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By H. C. LIVINGSTON

At the Hanna No. 4-A mine of The Union Pacific Coal Co. a new system of trackless mining is being utilized to extract a 26-ft coal seam. By using shuttle cars and a conveyor belt for haulage in the rooms and panel entries instead of pit cars and panel hoist a saving of 12 cents per ton is expected. Mining is conducted in a 26-ft coal seam laid down on a synclinal structure with active workings on a pitch of approximately ten to twelve degrees. The coal seam is interbedded between a shale bottom and sand- stone top. The coal is friable, high in moisture, and subject to spontaneous combustion. The mine is rated gassy by the State Coal Mine Inspection Department. Mining is conducted at the present time by unbalanced rope haulage an main slopes spaced on approximate 4300-ft centers with the three-entry system driven to boundary lines, strike entries being turned on approximate 1300-ft centers. Panels are driven to the rise between entries at approximately 750-ft intervals with panel rooms driven on the strike 500 to 600 ft long, leaving 150 ft of barrier pillar between each block of panel rooms.

Jan 1, 1949

By J. W. Snavely

THE high tension belt conveyor is introducing a new and tremendously expanded era of low cost bulk material handling. High tension belt conveyors are generally those installations involving very long centers, high lifts, or drops, in which the belts are stressed up to their maximum tension values, and further, where the belt construction provides tension capacity far beyond what is possible with conventional belt constructions. With these high tension installations, the magnitude of the forces involved demands careful refinement of accepted design practice in order to achieve optimum balance of all factors. No attempt will be made to evaluate the relative merits of belt conveyor haulage with other means of transportation. For present purposes, it is assumed this has already been done in favor of belt conveyor. Neither will any attempt be made to evaluate the various conveyor belt constructions now available or to balance the advantages of various types of mechanical equipment. It is also assumed that the basic haulage information on which the conveyor design is based is accurate and complete. A sustained maximum, uniform load on the belt at all times must be achieved through proper feed control and the use of adequate surge storage to level the peaks and valleys of any varying demand for the material being handled. General Belt Capacity Considerations The belt conveyor capacity tables published by various belting and conveyor equipment manufacturers vary to a considerable degree, and the ratings given are quite conservative. Of necessity, these published ratings are based on the handling of average materials under average conditions. In applying a high tension belt, all possible capacity from the belt must be obtained in order to hold its width to a minimum and thereby limit the initial cost. Two factors are involved, loading to maximum cross section area and traveling at a maximum practical speed. Belt Loading: Proper treatment of the loading of the belt will result in maximum cross section to the load, and published capacity ratings can be exceeded, sometimes by appreciable margins. On the 10-mile conveyor haul used in the construction of Shasta Dam, California, although the rated capacity of the belt line was 1100 tons per hr, at times the system handled peak loads of 1400 tons per hr, almost 25 pct better than the rated capacity. One of the large coal companies has been able to exceed rated capacity by as much as 50 pct. Loading conditions which must be controlled are: 1. Large lumps must be scalped off and rejected or the load must be primary crushed before being placed on the belt. 2. The material weight per cubic foot must be accurate, must be known for all the materials being handled, and must be known for the complete range of conditions of the individual material being handled. Long centers and high lifts magnify small differences into serious proportions. 3. Uniform feeding to the belt is most important. Various types of feeders are available, which can be used to place a constant predetermined volume of material on the belt, or, where an appreciable range of material weight exists, through electrical control actuated by current demand, to place a predetermined uniform tonnage on the belt. One long slope belt in a coal mine in Pennsylvania is being fed at three separate stations with the controls so arranged that whenever the maximum load is going onto the belt from the first station, the other two stations automatically cut out. Whenever the load from the first station drops back, the other two stations again automatically cut in. 4. Careful design of the chutes and skirts is necessary to get the load centered on the belt with a minimum of free margin along each edge. Some free margin at the edge of the belt is necessary to prevent spillage, but if the load can be kept accurately centered, this free margin area can be reduced, and more material can be carried on the belt. What can be accomplished in this respect will vary widely, depending on the nature of the material being hauled. The chute and skirt design must also protect the belt. 5. The design of chutes and skirts should also get the load traveling in the same direction and close to belt speed, so that the load comes to rest on the belt as quickly as possible. The design of the chutes and skirts is worthy of careful study, and after a system is put into operation it should be experimented with to get the best results. Belt Speed: High belt speeds should be used in high tension work. Obviously, high belt speeds enable haulage on a narrower belt, reducing initial cost. The major portion of belt wear takes place at the loading point and around the terminal pulleys. The

