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By Ernest A. Hersam

The rate of output of a rock crusher is based upon a certain space relation, the calculation requiring that the size and position of the jaws, the principle of motion, and the speed of the machine be known. The result is a calculated maximum output. The purpose of this paper is to develop a method of calculating this maximum output, to judge the general applicability or utility of such a calculation, and, so far as possible, to lecord calculated values as a basis for the comparison of actual results, or for estimating the capacity of a new crusher or of a standard crusher working under new conditions. A method for calculating the capacity of crushing rolls, which has been in common use for a long time, is well presented by R. H. Richards.' The output is conceived as a ribbon of rock, of which the breadth, thickness and length are governed respectively by the width of the rolls, the space between them, and their peripheral velocity. The weight of the rock thus crushed in a given time can be calculated from its specific gravity, after applying a factor representing the percentage of voids in the hypothetical ribbon. The calculation of crusher capacity is made in a somewhat similar manner. While the action of rolls is simple, with few irregularities in operating conditions, in rock crushers the material advances intermittently, usually under the force of gravity alone, and is subjected to a variety of variable conditions. The effect of these variable influences upon the calculation of capacity is now to be shown. In this paper, capacity will be discussed quite apart from any consideration of mechanical efficiency; that is, results will be stated not in terms of output per horsepower, but of output for a given machine when operated at a known speed, constructed and adjusted to receive material of a known size, and to yield a product having a definite maximum coarseness.

Jan 1, 1923

By Ernest Hersam

THE rate of output of a rock crusher is based upon a certain space relation, the calculation requiring that the size and position of the jaws, the principle of motion, and the speed of the machine be known. The result is a calculated maximum output. The purpose of this paper is to develop a method of calculating this maximum output, to judge the general applicability A utility of such a calculation, and, so far as possible, to record calculated values as a basis for the comparison of actual results, or for estimating the capacity of a new crusher or of a standard crusher working under new conditions. A method for calculating the capacity of crushing rolls, which has been in common use for a long time, is well presented by R. H. Richards.1 The output is conceived as a ribbon of rock, of which the breadth, thickness and length are governed respectively by the width of the rolls, the space, between them, and their peripheral velocity. The weight of the rock thus crushed in a given time can be calculated from its specific gravity, after applying a factor representing the percentage of voids in the hypothetical ribbon. The calculation of crusher capacity is made in a somewhat similar manner. While the action of rolls is simple, with few irregularities in operating conditions, in rock crushers the material advances intermittently, usually under the force of gravity alone, and is subjected to a variety of variable conditions. The effect of these variable influences upon' the calculation of capacity is now to be shown. In this paper, capacity will be discussed quite apart from any consideration of mechanical efficiency; that is, results will be stated not in terms of output per horsepower, but of output for a given machine when operated at a known speed, constructed and adjusted to receive material of a known size, and to yield a product having a definite maximum coarseness.

Jan 7, 1922

By Ernest A. Hersam

The rate of output of a rock crusher is based upon a certain space relation, the calculation requiring that the size and position of the jaws, the principle of motion, and the speed of the machine be known. The result is a calculated maximum output. The purpose of this paper is to develop a method of calculating this maximum output, to judge the general applicability or utility of such a calculation, and, so far as possible, to lecord calculated values as a basis for the comparison of actual results, or for estimating the capacity of a new crusher or of a standard crusher working under new conditions. A method for calculating the capacity of crushing rolls, which has been in common use for a long time, is well presented by R. H. Richards.' The output is conceived as a ribbon of rock, of which the breadth, thickness and length are governed respectively by the width of the rolls, the space between them, and their peripheral velocity. The weight of the rock thus crushed in a given time can be calculated from its specific gravity, after applying a factor representing the percentage of voids in the hypothetical ribbon. The calculation of crusher capacity is made in a somewhat similar manner. While the action of rolls is simple, with few irregularities in operating conditions, in rock crushers the material advances intermittently, usually under the force of gravity alone, and is subjected to a variety of variable conditions. The effect of these variable influences upon the calculation of capacity is now to be shown. In this paper, capacity will be discussed quite apart from any consideration of mechanical efficiency; that is, results will be stated not in terms of output per horsepower, but of output for a given machine when operated at a known speed, constructed and adjusted to receive material of a known size, and to yield a product having a definite maximum coarseness.

