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By Arthur F. Daily

8.5-1. Bucket Line Dredge. INTRODUCTION. The modern bucket-line dredge for mining placer deposits is a combined floating excavating machine and a gravity concentration system. Material is excavated at the forward end by the buckets, elevated, washed and screened, concentrated for recovery of valuable mineral, and discharged off the stern as coarse and small fractions. The end product is a concentrate consisting either of the valuable mineral(s) and associated heavy minerals, which are taken to a treatment plant on shore; or in the case of gold, a clean amalgam ready for retorting. The bucket-line dredge may be adapted for purposes other than mining for valuable mineral by installing, in lieu of a concentrating system, machinery for pumping all of the solids ashore in a pulp, or for producing washed gravel in selected size fractions of which all or a selected fraction is pumped to disposal areas on shore or into side barges. The two principal types of bucket-line dredges designed for mining are: 1) those having an inclined belt conveyor stacker to discharge the coarse fraction of washed tailing well astern of the hull, and sluices to discharge the sand fraction (Fig. 8.5-1), and 2) those having only sluices for discharge of all tailing astern. Use of the latter type has been confined, with few exceptions, to mining cassiterite-bearing deposits in Malaysia and at sea off Indonesia. Small dredges having only flumes for washing and concentrating all material dug by the buckets have been used for mining shallow stream valley deposits. GENERAL ARRANGEMENT. The general arrangement of a modern bucket-line dredge for mining tin, with a primary concentrating plant on board, is shown in Fig. 8.5-2. The hull and superstructure of most dredges are fabricated of structural steel; wood also has been used for both small and large dredges with complete satisfaction. All-riveted or partially welded unit hulls have been widely used and are desirable for exceptionally severe service. The hull

Jan 1, 1968

By R. H. Harrington

The definition of precipitation-hardening1 is well understood and its principles have been subjected to study for some time. However, the variation of properties with double aging, combined with strain-hardening, gives promise of new and useful phenomena. Properly to understand these distinctions, definitions of these terms are necessary. Precipitation-hardening1.—This reaction usually depends upon an alloy having such a composition that it consists only, or in major part, of but one phase, a solid solution, at a high temperature, so that, upon slow cooling, this solution breaks down into two phases, the solid solution and a compound. By heating the alloy to the temperature for maximum solution of the compound, quenching, and reheating to a suitable lower temperature for critical dispersion precipitation of the compound, useful properties of the alloy may be developed to a maximum. Double Aging.—Dougle aging in part is similar to the process for precipitation-hardening, consisting of heating a precipitation-hardening alloy to the solution temperature, quenching, reheating to the suitable dispersion precipitation temperature, strain-hardening, and again reheating to a suitable temperature to develop certain useful properties to a maximum. The strain-hardening may be induced by two methods: (I) a rate of cooling from the first reheat may suffice to strain the solid solution lattice of the alloy; or (2) the alloy may be cold-worked to a suitable degree between the two reheats. Pkecipitation-hardening of Copper-cobalt-beryllium Alloys1.2 The composition of principal interest is that of 2.6 per cent Co, 0.4 per cent Be, 97 per cent Cu. The alloy has been developed commercially and, with certain reasonable precautions, ordinary brass-foundry practice suffices to produce an alloy of high quality. Preliminary Precipitation-hardening Study.—Samples were cut from a I-in. round rod cast in a graphite mold. These samples were then