Jan 1, 1952

By T. A. Wilson, S. L. Hoyt

The plastic deformation of slender single crystals of zinc has been described in some detail in the paper by Mark, Polanyi and Schmid,' which has become a classic, and also by one of the present authors in a somewhat shorter account. 2 The study of single-crystal zinc is termed classical because zinc single crystals offer, perhaps, the best material yet available for the study of atomic behavior during deformation and the effect known as "strengthening" in metals. A considerable amount of additional work has also been done on single-crystal zinc, but as it is not closely related to the present paper it will not be considered. Throughout all the former work, the mechanism of plastic deformation first described by Mark, Polanyi and Schmid has been assumed to hold. This may be said to offer the strongest confirmation of its correctness. Even so, the picture of the process has never been as completely portrayed as is desirable. The first object of the present paper is to describe work that has been done in this field, and which is even yet being carried on, in the hope that a more complete picture may be obtained. Mathewson and Phillips3 have recently described a new mechanism of the deformation of zinc based on their study of large rectangular crystals. One of their conclusions was that deformation produced twinning with a rotation of some of the basal planes into positions 94" removed from their original position; a position almost the same as that of the prismatic planes before twinning. A second conclusion was that fracture occurred along these basal planes in their new position, and, therefore that fractures previously regarded as prismatic were in reality basal. Such findings are of great significance and they raise a question as to the generality of such behavior. Professor Mathewson's opinion is that even the slender cylindrical single crystals behave in the same manner as his large rectangular crystals when strained by simple tension.

By L. Adler

A relatively simple and effective technique is proposed to deal with the failure of geologic masses containing weakness planes. This technique, termed irextended" rupture envelope, provides a means to clearly distinguish rock and soil from fractured rock and, on a theoretical level, considers a matrix-inclusion system. It may also constitute the link between Mohr's and Griffith's failure theories. Included in the article are five sample problems concerning site location, structural design, strengthening the plane of weakness, changing the magnitudes of major and minor principal stresses and changing the orientations of major and minor principal stresses. Engineers trying to solve design problems in rock and soil mechanics have often assumed an iso-tropic and homogeneous medium. For naturally occurring geologic masses this assumption has always been viewed with regret. The following analysis which deals with the effects of plane anisotropy on failure presents a solution to this. The planes of weakness are joints, faults, bedding planes, fracture and cleavage (natural and induced), foliation and schistosity. The physical properties of these weakness planes include an undulating surface, frictional resistance, discontinuous extent, filling material, tightness and presence of water to cause a hydrostatic pore pressure. All of these properties relating to failure can be summarized in Mohr's rupture envelope for the plane of weakness. This, along with the geometrical orientation, strike and dip, of the plane of weakness produces what is termed an irextended" rupture envelope. MOHR'S STRESS CIRCLE AND RUPTURE ENVELOPE The significant features of these concepts are listed below.' 1) A point on the u - r coordinate plane represents the normal and tangential stress components on a reference area in the material. This area can have any orientation. (Fig. la)

Jan 1, 1963

By E. Furubayashi, T. Taoka, S. Takeuchi

Recrystallization textures developed from artificial nucleation around indentations were compared with spontaneously recrystallized textures in two rolled 3 pet Si-Fe single crystals with (111)[112] and (100) [011] orientations. Orientation of individual grains in some stages of their growth was also directly determined by a microetch-pit method. In both the crystals, the recrystallization texture was characteristic of each orientation regardless of any nucleation conditions, artificial or spontaneous, though artificially nucleated grains were more randomly oriented in finer stage. These results support the concept that the process of selection of growing grains controls the formation of the prejerred recrystallization texture. Discussion is given on the factors controlling the mobility of grain boundaries. Recrystallization textures are formed through a number of stages which are customarily called by the terms recovery, nucleation, and grain growth. Many experiments have been done to clarify the mech- anism of formation of recrystallization texture but no fully successful explanation has been proposed. The texture consists of oriented grains which nucleate at many sites of the deformed matrix and grow at the expense of the matrix during annealing. The current theories on the formation of recrystallization texture are based on the following two extreme hypotheses: 1) the oriented nucleation theory by Burgers et al.;1, 2 2) the oriented growth theory by Beck et al.3-5

