Search Documents

By Charles Will Wright

Brief descriptions of the occurrence of the various deposits of strategic minerals then known in South America are published in "The Mineral Deposits of South America," by B. L. Miller and J. T. Singewald, 1919; in "Ores and Industry in South America," by H. F. Bain and T. T. Read, 1934; and in many publications on the individual countries. To give a gen.era1 idea of the situation today and possibilities for future output of strategic minerals in several of the countries, the following notes are offered. All tonnages are in metric units.

Jan 1, 1940

By J. Mark Gronseth

The instantaneous shut in pressure often times is not a well defined feature of pressure-time records from in situ stress determinations by hydraulic fracturing. As the applications of in situ stress data become more sophisticated, the grea5er the need for an unambiguous method with which to identify the instantaneous shut in pressure becomes. Controlled experiments suggest that the instantaneous shut in pressure should be equated with the pressure at the inflection point of the pressure-time record following shut in. A method for determining this value is presented. Often times the minimum instantaneous shut in pressure determined after several pressurization cycles is the best estimate of the stress acting perpendicular to the fracture plane.

Jan 1, 1982

By CLYDE M. EYE

THE Sub-province of Benguet is in the North Central part of the Island of Luzon. Baguio, the capital, is situated on a piateau 5000 ft. above sea level, and is the main health resort of the Philippines. It is rapidly becoming the favorite resort for the China Coast as well, and has many miles of beautiful, curving drives with nearly every pine-covered knoll surmounted by a summer home. The United States Army has a recreation post here, known as Camp John Hay, with a well-equipped hospital, and there is a Country Club with a good golf course adjacent. The weather during the winter months and until late spring is ideal. The business center consists mainly of Chinese and Japanese stores, several hotels, and a large public market, in which are displayed all of the vegetables of the temperate zone, which are flown near Baguio, and many tropical and other products brought up from below. This district is reached from the Coastal Plain either by the old Benguet road built in 1904 by the United States Government, or by the Naguilian road, built some years later. The former is now a toll road, with a line of stages operating over it to and from Des Mortes in connection with the government-owned rail- road. Auto travel from Manila is also along this road, the trip from Manila to Baguio requiring about seven hours, following up the great valley north of Manila for nearly 150 miles to the lower end of the Benguet road, and thence to Baguio, 25 miles. This is an interesting, scenic trip; the road is especially famous for the zig zags where it climbs out of the canyon of the Bued River to the plateau. In the September number of the National Geographic Magazine, a fine aerial picture of this road, as well as of other interesting points in various parts of the Philippines, appears. Freight for the district is taken in mainly over the Naguilian road connecting with the railroad at Bauang. This route follows the ridges of the mountain slope with broad vistas and views of the coast.

Jan 1, 1930

By Arthur F. Wendt

The following experiments and researches were originally conducted by Dr. Heinrich Rcessler, chief of the German Gold and Silver Parting Establishment at Frankfort-on-the-Main, for the sole purpose of abating the nuisance created by the discharge into the air of the sulphurous and sulphuric acids generated in the process of parting bullion by sulphuric acid. The results achieved have, however, an important bearing not only on this process, but are of value in the manufacture of sulphuric acid and sulphate of copper from sulphurous gases derived from any source. It has now been in successful operation for a term of years at Dr. Roessler's own works, and has been lately introduced with satisfactory results at the royal mints of Kremnitz and Munich, and the well-known establishment of Johnson Mathey & Co., of London.

