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By T. Nakao

Fujiwara quarry had been operated by the glory-hole benchcut mining system, but as it became difficult to meet expanding demand with this system, a central-shaft mobile crushing plant (MCP) system was introduced in 1979. This MCP is equipped with a hydraulic walking system manufactured for the first time in Japan. Central-shaft mining is now the common mining method of Japanese limestone quarries. With this method, crushing facilities are usually installed at the bottom of the shaft. But at the Fujiwara quarry, MCP was adopted and installed on the quarry surface. Many MCPs are operated in foreign countries, but few examples exist in Japan. Normally, Japanese limestone deposits lie in high mountain, obviously making it inconvenient for MCPs to walk in and around the quarry. This difficulty, however, was overcome, and the MCP has operated satisfactorily and efficiently for two years since its installation. To overcome difficulties in the central-shaft MCP mining system, two mining methods are employed: the slice-down method and the block-cut method.

Jan 1, 1985

By Leon Y. Sadler

Three new transfer functions relating the time response of the amount of floatable mineral in the under flow to time-dependent changes in the amount of floatable mineral in the feed to the cell are presented. Using experimental stimulus-response data obtained from the flotation of -200+325-mesh glass spheres in a rotor-stator-type cell, the new transfer functions are compared to the only transfer function to be presently found in the literature by nonlinear least-squares fitting in the frequency domain. The new mathematical model based on the amount of available bubble surface area and its rate of introduction is quite promising. The transfer function which allows for a distributed first-order flotation rate constant also gives good results. Simultaneous sodium chloride tracer and glass bead stimulus-response tests show that the mixing conditions in the cell were nearly ideal. It is felt that the new transfer functions presented offer excellent alternatives for use in the design of automatic process control equipment for the continuous mechanical froth flotation cell.

Jan 1, 1974

By D. V. Fites

Criteria for deciding when rock should be ripped and what ripping equipment and techniques should be used in given situations are discussed in this article. The relation between ripper performance and seismic wave velocities in various types of rock is also discussed. The ripper is not a new tool. In fact, it dates back as far as the Roman Empire. The Roman's ripper-mounted on wheels and shaped something like a plow — was pulled by oxen and used to loosen the earth for the shovelers and basket carriers building the Appian Way. There are records of rippers being used in this country in railroad construction between 1860 and 1880. However, the ripper as we know it today did not appear until about 1930. Tractor-drawn models were in use in 1931 on the Hoover Dam project. At that time they weighed about 7500 lb and were pulled by tractors with about 75 flywheel hp and up to 30,000 Ib total weight. The chief shortcomings of trailed

Jan 1, 1969

By J. S. Crump, C. R. Hocott, A. E. Hoffman

Planning of the efficient operation of a gas-condensate reservoir requires a knowledge not only of the gross phase behavior of the system but also of the equilibrium distribution of the various components between the gas and condensate phases. This equilibrium distribution can be calculated with appropriate equilibrium constants. In this paper are presented equilibrium constants determined experimentally for the oil and gas phases initially present in the same reservoir and for the gas and condensate phases of the gas cap material at a series of pressures below the original reservoir pressure. Also presented is a method for the correlation of the experimentally determined equilibrium constants. The utility of the correlation is demonstrated further by an example of its use in adjusting the equilibrium data to permit their application to another gas-condensate system of similar composition. INTRODUCTION Planning of the efficient operation of a gas-condensate reservoir requires a thorouugh knowledge not only of the gross phase behavior of the particular hydrocarbon system but also of the equilibrium distribution of the various components between the gas and condensate phases. At the initial conditions of reservoir temperature and pressure, the original hydrocarbon materials in a gas-condensate reservoir or in the gas-cap of an associated reservoir exist in a single, homogeneous vapor phase. However, some condensation of hydrocarbons to a liquid phase usually occurs in the reservoir as pressure declines incident to production. Because of this condensation. the produced gas changes composition continuously. The composition of the produced gas, as well as that of the condensed liquid, can be calculated from the composition of the original reservoir material through the application of appropriate equilibrium constants or "K"-values provided these values are known. Equilibrium constants have been used for many years in problems of surface separation of gas and oil and natural gasoline recovery. However, no satisfactory equilibrium data at reservoir conditions have been available for the higher boiling hydrocarbons which acquire abnormal volatility at high pressure and are therefore present in the gas phase in condensate reservoirs. Early work in this field indicated that the behavior of the higher boiling hydrocarbons largely determines the behavior of gas-condensate systems at high pressure.' Consequently, a portable test unit was designed to permit determination of the distribution of the heavier hydrocarbons between the gas and liquid phases of a gas-condensate system. This paper describes the test equipment and presents the results of an investigation of the reservoir fluids from an associated oil and gas reservoir in the Frio formation in Southwest Texas. Also presented is a method for correlation of the experimentally determined equilibrium constants, together with an example of the use of the method in adjusting these data for application to another gas-condensate system of similar composition. FIELD TESTING AND SAMPLING In order to determine the compositions of the reservoir fluids, field samples were secured from two different wells, one completed in the oil zone, and one completed in the gas cap. The oil well was completed through perforations in 51/2-in. casing at a depth of 6,822-6,828 ft subsea. Pressure and temperature traverses made in the well indicated the pressure and temperature to be 3,831 psig and 201 °F, respectively, at a depth of 6.828 ft subsea. Subsurface samples were taken from this well after a four-hour shut-in period.