Jan 1, 1968

By Albert E. Wood, Edgar R Shepard

The interest of the Federal Government in improvement of waterways dates from 1820, when Congress appropriated $5000 for making a survey of the Mississippi and Ohio Rivers and assigned this work to the Corps of Engineers of the Army. Since that time the Government has gradually assumed increasing jurisdiction in the matter of improvement and control of inland waterways until, by the River and Harbor Act of Jan. 21, 1927, Congress assigned to the Secretary of War and to the Chief of Engineers the duly of making surveys, in accordance with House Document No. 308, 69th Congress, to formulate plans for the most effective improvement of the navigable streams of the United States and their tributaries, for navigation, development of water power, control of floods, and the needs of irrigation. Virtually all the preliminary investigations and surveys required by this act have been completed. The reports made to Congress have been published and often are referred to as ''308 Reports." The map shown in Fig. 1 is merely a skeleton distribution of the projects covered by these reports, but it serves to indicate the magnitude of the proposed undertaking. In many instances, a single character on the map stands for a major development involving several dams and reservoirs or many miles of canals or levees. The devastating floods of 1936, and the need for worthy public works to take up the slack in employment, gave further impetus to this program and in 1936 led to the enactment of a bill authorizing a large number of these projects. The National Flood Control Act of 1936 specifically authorizes some 270 flood-control projects in 31 states, and affecting nearly every state in the Union, with an estimated construction cost of about $300,000,000. In addition, the 1936 Act directs the Secretary of War to make preliminary examinations and surveys for flood control in some 230 additional localities, and to continue surveys and studies of 18 reservoir sites. The Corps of Engineers is proceeding rapidly with foundation investiga-

Jan 1, 1940

By Albert E. Wood, Edgar R. Shepard

The interest of the Federal Government in improvement of waterways dates from 1820, when Congress appropriated $5000 for making a survey of the Mississippi and Ohio Rivers and assigned this work to the Corps of Engineers of the Army. Since that time the Government has gradually assumed increasing jurisdiction in the matter of improvement and control of inland waterways until, by the River and Harbor Act of Jan. 21, 1927, Congress assigned to the Secretary of War and to the Chief of Engineers the duly of making surveys, in accordance with House Document No. 308, 69th Congress, to formulate plans for the most effective improvement of the navigable streams of the United States and their tributaries, for navigation, development of water power, control of floods, and the needs of irrigation. Virtually all the preliminary investigations and surveys required by this act have been completed. The reports made to Congress have been published and often are referred to as ''308 Reports." The map shown in Fig. 1 is merely a skeleton distribution of the projects covered by these reports, but it serves to indicate the magnitude of the proposed undertaking. In many instances, a single character on the map stands for a major development involving several dams and reservoirs or many miles of canals or levees. The devastating floods of 1936, and the need for worthy public works to take up the slack in employment, gave further impetus to this program and in 1936 led to the enactment of a bill authorizing a large number of these projects. The National Flood Control Act of 1936 specifically authorizes some 270 flood-control projects in 31 states, and affecting nearly every state in the Union, with an estimated construction cost of about $300,000,000. In addition, the 1936 Act directs the Secretary of War to make preliminary examinations and surveys for flood control in some 230 additional localities, and to continue surveys and studies of 18 reservoir sites. The Corps of Engineers is proceeding rapidly with foundation investiga-

Jan 1, 1940

By Gilbert Soler

Producers of alloy steels recognize the importance of chemical composition in relation to the hot-working properties and the typical surface defects found in their product. Each analysis of steel has its own peculiar characteristics. Under conditions of standard mill practice each analysis is susceptible to certain types of defects. Mill practice must be varied to obtain the best combination of surface and internal quality in the product. Chemical composition influences the cast structure and crystallization characteristics of the ingot. It also determines the rate of heating and cooling, the plastic hot-working range, and the phase structure of the steel at various temperatures. as well as the tendency toward scale formation and decarburization. This paper endeavors to emphasize the manner in which chemical composition affects the various properties of steel, and to indicate the relative importance of these factors in relation to the hot-working properties and surface characteristics of killed steel. The influence of chemical composition may be outlined as follows: I. Effect on the cast structure of steel, including: A. State of deoxidation, and type of inclusions. B. Gas content of steel. C. Freezing point and melting point of steel. D. Crystallization characteristics and segregation. 11. Effect on the hot-working properties and surface characteristics of steel, including: A. Plastic hot-working range. B. Phase structures at hot-working temperatures. C. Rate of heating. D. Cooling characteristics. E. Scale formation. F. Surface decarburization. EFferect of Chemical Composition on Cast Structure of Steel State of Deoxidation and Type of Inclu-sions.—The state of deoxidation is limited by the final chemical analysis desired in the finished product, and is controlled primarily by carbon, manganese, silicon, and aluminum, and to a lesser degree by chromium, titanium, vanadium, or other deoxidizing elements. The degree of deoxidation affects the density of the cast structure and broadly classifies the steel as killed, semikilled, or rimming. This in turn manifests itself in surface characteristics. The manner and extent of deoxidation also controls the amount, type, and distribution of nonmetallic inclusions formed. The equilibrium of manganese, silicon and aluminum with the slags and pouring refractories with which the metal comes in contact is important, especially in regard to inclusions of fire-clay origin. Some surface Seams and hot-working difficulties can be traced to nonmetallic inclusions.

