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By G. A. Vissac

The drying of fine coal involves special techniques, which are discussed and analyzed. Types of dryers employing these techniques are described. Calculations are presented for new methods of dealing with the entrained dust that is always present in fine coal drying operations. NEW conditions, new requirements, and new methods have increased the demand for more efficient and more economical methods of drying fine coal. Dewatering of larger sizes may reduce the surface moisture to 8 or 9 pct. It is more difficult, however, to dewater sizes below 1/4 in., and some filter cakes still contain as much as 20 or 25 pct moisture. Increased freight rates and stricter consumer specifications have resulted in a demand for further reductions in moisture content. This can be obtained only by heat drying. Most modern methods of heat drying disperse or spread the mass of coal to be dried, in an atmosphere of dry hot gases. The more intimate the contact between coal particles and hot gases, the quicker and more efficient the drying operation will be. Two different techniques are generally employed, using either a fluidized condition or an entrained condition of the coal to be dried. Fluidized Condition Fluidization of a body of sand was defined and explained by Fraser and Yancey in a paper published in 1926.' This condition was artificially obtained and maintained by proper regulation of the rate of air flowing through the sand body. "The sand bath 'boils' uniformly on the surface," they write, "and feels like a fluid." The fluidization technique was also described and analyzed by Steinmetzer2 in connection with the operation of an air cleaning table. His main conclusions are as follows: "Fluidity is, for the particles involved, the possibility of motion with minimum friction. . . . Then fluidity requires the introduction of various forms of energy capable of neutralising frictions. Two solutions can be used— air and/or mechanical motions (such as the shaking motion of the carrying deck of the air table). The combination of mechanical and air energy will give the widest margins of size ratios and of bed thickness, translated in capacity per unit area of the carrying table." Richardson and Langston3 have indicated results obtained with a dryer working with a fluidized bed. They used a vertical tube type of dryer, however, without the assistance of any mechanical energy, and without any lateral motion of the fluidized bed. The capacity of such a dryer is too limited for practical applications, since the speed of the acceptable air currents is held to the speed of fall of the particles involved. Capacities as low as 182 Ib of coal per hr per sq ft of dryer area are indicated. As stated by Richardson: "A basic limitation to a fluidised bed dryer is that the velocities of the gas must be held within a definite range; with velocities of 10 ft per second, all coal minus 6 mesh in size will be entrained, and the operation is then similar to that of a Flash dryer." A fluidized bed must be virtually static. The coal particles simply kept in suspension offer a minimum resistance to the flow of gases, insuring the most favorable conditions for rapid evaporation of surface moisture. However, very wet fine coal, i.e., over 12 pct of surface moisture, will be delivered in the forms of mud balls, or as a soggy, sticky mass, almost impossible to disperse, sticking and acting as a wet blanket on the deck. Strong currents of gases and wide deck perforations will be required to punch holes in the wet mass and gradually loosen and fluidize it. The mechanics of fluidizing a bed of coal in a gas medium for the purpose of obtaining the most efficient drying condition are entirely similar when the fluid used is water and the purpose is to break up and distend a bed of coal to be cleaned so that perfect stratification according to densities will be insured. Purely mechanical energy is used in the basket-type jig, water pulsations in the piston and in the Baum-type jigs. A combination of mechanical motion and of air pulsation offers the most efficient and favorable conditions. Entrained Condition The most critical factor to be considered in the design of a dryer employing the entrained condition technique is the speed of the hot gases to be circulated in the drying column. With insufficient gas velocity, excessive amounts of the largest sizes will drop to the bottom of the dryer column without being thoroughly dried. On the other hand, high gas velocity will cause degradation, dust losses, and high power consumption. Figs. 1 and 2, reproduced from Hanot,4 show the relative importance of speed and temperature for various sizes of particles. It can be seen, for instance, that to maintain in unstable equilibrium particles of 1/4-in. size in a gas current at 500°C, a speed of 30 meters per sec, or 6000 fpm, will be required. For % -in. particles an almost prohibitive speed of 45 meters per sec, or 9000 fpm, will be necessary. In practice, maximum gas velocities of 3000 fpm are recommended; since power increases as the cube of the velocity, it can be seen that beyond certain limits such dryers would not be economical. If the particles were moving at the same speed as the hot gases they would remain in the same

Jan 1, 1954

By H. J. Wasson

With the close of 1932 and the third year of the depression, the activity of oil production presents, amidst the general wreckage and chaos of industrial society, a somewhat unique picture of rationalized economic effort. How long it will continue to present such a picture, however, is a subject for conflicting surmises. East Texas still dominates the contemporary horizon, but it has become, at least for the time being, a definitely known factor. With its 9500 wells it is approximately 90 per cent drilled up. So long as production control obtains, it is merely one important factor of the national oil reserve. Domestic Production The notable new discoveries in the United States were less numerous than for several years. Elsewhere in the world the record is much the same. The Conroe field in Montgomery County, Texas, lying in an intermediate zone that might be classified either as Gulf Coast or East Texas, represents perhaps the single example of a truly major discovery during the year. Elsewhere in Texas the new pool discoveries, about a dozen or so in number, were nearly all in the region known as Southwest Texas. Oklahoma contributed seven or eight new pools of the routine "run-of-mine" caliber, and the opening up of a few deeper oil pays also were of some significance. Continued expansion of the proved and semiproved reserves in Kansas added an important increment to the oil resources of that state. In California not a single new field was added to the roster, though deeper pay zones equivalent to or of greater importance than many new fields in other parts of the country were discovered or indicated. The new deep zone in the Belridge field is considered by some to underlie the prolific Temblor and may thus forecast the widespread distribution of a potentinl oil horizon underlying many San Joaquin Valley fields below the depths thus far exploited. Aside from the routine operations in connection with settled production, the Eastern fields were decidedly inactive. Further new develop-

