Search Documents

By B. M. Larsen, W. E. Shenk, T. E. Brower

Shortly after our previous paper on this subject was printed1 we located a source of uncertainty in the results arising from the unexpected fact that hydrogen slowly reduces silica at 1100" C. in presence of iron, even when the iron nowhere touches the silica, although in absence of iron it does not do so. This difficulty has been completely obviated by the use of a small high-frequency furnace, which enables us to heat the specimen for analysis without raising the temperature of the silica vessel to a point at which any appreciable reduction of the silica glass occurs. We now describe this modification of procedure, and present some typical results obtained with it. For any given specimen of steel, the results are entirely definite and reproducible, but their precise significance is still open to some question, as indeed is true of all methods of oxygen determination SO far developed. Further elucidation of this question is to be expected from the cooperative comparison of the several methods now under way under the auspices of the Bureau of Standards at the instance of the Iron and Steel Division of the A.I.M.E. Apparatus The final form of apparatus we have used is identical with that described and illustrated in our previous paper, except for the substitution for the Globar furnace of a small high-frequency furnace actuated by a vacuum tube oscillator2 0f about 1.5 kw. capacity, and for a slight modification of the containing vessel. This transparent silica vessel is illustrated in Fig. 1 of this paper. Its enlarged portion is about 5 cm. in diameter and 13 cm. long. The silica tube for inlet of hydrogen is fused into this bulb and ends beneath the metal "bucket" holding the steel sample. This sample is in the form of fine millings. The "bucket" is suspended by a platinum wire from the cap of Pyrex glass. The high-frequency

Jan 1, 1934

By Clarence E. Jackson, George G. Luther

THE ever increasing array of information concerning the measurement of the effect of the welding process on the properties of a steel is an indication of the tremendous effort that is being expended in this field. The methods that have been considered may be divided into two groups: first, those that measure directly the effect of welding on the ductility of a steel, and, second, those that observe the change in some property, such as the hardness of the heat-affected zone, and assume a direct correlation between this change and the resultant ductility. The nick-bend test is a direct method designed for studying the effect of welding on the ductility of a steel. The test specimen (Fig. I) consists of a bar cut from a plate with a bead weld on the surface. The specimen is prepared with a saw-notch placed so as to restrict deformation to the heat-affected zone under the bead weld when tested as a static bend. Failure is caused by rupture of the low-ductility metal in the heat-affected zone. The angle at maximum load is used as an index of the effect of the welding process on the material. In the development of the nick-bend test considerable scatter was noted in some of the results, although the agreement of duplicate specimens welded at the same time and tested consecutively was excellent. Upon further investigation it was found that the change in ductility was dependent upon the interval of time between the welding operation and the testing of the specimen. For the six steels of Fig. a, the angle at maximum load in four cases was doubled and in one case was tripled. All steels that have been studied show an improvement in the angle of bend for longer intervals between welding and testing. This same behavior has been found in weldability tests using the Navy T-bend

Jan 1, 1945

By G. L. Oldright

Nearly all of the present schemes for treating complex (i. e. lead-silver-zinc-copper) ores are based on the idea that lead holds, and will hold for some time, the strongest economic place from the viewpoint of supply and demand of all the non-ferrous metals. Copper, it is thought, will come back to its own when European affairs are stabilized, although at that time competition from Chile, Peru, and Katanga, in particular, will be more severe than in pre-war days. The future for silver and for zinc is uncertain. New uses are developing for zinc, and the market has remained better than many expected, but the stabilization of world markets will bring in foreign competition instead of relief. The cost of producing zinc from simple zinc ores, by the retort process, will, from the nature of the labor required and the increasing cost of fuel, increase steadily. As a result, the small producers of purely zinc ores around Joplin are shutting down their mines, even with a good market price for zinc; on the other hand, the producer of lead from complex ores, in the Rocky Mountain states, is confident of a profit from the sale of his lead, and is seeking means to make the zinc in his ore pay some part of the cost of treatment. However, the tonnage costs for mining and ore dressing are much higher in the Rocky Mountain states, as may be seen by comparing tax-return statements from the various states. Even before the recent drop in the price of silver, many mines were operating on a very slender margin of profit; labor and supplies cost more. Mining at greater depth has shown most orebodies to grow increasingly more complex, so that improvements in mining and ore-dressing practice have not been sufficient to compensate for the additional expense involved in beneficiating these ores. The smelters have bad to meet the same general economic situation, so they can only give