Jan 1, 1937

By J. D. Livingston, H. E. Cline

The lamellar-dendritic transition in Sn-Pb alloys near the eutectic composition has been studied at high growth rates. Lamellar structures were found over a substantial range of tin-rich compositions, and this range extended to increasingly tin-rich concentrations as growth rate increased. These results are discussed in terms of stability and competitive-growth arguments. Various experimental and structural limitations to the rate of directional solidification are discussed. The rate of heat removal at the heat sink is the major experimental limitation. ReCENT interet1,2 in the use of fine composite structures produced by directional solidification of eutectic alloys makes it important to determine the range of composition and growth conditions that yield such microstructures. Because increasing growth velocities produce increasingly finer microstructures, it is particularly significant to determine the factors limiting the rate of solidification. Mollard and Flemings3 have shown that composite structures, free of primary dendrites, can be obtained in Sn-Pb alloys of off-eutectic composition. The composition range of composite structures was found to increase with increasing values of G/V, where G is the temperature gradient and V is the growth velocity. These results are in good quantitative agreement with an analysis of the stability of a planar eutectic interface.4 This analysis specifically predicts that over a small range of compositions stable lamellar structures will be obtained even for G/V = 0, hence, even at very high growth rates. The lamellar-dendritic transition in Sn-Pb alloys has also been analyzed with a model based on competitive growth between dendrites and the composite structure.576 This treatment, based on earlier work on organic eutetics,7 predicts that the composition range yielding composite structures in Sn-Pb will increase rapidly at high growth rates. An increase in the composition range of composite structures at high growth rates was recently observed in Cu-Pb alloys near the monotectic composition.8 In view of these results, and the predictions of the stability and competitivegrowth analyses, it was decided to study the lamellar-dendritic transition in Sn-Pb alloys at high growth rates. EXPERIMENTAL Using 99.999 pct pure materials, a series of Sn-Pb alloys were prepared containing 16.8 at. pct to 27.6 at. pct lead. (Eutectic composition is 26.1 at. pct Pb.) Ingots were extruded to 0.175 in. rod, and some rod was drawn to 0.070-in. wire. Directional solidification was accomplished in two different ways, Fig. 1. For growth rates up to 2 x 10-1 cm per sec, a 0.175 in. diam sample was placed in a graphite crucible 5 in. long with 0.250 in. OD and 0.035 in. walls. Samples were melted under flowing argon in a vertical, platinum-wound furnace, and solidified by driving the crucible downwards through a \ in. hole in a water-cooled copper toroid, Fig. l(a). An insulated chromel-alumel thermocouple was imbedded in the center of a representative sample, and moved with the sample during solidification. The local temperature is plotted against the distance travelled by the sample in Fig. 2. As the growth rate increased, the solid-liquid interface moved closer to the water-cooled toroid and the temperature gradient increased. At growth rates above 10-1' cm per sec, heat was not removed fast enough and the sample moved into the toroid in the liquid state. The curve for V = 2 x 10-1 cm per sec shows a plateau caused by incomplete removal of latent heat from the interface, a problem which will be discussed later. To improve the heat removal, the toroid was cooled by nitrogen gas precooled in liquid nitrogen. This allowed successful solidification at rates up to 2 x 10-1cm per sec. Higher solidification rates required still more effective heat removal. Samples 0.070 in. in diam were placed in graphite tubes 0.125 in. in diam with 0.020 in. walls. Instead of cooling by sliding contact with a cooled toroid, these thinner samples were sprayed or directly immersed into water, Fig. l(b). After solidification, samples were stored in liquid nitrogen until they could be examined metallographic-ally. The surface was prepared with a diamond-knife microtome, followed by a light etch. The presence or absence of tin dendrites, Fig. 3, or lead dendrites, Fig. 4, was noted by optical microscopy, usually of a transverse section near the center of the sample. Replicas of the surface were prepared and examined in an electron microscope to resolve the fine lamellar structures, Fig. 5. The structures observed at various compositions and growth rates are summarized in Fig. 6. Composite structures were observed at increasingly cin-rich compositions as growth rate increased. This transition from dendritic to composite structure with increasing growth rate was also demonstrated by solidifying half a sample at a slow rate and then suddenly increasing the growth rate by lifting the furnace and quenching the sample with a water spray. A longitudinal section of this sample, Fig. 7, shows that the tin dendrites, which extended ahead of the slow-moving composite interface, were bypassed by the composite when the growth rate was increased. The range of composite structures at high growth rates was limited by the appearance of primary lead dendrites on the tin-rich side of the eutectic composition. Observation of representative longitudinal

