Search Documents

By W. L. Dennen, W. W. Wirth

Research looking toward the reduction of the cost of roof support by substitution of longer-life materials for wooden timber is fully justified by the fact that roof support is an important element of all production costs. Permanent or semipermanent roof support will reduce the expense of timber-maintenance crews during steady operations, but even more markedly during idle periods. The management, therefore, is faced with the important problem of timber renewals, which in times of regular operation are frequently obscured by more urgent problems of production. Increased use of timber in the Anthracite Region of Pennsylvania is caused mainly by increased percentage of coal obtained from robbing areas, which requires more timber for safety than development work, and maintenance of long haulageways through crushed ground despite the fact that less coal is transported over them. The timber reserve in the immediate vicinity of the mines has been depleted to such an extent that it is necessary to secure 70 per cent of the timber requirements from distant sources. Originally, mine timbering in this region was done by largely utilizing round props or legs with round collars. The whole cross section of the tree from which timber was cut was utilized by forming the joints between the legs and the collars with saw and adze, using plank or round saplings for lagging behind the legs and over the collars to prevent material falling between them. The Mine Inspectors' report of 1898 records an important digression from the use of round timber, when two tunnels at the Babylon colliery, near Pittston, Pa., were timbered with 12 by 12-in. square timber sets with mud sills, through quicksand for distances of 425 and 160 ft., respectively. The timbers were lagged with 3-in. plank to control sand. An early step toward the permanent type of roof support was the installation of "brick pillars or perfect arched brick rooms" instead of

Jan 1, 1940

By A.S. Richardson

AIR conditioning, or air cooling, for the improvement of ventilation in the Butte mines has come into increasing use during the past 10 years. In part, the methods practiced have been described in previous publications of the Institute, but some improvements on earlier methods have been made and a number of new features have been developed. This paper is presented as a record of progress made, and for the sake of completeness describes all general features of the work. The need for air conditioning in the ventilation of mines in the district arises from the fact that the temperature of the ground and mine water has shown a very great increase with increase in mining depth, and has now reached a maximum of slightly over 130°F. The most difficult part of the ventilation problem is the maintenance of temperature and humidity of a satisfactory standard in the working places, especially on the lower levels. Although ordinary ventilation is adequate to maintain good conditions in most of the working places it is subject to a number of limitations at great depth. Most important among these limitations is that with increase in depth the air becomes heated before it reaches the working places, both by compression from increase in atmospheric Pressure and by heat transferred to it from rock at high temPerature, so that its capacity for lowering temperatures is greatly reduced before it reaches the operating zone. Increasing depth of mining also increases the distance traveled by the air in its passage through the mine, and this causes a corresponding increase in resistance to air flow, so that there is greater difficulty in maintaining even the same volume in circulation. Thus, in the face of a demand that the ventilating system have a very much greater capacity to remove heat from the mine, the tendency is for that capacity to diminish. The only evident alternatives were (I) the opening of additional air shafts to increase the volume of air in circulation, (2) an extension of the existing system that would be subject to the same limitations, or (3) the adoption of an entirely different method such as air cooling. Fortunately for an economic solution of the problem, the mean annual temperature of the surface atmosphere at Butte is about 40°F., with very low relative humidity in summer, so that there is unlimited natural cooling power at a temperature range adaptable to air-conditioning methods. Methods Two similar methods of air conditioning are used, as necessitated by service requirements and dependent upon the equipment available. In one, which is the more important and has the greater cooling capacity, water is circulated in a closed circuit, and, alternately, first absorbs heat from warm mine air and then dissipates it in the surface atmosphere by cooling at a cooling tower. The second