Jan 1, 1884

By W. A. Thomas

STEAM is, and doubtless always will be, the basic power in the anthracite industry, either directly applied through engines and pumps or electrically. The rapidity with which electric power is being applied to the mining and preparation of anthracite leaves little doubt as to its utility and economy. There is practically no operation, except possibly the drilling of hard rock, that has not been successfully electrified and the matter of drilling is handled economically with electrically driven compressors and the standard compressed-air drills. Conservation and the seemingly ever-increasing cost of production, justify careful consideration of the possible results of the more extensive use of electric power in the industry. It is not planned to discuss, herein, the relative economies of individual applications but to consider the relative economy and flexibility of steam and electric power. The reports available for the year 1920 indicate a production of slightly over 80,000,000 tons of anthracite, of which 8,843,500 tons were used for power and heating purposes; in other words, over 11 per cent. of the production was used at the mines. Some of this was used to generate electric power at the mines, about 160,000,000 kw-hr., while 150,000,000 kw.-hr. was purchased from the public utility companies. One large producer, who is buying some electric power and generating some, used over 13 per cent. of the production for power and heating at the mines. Another producer, where considerable electric power is generated on the properties, is using less than 9 per cent. of the output for power and heating. One of the largest producers has a fuel consumption of over 15 per cent. of the output, besides which considerable power is purchased. A careful study of the field indicates that steam-operated plants use upwards of 13 per cent. of the production for power and heating, while electrically operated plants use about 1 per cent. for heating; so that, for steam-power purposes at least 12 per cent., or 268.8 lb., are used for power out of each ton produced.

Jan 9, 1921

By Robert T. Pring

IN addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of employees, with a consequent decrease in labor turnover rates. One progressive mining company1 estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination decreases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor. Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flowsheet. Exhaust ventilating systems are now afforded equal care in design and maintenance to that given other machinery more closely related to the process. METHODS OF DUST CONTROL "Dust control" is a general term descriptive of a number of methods used singly or together to prevent particulate atmospheric contamination. These methods are, in order of their desirability, as follows: I. Change of process. 2. Isolation of process. 3. Wet methods. 4. Ventilation. a. Local exhaust ventilation. b. General ventilation. 5. Personal respiratory protection. In ore-concentration plants it is seldom practical to change a process to eliminate the dust it creates It is possible in some cases to isolate a particular dust-producing operation from the rest of the plant, provided that constant attention on the part of the operators is not required. Frequently water is used in fine crushing and fine grinding, primarily to facilitate the processing of the ore and incidentally to allay the dust produced. Wet methods, however, are not feasible in coarse and secondary crushing operations, because of the relatively great volume of water required in instantly wetting each freshly fractured rock surface. Such quantities of water would entail conveying and storage difficulties. Local exhaust ventilation is the most effective and most commonly applied control measure, wherein directional air currents through the zone of dust production draw the contaminants into a duct system. Unfortunately, only a limited amount of reliable information on exhaust ventilation is available.2-5 Of necessity these publications are rather general, being primarily concerned with engineering fundamentals. While many organizations have successfully

Jan 1, 1940

By William R. Webster

In view of the good results which have followed the wide discussion of the rail-specifications of the American Section of the International Association for Testing Materials, I now offer for discussion its specifications for steel forgings and steel castings. It is not necessary to emphasize the importance of reaching definite conclusions on these subjects. Engineers, consumers and manufacturers are alike interested in securing good, reliable, uniform steel. In this connection, I would call particular attention to the important paper read by Mr. C. H. Ridsdale, last September, before the Iron and Steel Institute, as bearing on them; and, for convenience of reference in the discussion, I append the Table in Section VI. of his paper, on a Manifestations, Classified mider Heads of Faults of Different Types. appearing after Treatment by the User, for Tracing their Probable Source."* The discussion of these specifications will be practically a continuation of our former discussions on "The Physics of Steel." We have passed through a period in which the chemical composition of steel has received the greatest prominence; but failures of steel forgings and castings of the best chemical composition have shown that we could not control the quality of the finished product by the chemical composition alone. It must be admitted that differences in the physical properties of the steel, greater than those due to small variations in composition,are produced by heat-treatment, both in connection with the mechanical work of forging and otherwise. The present result is a strong tendency to deem the heat-treatment more important than the chemical composition. I think the mean course is the safer. We should give them equal importance; for we know that to produce the best results me must start with a good

