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By Hubert D. Keiser

An observation that is finding fresh confirmation in the leadership of the Allied Nations is "When the need arises, a man will rise to fill it." Much the same can be said of industrial advances in the current emergency. Events and circumstances have created needs for new materials and stimulated the inventive genius of man to fill them. The timely development of fibrous-glass manufacture, in relation to present war needs, is a case in point. Historical Summary It is probable that the first glass fibers produced by the hand of man were made about 4000 years ago. Successful production of glass fibers for manifold industrial and military uses, on any scale that could begin to meet present needs, has a history spanning a scant four years. The American processes that brought this young industry into being were developed between the years 1931 and 1937; research and manufacturing efforts were consolidated to create a commercially satisfactory operation as late as November 1939. In the 40 months that have elapsed since then, the industry has achieved commercial importance, supplied immense quantities of materials for pre-war industrial expansion to meet "defense" and Lend-Lease needs, and now has reached such importance that it has come largely under the control of the War Production Board for equitable distribution of its major products among 13 claimant agencies. It is worthy of note, however, that the Bureau of Ships, Navy Department, began exploratory use of fibrous-glass products in 1932, within one year after the date of the first experimental trials of the new process. This early recognition of the military importance of fibrous glass gave impetus to further research work. The foregoing rapid scanning of historical development must be filled in, lest the. impression be created that glass fibers were suddenly created out of thin air, with no antecedent trials, failures, and partial successes. The actual history of glassmaking is lost in antiquity. Probably some nomadic tribesman found molten glass beneath the bed of a hot campfire built upon sand of the proper composition. If his curiosity led him to poke the glowing, viscous pool with a green-wood stick or some handy weapon, it is probable that he drew a glass fiber on the end of his implement. Molten glass has much the same consistency as honey or molasses; it strings out tenuously. Thus, it is quite possible that the first form of glass shaped by man's action was a glass fiber. Artisans in glass, throughout the long Direc- of glassmaking as an art> drew fibers from fine rods for many decorative applications, including "spun glass" decoration in beautiful stemware and the charming millefiori (glass flowers encased in solid glass), and even to create the blood vessels in glass eyes to match a bleary mate.

Jan 1, 1948

By Andrew A. Blair

It is now well known that certain pig-irons give a considerably smaller percentage of sulphur when determined by evolution-methods than when determined by oxidation-methods. The most striking examplcs of such irons are those made either wholly or in large part from New Jersey magnetites containing more or less titanium. It is never safe to use an evolution-method on such iron; for it is quite common that the sulphur result by evolution is only one-half or even one-third as great as that obtained by oxidation. For this reason, evolution-methods should be discarded, except in the analysis of pig-irons known to contain the sulphur in a state of combination from which it is evolved as sulphuretted hydrogen on treatment with hydrochloric acid. A good example of an iron containing, in the residue, sulphur insoluble in hydrochloric acid having come to our attention, it was determined to try to isolate a suspected insoluble sulphide. A large piece of high-silicon gray-forge iron was accordingly selected as the most promising material to work on. This piece was dissolved slowly, through several months, in dilute hydrochloric acid, aided by the electric current, yielding a soft graphitic residue. The object of dissolving a mass of iron, instead of drillings, was to prevent the crushing, by the drill, of any insoluble crystalline compound that might be present. The first step in the preparation was to break up the graphitic material and put it through bolting-cloth of 157 meshes to the linear inch. This was done by crushing the mass under the fingers on the bolting-cloth fastened over the top of a beaker, while a stream of water from a wash-bottle washed the finer portions through the cloth. The suspended matter was allowed to settle. It was then transferred to a platinum

Jan 1, 1902

By James V. Thompson

SINCE it was introduced in 1943 to recover chromite from Oregon beach sands, the Humphreys spiral concentrator has proved successful in several fields of wet mineral beneficiation. By the end of 1957, 9390 Humphreys spirals had been manufactured. Most of these are still in service. The spiral does not offer a panacea for all mineral dressing problems. Its proper application can best be determined by test work. Spirals present a unique advantage for the metallurgist to make tests in a full-size machine rather than a miniature model, without the risk involved in scaling up results. With only 10 to 40 lb of sample, the operator of a closed circuit test unit employing a full-size Humphreys spiral can conduct preliminary tests with full-scale loadings of 0.5 to 2.5 tph. With larger samples, from 300 to 500 lb, he can run longer multi-stage tests to obtain reliable data for the next step-pilot plant design. The manufacturer of the Humphreys spiral concentrator maintains a fully equipped ore dressing laboratory and by insisting on test work prior to sales has largely prevented misapplication of the spiral.

