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By H. Kazemi

An ideal theoretical model of a naturally fractured reservoir with a uniform fracture distribution, motivated by an earlier model by Warren and Root, has been developed. This model consists of a finite circular reservoir with a centrally located well and two distinct porous regions, referred to as matrix and fracture, respectively. The matrix has high storage, but low flow capacity; the fracture has low storage, but high flow capacity. The flow in the entire reservoir is unsteady state. The results of this study are compared with the results of the earlier models, and it has been concluded that major conclusions of Warren and Root are quite substantial. Furthermore, an attempt has been made to study critically other analytical methods reported in the literature. In general, it may be concluded that the analysis of a naturally fractured reservoir from pressure transient data relies considerably on the degree and the type of heterogeneity of the system; the testing procedure and test facilities are sometimes as important. Nevertheless, under favorable conditions, one should be able to calculate in-situ characteristics of the matrix-fracture system, such as pore-volume ratio, over-all capacity of the formation, total storage capacity of the porous matrix, and some measure of matrix permeability. INTRODUCTION The analysis of flow and buildup tests for obtaining in-situ characteristics of oil and gas reservoirs has received considerable attention in the past decade. Most of the available techniques result in reliable conclusions in macroscopically homogeneous reservoirs or in the homogeneous reservoirs with only certain types of induced and/or inherent heterogeneity (such as wellbore damage, etc.). In general, the greater the degree of heterogeneity, the less the reliability of the information deduced from the pressure transient data. A commonly encountered heterogeneous system is a naturally fractured reservoir where two types of distinct porosities occur in the same formation. The region containing finer pores may have high storage and low flow capacities. This is called the matrix. The remaining region may have high flow capacity with low storage. The latter region is generally the set of interconnecting fractures and fissures of the rock, and for this reason it is called the fracture. Ordinarily, we wish to obtain the permeability and porosity of each region and perhaps the frequency of the fracture distribution in a reservoir. Such information is necessary for reservoir engineering. Other information, such as wellbore damage, will be useful in evaluating possible remedial work for such fields. Few authors have suggested theories to aid in calculating the in-situ characteristics of a naturally fractured reservoir similar to what we have described above. Pollardl suggested that a naturally fractured reservoir contained three distinct regions: a damaged or an improved region surrounding the wellbore, and the two remaining regions the same as described earlier. He suggested that the flow was taking place from the tight matrix into the highly conductive fractures, then into the we wllbore region and finally into the well column. He concluded that the average pressure buildup in each of these distinct regions can be expressed approximately in terms of an exponential decay function of time. He also hypothesized that the decay coefficients for each of these functions were significantly different from each other; consequently, each of these functions became dominant in turn, in the process of pressure buildup. Thus, by a proper graphic plot of the logarithm of wellbore pressure differences vs buildup time, each of these functions could be determined (see Fig. 1). Pollard suggested methods of determining the wellbore damage and fracture volume. Later Pirson and Pirson2 extended