Jan 1, 1941

By Gilbert Soler

Producers of alloy steels recognize the importance of chemical composition in relation to the hot-working properties and the typical surface defects found in their product. Each analysis of steel has its own peculiar characteristics. Under conditions of standard mill practice each analysis is susceptible to certain types of defects. Mill practice must be varied to obtain the best combination of surface and internal quality in the product. Chemical composition influences the cast structure and crystallization characteristics of the ingot. It also determines the rate of heating and cooling, the plastic hot-working range, and the phase structure of the steel at various temperatures. as well as the tendency toward scale formation and decarburization. This paper endeavors to emphasize the manner in which chemical composition affects the various properties of steel, and to indicate the relative importance of these factors in relation to the hot-working properties and surface characteristics of killed steel. The influence of chemical composition may be outlined as follows: I. Effect on the cast structure of steel, including: A. State of deoxidation, and type of inclusions. B. Gas content of steel. C. Freezing point and melting point of steel. D. Crystallization characteristics and segregation. 11. Effect on the hot-working properties and surface characteristics of steel, including: A. Plastic hot-working range. B. Phase structures at hot-working temperatures. C. Rate of heating. D. Cooling characteristics. E. Scale formation. F. Surface decarburization. EFferect of Chemical Composition on Cast Structure of Steel State of Deoxidation and Type of Inclu-sions.—The state of deoxidation is limited by the final chemical analysis desired in the finished product, and is controlled primarily by carbon, manganese, silicon, and aluminum, and to a lesser degree by chromium, titanium, vanadium, or other deoxidizing elements. The degree of deoxidation affects the density of the cast structure and broadly classifies the steel as killed, semikilled, or rimming. This in turn manifests itself in surface characteristics. The manner and extent of deoxidation also controls the amount, type, and distribution of nonmetallic inclusions formed. The equilibrium of manganese, silicon and aluminum with the slags and pouring refractories with which the metal comes in contact is important, especially in regard to inclusions of fire-clay origin. Some surface Seams and hot-working difficulties can be traced to nonmetallic inclusions.

Jan 1, 1941

By L. D. Clark

Pay-out, the ratio of capital expenditure to annual cash return can be very revealing when employed to gage the merits of a proposed mining venture. It is a quantity, numerically but not physically equal to a factor, by which cash return may be discounted to equal required investment. The fewer the pay-out years, the greater the average annual earning power of the project. Considerable material has been written in the past about the most important and difficult problem mining management faces in evaluation of a property: the optimum production rate for the venture. What daily capacity should be adopted for the proposed operation that it may be the most rewarding to those underwriting it? H.C. Hoover has said, "The most important objective is the least cost per ton mined; and minimum working costs can only be gained by the most intensive production." Theoretically and practically, the quicker the ore is removed, the more profitable should be the venture because of the saving in fixed charges, the consequent lower unit costs and the interest unearned by the profit from the unmined ore. Yet, such performance will be tempered by policy and a restraint imposed by the ratio of capital expenditure to annual cash return. * The 'Annual net profit after taxes but including depreciation and depletion allowances. former will be based upon an analysis of the economic climate anticipated, with its many ramifications including the demand for the product, prices, tax laws, the conduct of labor and related wage scales. The variables and intangibles involved in estimating the optimum production rate for a mine do not readily lend themselves to mathematical relationships or equations and the problem can become complex indeed. The more readily applicable and relatively faster appraisal method will be used which, in addition to being reasonably adequate in most cases, will serve as a guide, should a more expanded and detailed estimate be desired. The first question is what is company policy with respect to the rate of investment return? This will depend on that significant period of time referred to as the pay-out, which can be defined as the estimated interval during which capital investment is returned through application of annual cash return to its recovery. Expressed another way, it is the ratio of capital expenditure to the annual cash return. For example, if the capital investment is $C and the annual cash return is $A (after Federal tax), then $C/$A = the pay-out period in years. That is to say, if $C = $1,500,000 and $A = $214,000, then which is the mathematical expression for the period of time it takes to recover the funds originally invested in a mining enterprise. The relationship yp = $C/$A can be useful — an expression which requires only the significant tern yp to be fixed; in other words, the long range investment policy. For what is the pay-out period but an expression of that policy in terms of the speed, within practical limits, with which an individual or company may want to recover capital expenditure? A policy by which pay-out will be fixed is imperative. This ratio must lie within relatively narrow limits governed by what is economically feasible. It cannot be too low, rendering the ratio impractical or absurd, nor too great, delaying the return of capital for reinvestment beyond a commensurate interval. What pay-out will govern this policy? Federal corporate taxes would seem to present the best measure. Consider mining in Canada where new mines are exempt from Federal income tax for 3½ yr from date of first production. This exemption expressly allows The Act states: "A corporation . . . i s not required to include the profits . . . for the period of 36 months commencing with the day on which the mine came into production in reasonable commercial quantites." a company to recover capital expenditure during the early stages of production. With such an incentive, it is logical to strive for as much capital redemption as possible during this period. Thus, 3½ yr would be a major contribution to the pay-out in Canada. Furthermore, it generally takes from 1½ to 3 yr to develop