Jan 1, 1958

By O. L. Kowalke

During the last few years the use of base-metal thermocouples has increased very considerably in various industries, due to the necessity for more precise control of temperatures. The base-metal couple has the advantages of being robust to a surprising degree, cheap as compared with platinum couples, sufficiently accurate for most operations, rapid in indicating changes in temperature, easily renewed or repaired, and of generating a much higher electromotive force than the noble-metal couples. There are, however, some factors, such as indicating and recording instruments, the insulation on the elements, the constancy and homogeneity of the wires, and the resistance to oxidation in the furnace, that limit the. Usefulness of the temperature-measuring device. It is the purpose of this paper to discuss in what manner these factors affect the usefulness of the couples.

Jan 9, 1919

By J. F. Peters

The term solution loss is discussed and defined. Examples are given showing that solution loss may either have a favorable or unfavorable effect on blast furnace performance. A theory is advanced explaining the contradictions encountered during earlier studies of the problem. MANY papers have been written and numerous theories advanced concerning the chemical reactions in the iron blast furnace. Richards, discussing the utilization of fuel in the blast furnace, said: "All the carbon burnt in the furnace should be first oxidized at the tuyeres to CO and all the reduction of oxides above the tuyeres should be caused by CO, which thus becomes CO,. This dictum is not Gruner's own words, but expresses their sense, and from the point of view of the present discussion, it is the correct principle upon which to obtain the maximum generation of heat in the furnace from a given weight of fuel." Richards also said the cubic feet of wind per pound of coke does not express how efficiently a furnace is running, but it will be shown later where Howland paid much attention to this figure. Richards pointed out a shortcoming of Grun-er's discussion in that Richards claimed there is not enough CO generated in a good working blast furnace to possibly combine with the oxygen of the ore, so some of it must be reduced by solid carbon. Mathesius2 made two important contributions. First, he wrote the direct and indirect reduction equations showing the heats of formation in each case and stressed that the indirect reduction reaction produces heat while direct reduction absorbs heat. Secondly, he substantiated Richards' conclusion that there may be a deficiency of CO gas and that some direct reduction is required, but he pointed out that "direct reduction in the hearth has often been confused with direct reduction in the stack, which more correctly should be termed 'premature combustion'." Then he said that "as this carbon is consumed partly by economical (direct reduction in the hearth) and partly by wasteful reactions in ever varying proportions, it is evident that the relation of this total carbon gasified above the tuyeres to the fuel consumption of a furnace cannot possibly have a direct bearing on the economy of furnace operation. The premature combustion of carbon (CO2+C?2CO) must therefore in all cases be considered a detrimental reaction." Johnson3 discussed this whole problem. Through experience Johnson found that when departure from Gruner's ideal working is considerable, the fuel economy is poor, and when the quantity of blast goes up, the fuel economy goes up in the same proportion. Johnson said that the wind per pound of coke is a measure of fuel economy, which will be shown to be wrong. Howland4 established the fact from operating data that there was no relationship between the coke consumption of a furnace and the percentage of coke burned at the tuyeres. But some of his calculations have led to questionable conclusions, such as "it is practically impossible to obtain low coke consumption unless we keep our wind low." Howland made an important contribution when, in his concluding paragraphs, he reached certain negative decisions as to why one coke works better than another. He said the reason one coke works better than another in a blast furnace is not because: 1—there is any difference in the percentage gasified at the tuyeres, or 2—there is any difference of wind required per pound of coke. Korevaar5 propounded a new theory on combustion which disagrees with Gruner because "as far as we can see, this is sufficient proof for the invalidity of Gruner's ideal, for if it was valid, the Low coke consumption should always be accompanied by a higher percentage of carbon burned at the tuyeres. This not being the case, we must deliberately give up our belief in Gruner's ideal." The part in italics will be proved to be wrong. Martin" contended that there was not enough reducing capacity in the blast furnace unless solution loss occurs. He came to a series of conclusions, such as: 1—The greatest efficiency of the blast furnace may not be attained when the reduction is performed entirely by carbon monoxide as demanded by Gruner's definition of the ideally perfect working of the blast furnace. 2—The so-called solution loss reactions, which should more properly be termed direct reduction reactions, promote furnace efficiency. 3—In modern blast furnace practice, the carbon consumption of the process is determined primarily by the carbon needed for reduction purposes, any thermal deficiency created by the reduction process being balanced in practice by the use of blast heat. From a practical standpoint further discussion of the theory of chemical reactions is of little moment. There is however one phase of the general theory of chemical reactions which is very important and that is the combustion of coke in the blast furnace. The purpose of this paper is to show that the reaction