Jan 1, 1970

By P. M. Kelly, E. P. Butler

The stability of a 70/30 Mn-Cu alloy aged to peak damping has been investigated using electron microscopy, X-ray diffraction, and torsional pendulum measurements. Storage at room temperature or at 100" C causes a reduction in damping capacity. This is shown to be due to the formation of subdomains which "lock" the main domain structure and so hinder their movement. After storage the damping capacity can be restored by a retransformation treatment, which generates structures identical to those found in newly aged specimens. Plastic deformation by rolling also causes a decrease in damping capacity. In this case the damping capacity can only be restored by retransformation if the amount of deformation is less than about 5 pct. THE general metallography and structure of these high damping capacity alloys has been discussed in Part I of this work.1 Part II deals with some of the variables that affect the damping capacity. In particular, the stability of the damping capacity of a 70/30 alloy aged for 2 hr at 425° C and quenched has been investigated. The temperature sensitivity of the damping capacity of a 70/30 alloy aged for 2 hr at 450° C has been reported by Birchon.2 The damping capacity begins to decrease with increasing temperature, and is very low above the M, temperature of 125°C. The cubic — tetragonal transformation is completely reversible and there is no apparent thermal hysteresis associated with the change in damping capacity. Another important effect was first reported by Dean and his coworkers.3 They noticed a decrease in the damping capacity with time for specimens of a quenched tetragonal alloy. More recently workers at the Admiralty Materials Laboratory 4 have studied the stability of an aged 70/30 alloy. They found that the damping capacity decreased to half its original value after about 1000 hr at room temperature. EXPERIMENTAL The techniques used for electron microscopy and X-ray diffraction have been described in Part I. The damping capacity was measured by means of a torsional pendulum, using rectangular specimens, 3 by 0.3 mm with a 6 cm gage length. The specific damping capacity, S.D.C., was calculated as a percent amplitude decay in free vibrations over 10 cycles, starting at an amplitude which corresponded to a 700 psi surface shear stress. Because of the stress dependence of the damping,' the values obtained were about a third those reported for a 5000 psi surface shear stress.' RESULTS a) Effect of Aging Temperature. The effect of aging temperature on the damping capacity is shown in Fig. 1. The damping capacity reaches a peak of 12 pct after aging at 400° to 425°C) then begins to decrease as the volume fraction of a Mn increases. At higher aging temperatures the structure becomes cubic again with a low damping capacity. b) Stability of the Aged Structure. The damping capacity of the aged alloy decreases with time at room temperature. This process could be accelerated by storing at 100°C, when about 100 hr were required for the damping to fall to half its original value. The results of room temperature and 100°C storage, for times up to 1000 hr, are shown in Fig. 2. The damping capacity starts to decrease after about 24 hr at 18° C and 1 to 2 hr at 100°C. It was found, however, that the damping could be almost completely restored by retransformation. The specimens were held at a temperature above the M, for a short time, 250° C for 5 min, and then quenched. The values of damping capacity for specimens that were aged, stored, and then retransformed are shown by the full points in Fig. 2. X-ray measurements of the c/a ratio and hardness readings on the specimens did

Jan 1, 1969

By C. L. Ray, R. E. Baarson, H. B. Treweek

As an example of nonmetallic mineral flotation, the separation of several pegmatite minerals will be discussed in considerable detail, from both the laboratory-testing and plant-operation standpoints. The pegmatites have been chosen to illustrate the practicality of the selective separations of the minerals in a complex nonmetallic ore and, in so doing, to set forth a summation of the flotation art and technology which is applicable in part to the beneficiation of several less complex nonmetallic ores. In addition, a brief summary of descriptions of other nonnietallic mineral flowsheets and separations is included. Some of the industrial minerals now being concentrated by froth flotation methods commercially, or in the laboratory, are listed in Table 1. GENERAL CONSIDERATIONS There are two classes of chemicals that are normally utilized as collectors in froth flotation separations of nonmetallic minerals. These are defined as anionic and cationic and are typified by the fatty acids and amines, respectively. The fatty acids are selective to those minerals that have a high concentration of positive surface charges, such as the various calcium minerals typified by calcite, phosphate rock, and fluorspar. The amines are selective to those minerals with a high concentration of negative surface charges, such as silica sand and silicates. It should be noted, however, that by using various inorganic chemicals, a new or synthetic surface can be placed on specific minerals which produces different characteristics, thereby reversing the flotation reagent required for separation. The polar end of the collector attaches to the mineral surface either by chemical or physical adsorption; the nonpolar unreactive end is oriented away from the mineral surface. The result is a hydrophobic coating at the mineral surface which causes attachment to air bubbles. It is this surface condition that permits the floating of minerals which normally sink in water. In order to utilize these fatty acids and amine derivatives, several conditions .must be fulfilled. Before there can be a selective flotation process,

Jan 1, 1962

By Alfonso Merlini

DIFFERENT explanations have been given by the two current theories of the annealing textures for the variation of annealing texture with the annealing temperature observed in rolled polycrystal-line aluminum,' copper,2 and brass, And in rolled single crystals of copperk and silicon iron.' The theory