Jan 1, 1970

Jan 1, 1955

By R. W. Cahn, C. D. Graham

The rate of growth of a single grain growing into a strained aluminum single crystal, measured by the conventional heat-cool-etch technique, is shown to decrease with time at temperature. The growth rate measured by means of X-rays, with the sample continuously at temperature, is found to be linear. Evidence is presented to show that the decreasing growth rate obtained by the conventional technique is due to abnormal recovery in the strained grain, and that the recovery in turn results from the heating and cooling cycles, rather than from the effects of etching. The experimental apparatus is described in an appendix. FREQUENTLY, the rate of grain boundary motion during recrystallization is determined by heating a sample to a known temperature for a given time, cooling to room temperature, and etching to reveal the boundary position. The cycle of operations is repeated as many times as necessary to establish the rate of boundary motion. Although this heat-cool-etch technique has been used by a number of workers over a period of many years,'-!' other investigators have encountered difficulty with the method."'. " They have attributed the erratic results to the effects of repeated heating and cooling, or of etching, or both, and have adopted an alternative experimental procedure in which a number of identical samples are employed, each sample being cooled and etched only once. This alternative method ove1.comes some difficulties, but introduces others. In particular, the incubation periods of the observed grains are unknown: any effect of crystal orientation on growth rate cannot be determined easily. A preferable method would be to measure the motion of a recrystallizing grain boundary with the sample at temperature without etching," but such measurements have in the past been restricted to nonmetals. This paper describes the construction and operation of a device, the goniometer furnace, with which the position of a moving grain boundary between a recrystallizing grain and the strained single crystal into which it grows can be measured by means of X-rays, with the sample maintained continuously at temperature. Goniometer Furnace The operating principle of the goniometer furnace is shown in Fig. 1. The sample, in the form of a bicrystal strip, is surrounded by a furnace, not shown in the sketch, and can be rotated about the two axes A and B which intersect at the point where the X-ray beam strikes the strip. The strip is oriented so that one of the two grains gives a strong Bragg reflection, which is detected by a suitably placed Geiger-Miiller counter coupled to a counting-rate meter When the strip is moved parallel to its own length in the furnace, arrow C, so that the X-ray beam strikes the second grain, there is in general no strong reflection. By noting the position of the strip at which the drop in Geiger counter reading occurs, it is possible to determine the position of the boundary. Measuring the change in boundary position with time at temperature gives the rate of growth of the recrystallizing grain. Details of the construction and operation of the goniometer furnace are given in the Appendix. Measurements showed that the temperature in the furnace was uniform within ±10°C over its working length of about 28 cm. The temperature at the measuring position, i.e., at the point where the X-ray beam struck the sample, was estimated to be constant within ±2oC. Using the goniometer furnace, the position of a stationary boundary could be measured with a reproducibility of ±0.3 mm. At elevated temperatures, 500" to 625"C, with the boundary in motion and the X-ray reflection less sharp, the estimated accuracy of each measured boundary position dropped to about ±1 mm. Experimental Results The test pieces were single crystals of 99.6 pet A1 —principal impurities 0.19 pet Fe and 0.12 pet Si— 1 mm by 1 cm in cross section and 6 to 10 cm in length, grown by the strain-anneal method. This relatively low purity material was used because of the difficulty encountered in producing strain-anneal single crystals of very high purity—99.996 pet—

Jan 1, 1957

By R. L. Smith, J. L. Rutherford

ALTHOUGH considerable effort has been devoted toward the determination of the mechanical properties of pure metals, it is extremely difficult to compare the results of such work. This is because of differences in method and type of test, grain size, heat treatment, and purity of material. There is very little information on the properties of most of the high melting point reactive metals with purities greater than 99.9 pct. Previous evidence concerning the tensile properties of unalloyed metals show that: body-centered-cubic metals are brittle at low temperatures; face-centered-cubic metals remain ductile; some hexagonal metals remain ductile, others become brittle. It may be that traces of impurities decrease the low temperature ductility of the body-centered-cubic lattice. This would suppose that a body-centered-cubic lattice free from impurities would exhibit nearly the same ductility as a face-centered-cubic structure. The present investigation has been an evaluation of the tensile properties of zone refined iron in order to determine whether higher purity material than that previously evaluated behaves differently. Experimental Procedure In this investigation, high purity iron was zone purified using the floating zone method.' The starting stock was obtained from two sources. The first,

Jan 1, 1958

By A. D. Hodges

The process to be described, whatever other merits (or demerits) it may have possessed, certainly proved a financial success under the conditions of the locality where it was introduced and where a refining process had been sought previously in vain. I have ventured to bring it to the notice of the Institute in the hope that it may prove of some interest as a solution of a practical problem, such as is often presented to the metallurgist in the remote mining regions of the West. The method was used first at the Lyon Mill at Dayton, Nevada, and has been adopted at other tailings-mills on the Cornstock. These mills treat two classes of tailings: "sand," or; material which has passed previously through the pans of the ore-mills; and " slimes," or the fine clayey material which, coming from the battery, is too light to settle in the tanks inside of the mills but is