Jan 1, 1923

By Ernest Darby

WHEN bronze is melted in open-flame furnaces a considerable amount of slag is formed during the melting operation. This slag may be incidental to the melting practice or it may be formed intentionally by slag-forming constituents added to the furnace charge to provide a covering for the melted metal. When this slag is removed from the furnace, it contains, in addition to the free metal carried with it by the skimming operation, a considerable amount of metal as oxide either combined or mechanically mixed with it. By the usual crushing and washing methods this metallic oxide generally goes to the tailings pile, so diluted by other foundry waste that its recovery is economically impossible. If this furnace slag is not mixed with other foundry waste, practically all of the metal oxide as well as the free metal may be recovered by some form of smelting operation. The first side of the problem to be considered is the amount of slag produced. It may not be true that the majority of foundries have no record of the amount of slag made, but it is certainly true that a very great many either have no record or pay little attention to it. Usually the collection of furnace slag for one normal week's run will be sufficient to determine the advisability of its being handled in a different manner from the crushing and concentrating generally employed. If a large representative sample of the accumulation is crushed and concentrated and the recovery compared with the results of a careful assay, it will be found that a large percentage of the total metal content was lost in the washing process. The percentage of loss will be greater than the metallic oxide content, as some free metal in extremely fine particles always is carried away in grains of slag: From such a comparison, it may be determined whether or not the slag should be melted, sold or treated as before. An example of an actual test of this kind is given below.

Jan 1, 1928

By Horace Knerr

The term. "high-yield-strength," used in the title of Dr. Gillett's paper (p. 40) is obviously relative. His discussion is limited to improved steels intended to compete with the low-cost, low-carbon, hot-rolled, sheet and plate steels of commerce made and used on a tonnage basis, without heat-treatment. In his list of about three dozen steels, only three have a yield strength of 70,000 lb. per sq. in., or over. Double such values are not uncommon in aircraft steels. Dr. Jeffries (p. 21) refers to "light-weight metals," obviously meaning strong alloys of low specific gravity; namely, aluminum alloys of the duralumin type and certain magnesium alloys. In a structural material, "lightness" is determined by two factors, strength and specific gravity. They must always be considered jointly. The basis of comparison is a strength-weight ratio, obtained by dividing the desired strength value, such as tensile strength, yield strength, or endurance limit, by weight per unit of volume, such as specific gravity or pounds per cubic inch1. For example, aluminum is a heavy metal, structurally, unless alloyed and heat-treated to give it high strength. When the strength of a structural metal is raised by heat-treatment or by cold-work, its specific gravity is not appreciably changed, but it is made lighter in direct proportion to the increase in strength because less of it will be required to carry the load. The lightness of the finished structure of adequate strength is the real point of interest. This structure must not only carry designed load, but "stand the gaff" of service, which includes the effects of accidental overload, fatigue, corrosion, loosening of joints, and so forth. Neither Dr. Gillett nor Dr. Jeffries mentions the true "lightest material of construction," which is alloy steel, tubular in form (Fig. 1), assembled by welding and heat-treated to a yield strength in excess of 150,000 lb. per sq. inch.

Jan 1, 1936

By Howard Scott

Invar is the preeminent low-expansion metal by virtue of the fact that it can be prepared with a zero coefficient of expansion at atmospheric temperature. This fact suggests that there is little room for improvement in the expansion properties of the low-expansion nickel steels. The inference is true, however, only so far as the expansion at and near atmospheric temperature is concerned, because the expansivity of invar starts to increase rapidly on heating above 100" C. and soon reaches the value of copper. Guillaumel met this situation by increasing the nickel content above that of invar. By that expedient, alloys having low expansivity under higher temperatures were obtained, but not without a large increase in minimum expansivity. The increase in minimum expansivity with increasing nickel content severely limits the technical applications of these alloys at high temperatures. Prospects of improving the expansion characteristics of the nickel steels is offered by alloying. Search for an advantageous alloying addition by analogy with other alloy systems, however, is not productive because the low-expansion characteristic is unique with that system. The rule of mixtures usually gives a fair value of the expansivity of other solid-solution alloys, but in the iron-nickel systems gives a value of 18 X 10-6 per deg. C. whereas the actual value is 1 X 10-6 per deg. C. Apparently suitable additions are not to be deduced from such ingenuous considerations. Recognition of the fact that the temperature range of low expansivity in nickel steels is terminated with loss of magnetism affords a more promising basis for the selection of an advantageous element. One may expect from that fact that additions of nonmagnetic elements to the iron-nickel alloys are detrimental to the low-expansion characteristic. Indeed, carbon, manganese, silicon, copper and chromium are detrimental to the expansion properties and no nonmagnetic element is reported to be beneficial. From the same viewpoint, the addition of a magnetic metal offers prospects of improvement. As two of the three ferromagnetic elements are already present in the