Jan 1, 1957

By Arthur W. Gray

The thermal analysis of a metal or an alloy is ordinarily made with the aid of heating and cooling curves in which transitions are indicated by the rapid changes in curvature that accompany changes in the rate of heat absorption or evolution. Analysis by the method that depends on the change in thermal expansivity is not customary, partly, at least, because of the difficulties involved in making the necessary measurements. However, under certain circumstances, the dilatometric method of analysis may possess advantages over the thermometric method that will justify the additional trouble required. The addition of 1 per cent. of zinc to an alloy has been found to produce upon the volume changes that take place during transition effects that suggest the possibility of using the dilatometric method of thermal analysis as a rather sensitive means of obtaining chemical information. Although the illustrations presented in this paper are drawn from data obtained during an investigation of dental amalgams, similar phenomena can doubtless be observed with other alloys. Some of the results found during an investigation made in 1917l have been confirmed by data on the thermal expansivity of amalgams published by Souder and Peters of the Bureau of Standards in reporting tests of dental materials.2 Although the Bureau of Standards made experiments for the purpose of discovering effects of including zinc as one of the constituents of a dental alloy—a matter much discussed in dental literature but without the presentation of reliable experimental evidencae to support the views of either side—the reports of the tests made by the Bureau give the impression that certain striking phenomena associated with the presence of zinc were not noticed. Among such phenomena arc those connceted with the conditions that determine whether or riot a specimen of amalgam becomes covered with droplets from which crystals develop.

Jan 1, 1921

By H. J. Hand

STATISTICAL methods are becoming increasingly important for inter-preting routine reports, or for analyzing special test data in industrial plants, such as steel plants. They have already become practically a necessity to the plant metallurgist. A paper by Chancellor,1 written in 1933, gives many examples of the benefits the plant metallurgist can derive from the use of these methods. The present paper discusses applications of importance to many others who must analyze reports in the steel plant, as well as other examples of interest to metallurgists. Statistical Methods Logically Suited to Plant Problems.-Statistical methods are not new as a branch of mathematics. Until comparatively recently, however, practical applications were confined mainly to actuarial science, biology, and economics; fields in which an observed result is obviously influenced (and often determined) by a complicated set of vari-ables more or less constantly tending to affect it. As pointed out by Daeves, 2 a decade or more ago, problems in industry are basically similar to those in these other fields in that a given result is at least partly due to that chance combination of causes happening to be present at the time. When trying to do the same thing repeatedly, constant results are never attained; they vary about the desired result with more or less well defined mathematical regularity. Such a condition arises out of the great number of factors tending to affect the final result. If statistical methods are so valuable to the biologist or economist, why then should they not also be of great value to plant managers and engineers, and to all who must interpret reports from various sources in the industrial plant? Within the last few years, industry has become conscious of this situation, and the use of these methods has been rapidly expanding in such plants. ?

Jan 1, 1938

By Georg Masing

Jan 1, 1933

By R. H. Heyer, J. L. Bray, M. E. Carruthers

It is well known that iron markedly improves the physical properties and casting characteristics of aluminum bronzes. The use of 1 to 4 per cent iron as the principal modifying addition has become common practice in many foundries melting aluminum bronzes. Although the beneficial effects of iron are unquestioned, there is some uncertainty regarding the structural changes caused by it in the basic copper-aluminum system. It is agreed that a new constituent appears in abundance when the iron content reaches 2 to 4 per cent. This constituent, which frequently occurs in shapes resembling clover leaves, is sometimes assumed to be an aluminum-iron intermetallic compound. If this were correct we might expect a change in the structural relationships of the matrix in the direction of decreased aluminum content. On the other hand, it has been reported that iron has a negligible effect in altering the fundamental relationships of copper-aluminum alloys1 Others2'3 have reported an additive coefficient. Apparently it will be necessary to know the equilibrium relationships between the phases of the copper-aluminum-iron alloy system to establish any such theory as fact. When this has been done it may very well be that a further revision in the structural relationships may be necessary to describe the changes to be expected in commercial cast alloys. It was with this latter problem before them that the authors attempted to determine the change in the copper-aluminum relations with respect to iron. Objects of the Investigation In certain investigations carried out by the authors for a plant producing a large tonnage of cast aluminum bronzes the structures

Jan 1, 1936

By R. P. Ehrlich, D. A. Dahlstrom

In the hydrometallurgical circuit, many phase separation steps are usually necessary. Typical steps are pregnant liquor - leach residue separation by counter- current decantation or continuous vacuum filtration, clarification of liquids prior to precipitation, ion exchange or solvent extraction, dewatering of final product, etc. The paper discusses the more recent advances in these areas and considers general operating parameters and cost factors. In addition, emphasis is placed on future needs because of the growing importance and necessity of hydrometallurgical processing of minerals.