Jan 1, 1943

By W. L. Dennen, W. W. Wirth

Research looking toward the reduction of the cost of roof support by substitution of longer-life materials for wooden timber is fully justified by the fact that roof support is an important element of all production costs. Permanent or semipermanent roof support will reduce the expense of timber-maintenance crews during steady operations, but even more markedly during idle periods. The management, therefore, is faced with the important problem of timber renewals, which in times of regular operation are frequently obscured by more urgent problems of production. Increased use of timber in the Anthracite Region of Pennsylvania is caused mainly by increased percentage of coal obtained from robbing areas, which requires more timber for safety than development work, and maintenance of long haulageways through crushed ground despite the fact that less coal is transported over them. The timber reserve in the immediate vicinity of the mines has been depleted to such an extent that it is necessary to secure 70 per cent of the timber requirements from distant sources. Originally, mine timbering in this region was done by largely utilizing round props or legs with round collars. The whole cross section of the tree from which timber was cut was utilized by forming the joints between the legs and the collars with saw and adze, using plank or round saplings for lagging behind the legs and over the collars to prevent material falling between them. The Mine Inspectors' report of 1898 records an important digression from the use of round timber, when two tunnels at the Babylon colliery, near Pittston, Pa., were timbered with 12 by 12-in. square timber sets with mud sills, through quicksand for distances of 425 and 160 ft., respectively. The timbers were lagged with 3-in. plank to control sand. An early step toward the permanent type of roof support was the installation of "brick pillars or perfect arched brick rooms" instead of

Jan 1, 1940

By A. S. Richardson

AIR conditioning, or air cooling, for the improvement of ventilation in the Butte mines has come into increasing use during the past 10 years. In part, the methods practiced have been described in previous publications of the Institute, but some improvements on earlier methods have been made and a number of new features have been developed. This paper is presented as a record of progress made, and for the sake of completeness describes all general features of the work. The need for air conditioning in the ventilation of mines in the district arises from the fact that the temperature of the ground and mine water has shown a very great increase with increase in mining depth, and has now reached a maximum of slightly over 130°F. The most difficult part of the ventilation problem is the maintenance of temperature and humidity of a satisfactory standard in the working places, especially on the lower levels. Although ordinary ventilation is adequate to maintain good conditions in most of the working places it is subject to a number of limitations at great depth. Most important among these limitations is that with increase in depth the air becomes heated before it reaches the working places, both by compression from increase in atmospheric Pressure and by heat transferred to it from rock at high temPerature, so that its capacity for lowering temperatures is greatly reduced before it reaches the operating zone. Increasing depth of mining also increases the distance traveled by the air in its passage through the mine, and this causes a corresponding increase in resistance to air flow, so that there is greater difficulty in maintaining even the same volume in circulation. Thus, in the face of a demand that the ventilating system have a very much greater capacity to remove heat from the mine, the tendency is for that capacity to diminish. The only evident alternatives were (I) the opening of additional air shafts to increase the volume of air in circulation, (2) an extension of the existing system that would be subject to the same limitations, or (3) the adoption of an entirely different method such as air cooling. Fortunately for an economic solution of the problem, the mean annual temperature of the surface atmosphere at Butte is about 40°F., with very low relative humidity in summer, so that there is unlimited natural cooling power at a temperature range adaptable to air-conditioning methods. Methods Two similar methods of air conditioning are used, as necessitated by service requirements and dependent upon the equipment available. In one, which is the more important and has the greater cooling capacity, water is circulated in a closed circuit, and, alternately, first absorbs heat from warm mine air and then dissipates it in the surface atmosphere by cooling at a cooling tower. The second

Jan 1, 1943

By Ernest Burchard

FLUORSPAR is found in most of the states from the Rocky Mountains westward, and commercial production of the mineral has been reported from Arizona, Colorado, Nevada, New Mexico, Utah and Washington. The map in Fig. 1 indicates the general distribution of many of these deposits but it is by no means complete. In the summer of 1926 the writer examined certain deposits of fluor-spar in Arizona, California, Colorado, New Mexico and Washington; in November, 1927, revisited the Jamestown, Colo., district, and in earlier years examined deposits in Colorado and New Mexico. Based on notes of his own and. on descriptions and other data by H. A. Aurand, H. W. Davis, R. B. Ladoo, V. C. Heikes, W. D. Johnston, Jr., and by producers of fluorspar, he prepared the following brief descriptions of deposits and estimates of reserves of fluorspar, originally for the use of the subcommittee on fluorspar of the Joint Committee on Foreign and Domestic Mining Policy and on Industrial Preparedness respectively of the Mining and Metallurgical Society of America and the American Institute of Mining and Metallurgical Engineers. Descriptions of many fluorspar deposits in various western states and districts have been published. It is not feasible to summarize this literature here, but the appended bibliography will indicate to the interested reader what papers are available.