Jan 1, 1933

By L. R. Jackson, W. T. Lankford, K. F. Smith

ComMercial steel sheet is prepared by a combination of hot and cold rolling and annealing. This treatment usually results in more or less pronounced anisotropy. The anisotropy may manifest itself both as preferred orientation and in the manner in which impurities, segregations, and the like, are aligned in the sheet. The type of preferred orientation and the organization of impurities or segregations may affect the elastic moduli, the yield strength, the tensile strength, and almost always the amount of ductility in different directions. In any case, the most important directions concerned in the anisotropy are along the rolling direction, along the width direction, and along the thickness direction. Considerable data exist on the anisot-ropy of sheet steel as demonstrated by conventional tensile tests; however, few attempts have been made to measure the constants of plastic anisotropy and use them to describe the flow of anisotropic sheet under combined stresses. In this paper, evidence is presented indicating that plastic flow in anisotropic sheet can be described by the shear-strain energy flow theory provided that the anisotropy is properly taken into account. Materials Used in the Investigation Table I lists the sheet materials used in this investigation and describes the condition in which materials were tested. Direction, of Tests and Test Methods Two types of tests were run—tensile tests and hydraulic-bulge tests. Characteristic parameters of anisotropy were determined from the tension tests by methods which will be described later. In all cases, the tensile test pieces were cut from the same quarter line and adjacent to the bulge test pieces in the sheet in order to minimize

Jan 1, 1949

By W. L. Austin

The only essential difference among the three methods of collecting the precious metals from their low-grade ores by fusion is comprised in the nature of the vehicle in which those metals are concentrated. If lead- or coppper-ores are used, the processes are respectively lead- or copper-smelting; but when the sulphide of iron forms the matrix in which the gold and silver are collected, the process is known as pyritic smelting. The latter method presents rarely any advantages when lead- or copper-ores are available at rates which permit profitable treatment. Pyritic silver-smelting, defined by Percy as " the smelting of silver-ores, which are either free from lead or do not contain it in sufficient quantity to collect the silver, in conjunction with pyrites, in order to produce a regulus in which the silver may be concentrated," is not, as the name would imply, confined to ores of this metal alone, but embraces auriferous silver-ores, or even gold-ores simple. This method of collecting the precious metals from lowgrade dry ores, employed at Freiberg by Barthel Kohler in 1585, does not appear, up to the present, to have been introduced into this country on a working scale. And yet the possibility of getting rid in a single operation of all the earthy or siliceous gangue of a lowgrade ore and concentrating the precious metals in a matte without loss of lead (which includes gold and silver) by slagging, or volatilization, at the same time producing a highly siliceous slag, very nearly if not quite as clean as is usual in lead-smelting, certainly commends itself. In some parts of the country, owing to the com-

Jan 1, 1888

By W. A. Ver Wiebe

UNder the impetus of new demands caused by the defense program, the oil and gas industries of Kansas established new records during the year 1941. In all, 2113 wells were drilled, which compares favorably with the record total drilled in 1937. These 2113 tests resulted in 1446 oil wells, 76 gas wells and 592 dry holes. In all three categories there was an increase over the previous year, but unfortunately the most marked increase was in the dry holes. Nearly 80 per cent of the increase must be allocated to the drilling 01 unsuccessful tests. This was partly because of the increasing difficulty of finding new reserve areas and partly because of the erratic character of the production in the Arbuckle dolomite, which is now the main producing zone. Closer analysis of the totals reveals that western Kansas accounted for 1634 tests, of which 1186 were oil wells, 34 were gas wells and 415 were dry holes. The total potential initial daily production uncovered by the successful wells amounted to 1,691,000 bbl. of oil and 508,000,000 cu. ft. of gas. Both figures indicate a considerable decrease when compared with the proceeding year; in 1940 the respective figures were 2,128,000 bbl. and 1,289,000,000 cu. feet. In eastern Kansas a total of 479 wells were drilled. Among these, 260 were oil wells accounting for a daily initial potential production of 45,662 bbl. The new gas wells numbered 42 and added 290,438,000 cu. ft. per day to the gas potential production of the state. The remaining tests, 177 in number, were dry. It is interesting and significant that almost half (791) of the total wells drilled in western Kansas were drilled by the independent operators. Among the large companies the Cities Service Oil Co. drilled 169 wells; the Stanolind Oil and Gas CO., 101; the Skelly Oil Co., 80; the Continental Oil Co., 99, and the Shell Petroleum Co., 63 wells. In eastern Kansas the independent operators drilled 406 out of the total of 479 wells. Among the major oil companies the Cities Service Oil Co. drilled 38; the Phillips Petroleum Co., 13, and the Sinclair-Prairie Oil Co., II wells. The figures on relative percentages of dry holes to successful oil or gas wells are revealing. In western Kansas approximately one third of all wells drilled by the independent operators were dry holes. The major oil companies drilled approximately 844 wells in western Kansas, of which 678 were successful in finding either oil or gas. It thus appears that the major companies fared much Getter than the independents. In eastern Kansas the major companies drilled 73 wells of which 63 were successful in finding commercial quantities of oil or gas. No less than 286 wildcat tests were put down in western Kansas and 72 in eastern Kansas, or 358 in all, during 1941. Considerably more than half of these were drilled by independent operators; zoo in western and 66 in eastern Kansas. An exploratory hole % mile or more from production is regarded as a wildcat well in Kansas. On a percentage basis, approximately 75 per cent of all wildcat wells were failures; only 25 per cent found oil or gas in western