Jan 1, 1953

By J. G. Richardson, F. M. Perkins

Results and procedures are pre-cented covering a laboratory investigation of the effect of rate of water advance on the displacement of oil from clean water-wet sands. The experiments included water floods at atmospheric pressure with and without gas present over a range of flow rates from reservoir rates to rates ten thousand-fold higher. Water floods were also conducted at various rates at elevated pressure with no gas present. Other tests were made at elevated pressures by forming a free gas saturation by evolution of gas from solution in the oil before water flooding. Recovery of oil was found to be independent of the rate of water advance with or without gas present and independent of the pressure level of the water flood. A dimensionally-scaled model of a reservoir composed of a thick uniform sand was used to study the effect of rate on the tendency of water to underrun the oil because of the greater density of the water. Another model was used to study the effect of rate on the tendency of water to channel down the more permeable sand in a stratified reservoir composed of sands of diffierent per-meability in intimate contact. The effect of the presence of gas on the flooding conformance was studied with both models. The results obtained using these simple models provide a basis for predicting behavior in more complicated systems. INTRODUCTION In spite of the great amount of research on the flow of fluids in porous rocks, there still exists some disagreement as to the influence of the rate of water advance on the displacement of oil by water flooding. Various investigators have found that increasing the rate of water injection would decrease, increase, or have no effect on recovery of oil. One reason for this disagreement has been a lack of understanding of the effects of the capillary forces which influence the results obtained in the laboratory at low rates with short columns. Other causes of the disagreement have undoubtedly been inconstancy and uncertainty of the wetting properties of the porous media studied, inaccurate saturation determinations, and in some instances conclusions based on insufficient data. Capillary forces are involved in the displacement of oil by water in two ways. On the microscopic scale, the capillary forces control the dis- tribution of oil and water in the pore spaces of the sand. The magnitude of these forces is governed by the preference of the sand to be wet by water, the pore sizes and geometrical shapes, and the interfacial tension between the water and oil. On the macroscopic scale, differences in saturation at the flooding "front" when water displaces oil result in capillary pressure gradients. These gradients cause water to flow preferentially ahead of the front. In short laboratory columns at low rates, the front can span the entire column length. Also, at the outflow boundary the preference of sand to be wetted by water results in retention of water and a high water saturation in the region of the outflow face. This effect is commonly called the boundary effect.' The capillary pressure gradients which complicate the interpretation of flooding performance of short laboratory columns at low rates of water advance become negligibly small under certain conditions. The conditions where capillary pressure gradients are negligible are in long, homogeneous reservoir sands,' at high rates of water advance in short laboratory columns,3 and at any rate in laboratory columns as the residual oil saturation is approached. Thus, laboratory water floods, conducted

Jan 1, 1958

By Ellis Clark

DURING the winter of 1877-78 the Glendon Iron Company, by the advice of the superintendent, Mr. Frank Firmstone, decided to make the experiment of exploding a heavy blast of gunpowder in their limestone quarry at Cedar Hill, Palmer Township, Northampton County, Pennsylvania. The amount of limestone used in the five furnaces of the company is about 60,000 tons per annum, and it was thought that with successful results; this entire amount or more would be thrown down at a single operation, disintegrating the mass to a greater or less extent, and obviating the necessity of blasting and boring the rock from the face of the cliff, both of which operations are slow, and therefore, costly. The rock at the quarry is Auroral limestone, or No. 2 of the old Survey. No fossils have ever been found in the quarry, nor in the immediate vicinity. The nature of the rock varies considerably in