Jan 1, 1933

By Stewart R. Wallace

"For his achievements in unravelling the complex geology of the Climax ore body; for his leadership in the discovery of the Henderson deposit; for his continued encouragement of young geologists; and for his lecture . .."

Jan 1, 1975

By Charles Fulton

The study of the condensation of zinc from its vapor was undertaken to shed light on certain problems encountered in large-scale electric zinc-furnace work recently conducted. It is a matter of common knowledge that one of the disadvantages of the arc type, electric zinc furnace, is the production of a large amount of blue powder and proportionately little liquid spelter, for, as stated by Stansfield,1 "A notable defect in the electric smelting of zinc ores is the difficulty experienced in obtaining the distilled zinc in the liquid state; when zinc ores are smelted electrically, very little liquid metal is commonly obtained, nearly all of the zinc being in the state of powder."

Jan 8, 1918

By H. Van F. Furman

As the cyanide-method for the extraction of gold from ores is extensively used in the United States and elsewhere, and appears destined to prove a factor of increasing importance in the metallurgy of gold, a description of the latest laboratorymethods may prove of interest. The history of the development of the process in the United States has been analogous to that of all new processes. Many failures are to be recorded and a few successes. It is the opinion of the writer that, had the following simple tests been better understood, many of the failures would not have occurred, and we should probably have a larger number of successful plants in operation. While the process is not simple, but requires a high degree of chemical and engineering skill, the determination of the adaptability of an ore to the method is generally not difficult. While the laboratory-results will not always coincide with the actual results obtained in the mill, they will serve as a guide and control on the working of the mill, and mill generally suffice to determine if the ore can be

Jan 1, 1897

By Paul M. Tyler

Mineral raw materials, because they are essential to our industrial prosperity and military strength, must be made available in substantial quantities regardless of cost. Variations in the cost of procuring minerals, as compared with the cost of obtaining other commodities, and changes in the cost of production of different minerals relative to one another, will naturally influence the quantities of a given mineral item that can be marketed readily. However, in the last analysis, the cost of winning minerals from the ground usually constitutes only a small fraction of the value of the end-use products and services derived from them. The miner's share of the cost of a typewriter, telephone circuit, or even a modem office building, is almost insignificant. Far more important to the ultimate consumer, therefore, than any minor saving in cost is the assurance of ample supplies of the minerals needed to aliment our expanding economy. To create a successful metal mining operation involves (1 ) the discovery and systematic development of a mineral deposit, (2) extraction of the ore, (3) the mechanical and metallurgical processing to eliminate worthless or harmful impurities, and (4) the profitable disposal of the product. The fist step of the technological process belongs chiefly in the realm of the geologist, the second is a mining engineer's job, the third is mainly up to the millmen and extractive metallurgists; whereas the fourth and equally important step poses a commercial problem that has aspects in common with the marketing of other products. Ore finding is far from being an exact science. There is no mathematical criterion for evaluating the efficiency of prospecting and exploration. Lady Luck shares the honors or assumes part of the blame along with the prospector and geologist. Marketing like- wise involves factors that seemingly defy engineering analysis. Although the other steps can be measured with some degree of mathematical accuracy, even they tend to vary so widely in basic principle, as well as in

Jan 1, 1964

By F. R. Morral, E. P. Miller

Hot-dipped heat-treated zinc coatings on sheet steel were examined with X-rays. The phases identified were compared with those listed in the modern literature 01 the zinc-iron system. The zeta (FeZn13) phase is shown to correspond to the phase found by Schueler (1925) in heat-treated zinc coatings. An investigation was undertaken to determine the phases present in hot-dipped heat-treated zinc coatings on steel sheets and wire. This kind of coating on wire was studied some years ago by Schuelerl by microscopic and chemical methods. He reported a new phase, FeZn10. Later, Clark and Stillwell,2 using X-ray crystal analysis, identified a new phase in ordinary galva. nized wire, which was assumed to be the FeZn10 phase. Since the extensive review of the iron-zinc alloys presented a few years ago,3 much new work has been published, some of which5-l6 was too late to be included in the recent edition (1939) of the American Society for Metals' Handbook.4 Figs. 1 and 2 are reproductions of the latest iron-zinc diagram proposed by Schramml1 as a result of his investigations by microscopic, thermal, magnetic susceptibility and X-ray methods. Table 1 summarizes all the known published X-ray data of the phases Present. The solubility of iron in zinc has been determined by x-ray methods.10 In the same manner the homogeneity range of the P phase was studiedlo using the principle that the parameter of an intermetallic compound changes while the concentration of One of the constituents changes. Schramm10 has found some 80 alpha lines in X-ray powder photograms of phase d1, and from these he believes that this phase is related to the P phase. Previous investi-