Jan 1, 1942

By W. A. Ver Wiebe

UNder the impetus of new demands caused by the defense program, the oil and gas industries of Kansas established new records during the year 1941. In all, 2113 wells were drilled, which compares favorably with the record total drilled in 1937. These 2113 tests resulted in 1446 oil wells, 76 gas wells and 592 dry holes. In all three categories there was an increase over the previous year, but unfortunately the most marked increase was in the dry holes. Nearly 80 per cent of the increase must be allocated to the drilling 01 unsuccessful tests. This was partly because of the increasing difficulty of finding new reserve areas and partly because of the erratic character of the production in the Arbuckle dolomite, which is now the main producing zone. Closer analysis of the totals reveals that western Kansas accounted for 1634 tests, of which 1186 were oil wells, 34 were gas wells and 415 were dry holes. The total potential initial daily production uncovered by the successful wells amounted to 1,691,000 bbl. of oil and 508,000,000 cu. ft. of gas. Both figures indicate a considerable decrease when compared with the proceeding year; in 1940 the respective figures were 2,128,000 bbl. and 1,289,000,000 cu. feet. In eastern Kansas a total of 479 wells were drilled. Among these, 260 were oil wells accounting for a daily initial potential production of 45,662 bbl. The new gas wells numbered 42 and added 290,438,000 cu. ft. per day to the gas potential production of the state. The remaining tests, 177 in number, were dry. It is interesting and significant that almost half (791) of the total wells drilled in western Kansas were drilled by the independent operators. Among the large companies the Cities Service Oil Co. drilled 169 wells; the Stanolind Oil and Gas CO., 101; the Skelly Oil Co., 80; the Continental Oil Co., 99, and the Shell Petroleum Co., 63 wells. In eastern Kansas the independent operators drilled 406 out of the total of 479 wells. Among the major oil companies the Cities Service Oil Co. drilled 38; the Phillips Petroleum Co., 13, and the Sinclair-Prairie Oil Co., II wells. The figures on relative percentages of dry holes to successful oil or gas wells are revealing. In western Kansas approximately one third of all wells drilled by the independent operators were dry holes. The major oil companies drilled approximately 844 wells in western Kansas, of which 678 were successful in finding either oil or gas. It thus appears that the major companies fared much Getter than the independents. In eastern Kansas the major companies drilled 73 wells of which 63 were successful in finding commercial quantities of oil or gas. No less than 286 wildcat tests were put down in western Kansas and 72 in eastern Kansas, or 358 in all, during 1941. Considerably more than half of these were drilled by independent operators; zoo in western and 66 in eastern Kansas. An exploratory hole % mile or more from production is regarded as a wildcat well in Kansas. On a percentage basis, approximately 75 per cent of all wildcat wells were failures; only 25 per cent found oil or gas in western

Jan 1, 1942

By John Greenawalt

IN view of the increasing importance of sintering in the beneficiation of iron ores preparatory to their reduction in the blast furnace, the writer believes the time is opportune for an up-to-date, though brief, discussion of the general principles of sintering, as well as a discussion of some of the recent improvements and mechanical developments that have been achieved in this industry, its present trend and future possibilities. Sintering may be defined as the agglomeration of fine mineral particles into a porous mass by incipient fusion caused by heat produced by com-bustion within the mass itself. Its first successful application, in connec-tion with the treatment of lead sulphide ores, was known as blast roasting. In this process the lead ore was given a preliminary roasting in a reverber-atory furnace, then the incandescent mass was placed in a pot with a grate and an updraft was applied. It was soon discovered that much better results were obtained by cooling the ore, moistening it, and placing it upon an incandescent layer of fuel previously placed upon a grate, and then applying the updraft blast of air until the charge was converted into a more or less agglomerated mass. The fuel was sulphur and the process one of desulphurization, which was the principal result desired. The application of downdraft to blast roasting brought about tremen-dous results; the principal one of which was that an air blast of high pressure could be passed through a layer of ore deposited on a grate, or on a grate covered by a layer of coarse porous material, without disturbing the particles of which the layer is composed. The air current is compelled to filter through the pores of the charge, whereas if the same pressure applied to the top surface of the charge with downdraft were applied to the bottom of the charge with updraft, the charge would be completely blown off the grate. Another result of reversing the draft was that a flame could readily be applied to the top surface of the charge for ignit-ing purposes.