Jan 1, 1930

By J. C. Wilhoit, J. B. Cheatham

Although an oil well is a long cylindrical hole with an irregular bottom, it appears likely that the nature of the stress concentration at the bottom of the hole can be ascertained from an analysis of the stresses around a short cylindrical cavity with rounded comers and smooth bottom. Such a cavity is studied primarily because it leads more readily to a solution to the problem by the use of stress functions. In this paper the stress distribution around a short cylindrical cavity subjected to bit loading, overburden and drilling-fluid pressures is determined by means of an analytical solution which approximately satisfies the boundary conditions of the problem. From this solution the stresses at the corner of the hole are calculated to be about 35 per cent lower than comparable results obtained by photoelastic and relaxation analyses. This difference is apparently due to the large radius of curvature at the corner of the cavity in the present analysis. Since good agreement is obtained between the results of this analysis and the stresses calculated for a similar loading on a semi-infinite elastic solid, it is concluded that the bit action in the region near the center of the hole is not appreciably affected by the presence of the sides of the hole. INTRODUCTION Much has been written concerning drilling "under down-hole conditions" and pertaining to the stress distribution in the rock at the bottom of an oil well.1-5 For example, it is known that identical rocks can be drilled more rapidly at the surface than under subsurface conditions of pressure and stress.6 Information on the behavior of rocks under loading can be obtained from triaxial test data.7-9 From such tests it is found that rocks exhibit brittle failure when the confining pressure and pore pressure are equal, but the mode of failure may change to ductile as the difference between the confining pressure and the pore pressure is increased. Brittle failure implies that there is very little permanent deformation before fracture, whereas ductile failure indicates that permanent deformation takes place before fracture. Some rocks are ductile at differential pressures of 5,000 psi , but other rocks are brittle even at differential pressures of more than 50,000 psi. Cuttings embedded in mud at the bottom of the hole may act as a plastic mass which the bit teeth must penetrate in order to attack the virgin rock below. 10 During drilling, the mud pressure acts as the confing pressure, and in many cases the difference between the mud pressure and the formation pore pressure IS sufficiently low so that the rock most likely falls in a brittle manner. Very little penetratiori by the bit teeth may be required for brittle failure of the rock. For these brittle materials, the elastic stress distribution is of practical interest in determicing the possible effects of a given loading on failure. The penetration of bit teeth into ductile or plastic rock has been analyzed previously ll,12 and will not be considered further in the present work. During actual drilling, many teeth act at various points ovel an irregular hole bottom. In the present analysis a solution is obtained for an idealized problem of determining the elastic stress distribution caused by only one tooth acting alone at the center of a smooth hole bottom. It obviously is not proposed that any driller should put a special one-tooth bit on bottom, but it is hoped that extensions of the simpler problems can eventually lead to a better understanding of more complex actual drilling phenomena. To obtain a solution by the use of stress functions, a short cylindrical cavity with rounded corners and smooth bottom is studied. The solution to this problem should give an insight into the nature of the stress concentration at the bottom of an oil well which is in reality a long cylindrical hole with an irregularr bottom. After selection of the proper curvilinear co-ordinate system, the stress functions are expressed as series of Legendre polynomials. The coefficient of each term in the series is then determined to satisfy the boundary conditions at a finite number of discrete points on the boundary of the cavity with least square error. Results are compared with bottom-hole stresses obtained by photoelastic and relaxation analyses.