Jan 1, 1903

By S. H. Chauvenet

Jan 1, 1882

By A. Roberts

This paper reviews progress in equipment design and in the techniques applied to mine lighting in Great Britain. The incidence of the disease miner's nystagmus, which was a major source of concern only a few years ago, has now diminished, largely owing to improvements in standards of lighting in mines. The reorganisation of the coal mining industry, involving increasing mech-anisation, together with new safety legislation, has brought about the widespread use of mains electric lighting underground. An account is given of some of the results of research to determine the lighting conditions needed for compliance with the compulsory legal requirement of "sufficient and suitable" general lighting at specific localities in British mines. Some details are given of the techniques applied and the results of recent research in the problem of glare from miners' cap lamps. Of the various factors in the working environment of the miner, it is true to say that lighting is seldom given attention comparable with that devoted to other factors, such as dust, heat and humidity, or atmospheric gas content. No doubt one reason for this lies in the ability of the human eye to adapt itself to low brightness levels. Be that as it may, the fact is that at the turn of the 20th century the miner's working light improved little throughout the centuries during which mining technology has developed. Indeed, in coal mines which encounter a methane explosion hazard, flame safety lamps, with a luminous intensity less than one candle power, were virtually the sole means of lighting during almost the whole of the 19th century. The 20th century has witnessed a substantial improvement in lighting techniques underground in coal and metalliferous mining. In Great Britain the general pattern has been one of standards periodically raised by the implementation of Statutory Regulations imposed under successive hlines Acts, but it is fair to add that the more progressive mining companies usually anticipated the Statutory Regulations, which when they have been put into effect have served to turn into general practice what was already being done at the better mines. In earlier years, official requirements were limited to the specification of approved lamp designs, with stipulated minimum values of luminous intensity and light output, but more recently the necessity of satisfactory maintenance of standards during service has been recognized, and the current regulations not only require that a maintenance organisation should exist, but also specify a maximum permissible depreciation below initial approval standards.'

Jan 1, 1961

By Andrew Meyer

As a producer of gold and platinum, Colombia is most emphatically an important country. Last year it produced 656,000 oz. of gold-twice as much as any other country in South America, in fact accounting for a third of the production of that continent. In platinum, world data for 1941 are not available, but in 1939 Colombia exported 39,000 oz., apparently ranking fourth among the world's producing countries, being exceeded only by Canada, Russia, and the Union of South Africa. Colombia was always a mining country. Centuries before the Conquest, Indians mined gold, copper, silver, salt, and emeralds. The Spaniards simply intensified mining. The Bank of the Republic states that from 1493 to 1940 52,177,427 oz. of gold was produced by Colombia, and official Chocó statistics show that about $60,000,000 worth of platinum was mined between 1908 and 1941. These figures are impressive indeed considering that only rich pockets and surface showings were mined by the ancients.

Jan 1, 1942

By JOHN LANE DYNAN

HE Tonopah Extension property consisted originally of three claims, with an area of 38 acres. In 1902 a shaft, now known as No. 1, was started near the eastern end of the property, close to the Tonopah Mining Co.'s boundary line, in the. andesite cap rock' which covers the ore-bearing formations in the western end of the Tonopah district. A short distance below the 60-ft. level, the orebodies pinched out, although the veins continued. This shaft has not been used since 1916. Before 1910, the production was small, coming mostly from small shoots of high-grade shipping ore. In that : year, the, company started its 30-stamp mill and cyanide plant; the mill was later enlarged to 50 stamps, with a corresponding increase in the cyanide-plant capacity, which brought the capacity of the mill up to 350 .tons per day. The total production of the mine to Oct. 1, 1920, is 871,177 tons of ore, from which was recovered 15,267,216 oz. of silver and 156,241 oz. of gold.' This makes an average recovery per ton of 17.5 oz. silver and 0.179 oz. gold. The average price received for silver since' the beginning of operations is 65.87 c. per oz., and the average value recovered from the ore-'is $15.25. The area of the property has been gradually increased by purchases and consolidations of adjoining ground until it is now 647 acres. A new shaft, known as No. 2, was started in 1912, 1600 ft. west .of No. 1, and in the following year a crosscut on the 750-ft. level of this shaft resulted in the discovery of the. Murray Vein system, from which the greatest prosperity of the mine has come. This vein, with its related veins,