Jan 1, 1938

By Henry Fernald

THE accounting system or bookkeeping methods of any company are principally the concern of that company and of those who are in control of its affairs. Its published financial report is, however, primarily intended for those who are not already fully informed regarding its operations and finances. Whatever may be the advantages of standardization of accounting and bookkeeping methods, it must be admitted that a company has a certain right to handle its accounts and keep its books and records in whatever manner may seem to it best adapted to its affairs, even though such methods may differ materially from those generally adopted by others. In its financial reports it should not, however, either ask or expect that the statements it makes or the terms which it uses will be given in its case a meaning and interpretation different from that which they are ordinarily considered to have in similar reports and statements of other companies. The particular form and arrangement of such reports is a matter concerning which there may be much difference of opinion. It is of little importance whether current assets come first or last in the Balance Sheet, but it is important that there should not be included under this designation any items which are not properly current assets within the generally accepted meaning of that term. The extent to which stockholders or others interested are to be made acquainted with the full details of a company's business is a question which the proper authorities must in each case decide. It should, however, be recognized that there are certain facts regarding a mining com-pany which must be set forth in a financial statement if it is fully to cover the conditions and affairs of the company. For example, a financial, statement which does not include or is not accompanied by a statement, of the ore reserves of the company does not fully set forth its financial condition. This is true whether the absence of such a statement of ore reserves is because it is not desired to make public the figures or whether it is because the ore reserves themselves are not definitely known, or accurately measured.

Jan 1, 1928

By David P. Shoemaker, Clara Brink Shoemaker

The I phase was discovered by Bardos, Malik, Spiegel, and Beck1 in the V-Ni-Si system at 1100°C and in the Mn-Co-Si and Mn-Ni-Si systems at 1000°C. Kuzma and Hladyshevskii2 and Kuzma, Hladyshevskii, and cherkashin3 have reported a new phase, which they named the S phase, in the Mn-Co-Si and the Mn-Ni-Si systems at 800°C at approximately the I phase compositions. The powder diffraction diagrams of the I and S phases, compared by Bardos el al.,1 are related but show distinct differences in relative intensities. Professor Paul A. Beck kindly sent us a specimen of the (v-Ni-Si) I phase for single-crystal study. Precession and Weissenberg diagrams taken with a tiny single-crystal fragment showed that the structure is monoclinic with a large unit cell. The cell dimensions were refined from a powder diffraction diagram taken with CrKa radiation in a 57.3-mm camera with our computer program LSCELP4 using only the indices of those reflections that were observed on Weissenberg diagrams (hnl, with n = 0 through 9 and n = 12) and precession diagrams (Okl, lkl, Izk0, hkl, hk2). Table I shows the agreement obtained between the l/d values calculated with the final values for the cell dimensions and the l/d values observed by Bardos et al .1 for I(V42Ni33Si25), by US for I(V41Ni36Si23), and by Kuzma and Hladyshevskii2 for S(MnpCoSi). The powder patterns contain many broad and diffuse lines. In fact practically all powder lines observed are near-superpositions of several reflections. The refinement program is not set up to handle several reflections contributing to one observed line: the position of each line is refined with the aid of one set of indices only. The final values for the cell dimensions were obtained from the lines of strong or medium intensity with the indices indicated by asterisks in Table I: a0 = 13.403(6), bo = 23.336(15), co = 9.129(6)A ß = 99.11(6) deg The standard deviations (given in parentheses) are those calculated by the refinement program from least-squares theory and do not take into account that the lines included in the refinement may not have been correctly indexed in every case or that the position of a line may also be partly determined by the overlapping reflections. The agreement between the calculated and observed I phase patterns is fairly good, although some discrepancies occur. Not all observed lines could be indexed with the incomplete set of sin-

