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By I. Cadoff, J. P. Nielsen

The Ti-C phase diagram exhibits a peritectic point at 1750°C and 0.8 pct C, and a peritectoid point at 920°C and 0.48 pct C. The maximum solubility of carbon in a titanium is 0.48 pct. The 6 region containing the Tic compound (20 pct C) extends to 11 pct C at the peritectic temperature. THE interest in the Ti-C alloy system stems from the fact that carbon occurs as an impurity in titanium alloys when graphite electrodes or graphite crucibles are used in their melting. Since titanium-base alloys are still in the development stage, some virtue may be found in carbon addition to titanium. The Tic compound is currently emerging as an important powder metallurgy base constituent similar to the WC compound. Ehrlich' identified the phases and structures present in the Ti-C system. The peritectoid region of the phase diagram was investigated by Jaffee et al." A preliminary diagram based on theoretical considerations was proposed at the outset of this research." The Tic compound has been investigated extensively and has been reported on in a large number of papers. Experimental Procedure Arc-melted alloys of 24 compositions in the range 0 to 20 wt pct C were investigated using metallography, X-ray diffraction, and, for the liquidus and solidus regions, incipient and complete melting. All alloys were prepared from iodide titanium (New Jersey Zinc Co., 99.95 pct Ti minimum) and spectroscopic grade carbon (National Carbon Co.). To prevent carbon spattering during arc melting the carbon was encapsulated in titanium. For alloys containing less than 1 pct C the powder was inserted into a capsule formed by drilling a hole in the as-received rod. For higher compositions, capsules were formed from titanium sheet. Arc Melting: The charges were melted in the copper-hearth cold electrode furnace shown in Fig. 1. This furnace is similar in principle to the all-metal unit adapted for titanium melting at Battelle Memorial Institute.' The transparent pyrex walls giving unlimited visibility during operation and the multiple-

Jan 1, 1954

By Joseph A. Norden, A. R. Willson

Much has been written concerning the hoisting equipment of various mines throughout the country, but most of the literature on the subject, if not all, describes equipment of extraordinary capacity and the small and medium-sized outfits have been neglected. The hoisting equipment here described is capable of handling about 1200 tons per day. It has not been worked to capacity, but 600 to 700 tons, together with men and materials, have been handled in two shifts without any great effort. Only one shaft extends from the surface to the lowest levels of the mine; see Fig. I. It is composed of three compartments, two of which are used for hoisting, and the third for water, air, and electrical lines, and for sinking purposes. In 1909, this shaft was raised from the 1000-ft. (304-m.) level to the 700-ft. There a station was cut and an air hoist installed. At this time all mining operations were confined to the upper levels of the mine; that is, above the 700-ft. The ore was dropped to this level through chutes from the 300-, 400-, 500-, and 600-ft. levels and then lowered in cars on cages to the 1000-ft., which is the main haulage adit, the mill and railroad bins being about 3000 ft. from the shaft. Orebodies were, in due time, developed on the 1000-ft. level and below. Therefore, in 1913,the shaft was sunk to the 1150-ft. level and thereafter sinking was continued at regular intervals until the 1500-ft. level was reached. But, hoisting from the 1300-ft. level was a difficult and slow process with the antiquated air hoist, so, in 1916, it was decided to raise the shaft to the surface and install a modern, electrically operated hoist. This was completed early in 1917 and the hoist was in operation in March of that year. The Hoist Figs. 2, 3, and 4 show various features of the hoist and electrical equipment. A Nordberg engine of the double-drum, geared type, designed for a 10-ton load, including rope, at a speed of 1500 ft. per min., is used. The drums are 7 ft. (2.1 m.) in diameter, with a 54-in. (137-em.)

Jan 1, 1922

NORTH AMERICA ALASKA Anchorage,-Ames, M. B. Culver, H. W. Fiedler, H. L. Fox, E. F. Gallemore, W. A. Kreitlow, E. J. Layfield, R. A. Saarela, L. H. Strandberg. H. Candle,-Bobbins, J. S. College.-Fackler, W. C. Joesting, H. R. Swift. R. E. "Wilcox, H. G.. Crooked Creek-Lyman. R. F. Fairbanks.-Beistline, E. H. CANADA Canadian Army Overseas,¬ Ball, H. D. Brides, C. Butterill. H. J. M. Ladner, F. E. Lane, H. C. Millar, R'. A. Murchison, R. G. Passow, F. M. ALBERTA Calgary-Allen, R. E. de Hart. J. B. Dingman, C. W. Furnical. G. H. Gray, J. G.

