Search Documents

By B. Ladanyi

The problem of rock behavior under concentrated loadings has been the subject of a number of studies in the past and has been receiving increasing attention by rock mechanics investigators in recent years. Its application covers various fields, but main interest in its solution has arisen in connection with the problems of drilling, bearing capacity, and rock testing. These widely different purposes and fields of interest probably have been one of the reasons why, in spite of the large amount of published experimental data and several theoretical studies, there are still many points which need further clarification. Another reason for this situation undoubtedly is due to the fact that the rock behavior in indentation is complicated by a great number of influencing factors. Experimental evidence shows that, depending on the rock type (mechanical properties, porosity), environment (ambient effective pressure, pore fluid, temperature), and the type of loading (indenter shape, initial embedment, load level, loading rate), the rock response to indentation may vary within very large limits. The widely different rock behavior has made it impossible up to now to treat the problem with a consistent single mathematical theory, but has required instead a series of simplified models covering only certain most important events in the failure sequence. As far as the theory of rock indentation is concerned, this chapter does not add much new information. Its main purpose is, however, to state the indentation problem in a general manner and to indicate which points need to be studied in more detail before its definite solution is attempted. Also, since excellent reviews of the state-of-art of rock indentation in drilling have recently been given,1-4 this will not be repeated here, and only references pertinent to the points of the problem under study will be quoted. The theoretical part of this study attempts to give a quantitative evalu-

Jan 1, 1972

By Fred C. Bond

The process of comminution by grinding is properly classified as an art, rather than as a science. Like most other operations concerned in ore dressing, or in the treatment of nonmetallic minerals, the mathematical relationships of rock breaking are still obscure, and much disputed. If some basic formula exists, comparable for instance to E = RI in electricity, it has not yet been placed in common use. The absence of such a comprehensive mathematical background undoubtedly is the cause of many inefficient designs and installations, as well as of much poorly oriented experimental work. On the other hand, the mathematical immaturity of the process constitutes an opportunity for a real contribution on the part of those who enjoy mental pioneering. Some of the statements made in any such exploratory work may be little more than opinions, and it is to be expected that some will later be proved untrue; but such an evolutionary development is necessary if we are ever to arrive at the fundamental laws, the discovery of which can change the empirical art into a mathematically exact science. The most significant principle of comminution that we possess is probably Rittinger's law, which states that the work done in crushing or grinding is proportional to the area of the new surface produced. There is an alternative theory, known as Kick's law, which formerly was preferred to Rittinger's but which now is rather discredited. According to Kick, the work done in comminution is proportional to the volume, or weight, of the pieces broken, or to the cube of their diameters, while according to Rittinger it is proportional to the square of the diameters. Careful determinations of size distribution below the limit of sieve sizes1 indicate strongly that under ordinary grinding conditions the amount of new surface area produced is directly proportional to the net power input. Changes in the size ratio between the balls and the particles cause important differences in the proportion of the product that passes a given mesh size, but do not affect the total amount of new surface area; they merely change the distribution of the surface among mesh sizes. The principle of constant surface area is the logical result of Rittinger's law, and it may well have an important bearing on the comminution theories of the future. Formula for Ball Wear Grinding tests have been made in the Allis-Chalmers laboratory for more than 9 years, using a standard charge of mixed balls of different sizes; and a continuous record has been kept of the rates of wear of each size. These results have been combined and plotted in various ways in order to discover the relationship that exists