Jan 1, 1973

By Anson Hayes, John Chipman

The quality of sheet and strip products made of rimming steel is closely related to the structure and chemistry of the ingots. The variation in composition throughout the ingot, as affected by segregation, is of great importance, as are also the form and distribution of the voids that result from the gases evolved. It is because of this importance that the considerable literature in this field has accumulated. No attempt is made in the present paper to compile a bibliography of the excellent work that has already been done, as this has been adequately covered in the many excellent reports on the heterogeneity of steel ingots prepared by a joint committee and published by the Iron and Steel Institute.' From time to time, in any field of investigation new tools and new technique are developed, which make further progress possible. In the field with which this paper is concerned, this is true. The development of the vacuum-fusion method as a means of following oxygen segregation, and a technique for obtaining the volume and composition of the gases evolved during solidification, have opened the way to obtaining data by means of which some considerable progress has been realized in developing more of the detailed mechanisms of solidification and segregation in rimming-steel ingots. General Theory of Segregation The basic cause of segregation lies in the fact that the impurities are less soluble in solid than in liquid iron. The solid that forms from the impure liquid is more nearly pure than the liquid itself. If solidification proceeds slowly enough, or if the liquid and solid phases are maintained in contact with one another for a sufficient time, a condition of equilibrium is set up, which may be represented by a phase diagram. Portions of the

Jan 1, 1939

By J. J. Arps

n approach to the study of the electrical properlies of drilling muds, their cakes and their filtrates was made by treating the drilling fluid as a porous medium. Lluring this study it was found that the weight pararneter was omitted from previous investigations on electrical properties. Patnode in 1949 made a similar approach to ,his investigation. His work showed that there was a variation of resistivity relationships with per cent Puid present in a given suspension. This present study ex-tends Patnode's investigation to one in terms of the solids fraction of the drilling fluids. Previous investigations were made on low weight muds where the effect of the rolids fraction was obscured. The following equationr were fitted to data taken from 94 field muds and 47 laboratory muds (see Tables I and 2). The parameter, C, is a complex function of the solidr content, or mud weight, of a drilling fluid. It was also found that for all drilling muds examined. A nomograph is presented combining Eqs. I and 2. INTRODUCTION It is generally recognized that the materials present in drilling muds affect the relationship between mud filtrate and mud resistivities. However, most electric log interpretations proceed with the assumption that the mud resistivity and temperature are the only important parameters needed to obtain a filtrate resistivity or a mud cake resistivity. Lamont1 suggests that only average relationships exist between mud cake, mud filtrate and mud resistivities. He indicates that there is limited accuracy when these intercorrelated factors are used since no other measure-able variable is apparent. A previous paper by Patnode indicates that drilling fluids may be considered to be a system of fluids in solid particles which may be correlated electrically in a manner similar to rock solids. 1 he equation for the resistivity factor. F = (per cent fluid) is satisfied for a given clay type in water, but the value of m varies as different materials are used in the water. The resistivity factor is not constant for a given amount of clay. As is suspected it varies as the solids fraction conducts electrical current. Since both weighting material and clay solids are present in commonly used drilling fluids, it is expected that both materials contribute to the variation of the m factor in Eq. 3. An extension of Patnode's work is presented in this paper to show some of the interrelations which exist between the resistivities of mud cake, mud filtrate and mud. Use of these data enable a more accurate calculation of mud filtrate and mud cake resistivities if only the mud resistivity and weight are measured. EXPERIMENTAL The measurements of mud weight, fluid and solids resistivity, alkalinity, and chloride content of mud samples were made in this research. Mud samples representing drilling fluids from 94 Louisiana and Texas wells (Table 1) and 47 laboratory-constructed systems (Table 2) were used in the experimentation. The measurements of the mud properties were made both in the field and in the laboratory. The tests on the properties of weight, alkalinity and chloride ion were standard tests as described by API specifications. The resistivity measuring devices were constructed in the laboratory for this study. For details on the resistivity equipment see Fig. 1. The fluid cell