Jan 1, 1955

Gentlemen of the American Institute of Mining Engineers.—As you well know an application is about to be made to Congress, by the American Society of Civil Engineers, for the appointment of a cornmission composed of persons skilled in the production and use of iron, steel, and other structural materials, whose duty it shall be to test the strength, elasticity, and other quatities of such materials ; not simply the substances used as such, but the members of large structures composed of such materials, of the forms and sizes in which they are actually used. As I understand, the papers that will be read here to-night will have for their object to show the necessity for such tests, and therefore the necessity for the commission asked for. As the representative of the Society of Civil Engineers, I have to thank you, gentlemen of the Mining Engineers, for the great zeal with which yon have taken up this subject, and seconded the efforts of the Civil Engineers; or, perhaps I ought rather to say, initiated the efforts to get a suitable commission appointed to obtain most vitally important information which it is admitted on all hands we do not now possess. In drawing up the memorial to Congress, in connection with some of the ablest and best informed of our Society, and in all the discossions on the subject, I have been struck with the emphasis with which the confession is made, that so little is known of the strength of the larger-sized members constantly used in building structures of the magnitude which the present requirements of the country now demand. I presume the remarks made to-night will bring this out very prominently. This is no disgrace, for with the means here-

Jan 1, 1882

By Shiou-Chuan Sun

THE fact that coals of different ranks and even of the same rank differ greatly in their amenability to iroth flotation is well known. In recognition of the need for an explanation of this phenomenon, two hypotheses have been suggested. Wilkinsl reported that the floatability of coals increased with an increase of the carbon content or rank. This postulate is handicapped by the fact that bituminous coals that possess moderate carbon contents are actually more floatable than anthracite coals that have high carbon contents, as shown in columns 6 and 9 of Table I. Taggart and his associates' implied that the difference of floatability between bituminous and anthracite coal was caused by the variation of carbon-hydrogen ratio. This is not applicable to the relative floatability of other coals and carbons. For example, column 11 of Table I shows that the carbon-hydrogen ratios of low-floating lignitic coal and non-floating animal charcoal are not only smaller than the moderate-floating anthracite coal, but are also similar to the high-floating bituminous coal. Furthermore, according to this hypothesis, high temperature coke-A (464), Ceylon graphite (1238), and lamp-black (357), all possessing extremely high carbon-hydrogen ratios, should be less floatable than other substances having much lower carbon-hydrogen ratios such as high volatile-B bituminous coal (11.9 to 22), anthracite coal (35.7 to 60.5), lignitic coal (15.6 to 33.6), and charcoal (13 to 26.2). However the former group is actually more floatable than the latter group. In this paper, a surface components hypothesis is Proposed to explain the different floatabilities of coals, carbons, and hydrocarbon minerals. The validity of the hypothesis is experimentally supported by the actual floatability, natural floatability, wettability, and adsorbability for neutral oils of coals, carbons, and hydrocarbon minerals tested. The combustible recovery of the flotation results, as used in this paper. was calculated from Eq. 1: P (100-Ep) 100 RWCP Rc= [1] F (100-E,) C, where R, is the percent combustible recovery; F and P are, respectively, the weight of feed and the weight of concentrate or product; E, and Ep are, respectively, the total percent of ash plus moisture in feed and in concentrate; Ru. is the percent weight recovery: and C, and C, are, respectively, the percent of combustible in feed and in concentrate. Except for ash and moisture content, all chemical components of a coal are assumed combustible. The experimental work included studies on flotation, ultimate and proximate analyses, contact angle tests, extractions of bitumen-A with benzene, adsorptions for liquid hydrocarbons, and wetting tests. Most of the flotation experiments were performed in a laboratory Fagergren machine; others were tested in a small Denver machine. The solid feed for the former was 300 g and for the latter was 30 g. The solid materials used for flotation were crushed to —48 mesh. After the mineral pulp in the flotation cell was agitated for 6 min and the pH was adjusted to 7.5 & 0.2 with sodium hydroxide or hydrochloric acid, a petroleum light oil having a viscosity of 5.73 centipoises at 77 °F was added and conditioned for 2 min. Finally, pine oil was introduced and the froth was collected for exactly 3 min. The weight ratio of petroleum light oil to pine oil was kept constant at 1.5 to 1. Tap water was used for all flotation tests. Contact angles were measured with a captive bubble machine. For each coal sample, three specimens were mounted in transoptic mounts and polished with levigated alumina, first on a sheet glass, then on a cloth-covered metal polishing wheel. The polished specimen was first washed with distilled water and wiped thoroughly on a cleaned linen pad, then transferred into the pyrex cell of the captive bubble machine and conditioned for 6 min., and finally measured for contact angles at three or more points. Except where otherwise stated, the induction time for each measurement was 1 min. The contact angle representing each material was obtained by averaging the measurements of three specimens. The linen pad was first washed with warm distilled water, then boiled 30 min in a 2N sodium hydroxide solution, and finally washed with distilled water until no trace of sodium hydroxide could be detected in the decanted solution. The cleaned linen pad was stored under distilled water. Immediately before using, the pad was rewashed and transferred into a clean pyrex petri dish partly filled with distilled water. The glassware and rubber gloves used were cleaned by soaking in sulphuric acid-potassium dichromate cleaning solution, followed by rinsing with distilled water. The polished specimens were handled only by glass forceps. The ultimate and proximate analyses were made in accordance with the ASTM standard procedures for coal and coke. The extractable bitumen-A was determined by weighing 1 g of —100 mesh sample and placing it in a desiccated and weighed ASTM aluminum-extraction thimble. The thimble was placed in condenser hooks and inserted into an extraction flask containing 100 cu cm of benzene. The flask was heated and the benzene vapor was condensed by water coils. At the end of 24 hr of percolation, the thimble was removed, desiccated, and weighed. Loss in weight of sample was taken as bitumen-A and calculated to dry and ash-free basis.