Jan 1, 1921

By A. J. Weinig

IN the accompanying figure consider the classified AB in closed circuit with a ball mill, wherein T = Tonnage of new feed C = Ratio of circulating load Now consider that the circulating load is made up of two portions of ore. One portion is due entirely to the characteristics of the ball mill and the tonnage of new feed impressed on the ball mill. This portion of the circulating load in no way is to be blamed on the characteristics of the classifier and is all composed of oversize. Consider, for illustration, that this portion of the circulating load is handled in the A division of the classifier, assuming that the classifier is divided longitudinally into two divisions by an imaginary line. Because the classifier does not usually make a perfect separation of the undersize, a certain portion of the total circulating load is to be directly blamed on the efficiency of the classifier. Let this portion of the circulating load be considered as being handled in the B division of the classifier. Now if the classifier is operating perfectly (100 per cent efficient), the width due to the B division becomes zero and correspondingly the efficiency of the classifier diminishes as B becomes wider in proportion to A. If E is the mechanical efficiency, then

Jan 1, 1934

By Richard A. Hawkins

O the American coal man, Australian coal mining most appear to have little, if any, influence on American coal-mining practice and to bear little relation to it. Actually, the relationship has been close, for Australian operators have carefully studied American practice by reading American technical publications, by consulting American engineers, and by visits to Ameriean operations. They have leaned heavily on America for their supply of mechanization equipment and many American mining-machinery manufacturers are active in that country, supplying its needs and furnishing technical assistance. Australia's influence on American coal mining has been obscure and probably negligible. However, it seems reasonable to assume that this influence will increase. The wartime development of air transportation will inevitably bring these two countries into much more intimate contact than existed in recent years. American servicemen. many of them former miners and coal-mining technicians, have visited Australian operation, while stationed in that country, have talked with operators and men over there, and undoubt-

Jan 1, 1945

By Robert T. Pring

In addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of employees, with a consequent decrease in labor turnover rates. One progressive mining company' estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination decreases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor, Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flowsheet. Exhaust ventilating systems are now afforded equal care in design and maintenance to that given other machinery more closely related to the Process. Methods of Dust Control "Dust control" is a general term descriptive of a number of methods used singly or together to prevent particulate atmospheric contamination. These methods are: in order .of their desirability, as follows: 1. Change of process. 2. Isolation of process. 3. Wet methods. 4. Ventilation. a. Local exhaust ventilation. b. General ventilation. 5. Personal respiratory protection. In ore-concentration plants it is seldom prac tical to change a process to eliminate the dust it creates It is possible in some cases to isolate a particular dust-producing operation from the rest of the plant, provided that constant attention on the part of the operators is not required. Frequently water is used in fine crushing and fine grinding, primarily to facilitate the processing of the ore and incidentally to allay the dust produced. Wet methods, however, are not feasible in coarse and secondary crushing operations, because of the relatively great volume of water required in instantly wetting each freshly fractured rock surface. Such quantities of water would entail conveying and storage difficulties. Local exhaust ventilation is the most effective and most commonly applied control measure, wherein directional air currents through the zone of dust production draw the contaminants into a duct system. Unfortunately, only a limited amount of reliable information on exhaust ventilation is available.2-5 of necessity these publications are rather general, being primarily concerned with engineering fundamentals. While many organizations have successfully

Jan 1, 1943

By Robert T. Pring

In addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of employees, with a consequent decrease in labor turnover rates. One progressive mining company' estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination decreases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor, Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flowsheet. Exhaust ventilating systems are now afforded equal care in design and maintenance to that given other machinery more closely related to the Process. Methods of Dust Control "Dust control" is a general term descriptive of a number of methods used singly or together to prevent particulate atmospheric contamination. These methods are: in order .of their desirability, as follows: 1. Change of process. 2. Isolation of process. 3. Wet methods. 4. Ventilation. a. Local exhaust ventilation. b. General ventilation. 5. Personal respiratory protection. In ore-concentration plants it is seldom prac tical to change a process to eliminate the dust it creates It is possible in some cases to isolate a particular dust-producing operation from the rest of the plant, provided that constant attention on the part of the operators is not required. Frequently water is used in fine crushing and fine grinding, primarily to facilitate the processing of the ore and incidentally to allay the dust produced. Wet methods, however, are not feasible in coarse and secondary crushing operations, because of the relatively great volume of water required in instantly wetting each freshly fractured rock surface. Such quantities of water would entail conveying and storage difficulties. Local exhaust ventilation is the most effective and most commonly applied control measure, wherein directional air currents through the zone of dust production draw the contaminants into a duct system. Unfortunately, only a limited amount of reliable information on exhaust ventilation is available.2-5 of necessity these publications are rather general, being primarily concerned with engineering fundamentals. While many organizations have successfully