Jan 1, 1963

By H. W. Schreiber, G. R. Castle

INTRODUCTION The small mining company faces the dilemma of how to finance the development of its properties. Many of these small companies don't have the financial resources to pay for development costs from their own funds and frequently they do not even have the financial strength to permit them to borrow the money needed for development. A project financing can sometimes be arranged in such a way as to solve this dilemma. A typical project financing will not provide the answer to the "little guy's" problem because most project financings require that the sponsors of the project provide completion undertakings and sometimes other undertakings. These undertakings are often a prerequisite to obtaining financing, and if the sponsor is not financially strong enough to provide the comfort that the lenders require, then the sponsor will have difficulty obtaining financing no matter what undertakings are offered. However, with a little imagination and the right set of circumstances, a project financing can sometimes provide the solution to the small mining company's problem. The Strathcona Sound Project is unusually suited as a case study because the sponsor, Mineral Resources International Limited,(MRI) was able to arrange a project financing for the development of the project even though the lenders probably would not have been willing to loan a similar amount of money direct to MRI based on the full faith and credit of MRI's balance sheet. The way that MRI was able to arrange this financing makes for an interesting story. THE CASE In early 1974, MRI owned 100% of a small to medium sized zinc - lead - silver massive sulfide deposit (Property) located 475 miles north of the Arctic Circle less than two miles from deep water on Strathcona Sound which is a shipping zone in the Canadian Arctic. The Property was situated at a desolate location except for an Eskimo settlement (Arctic Bay) which was about 20 miles west of the Property. In other words, the project required that complete infrastructure would need to be installed in this far northern location. Independent reserve and feasibility studies (Study) had been completed on the Property which confirmed a total of 6,825,000 tons of reserves classified and summarized as shown below on Table I: [ ] These reserves were based on 229 diamond drill holes totalling 58,909 feet and were established on a cut-off grade of 7% zinc and a minimum mining height of seven feet. The overall mining recovery rate was estimated at not less than 85% and not more than 90%. The feasibility study indicated that it would cost an estimated $45,044,000 to develop an underground mine, a concentrator, a town-site, a power plant, storage facility, loading dock, a tailings disposal area and an airstrip on the Property with an annual capacity of 525,000 tons of ore per year. The construction period was expected to take two years and projected capital costs were broken down as set forth below on Table II:

Jan 1, 1985

By George H. Eldridge

The existence of phosphate of lime within the State of Florida has been known for over a decade; but until the spring of 1887, the extent and value of its deposit.;, possibly with one exception, were unsuspected. In that year Col. T. S. Moorehead, induced by a statement made by Mr. J. F. Le Baron, examined the gravels of the Peace river, recognized the importance of the deposits, acquired such tracts as were regarded as desirable, and established the pebble-phosphate industry, making his first shipment in May, 1888, to the Scott Manufacturing Company, of Atlanta, Ga. The establishment of the pebble-phosphate industry upon Peace river was followed, a year later, by the discovery in Marion county of an entirely different class of phosphate, now commonly known as hard-rock phosphate. This discovery was made early in June, 1889, by Mr. Albertus Voght, in a well which he was sinking upon his place near the site of the present town of Donnellon, about 20 miles southwest of Ocala. To it, more than to any other cause, is due the rapid and remarkable development of the present great industry of the State. It was, however, Mr. John F. Dunn, of Ocala, who turned to advantage the accidental discovery of Mr. Voght. After acquiring a knowledge as to the chemical composition and value of the material, Mr. Dunn and hid associates purchased several thousand acres of land and organized the Dunnellon Phosphate Company for active operations. From Dunnellon as a center, prospecting rapidly extended in all directions, until at the present day important mines have been opened over a well-defined tract more than 200 miles long and about 6 miles wide. This tract lies par-