Jan 1, 1955

By A. W. Gauger

SMELTING of iron ore, manufacture of steel, and the fabrication of ferrous metal products are all processes that require energy. Charcoal was adequate, to supply this energy for the relatively simple processes of the early iron-masters. In the fourth decade of the nineteenth century, anthracite and bituminous coal and later coke supplanted charcoal for the smelting of iron. So far as the chemical phases of the process were concerned, charcoal was an ideal iron-furnace fuel. It had practically no sulphur, and its ash, besides being low in quantity, consisted chiefly of lime and alkalies, thus supplying a part of the flux required for smelting the ore. The ash of coal and coke on the other hand, being largely silica, had itself to be fluxed with bases added to the charge. Physically, however, coke proved to have many advantages over charcoal, which could not be used in the furnaces of today. The chief reason, however, for the change from charcoal to coke was the impossibility of maintaining an adequate wood supply.

Jan 1, 1941

By J. O. Mack, J. B. Russell

IN recent years, solders containing 20 per cent tin with no bismuth or cadmium have been developed by a few companies, and personnel have been properly instructed in their use. In addition, since the tin shortage, a number of solders containing less than 10 per cent Sn, and some with no tin, are being used in special applications; however, a solder of this type has yet to be developed that is satisfactory for general use. [ ] The purpose of this investigation was to develop an alloy containing a maximum of 15 per cent tin, with no cadmium or bismuth, having solder properties equivalent to or better than those of substitute solders now specified containing i8 to 20 per cent tin (Table I), or even approaching the properties of the standard 40 to 60 tin-lead solder. The wartime restriction of bismuth and cadmium, elements that have beneficial effects on fluidity, solidification range and strength, makes it increasingly difficult to develop a general-purpose solder containing a maximum of 15 per cent tin. In the course of this investigation, 11 elements were used in various combinations with the basic 15-85 tin-lead alloy. These elements were antimony, silver, copper, indium, thallium, lithium, calcium, barium, potassium, sodium and arsenic. In all, 116 low-tin solders were investigated, with the idea of developing a solder that will give satisfactory working properties, specifically in regard to "wetting" of copper, brass and iron, solidification range, capillarity and shear strength of a soldered joint. The relative importance of these various properties plays an important role in the search for substitute solders, since it is almost impossible to retain all of the desired qualities of a high-tin solder and still make drastic changes in the alloy composition. Because of the expected uses of a general-purpose solder, it is necessary that it have properties, especially in regard to wettability, that will enable it to be used on the metals in common use. BASIC CONSIDERATIONS The maximum liquidus temperature of a solder is determined by the particular application involved and the temperature that can be obtained by the source of heat.

Jan 1, 1944

By H. E. Doerr

The writer has been unable to find much information relative to tests made to determine the effect of forging on the specific density of steel. The opinion, however, among men engaged in the business, seems to be that forging greatly compresses or consolidates the steel. While such is doubtless the case with spongy or porous steel, the following experiments indicate that there can be little or no change in the density with steel initially free from cavities. Ten ingots of basic open-hearth steel cast as shown in Fig. 1 were used in the experiments. All the specimens were 0.53 carbon with all other elements the same, the analysis being determined from drillings taken midway between the center and outside of the upper end, as shown in Fig. 2. The specimens were selected from over one thousand ingots so that the tests could be comparative for the work done in forging only, but no two of the ingots were cast in the same heat. Each ingot remained in the mold approximately 30 min., when it was removed and sir-cooled. About 12 hr. later, when the temperature had been reduced to approximately that of the surrounding atmosphere, the head was discarded and the ingot heated in an oil furnace to approximately 2250" F. (1235" C). Approximately 1 min. was required to forge under the steam hammer to 1 1/4 in. (31.75 mm.), rough diameter, as shown by the dotted lines in Fig. 2. All ingots were allowed to air-cool after forging. Cylinders 1/2 in. (17.7 mm.) in diameter and 1/2 in. high were then turned from the forged and unforged parts of the ingots and numbered. The ten pairs of specimens were submitted to Louis E. Endsley, Professor of Railway Mechanical Engineering, University of Pittsburgh; A. N. Talbot, Professor of Applied Mechanics, University of Illinois; L. Z. Slater, chief chemist, Scullin Steel Co., St. Louis, Mo. NO information was furnished as to which specimens were forged or unforged and each laboratory used the same specimens, submitting the average of three independent determinations, a tabulation of which is shown in the accompanying table in which the laboratories are designated by the letters A, B, and C. While there is considerable difference in the individual determinations for a number of the specimens, the averages