Jan 1, 1943

By R. S. Shoemaker, F. W. McQuiston

EMPEROR GOLD MINES Vatukoula, Fiji 1974 Operating Data to July 1 ORE DESCRIPTION: Ore bodies occur in basalt and associated ash beds overlain by andesite tuffs and sediments. The basalt in much of the ore mined is weathered with alteration of olivine to serpentine and iron oxides, and augite to chorite. The most important host minerals for gold are the tellurides sylvanite and hessite. Next in importance the sulphide s, pyrite, marcasite and arseno-pyrite. A small amount of free gold also occurs. Chalcopyrite, sphalerite, tetrahedrite, bornite, galena and native tellurium are present in small quantities. TYPE OF MINE: Underground and open pit ORE HAULAGE TO MILL: 3.5 ton bottom dump skips from underground. 7 ton trucks from open pit. CAPACITY IN TONS/24 HRS: 1345 short tons ASSAY HEADS (1973): 0.232 oz Au per ton, 0.357 oz Te per ton PRODUCTS: Gold Bullion (400 oz bars) Metallic Tellurium (1 2 lb bars ) RECOVERIES: AU 86.2% Te 88.0% ORE GRINDABILITY: 9.25 Kwh/T TOTAL POWER: 25.7 Kwh/T WATER: Pumped 112 mile to a 318, 000 gallon head tank. Consumption: 2 140 gal per ton, no reclaimed water used. TAILINGS: Pumped 2 /3 mile through 8" pipe. Uphill sections are steel. Downhill sections are fibro asbestos.

Jan 1, 1975

By M. H. Cullender

The performance characteristics 01 gas wells producing from formations which fail to stabilize within a relatively short period of time are obscured by the interrelation of the coefficient (C) and the slope "n" of the conventional back-pressure curve q = C(P2 f- p2s)n An empirical method is presented whereby the characteristic or true slope (11) of the back-pressure curve may be determined for a particular gas well. For those gas wells which do not stabilize within a relatively short period of time, the coefficient (C) is considered as a variable with respect to time and as a constant only with respect to a specific time. Thus, the back-presrure performance of such a well is presented as a series of parallel curve5, each curve representing the performance of the well at the end of a given time interval. Through use of the method presented, a simple presture gradient is developed and maintained within the drainage area around a producing gas well during the test period in order that the variation of the coefficient (C) with respect to time does not obscure the true value of the lope. INTRODUCTION The back-pressure method of testing gas wells as set forth by Schellhardt and Rawlins1 is dependent upon the requirement that a series of flow rates and corresponding pressure data be obtained under stabilized conditions. These data arc then plotted on logarithmic coordinates of flow rate (Q) vs difference in squared pressures (P2f — P2s) in order to determine the constants (C) and (n) for Equation 1. With respect to this method of presenting the performance characteristics of a gas well, it should be pointed out that although Equation 1 is an empirical relationship, the form of the equation was justified to a considerable extent by an independent development by Muskat and Botset.2 This development was theoretical in nature; however, certain assumptions with respect to the type of flow existing (viscous vs non-viscous) were madc which may or may not be correct. As the use of the method presented by Schellhardt and Rawlins spread through the industry, it became evident that the method of testing was applicable for those wells which approached stabilized prbducing conditions within a relatively short period of time. Performance characteristics could not be determined by this method, however, for wells which approached stabilized protlucing conditions slowly over a considerable period of time. This characteristic of "slow stabilization" has generally been associated with gas wells producing frorn reservoirs of low permeability. As the demand for natural gas continued to grow through the years, a great number of wells were completed in reservoirs of low permeability which exhibited "slow stabiliz:~tion" characteristics. Consequently, the problem of determining the true performancc characteristics of these wells became more apparent. It is with this problem in mind that the isochronal performance method of determining the flow characteristics of gas wells is presented.