By F. H. Callaway, W. O. Keller

The various theories as to the well spacing-recovery relationship are reviewed in considerable detail and these theories analyzed in terms of their consistency with modern reservoir engineering concepts. It is concluded that the well spacing problem must be analyzed in terms of recovery efficiency and that a positive answer to the relation between well density and recovery efficiency is not available from direct comparisons of the production histories of wells and fields. The results of an engineering analysis designed to permit approximate calculation of recovery efficiencies as a function of well spacing in a depletion type reservoir from basic reservoir data is presented. Results of this type analysis indicate that the effect of well spacing on recovery efficiency in depletion type reservoirs can be expected to be very small. Limitations of this approach are pointed out, particularly with respect to its application in lenticular reservoirs. Testing techniques are outlined which should indicate whether or not a reservoir is continuous between wells and whether or not satisfactory drainage is being obtained with present spacings. A mass of data of this type indicates continuity to exist in most fields. INTRODUCTION The purpose of this paper is to review critically the engineering aspects of the well spacing problem, both from the standpoint of certain concepts and from the standpoint of reservoir mechanics. The well spacing problem is primarily an economic problem in which the optimum well density for a particular field is that density which will yield the greatest oil recovery consistent with justifiable development costs. The well spacing answer in terms of economic conditions, however, is extremely sensitive to the variation in recovery efficiency with well density. The variation in recovery efficiency with 'References given at end of paper. Manuscript received at the office of the Petroleum Branch October 2, 1949. Paper presented at the Petroleum Branch Meeting in San Antonio. Texas, October 5-7. 1949. well density is properly an engineering problem. Different opinions as to the correct answer to this engineering problem is the basis for most of the wide difference in opinion among various members of the industry as to optimum well spacing. This paper will be confined to the engineering problem of the relation between well density and ultimate oil recovery; economic considerations necessary for the evaluation of optimum well density for any particular field will not be discussed. The paper can be logically divided into two parts. The first part deals with a critical examination of the background and logic of the Cutler Rule and of similar studies by other authors and of related well spacing concepts. It is indicated that the variations in recoveries with well density* observed by Cutler and. others can be logically attributed to regional migration. Theoretical justification of the Cutler type relation wherein observed variations in recovery with well density in the same field is attributed to variations in recovery effiiency, in terms of energy relations, is refuted. The second part consists of a review of concepts of reservoir mechanics with regard to the well density-recovery relation. It is indicated that little variation of recovery efficiency with well density can be expected in a depletion type reservoir, unless lenticular conditions prevent communication between wells. The significance of field test data with regard to the existence or non-existence of lenticular conditions is pointed out. THE CUTLER RULE The first published article concerning the engineering aspects of the well spacing problem to receive wide attention was the work of W. W. Cutler' of the U. S. Bureau of Mines, published in 1924. In a study of decline curves from a large *The expression "well density" as utilized herein refers to the number of acres attributed to each well in a uniform well pattern, and is expressed in acres per well. The term "well spacing" Is utilized to denote the average distance between adjacent wells in a uniform well pattern. †Although the Cutler rule is treated critically in this discussion the authors intend no personal criticism of W. W. Cutler or of his hark The currently accepted concepts of reservoir mechanics were no": existent at the time of Cutler's work, as were even the moat basic tools (such as the bottom hole pressure bomb) for observing reservoir behavior.

Jan 1, 1950

By Frederic Benard

The treatment of Balbach-Thum slimes at Copper Cliff by the Ontario Refining Co, is of interest because it differs considerably from methods usually employed for the recovery of fine gold from parting-plant slimes. Owing to the comparatively high percentages of palladium and platinum, wet methods are used to remover the greater proportion of these metals before electrolytic refining in the Wohlwill cells. The Plant The platinum-metals department, Wohlwill room, and gold-melting room extend along the north side of the silver refinery and are separated from the parting plant by a glass partition (Figs. 1 and 2). The platinum-metals department resembles a laboratory built on a large scale, with the various pieces of equipment laid out on terraces to facilitate handling. Because of the corrosive nature of the solutions, chemical stoneware is used throughout. Elevation of acids is accomplished by means of Mariotte bottles. On the top level are three steam-jacketed stoneware kettles of 50-gal. capacity, also a packed tower. One kettle is used for digesting the slimes while the remaining kettles are used for precipitating the gold. The dissolver is equippcd with a treated concrete hood, which is connected to the flue system. Gases are drawn off through the packed tower by means of a 6-in. stoneware exhaust fan. A 15 per cent solution of sodium carbonate is continually circulated through the tower. On the intermediate level are two suition filters, one for removing silver chloride and the other for the gold sand. The filter medium consists of an asbestos pad covered with a filter paper on which is a layer of twill. On the bottom level are two rectangular cementation tanks, 24 by 48 by 24 in. deep, and a suction filter used for removing the platinum-metal concentrates. The circulating pump for the packed tower is also here. Suction is provided by a vacuum pump having a capacity of 8 cu. ft. at 20-in. vacuum.