Jan 1, 1968

By J. W. Taylor, E. G. Zukas

THE results of shock-loading studies on copper were reported several years ago by smith. In his experiments, Smith found that there was a correlation between the shock direction and the orientation of twins which the shock produced. By using free-surface-type shots in which the free surface of the specimen was not normal to the shock direction, he showed conclusively that twinning of copper in impulsive loading was caused by the rarefaction wave. Similar tests with iron, however, showed that it twinned during compression. More recent studies of iron2 and on Fe-Si single crystals3 have shown that twinning can be suppressed in these materials by shock loading at pressures high enough so that the velocity of the shock wave exceeds the elastic-wave velocity. From these observations, it appeared that twinning was caused by the shear stresses present in the zone undergoing adjustment from one-dimensional to three-dimensional loading. At high pressures, such a zone becomes so thin that there is insufficient time for the relatively ordered motion of atoms involved in twinning to occur. Twinning in copper, therefore, cannot be produced by a single compressive shock wave because resolved shear stress large enough to create twins exists only for a very short time (0.01 psec or less) before the pressure increases suddenly and loading becomes essentially hydrostatic. (A typical pressure vs time record for a copper shot, illustrating the short rise time of the compression wave, is shown in Fig. 1.) If, on the other hand, a second shock wave can be created in a precompressed sample, then the new elastic limit is several kilobars,4 and a resolved shear stress sufficient to cause twinning should be maintained for an adequate time period (0.1 psec or more). This experimental situation can, in fact, be realized. The experimental arrangement used to do so is shown in Fig. 2. By utilizing the pressure transformation in Fe-V alloys, it was possible to shock-load the copper in compression while the copper was already precompressed. In the first test, an 8 wt pct V-Fe sample was used as a driver for loading the copper, and the copper was exposed to the following series of compressive shocks: 1) an elastic wave of about 8 kbars, which is usually ignored in shock studies; 2) the pressure transformation wave for the driver of 200 kbars; and 3) the driving shock wave of 270 kbars pressure. Metallurgical determination of the angular twin distribution, shown in Fig. 3, with respect to the shock direction and the shock rarefaction direction (which was 23 deg from the shock direction) showed that twinning took place

Jan 1, 1965

By J. J. Gilman

Rates of prisnzatic plastic glide ( {1010}<2110>) in pure Cd crystals have been measured at temperatures from 158° to 276°C. The glide rate is proportional to the 2.75 power of the applied shear-stress. The activation energy is 29.2 kcal per mol. It is suggested that the rates of prismatic glide in Cd and Zn crystals are determined by the strengths of the atomic bonds across the prism planes. ALTHOUGH zinc and cadmium crystals both have hexagonal structures with nearly the same c/o ratios, their mechanical behaviors are quite different. Whereas zinc becomes quite brittle below room temperature, and cleaves readily on (0001) planes, cadmium is very ductile even at 4.2°K, and cannot be cleaved at any temperature. As part of a search for the explanation of this difference in behavior, a study has been made of prismatic glide in cadmium. It complements a previous study of the same phenomenon in zinc.1 The primary glide plane in cadmium is the basal (0001) plane, and the primary glide direction is the direction of atomic close-packing <2110>. However, if a tensile stress is applied parallel to the basal plane, then the shear stress on the basal plane equals zero so basal glide cannot occur. At low temperatures, deformation by twinning occurs; but at high temperatures, it has been found in this study that gliding on prismatic planes (1010) occurs in the close-packed direction. This is completely analogous with the case of zinc, except that lower temperatures are required. EXPERIMENTAL The experiments were done in nearly the same way as for zinc.&apos; Therefore, only the differences in the two sets of experiments will be described here; for other details the reader is referred to the previous paper. Crystals 6 by 6 mm sq were used that were grown from "Super Purity" 99.999 + pct Cd purchased from the New Jersey Zinc Co. The crystals were grown with their basal planes parallel to both the rod axis and one of the flat sides of the square cross section, A close-packed direction in the basal plane was oriented parallel to the rod axis. Gage sections were carefully machined into the crystals, and the surface damage caused by machining was removed with the same chemical polishing reagent as had been used for zinc. Thus, specimens of the same form and size as the previous zinc ones were produced. The crystals were heated to the test temperatures in a silicone oil bath (fused salts were tried first, but they reacted badly with the cadmium). An Instron tensile-testing machine was used for applying stresses to the crystals at various constant strain-rates. RESULTS The general behavior of cadmium crystals is much the same as for zinc. Only the constants that measure specific properties are different. Just as

Jan 1, 1962

By A. R. Jr. Amos

LOG washers have been used for many years in the washing of clay iron ores, phosphate rock and manganese ores, but not until the past 15 years have they been employed to any extent in the preparation of aggregate materials and fluxing stone. For a machine of such importance where tenacious clay or soft rock must be eliminated, there are few data generally available. The purpose of this paper is to set forth the results obtained from several operations, together with a few suggestions for planning a specific installation. Where the material to be washed out consists of loose surface soil, silt, or small amounts of quickly soluble clay, there is little competition with other forms of washers, because greater power and maintenance are required for the operation of log washers, but where the foreign matter is a stiff clay, such as occurs with high-calcium limestones and in marginal gravel deposits, the ability of other kinds of washers to eliminate com-pletely the hard clay balls is at least uncertain. Then the log washer comes into its own field, for with the breaking and churning action of the logs it will clean out the toughest clay. Even with material from the hydraulic dredge, if it contains tough clay, the log washer is desirable unless the gravel is subjected to a costly soaking and rehandling process. Recently there has been a considerable development in other types of machines to accomplish these results but it is not within the scope of this paper to make comparisons between competitive types, but to present the best obtainable data on log washers only. From the primitive design that gave it its name, a long log hewn from a tree, with paddles forged to shape from strap iron and attached by lag screws, the log washer has gradually been developed to the present all-steel type. As now manufactured, the log washer consists essentially of two built-up logs on which are mounted a series of paddles, carried by shafts fitted at the ends of the logs on bearings fastened outside the enclosing steel box, or trough, which is set at an angle of about 5° to 10° and into which the material is fed. Stuffing boxes at the places where the shafts pass through the box at the lower end are equipped with water-