Jan 1, 1943

By Fred C. Bond

The process of comminution by grinding is properly classified as an art, rather than as a science. Like most other operations concerned in ore dressing, or in the treatment of nonmetallic minerals, the mathematical relationships of rock breaking are still obscure, and much disputed. If some basic formula exists, comparable for instance to E = RI in electricity, it has not yet been placed in common use. The absence of such a comprehensive mathematical background undoubtedly is the cause of many inefficient designs and installations, as well as of much poorly oriented experimental work. On the other hand, the mathematical immaturity of the process constitutes an opportunity for a real contribution on the part of those who enjoy mental pioneering. Some of the statements made in any such exploratory work may be little more than opinions, and it is to be expected that some will later be proved untrue; but such an evolutionary development is necessary if we are ever to arrive at the fundamental laws, the discovery of which can change the empirical art into a mathematically exact science. The most significant principle of comminution that we possess is probably Rittinger's law, which states that the work done in crushing or grinding is proportional to the area of the new surface produced. There is an alternative theory, known as Kick's law, which formerly was preferred to Rittinger's but which now is rather discredited. According to Kick, the work done in comminution is proportional to the volume, or weight, of the pieces broken, or to the cube of their diameters, while according to Rittinger it is proportional to the square of the diameters. Careful determinations of size distribution below the limit of sieve sizes1 indicate strongly that under ordinary grinding conditions the amount of new surface area produced is directly proportional to the net power input. Changes in the size ratio between the balls and the particles cause important differences in the proportion of the product that passes a given mesh size, but do not affect the total amount of new surface area; they merely change the distribution of the surface among mesh sizes. The principle of constant surface area is the logical result of Rittinger's law, and it may well have an important bearing on the comminution theories of the future. Formula for Ball Wear Grinding tests have been made in the Allis-Chalmers laboratory for more than 9 years, using a standard charge of mixed balls of different sizes; and a continuous record has been kept of the rates of wear of each size. These results have been combined and plotted in various ways in order to discover the relationship that exists

Jan 1, 1943

By George F. Becker

Complexity of Rock-Fractures. - The strains to which rocks have been subjected are manifestly very complex, and it is entirely safe to presume that every possible node of deformation and rupture is exemplified. The most superficial inspection of any ordinary mountain region is sufficient to assure the observer that the rocks have been pressed, stretched, bent, buckled, twisted, and shorn. The study of torsional rupture cannot fail, therefore, to throw light on geological phenomena. The question is, how areas which have been broken in this manner are to be distinguished from those which have yielded to other systems of forces. Phenomena of Joints. - It is well known that a large part of the more homogeneous rocks and some very heterogeneous rocks are intersected by partings, often called joints. These partings are frequently flat surfaces, even when seen in very large exposures, but are sometimes surfaces of moderate single or double curvature. Joints usually occur in groups, in each of which the several partings are parallel to one another, and several such groups often intersect the same rock-mass. In such cases the different systems make large angles with one another. Nearly all students of the subject of jointing have reached the conclusion that joints are faulted surfaces, the dislocations usually being of small amplitude; and this conclusion receives abundant support from the study of thin sections under the microscope. It has thus been shown that much even of what would be regarded in I hand-specimens as mere slaty cleavage consists, in reality, of innumerable microscopic faults. For this reason, Mr. Daubrée rejects the term "joint," as failing to imply the existence of relative motion, and has introduced the terms “diaclase” and “paraclase” as substitutes.1

Jan 1, 1913

E. L. BLOSSOM, New. York, N. Y.-That this paper deals with a real problem is illustrated by a statement made to the speaker a few months ago by the manager of a silver-lead property: "Our ore contains 60 per cent. silica on which the smelters are penalizing us heavily, and they are not able to take all our stuff even then. We have simply got to find some method other than smelting for getting the silver and lead out of our ores. We have had experts down here and have investigated flotation, leaching and volatilization, of which processes the latter is by far the most promising. We are continuing investigation." I was somewhat concerned in certain chloride volatilization experiments which we carried on in Denver in 1903, working on a carload of ore from Butte. Now being connected with the Cottrell process, by which method the fumes will undoubtedly he recovered if they solve the volatilization problem, I have looked into the matter again, and believe it can be developed into a commercial process. On a laboratory scale, working With silver-lead ores, experimenters have obtained a volatilization of over 90 per cent. of the total values in 30 to 60 min, on quantities of 1 to 5 lb., using a roasting dish and a muffle. That looks very good, and would be entirely commercial. On attempting to duplicate these results in a reverberatory furnace, they found that it is more likely to take 8 hr. firing to yield 75 per cent. extraction, which is not commercial at all, as it requires too much time, labor, and fuel, and the whole process is too slow. Of course it can be done, because we have done it in the laboratory.