Jan 1, 1893

By H. W. Mead, C. E. Birchenall

SELF-DIFFUSION of iron in austenite is a process which may play a significant role in some of the practically important reactions which occur in solid irons and steels. It also provides a system in which the interaction of vacancies on substitutional sites and atoms in interstitial positions may be investigated. For both purposes, accurate values of the diffusivities are required. Two sets of previous measurements exist, each containing features which require checking. In the course of an investigation to determine the rate of diffusion of iron in certain steels, Garwick and Rosenqvist' measured the self-diffusion coefficient of iron in a 0.10 pct* C steel and obtained a dicated that while at lower temperatures D increased with increasing carbon content, at the higher temperatures it first increased and then decreased. At the same time the activation energy decreased linearly from a value of 69,000 cal per g-atom for pure iron to 33,000 cal per g-atom at 1.06 pct C. This rapid decrease in activation energy implies that iron at higher temperatures within the austenite range would diffuse more slowly in high carbon steels than in steels of lower carbon content. Experimental Procedure The radioactive iron used in this work was obtained from Oak Ridge National Laboratory. The unit consisted of about 1 microcurie each of Fe7 and Fe It was allowed to decay for two years. At the end of this time most of the Fe with a half-life of 46.3 days, had decayed, while most of the original Fe(half-life 2.91 years) still remained. The iron as chloride was extracted into an ether layer, using the method of Ashley and M~rray. After evaporation of the ether the iron chloride was dissolved in 250 ml of aqueous solution containing 2.4 gpl Fe. The compositions of the steels used are listed in Table I. Disks of ¾ in. diam and about ¼ in. thick were machined from these steels for use in diffusion couples. The disks were surface ground on both sides to ensure parallel opposite faces. One face of each disk was polished through 000 emery paper. Half of the prepared disks were plated with radioactive iron. For this, 1 ml of the radioactive iron

Jan 1, 1957

By C. E. Silverblatt, D. A. Dahlstrom

Previous bench-scale studies demonstrated that a substantial moisture reduction can be obtained by the application of steam to coal filter-cakes, particularly to those containing a limited amount of minus 200-mesh material. Consequently, U.S. Steel's Applied Research Laboratory conducted a study to determine the feasibility of steam filtration of 1/4 in. by 0 coal on a continuous pilot-scale installation in which an Eimco extractor is used. The test results showed that the moisture content of this coal could be reduced to 5.5% at a steam loading of about 175 lb of steam per ton of dry cake. In terms of steam consumption, this loading is calculated to be 1-1/2 lb of steam per lb of water removed. In some tests, only 1 lb of steam per lb of water removed was required. These levels of steam consumption are significantly less than the actual heat requirements of conventional thermal dryers. The satisfactory moisture reductions were obtained at filtration rates of 125 to 186 lb of dry solids per sq ft per hour. However, the proper design of commercial filters should improve the potential rates that can be attained. These results indicate that steam filtration has considerable economic potential for drying 1/4 in. by 0 coals and also has additional advantages over the conventional thermal drying of coal. The results of the previous bench-scale studies and those published by Burton' demonstrated that a substantial moisture-content reduction can be effected by the application of slightly superheated steam to coal filter-cakes, particularly to those containing a limited amount of minus 200-mesh material. Consequently, US Steel's Applied Research Laboratory conducted a study to determine the feasibility of steam filtration of 1/4 in. by 0 coal on a continuous basis. In the continuous process, the dewatering operation on the filter is conducted in stages. In the first, the bulk of the water in the feed slurry is removed by conventional mechanical dewatering on a portion of the filter before the steam is applied. In the second stage, steam is applied to the cake. The steam condenses and releases its latent heat, thereby reducing the viscosity of the remaining cake water; this reduced viscosity then facilitates further drainage and produces a cake of lower moisture content. Because of the availability of feed coal on a continuous basis and since steam was readily available from a low-pressure boiler, the Applied Research Laboratory selected for the test site a coal-preparation plant that cleans Pittsburgh Seam coal. A slurry of table and flotation coal in percentages as they occur normally was used as feed stock. Typical analyses of this slurry are shown in Table I. DESCRIPTION OF FILTER AND EXPERIMENTAL PROCEDURES An Eimco Extractor was selected for the evaluation of steam filtration in a continuous process. This unit was chosen because of its availability and its design features that permit relatively simple hood construction, instrumentation, and operation. A photograph of the Extractor is shown in Fig. 1. In the filter a cloth medium is used that travels horizontally and continuously with a grooved, rubber drainage belt. The total effective filter area was 12.5 sq ft. As the feed slurry flows by gravity from the feed box onto the medium,

Jan 1, 1964

By P. K. Chatterjee

The overall success of many strip coal mining operations depends primarily upon the efficient use of draglines to remove overburden. These machines require enormous capital investment and unless used efficiently the profitability of a venture is adversely affected. It is important that the dragline works continuously and it is imperative that the walking path and other facets of its operation be predetermined exactly so that the desired production rate is achieved with a minimum of non-productive time. Details of dragline operations which are of particular interest are walking path, prediction of best cut and positioning to maximize production, the angle of swing which produces the swiftest operation, optimum fill factor allowable for the type of material and conditions of ground, the maximum depth from which it can excavate and operating level with respect to the elevation of the high wall. The aims of the present paper are: 1. To establish a cut-off point in the cost-depth ratio. 2. Predict the most economic method of stripping in a given area using graphical plots of walking path implemented with information necessary to ensure optimum production. The optimum operating efficiency of the dragline in relation to the terrain and other conditions imposed on its operation will be evaluated. The model is based upon operating data which has been collected from site observations of a large strip coal mining operation in Central Queensland, Australia.