Jan 1, 1924

By R. Scheffel, R. Washnock, G. Zarate

"The second survey of global copper leaching operations has been completed, the data published in 1998 has been updated. A survey questionnaire was sent to 40 identified copper leach operations around the world including those leach properties still in operation that responded to the 1998 survey. This paper lists the results of 26 operations that responded to the survey. Selected information from the survey is represented in graphical form. INTRODUCTION Copper leaching was first performed by truck dumping huge monolithic stockpiles of ore and flooding the surface with leach solution or lixiviant with little understanding to the parameters that support optimum recovery of the metal. Heap leaching has evolved into a controlled process whereby a complex low grade ore is stacked in shallow lifts (under 10 m in most cases). The ore is usually crushed and agglomerated, conveyor stacked on an engineered containment system (leach pad) and irrigated in a controlled manner. The lixiviant chemistry is designed to extract the optimum amount of metal from the ore. At first glance, heap leaching appears to be simple in nature. In fact, it is a very complex process. A plethora of technologies such as material handling, environmental control, analytical techniques, solution chemistry, hydrology and many others contribute to the design and operation of a heap leach. Heap leaching requires an inter-disciplinary approach between geologists, mining engineers and metallurgists. Many operational factors affect heap leaching. The process must address climatic factors, flexible operation, quality control before and after leaching, physical characteristics of the ore, geology, mineralogy, reagent consumption, solution application rate and methods (wobblers or emitters), particle size, and favorable conditions for bacterial growth and survival. Predicting, troubleshooting, and optimization of leach recovery is a significant challenge when considering the number of variables involved and their interactions The survey updates many of these key operating parameters to the current state of the art. It should provide the reader an excellent benchmarking summary of these factors on a site-by-site basis."

Jan 1, 2016

By Donald P. Brown

[Mr. Brown did not make his speech available for reprint.] Productivity is the Answer - Always Was; Always Will Be When Bill Balaz invited me to speak here this morning, he asked me to examine the three most important issues Consol will face over the coming decade. There are more than three. But the more I thought about that question, the more I realized all our issues come down to only one. As I reviewed the U.S. coal industry over the past ten years, and as I thought ahead into the year2000, one thing stood out. Not markets. Not government regulations. Not record tonnages. But productivity. The recent history of American coal is a tale of productivity improvement. It is a story that needs telling. And understanding. Not just for the good of the coal industry, but for the benefit of the American economy. Americans today do not appreciate the value of productivity growth. I don't say that lightly. As I review recent debate over American industrial competitiveness, as I look at certain legislative proposals, I see disturbing trends. It's not that anyone is against productivity per se. But many people seem to fear the very processes that enhance productivity. Twentieth century America enjoyed unprecedented growth in productivity. And in personal standards- of-living. Those two go together. This century has been one of change. Demographics. Education. And technology. Many new industries-cable television, computer services, telecommunications, for example-have grown from mere dreams to billion- dollar enterprises employing tens-of-thousands. And some older industries have declined. The nature of work has changed-from manual work to know- ledge work. From agriculture, to manufacturing, to services. In the mid-1960s. AT&T employed more than one million people. These were not high-paying jobs: telephone operators, linemen and equipment assemblers. Today, the successor Bell companies and their new competitors employ no more than a few hundred thousand. Because of automation. Because of enormous gains in employee productivity.