Jan 1, 1956

By A. A. Terchick, J. C. Anderson, D. T. King

During 1972-1973, U.S. Steel acquired an existing southern West Virginia high volatile coal mine property including a 150 tph heavy media feldspar jig preparation plant. Expansion of production from the property required an increase in plant capacity to 300 tph, replacement of the feldspar jig with a hydrocyclone circuit, and inclusion of a water clarification thickener system. The rugged and restrictive nature of the terrain adjacent to the plant facility indicated prohibitive construction costs and severe site congestion would be encountered if a conventional water clarification thickener were installed. A high-loading, small-volume thickener, developed initially for the sugar beet industry by the Enviro-Clear Co. of New York, was investigated by U.S. Steel Research for possible coal preparation application, utilizing bench scale and small scale pilot plant evaluation methods. Results of testing at existing U.S. Steel preparation plants indicated predictable successful application of the Enviro-Clear thickener, so a 35-ft-diam unit was installed. The two-phase thickener system, utilizing presettled bottom sludge as a filter-clarification media, has successfully performed since commissioning in April 1973, producing clarified water competitive with conventional thickener systems with freedom from usual thickener operational problems.

Jan 1, 1976

By Mayumi Someno, Kazuhiro Goto, Masahiro Kawakami

The apparent rates of decarburization of liquid alloys of Fe-C, Fe-C-S, Ni-C, and Co-C systems and the rate of oxidation of solid graphite with pure carbon dioxide gas and with gas mixtures of carbon monoxide and carbon dioxide have been measured in the temperature range of 1000° to 1600°C. The cotnposition of carbon dioxide and carbon monoxide gas at the reaction surface has been measured by oxygen concentration cells with the ZrO,-CaO solid electrolyte. 1) The apparent rates of the carbon removal are essentially the same for all the cases of solid graphite, Fe-C, Fe-C-S, Ni-C, and Co-C systems under the same experimental conditions. 2) The apparent rates are independent of the carbon content in the high carbon concentration range but very much affected by the flow rate and the gas composition of the CO-CO2 reactant gas mixture. The ratio of the gas consumed by the reaction to the total quantity of the supplied gas is very large under the present experi~nental conditions. 3) There is a concentration gradient of' carbon dioxide in the vicinity of the reaction surface and the content of CO, becomes extremely small at the reaction surface. 4) A large time fluc-tuation of the gas composition was observed. This jluctuation implies the presence of unstable flow in the gas phase in the vicinity of the reaction surface. THE decarburization of molten steel by an oxidizing gas or by slag may be one of the most important chemical reactions in steelmaking processes. Nevertheless, the kinetics of this heterogeneous chemical reaction do not seem to be well-solved even with the previous studies. Although the conditions for the reaction in steelmaking processes are quite different from those in the laboratory scale, some critical experiments may give information on the mechanism of the decarburization. From the previous work,'-' it is known that the rate of the decarburization is independent of the carbon content in liquid iron with more than about 0.2 wt pct C when the oxidizing gases are supplied to the surface of liquid Fe-C alloys on a laboratory scale. Two rate-controlling steps have been proposed for the decarburization of liquid iron with the high carbon content: one is the surface reaction control proposed by Swisher and Turkdogan;' the other is that the rate is controlled by the gaseous diffusion through the gaseous stagnant layer. proposed by Baker. Warner, and Jenkins.7 and also by .Ito and Sano.2 In the present study, some experiments have been carried out for the evaluation of these rate-controlling steps in the decarburization of liquid iron with high carbon content. The apparent rate of decarburization of liquid iron has been compared with the rates of carbon removal of liquid Ni-C, Co-C, and solid graphite under the same experimental conditions. The composition of carbon dioxide and carbon monoxide gas at the reaction surface has been measured by oxygen concentration cells. I) EXPERIMENTAL PROCEDURE Fig. 1 shows the schematic diagram of the reaction chamber. Solid graphite and liquid metals were contained in an alumina or magnesia crucible of 32 mm ID and 35 mm in height. The samples were heated by high-frequency induction and the temperature was measured by the calibrated optical pyrometer. The temperature was held constant to within 10°C. The re-actant gases were supplied to the surface of the samples through the quartz tube of 8.0 mm ID. The distance from the end of the quartz tube to the surface was 20 mm. The block of high-purity graphite was cut and shaped to the inner profile of the crucible. The height of the shaped graphite was 18 mm, which corresponded to the depth of the liquid iron of 100 g. About 100 g of Fe-C alloy (4.20 to 4.40 pct C), Ni-C alloy (1.84 pct C), Co-C alloy (1.85 pct C), and Fe-C-s alloy (4.35 pct c, 0.5 or 1.0 pct S) were melted in the crucible. The reactant gases were pure CO, and gas mixtures of CO-CO,: the flow rates were controlled by capillary flowmeters with bleeders.