By Anson Hayes, John Chipman

The quality of sheet and strip products made of rimming steel is closely related to the structure and chemistry of the ingots. The variation in composition throughout the ingot, as affected by segregation, is of great importance, as are also the form and distribution of the voids that result from the gases evolved. It is because of this importance that the considerable literature in this field has accumulated. No attempt is made in the present paper to compile a bibliography of the excellent work that has already been done, as this has been adequately covered in the many excellent reports on the heterogeneity of steel ingots prepared by a joint committee and published by the Iron and Steel Institute.' From time to time, in any field of investigation new tools and new technique are developed, which make further progress possible. In the field with which this paper is concerned, this is true. The development of the vacuum-fusion method as a means of following oxygen segregation, and a technique for obtaining the volume and composition of the gases evolved during solidification, have opened the way to obtaining data by means of which some considerable progress has been realized in developing more of the detailed mechanisms of solidification and segregation in rimming-steel ingots. General Theory of Segregation The basic cause of segregation lies in the fact that the impurities are less soluble in solid than in liquid iron. The solid that forms from the impure liquid is more nearly pure than the liquid itself. If solidification proceeds slowly enough, or if the liquid and solid phases are maintained in contact with one another for a sufficient time, a condition of equilibrium is set up, which may be represented by a phase diagram. Portions of the

Jan 1, 1939

By Kenneth K. Humphreys, J. W. Leonard, T. S. Spicer

INTRODUCTION Reasons for Thermal Drying The continuing increase in the percentage of - '/4 in. ( -6.3 mm) coal produced as a result of the increased use of mechanical mining methods has, over the years, tended to shift considerable portions of the work of producing salable coal to the fine coal cleaning section of the preparation

Jan 1, 1979

By H. Rosenthal, A. L. Jamieson

Stress-corrosion cracking of copper-base alloys is of considerable importance and has been the subject of many investigations which employed various accelerated tests and long-time service tests. The outstand¬ing accelerated tests used are variations of either the mercury cracking test reported by Rogers in 1905( 1)2 or the ammonia test reported in 1910(2). The ease of applica¬tion of the mercury test is probably the reason industry adopted it. Subsequent investigation of this test(3,4) revealed that a minimum threshold stress was necessary before mercury cracking could develop. Since season cracking has been found in some instances in caliber 0.3o ammunition which has passed the mercury test, it is evident that the threshold stress value of the mercury test may be too high for dis¬tinguishing between acceptable and un¬acceptable caliber 0.30 cartridge cases. This condition has naturally led to the study of an ammonia test with its ability to cause cracks with almost any stress level. But the lack of a definite threshold value means that standards are necessary for evaluating the results of the ammonia test.

Jan 1, 1945

By D. T. Novick, M. B. Bever, B. Roessler

Ordered and disordered specimens of the alloy CusAu were cold worked and then annealed at 2880, 310°, and 340°C, together with disordered unworked specimens. me resistivity decreased during annealing mainly as a result of ordering; the resistivity measurements suggest that in cold-worked specimens the growth of antiphase domains is impeded. The strength properties increased during annealing at 288 "C; in cold-worked specimens this increase was lo a level above that for cold-worked specimens which had not been annealed. X-ray diffraction showed that after annealing for a few hours at 288ºC, the long-range order increased to a constant value; additional annealing at 288ºC resulted in the growth of antiphase domains in which the degree of order was constant. Changes in peak breadth and particle size confirmed that in cold-worked specimens the major effects of cold work were not eliminated during annealing at 288 "C, although a slight recovery process occurred. When a specimen of the alloy Cu3Au is heated to a temperature below the critical temperature (388ºC), long-range ordering tends to occur in a specimen containing less than the equilibrium amount of order characteristic of that temperature Ideally, a specimen of Cu3Au contains no long-range order if it has been quenched from above the critical temperature. Long-range order is reduced by cold work. If cold-worked specimens are heated, restoration processes such as recovery and recrystallization may occur,