Jan 1, 1941

By Earle E. Schumacher, W. C. Ellis, John F. Eckel

Copper-calcium alloys are of interest as materials for use in deoxidized conductors of high conductivity. That calcium is effective in deoxidizing and degasifying copper is well known. Brandenberg and Wiensl have described the use of calcium in the casting of sound copper and state that the deoxidation can be carried out without difficulty. The castings that they prepared were sound and sufficiently ductile to permit wire drawing. Pratt,2 in British Patent No. 1699 (1907), has claimed the use of calcium for the deoxidation and degasification of copper. Masing3

Jan 1, 1930

By Nicholas J. Grant, Irmgard Rump, Bill C. Giessen

The system W-Hf was determined by use of metal -lographic and X-ray methods. The only interrnetal-lie phase W2Hf melts peritectically at 2650° ± 50°C. A eutectic between W2Hf and ß-Hf solid solution exists at 78 at. pct Hf arul 1930º ± 10°C. The addition of tungsten loulers the hafnium transfornzation; there is a eutectoid at 93 at. pct Hf and 1560°C. The solubility limits of the terminal solid solutions were determined. At the beginning of this investigation, the system had not been elaborated; only crystallographic work had been done to determine the structure of the occurring intermetallic compound W2Hf, and a certain analogy to the system W-Zr was to be expected. Special emphasis was placed in this program on the Hf-rich part of the diagram. Following the completion of our experiments, a phase diagram was suggested by Braun and RUdY.1 EXPERIMENTAL METHODS The investigation utilized tungsten powder supplied by the General Electric Co. with a purity of about 99.9 pct and hafnium crystal bar of about 97.7 pct purity, 2.3 pct Zr, supplied by Foote Mineral Co. Typical analyses are given in Table I. The procedures followed were identical with the ones described for the Re-Nb diagram.' Tungsten powder was compacted at 16,000 psi and the necessary amount of hafnium was added in the form of small pieces cut from the crystal bar, with a reasonable excess of tungsten powder to make up for powder losses on melting. High hafnium or tungsten melts were prepared from premelted tungsten and hafnium or by employing master alloys. The melting was done in a Heraeus arc-furnace under argon. Melting and remelting up to 8 times resulted in fairly homogeneous alloys. No weight

Jan 1, 1962

By Dr. O’Neil Thomas J., Donald W. Gentry

Who steals our gold and silver, and copper, zinc and lead? Who takes the joy all out of life and strikes our high hopes dead? Who never wrote a schedule that to anyone else was clear? The sulphur-belching, miner-welching, smelter engineer. -Anonymous From "The Engineer," Engineering & Mining Journal, Apr. 13, 1918 INTRODUCTION A striking characteristic of publications devoted to the principles of engineering economy and investment analysis is that the revenue side of the equation is generally either ignored entirely or addressed only in a superficial manner. This is understandable to a degree in the general case because methods of revenue estimation are highly dependent upon the specific type of project under consideration and the nature of the market served. An important contributing factor, however, is that developing estimates of future sales prices for most products is a risky activity which is less amenable to credible quantitative modeling than other topics in investment analysis. The specific subset of capital intensive investments addressed in this book- mining projects-is particularly sensitive to projections of mineral prices, many of which are notoriously volatile. Furthermore, the unique nature of mineral markets, prices, and product specifications occupies a major role in mineral project evaluation. Even here, however, authors have tended to offer little assistance to the reader in estimating project revenues. For example, the most popular mining engineering textbook for four decades, Elements of Mining (Lewis and Clark, 1967), contains the following advice on estimating future mineral prices (pp. 359-360): "Since the life of the mine will extend over a number of years the future price of mineral products must be estimated in order to calculate the probable profit to be realized. Current prices may be used, but it is preferable to take the average price for the past 25 to 35 years as it covers definite business cycles. Some engineers believe that a mine should make a small profit if its highest-grade ore is marketed at the minimum price during the past 35 years. Business