Jan 1, 1970

By W. J. Rude

LARGEST of the known commercial deposits of pebble phosphate are those found in Polk County, Florida. The phosphate bed, commonly known as the matrix, will consistently average 6 to 9 ft. in depth, and is found under 3 to 60 ft. of over-burden. The phosphate pebbles, white and black in color, varying greatly in grade, are found imbedded in a matrix of sand and clay; and range in size from the fines to pebbles 1 1/2 in. in diameter, although the average coarse size is approximately 1/2 in. in diam¬eter. On some of the washers all material under 14 mesh is lost. High-grade phosphate (75 per cent plus of bone phosphate of lime, CasP2Oa) is generally soft, the pebbles breaking up during the mining operation and in pumping; low-grade phosphate, 67 to 69 B.P.L., is black in color with hard pebbles with no loss encountered in pumping.

Jan 1, 1941

By E. P. Barrett

THE high-frequency laboratory induction furnace with a rotating liquid crucible enables research workers to conduct certain investigations heretofore very difficult or impossible to realize because vessels are not obtainable that are capable of resisting the physical conditions or the chemical actions to which they are subjected. Applications for patents covering commercial uses of centrifugal liquid crucibles were filed in the United States in 1919,1 in France in 1925, in the United States and Germany in 1926,2 and in France in 1927.3 In 1928, Schuette and Maier,4 of the Bureau of Mines, reported the construction of a whirling table beneath a high-frequency induction furnace. SHAPE AND SIZE OF CENTRIFUGAL LIQUID CRUCIBLES When a vessel containing a liquid is rotated, the inner surface of the liquid takes the shape f a paraboloid under the simultaneous action of centrifugal force and gravity. The internal dimensions of the paraboloid rotating liquid crucible are governed by the diameter of the container and its speed of rotation. Melted Wood's metal was poured into cylinders 2 ½ in. in diameter, which were rotated at 180, 300, and 468 r.p.m. When the metal was solid, a slurry of plaster of Paris was added, and rotation continued until the plaster had set. Fig. 1, a photograph of sections f the cylinders, shows the effect f speed f rotation of the containers upon the shape f the inner surface f the rotating liquid crucibles.

Jan 1, 1938

By K. R. Garr, D. Kramer, A. G. Pard

EXPOSURE of steels to a fast-neutron flux results in helium generation by (n,a) reactions. The elements Fe, Ni, Cr, and N are major participants in the (n,a) reaction and helium concentrations of up to 5 x 10"5 atom fraction could accrue in fuel clads after a year of service in proposed fast reactors.' Such concentrations of helium can severely reduce the ductility of alloys at temperatures of reactor service. The phenomenon of helium embrittlement has been studied in austenitic alloys which were irradiated with particles as a rapid means of producing significant helium concentrations.2-5 The pres-ent work is a continuation of those studies and is concerned with helium effects in a ferritic stainless steel. I) EXPERIMENT Small sheet tensile samples with a gage length of 0.50 in. and a cross-section of 0.009 by 0.040 in. in the gage length were punched from cold-rolled type 405 stainless steel. The composition of the steel used in this work is given in Table I. Prior to helium injection, the samples were annealed 24 hr at 760°C which caused complete recrys-tallization with a resulting grain size of 40 u. This treatment rendered the alloy completely ferritic and carbide particles, 0.5 to 2 uin size, were present at a density of 1 x 1011 cm-3, Fig. 1. These carbide particles were probably a mixture of the M7C3 and M4C types.6 Helium was injected into the samples by irradiation with a particles from a cyclotron, which produced uniform concentrations through the center two-thirds of the sample thickness. Details of this procedure were previously described.' The average helium concentration, as measured on a gas-source mass spec- 11) RESULTS A) Tensile Tests. The results of the tensile tests are given in Table I1 where the values shown are averages of two samples. There was no significant effect of helium on either the yield strength or tensile strength at 550" or 650°C but an increase in both is apparent at 750°C. Samples with helium showed a 20 pct loss in total elongation at 650°C which increased to a 55 pct loss at 750°C. The uniform elongation is not affected by helium at 550" or 650°C but shows an increase at 750°C.