Jan 1, 1977

By Robert W. Thompson, Darry A. Ferguson

In August, 1977 the United States Congress passed Public Law 95-87 which has been commonly referred to as the Surface Mining Control and Reclamation Act (or SMCRA). This title is somewhat misleading in that the act creates as many regulatory requirements for underground coal mines as for surface coal mines. How- ever, this paper will concentrate on the effects of SMCRA on designs and stability for various activities of surface coal mines, specifically those concerning "Disposal of Excess Spoil". In the past, the objective of most laws and regulations applicable to the mining industry has been to achieve goals of safety or environmental concerns for all types of mining. However, SMCRA is unique in that it sought to regulate-all-activities of coal mining from initial data gathering, exploration, mine design and facilities design to reclamation activities and design. More specific to the stability of the activities of surface coal mining, special criteria for design and construction performance standards have been promulgated for the construction and maintenance of roads, dams and embankments, coal processing waste, ex- cess spoil piles, backfilled reclamation and pit slides. The criteria for design for the previously mentioned facilities has been enumerated by regulations and in many ways restrict the use of site specific design parameters. The restrictions imposed by regulations significantly inhibit the engineer's ability to develop the best practical and economical design and in some cases may re-

Jan 1, 1983

By Robert R. Turner, Arthur R. MacPherson

This chapter reviews the steps which should be taken from the time it is decided to consider autogenous grinding in the development of a new ore deposit or the expansion of an existing plant up until the purchase of the new autogenous mills. In this case the term autogenous includes semi -autogenous, secondary pebble mills, and lump milling as well as fully autogenous grinding systems. Also, both wet and dry grinding alternatives have been included. Before the test program it must be decided how many bulk samples are required to properly assess the autogenous grinding possibilities of the deposit. Also, a decision must be made on where and how the samples are to be ground i.e. pilot mill at site or in established location, wet and or dry grinding, etc. In the test program itself, certain fundamental data must be obtained. The testing should include enough work to determine whether fully autogenous or semi-autogenous grinding should be used and what type produces best power efficiency. Also, all the other pertinent data should be collected such as power; tonnages; feed, charge, and product sizing; circulating loads, etc. If a secondary mill is required to produce a final grind the decision on whether a pebble or ball mill should be used may require additional test work. Finally, the concentration of the mineral may play an important part in selection of the circuit and should become a part of the final testing once the grinding has been established.

Jan 1, 1978

By A. J. Opinsky

ThE superior performance of nonsag tungsten wire in lamps has been ascribed to the large-grained micro-structure that can be developed in it. The orientations of these large grains have been studied several times; most published data1-' appear to be similar to those plotted in Fig. 1. These new data were obtained by X-ray back-reflection Laue technique from all of the large grains occurring in thirteen different wires that had been heated at the lowest possible temperature for the formation of large grains. Here the wire axis is plotted in terms of the principal directions of the cube. Rosi decided that the preferred orientation of the large crystals could be described by a single ideal orientation, (531), being parallel to the wire axis.' Rieck2,3 and Mannerkoski' have essentially confirmed this finding. Opinsky, Orehotsky, and Seigle argued that the data suggest that (211) is parallel to the wire axis instead of a single ideal orientation.5 This {211} contains the (531) ideal orientation and would appear to be a more general case. Ahlborn and Wassermann report that their orientation data stretch from ( 110) through (531) to (311) 8 This is part of the locus of (211). All these investigators have determined the orientations of the large grains by back-reflection Laue techniques. They have all obtained essentially similar results. On the other hand, Swalin and Geisler, who obtained their data by neutron diffraction, indicated that the preferred orientation of the large grains in doped wire is (110) .7 These findings cannot presently be reconciled with the pole density data described in the previous paragraph. Rosi1 and Rieck2 have advanced arguments about how their orientations could occur. Nevertheless, the crystallographic link between the (110) (cold-worked) fiber texture and the preferred orientation of the large grains has remained missing. This link can be provided through the concept of coincidence-type boundaries. Such boundaries separate two grains that have a certain number of common lattice sites. Coincidence relationships that result from rotations about low index directions are given by Brandon et a1 .' What is desired is a calculation of those orientations that bear a coincidence relationship with the (110) fibers of the cold-worked matrix. This situation arises in the following fashion. Heating the tungsten wire for a combination of time and temperature falling short of the formation of the nonsag structure yields a structure that is still fibrous in nature and the preferred orientation remains (110). During grain growth, the growing grain is in contact with these fibers. It is hence possible that the entire process may begin by the passage of a coincidence boundary into a (110) fiber. The calculations were carried out analytically and checked graphically. Following Brandon et a1.,8 coincidence relationships from 1 in 5 to 1 in 19 have been considered. The results of the calculations are given in Fig. 2. Of the coincidences examined, some of those occurring upon rotation about ( 110) come closest to the experimental points in Fig. 1. Nineteen of the twenty-three data points in Fig. 1 can be attributed to the ideal orientations A, B, C, and D in Fig. 2. As determined analytically, three crystals lie within 4 deg of point A, four lie within 21/2 deg of point B, eleven lie within 5 deg of point C, and one lies within 1 deg of point D-a total of nineteen. The off-lying points are near the |110| point of the triangle.