Jan 1, 1984

By C. D. King

THIS year the American Institute of Mining and Metallurgical Engineers celebrates its seventy-fifth anniversary as well as the same anniversary of iron and steel in this country as we now know it. The society's span of life comprehends the very beginning and gradual development of the present-day iron and steel industry and its TRANSACTIONS are rich with the trials and achievements of the pioneers in this field. It is difficult to believe that in the first year of the Institute's existence there was produced in this country only 84,000 net tons of ingots, of which only 2000 tons was made by the open-hearth process; that the bessemer process was just barely beginning; that charcoal and anthracite were virtually the only blast-furnace fuels; that Mesabi ores had not been used in blast furnaces, and such pig iron as was then made was produced at a number of small units, each adjacent to its ore and fuel supply. The growth from 84,000 net tons production of steel ingots to 95,500,000 tons in 1945 eloquently tells the story of America's industrial growth.

Jan 1, 1947

By E. P. Miller, F. R. Morral

Hot-dipped heat-treated zinc coatings on sheet steel were examined with X-rays. The phases identified were compared with those listed in the modern literature 01 the zinc-iron system. The zeta (FeZn13) phase is shown to correspond to the phase found by Schueler (1925) in heat-treated zinc coatings. An investigation was undertaken to determine the phases present in hot-dipped heat-treated zinc coatings on steel sheets and wire. This kind of coating on wire was studied some years ago by Schuelerl by microscopic and chemical methods. He reported a new phase, FeZn10. Later, Clark and Stillwell,2 using X-ray crystal analysis, identified a new phase in ordinary galva. nized wire, which was assumed to be the FeZn10 phase. Since the extensive review of the iron-zinc alloys presented a few years ago,3 much new work has been published, some of which5-l6 was too late to be included in the recent edition (1939) of the American Society for Metals' Handbook.4 Figs. 1 and 2 are reproductions of the latest iron-zinc diagram proposed by Schramml1 as a result of his investigations by microscopic, thermal, magnetic susceptibility and X-ray methods. Table 1 summarizes all the known published X-ray data of the phases Present. The solubility of iron in zinc has been determined by x-ray methods.10 In the same manner the homogeneity range of the P phase was studiedlo using the principle that the parameter of an intermetallic compound changes while the concentration of One of the constituents changes. Schramm10 has found some 80 alpha lines in X-ray powder photograms of phase d1, and from these he believes that this phase is related to the P phase. Previous investi-

Jan 1, 1941

MODERN mining is based on drilling--everything else stems from that. U. S. and Canadian mining companies and suppliers of mining equipment are constantly seeking new techniques and tools for increased drilling efficiency. Ultimate goal is increased bit-against-rock time. Just how important their efforts are can be seen through a legitimate extension of available statistics. In Canada some 70 million ft of drilling per year is required. While the number of feet actually drilled in the U. S. is unknown, it is possible to compare U. S. and Canadian mineral production, excluding oil and coal. In the U. S. mineral value was $4200 million and across the border $836 million. Taking into account the number of drilled feet required to produce Canada's total, the U. S. total would be 365 million ft in 1953. A saving of 14 per ft would reduce over- all metal and nonmetal mining costs some $3.65 million per year. This does not take into account other indirect savings. Methods have changed and there have been structural and metallurgical advances in blasthole practice in the last ten years. The Editors of MINING ENGINEERING in the articles on the following pages present the most significant innovations coupled with results in the field. Environment plays an important role in selection of materials and equipment -but while unanimity does not exist throughout the industry in reference to drilling problems, a definite trend is evident. For the story of that trend read the articles on the following pages.

Jan 9, 1954

By John D. Wiebmer

Lignite Development in North Dakota is a "shotgun wedding" according to former state senator Robert L. Stroup-the unwilling groom (North Dakota) is being led to the altar by the nation's demand for increased coal production. The state's attorney general, Allen I. Olson, reacts to the situation this way: "We have no specific coal policy. We plan to keep the whole matter down to a dull roar and drag our feet until we see how we fit into the national energy picture." But despite a state administration labeled as "cautiously negative" toward resource development, North Dakota has experienced a twofold increase in annual lignite production within the last two years. And within the next four years, three more mine additions will double the state's output again.