Jan 1, 1970

Year Institute of Metals ? Petroleum - Iron and Steel ? Coal ? Mineral Industry Education - Industrial Minerals 1918 W M CORSE 1919 1920 W H BASSETT 1921 1922 W B PRICE 1923 E DEGOLYER 1924 G K ELLIOTT 1925 F JULIUS FOHS 1926 PAUL D MERICA 1927 JOHN M LOVEJOY 1928 S SKOWRONSKI A W AMBROSE RALPH H SWEETSER 1929 J B UMPLEBY G B WATERHOLSE 1930 ZAY JEFFRIES C V MILLIKAN W J MACKENZIEHOWARD N EAVENSON 1931 SAM TOUR C E BEECHER F M BECKET 1932 C H MATHEWSON EARL OLIVER F N SPELLERTHOMAS G FEAR C H FULTON

Jan 1, 1952

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members and guests who called at Institute headquarters during the period Apr. 10, 1916; to May 10, 1916: Philip P. Baily, New York, N. Y. George W. Otterson Seattle, Wash. John M. Brooks, Jr., Knoxville, Tenn. C. Q. Payne, New York, N. Y. C. A. Burdick, New York, N. Y. Charles F. Potter, Los Angeles, Cal. W. N. Crafts, Oberlin, Ohio. Albert E. Rhoads, Harrisburg, Pa. Andrew B. Crichton, Johnstown, Pa. M. F. Sayre, Schenectady, N. Y. 0. P. Hood, Pittsburgh, Pa. H. V. Smythe, Northpines, Ont., Canada. W. McA. Johnson, Tulsa Okla. W. 0. Snelling, Long Island City, N. Y. G. H. Morgan, New York, N. Y. W. H. Staver, Ophir, Colo. E. G. Norton, Chicago Ill., A. W. Tucker, Salisbury, N. C. M. L. O'Neale, Coal City, Ala. Andrew Weisenburg, Philadelphia, Pa. Arthur H. Brown has resigned his position with the Dome Lake Mining & Milling Co., South Porcupine, Ont., Canada. Robert Sterling has resigned his position as chief engineer of the Goldfield Consolidated Mines Co., Goldfield, Nev., to accept the position of assistant manager of the vanadium mines of the Primos Chemical Co., Vanadium, Colo.

Jan 6, 1916

By H. P. Greenwald

THOSE interested in the early developments and experiments, both in the United States and abroad, that led to modern rock dusting, will find an excellent summary in a paper by George S. Rice,13 published in 1914. The period from 1914 to 1924 was one of intensive experiment on coal-dust explosions in the United States; abroad, war activities and rehabilitation stopped this work over a large part of that decade. Amer-ican findings were published by the Bureau of Mines, particularly in Bulletins 167 and 268. It is convenient to consider that in the United States rock dusting to prevent coal-dust explosions in mines was initiated in 1924 with the publication of tentative specifications.17 This was followed in 1925 by an investigation of methods and costs12 and approval by the American Engineering Standards Committee of a Recommended American Prac-tice.18 Approximately 13 years have elapsed since this approval, and inasmuch as changes in rock-dusting practice in the United States have been evolutionary, it is necessary to consider this entire period as "recent" in some phases of the work. There have been no official changes in the Recommended American Practice since its approval. This paper reviews as briefly as possible knowledge acquired since the issue of the earlier papers mentioned, through experience in mines and experiments conducted by different organizations engaged in the pro-motion of mine safety.