Jan 1, 1879

By Ellis Clark

During the winter of 1877-78 the Glendon Iron Company, by the advice of the superintendent, Mr. Frank Firmstone, decided to make the experiment of exploding a heavy blast of gunpowder in their limestone quarry at Cedar Hill, Palmer Township, Northampton County, Pennsylvania. The amount of limestone used in the five furnaces of the company is about 60,000 tons per annum, and it was thought that with successful results? this entire amount or more would be thrown down at a single operation, disintegrating the mass to a greater or less extent, and obviating the necessity of blasting and boring the rock from the face of the cliff, both of which operations are slow, and therefore, costly. The rock at the quarry is Auroral limestoue, or No. 2 of the old Survey. No fossils have ever been found in the quarry, nor in the immediate vicinity. The nature of the rock varies considerably in

Jan 1, 1879

By Arthur Crowfoot

Page IntRodUction ................... The Round Table in Lake Superior Practice .........420 Early Use of Revolving Round Table in Butte District...... Use oF the Round Table at GREat Falls foR Sand-Slime Feed ., . The Round Table for Fine Slime........,.... Construction of Slime Plant at Great Falls..... '..... 424 Tests on Wood, Linoleum, and Cement Decks.........426 Central Feed Apron Removed ....'......... Re-treatment of Round-Table Tailing........... Determination of Conditions for Round-Table Treatment of Slimcs ... 430 Variation in Slope of Round-Table Deck........ ,... The Steel-Frame Cement-Deck Round Table ........ Tests on Cement and Canvas Dock Surfaces ..: ..... Conoidal Deck Round Tables............. Results with Sand-Slime Feed on Conoidal Deck....... Conclusions from Preliminary Tests on Conoidal and Conical Decks ... 446 Discussion of Results of Four-Day Test on Conical and Conoidal Decks . 452 Discussion of Results of Eight-Day Test.......... Qualitative Sampling of Concentrates Across Conical Deck.... Summary of Slime-Plant Practice............ Suggested Flow Sheet for Slime Classification and Treatment.... Conclusion...................467 Introduction The principal object of this paper is 60 presest, data on the development of the revolving convex round table as a concentrator for the through 0.07-mm. slimes from the ores of the Butte district, although some brief notes on the earliest recorded use of this type of concentrating table in the ore-dressing plants of the Lake Superior region and of the Butte district are also presented. The revolving convex round table belongs to the class of concentrating tables known as film-sizing. tables, these tables using the relative transporting power of a film, or thin sheet of water, as it flows over a quiet inclined surface, to separate the minerals of a sorted product. The grains of heavy mineral move down the slope of the table deck slowly, or, in some cases, not at all, after the initial force of the feed entry VOL. XLIX.—27