Jan 1, 1936

By A. R. Jr. Amos

LOG washers have been used for many years in the washing of clay iron ores, phosphate rock and manganese ores, but not until the past 15 years have they been employed to any extent in the preparation of aggregate materials and fluxing stone. For a machine of such importance where tenacious clay or soft rock must be eliminated, there are few data generally available. The purpose of this paper is to set forth the results obtained from several operations, together with a few suggestions for planning a specific installation. Where the material to be washed out consists of loose surface soil, silt, or small amounts of quickly soluble clay, there is little competition with other forms of washers, because greater power and maintenance are required for the operation of log washers, but where the foreign matter is a stiff clay, such as occurs with high-calcium limestones and in marginal gravel deposits, the ability of other kinds of washers to eliminate com-pletely the hard clay balls is at least uncertain. Then the log washer comes into its own field, for with the breaking and churning action of the logs it will clean out the toughest clay. Even with material from the hydraulic dredge, if it contains tough clay, the log washer is desirable unless the gravel is subjected to a costly soaking and rehandling process. Recently there has been a considerable development in other types of machines to accomplish these results but it is not within the scope of this paper to make comparisons between competitive types, but to present the best obtainable data on log washers only. From the primitive design that gave it its name, a long log hewn from a tree, with paddles forged to shape from strap iron and attached by lag screws, the log washer has gradually been developed to the present all-steel type. As now manufactured, the log washer consists essentially of two built-up logs on which are mounted a series of paddles, carried by shafts fitted at the ends of the logs on bearings fastened outside the enclosing steel box, or trough, which is set at an angle of about 5° to 10° and into which the material is fed. Stuffing boxes at the places where the shafts pass through the box at the lower end are equipped with water-

Jan 1, 1936

By Elizabeth L. Robinson

INTRODUCTION The financial structure of the mining industry has changed strikingly over the last thirty years. The changes that have taken place in the last ten years include both the acceleration of adverse trends in familiar balance sheet numbers and ratios, and the subtle but extensive increase in the complexity and diversity of funding sources, both on and off the balance sheet. The objectives of this paper are: 1. to briefly trace the evolution of trends in the mining industry&apos;s financial structure; 2. to focus in more detail on changes in the last decade; and 3. to analyze those trends both within the framework of capital structure theory, and in the context of changes in business and economic conditions. This survey focuses primarily on the mining companies listed on the major U.S. stock exchanges, since financial data for these firms are readily available. The producers of minerals are a diverse lot, however, and the quantitative data on "the mineral industry" as characterized in this survey fails to encompass the financial arrangements for the bulk of production worldwide, whether owned by governments or private-sector enterprises. Even large portions of the U.S. minerals industry - subsidiaries of still larger firms, medium-sized privately-held companies, and the small miners - were not included in the quantitative part of the analysis. THE EVOLUTION OF THE INDUSTRY&apos;S FINANCIAL STRUCTURE In the aftermath of the business failures of the Great Depression, most borrowers and lenders considered minimal debt on the balance sheet the soundest policy. By the 1950&apos;s, however, a body of literature was developing which demonstrated that the use of leverage could improve the value of the firm, given a corporate tax structure which allows interest, but not dividends, to be deducted from income. Optimal Capital Structure The objective of undertaking a new project is to improve the wealth of the current owners of the firm. If internally-generated funds are insufficient to allow growth at the desired rate, the company can raise funds either by issuing new equity, or by incurring debt. The most attractive source is the one which will provide the funds for the lowest cost. Both stockholders and lenders expect to receive compensation for use of their funds at a rate which reflects two things: (1) the return they could earn in alternative investments, and (2) the riskiness of the projected return. Factors which increase business risk include the variability of demand, sales prices and input prices, and "operating leverage", or the proportion of fixed to variable costs. In addition, from the investors&apos; point of view, the use of financial leverage concentrates risk onto the shareholders, because lenders enjoy a prior claim in the event of bankruptcy. So although financial leverage can increase a project&apos;s expected rate of return, and therefore, presumably, earnings per share, too much debt will be perceived as uncomfortably risky by equity investors, and have a negative effect on stock prices. In theory, then, there should be an optimal level of debt which the firm&apos;s managers should seek to obtain in its financial structure. The desirable proportion of debt should in general be lower for a firm with a higher inherent business risk. In addition to their own judgement, financial managers are sensitive to the attitudes of lenders, rating agencies, and investment bankers in setting financial targets (Scott and Johnson). In practice, financial structure will also depend upon the company&apos;s growth rate and level of profitability, and conditions in the capital markets at a given time.