Jan 1, 1918

By J. M. Hartman

ONE of the most important subjects to the blast-furnace engineer is a thorough knowledge of the conditions affecting the temperature in the different portions of the furnace. All efforts to decrease the consumption of fuel and improve the working of the furnace must be based upon it, and I may, therefore, be permitted to place before you the results of my observations, and detail the conclusions to which they have led me. Tracing the thermic conditions from below upwards we have at the bottom of a blast furnace making No. 3 iron a temperature of 2900° F., which increases slightly to a point a little below the tuyeres. In the immediate vicinity of the tuyeres the temperature is somewhat lower, owing to the entering blast ; but a short distance above the tuyeres, where all the oxygen of the blast has been converted into carbonic acid, the highest temperature in the furnace must be attained. This carbonic acid is, however, almost as soon as formed, converted by the glowing coal into carbonic oxide, a process which absorbs heat, reduces the temperature, and provides the active agent for the reduction of the iron ores. In its ascent the hot carbonic oxide gradually parts with its heat, first melting the descending iron and earthy materials, which drop down to the hearth of the furnace. The limit of this zone of fusion is rather sharply defined, and the temperature above this zone suddenly decreases. In its further ascent the hot gas drives off the carbonic acid from the limestone, which causes a further absorption of heat, and finally the gas escapes at the top, at a temperature of about 250° F. if the furnace is working well. These changes of temperature 1 have attempted to represent graphically,

Jan 1, 1880

By Strathmore R. B. Cooke, Iwao Iwasaki, Hyung Sup Choi

Oleic acid is the chief ingredient of fatty acids used as collectors in nonsulfide flotation. With a few notable exceptions, the various quantities of saturated and other unsaturated acids comprising the remainder are usually unspecified. There have been occasional investigations to determine the collecting ability of these other acids and their effect on collection with oleic acid, but much remains to be done in this field. Hukki and Vartiainen, on the basis of tests using palmitic, oleic, and linoleic acids and an impure linolenic acid, concluded: "The collecting power of fatty acids used in flotation increases with increasing unsaturation of the hydrocarbon chain." 1 Their work was concerned mainly with the response of ilmenite to the foregoing collectors, although tests were also made with magnetite, pyrite, hematite, and rutile. Cooke and Nummela, employing an al- most identical technical procedure to evaluate flotation of hematite, magnetite, and goethite with various fatty acids, including oleic, linoleic, and linolenic acids of the highest purity obtainable, found: "The effectiveness of 18-carbon unsaturated fatty acids, as collectors for hematite, decreases with increase in the number of non-conjugated double bonds."' In the foregoing investigations, collector efficacy was measured on the basis of reagent addition in moles per liter.

Jan 9, 1959

By Robert C. Berggren

THE hot-milling process for reconditioning rock-drill bits is not new. It has been employed by a few mines for years and in the past decade it has been widely adopted, as its advantages have become better known. Because of the extensive commercial development in England and Canada of machines to operate on this principle, general acceptance has been largely in the British possessions and until recently has been chiefly in the field of conventional steel. In the past two years there has been a definite trend toward hot-milling of detachable bits in Canada, [t] but only in the past year has any considerable attempt been made to build special machines for this type of work. Generally a machine designed for conventional steel has been used and special holders employed to manipulate the bit. As early as 1934 at least one operator in the United States had adapted hot-milling to conventional steel with a substantial saving in resharpening costs.1 Several other operators have taken it up but there has been no widespread adoption of the method in this country by users of conventional steel. This may be partly explained by the fact that until recently no American manufacturer produced this equipment and operators have been obliged to build their own hot-millers or import them. Several years ago a few machines were built in Seattle, Washington, and operated in some mines in the northwest, but, for reasons not generally known, the effort was abandoned. THE PROCESS Hot-milling performs the function of re-dressing the bit at a forging temperature of about 1650°F., by the removal of metal from the flutes with a milling cutter, followed by a similar cut from the bit gauge. Conventional bits are thus treated following the usual forging operation in a sharpener, and usually in the same heat.