Jan 1, 1915

By J. B. Newkirk

IN 1939 Bitter and Kaufmann1 suggested that iron, precipitating from a copper-rich, Cu-Fe solid solution, appears initially as coherent particles of r-Fe which transform to the body-centered-cubic form of iron when the alloy is cold worked. Since then there has been considerable discussion, supported only by indirect evidence, regarding the validity of the concept. For example, Reekie, Hutchison, and Hether-ington2 interpreted the changes in electrical resistance accompanying the aging of Cu-Fe specimens in terms of a coherent 7-Fe precipitate which transformed to the incoherent a-phase during long aging or cold working. Greninger- ound that Cu-Fe alloys which had been water quenched from 1050" and then held at 650°C for 3 hr changed from weakly to strongly ferromagnetic as the aged wire was subsequently cold worked. He also found diffraction lines corresponding to body-centered-cubic iron in Debye-Scherrer patterns given by aged and worked specimens but lines corresponding to only one face-centered-cubic phase in specimens which had been aged but not worked. Knoppwost,' and later Cech and Turnbull,5 found that aged Cu-Fe specimens showed a slight increase in ferromagnet-ism after they had be? cooled in liquid nitrogen. Very recently Denney6 followed the kinetics of the precipitation reaction as indicated by the saturation magnetization, hardness, and diffuse X-ray effects. The experimental results reported by all of the authors mentioned above are readily explained in terms of the Bitter and Kaufmann concept. However, most of the evidence is indirect when used to define the structural changes involved. It was the aim of the present investigation to determine the mechanism of precipitation of iron from a Cu-Fe solid solution in the light of available published information and with additional new and more direct experimental data. Experimental Method At 1060°C copper will contain up to 3 atomic pct Fe in equilibrium solid solution.7 The solvus slopes rapidly toward lower iron concentration, so that at 600°C only about 0.5 pct Fe remains in solution at equilibrium. Below the eutectoid temperature (850°C), the iron-rich phase in equilibrium with the copper-rich solid solution consists of body-centered-cubic a-Fe. Above 850 °C the equilibrium iron-rich phase is face-centered-cubic r-Fe. The alloy to be studied was made by melting electrolytic iron and OFHC copper by induction under vacuum in an Alundum-lined crucible. The metal was held molten for about 5 min, after which time the power was turned off and the crucible was tipped about 70" to promote directional solidification. The resulting ingot, containing 2.5 wt pct Fe by analysis, was clean, large grained, and free of gross segregation. Slices % in. thick were cut from the ingot, rolled to 1/8 in. in thickness, homogenized in hydrogen at 1060°C for 24 hr and, finally, quenched in cold water. Specimens for all subsequent tests were made from these slices. Squares measuring about 1 cm on a side were cut from the slices to make specimens for studying hardness and microstructure. Wires (0.020 in.) for the Debye-Scherrer survey were drawn from 1/8 in. sq rods which had been cut from the homogenized slices. Large crystals for observing diffuse X-ray diffraction effects were prepared by mechanically

Jan 1, 1958

By S. M. Matthews, D. J. Maconochie, L. G. Alexander, V. H. Tillmann

Case studies of the behaviour of large open stopes at the New Broken Hill Consolidated Mine, Broken Hill and the CSA Mine, Cobar, N.S.W. are considered. Deformations were measured by multipoint rod extensometers in sufficient detail to note the phases of rock behaviour, from intact through to rock-fall. In one case readings were obtained from a zone of stress failure in which two bumps, felt as ground tremors, occurred. In this case noise and stress were also monitored. Deformations were analysed in relation to previously measured in situ rock stress, and conclusions drawn about the degree of conformity to, and the areas of departure from, elastic model behaviour. Attempts to describe the growth of instability utilize reduction factors of the apparent modulus, a magnification factor for the apparent Poisson's ratio, and a correlation between progressive noise count and displacement. Monitoring itself is seen as an aid in determiing the final dimensions of stopes and pillars. One large stope, of intermediate dimension 80 m, was mined essentially without change of plan, whereas a change in mining plan was necessary in other stopes. Aspects of interest to mine planners, and areas where futher research is needed, are indicated.

Jan 1, 1981

By C. G. Black

THE purpose of this paper is to present data obtained from an investi-gation conducted on the grindability of coal by the American Society for Testing Materials Tentative Standard ball-mill method. This investiga-tion has been conducted over a period of a year, during which time several hundred tests were run on a wide selection of different coals coming from Pennsylvania, Ohio, West Virginia and Kentucky. The data herewith presented tend to show that the tentative standard ball-mill method might give results that are misleading and that a volume measure might be more indicative of the true grindability 'of materials of varying specific gravity. A means whereby the time element might be reduced has been studied and other phases of this work such as preparation of samples, mechanical screening, reporting results and duplicating tests have been investigated. It is hoped that all criticism offered in this paper will be taken as constructive, with the purpose in mind of perfecting the method now tentative to show the true conditions and of making optional the manner in which certain parts of the test might be conducted to meet diversified laboratory conditions.

Jan 1, 1936

By Thomas L. Wright

Exploration activities were maintained at a high level throughout 1966. Numerous significant discoveries and developments in which geologists played an important part were announced. Although the complete results of exploration activities carried out during the year by private companies have not been announced, the following are among the more important developments that have been made public knowledge. In the western states, exploration for practically all of the metals continued at a high rate. Substantially increased interest in uranium occurred this year, and it is felt by many that a real boom in the demand for uranium may come about in the near future. The reasons have been the more rapid acceptance of atomic power than had been anticipated, and that uranium producers can now sell their product to private interests and even foreign countries. A tremendous demand for uranium is anticipated by many, and this has rekindled exploration activity. On the Colorado Plateau, in Wyoming, and in the area around Grants, N. M., a number of companies have undertaken uranium exploration programs, among which are Kerr-McGee, Homestake, Anaconda and Utah Construction. A new uranium orebody in Texas was brought into production early in 1966 by Susquehanna Western.