Jan 1, 1938

By AIME AIME

TO attempt to say anything adequate about Eugene McAuliffe as a human being, engineer, or executive in this brief space is ridiculous, for one could extol his virtues at length in all three catagories. Too, one might dwell on his good humor, and also his modesty, for lie did not wish even these few words to be said, "having no illusions regarding either ability or achievement, not even blessed with good looks." Mr. McAuliffe was born in England just seventy years ago. Twenty years later he started at the bottom with the Northern Pacific, gradually being promoted to locomotive fireman, engineer, and so

Jan 1, 1936

By J. C. Irvine

Meramec Mining Co., a joint venture of Bethlehem Steel Corp. and St. Joe Minerals Corp., mines and pelletizes iron ore at the Pea Ridge mine. The Pea Ridge property is located near Sullivan, Miss., about 113 km (70 miles) southwest of St. Louis. The ore body was delineated in the mid-1950's by St. Joe during a lead exploration program. The first test holes drilled on the Pea Ridge magnetic anomaly revealed the presence of a large magnetite deposit; further drilling in 1956 and 1957 confirmed that the ore body was mineable. Meramec Mining Co. was incorporated in 1957 and shaft sinking began late in the year. Production began in April 1964. The ore body is overlain by about 400 m (1300 ft) of flat-bedded sediments. It is tabular, about 800 m (2600 ft) long and up to 180 m (1600 ft) thick. It dips about 80° and is of unknown depth. The ore is mainly high-grade magnetite with small zones of specular hematite. The wall rock is a Precambrian rhyolite porphyry.

Jan 9, 1976

By Arthur F. Taggart

This paper proposes two units (believed to be new) for designating, respectively, capacity and efficiency for primary and intermediate crushers. Capacity Operators know that the tonnage of rock that can be put through a particular crusher in a given time depends primarily upon the crusher setting (open setting for jaw and primary gyratory types; closed setting for cones and rolls), and secondarily on the lithological character of the feed, its maximum size, the amount of fines that it carries, its moisture content, and the method of feeding. The proposed capacity formula states a relationship between all of these factors in one empirical equation, as follows: Tr = TR80K'K" [I] in which Tr, called "reduction tons per hour" is the new capacity unit; T = tons of feed per hour requiring crushing; R80 = "80-per cent reduction ratio"; and K, K', and K" are constants that approximate quantitatively lithological character, moisture content and method of feeding, respectively. T is the hourly weight of material in the feed that is coarser than the coarsest discharge of the crusher. (For marked departures from the normal specific-gravity range—2.5 to 2.7—T should be adjusted to corresponding volumes.) In the crushers under consideration, discharge from the crushing zone is limited by the minimum dimension of a particle. Passage of the particle through a square-mesh screen is limited by its intermediate dimension. Sheppardl has shown that the ratio of maximum: intermediate: minimum average dimensions of broken rock fragments may be taken as about 1.5:=:0,6 for nonslabby rocks such as are normally crushed, while for slabby rocks, such as thin-bedded sedimentaries, foliated schists and gneisses, and the blocky metamorphics, the ratio is of the average order I.3:I:o.3, with the possibility of an even smaller relative value for the thickness. Gaudin2 finds the corresponding ratio for —I50 + 200-mesh pyrite to be I.4: I:0.6. The hourly tonnage of crusher-plant feed, therefore, should be diminished by the amount thereof that would pass a square-mesh screen of which the aperture is S times the crusher setting, where S is a shape factor with the value 1.7 for rocks that break exceptionally cubic; 2 for ores and rocks that exhibit no appreciabie tendency to slabbiness; and 2.5 to 3, or, in exceptional cases, even larger, when the tendency to slabbiness is marked. R80 is the quotient of the theoretical square-mesh aperture that would pass 80 per cent of the feed, divided by the aperture that would pass 80 per cent of the product. It is best determined from screen tests. If, as is usual with primary crushers, a sizing test of feed is not available, the