Jan 8, 1977

By C. H. Mathewson

COPPER and the copper-base solid solutions readily form twin crystals when plastically deformed at a suitably elevated temperature or annealed after cold deformation. In fact, no feature of the microstructure of these materials is more prominent or characteristic than these straight-sided bands or simple lines of division which sometimes come from groups of thin polysynthetic lamellae, penetrating part way or wholly through the parent grain substance, but often divide the grain into a few or perhaps only two crystallographically related parts. Nearly always the bands as seen in the usual microscopic examination of a specimen come into vivid contrast with the adjacent crystalline material owing to the inherent difference in orientation. Bands which under special conditions of orientation cannot be seen with vertically incident light are often visible under oblique illumination and, when this fails, contrasting effects usually may be obtained by using polarized light. There is no longer any doubt that these synthetic banded structures obtained in the ordinary course of working and annealing are due to twinning of the spinel type which was observed long ago in a number of metals crystallizing in the isometric system.1 It has been customary in metallurgical literature to designate these synthetic twins, which grow into prominence during an annealing process, as "annealing twins" without regard to the actual mode of their formation, which is, indeed, obscure and with scant recognition of the fact that prior deformation is essential, no twins having been observed in metal of known unstrained history. This is questionable; especially in view of. the fact that in a number of metals and minerals, reorientation into the twin configuration is known to occur as a result of a simple shearing mechanism along the recognized twinning planes and the

Jan 1, 1930

By A. B. Parsons

NOT every organization on reaching the relatively ripe age of three score and fifteen can say with truth that its purpose and objects remain precisely the same as prescribed by its founding fathers. Of course, constancy of purpose may be something else than unalloyed virtue. It could merely reflect slavish worship of tradition, intellectual stagnation, or sheer inertia. On the other hand, it could establish the fact that the founders were men possessed of broad outlook, of prophetic vision, and of an acute sense of direction. In addition to charting the course with precision, the founders of the A.I.M.E. surely showed a flair for expressing clearly in a few words what others might say obscurely in many words. To quote verbatim from the "call" for the meeting, in 1871, the proposed organization was to have: "two great objectives: "First, the more economical production of the useful minerals and metals. "Second, the greater safety and welfare of those employed in these industries." This text underwent some refining on several subsequent occasions but today the ultimate product, as set forth in the Constitution reads: "to promote the arts and sciences connected with the economic production of the useful minerals and metals and the welfare of those employed in these industries by all lawful means." The original call was dated "Wilkes-Barre, Pa., April, 1871," and was signed by Eckley B. Coxe, of Jeddo, and by R. P. Rothwell and Martin Coryell, both of Wilkes-Barre, each of the three subscribing himself as "mining engineer." The authors proceeded to explain briefly just how it was proposed to achieve these objectives: "In European countries, where the arts of mining and metallurgy have long been the subject of the most careful study, no means have been found so effectual in attaining the end above proposed, as the free interchange of experience among those actually engaged in these industries; and this object has been accomplished mainly through the medium of `Institutes,' `Associations,' or `Societies,' composed of those engaged in these occupations, and by the periodical publication of `essays' or `papers' communicated to such societies by their members. "It must be evident to all practical men that the interchange of the varied experience

Jan 1, 1947

By Henry Rawdon

ONE of the most vital problems in the manufacture of steel at present is the occurrence of the defects that have been popularly termed "snow flakes," "flakes," or "scabs." Particularly is this the problem of many manufacturers who during the past 2 yr. have undertaken large-scale production for the first time. A study of the microstructure of such defective material throws considerable light upon the nature of these defects and is essential before measures may be taken for the elimination of the defects. Flakes do not appear to be found in the plain carbon steels; they have been found, however, in abundance in some of the simple alloy steels that are being used in such vast quantities; viz., nickel steel of the approximate composition, 0.40 carbon and 3.5 per cent. nickel, and in the chrome-nickel type. The present article summarizes the characteristic features of defective steel of the flaky type as they have been found by laboratory study of numerous specimens, and it aims to show the conditions within the metal that are favorable to the occurrence of this type of defect without entering into the details of mill practice (size of ingot, design of molds, rate of cooling, distribution of cooling stresses, etc.), all of which conditions appear to play a role in the production of these defects.

Jan 2, 1919