Jan 1, 1968

By NEWTON B. KNOX

THE war has forced the principal industrial nations of the' world into the strait jacket of a closely controlled economy; taxes have been heaped upon all enterprises in order to maintain the armed forces and to deprive the people of the ability to bid for goods now unavailable. These restrictions, controls, and taxes are unlikely to disappear entirely after the war has been won, for debts will remain to be paid with a long period of difficult readjustment. Although the new economy will doubtless offer plentiful opportunities for the advantageous use of capital, no investor can ignore the favorable conditions offered by industry in Latin America, where taxes are relatively low and the restrictions on free enterprise comparatively mild. In mining in South America, the great international corporations have

Jan 1, 1944

By V. J. Sikora, T. S. Hutchinson

This paper presents a method for making a water-rlrive ana1gsis without prior knowledge of aquifer geometry and uniformity using a standard desk calculator. Although it is necessary to know the initial oil in place to use this method, this is a minor limitation to the scope of (he method since in most reservoirs it is possible to obtain reasonably accurate volumetric oil-in-place estimates. An equation is developed which relates pressure at the water-oil contact to the water influx rate as a function of time by a factor called the resistance function. The resistance function introduces the composite effect of the aquifer geometry and flow resistance disrribution. It is pointed out that the characteristic shape of this function makes it possible to start with on approximation of the function and successively improve the approximation until the correct resistance function curve is obtained. In this fashion water-drive estimates can be made without the limitation of assuming simplifed aquifer shapes and flow distributions. This is the novel feature of this development. Methods are given for extrapolating the final curve to calculate future aquifer behavior. Equations are developed for adjusting the pressures and water influx rates where it appears that possible errors in these quantities make it difficult or impossible to obtain a useuble resistance function curve without this adjustment. Application of the pressure build-up analysis techiiique to estimate. some of the aquifer properties is also presented INTRODUCTION A great many oil pools are the result of oil accumulation in some type of trap in an otherwise large and continuous porous stratum. The void space of this stratum outside of the oil pool itself is filled with water or brine. In analyzing performance of the oil pool surrounded by this water aquifer, it is quite necessary. in most cases, to include behavior of the water. When the pressure at any point in a fluid system is lowered, such as by opening a well in an oil sand, fluids in the immediate neighborhood of this point will begin flowing towards this lower pressure sink. As pressure in this area drops due to flow towards the sink, fluids from farther out will start to flow towards the lower pressure. As more and more fluid is removed from the system, the distance from the sink or well within which flow is occurring will continually increase; that is, thc region of disturbance will grow. If some rigid boundary such as a fault is reached by the disturbance, this area will cease to grow; but if some movable boundary is reached, such as a water-oil contact, the area will grow on out into the water, although rate of growth may and almost always does change. The relation between amount of pressure drop and amount of fluid flowing at any point and at any time in an aquifer depends on such factors as compressibility and viscosity of the fluids, the porosity and permeability of the rock, geometry of the whole system and withdrawal rate or pressure drop. With these factors known, it is theoretically possible to calculate the pressure-flow behavior of the system, However, in practice true solutions to the problem are next to impossible due to complexity of reservoir systems. A number of approximate methods of solution have been developed based on various simplifying assumptions. One frequent assumption is that the water-oil contact can be located and equations defining oil reservoir and aquifer solved separately by assigning values to various parameters so as to match past pressure and production history. Usually the properties of the aquifer are not known, since few, if any, wells are drilled through the aquifer; but the water influx and the pressure at the reservoir boundary are known over some time. If it can now be assumed that the aquifer is circular, pie-shaped, or linear, and that it has uniform properties, it is possible to fit a theoretical dimensionless curve to the past aquifer performance history and therefore calculate future water drive. These theoretical curves are available in the literature,1,2,3 Of course, the assumption of uniform aquifer properties is almost always somewhat in error. Fortunately, however, moderate variations from the average have little effect on behavior of the system; and, hence, the best fit of a theoretical curve is frequently satisfactory. In other cases variations in aquifer properties and geometry are large enough that none of the available theoretical curves will give an acceptable fit of the data. In these cases, methods of fitting the data with various electrical analyzers have been developed.1,2' It is the purpose of this paper to present an approach