Jan 1, 1886

By William E. Ford, Edward Salisbury Dana

This section includes one distinct group, the Stibnite Group, to which orpiment is related; the other species included stand alone. Pyr., etc. - In the closed tube melts and gives a dark red liquid when hot and a red- dish yellow solid when cold; in the open tube (if heated ver slow? ) sulphurous fumes, and a white crystalline sublimate of arsenic trioxide. B.B. on ciarcoaTburm with a blue Hame, emitting arsenical and sulphurous odors. Soluble in caustic alkalies. Artif. - Realgar is frequently noted as a sublimation product from furnaces roasting ores of arsenic. Crystals are produced when arsenic sulphide is heated in a sealed tube with a solution of sodium bicarbonate. Obs. - Realgar occurs usually in veins associated with silver and lead ores. It has been found in volcanic regions as a sublimation~duct. It has also been noted as a deposit from hot spring waters. It is often rtasociate wlth orplment. It occurs at Felsi5bBnya, Kapnik and NagyAg, Hungary; Allchar, Macedonia. Binnental, Switzerland, in dolomite. In the United States, at Mercur, Utah; in the Norris Geyser Basin, Yellowstone Park, as a deposition from the hot waters. Found at the Monte Cristo millin district, Snohomish Co., Washington: the namerealga7 is from the Arabic, Rahj af gh&r,powder of the mine. Use. - Was used in fireworks to give a brilliant white light when mixed with saltpeter and ignited. The artificial material is now used for this purpose.

Jan 1, 1922

By Robert B. Fulton

Commercially, celestite (SrSO,) is the only significant strontium mineral. Among other strontium-bearing minerals, only strontianite (SrCO,) occurs commonly; however, it is not an item of commerce. The principal production of celestite is in England, Mexico, and Spain. New production is now coming on stream in Canada. Consumption is mainly in the United States. Lesser quantities are consumed in Japan and Europe. Main uses are for the manufacture of strontium carbonate and nitrate. The carbonate is used in glass for TV tube face plates and in ferrites for magnets. The nitrate is used in pyrotechnics to which it imparts a characteristic brilliant red color, mainly in safety flares. Minor amounts of strontium compounds are used in electrolytic zinc manufacturing and very small quantities in greases, ceramics, soaps, alloys, and pharmaceuticals. Specifications and Prices Typical celestite specifications for the carbonate and nitrate markets are as follows: [ ] Celestite currently shipped from Mexico for carbonate manufacture tends to be slightly better than these industry specifications, assaying about 92-93% SrSO, with less than 1% BaSO, but it is generally below the 95% minimum required for nitrate production. Contract prices for celestite are approximately $32-34 per st at U.S. Port of Entry in 50 to 60-ton carload lots for Mexican material. Spot prices are generally reported as low as $20 per st but are for minor volumes. A recent sale of surplus from the U.S. stockpiles, announced by the General Service Administration (GSA), was 4005 st sold to Du Pont for $140- 455 or $35.07 per st. British celestite, ground, washed, and graded, 95% SrSO, bulk, ex- works, 240 mesh, is quoted at £ 28.75 per mt in British trade journals, and a recent figure quoted for crushed lump material was $36.00 per st f.0.b. vessel Bristol Channel port (1973). Specifications of manufactured carbonate made from celestite and sold in two grades, one to the glass industry, the other to the electronic industry for ferrites, are given in [Table 1]

Jan 1, 1975

By Donald E. Scheck, Da-Rong Chou

The application of geostatistics to coal reserve analysis is discussed. One problem in particular, the selection of the optimum locations for exploratory drill holes, is considered in detail. A new interactive program to help the geologist determine the best locations is described and applied to a specific property. The steps in the process are described and then illustrated using a mine's actual data. First, a variogram is selected based on graphical displayed information from the known sample data. Kriging estimates are made for the region of interest and the blocks within the region. The location of future exploratory drill holes is selected based on the criterion of minimizing the region estimation variance for a given number of exploratory holes. The least number of exploratory holes required to meet a specified upper limit on the regional variance is also determined. The computer generated recommendations for the exploratory drill holes are compared to a manually prepared drilling plan. The post- drilling analysis of the results is compared to the predicted values.