Jan 1, 1988

By Alan Morris

The investigation of the hot-working properties of metals and alloys furnishes a problem which has been attacked in many ways. Tensile, impact and hardness tests on heated specimens have furnished interesting data, but in most cases either the tests are difficult to make or the results hard to translate into terms of practical value. Some investigators have used the drop hammer to advantage. It furnishes a rapid and simple method of comparing the plasticity of metals at elevated temperatures. The indications obtained by its use are of value only in so far as their significance is understood and they can be intelligently used to predict the behavior of a given metal under given hot-working conditions. The work reported here was undertaken not only to add something to the existing volume of such data but also to contribute to our understanding of the results. Doerinckel and Trockels1 used cylindrical specimens and determined the work required to reduce the specimen to one-half the original height. Ellis2 studied the effect of constitution on the malleability of steel at high temperature. His method and that of Kent3 were similar to the one used in the present work. The tests described by Kent were made on samples of tin, zinc, aluminum, copper, lead, 70:30 and 60:40 brasses, with and without a small quantity of lead. He concluded that the test would "indicate whether a material can be forged at a given temperature without cracking." This interpretation must be used with caution. While it is probably true within limits, one must consider the severity of the forging operation. Again, it will not apply strictly to forms of hot working other than forging. For instance, an alloy running 61.0 per cent. copper, 3.25 per cent. lead, remainder zinc, will crack badly in the test, yet, it is extruded commercially. When the possibility of hot-working a new alloy is being considered a study of its drop-hammer test should help

Jan 1, 1931

By Bryce Sullivan, Cliff Baratta, Ehsan Alavi, Timothy Dobbs, Lisa Mori

"Soil conditioning is one of the main factors in successful application of EPB machines in tunneling projects, which involves changing the characteristics of the ground in order to make it suitable for the tunneling process. Selection of the type of conditioner mainly depends on soil type, properties of the tunnel boring machine, and most importantly geological condition. Proper EPB tunneling and soil conditioning in ground above water table is challenging. This was encountered in Northgate Link Extension Tunneling Project in Seattle, WA. In order to improve the tunneling operation, a novel algae-based encapsulated oil was used as a conditioner and as a result the operation of the TBM was improved significantly. This paper reviews the traditional soil conditioning measures that were adopted in University Link and Northgate Link projects in Seattle, WA and compares the results with results when using the encapsulated oil additive. INTRODUCTION Soil conditioning agents are used in EPB tunneling to transform the excavated soil into a workable paste with the desired hydrological and mechanical properties. Reducing wear, power consumption, friction, adhesion, and improving the face stability and material flow are some of the benefits of using soil conditioners in EPB tunneling. Soil conditioning is performed by injecting foam, polymer, water, and bentonite to the tunnel face, excavation chamber and screw conveyor. Selection of conditioning agent mainly depends on soil type, geological condition (groundwater and soil permeability) and TBM features (injection points, open or closed cutterhead, type of foam generator, etc). The most widely used soil conditioners are foam and polymer and in some cases due to existing conditions, clay dispersion or anti-wear additives are also used (Milligan 2000, Langmaack 2000). Foam. Foam is created by dispersing air in a surfactant solution. A different combination of surfactant type and foam parameters should be used for different soil types. Laboratory tests on virgin soil should be performed to identify the best surfactant and foam parameters for the specific soil type (Langmaack 2000). The foam parameters can be described as follows:"