Jan 1, 1985

By L. O. Howard

R. HATCH, Garfield, Utah.-The object of the meeting, I believe, is to determine the proper chemical composition to insure long wear of a ball in a mill, This might also apply to rods. I feel that there is only one way of determining accurately the wearing qualities of balls in mills, and that is by actually wearing out 400 or 500 tons of different kinds of balls. Two things add to the wearing qualities of a ball: (1) the tenacity, with which the particular particles of iron or steel are cemented together; (2) the individual hardness of each particle. My experience is that a ball that has a Brinell of 550 to 650 will give comparatively long life. There is considerable difference of opinion as to the best steel and iron alloys necessary to produce a satisfactory grinding ball. Some favor chrome, some manganese and some nickel. Personally, I believe cast iron alloyed with chrome makes the best ball for small sizes; for large sizes (3 1/2 in. and up) steel alloyed with manganese is best. L. 0. HOWARD, Pullman, Wash.-How would this method apply to lining? A. KissocK, New York, N. Y.-I do not subscribe to that exactly. As I am connected with the Climax Molybdenum Co. you would hardly expect me to. We have been much interested in trying to work out this grinding-ball problem and have spent a great deal of thought and effort on it. As we are associated with the American Metal Co. and have a number of properties of our own, we are in position to try our ideas on ourselves first. We have tried different compositions, but have not done anything very remarkable with them yet, except that we have been able to say that the combination of chrome and molybdenum has given the best wearing ball. Mr. Hatch feels that iron is the best medium for grinding, but since toughness as well as hardness is a factor in wearability we feel that a well made steel is better for this purpose. Another difficulty with cast, or chilled, iron is lack of uniformity from day to day or from heat to heat and the impossibility of producing balls free from blow or shrinkage holes which materially affect their life. If cast iron is made hard it becomes brittle and lacks stretch or toughness. This prevents its use in the larger sizes, as breakage is a serious handicap to efficiency. We have tried hard and brittle balls and softer but very tough balls and have proved that maximum hardness, with sufficient toughness to prevent breakage, is the most important factor in resistance of a steel to abrasion. It is well known that chromium is one of the best hardening agencies for either iron or steel, and molybdenum is recognized as an element capable of introducing toughness. In other words, the proper combination of chromium and molybdenum permits unusual hardness with still sufficient toughness to stand up under severest impact. It is yet too early to give any actual mill results of this new combination and though we are proving our ideas at our own properties we have to depend on others to help us make the data more general and more worth while and would like to get some tests

Jan 1, 1928

By Donald Barton

THIS paper outlines a time-saving graphical method of calculation for application to the interpretation of observations with the Eötvös torsion balance. Preliminary to the treatment of this short cut method which has been found practicable, the principal formu-las by which the student of interpretation can calculate the gradient and differential curvature produced by different types of bodies in different types of situa-tions are presented and discussed. It is necessary to split most geologic bodies into a series of simpler ones for which not too complicated formulas are avail-able. The gradient and differential curvature effects are calculated for each of the simple bodies and then summed to the total effect for the whole body. The calculations are considerable in number and, though more tedious than difficult, should be&apos; entrusted to an experienced calculator. Considerable facility in qualitative interpretation can be acquired by the geophysicist from experience and from a thorough study of the types of gradient and differential curvature anomalies produced by the dif-ferent types of possible structural situations. How-ever, semi-quantitative calculations&apos; of the probable structure bring out many relations that are not evident in a simple inspection of torsion balance results ; it throws out as impossible or improbable certain of the alternative structural possibilities that may seem equally probable under simple inspection of the results; it will determine more accurately the position of the crest of the structure; and reduce considerably the un-certainty in the interpretation and it is necessary to intelligent interpretations. The calculation of such cross-sections consists of a trial-and-error calculation of a body that will give gradient and differential curvature effects as closely as possible the same as those observed. From his knowledge of the gradient and differential curvature produced by different types of bodies, the geophysicist sketches a tentative cross-section of the structure as indicated-to him-by the observed results of the torsion balance survey, and the calculator then splits the struc-ture into blocks, and calculates the gradient and differ-ential curvature block by block. If, as rather usual, the calculated .gradient and differential curvature pro-files diverge considerably from, the respective observed ones, it is necessary to add and subtract blocks from the cross-section until a close agreement is obtained .between the calculated and observed profiles. The com-plete calculations have to be gone through for each block that is added or subtracted.

Jan 9, 1928

By Thos Gibson

THE object of taxation is the raising of a revenue. Unless a tax accomplishes this, it is a failure. The right to take for public purposes a part of the moneys obtained from the carrying on of private enterprises is an attribute possessed only by a lawful government, and may indeed he called the supreme attribute of government. In free, democratic communities this power must of necessity rest upon the consent of the governed. Power implies obligation, hence it is obviously the duty of a government, in framing a system of taxation, to provide one which, while effective in producing a revenue, is also just and impartial. It will be conceded that mines and mining property ought to bear a fair share of the public expenditure. The question is, upon what basis taxation should proceed. Two separate taxing principles are usually contended for: Taxation should be proportionate to the benefits received by the person or property taxed; taxation should be based on ability to pay. A third is sometimes added, taxation should have reference to the extent and value of the natural resources enjoyed. As applied to mining taxation, it is pointed out by those who support the first mentioned basis that, mines being usually situated in rocky and hence sparsely peopled regions, mining companies are frequently obliged to construct roads, railways, telegraph and telephone lines, schools, water and sewerage systems, and many other amenities and conveniences of civilization, the cost of which in regions better suited for agriculture and consequently more thickly populated, has either been defrayed locally, or can be spread over a sufficiently large taxable group of people to materially lighten the financial burden on the mine. The mining com¬pany, it is argued, having made these outlays, should receive credit for, them and be relieved of taxation to a corresponding extent. There may be some force in this contention, but the situation is capable of relief without attempting to place taxation upon so unworkable a basis as the value of benefits received. Who is to be the judge of these benefits, and how are they to be valued? The very existence of a mining company and its ability to carry on business in peace and security, depend on the prevalence of law and order, which is a result of good government. The state provides protection against violence, and courts of law for