Jan 1, 1940

By L. B. Schmitt, N. H. Polakowski

Square bars of cold-dvawn copper, mild steel and a 2024 aluminum alloy were forced through an adjulstable gap between two hardened steel rollers by pulling or pushing. The rollers were either free to rotate or were locked in position so that conditions comparable with drawing, rolling, ad containerless extrusion could be created at will. Push or pull forces as well as roll separatirg forces were measured. Forming efficiency and coefficients of friction were determined. For- slow-rate deformation the values ot µ wrere between 0.09 and 0.14. Possibilities for further investigation are indicated. THIS work was undertaken with the aim of a) determining the principal parameters of cold drawing under simplified conditions directly, without recourse to speculative assumptions and b) comparing drawing with rolling and extrusion from the viewpoint of forces involved and deformation efficiency. Data of type a) relating forces in axially-symmet-rical drawing to die geometry. drafting schedules, material properties and lubrication conditions are abundant. Their intrinsic value is. however. limited as long as the radial die forces are unknown. On the other hand. the difficulties associated with measurement of these forces are serious as witnessed by the extreme paucity of such information."" Comparative investigations of type b) were also remarkably few and they all employed ring-shaped dies through which round bars were either drawn or pushed.2-4 Only in one case were the applied and the die splitting forces measured simultaneously.2 In order to simplify the problem, deformation under approximately biaxial conditions was adopted in the present work;. This enables both the drawing (rolling, extruding) efforts and the separating forces to be measured with reasonable ease by conventional methods. Since drawing, extrusion, and rolling can be carried out under virtually identical conditions only in a roller die. an adjustable tool of this type was constructed. The circular die profile involved a difficulty with interpreting the drawing and extrusion data. This was obviated by arbitrarily defining the angle between a contact chord and the drawing plane as the -.equivalent" die semiangle. The simplification was considered permissible since the effect of die angle was not specifically investigated. An additional conlplication was caused by the square cross section of the processed bars. This shape was selected as a compromise between the desire to have as massive as possible specimens and the capacity of the roller die. The metal was only partially restrained from spreading laterally. the flow conditions being therefore intermediate between plane stress and plane strain. On the Huber-Mises yield criterion the constrained and uni-axial yield strengths differ by up to 16 pct but the actual error due to the ignorance of the constraint factor was presumably much smaller than the maximum. In spite of these reservations it was felt that the method employed and results obtained have some merit. With certain further refinements to be indicated later, this technique can yield data perhaps more useful for checking metal forming theories than other, mostly indirect, methods. EXPERIMENTAL Materials—The metals used together with their principal mechanical properties are listed in Table I.

Jan 1, 1961

By W. T. Cardwell

This paper presents a theory for estimating the rate of gravity drainage of a liquid out of a sand column. Account is taken of the variation in permeability to the liquid as the saturation in the upper part of the sand becomes less than 100 pct. The theory is confirmed by previously published experimental data. Introduction Petroleum engineers have expressed the need for 4 theory of gravity drainage. Brunner,' in particular, has pointed out that some type of mathematical theory is necessary to begin the application of laboratory data to field problems. Muskat and his associates2'3-4 have recently made contributions to the theory of gas-drive behavior and have indicated an intention to apply their methods to water-drive systems. No theory of gravity drainage rates has been developed, however, and it seems desirable to formulate one at this time. Differential Equations of Capillary Flow The flow of liquids in partially saturated porous media has been studied by many investigators.6-10 Richards6 presented derivations of fundamental differential equa- tions governing two-phase capillary flow; and used simplified forms of those equations in solving a steady-state problem. Muskat and Meres6 presented and used equations different from those of Richards. Their equations did not explicitly involve capillary pressure gradients; but included, on the other hand, terms expressing the effects of the evolution of gas from the liquid phase during flow. Leverett8 stated in 1940 that "previous work on the flow of fluid mixtures in porous solids [had] failed adequately to account for all of the three influences that cause motion of the fluids: capillarity, gravity, and impressed external pressure differentials." Leverett's basic equations, however, were specialized forms of the general equations of Richards,5 which had actually taken account of the three influences mentioned by Leverett, but had not been used in a problem involving all three. The fact is that our knowledge of capillary flow and our ability to express this knowledge in differential equations exceed our ability to solve the equations except in a few cases. General differential equations have usually been of little more than formal value. In solving practical problems, it has been necessary to develop specific equations, preserving terms that involved the factors important in those problems, and purposefully neglecting other terms that were not of predominating influence. This is the method followed here. It is believed that the solution of the particular problem and the scheme of the solution itself are new.

Jan 1, 1949

Discussion of the paper of L. C. Graton and Joseph Murdoch, presented at the New York Meeting, February, 1913, and printed in Bulletin No. 77, May, 1913, pp. 741 to 797. THOMAS T. READ, New York, N. Y. (communication to the Secretary *) :-At the meetings of English technical societies it not infrequently happens that, during the discussion of a paper, someone will arise to say that although he highly appreciated the material presented, nevertheless he believed it would have been better if some other phase of the question had been more highly emphasized. Assuming that this form of discussion is permissible in the Institute, I should like to reiterate the point made by Prof. A. J. Moses that conclusive proof of the identity of the minerals in question is an essential feature of the study of ores in this way. This is also expressed by Paul Krusch in his recent valuable paper 1 on the sulphide ores (in which he arrives at conclusions diametrically opposed to those of Mr. Graton), as follows : ?The diagnostic properties of the various ore minerals are known to but a limited circle of investigators." Many earlier investigators began the study of ores beneath the microscope by reflected light, but discontinued their work, in most cases, because they were unwilling to undertake the great amount of preliminary work necessary to securely establish a basis for their inferences. It is evident that Messrs. Graton and Murdoch realize that the promised later paper on diagnostic characters will be the more important of the two, but the point should be emphasized to forestall a flood of literature from other investigators who may gain the impression that the brief survey of polished specimens is a wade mecum to incontrovertible conclusions as to any given ore deposit.