Jan 1, 1963

By R. W. Carpenter, J. C. Ogle

It is possible, by using pack-rolling instead of conventional rolling, to reduce a number of metals to thicknesses of 2µm or less. Such thinfoils are generally made at room temperature without intermediate annealing. In addition, pack-rolled foils fail by developing pinholes at thicknesses near 2µm instead of developing the shear cracks usually observed in cold-rolled ductile metals. This paper presents the results of a general investigation of the deformation substructure and texture developed in copper and iron pack -rolled from 130 to about 2µm thickness. Electron microscopy showed that in both metals a fine (0.2 to 0.5?µ m) deformation subgrain structure formed during pack-rolling; in neither case was this substructure grossly different from substructures formed during conventional rolling. The deformation texture formed in pack-rolled iron was quite similar to usual bcc textures; however, in the case of copper, the cube texture was stable during pack-rolling and the normal copper deformation texture was unstable. It is shown analytically that the constraining pack induced a large hydrostatic pressure in the foils during pack-rolling. The pinhole failure mechanism is attributed to the presence of the large hydrostatic pressure during pack-rolling; this strongly suppressed the growth of shear cracks. The stability of the cube texture in copper is also probably due to the unusuul stress distribution developed during pack-rolling. EXPERIMENTS at several laboratories have shown that very thin foils of the common structural metals and many of the rare earths can be made by "pack-rolling". 1-3 The technique was originally developed to make specimens for nuclear scattering experiments and foils for X-ray filters. It is also useful for making experimental laminar metallic composite bodies and foils thin enough for direct examination by ultra-high voltage electron microscopy without the need for special thinning techniques. Pack-rolling in the present context means a three-layer pack, with the material to be rolled into foil comprising the center layer. The outer two layers, which constrain the foil during reduction, are ordinarily austenitic stainless steel. Typically, a 130 µm (0.005 in.) metal strip can be reduced to a final thickness of 2 µm or less by this process. This is accomplished at room temperature, without intermediate annealing. It has been observed that foils produced by this process do not exhibit at any stage of their reduction the severe work-hardening found in strip rolled by conventional cold-rolling methods. Neither is the failure characteristic the same."&apos; Conventionally cold-rolled ductile metal strip fails by developing shear cracks on planes whose normals nearly bisect the angle between the rolling direction and normal to the rolling plane; these are planes of maximum shear stress. In pack-rolling this mechanism has not been observed; failure occurs by the formation of pinholes on the foil surface (penetrating the foil). If pack-rolling is continued the hole density increases. These differences in behavior imply the existence of appreciably different substructure in pack-rolled foils compared to substructure in conventionally rolled material, or perhaps that the geometry of pack-rolling has an effect on the foil behavior. This paper describes an investigation of deformation substructure and texture in some specimens of pack-rolled copper and iron, and some considerations of the stress distribution in the foils during rolling that result from the geometry of pack-rolling. EXPERIMENTAL DETAILS Three different materials were used for pack-rolling in the present work: soft copper sheet (99.8 pct Cu, 0.03 pct 0, electrolytic tough pitch) and two types of iron, Ferrovac E* and Armco iron. Each was "Crucible Stccl Co. initially in the form of 130 µm annealed strip with grain size ranges of approximately 10 to 40 µm. The initial texture of the copper (determined as noted below) was the normally observed cube type (001)[100]; there was evidence of a small amount of material in the cube-twin orientation reported by Beck and Hu.4 The initial texture of the Ferrovac E was similar to that reported for recrystallized iron by Kurdjumov and sachs,5 who list the principal orientations as {111}<112>, {001}<110> 15degfrom RD and a weak component {112}(110) 15 deg from RD. The starting texture of the Armco iron was not determined. Pack-Rolling Procedure. A four-high mill was used for all specimens. The work roll and backing roll diameters were 1.625 and 5.25 in., respectively. The peripheral roll speed of the work rolls was about 2.5 in. per sec. All foils were initially reduced from 130 to 100 µm by conventional straight rolling and then inserted into a pack, without any intermediate annealing, for further reduction. The pack consisted of an 0.033 in. (838 µm) thick 3 by 6 in. polished sheet of austenitic stainless steel, folded to make a 3 by 3 in. jacket. After folding, the jacket was given a small reduction to close the fold tightly before insertion of the foil. During pack-rolling a constant change in roll spacing was made every third pass. The roll-spacing change corresponded to a 5 pct reduction in thickness for a new pack. This approached a 10 pct reduction when the pack had decreased to about half its original thickness. At this point the deformed pack was discarded and a new one