Jan 1, 1920

By K. Thirumalai

Although the term "spalling" has long been known, Norton l first referred to its usage for the fracture or disintegration of materials subjected to rapid temperature changes. Spalling of ceramic materials at high temperatures has received attention in the past.2-4 Removal of the char formed during ablation in reentry of space vehicles has been referred to as mechanical spalling.5 The first experiments to evaluate the process of rock fragmentation by thermal spalling were conducted by Stoces6 using a series of gasoline burners on the quartz veins of the Zinnwald deep mines in Germany. After the development of rocket-jet burners, the principles of thermal spalling combined with high fluid momentum found wide practical application in rocks. The well-known jet piercing process for drilling blastholes in taconite and for jet channeling in the quarrying of granite are among the more notable of these application.7 For the purposes of this study, thermal spalling or spallation of rocks is defined as progressive failure caused by thermal stresses induced by a sudden application of heat from a high temperature heat source. Gray observes that the size of the spall is dependent on the pattern of induced thermal stresses before failure. The spallability or the relative susceptibility of rocks to failure by thermal spalling is a complex but potentially useful parameter for qualitative comparisons. Fundamental differences exist in the degree of spallability among different types of rocks. Accurate prediction of spallability of any particular rock has so far not been possible. Measurement of the state of stress and temperature in the rock during the rapid thermal spalling process poses difficult problems that must be solved. Identifying the parameters that influence the thermal spalling proc-

Jan 1, 1970

Jan 1, 1967

By W. T. Lankford, Edward Saibel

During the course of an investigation of the plastic flow of aluminum aircraft sheet under combined loads, several problems arose in which analyses of the conditions leading to unstable plastic flow were needed. In order to provide these analyses, and in the hope of attaining a better understanding of the general problem of unstable plastic flow, the present study was undertaken. It is well known that unstable plastic flow is associated with a form of mechanical instabi!ity frequently observed during the plastic deformation of ductile metals. This instability is characterized by the fact that, at its onset, plastic straining mill proceed at a constant magnitude of the externally applied forces. It is further typical that the resulting unstable flow is generally accompanied by the formation of a neck, a local bulging, or some other form of heterogcneous deformation. Perhaps the most familiar example of unstable plastic flow to the metallurgist is the formation of the neck in the ordinary tension test. It is well known that in this test most metals exhibit a maximum in the externally applied load, followed by the process commonly referred to as "necking down." Instability in the simple tension test has been frequently discussed and numerous investigators1'2'3'12 have derived the criterion for instability in terms of a critical rate of strain hardening. It is the purpose of the present study to extend the criterion for unstable flow to the more general case where the body undergoing flow is subjected to combined loads. It is hoped that the problems considered will provide a more consistent picture of the general features of this important form of mechanical instability. The most practical implications of instability in plastic flow arise in connection with sheet metal forming operations. In the formation of a great many sheet metal parts, the deformations are produced primarily by stretching. If the conditions which lead to unstable flow are fulfilled in such a formation, and if the resultant instability leads to a pronounced localization of flow, then the useful limit of ductility of the material will have been reached. It i; also essential that the effects of instability be taken into consideration in any study of the plastic flow and rupture of metals under combined stresses. In general, when unstable plastic flow is initiated, straining becomes localized, the geometry of the test splecimen changes, and the state of stress in that portion of the specimen undergoing plastic flow is no longer under external control. In many past studies of the effects of combinetl Metals On flow and rupture) account has not been taken of the fact that, although a given test may be started under constant