Jan 10, 1913

THE purpose of this chapter is to present a general outline of the basic open-hearth process for the benefit of students, practicing open-hearth operators, and metallurgists who wish to review the subject. The discussion is limited to a description of the sequence and purpose of the operations, illustrated by data and examples. Subsequent chapters deal with more detailed and fundamental studies of the subject. The function of the basic open-hearth furnace is to convert various types of ferrous material into finished steel of given composition and quality. In comparison with other steel-making methods, the basic open-hearth process is one of the most versatile, both from the stand- point of the raw materials that can be used and the types of steel that can be produced. The process can be considered as a sequence involving melting, refining, and deoxidation. In the case of some types of liquid-metal charges the melting stage is not present, but refining and deoxidation in varying degrees are fundamental features of the process. GENERAL DISCUSSION OF THE BASIC OPEN-HEARTH PROCESS The first consideration in open-hearth practice is the type of charge on which the operation is based. This consists of three components-fluxing, oxidizing, and metallic materials. Fluxes. In the basic process the fluxing material is primarily lime, added in the form of either limestone (CaC03) or burnt lime (CaO). This is supplemented by magnesia (MgO) and lime from the furnace bottom and banks. The function of these fluxes is to form a slag with the silica (SO2), manganese oxide (MnO), iron oxides (FeO and Fe203), and phosphorus oxide (P205) that are produced by the oxidation of varying amounts of the silicon, manganese, iron, and phosphorus in the charge during melting and refining. The slag, composed of the basic fluxes and the neutral and acid oxides, floats on top of the steel bath when the charge is melted. The composition of this slag depends on the amount of each slag-forming element present in the charge and on the extent of oxidation of these elements during the course of the

Jan 1, 1944

By G. B. Gould

Every mathematical statement of a measure of anything (as distinguished from a count') is followed by a qualification—always implied if not explicity stated—-that the statement is only an estimate, which may vary from absolute accuracy within certain limits, according to the accuracy of the measuring instrument. This basic fact, so obvious to engineers, is not so well understood by many that make use of laboratory coal tests. The tolerances that must be allowed in measurements of coal quality are very important in both their commercial and engineering applications—and the significance of these tolerances depends upon the use made of the laboratory coal test. Only in recent years has there been any intensive study of this question of tolerances as applied to measurements of coal quality. There is very little in our published literature on the subject, and what has been published is not readily comprehended by those who sell coal, or buy coal and use it, unless they happen to have made a study of the subject themselves. There is great need for more widespread understanding of what lias been discovered and how it applies to the use of laboratory coal tests. What follows is an attempt to condense into a few pages the results of the major investigations so far reported, and to explain their meaning in simple nontechnical language, with the addition of some recent illustrative experiments. Determining Deviations in Quality It is necessary at the outset to distinguish between: (I) the accuracy with which one test indicates the quality on one lot of coal; and (2) the accuracy with which a test of one lot of coal represents the average quality of a commercial product, of which the buyer will presumably receive a series of shipments—perhaps many thousands of tons. It is necessary to make this distinction because coal is a variable material—a heterogeneous mixture of a variety of components—the quality of which will vary from one lot to another. Therefore an absolutely accurate determination of the quality (if that were possible) of one lot of a coal is an