Jan 1, 1944

By L. S. Panyity

The State of Ohio is among the pioneers in the production of oil and gas. Numerous anticlinals, such as the Macksburg, Cow Run and Newport, have been thoroughly developed, and the pools found in connection with them are quite in accord with the structural theory. Numerous oil and gas pools found in the Berea sand, however, demand a different explanation. The study of these pools belongs to the sub-surface geologist, as it is possible to understand the factors controlling "off-structure" accumulations only after a careful study of well records. By carefully analyzing the various conditions over a large territory, it is possible to understand the otherwise meaningless mass of data that one may have at hand, and put it into tangible shape, from which various conclusions may be drawn. The territory here discussed includes Belmont, Guernsey, Muskingum, Noble, Monroe, Morgan, Washington, Athens and Meigs counties, containing the majority of the prolific oil and gas pools of the Carboniferous system in southeastern Ohio. The general dip of the strata is to the southeast, the entire territory lying on the northwestern flank of the Appalachian geosyncline. The best known oil- and gas-producing horizon in the territory is the Berea sand, which lies near the lower part of the Mississippian, with the Sun-burry shales (the coffee-shales of the driller) above, and the Bedford shales below it. The Bedford is underlain by the thick Ohio shales. The Ohio and Bedford contact is considered to be the dividing line between the Carboniferous and Devonian systems. The Berea is one of the most persistent of recognizable oil and gas horizons; its outcrop has always been found in its expected place, and it has always been penetrated whenever the drill went deep enough. It is not expected, however, even of the most uniform formations, that no lithological variations should occur, and the Berea is no exception. Nevertheless, there appears to be a certain regularity in its variation, the main features of which directly affect the accumulation of petroleum.

Jan 1, 1920

By L. S. Panyity

THE State of Ohio is among the pioneers in the production of oil and gas. Numerous anticlinals, such as the Macksburg, Cow Run and Newport, have been thoroughly developed, and the pools found in connection with them are quite in accord with the structural theory. Numerous oil and gas pools found in the Berea sand, however, demand a different explanation. The study of these pools belongs to the sub-surface geologist, as it is possible to understand the factors controlling "off-structure" accumulations only after a careful study of well records. By carefully analyzing the various 'conditions over a large territory, it is possible to understand the otherwise meaningless mass of data that one may have at hand, and put it into tangible shape, from which various conclusions may be drawn. The territory here discussed includes Belmont, Guernsey, Muskingum, Noble, Monroe, Morgan, Washington, Athens and Meigs counties, containing the majority of the prolific oil and gas pools of the Carboniferous system in southeastern Ohio. The general dip of the strata is to the southeast, the entire territory lying on the northwestern flank of the Appalachian geosyncline. The best known oil- and gas-producing horizon in the territory is the Berea sand, which lies near the lower part of the Mississippian, with the Sunburry shales (the coffee-shales of the driller) above, and the Bedford shales below it. The Bedford is underlain by the thick Ohio shales. The Ohio and Bedford contact is considered to be the dividing line between the Carboniferous and Devonian systems. The Berea is one of the most persistent of recognizable oil and gas horizons; its outcrop has always been found in its expected place, and it has always been penetrated whenever the drill went deep enough. It is not expected, however, even of the most uniform formations, that no lithological variations should occur, and the Berea is no exception. Nevertheless, there appears to be a certain regularity in its variation, the main features of which directly affect the accumulation of petroleum.