Jan 2, 1967

By F. R. Scauzillo

Equilibrium data which should be useful in the design and/or evaluation of glycol dehydration units were prepared from an analysis of various published data and the correlation of these data by the use of the thermo-dynamic equilibrium ratio. The equilibrium ratios of water are used to solve the glycol absorber problem; such solutions are necessary to define the number of trays and the glycol circulation rate needed to meet drying requirements. Activity coefficients were obtained which relate directly to the equilibrium ratios of water in the water-TEG-natural gas system. These activity coefficients have been used to calculate the equilibrium dew points for aqueous TEG concentrations of 60 to 99.9 weight per cent for the temperature range of 40° to 120° F. They also provide a means of calculating equilibrium ratios for water in the water-TEG-natural gas system; this applies to any desired TEG concentration and to the temperature range from 40° to 120°F. INTRODUCTION During the last several years, the drying of natural gas with aqueous triethylene-glycol (TEG) solutions has become very prominent. Most users of TEG as a drying agent have been satisfied with the performance of TEG solutions at the conditions used; however, there always has been some discussion of the drying ability of TEG solutions at conditions not commonly encountered such as temperatures below 50° or 60°F, but more particularly temperatures above 100°F, and pressures above 1,000 psia. Today, when higher wellhead temperatures such as 120°F are more commonly encountered many are skeptical of TEG's ability to dry sufficiently well to provide dew points around 32°F, which is generally the maximum tolerable when attempting to dry a gas to contract specifications of 7 Ib/MMscf. These views probably have evolved to some extent from the days when suppliers would not guarantee dew-point depressions in excess of 65° to 75 °OF. Also, the feelings about TEG drying may have arisen from the lack of information about the equilibrium relation of water in the drying operations. Porter and Reid' have reported equilibrium data for a 95 per cent TEG solution, while Townsend2 reported equilibrium data for 95, 98 and 100 per cent TEG solutions. Townsend also presented a calculational method which obtains activity coefficients in the liquid phase and, subsequently, the equilibrium water content of a saturated gas over glycol from published3 atmospheric dew points. Wise, Puck and Failey' presented activity data for the water-TEG system at atmospheric pressure. In the past, the equilibrium ratios published for water in a 95 per cent by weight aqueous TEG solution have been used indiscriminately by many for all concentrations of TEG encountered in gas drying operations. Since essentially all such gas operations require the use of more concentrated TEG solutions, a study was undertaken to correlate the existing equilibrium data for aqueous TEG and gas systems and to provide some means of calculating the equilibrium ratio of water in the natural gas-water-TEG system where TEG concentrations were other than 95 per cent. The data presented herein consider only the equilibrium drying ability of the TEG solutions and do not consider the effect of temperature and pressure on the tray eficiency of contactors. In other words, this paper is concerned primarily with the development of the equilibrium relationship between water in the dried natural gas and the water in the lean TEG entering the top tray of the absorber. BASIC EQUILIBRIUM RELATIONS A relationship which relates the K value of water in the natural gas-water-TEG system to the vapor pressure of water at the system temperature, the total pressure of the system and the activities of the liquid and gas phases has been evaluated. It is well known that, for any component of a mixture at equilibrium between a gas phase and a liquid phase,