Jan 1, 2016

By J. C. Sullivan, W. A. Knoll

The sinking of a new shaft at the Newport mine, Ironwood, Mich., was started in May 1931 and completed on Aug. 3, 1932. During this period, 2665 ft. of shaft in granite was completed, at an average advance of 6 ft. per 24 hr. In Novernber of 1930, experimental work was conducted on 65 ft. of shaft through 22 ft. of overburden where ledge was encountered, and this work convinced the operators that all drilling could be done with vertical holes with the blasting relief to a 4½-in. hole drilled vertically in the center of the cut. The reason for not adopting the conventional V-cut was to get away from damaging the shaft steel. The blasting in a V-cut naturally tends to throw the broken material upward, but with the cut as adopted the relief was in a horizontal direction to a large extent. The scheme of mucking employed made it necessary to keep the steel shaft sets within 50 ft. of the bottom at all times. This could not be done without serious damage with a V-cut when blasting in granite. The cut as drilled also broke 10.83 ft. per round of drilling, which was considerably more than the experience with a V-cut in the same material. The extended cut reduced proportionately the delays for charging, blowing smoke and handling drilling equipment in the shaft. Another advantage was the ease in drilling vertical over inclined holes, and the preservation of the proper spacing of the drill holes at the bottom of the cut. Drilling Air was carried down the shaft in an 8-in. flanged pipe line at a pressure ranging from 95 to 100 Ib. This line was extended to within 100 ft. of the bottom, where a valve and a 4 by 4 by 6-ft. tee was connected to it. To each side of the tee was connected a nipple and elbow, the resulting span of the two elbows being about 4 ft. Lengths of short 3-in. hoses

Jan 1, 1940

By Charles M. Behre

Under the caption "fault," geologists intend to include all mass movements of solid rocks over adjacent rock masses. When these are studied long after their origin, however, circumstances make it possible to recognize as "fault" only formations showing clear evidence of actual movement of one side with respect to the other. Necessarily the chief evidence consists of the offset of a vein, bed, or other key structure. Planes of movement parallel to the bedding, or nearly so, are recognized with difficulty or are overlooked and hence many important faults are wholly unrecorded. Indeed, among standard American references on structural geology, one alone emphasizes the importance of bedding-plane movements and that one only briefly1. For some time the writer, cognizant of this difficulty, has paid special attention to such movements, both as observed in the field and as recorded in the literature. It is believed that enough data are now at hand to justify a short discussion. Its purposes are fivefold. It is desired first to briefly classify and describe at least the more common kinds of bedding-plane faults, and second, to examine the causes and manner of their formation, at least in instances where the subject has not yet been well covered by other investigators. Third, certain by-products of bedding-plane movements are of such conspicuous importance to the economic geologist and mining engineer as to merit mention. Fourth, concrete illustrations should be placed before the reader in order to lend reality and to furnish a basis of comparison with his experience; such illustrations will necessarily be scattered through the text of this paper. They are only in part from the writer's own field observations. The fifth and prime objective of this paper is to direct attention to the great importance of movements on the bedding planes, in the hope that the recognition of such movements and their significance may simplify mining problems.

Jan 1, 1937

By B. D. Thomas

GRAVITY concentration is a general term designating processes for separating and sorting granular material by means of forces that depend on the density, size and shape of the particles. When these forces are applied to the particles the latter are caused to move, those of a given density along one path and those of a different density along another, until ultimately they are sufficiently separated to be removed from the operation of the process. The forces producing this separation are in general complex and, unfortunately, no completely rigorous analysis of them has as yet been devised. The science of the hydrodynamics of viscous fluids deals with the little that is known about the problem. Every observer of nature is familiar with the fact that an object moving in a fluid encounters a force of resistance. We have only to walk against a brisk wind or stir a cup of coffee, or observe the slow fall of a grain of sand in water, to experience directly the fact that such forces exist. The exchange of force between an object and a fluid in which it is moving operates on the fluid as well as on the object. Thus a sailboat may be set in motion by the force exerted by the wind on the sail; but the sail also deflects the wind-furthermore, the water in which the boat floats is set in motion by the force exerted by the boat as it cleaves through the water. The wind is thus enabled to do work on the water through the intermediary of the boat. In general, an object moving through a fluid encounters a force that opposes the motion and also acts to change the motion of the fluid. In gravity concentration we are dealing with this force of resistance acting on the granular particles that are to be separated. Furthermore, the motion induced in the fluid by a particle will in turn affect the motion