Jan 8, 1918

By Joseph E. Pogue

There are two methods employed in the development of oil pools. The older and dominant method is one in which the primary object is the protection of the underground deposit from drainage through competing wells, and considerations of efficiency of extraction and cost of production are subordinated thereto. The newer and less prevalent method is one in which maximum efficiency and minimum cost are the first objectives and developments to these ends may proceed undisturbed by the exigencies of competitive drainage. The second method has developed mainly in pools under single ownership and the term "unit operation" has come to be applied to this procedure. A single ownership, however, is not essential to the method, for unity of operation may be achieved by agreement under split ownership, or even by a concert of enlightened purpose. There are examples of unit operation where neither the ownership nor the management is a unit, but merely where unity of procedure has been attained, as in the Yates pool. Throughout this paper "unit operation" is used in its broad sense without implying sole ownership or single management, although unit operation is more conveniently attained where these conditions are present. It is evident, upon reflection, that the second method should yield results far superior to the first, for the work of exploitation can be conducted without extraneous considerations and the natural forces present in the oil reservoir can be utilized to maximum advantage. Experience has amply confirmed this conclusion and were the facts widely known and appreciated, the efforts to extend the applications of the principle of unitization would be greatly intensified. Competitive Development of Oil Pools It has come about that the vast majority of oil pools, or reservoirs, in the United States are subdivided by numerous surface tracts under separate ownerships. This condition arises from the prevalent practice in the oil business of acquiring prospective acreage in checkerboard spreads. Thus the discovery of oil usually reveals a mosaic of overlying ownership. Since oil is a migratory mineral and is subject to lateral

Jan 1, 1931

By Earl Oliver

Dean Roscoe Pound, of Harvard Law School, in addressing the A.I.M.E. Petroleum Division on Feb. 22, 1934, said, "When you are able to work out a program that is mechanically feasible, that is economicaIly advisable, and which seems in your judgment, which is just as good as that of anyone, to be politically wise, you will not have very much trouble in the end in inducing the courts of today to find that it is legally sound." The purpose of this paper is to show: first, legal conditions necessary to promote conservation and stabilization; and second, to suggest operating procedure when those legal conditions are established. The proposal is mechanically feasible and economically advisable. A growing public understanding should make it politically wise. The disappointing progress in the development of conservation and stabilization can be attributed to the lack of two legal concepts as integral parts of oil and gas law; i.e., (1) a practical substitute for the capture rule, (2) collective ownership control for the individual oil and gas pool. When these two concepts are established on an equitable basis, conservation and stabilization procedure will become a comparatively simple process, more or less automatic in its adaptation and operation. Establishing these concepts is the function of the law-making agencies and might well be left to them for discussion except that the mechanical processes that give them form and substance must first be developed by the engineer. A Substitute for the Capture Rule Much has been written on these subjects, but the most concrete statement that has come to the attention of this writer is the following from an article by Charles G. Haglund in the Kentucky Law Journal of May, 1934: The Oxford1 case is not only authority for the proposition that it is competent for the legislature to modify the old property law of capture with respect to oil and gas but that it may also delegate such authority to a subordinate body.

Jan 1, 1935

By H. F. Yancey, M. R. Geer

The importance of the size composition of coal is reflected in the difference in price of the various sizes of the same coal and in the large number of primary sizes and mixtures of sizes produced by the modern preparation plant to meet the demands of a market that in late years has grown increasingly conscious of coal size. The importance of size in the industrial and domestic uses of coal has its counterpart in the role played by size composition in the laboratory examination of coal. Investigation of many of the physical properties of coal in their relation to its uses requires an evaluation of size composition. In fact, the Standards on Coal and Coke issued by the American Socaiety for Testing Materials in 1936 contains 12 standard methods of testing that involve some use of size composition. The screen analysis is, of course, the standard method of determining size composition, whether the material is coarse run-of-mine coal or fine pulverized fuel. Custorriarily, the analysis is reported as the weight percentages retained on or passing each of a series of testing screens, the number of which may range from only two or three to as many as 20. When more than two or three sieves are used, which is usual, the number of weight percentages obtained is so great as to make the analysis difficult to comprehend. Direct comparison of analyses made 011 the same sieves is hard, and comparison of analyses covering the same range of sizes but made on different sieves is next to impossible. Consequently, a frequent purpose of sizing tests-—-correlation of size with properties and charactcristics related to size-—is rendered difficult. Less cumbersome means of expressing size composition have been attempted with various degrees of success. An average particle size, calculated by any of several formulas, is useful for some purposes, also the weight percentage retained on a single sieve finds some application as a