Jan 1, 1970

By M. V. Lowry

This paper outlines the economic considerations that led to the recent installation of a thickener at St. Joseph LeadCo.&apos;s Balmat, N.Y. mill. To incorporate storage of concentrates, they decided upon a single, unusually deep tank to be used for both storage and thickening. The abnormally high rake lift required was achieved by the novel feature of having the entire drive platform raise and lower. Initial operating problems are described along with the satisfactory solutions. Total costs for concentrate handling before and after installation of the storage thickeners are compared. In Northern New York State, the St. Joseph Lead Co. conducts a 2100 tpd zinc mining and milling operation at its Balmat Plant. Conventional crushing, grinding, and flotation is used to produce a zinc concentrate. For 32 years, from 1930 through 1962, the plant operated with the concentrates going directly from flotation to the filtering, drying, and loading facilities. All of the concentrate handling equipment, therefore, had to operate 24 hrs per day. It also had to accommodate wide fluctuations in tonnage, due to variations in the grade of ore. Many problems were thereby encountered in filtering and drying, but it was never concluded that the cost could be justified for installing a conventional, large diameter thickener. Finally, in 1963, they installed an unconventional thickener that is unusual in several respects. The tank depth is 16 ft instead of the normal 8 ft. The rakes are raised and lowered by having the main drive gear located on a movable platform. Automatic controls are programmed to raise the drive platform and rakes during one shift of storage. During the next two shifts of withdrawal, the controls are programmed to lower the drive platform and rakes. After three years of operating this unique storage-thickener, the conclusion is that a correct choice was made from several alternative schemes for storing concentrates. The various considerations involved in the final selection will here be analyzed, and the design features and installation details will be de- scribed. Operating problems and modifications made to the equipment will next be considered, and finally the effects upon filtering, drying, and loading will be reported. SELECTION CONSIDERATIONS Even without a thickener, concentrate handling had become reasonably efficient at the Balmat Mill by the year 1962. A tonnage that varied between 6 and 25 tph was being handled fairly satisfactorily. The filter cake moisture of 8%% seemed quite respectable, except that two large filters were usually in service. Three filters often had to be operated in order to prevent excessive filter overflow with consequent loss of values. This situation occurred when zinc concentrates from flotation exceeded 20 tph and when filter cloth blinding developed. Over the years, numerous small improvements had been effected, such as: selection of a filter cloth with better flow characteristics; addition of flocculant to the filter feed; and, in 1953, the smallest of three drum filters was replaced by a five disc, 8&apos; 10" diam filter with a bottom agitator and snap blow. As another example of fairly efficient operation, the oil-fired dryer was doing a seemingly satisfactory job of further reducing the moisture content to an average of 3%. However, there were often considerable dust losses when the tonnage suddenly dropped off to 6 tph. At high tonnage rates, the resulting high moistures of 4% and 5% caused difficulties due to concentrates sticking and freezing in chutes leading to the box car loaders. (Drying of concentrates is justified because of the high freight rate for the long shipping distance to the company owned smelter at Josephtown, Pa. near Pittsburgh.) It was long realized that installation of a thickener would permit the subsequent steps of concentrate handling to proceed more smoothly and would alleviate the problems existing in the filtering, drying, and loading operations. It was also realized that even a slightly lower filter cake moisture could mean considerable savings in fuel oil. However, all these factors were never quite sufficient to warrant the expense of a thickener until three more considerations were added to the picture. First, the advent of flocculants meant that a thickener of relatively small area could now be considered. Secondly, a complete renovation of the zinc flotation circuit was made between 1957 and 1961. The

Jan 1, 1967

By George S. Rice

The increasing use of mechanization at the face of the workings in coal mining and the consequent necessity of special supports of the roof has led, in several countries, to considerable scientific investigation, including physical tests in mines as well as on specimens of roof rocks to obtain data on the behavior of the immediate roof strata and on the effect of its pressure on supports while the coal is being mined. The investigations discussed in this paper do not include studies of the ultimate effect of subsidence and movement of the roof rock over the mine excavation, upon higher strata and the surface, but are confined to the immediate underground effects in the workings. The more recent principal investigations which have been brought to the attention of the writer are as follows: Germany.—The trial of strip packing, the usual method employed in Great Britain in longwall workings, as compared with complete packing heretofore used in Germany and in France to minimize subsidence; the behavior and strength of metal props under load; the testing of the strength of coal measure rocks, in the laboratory of the Technical High School of Breslau; and an investigation, by a special commission, concerning "bumps" as a possible cause of instantaneous outbursts of gas in coal mines of Lower Silesia. France.—The cause of instantaneous outbursts of gas in the Gard mines and tests by the official French experimental organization of the "electrical resistivity" of coal as a possible means of detecting a condition preceding an instantaneous outburst. Great Britain.—The subsidence of the roof and rise of the floor preceding and during excavation of the coal, in longwall and in room-and-pillar or bord-and-pillar workings; the compression and lateral movement of the road packs in longwall back from the face; the extent of separation of the immediate roof layers from the higher strata following mining excavation;