Jan 1, 1947

By Edward Saibel, W. T. Lankford

During the course of an investigation of the plastic flow of aluminum aircraft sheet under combined loads, several problems arose in which analyses of the conditions leading to unstable plastic flow were needed. In order to provide these analyses, and in the hope of attaining a better understanding of the general problem of unstable plastic flow, the present study was undertaken. It is well known that unstable plastic flow is associated with a form of mechanical instabi!ity frequently observed during the plastic deformation of ductile metals. This instability is characterized by the fact that, at its onset, plastic straining mill proceed at a constant magnitude of the externally applied forces. It is further typical that the resulting unstable flow is generally accompanied by the formation of a neck, a local bulging, or some other form of heterogcneous deformation. Perhaps the most familiar example of unstable plastic flow to the metallurgist is the formation of the neck in the ordinary tension test. It is well known that in this test most metals exhibit a maximum in the externally applied load, followed by the process commonly referred to as "necking down." Instability in the simple tension test has been frequently discussed and numerous investigators1'2'3'12 have derived the criterion for instability in terms of a critical rate of strain hardening. It is the purpose of the present study to extend the criterion for unstable flow to the more general case where the body undergoing flow is subjected to combined loads. It is hoped that the problems considered will provide a more consistent picture of the general features of this important form of mechanical instability. The most practical implications of instability in plastic flow arise in connection with sheet metal forming operations. In the formation of a great many sheet metal parts, the deformations are produced primarily by stretching. If the conditions which lead to unstable flow are fulfilled in such a formation, and if the resultant instability leads to a pronounced localization of flow, then the useful limit of ductility of the material will have been reached. It i; also essential that the effects of instability be taken into consideration in any study of the plastic flow and rupture of metals under combined stresses. In general, when unstable plastic flow is initiated, straining becomes localized, the geometry of the test splecimen changes, and the state of stress in that portion of the specimen undergoing plastic flow is no longer under external control. In many past studies of the effects of combinetl Metals On flow and rupture) account has not been taken of the fact that, although a given test may be started under constant

Jan 1, 1947

By M. J. Pearse

The processing of fine particles inevitably produces slimes. These present a dewatering problem, for which gravity thickening provides a partial or preliminary solution. The paper shows the effects of practical factors in carrying out laboratory sizing tests for thickeners. Several methods of determining thickener unit area have been compared for a lightly coagulated phosphate slurry and a highly flocculated kaolin slurry. Practical techniques of mixing and flocculant addition have significant effects on batch settling data. Pulp temperature and cylinder dimensions are very important. Errors in sizing thickeners for highly flocculated slurries by the standard methods are discussed. Such methods are suitable for less compressible slurries, however. Rules of thumb for flocculant selection are given.

Jan 1, 1980

By J. R. Low, M. Gensamer, W. T. Lankford

THE problem of sheet metal formability is one which has received a vast amount of attention during recent years. In spite of the great amount of study and experimental work which has been devoted to this problem, many of its fundamental aspects are still not well understood. No generally satisfactory test has been developed which is capable of providing a reasonably adequate evaluation of sheet metal formability, particularly in borderline cases. Anomalies persistently arise in which a lot of supposedly satisfactory material exhibits excessive breakage when formed. This lack of suitable technological tests greatly hinders the design of new parts and the substitution of new materials in parts of existing design, frequently necessitating considerable costly trial and error experimentation on an actual production basis. When, at the beginning of World War II, it became apparent that mass production methods of forming would be required in the aircraft industry if the large numbers of military aircraft needed were to be supplied, renewed attention was focussed on the problem of sheet metal formability. It was widely recognized that the formability requirements placed on sheet metals had been steadily increasing in severity through the years, especially as greater and greater emphasis was placed on streamlined designs with the resultant freer application of doubly curved surfaces. The recent advent of several new high strength aluminum alloys of more limited formability than some of the older alloys also served to emphasize the need for new approaches to the problem. It seemed evident that progress in the technology of sheet metal forming would depend to a great extent on the development of more reliable criteria for the evaluation of formability. Although the problem is admittedly very complex, the most logical approach appeared to be through studies of the fundamental material properties of sheet metals, especially under complex stress conditions simulating those prevailing in actual forming operations. Most previous investigations have failed to make full use of existing knowledge of fundamental material properties, and in many instances have attempted correlations with properties which are now recognized as being ambiguous in nature. This investigation was undertaken, therefore, with the aim of developing methods for the study of the flow and fracture of sheet metals under combined stresses, and of making use of such methods as might be developed in