Jan 1, 1983

By Merlon C. Flemings, Theodoulos Z. Kattamis

Examination was made of the distribution of tnanganese and nickel in colutrrnar dendrites of a cast low-alloy steel; more limited work was corzducted on chromium. Corresponding "segregrction ratios" were calculnted and shown to be relntivelv insensitive to cooling rate (''segregation ratio" is defined (Is the ratio of maximum to minimum concentrations within a volume whose dimensions are the order of the dendrite-arm spacing). Isoconcentratiorl curves were determined by the electron micropvobe and by rt7etallografihic studies on specimens subjected to isothermal-transformation treatments. From construction of isoconcentration curves, morphology of columnar dendrites is descvibed as intermediate between Perfect rodlike and sheetlike morphologies. The study is extended to equiaxed dendrites and it is shown that the strcture of these dendrites is sittlilar in many respects to that of columnar dendrites. On the basis of tlze sheetlike morphology of dendrites, a simple model is pvoposed for calculation of honzogenization kinetics. Results of trzatllevlatical analysis brcsed on this utzodel are given. This analysis relates residual segregation to time at homogenization temperature; it is in agreement with experiment. Calculations are given which show that even for relatively rapidly cooled material (of 1-ine dendrite-artn spacing) treatmets at 1200°C or above are necessary to achieve slgxificant Izomogenization of elenlents other than carbon itz reasonable time (e.g., rnangclnese, nickel). Conlplete homogenization of carbon is obtnined at much lowev tenlperatures (below 870°C). IN dendritic solidification of castings and ingots, solute redistribution during freezing results in mi-crosegregation of most alloy elements. The micro-segregation is such that minimum solute concentrations occur at the center of dendrite arms and maximum concentrations occur between dendrite arms. Residual segregation after subsequent therma1 processing (homogenization) depends on maximum and minimum initial concentration, on the detailed geometry of the isoconcentration surfaces within interdendritic regions, on the diffusion coefficient of the solute, and on time of thermal processing. The objective of this work was to determine, for a low-alloy steel, maximum and minimum concentrations, and the geometry of isoconcentration surfaces, primarily in order to permit calculation of homogenization kinetics. Most of the work reported was conducted on Samples from a unidirectionally solidified, fully columnar ingot. This type of ingot is made by extracting heat during solidification from one face; techniques for accomplishing this have been discussed.' Samples were taken at several locations, up to 5.75 in. from the mold chill face; the bulk of the work was performed on samples at 5.75 in. Alloy cast was, nominally, 0.4 pct C, 1.8 pct Ni, 0.8 pct Cr, 0.7 pct Mn, 0.25 pct Mo, 0.3 pct Si, and the balance iron. Brief study was also made on samples from an ingot which solidified with equiaxed grain structure. SAMPLE PREPARATION AND ANALYSIS Samples for electron-microprobe analysis were incorporated in mounts that included pieces of electrolytic nickel, chromium, and manganese, in order to normalize the intensities of these solutes in the specimens; also, a piece of electrolytic iron was included to measure the background. All specimens were polished in the usual metallographic manner. After the microprobe traces were made, the path was revealed by etching the specimens with picral. All microprobe analyses were made by point counting, integrating for 30 sec. The distance between points was fixed from 2 to 10 p, according to the precision desired in each case, the fineness of the structure, and the concentration gradient existing in a given area. (The distance was chosen 2 to 5 p near the maximum-concentration regions and 5 to 10 p near the minimum concentration.) The "take-off" angle for the A.R.L.-Model No. 21000 microprobe employed was 52.5 deg. Samples for metallographic analysis of isoconcentration curves were prepared by austenitizing at 1540°F for 20 min, quenching to the nose of the TTT curves (1200°F), heat treating isothermally at this temperature for a given time 0, and then quenching to room temperature. Due to concentration gradients existing in a dendritic structure, no transformation will take place for a given time 0 of isothermal heat treatment in the regions where the a.lloy concentration is higher than a given limit. Thus, the dendrite appears limited by an isoconcentration curve and can be made to appear to grow by varying the time of isothermal heat treatment.