Jan 1, 1943

By Arthur F. Taggart

This paper proposes two units (believed to be new) for designating, respectively, capacity and efficiency for primary and intermediate crushers. Capacity Operators know that the tonnage of rock that can be put through a particular crusher in a given time depends primarily upon the crusher setting (open setting for jaw and primary gyratory types; closed setting for cones and rolls), and secondarily on the lithological character of the feed, its maximum size, the amount of fines that it carries, its moisture content, and the method of feeding. The proposed capacity formula states a relationship between all of these factors in one empirical equation, as follows: Tr = TR80K'K" [I] in which Tr, called "reduction tons per hour" is the new capacity unit; T = tons of feed per hour requiring crushing; R80 = "80-per cent reduction ratio"; and K, K', and K" are constants that approximate quantitatively lithological character, moisture content and method of feeding, respectively. T is the hourly weight of material in the feed that is coarser than the coarsest discharge of the crusher. (For marked departures from the normal specific-gravity range—2.5 to 2.7—T should be adjusted to corresponding volumes.) In the crushers under consideration, discharge from the crushing zone is limited by the minimum dimension of a particle. Passage of the particle through a square-mesh screen is limited by its intermediate dimension. Sheppardl has shown that the ratio of maximum: intermediate: minimum average dimensions of broken rock fragments may be taken as about 1.5:=:0,6 for nonslabby rocks such as are normally crushed, while for slabby rocks, such as thin-bedded sedimentaries, foliated schists and gneisses, and the blocky metamorphics, the ratio is of the average order I.3:I:o.3, with the possibility of an even smaller relative value for the thickness. Gaudin2 finds the corresponding ratio for —I50 + 200-mesh pyrite to be I.4: I:0.6. The hourly tonnage of crusher-plant feed, therefore, should be diminished by the amount thereof that would pass a square-mesh screen of which the aperture is S times the crusher setting, where S is a shape factor with the value 1.7 for rocks that break exceptionally cubic; 2 for ores and rocks that exhibit no appreciabie tendency to slabbiness; and 2.5 to 3, or, in exceptional cases, even larger, when the tendency to slabbiness is marked. R80 is the quotient of the theoretical square-mesh aperture that would pass 80 per cent of the feed, divided by the aperture that would pass 80 per cent of the product. It is best determined from screen tests. If, as is usual with primary crushers, a sizing test of feed is not available, the

Jan 1, 1943

By J. M. Ohm, Carl M. Bunker

Two special tools for recovering gamma-ray probes and logging cable from drillholes have been designed by Ohm and Bunker and constructed by Ohm. Though intended specifically for U. S. Geological Survey equipment, they may be used with other equipment of the same general type. Fishing Tool for Probes: A fishing tool of the overshot type (Fig. 1) was designed to retrieve logging probes (sondes) that become disconnected from the logging cable and are trapped in the drillhole. When the tool slides over the top of the gamma-ray probe, studs on the bottom engage the shoulder near the top of the probe (Fig. 2), which is then pulled to surface.

Jan 10, 1959

By H. L. Monroe

Meramec Mining Co., owned 50% by St. Joseph Lead Co. and 50% by Bethlehem Steel Corp., is engaged in mining, concentrating and pelletizing iron ore from the Pea Ridge Mine which is located about 75 miles southwest of St. Louis. The Pea Ridge orebody lies under some 1300 ft of limestone, dolomite, shale, and sandstone. It runs from east to west for about 1/2 mile and varies in width up to a maximum of around 600 ft. The orebody dips about 80" S. The ore is high grade magnetite with some local zones of specular hematite. The Precambrian country rock is rhyolite porphyry.

Jan 12, 1965

By Roger B. Alke

INTRODUCTION Request to Mine Beneath Bridge The Jakes Run Bridge is a reinforced Portland concrete arch filled bridge located on WV Route 7 near Pentress, WV. The bridge has a span of 22.9 m (meters) and a height of 4 m above normal pool elevation to the underside of the center of the arch (See Fig 1). The bridge is a two lane structure with a width of 6.86 m. The structure is over 50 years old having been built in 1929 and is owned by the Department (WV Department of Highways). [ ]

Jan 1, 1984