Jan 1, 1947

By N. Mungan

Formation damage, i.e.. reduclion in permeability, has been generally attribuled to clay minerals which expand or disperse upon contact with water that is less saline than the connate water. Luboratory, studies show that penneahility reduction can also occur in formalions containing only nonexpandable clays such as illite or kaolinite, and can be caused also by changes in pH. Furthermore, pH changes can damage even formations that are essentially free of clays. It is suggested that permeability reduction is due to the small passages being blocked by particles, which may be dispersed clays, cemenlion material or other fine parricles. These particles are dislodged by dispersion of clays due to changes in salinity or by dissolution of calcareous cement by acids, or of silicaceous cement by alkaline solutions. In working with reservoir cores, it was found that extracted cores damaged more easily and extensively than nonextracted cores. The extent of damage depended also on tenlperatltre. INTRODUCTION Permeability is an important property of porous media and has been the subject of many studies by engineers and geologists. Many of these studies are conccrned with formation damage, i.e., reduction in permeability, resulting from exposure of oil-producing formations to water substantially less saline than the connate water. This effect causes understandable concern since during drilling, completion and production phases formations are often exposed to fresh water. The damage resulting from contact with relatively fresh water has been attributed to expansion and dispersion oF clay minerals. During laboratory investigation of the use of NaOH as a wettability reversal agent to increase oil recovery from oil-wet reservoirs, several cores used in the displacement studies suffered loss in permeability. Despite the traditional usage of NaOH for conditioning aqueous mud systems, the role of the caustic filtrate in wellbore damage seems to have been overlooked. Browning2 as recently reported on the effects of NaOH in dispersing clay minerals but he was concerned only with complications that may arise in drilling massive shale beds. The following study was made to examine the role of pH and salinity changes in core damage. Where cores from reservoirs were used, tests were performed with extracted and nonextracted cores both at room and reser- voir temperatures, since it was felt that the test environment and core condition may affect the results. Because of its limited coverage and exploratory nature, this study is not intended to provide answers to field formation damage problems. It is hoped that it will encourage research into new aspects of the permeability reduction problems, particularly those allied to new recovery and production processes. PROCEDURE In all permeability tests, fluids were pumped through the cores at a constant volumetric rate. Only deaerated fluids and reagent grade chemicals were used. The fluids were passed through two ultrafine filters before injection to remove any entrained particles. The cores, with the exception of the unconsolidated cores, were mounted in Hassler holders. Water was used to transmit pressure to the sleeve. The inlet endpiece had two entry ports which permitted scavenging one fluid with another to avoid any mixing in the small holdup volume. The cores were flushed with CO2 gas, evacuated for 5 to 6 hours and saturated with the first liquid at a pressure of 1,000 psi for 24 hours to eliminate any free gas from the cores. Pressure differences up to 20 psi were measured by transducers, calibrated in inches of water and continuously recorded. For greater pressure drops, gauges were used. All reservoir cores were cleaned with a light refined mineral oil, then with heptane, and finally dried with CO2. Compatibility tests showed that no precipitates formed when mineral oil and the crudes were mixed. Some cores were extracted in Dean-Stark-type solvent extractors using xylene and trichloroethane and dried in a vacuum oven at 450F. Each test consisted of a sequence of water, test solution, and again water flow. RESULTS AND DISCUSSION STUDIES IN BEREA CORES Salinity Contrast Berea cores 2-in. in diameter and 12-in. long were cut from sandstone quarried in Cleveland, Ohio. The clay minerals were identified by X-ray diffraction to be chlorite, kaolinite, illite and incerlayered illite. Flow of fresh water or 30,000 ppm brinc does not cause any permeability reduction (Fig. 1). However, after injection of brine the core is readily damaged by fresh water. Damage starts almost instantly as the fresh water injection is begun, and at a cumulative injection of 1.2 PV fresh water, the permeability has dropped from 190 to 0.9 md. Upon continued injection, the effluent contains clay minerals dislodged from the core. The final core per-

Jan 1, 1966

By John Griffen

This paper records over twenty years' experience with the use of the Rheolaveur system in the United States, showing its ability to meet changing conditions caused by the dirtier mine output of present-day mechanical mining methods. Data are given on size ranges handled, number and capacity of units installed, maintenance experience, and operating results on two-product and three-product separations. IT is not the purpose of this paper to discuss the principles employed in the Rheolaveur system of fine-coal cleaning as these have been fully covered in the technical literature of the Institute."2 Rather, our purpose will be to record the highlights of over 20 years' experience in the United States with Rheolaveur fine-coal launders, which will indicate their capabilities and costs of cleaning and their adaptability to meet the changing conditions caused by present-day mechanical mining methods. Rheolaveur fine-coal launders are used in the United States to treat a wide variety of size ranges of fine coal, the coarsest being 1/2 in. to 0 and the finest about 1/8 in. to 0. In Europe feeds as coarse as 5/8 in. and as small as 1/2 mm (28-mesh) to 0 are being cleaned. The size ranges usually handled in this country are 3/8 to 1/4-in. round to 0. Thirty five units with a combined hourly feed capacity of 3200 tph have been installed in the United States. Individual units are cleaning as little as 25 tph, while others are cleaning as much as 200 tph. Rheolaveur fine-coal launders offer cleaning units of high capacity and are outstanding in requiring a minimum of building space per ton of input. Experience has shown that maintenance costs are low. Several installations were made in the Pittsburgh district from 1928 to 1930, and since that time operation has been largely two shifts per day. Minor repairs to liner plates and Rheo boxes have been required during the intervening years, but no major replacement of launders was required until 1947 and 1948. At one of these plants, launders operated for 17 years before they were replaced and during that period over 26,000,000 tons of —5/16-in. coal were cleaned. The effect of the much dirtier raw coal produced by mechanical loading of the Pittsburgh seam is shown by the following tests. The data in table I summarize the performance of a Rheo fine-coal unit when cleaning hand-loaded raw coal. The —4-in. raw coal fed to the cleaning plant analyzed only 8.16 pct ash and 1.31 pct sulphur and contained 4.6 pct sink, 1.55 sp gr. Two years later, in 1945, mechanically-loaded coal from the same mine was cleaned in the same plant. The feed, —4 in., then analyzed 20.10 pct ash and 1.53 pct sulphur and contained 20.2 pct sink, 1.55 sp gr. The performance of the Rheo fine-coal unit when cleaning this coal is given in table 11. It will be noted that the +48-mesh coal is cleaned almost as thoroughly as in table I. The large amount of high-ash slimes produced from the dirtier feed are responsible for the higher ash of —--48-mesh washed coal in table 11. In this plant the Rheo fine-coal unit did not get the full load of refuse resulting from mechanical