Jan 1, 1965

By W. I. Garms, J. L. Stevens

Because of the many conflicting opinions regarding the functioning of the ball load and the characteristics of ball wear in ball-mill grinding, the following résumé of reports covering recent tests conducted at the Hayden plant of the Kennecott Copper Corporation is submitted with the view of pointing out certain salient features that should throw additional light on the subject. Mills Used Cylindrical drum mills with trunnion feed and discharge were used. The discharge trunnion was 13½ in. in diameter. Dimensions inside the lining were 6 ft. 6 in. in diameter and 9 ft. 6 in. long. The mills were Britannia-lined and nine lifter bars projected 2 in. from the lining. The mill speed was 162/3 r.p.m. Feed to the mill was 9 per cent on 10-mesh, 85 per cent on 100-mesh, 77 per cent solids. New balls measured 2 in. in diameter and the approximate weight of the ball load was 40,000 pounds. Initial Test During a test that was being conducted to determine the relative economic value of standard cast balls vs. forged steel balls in the local 'grinding operation, certain observations were made in regard to the functioning of the various ball sizes and the characteristics of ball wear, which warranted a supplementary test for the purpose of confirming such observations. For the initial test, the necessity for developing a graduated load of the new forged balls before the test could be started was realized, but the time required to obtain a graduated load and the functioning of the various ball sizes was not clear. No advantage could be seen for starting out with a full load of forged balls, as this initial load, at the least, would have to be completely ground out and replaced by daily additions of balls before the graduation could be complete and a normal static condition of ball sizes reached. For a considerable period prior to exhaustion of this initial charge there would be an unusual quantity of worn balls of a certain size, which would not be typical of a normal charge and could influence the characteristics and functioning of the entire load. Therefore, it was decided to start by daily addition of the forged balls to a mill that contained a normal operating load of cast balls. After 88 days of operation the mill was shut down for inspection. By that time the load consisted of a mass of forged balls functioning around a large core of the residual material of the former cast-ball load. This core of cast slugs, locally referred to as "the kidney," was well defined from the forged-ball load.

Jan 1, 1947

By W. I. Garms, J. L. Stevens

Because of the many conflicting opinions regarding the functioning of the ball load and the characteristics of ball wear in ball-mill grinding, the following résumé of reports covering recent tests conducted at the Hayden plant of the Kennecott Copper Corporation is submitted with the view of pointing out certain salient features that should throw additional light on the subject. Mills Used Cylindrical drum mills with trunnion feed and discharge were used. The discharge trunnion was 13½ in. in diameter. Dimensions inside the lining were 6 ft. 6 in. in diameter and 9 ft. 6 in. long. The mills were Britannia-lined and nine lifter bars projected 2 in. from the lining. The mill speed was 162/3 r.p.m. Feed to the mill was 9 per cent on 10-mesh, 85 per cent on 100-mesh, 77 per cent solids. New balls measured 2 in. in diameter and the approximate weight of the ball load was 40,000 pounds. Initial Test During a test that was being conducted to determine the relative economic value of standard cast balls vs. forged steel balls in the local 'grinding operation, certain observations were made in regard to the functioning of the various ball sizes and the characteristics of ball wear, which warranted a supplementary test for the purpose of confirming such observations. For the initial test, the necessity for developing a graduated load of the new forged balls before the test could be started was realized, but the time required to obtain a graduated load and the functioning of the various ball sizes was not clear. No advantage could be seen for starting out with a full load of forged balls, as this initial load, at the least, would have to be completely ground out and replaced by daily additions of balls before the graduation could be complete and a normal static condition of ball sizes reached. For a considerable period prior to exhaustion of this initial charge there would be an unusual quantity of worn balls of a certain size, which would not be typical of a normal charge and could influence the characteristics and functioning of the entire load. Therefore, it was decided to start by daily addition of the forged balls to a mill that contained a normal operating load of cast balls. After 88 days of operation the mill was shut down for inspection. By that time the load consisted of a mass of forged balls functioning around a large core of the residual material of the former cast-ball load. This core of cast slugs, locally referred to as "the kidney," was well defined from the forged-ball load.