By A. W. Bethune, L. M. Pidgeon

The equilibrium vapor pressure of zinc has been determined over the systems: ZnS(s) + Fe(s) = FeS(s) + Zn (vapor) and ZnS(s) + 2Cu(s) = Cu2S(s) + Zn (vapor) by reacting the components in an evacuated tube containing a thin copper fiber, and allowing equilibrium to be established with respect to the brass formed and the zinc in the vapor phase. The composition of the brass formed was determined and equilibrium vapor pressure values obtained from existing data. Between 850' and 1000°C, values for the first reaction ranged from 8 to 58 mm Hg; for the second reaction from 1.8 to 22 mm Hg. THE direct reduction of metallic sulphides may be indicated by an equation of the form MS + X = XS + M [1] where X is some suitable reducing agent. In the case where M is a metal of relatively high volatility, the use of vacuum will displace the equilibrium to the right at comparatively low temperatures in the face of the usually unfavorable thermochemistry. For this technique to be feasible, MS, X, and XS, must of course be nonvolatile compared to M. In this regard, zinc becomes an obvious metal both from the point of view of its volatility and the fact that most commercial ore deposits of this metal occur as the sulphide, and its direct reduction would avoid the expensive roasting process necessary prior to present day reduction methods. Two reducing agents are of interest, namely copper and iron, with the former having the added attraction of being relatively easily regenerated by oxidation in the copper converter. The possibility of these reactions has been considered before. Imbert1 patented a process whereby zinc sulphide was reduced by either copper or iron. The process as described took place at atmospheric pressure and, at the high temperatures required, the system was molten, resulting in the formation of a matte with the consequent reduction in the activities of the reactants. Peterson2 did further experimental work on these reactions and, although promising results were obtained on a small scale, attempts to increase the size of the furnace led to excessive "blue powder" formation. The early workers failed to realize the large reduction in temperature afforded by the use of vacuum and its desirable results. More recently, the direct reduction of zinc sulphide by iron has been the subject of a thermody-namic investigation by Kelley,3 and Gross and War-rington' have studied the kinetics of the reaction in the temperature range 900" to 1000°C, their experiments being conducted using vacuum and indicating that the reaction would proceed practically to completion in 1 to 3 hr, depending on the temperature. A qualitative examination of the system ZnS-Cu carried out at this University indicated that 98 pct of the theoretical zinc in the charge could be recovered in 1 hr at 1000°C when operating under reduced pressure. The purpose of this research program was to study the equilibrium of the two reactions. During the investigation, reference to the experimental work of Schenk5 was found but, due to lack of detail in the report, it was felt that it would be desirable to continue the equilibrium measurements. Selection of Method The measurement of vapor pressure of metals presents obvious problems resulting from the high temperatures which must be employed. In the present case, the production of the "reaction pressure" introduces a further difficulty since a chemical reaction must proceed before any metal vapor pressure is produced, resulting in depletion of the re-

Jan 1, 1954

By Edward Thomas

ROCK bolting, third great change in postwar underground mining, is inseparably tied to the other two changes: better drilling and mechanized mining. Mechanized mining provided the impetus, when conventional supports restricted maneuver-ability of equipment-while carbide-tipped bits lent the means of drilling required holes cheaply. With the need and the tools at hand development snow- balled. In just six years, from January 1948 to January 1954, some 800 mines adopted bolting for systematic support, and over 100 of these mines now use rock bolts exclusively. Simultaneously, foreign mines have adopted the idea, but to a lesser extent. What held back this major change? The concept of fastening loose material to unbroken and apparently solid material is probably as old as mining itself, and sporadic use has been reported from virtually every mining region in the world. But falls of rock have always been the greatest source of both fatal and nonfatal accidents in underground mining and miners have understandable reluctance to work under roof or back material if they even suspect that it might be hanging like a "sword of Damocles" -supported only by a thin bolt.

Jan 11, 1954

By James M. Link

The design and construction of cross-country pipelines for fluids such as crude oil appears relatively simple compared to the complex problems encountered in slurry systems. Considerable effort has been expended in hydraulic research laboratories in an attempt to improve the understanding of slurry behavior. This effort has been rewarded with considerable success and is best illustrated by the large number of slurry systems now planned or under construction. However, slurry transport in pipelines is still, in many instances, more of an art than a science. In order to minimize the risk factors in the construction and operation of large scale slurry systems, studies are frequently conducted in pilot scale test loops such as the one at the Colorado School of Mines Research Institute. The pilot scale projects are designed to provide the basic engineering data necessary to design slurry transport pipeline systems. Usually three slurry solid concentrations are pumped at various line velocities and optimum slurry densities and velocities are determined. Critical velocities, friction head losses, power requirements, and so forth, are also determined from measurements and calculations. Wear tests are also strongly recommended and anticipated pipe wear rates in inches per million tons of solids reported.