Jan 1, 1951

By John Griffen

This paper records over twenty years' experience with the use of the Rheolaveur system in the United States, showing its ability to meet changing conditions caused by the dirtier mine output of present-day mechanical mining methods. Data are given on size ranges handled, number and capacity of units installed, maintenance experience, and operating results on two-product and three-product separations. IT is not the purpose of this paper to discuss the principles employed in the Rheolaveur system of fine-coal cleaning as these have been fully covered in the technical literature of the Institute."2 Rather, our purpose will be to record the highlights of over 20 years' experience in the United States with Rheolaveur fine-coal launders, which will indicate their capabilities and costs of cleaning and their adaptability to meet the changing conditions caused by present-day mechanical mining methods. Rheolaveur fine-coal launders are used in the United States to treat a wide variety of size ranges of fine coal, the coarsest being 1/2 in. to 0 and the finest about 1/8 in. to 0. In Europe feeds as coarse as 5/8 in. and as small as 1/2 mm (28-mesh) to 0 are being cleaned. The size ranges usually handled in this country are 3/8 to 1/4-in. round to 0. Thirty five units with a combined hourly feed capacity of 3200 tph have been installed in the United States. Individual units are cleaning as little as 25 tph, while others are cleaning as much as 200 tph. Rheolaveur fine-coal launders offer cleaning units of high capacity and are outstanding in requiring a minimum of building space per ton of input. Experience has shown that maintenance costs are low. Several installations were made in the Pittsburgh district from 1928 to 1930, and since that time operation has been largely two shifts per day. Minor repairs to liner plates and Rheo boxes have been required during the intervening years, but no major replacement of launders was required until 1947 and 1948. At one of these plants, launders operated for 17 years before they were replaced and during that period over 26,000,000 tons of —5/16-in. coal were cleaned. The effect of the much dirtier raw coal produced by mechanical loading of the Pittsburgh seam is shown by the following tests. The data in table I summarize the performance of a Rheo fine-coal unit when cleaning hand-loaded raw coal. The —4-in. raw coal fed to the cleaning plant analyzed only 8.16 pct ash and 1.31 pct sulphur and contained 4.6 pct sink, 1.55 sp gr. Two years later, in 1945, mechanically-loaded coal from the same mine was cleaned in the same plant. The feed, —4 in., then analyzed 20.10 pct ash and 1.53 pct sulphur and contained 20.2 pct sink, 1.55 sp gr. The performance of the Rheo fine-coal unit when cleaning this coal is given in table 11. It will be noted that the +48-mesh coal is cleaned almost as thoroughly as in table I. The large amount of high-ash slimes produced from the dirtier feed are responsible for the higher ash of —--48-mesh washed coal in table 11. In this plant the Rheo fine-coal unit did not get the full load of refuse resulting from mechanical

Jan 1, 1951

By A. G. Paithankar, G. B. Misra

Although certain physical mechanical properties of rocks have been claimed to give an estimate of penetration rate in percussive drilling, the authors' work shows that the correlation of penetration rate with individual rock properties is Poor. The authors have developed a good correlation between penetration rate and a set of rock properties but the relation is complex. Energy per unit volume has been used as a measure of penetration rate in percussive drilling by Hustrulid and Fairhurst; however, their test setup is large wing a full size drill bit. The authors determined the minimum energy for unit volume Ev min for any rock at the optimum index angle in a simple laboratory drop tester wing a sharp microbit with a tip angle of ll0°. This Ev min has been found to correlate well with penetration rate obtained in controlled laboratory drilling in different rocks for different stages of bit wear. A comprehensive relation has been developed between penetration rate and Ev min.

Jan 1, 1981