Jan 1, 1947

By J. M. Smith, D. Kunii, P. Adivarahan

Effective thermal conductivities were measured for seven samples of porous rocks through which gases or aqueous salt solution were flowing, parallel and countercurrent to the flow of heat. The results are analyzed in terms of the contributions of the solid and fluid phases to the total energy transfer. The solid contribution for the sandstone samples studied was found to be a Junction of the porosity and an effective thermal conductivity for the solid phase. The fluid contribution was a function of the Peclet number. Based upon the equations presented, the effective conductivity of the system can be estimated from the properties of the fluid, the flow conditions, and the porosity and pore-size distribution of the rock. INTRODUCTION Heat-transfer characteristics of porous media containing fluids are needed for the design and evaluation of thermal methods of petroleum production. The study reported here considers the problem of countercurrent flow of fluid and heat in sandstone rocks, and is a continuation of previous studies concerned with parallel and radial flow of energy and fluid in both rocks517 and beds of fine particles.6,10 In addition to these earlier works, Asaad,1 Kimura,4 Preston,8 Zierfuss and vlietll and waddams9 have reported effective conductivities for systems filled with stagnant fluids. There appears to be no published data on rocks through which fluids are flowing. The purpose of this study was to present such information and, particularly, to investigate the effects of properties of the rock and the flow rate on the results. The rock samples were naturally occurring sandstones from different locations and were similar to petroleum-bearing formations. The properties of the seven samples showing the range in porosities and permeabilities are given in Table 1. The mean pore sizes were calculated from mercury penetration data by averaging the radius with respect to pore volume. The details of this method and comparison with other procedures for estimating 7 are given elsewhere. Four fluids, nitrogen, carbon dioxide, helium and 10 weight per cent sodium-chloride solution were used with each sample. For Bartlesville sandstone, BA-5, runs were made at mean pressures from 15 to 250 psig using nitrogen. The other measurements were carried out at a mean pressure of 100 psig. The maximum temperature range eacountered was 70° to 300°F. The flow rate of fluid ranged from about 1.0 to 130 Ib/(hr)(sq ft), and this corresponded to a modified Reynolds-number range of 5 x 10-4 to 1.0. The variation in Prandtl number was 0.70 to 4.1. EXPERIMENTAL WORK The equipment consisted of apparatus to supply a constant flow of gas, or salt solution, at constant pressure to the bottom of a vertical test section, and metering and flow-regulation apparatus after the test section. The flow of salt solution was

By J. R. Guard

Development of electrical power in coal mining has been an outstanding example of adaptbility. It has accommodated itself to new inventions, changing mining methods, increasing demands, increasing safety requirements and many other new conditions. With the appearance of the continuous miner in the mining machinery picture, those engineers interested in the application of electricity to mining have been thinking about what new comination of electrical apparatus will best suit this newcomer. It is the purpose of this paper to discuss the relative costs of supplying d-c versus a-c power to mining equipment with particular reference to continuous miner setups. Assume that a-c power will be delivered to the mine at some high voltage suitable for transmision to the various substation locations. Typical voltage for this purpose is 4000 volts. The problem then is to change the power to some kind of power suitable for driving the motors of mining equipment. For safety and other reasons the voltage to be delivered to the motor terminals must be under 600 volts.

Jan 6, 1950

By C. R. Dodson, W. T. Cardwell

This paper presents the results of a theoretical and experimental study of the effect of preperforated liners on well productivity. The analysis concerns the rectangular type of slot, either machine or torch cut, which is common in California. Muskatla treated this problem recently in a mathematical analysis of the flow of oil or gas from natural reservoirs into both gun-perforated and slotted liners. This paper presents additional and simplified analytical considerations and conclusions for the slotted liner, the solutions being applicable in the laboratory as well as in the field. An application of the analytical methods to permeability measurements on mounted core samples is given, to show the effects of sealing wax or other obstructions on the end faces of the cores. Results Fig. I 'Ompares the results of some theoretical calculations with the results of electrical analogy experiments performed in the Standard Oil Company of California's Production Technology Laboratory at La Habra, California. Fig. I indicates that the flux into short, "three-dimensional slots" of the relative dimensions encountered in practice is approximately equal to that into full-length, "two-dimensional slots" having the same open fraction of pipe. (The same numbers of slot rows, and the same radius ratio are also implied.) It can be seen from physical considerations that the closeness of this approximation must improve as the ratio of the external radius to the internal radius increases. Therefore, it is possible to calculate the flow into a slotted liner using a simple modification of the Darcy equation: where N is .the number of slot rows and O is the open fraction of the pipe. Fig. 2 shows the results of calculations . using Eq. 28. The most remarkable features of Fig. 2 are the high flux values for very small open fractions of pipe. For instance, with six slot rows and a radius ratio of 500, 74 per cent of the open-hole flux may be obtained with only o.I per cent of pipe Open. Fig. 2 shows that for a given open frac tion of pipe, the flux is greater, the greater