Jan 1, 1943

By H. H. Uhlig

IN our study of the mechanism of and the prevention of corrosion in stainless steels, it was considered of fundamental importance to obtain knowledge of the surface structure of such alloys. If corrosion resistance is due to a self-healing oxide layer, which like a paint film protects the underlying metal, it would be obviously relevant were the effort made to make the film less permeable and more adherent; for example, the surface might be expected to respond to an anodizing process, which is found successful in increasing the film thickness and corrosion resistance of aluminum. However, if passivity and corrosion resistance of stainless steels are due to another cause, the attack of the problem would follow another path. One of the most effective techniques for studying passivity and corrosion tendency is the measurement of the electrochemical potential. Not only can one determine by potential measurements whether a metal is active or passive, but also one can determine the degree of passivity and rate of transformation of passivity with time. Chemical media that build up or destroy passivity when in contact with the steel can also be classified by potential measurements. Something can be learned, too, of the effect of alloy additions such as molybdenum to 18-8, known to decrease corrosion of the alloy in chloride solutions. A study of alloys in previous investigations has sometimes included data on the electrochemical potentials. Tammann and Sotter1 measured the electrochemical potentials of alloys of iron-molybdenum and iron-chromium and reported the critical concentration of molybdenum or chromium at which passivity initiates. Strauss2 made similar measure-ments for the iron-chromium system. The electrochemical potential' has also been used to indicate carbide precipitated 18-8. In 18-8, heat-treated to precipitate carbide, active metal exists at the region of the grain boundaries, contrasted with passive metal within the grains, the active metal accounting for a resultant active potential. Several

Jan 1, 1939

By John Marshall

Silverton was the queen city of the western mining towns in the early 1900s. Located high in the San Juan Mountains, the town constantly grew and changed. Yet, it was subject to the vagaries and whims of economics, politics and disasters, natural or otherwise. Breweries, smelters and sawmills serviced Silverton's swelling mining population, which reached several thousand at its peak. Two trains a day ran from Durango to Silverton, in addition to trains running from Silverton over the top of Red Mountain on to Ironton. They ran up Cement Creek to the little town of Gladstone and up the Animas River Valley to Howardsville, Eureka and Animas Forks. During these prosperous times, construction flourished. There were plenty of wooden structures, and many of these stand today. The first brick buildings were built by bricklayer Patrick Stanley in 1877. It took quite a while for the first car to arrive. Almost 28 years passed from the coming of the first train to the arrival of the first car. It was brought over 3,840-m (12,600-ft) Stony Pass from Creede, CO, in an incredible journey retold years later by Louis Wyman. "Dad's daydreams were not the idle musings or the fantasies of a mystic," Wyman said. "They had a way of erupting into reality. He advocated and built good roads," he said. "During the summer of 1910, he was up to his sweatband in a project that took in half the state of Colorado. He envisioned an automobile highway, unheard of at that time, running southwest from Denver through the scenic grandeur of the high Colorado Rockies. The road would traverse a thousand miles or more of the state's finest recreational land finally circling back to Denver. Years later, when all of the county roads had been connected, it became known as 'Colorado's Thousand-Mile Circle Route.' Of course, Silverton and the San Juans were bright stars along the way."

Jan 1, 1997

By H. F. Johnson, C. S. Harloff

The Nichols series system of electrolytic copper refining has successfully maintained its strong competitive position in the copper-refining industry of today; therefore the improvements made in accomplishing this result are of interest. While additional interest would lie in specific comparisons of results obtained in series operation with those in multiple, we have refrained from such a comparison because it can be fair to both only when they are operating under similar conditions on the same grade of materials. Historical The Nichols Copper Co. started a small refinery at Laurel Hill, using its present system, about 1892. The details of the process in its early stage of development were kept strictly secret, so that no information was published or interchange of ideas permitted with the staffs of other copper refineries, where the multiple system was being developed at the same time. However, the fundamentals of the process and type of cell used today differ very little from their earliest form. All operations including loading and unloading of tanks, and all transportation as well, were carried on by hand. The plant remained in this condition with a gradual expansion taking place until the World War forced such a rapid development that little time or thought could be devoted to modernization or mechanical improvement requiring careful design or detailed planning. Considerable progress was made, however. (1) Large refining furnaces were developed. (2) The old expensive air-lift type of circulation was abandoned in favor of the present system. (3) Operating technique was gradually developed to a high point of efficiency. (4) Tank construction and lining were greatly improved, the first concrete tank being installed in 1915. (This tank is still in operating condition.) (5) A new power plant was constructed. (6) Fuel oil was substituted for lump coal on the refining furnaces. (7) Mechanical casting of the finished product was accomplished. During this entire period the plant was particularly fortunate in receiving only high-grade, clean copper bullion coming principally from the Phelps Dodge mines in Arizona. This, together with the lack of