Jan 1, 1932

By Charles W. Goodale

The purpose of this paper is to review the history of the Drumlummon, one of the famous old mines of the West. Mining engineers, when sent to examine new mines in old districts, or, to decide whether an old property, under new conditions, will pay to reopen, have had difficulty in learning anything authentic regarding workings which are under water, and historical facts about the working character of the ore, the total production, and the value of the ore with increasing depth. &apos;Not many years elapse after the pumps are pulled, before maps, books and records are destroyed, and the value of the publications of the Institute would be increased if they contained the history of many old mines now abandoned. The unsuccessful efforts of the writer quite recently in trying to obtain reliable information about a gold mine which was reported to have produced several million dollars between 1880 and 1888, the workings of which are now partially caved and under water, impressed upon his mind the desirability of having a permanent record of old properties. In this particular case, the owners insisted that under present conditions of improved methods of treatment —particularly by the use of cyanide, which was not an applied process when the mine was operated, the property could be made to pay a handsome profit on ore left in sight in the old workings, but no assay records could be found to confirm these assurances, and even the records of bullion shipments had been destroyed. If surveys and maps were made as the work progressed, no trace of them could be found, and therefore opening of the ground through a new shaft and drifts therefrom would be attended by some risk while exploring near the old workings. Fatal accidents by flooding under these conditions have occurred, and as an evidence that miners have fears of such dangers, it was urged upon the Mining Committee during a recent session of the Montana Legislature, by a delegation of

Jan 1, 1915

By F. D. Wright

Production of a coal preparation plant is governed by many restrictions, such as the tonnage of different products and blends that can be sold within a given period, capacities and output proportions of the cleaning and sizing units, blending proportions, quality specifications, and costs and prices for the various products. Determination of the tonnage of each product and blend that should be made in order to obtain the maximum profit can be difficult unless a systematic method such as linear programming is used. In this paper the basic method of linear programming is described briefly. The Old Ben No. 9 preparation plant is used as an example to illustrate in detail how eqwations can be written to form a linear programming model of a coal preparation plant. Three sample problems, each requiring 56 or more equations and 63 structural variables, were solved with an IBM 650 computer. Linear programming is one of several mathematical tools used for operations research. It has been applied to many fields and has been used by a number of industries either to maximize the profits of certain operations or to minimize costs. P. B. Nalle and L. W. weeks&apos; have described the use of the method by the Riverside Cement Co. to minimize the cost of blending raw materials to make portland cement. Their problem is to obtain at minimum cost a mix with certain specifications from a number of possible materials which have various costs and various amounts of CaO, SiO2, Fe2O3, and other constituents. In a paper on the use of linear programming by the National Coal Board in England, K. B. Williams and K. B. Halley2 describe how the transportation method, a variation of linear programming, is used to minimize the cost of sending 37 grades of coal from 28 mines to seven central washing plants which produce coal for furnace coke and foundry coke. The various coals have different percentages of volatile matter, moisture, sulfur, ash, and phosphorous, so there is considerable choice in how they can be blended to meet the specifications of the two products. The purpose of this paper is to show how linear programming can be used to maximize the profits of a coal washing plant which produces individual final products as well as blends. The Old Ben Corp. furnished assumed sample data from their Old Ben Mine No. 9 preparation plant for this investigation. However, the data that have been used are entirely the author&apos;s responsibility. METHOD OF LINEAR PROGRAMMING Numerous articles and books have been written on the theory and applications of linear programming.3-5 However, since the method has not been widely applied by the mining industry, a brief, nontheo-retical discussion of its basic method seems to be in order. Linear programming (Table I) is used to determine the best possible solution to a number of interdependent activities. It is essentially a method for making systematic selections from a number of possible solutions to determine positively the optimum solution. There may be other equally good solutions but no better ones. Each activity must have linear coefficients and there must be a criterion to judge how good the solution actually is. Linear programming is different from the solution

Jan 1, 1961