Jan 1, 1945

By Heinrich Ries

Fullers' earth is a clay-like substance, which has the property of decolorizing or clarifying oils. An ultimate chemical analysis shows it to differ from most ordinary clays in having usually a high percentage of combined water and a low amount of alumina. There is probably a large amount of hydrous silica present. Fullers' earth possesses little or no plasticity, and in order to work properly has to be ground very fine. A chemical analysis is of little value at present in determining its quality; only a practical test suffices. Up to about two years ago all of the fullers' earth used in this country was imported from England; but about that time deposits were discovered in Florida, "† and since then rumors of its occurrence have been coming from all parts of the country. Next to the Florida deposits of fullers' earth, those of South Dakota are the most extensive thus far discovered in this country. The earth was first discovered near Fairburn, Custer county, and other deposits have since been prospected at Argyle, Minnekahta and other localities. Fairburn.—One of the first deposits located and opened up is five miles southeast of Fairburn, Custer county. The mine is a mile from the Fremont, Elkhorn and Missouri Valley Railroad, and the section exposed shows, beginning at the top: Feet. Micaceous sandy clay,......... 6 Fullers' earth,..........9 Micaceous sandstone,......... The fullers' earth passes upwards into the sandy clay, but in its purer portions it is a yellowish, gritty clay, with a somewhat

Jan 1, 1898

By Herbert D. Drechsler

Mining Finance is the interrelated aspects of "determining the total amount of funds to employ in a mining firm; allocating these funds efficiently to various assets; and, obtaining the best mix of financing in relation to the overall valuation of the firm." The first section is an overview of the financing problem through examination and discussion of the Balance Sheet and Income Statement. The next section is a discussion of the nature of the criteria developed in feasibility study. The third section describes type of capital funds, and the final section describes case studies of mining finance

Jan 1, 1985

By Herbert D. Drechsler

Mining Finance-is the interrelated aspects of "determining the total amount of funds to employ in a mining firm; allocating these funds efficiently to various assets; and, obtaining the best mix of financing in relation to the overall valuation of the firm". The first section is an overview of the financing problem through examination and discussion of the Balance Sheet and Income Statement. The next section is a discussion of the nature of the criteria developed in feasibility study. The third section describes type of capital funds, and the final section describes case studies of mining finance.

Jan 1, 1978

By R. Raring, W. J. Harris, J. A. Rinebolt

G. W. Geil (National Bureau of Standards, Washington, D. C.)—The authors state that the degree of accuracy realized in the experimental determination of a, is likely rather low. This inaccuracy is attributed to the difficulty in reading the load of the tension machine at the instant of fracture of the test bars. I believe there is another factor which may have added considerably to the inaccuracy in the determination of a,, namely, the determination of 8,. Fracture of a cylindrical tensile specimen of a ductile metal tested in tension at room temperature is generally initiated at the axis and rapidly propagates radially to the periphery of the necked section. During the propagation of the fracture, the metal at the rim of the minimum cross-section extends longitudinally and contracts radially. Thus values of 81, based on diameter measurements made after complete fracture of the specimens do not necessarily represent the strain at the initial fracture." Data obtained at the National Bureau of Standards with a 0.3 pct C steel in the condition as-quenched from 1575°F and tempered at 1000°F for 1 hr and tested in tension at room temperature indicated a considerable "rim effect" and as shown in Fig. 13, resulted in an apparent increase in Sf from 0.90 to 0.98. As the fracture strain of this steel is approximately equal to those of the steels reported by the authors, it seems probable that a similar "rim effect" may have added to the inaccuracies in the reported values of Si and accompanying values of El. R. Raring (authors' reply)—The authors are grateful to Mr. Geil for having called attention to a possible source of uncertainty in the determination of fracture stress, and they are in agreement with the principles upon which his discussion is based.

Jan 1, 1952