Jan 4, 1919

By Lucien Eaton

THE accuracy with which detachable bits can be sharpened and gauged by grinding has made possible refinements in design that cannot be attained by forging. This applies particularly to gauging, where accuracy is of the greatest importance. Gauge changes of 1/32 in., and even 1/16 in., are now feasible, whereas 1/16 -in. changes are about the limit in accuracy for forged bits. These small changes in gauge are feasible, however, only with certain fundamental principles of design. Within reasonable limits the depth to which a hole can be drilled is dependent primarily upon the loss in gauge, or diameter, of the bit. In drilling there is always a certain amount of " overdrilling "-the bouncing of the bit in the hole and its rotation wear away the walls-so that the actual diameter of the hole is greater than the diameter of the bit. The amount of this overdrilling depends upon the kind of rock being drilled, and is sometimes sufficient to permit the use of the same diameter of bit for the full depth of the hole. If, for instance, a 1 ¾ -in. diameter bit overdrills 1/32 in. in diameter, and loses 1/64 in. in gauge in drilling 2 ft. of hole, the bottom of the hole is still 1/64 in. larger than the original diameter of the bit, and a new 1 3/4-in. bit can be used to drill the next 2 ft. If, however, the overdrill is less than the loss in gauge, the next bit must be of smaller diameter. The first requisite in reducing loss of gauge in drilling is to have the points and corners of the wings of the bit cut circles of the same diameter, thus producing a reaming surface with continuous bearing on the wall of the hole. The greater the reaming surface, the less the gauge loss that is to be expected. If the reaming surface, however, is too large, it may impede the rotation of the bit through excessive friction. This principle was probably first recognized in the design of the Carr bit (Fig. 1)) a bit with a single cutting edge of wide angle, a definite reaming edge, and a large center hole. The same idea was followed in designing the double-taper cross bits, which are now standard almost everywhere Fig. 2 illustrates a typical double-taper cross bit. The taper from the point of the wing A to a little behind the corner B is 5° and from

Jan 1, 1939

By Hans W. Schreiber

INTRODUCTION At the end of the day, the decision by the sponsor to proceed with a project and to seek financing, or the decision by the financier to grant financing are made on a judgmental basis. Cash flow projections, sensitivity and risk analysis, the innumerable ratios applied by the financier, the so-called feasibility study, etc. are all only tools, and the degree to which they affect decisions is as highly varied as are the personality differences and business conduct and outlooks of the persons who render the decision of "go or no-go". The independent consultant, then, is expected to provide an additional increment of credulity and/or reliability to the "tools" which others will use in reaching a decision; the consultant is really not in a position to directly recommend a "go or no-go". PROJECT FINANCE INGREDIENTS The project finance situation has basically three ingredients: - The project; - The inherent risks attendant with project failure; - The parties. The project, to be viable for financing, will have certain essential characteristics, namely: 1. Clear title or rights to the mineral; 2. Proven definition/establishment of mineral quantity; 3. Financial viability; 4. Physical access consistent with financial viability; 5. A market for the product at a price and for the quantity consistent with financial viability; 6. Transportation/shipping from the project facility to the market at a cost consistent with financial viability; 7. Availability and demonstrated expertise of the developer of the facility; 8. Demonstrated expertise of the operator of the facility; 9. Production processes do not involve unproven new technology; 10. Availability of management personnel; 11. The property and the facilities have value (and thus can be used as collateral); 12. Government approvals/support, as required, will have been obtained; 13. The political environment is essentially friendly and stable; 14. The owner(s) of the project have the financial, strength to make equity contributions consistent with total required investment capital and project risk; 15. Backing by credit support other than that of the financier (i.e. guarantees); The inherent risks of failure are (Nevitt, 2nd Edition); 1. Completion delays with consequent delays in the generation of revenue 2. Cost overruns 3. Technical failure 4. Financial failure of contractors 5. Government interference 6. Uninsured losses 7. Increased price or shortages of raw materials, supplies 8. Technical obsolescence 9. Loss of competitive position in the market place 10. Expropriation 11. Inadequate/poor management The parties directly or indirectly integral to the project financing are: - The mineral rights owner - The developer - The operator - The equity investor

Jan 1, 1985

By Alfred Weiss

The Daniel C. Jackling Award, established in 1953, is presented for significant contributions to technical programs in mining, geology, and geophysics. This year&apos;s recipient, Alfred Weiss, was cited "For his pioneering achievements in applying systems analysis, operations research, and computer methods in exploration, mining, and environmental control; and in disseminating the new technology to the worldwide mining community; and for his lecture, “New Concepts and Tools in Decision-Making.”

Jan 1, 1979