Jan 1, 1938

By M. R. Geer, H. F. Yancey

The importance of the size composition of coal is reflected in the difference in price of the various sizes of the same coal and in the large number of primary sizes and mixtures of sizes produced by the modern preparation plant to meet the demands of a market that in late years has grown increasingly conscious of coal size. The importance of size in the industrial and domestic uses of coal has its counterpart in the role played by size composition in the laboratory examination of coal. Investigation of many of the physical properties of coal in their relation to its uses requires an evaluation of size composition. In fact, the Standards on Coal and Coke issued by the American Socaiety for Testing Materials in 1936 contains 12 standard methods of testing that involve some use of size composition. The screen analysis is, of course, the standard method of determining size composition, whether the material is coarse run-of-mine coal or fine pulverized fuel. Custorriarily, the analysis is reported as the weight percentages retained on or passing each of a series of testing screens, the number of which may range from only two or three to as many as 20. When more than two or three sieves are used, which is usual, the number of weight percentages obtained is so great as to make the analysis difficult to comprehend. Direct comparison of analyses made 011 the same sieves is hard, and comparison of analyses covering the same range of sizes but made on different sieves is next to impossible. Consequently, a frequent purpose of sizing tests-—-correlation of size with properties and charactcristics related to size-—is rendered difficult. Less cumbersome means of expressing size composition have been attempted with various degrees of success. An average particle size, calculated by any of several formulas, is useful for some purposes, also the weight percentage retained on a single sieve finds some application as a

Jan 1, 1938

By J. E. Johnson

OF the many items of information necessary to the successful management of the blast-furnace, few are more important than knowledge of the location and movement of the stock: line:—whether the furnace is full and has been kept so; whether the stock is settling regularly or slipping; and, if slipping, how often it has slipped, at what times, and how far at each time. To obtain these data, a man is sometimes stationed at the top of a pair of mechanically-filled furnaces, sim-ply to watch and gauge them by hand in the old-fashioned way. A more recent practice is the suspension of test-rods from ropes leading over pulleys to the ground-level, where the ropes are mound on small drums with graduated peripheries and provided with crank-handles, whereby the skip-man or some other person can quickly and conveniently gauge the position of the stock-line in the furnace. I believe the credit for this great improvement belongs to Messrs. McClure $ Phillips of Sharon, Pa., who were, as far as I know, the first to apply it, and who have a patent for it. The valuable indications gained by application of the Uehling pyrometer to the down-comer are not to be ignorcd; but the information thus furnished is somewhat indirect, and there is no scale for the translation of " top-temperatures " into " feet down." Moreover, this apparatus, as a whole, is delicate, and the cost of installation and maintenance is high. If the record furnished by the Uehling pyrometer is not in the most desirable form, the test-rods, on the other hand, give no record at all, except through the memory or notes of a man who, to say the least, is not gauging continuously, and who may omit to report an improperly low stock-line, if it be due to a fault of his own.