Jan 1, 1938

By G. B. Gould

Every mathematical statement of a measure of anything (as distinguished from a count') is followed by a qualification—always implied if not explicity stated—-that the statement is only an estimate, which may vary from absolute accuracy within certain limits, according to the accuracy of the measuring instrument. This basic fact, so obvious to engineers, is not so well understood by many that make use of laboratory coal tests. The tolerances that must be allowed in measurements of coal quality are very important in both their commercial and engineering applications—and the significance of these tolerances depends upon the use made of the laboratory coal test. Only in recent years has there been any intensive study of this question of tolerances as applied to measurements of coal quality. There is very little in our published literature on the subject, and what has been published is not readily comprehended by those who sell coal, or buy coal and use it, unless they happen to have made a study of the subject themselves. There is great need for more widespread understanding of what lias been discovered and how it applies to the use of laboratory coal tests. What follows is an attempt to condense into a few pages the results of the major investigations so far reported, and to explain their meaning in simple nontechnical language, with the addition of some recent illustrative experiments. Determining Deviations in Quality It is necessary at the outset to distinguish between: (I) the accuracy with which one test indicates the quality on one lot of coal; and (2) the accuracy with which a test of one lot of coal represents the average quality of a commercial product, of which the buyer will presumably receive a series of shipments—perhaps many thousands of tons. It is necessary to make this distinction because coal is a variable material—a heterogeneous mixture of a variety of components—the quality of which will vary from one lot to another. Therefore an absolutely accurate determination of the quality (if that were possible) of one lot of a coal is an

Jan 1, 1938

By L. Cichowicz, K. K. Millheim

The constant-rate drawdown test performance for a low-permeability, verticany fractured gas well was investigated. A series of gar wells were tested by flowing each well at constant rate until the data could be analyzed using con-ventional radial flow theory. Each well was then shut in to build up. After a sufficient buildup was obtained, another flow Iest commenced but at a higher flow rate than Ihe first test. Again, the well was shut in when radial fiow was obtained. his procedure was repeated for three to four different flow rates. Two wells in the San Juan basin were tested using this procedure. Both wellere fractured after completion, cleaned up and then shut in until flow testing commenced. Test designs of both wells permitted investigation of the most realistic values of egective permeability, wellbore radius and turbulence factor. Also, being able to determine the eflective fracture flow area and vertical fraclure efficiency was inherent with this testing approach. It was observed that fractures in both wells influenced the Pressure behavior for approximately Is to 40 hours (depending on the flow rate) before radial flow was evident. After this time, drawdown data were analyzed using radial pow theory. When a low-permeability gas well has vertitally oriented, induced fractures, the early flow geometry ic. essentially linear. It will be shown how to determine when a flow test has been conducted long enough so lha' the most representative values of effective permeahiiity. wellbore radius and turbulence factw can be calculated. From the linear pressure data, valuable information about The fracture treatment, such as the effective flow area and vertical fracture efficiency, can be determined for vertically froctured wells. Introduction During tests on gas wells in the Sari Juan basin7 initial transient behavior lasted for many days because of the low permeability of some porous media. As a result, stabilized flow performance could not be obtained. If these wells received some type of stimulation treatment, early pressure behavior deviated from conventional theoretical radial Row. When conventional radial flow theory was used to analyze these low-permeability fractured gas wells, larger values of flow capacity and absolute open flow potentials (AOF) sometimes resulted. Wells were assigned open flow poten- tials that proved to be 3 to 10 times higher than the well would sustain over a longer period of production. In some cases where the wells had flowed for longer periods of time during a constant-rate drawdown test, it was noticed that the effective flow capacity appeared to be decreasing with time until a certain value was reached. The early nonradial pressure behavior can be explained If linear flow is assumed. Rusell and Truitt mathematic. ally investigated the vertically fractured well in a bounded area. They showed that early flow behavior was essentially linear and, for x,/x. approximately less than 0.10 radial flow was obtained after short periods of time. Then realistic values of effective permeability and skin could be determined. Scotta experimentaliy studied the vertically fractured well with a heat flow analog. He showed that earb flow was linear, Both studies indicate that, for small values of x,/x,, linear flow approaches radial flow if the well is tested long enough, To help prove this concept of early linear flow caused by induced vertical fractures, two low-permeability gas wells were tested. Both wells received large fracture treatments prior to testing. A vertical fracture was indicated from the analysis of fracture treatments, As anticipated, tests of both wells indicated early linear flow that was later followed by a period of radial flow, Data collected from each well were analyzed. From the well tests, plus other information on each well, the effective permeability, wellbore radius and turbulence factor were calculated. Effective fracture flow areas calculated from test analyses for each well proved to be approximately one-fourth the created area calculated from classic hydraulic fracturing theory: other fractured wells that were tested but not presented in this paper also indicated that the effective fracture flow area was one-fourth to one-third the created area predicted from hydraulic fracturing theory. The vertical fracturing efficiency was estimated from the calculated values of effective wellbore radius and fracture flow area. For the two wells tested, calculated fracture lengths x, were 112 and 105 ft, and the vertical fracturing efficiencies E, were 122 and 183 percent. Development of Flow Model Agnew' showed that most induced fractures below 1,500 ft are vertical. Anderson and Stah15 indicated that most of the fractures they studied were vertical. Thc model proposed for early flow in most vertically fractured gas wells is shown by Fig. 1. This model should approximate early flow behavior until radial flow is reached, at which time a radial model with an effective wellbore radius of 0.5 they will