Jan 11, 1972

By Frank E. Shepard

Electric power in mining-operations is now successfully applied to haulage, hoisting, lighting and pumping; and until lately, drilling was the one department of mining in which an electric source of energy had not been introduced. Drilling by electric power has been the field for much investigation and several forms of electric-drills have been tried; but in the severe service of rock-drilling many dieculties have been encountered, and the heavy cost of repairs has caused a deep prejudice against this system of drilling. In the majority of electric rock-drills previously placed on the market, two principal factors have been considered; first, a portable electric motor usually of heavy pattern, coupled to the driving-mechanism of the drill proper by means of a flexible shaft; and second, the coupling of some form of reciprocating cross-head to a piston by means of a spiral spring, the drill-bit being fastened to the piston-rod by some suitable form of chuck with fastening bolts and nuts. In this latter form of drill, the cross-head has a fixed stroke, while the piston with drill-bit attached is allowed a variable stroke through the

Jan 1, 1904

By Carl H. Samans

THE INFORMATION AVAILABLE on the rolling characteristics of the precious metals-gold, silver, the platinum metals and their alloys-is incomplete and mostly from scattered sources. In the present paper an effort has been made to assemble and correlate it and to fill in some of the gaps that exist. GENERAL ROLLING CHARACTERISTICS SOME EFFECTS OF IMPURITIES Gold and its alloys are generally considered to be hot short and hence are usually rolled cold. Cold rolling of the yellow, green, and pink gold alloys. Which customarily contain gold, silver, copper and zinc and frequently some nickel as well, introduces no new problems since reasonable reductions are quite feasible and the alloys show little tendency to fire crack in subsequent annealing. The white gold alloys. which usually contain little or no silver and 10 pct or more nickel, are very susceptible to fire cracking1 and hence wrist he given relatively heavy reductions, i. e., 8-10 pct or more per pass with a total reduction of about 50 pct between anneals, to minimize this tendency. In addition, it is preferable to keep the bar as flat as possible during rolling. Although no comprehensive study appears to have been made of the effects of impurities on the cold rolling characteristics of gold alloys, the observations of Nowack2 on the effects of small

Jan 1, 1948

By E. Goldin, H. J. Juretschke

THE electrical properties of porous conductors have been studied ever since such materials, usually prepared by pressing and sintering of metallic powders, obtained practical importance. In most cases, however, the results have not been easy to interpret because of the great number of independent variables such as powder size, pressure, pressing rate and temperature, subsequent thermal history, porosity, and so on, which enter into the fabrication of industrially desirable materials. In recent years an interpretation of these properties has become of interest because the electrical properties of many new substances, prepared as fine powders by crystallization from the vapor phase or by reactions in the solid state at high temperatures, have to be determined on porous samples formed from the powder. Since theoretically significant information must refer to the fully dense state of the material, it is important to relate the electrical properties measured on such porous samples to those expected for a sample of 100 per cent density. A simple theory for the porosity dependence of the electrical conductivity and the Hall effect was recently proposed by Juretschke, Landauer, and Swanson.' Their model, assuming a distribution of pores of equal size and shape, sufficiently far apart so that each pore is embedded in a region of uni-

Jan 1, 1959

By James R. Jones

The concern for air pollution goes back centuries as will be seen from this quotation: "Strife and coal, it seems, have a hand-in-hand historical relationship. It was thought by some . . . in the Middle Ages that burning coal filled the air with dangerous poisons. So great was the concern that in 1306 King Edward I of England passed the first and unquestionably the harshest, air pollution legislation edict that history will record. His proclamation declared the use of coal an act punishable by death." As related to coal mining the air pollution problem is primarily that of its customer when using the fuel. Thus the major impact relates to markets for coal rather than the actual mining operation itself. In the vicinity of the coal mine the problem is principally related to fugitive dust from roads, transfer facilities, loading facilities, crushers. etc., and particulate matter (dust or fly ash) from thermal dryers and air cleaning tables. FUGITIVE DUST Most state air pollution regulatory agencies now have rules and regulations requiring control of fugitive dust. This refers to dust generated from normal processing operations. A typical air pollution control agency regulation reads as follows: "Fugitive Dust" "No person shall cause, suffer, allow, or permit any material to be handled, transported, or stored; or a building, its appurtenances, or a road to be used, constructed, altered, repaired, or demolished without taking reasonable precautions to prevent particulate matter from becom-

Jan 1, 1973