Jan 1, 1934

By R. H. Thurston

THE writer became convinced, many years ago, that the generally accepted values of the coefficient of friction for lubricated surfaces were not applicable to such heavy machinery as he had been called upon, in the course of professional work, to design, to construct, and to operate. Experience frequently seemed to indicate, also, a wide departure, in such cases, from the accepted "laws of friction." In the year 1869, or earlier, he invented an apparatus to redetermine these laws and these coefficients for a wide range of temperatures, pressures and velocities. The construction of the machine was delayed, however, some time, and no experiments were made for several years, when, finally, the construction of the apparatus was commenced in the workshops of the Stevens Institute of Technology, and experiments were begun in the Mechanical Laboratory organized by the writer in connection with the Department of Engineering. These machines have now been in use about five years, and have furnished an immense amount of valuable information. Those now in use are of two styles: one designed and built by the Class of 1877, Figs. 1 and 2; the other a much larger machine, Figs. 3 and 4. The first has been already frequently described,* and a working drawing of the second has been also published.† For convenience, engravings of both are herewith reproduced. In the “'77 machine,” a journal, F, is made on the overhung extremity of a shaft carried in the two bearings, B B'. This journal is grasped by brass boxes which are carried in a pendulum, II H. They are forced against the journal by a screw which compresses a coiled spring with a pressure which is read off on the scale, N H. A weight at the lower end of the arm, at I, gives it the necessary resistance to deflection. The angle of deflection is measured on the * In Scientific American, Railroad Gazette, Jour. Frank. Inst., Johnson's Cyclopaedia, Knight's Mechanical Dictionary, etc. † Railroad Gazette, Jan. 18th, 1878, p. 25.

Jan 1, 1879

By R. C. Allen, Ralph Arnold

The writers have no new system and no new principle of taxation to propose. The general subject of taxation is as old as governments are and as familiar to taxpaying Americans as the general thesis on the inalienable rights of man. We believe, therefore, following the committee of the National Tax Association, that improvement in the general conditions of taxation, including mine taxation, maybe brought about mainly through a better adjustment of known and tried principles and methods of taxing to modern complex forms of property and income, and that not much is to be expected from abandonment of experience for new ways and means, methods and principles, should anything new be discovered, which in our opinion is very doubtful. The committee referred to has constructed the general framework of its Model System of State and Local Taxation1 on familiar forms of taxing, by eliminating some that ' have proved bad, suggesting improvements in others, and adopting the best, leaving plenty of room for the accommodation of the general plan to the varying conditions of taxation in the several states. Unfortunately, the taxation of mines is dismissed by the committee with the statement that the subject has been reassigned for further investigation and report by a special sub-committee, frankly recognizing that the peculiar difficulties of this phase of the subject require special study and investigation. Much may be hoped for from the labor of this sub-committee if the problem is approached from the viewpoint of recommendations already published. In this paper, the writers state their opinion on some of the broader aspects of mine taxation with too little attention to the grounds on which they rest. Contrary to inclination space requirements compel them to resort to summary statements without adequate discussion for a satisfactory presentation of the whole subject. All they can do is to qualify the witnesses and record the testimony. The senior writer was introduced to the practical aspects of the subject of this paper in 1913, when, as State Geologist of Michigan, he was