Jan 1, 1906

"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

By T. E. Tietz, J. E. Dorn

Activation energies for creep of copper at intermediate temperatures, where crystal recovery was negligible, were determined by the simple technique of rapidly alternating the test temperature between and T2 (T2 = TI + about 10°K) throughout a constant stress creep test. The activation energy for creep H was found to be 37,000± 3,000 cal per mol, independent of stress and strain. The same creep laws as have been previously established for high temperature creep were found to be valid for creep at intermediate temperatures. But the AH was found to be lower than that for self-diffusion in the intermediate temperature range whereas it is known to be equal to that for self-diffusion at high temperatures. IT is now well established that creep at high temperatures can be correlated by the functional relationship'-" e = f(?) s = constant [I] where E is the total plastic strain, f is the function that depends on the stress, ? = f e -- dt, t is the duration of test, e is the base of natural logarithms, AH is the activation energy for creep, R is the gas constant,T is the absolute temperature, and s is the stress. Thus, identical values of are achieved during creep under a given stress at two alternate temperatures at the same total strain. At the same strain therefore where subscripts refer to the two alternate temperature conditions of test. Consequently, the activation energy for high temperature creep is readily obtained with the aid of Eq. 2. Activation energies so obtained have been observed to be insensitive to the creep strain at which they are evaluated, the applied stress, grain size, minor alloying additions,'-' cold worked state, and the presence of thermally stable dispersions of intermetallic compounds in an a solid solution matrix Furthermore, the activation energy for high temperature creep is very nearly equal to that for self-diffusion in all cases where adequate data are available for comparison." " The apparent identity of the activation energies for high temperature creep and self-diffusion strongly suggest that high temperature creep arises from a dislocation climb process. This hypothesis is further strengthened by the fact that the energy of activation for high temperature creep is insensitive to the applied stress," and by the observations that the correlation suggested by Eq. 1 cannot be ex- tended to temperatures below those for rapid crystal recovery. When using the activation energy for self-diffusion, Eq. 1 fails to give the required correlations between creep curves at various intermediate temperatures.' This suggests that the dislocation climb mechanism for creep might be superseded by some alternate mechanism in the intermediate range of temperatures. This investigation was initiated in a preliminary attempt to ascertain the type of creep law that might be valid in the intermediate range of temperatures. Special consideration, however, was given to the determination of the activation energy for creep in this range because the Becker-Orowan', " and the Mott-Nabarro10 theories for transient creep suggest that the activation energy should increase

Jan 1, 1957

ROSWELL H. JOHNSON,* Pittsburgh, Pa.-The industry, I think, has suffered very severely from the lack of just such work as has been done by Messrs. Lewis and Beal. I think we owe a great deal to the Bureau of Mines for at last undertaking this much needed work, even though it is so belated. It could have been of very great assistance in so many properties where its usefulness has now passed. I think it is perhaps well to sound a note of caution, owing to the fact that so much of this information was derived from eastern Oklahoma; but with the new bulletin giving the decline for many fields, there will be far less danger of falling into error through assuming too much uniformity. The cumulative percentage curve seems to 'me to be a. particularly splendid idea. It should have a very important -influence, especially as the authors have themselves pointed out several variables that ought to be taken into consideration. The thickness, I think, is going to be an especially important one to work out along the general lines of method that they have advanced. Probably the most surprising thing in the paper is the general rule that the decline of a well is more correlated with its size than with its age. I can't help but think that that generalization, important as it is, is rather rough and will not apply so clearly when we have a larger number of fields before us. Still the generalization, rough as it is, is of very great importance, since the industry has been very largely basing a great many of its ideas on the ignorance of that principle. It leads to certain corollaries that are of great consequence. The first is that the undrilled portion of the property must be appraised on a. different basis from that used for the drilled portion.

Jan 4, 1918

By Albert Walcott

THE success of various operations in the manufacture of optical glass depends, in a large measure, on the ability to maintain proper heat control. A good pyrometer system is, therefore, a very necessary part of the equipment needed. Men of long experience in dealing with high temperatures, who have acquired through constant practice the ability of judging approximate temperatures by means of color, are undoubtedly valuable, but even the most competent are not as reliable as a good pyrometer system. They admit that their ability to judge accurately varies from day to day and that their judgment is affected considerably by the condition of the sky, whether it is clear or cloudy. Besides, where it is a matter of only a few weeks to train a man to operate a pyrometer system, it takes about as many years to train him to judge temperatures by the state of incandescence. The pyrometer outfit in use in the glass plant of the Bausch & Lomb Optical Co. consists of the following: Platinum elements, optical pyrometers; base-metal elements, indicators, potentiometers, and recording pyrometers. Platinum Elements and Optical Pyrometers.-Temperature control in - the melting operation is of such great importance that it is very desirable to know the exact temperatures, relative temperatures being of little value. The use of the platinum element is to determine the rate of heating or cooling of the furnace. The platinum couple is installed in either the crown or the wall of the furnace. It is placed first in a porcelain protecting tube and this is placed in a permanently fixed fireclay tube projecting from 1 1/2 to 2 in. into the fire-chamber. It has been found impractical to use the platinum couple for determining exact temperatures of the melting furnace, for the platinum element deteriorates rather rapidly at the high temperatures used, 2500° to 2700° F. (1371° to 1482° C.). When protected and installed as described, though,

Jan 9, 1919