Jan 1, 1969

By W. J. Keep

Almost without exception, writers on the subject say that sulphur in cast-iron will cause it to be white, and is in every way injurious. All founders believe that a small amount of sulphur in the fuel will work great damage, and that if any castings crack, or if anything out of the general run occurs, it may be charged to sulphur in the fuel. Fuel rarely contains more than 1 per cent. of sulphur, and if this can produce so marked an effect, one would suppose it an easy matter to introduce sulphur into cast-iron, so as to produce castings containing different desired percentages of sulphur. We have be-

Jan 1, 1894

By Joseph Richards

PLATING iron with copper has received great attention from practical sand scientific men, but, aside from the deposit secured by immersion of iron in copper salts, by electro-plating, or by welding together thin sheets of iron and copper, these efforts have met with no success. Failure of these efforts, in the production of copper plating, has been due to the fact that the conditions normally and necessarily present in the plating operation are antagonistic to the production of copper-plated iron. In most, if not quite all of them, a bath of molten copper has been used. The-temperature of a molten copper bath is so high that the iron becomes oxidized before it can be immersed in the molten copper, and unless protective flux for the molten copper is used, the surface of the copper will become oxidized, and, in any event, the plated iron will oxidize immediately on its being withdrawn from the molten bath. I recently had the pleasure of visiting the works of The Metals Plating Co. at Elizabeth, N. J., where I witnessed the plating of iron sheets with copper by a new process.1 The plating metal is applied to the sheet in the form of a liquid mixture by means of rolls, such as inking rolls. The sheet, after being coated with the mixture, is automatically carried forward and deposited on a link-belt conveyor, which carries it through a furnace maintained at a. temperature well above that of molten copper. The basic principle involved in this method lies in the application of the plating metal to the sheet while the sheet is cold and then melting the metal in place on the sheet under conditions which are favorable to the formation of the plating.

Jan 1, 1919

By Joseph Pogue

THE prices of crude petroleum and its derivatives have shown an upward trend from 1915 to 1920, and a downward trend from 1920 to 1923, see Table 1. Over the former period, oil prices were dominated by the rapidly increasing demands and inflation incident to the war and its aftermath, while over the latter period oil prices were influenced at the outset by deflation and then by the conditions of overproduction that have characterized the past three years. The purpose of this paper is to analyze the broader features of the more recent price movements in the petroleum industry and to relate these features to basic economic conditions in the industry.

