneficiation of coal may be described as separation of two materials having different specific gravities. Although there is an inherent ash content even in the purest coal which slightly affects its specific gravity, it is recognized that many particles are true middlings. The percentage of these particles allowable in the final product depends upon the ultimate ash, or specifications of the consumer. Richards in his study of free settling and hindered settling classification' determined that particles of equal size and different specific gravities had unequal settling velocities. He also determined a definite size relationship for equal settling velocities with free settling and hindered settling conditions. Considering the design of machines used to clean No. 4 and No. 5 buckwheat, it may be assumed that both free settling and hindered settling conditions exist and that ratio of size for practical operations is between the established values. The essential factor is that the more efficiently and closely sized the feed is maintained, the more nearly perfect the resulting separation. Flowsheet design was governed primarily by factors related to the 1200 to 1500 tons per hr feed to the main plant. It should be stressed that because of the many sources of supply from mine and stripping, the physical characteristics of this feed varied considerably. The most significant influence was varying percentage of fines, necessitating that all machines be capable of operating under maximum peak load during periods of surge. Since cleaning practice is a wet process, about 9000 gal per min containing 14 to 15 pct solids, or 350 tons per hr, must be treated. This slurry contained all the fines, or —3/32 in., but also percentages of oversize, up to 1 % in., dependent on spills or breaks in screen jackets, a not uncommon occurrence in preparation plant practice. The flowsheet developed is shown in Fig. 1. Circled numbers represent points of sampling. Table I gives operational data including size, ash by size, composite ash, rate of flow in gallons per minute, percent solids dry weight, and average tons of solids per hour. It should be noted that these results are subject to human error in sampling practice. Detailed information reported is a representative evaluation of plant operation.

Jan 1, 1954