Jan 1, 1920

By Luís Marcelo Tavares, Juliana Segura

Comminution is one of the most energy consuming stages in a mineral processing plant. This consumption is not only related to the power supplied to equipment, but also to the indirect or embodied energy, mainly associated to materials that are worn during operation, including grinding media and liners. Until recently, preparation of iron ores in Brazil did not use comminution intensively, given that plants mainly produced sinter feed, natural pellet fines, besides lump ore. However, with decreasing ore grades, size reduction now occupies a centre stage in nearly all new plants. Technologies used up to date for processing low-grade iron ores in Brazil, in particular itabirites, have consisted of three or four stages of crushing followed by ball milling. A number of new plants are either being built or are currently being designed that will process the same type of ore, so that engineers are investigating alternative comminution routes. The paper analyses comparatively four comminution routes for processing a particular itabirite ore, many of which using technologies and layouts that have not yet been used in such application. Using data from bench scale and/or pilot-plant tests, the different routes are compared on the basis of sustainability principles in accordance to the Brazilian energy matrix, which is quite particular. It is concluded that if the sustainability criterion is used, then the optimal route would correspond to a circuit that uses HPGR technology with truncated feed followed by ball milling. Given the particular case of itabirite iron ores and specially to the one in the present work and the source of Brazilian energy, it is evident that indirect energy expenditure in comminution plays a significant role in greenhouse gas emissions when compared to direct energy, being the reason for the great attractiveness of HPGR technology. Evidently that these will have to be balanced against CAPEX, OPEX, NPV and other qualitative criteria, which can certainly lead to a different optimal circuit.

Jan 1, 2014

By Henryk Bystron

The underground fire areas are formed as a result of failure of an active fire extinguishing in mines. Such areas bring about a fire hazard for the work safety and for the mining operations. For liquidation of fire areas it is necessary to create conditions under which a possibly small amount of air is flowing to the fire. To achieve this end, isolation methods are used which consist in erection of full stoppings of various types, sealing practically the fire areas. These methods usually fail in oases when the coal seam is thick and the fire area is situated between the intake shaft and the outtake shaft in which a high-pressure fan is in operation. In such oases ventilation methods based on the balance of aerodynamic potentials in fire areas are to be used. For a very long time the isolation and ventilation methods have been developed in the world mining, No sooner than since 1980 the aerodynamic potential has been used in ventilation methods [1,2,6]. So far, the aerodynamic potential was called in different ways and was determined by different formulae which gave its numerical values more or less approximative. Nevertheless, even in situations featuring by a lack of sufficient theoretical bases of the aerodynamic potential the ventilation methods brought considerable profits in the field of safety in mines and of economics in mine ventilation [1-6,9,10]. The increase in the depth of underground mines and their equipment with expensive machines (apparatus) brought about that the Central Mining Institute at Katowice undertook research works which are crowned by the theory of the aerodynamic potential in mine ventilation networks [7]. The use of this theory in the mentioned ventilation methods will increase their effectiveness. Since the theory will be published in the III rd quarter of this year, we cite in the present paper the formulae and relations associated with this theory which are indispensable to present the balance of aerodynamic potentials in the fire areas in their control by ventilation methods.