Jan 3, 1924

By Donald B. Evans, Robert D. Pehlke

The solubility of nitrogen in liquid Fe-B alloys has been measured up to the solubility limit for the formation of boron nitride. The activity coefficient of nitrogen increases with increasing boron content in the range 0 to 7 wt pct B. From experimen -tal data, values have been calculated for the B-N interaction parameter e3 at temperatures in the range 1550" to 1750°C. A value of 0.038 has been estimated for the boron self-interaction parameter eg at 1550°C. The standard free energy of decomposition of boron nitride into the elements dissolved in liquid iron has been determined to be: ?F° = 45,900 -21.25T in the range from 1550° to 1750°C. The nitride is assumed to be of composition BN. BORON nitride has an unusual combination of properties which make it appear attractive in a wide range of engineering applications. Some of its more important and most recent applications are in the nuclear area, particularly in connection with the liquid-metal cooled reactor concept now receiving considerable emphasis. Boron nitride has a high degree of stability at elevated temperatures. It also has excellent ma-chinability and the ease with which its crystals deform suggests applications as a lubricant. These properties stem from a hexagonal layer-type structure similar to the structure of graphite. One of its primary uses to date has been for seals in liquid-metal pumping systems. It is also used in nuclear reactors as an insulating layer to separate two solid metals which are not themselves compatible under the conditions of temperature and atmosphere in which they are used. Its inertness to liquid metals has also suggested use as a mold-release agent in casting processes. In addition to its excellent machinability and reported inertness to liquid metals such as iron, silicon, aluminum, copper, and zinc, boron nitride has high thermal conductivity and excellent thermal shock resistance. This combination of properties would make it appear ideal as a refractory crucible material for refining of high-purity liquid metals, for example high-quality steels. However, since it is known that concentrations of boron as low as 50 ppm can have a marked effect on the physical properties of certain steels,' in particular on the creep and stress-rupture properties, an investigation was undertaken to define accurately the chemical equilibrium among boron, nitrogen, and liquid iron in the range of steelmaking temperatures. EXPERIMENTAL PROCEDURE Two experimental approaches to this problem were employed: a Sieverts' method and a quenching method. In the first method, the Sieverts' technique was used to measure the equilibrium nitrogen solubility in liquid Fe-B alloys of 0 to 7 pct B as a function of nitrogen gas pressure over the melt. The solubility limit of the boron nitride phase formed was determined by the point of departure of the nitrogen absorption from Sieverts' Law. This technique has been applied to liquid Fe-Ti alloys by Rao and parlee,' to liquid Fe-A1 alloys by Evans and Pehlke,3 and to solid Fe-V alloys by Fountain and Chipman.4 In the second method a melt of liquid iron was held in a crucible of boron nitride under a known partial pressure of nitrogen gas. After thermodynamic equilibrium was attained, the melt was quenched in a stream of helium and then analyzed by wet-chemical methods for boron and nitrogen. The Sieverts' apparatus used in the first method was essentially of the same design as the one described by Pehlke and Elliott.5 The charge materials were vacuum-melted high-purity iron (Ferro-vac E) supplied by the Crucible Steel Co. and -325 mesh boron powder supplied by Cooper Metallurgical Associates of Cleveland, Ohio. The boron contained less than 0.02 wt pct O, according to supplier's analysis. Recrystallized alumina crucibles were used to contain the melt. Examination of solidified melts showed these crucibles to be satisfactory with no evidence of any reaction or physical penetration of the crucible wall by the melt. The melt temperature was measured by a disappearing filament-type optical pyrometer sighted vertically downward on the melt surface through a 1/4-in.-diam sight hole in the crucible lid. The pyrometer was calibrated against the melting point of pure iron in the same apparatus, taking the emissivity of

Jan 1, 1964

By Walter S. Weeks

In this paper the effect of natural ventilation pressures is considered a part of the mine resistance and it is shown that their effect on the mine resistance is not the same as the total natural ventilation pressure of the shafts if the mine has several levels. It is shown that increasing the fan pressure causes the division of the air to approach the condition that would obtain if there were no natural ventilation pressure present. It is shown that if an appreciable difference in pressure is maintained between the beginning and end of a group of splits, the value of the integrated effect of the natural ventilation pressures on the individual splits does not change substantially with moderate changes of this pressure. A method is outlined for determining the resistance factor of the mine and the value of the effect of natural ventilation with the fan operating; also a method for determining this factor when circulation is caused by natural ventilation alone. Natural Ventilation Pressure Natural ventilation pressure (N.V.P.) is caused by the difference in weight of the air in two similar columns between two horizontal planes, and the difference in weight is caused principally by the difference in temperature of the two columns. The fan pressure causes some variation in density, but, since it is usually small and affects both columns, its effect is relatively unimportant. It has been suggested that "N.V.P." be called "stack effect"; but, since the term N.V.P. was used in a previous Institute paper,' applied in exactly the same manner, the term will be used. Frictional Resistance The frictional resistance to flow in a mine without natural ventilation may be expressed as RQ2 where R is a constant for a given air density and Q is the rate of flow. This frictional resistance plus the effect of velocity changes will be called the F pressure (F.P.) and a curve of F.P. against Q, the F characteristic of the mine. If a pressure is applied to a mine by a fan, the air flow so adjusts itself that the drop in pressure through any path from entrance to exit of mine, due to frictional resistances and velocity changes, is the same as that in any other path. The mine resistance varies as the square of the quantity. The air distribution without N.V.P. will be called "normal." Natural Ventilation Present When N.V.P. is irregularly distributed in a mine, it is more convenient in analysis to consider the N.V.P. as a part of the duct resistance. If it is so considered the resistance no longer varies as the square of the quantity, and if N.V.P. exists between levels the distribution of the air is no longer normal. The total N.V.P. of the mine is the pressure caused by the full length of the shafts. If a mine has several levels, N.V.P. exists

Jan 1, 1946