Jan 1, 1980

By J. C. Sullivan, W. A. Knoll

THE sinking of a new shaft at the Newport mine, Ironwood, Mich., was started in May 1931 and completed on Aug. 3, 1932. During this period, 2665 ft. of shaft in granite was completed, at an average advance of 6 ft. per 24 hr. In November of 1930, experimental work was con- ducted on 65 ft. of shaft through 22 ft. of overburden where ledge was encountered, and this work convinced the operators that all drilling could be done with vertical holes with the blasting relief to a 4%-in. hole drilled vertically in the center of the cut. The reason for not adopting the conventional V-cut was to get away from damaging the shaft steel. The blasting in a V-cut naturally tends to throw the broken material upward, but with the cut as adopted the relief was in a horizontal direction to a large extent. The scheme of mucking employed made it necessary to keep the steel shaft sets within 50 ft. of the bottom at all times. This could not be done without serious damage with a V-cut when blasting in granite. The cut as drilled also broke 10.83 ft. per round of drilling, which was considerably more than the experience with a V-cut in the same material. The extended cut reduced proportionately the delays for charging, blowing smoke and handling drilling equipment in the shaft. Another advantage was the ease in drilling vertical over inclined holes, and the preservation of the proper spacing of the drill holes at the bottom of the cut. DRILLING Air was carried down the shaft in an 8-in. flanged pipe line at a pres- sure ranging from 95 to 100 lb. This line was extended to within 100 ft. of the bottom, where a valve and a 4 by 4 by 6-ft. tee was connected to it. To each side of the tee was connected a nipple and elbow, the resulting span of the two elbows being about 4 ft. Lengths of short 3-in. hoses

Jan 1, 1938

By Leo P. Tarasov

Magnetic torque studies of ferromagnetic single crystals have been carried out in a number of laboratories during the last decade&apos;s2 and some work has been reported on polycrystalline material showing preferred orientation. Goss3 used the method extensively in developing electrical sheet with desirable magnetic properties, but he used it as a control rather than as a means of studying the texture. Bozorth4 made a quantitative correlation of a torque curve he obtained from some cold-rolled iron with the texture as determined from X-rays, but did not extend his studies beyond the one specimen. Other studies, which have been reported from time to time2,5 have also been incomplete in the sense that no effort was made to study a whole series of samples, differing only in degree of cold reduction or in the annealing temperature, in order to ascertain the effect of such treatments on the texture as revealed by torque measurements. It is the purpose of this investigation to make such a study, mainly in order to see how useful the method can be made when used under favorable circumstances and to find what kind of a correlation can be expected between magnetic and X-ray studies of texture. Before proceeding further, it is desirable to say a little about single crystals, so as to make clear the concepts involved in magnetic torque measurements. Magnetic Torque Method It is fairly well known nowadays that single crystals of ferromagnetic substances have directions of easy magnetization and of hard magnetization. In Fig. 1 are reproduced typical magnetization curves for a single crystal of iron, which show that in a < 100 > direction saturation occurs at low fields compared to those required to saturate the same crystal in a <110> or a <111> direction. (The magnetization intensity I is defined by the equation B = H + 4pI.) At fields high enough to

Jan 1, 1939

By G. W. Jarman

The purpose of this paper is to present briefly a description of some of the special methods of separation or concentration, either singly or in combination with others, and to give certain operating data and examples. Explanation of the usual methods of large-production mill treatment, such as flotation or wet tabling, or of chemically treating industrial minerals, is not included in the scope of this paper, although one of these methods might be, in certain instances, augmented by one or more of the special methods that will be enumerated herein. Description of these special methods will be centered on magnetic separators, electrostatic separators and air flotation or air tables. Magnetic Sepaeatohs In general, separation is achieved by exerting upon a particle some kind of force opposed to gravity, either directly or at an angle. For example, in the Wetherill or cross-belt type of magnetic separator some particles are lifted vertically from the others because they have been exposed to a force to which they respond more readily than particles of lesser magnetic susceptibility. Of course, there is a limitation to this vertical rise, for the particle must be of a high enough susceptibility to receive a magnetic force greater than the 980 dynes per gram of gravitational urge. To overcome this limitation, the induction type of magnetic separator was developed, so that it is only necessary to instill, say, 30 to 60 dynes per gram instead of the 080, to cause a deflection away from the vertical in falling, and that deflection can be used advantageously when falling by inserting a dividing knife-edge. The induction magnetic separator (Fig. 1) has become a fairly well known method of concentrating and purifying. For example, abrasive grain was among the materials that did not respond to the previously best known type of magnetic separator, such as the Wetherill type, and the development of the induction magnetic separator in the plant of a

Jan 1, 1942