Jan 1, 1943

By R. Bainbridge

THE Consolidated Mining and Smelting CO. of Canada Ltd. has operated a lead smelter at Trail, B. C., for many years. In order to take advantage of metallurgical advances, as well as to improve materials handling methods, this company, commonly known as "Cominco," commenced planning a program of smelter revision and modernization some years ago. The first stage of this program involved the design and construction of a new blast furnace gas cleaning system. The selection of equipment, the design of facilities, and preliminary operating details of this system will be dealt with in this paper. The essential problem was to clean and collect 100 tons of dust daily from 153,000 cfm* (12,225 lb per min) of lead blast furnace gas which varied in temperature from 350º to 1100°F. Because it was desired to collect the dust dry, either a Cottrell or a baghouse cleaning plant was to be selected. Comin-co's many years of experience with both systems provided a background for choosing the most satisfactory installation. All information pertinent to the two methods of dust recovery was carefully investigated, and it was decided to replace the existing equipment with a baghouse. Very briefly, the reasons for this decision were as follows: 1—A baghouse installation would be practical because the SO2 content of the gas was low and corrosion would not be a problem if the baghouse operating temperatures were held sufficiently above the dew point. 2—Variations in the physical characteristics of fume and dust, which are inherent in this blast furnace operation, should not substantially affect the operating efficiency of a baghouse. 3—For the same capital cost, metal losses (stack and water losses) would be appreciably less in a baghouse. 4—A baghouse would be easier to operate, and would not require the use of highly skilled labor. 5—Operating and maintenance costs of a bag-house would be lower. 6—The only available space for reconstruction was relatively small, and not suited to a Cottrell installation. Once the baghouse system was decided upon, detailed design of the installation was begun. Baghouse Design Gas Cooling: Before the required capacity of the baghouse could be determined, the method of cooling the gas to the temperature necessary for bag-house operation had to be chosen. The problem confronting the design engineers was how best to cool 153,000 cfm of gas from a temperature ranging from 350°F to brief peaks of 1100°F, down to 210°F, the maximum safe baghouse inlet temperature. A survey of existing blast furnace gas temperatures in the outlet flue showed that the normal range was as given in Table I. The obvious choices of cooling method were: 1— cool completely by the addition of tempering air; 2—utilize a heat exchanger; 3—cool by radiation; and 4—cool with water spray in conjunction with the admission of tempering air. The advantages and disadvantages of the various cooling methods were: Air Addition: To cool completely by the admission of tempering air involved tremendous volumes, Fig. 1. For example, to cool 1 lb of blast furnace gas at 450°F requires 1.84 lb of air at 80°F or 1.60 lb at 60°F. As it is necessary to design for peak conditions, it can readily be seen that volumes of tempering air in the order of 1,500,000 cfm would have to be handled. Using the normal design figure of 2.5 cu ft per sq ft of bag area, a baghouse installation comprising some 600,000 sq ft of filter cloth would be necessary. Such design requirements would be prohibitive, not only from a standpoint of capital expenditure, but also because of space limitations. Heat Exchanger: The utilization of a heat exchanger was given serious consideration. A horizontal tube unit using air as the medium to cool the required volume of blast furnace gas from 400" to 250°F was investigated. Cooling above 400°F would be done by water spray, and below 250°F by admission of tempering air. The estimated capital cost of such a unit was found to be prohibitive. From an operating standpoint, there was considerable doubt as to whether the soot blowing equipment provided would effectively keep the dust from building up on the tube surface. The performance of heat exchangers operating on dusty gas in other company operations had not been too favorable. Radiation Cooling: Although somewhat cumbersome, gas cooling by radiation from 'trombone' tubes or other similar equipment (cyclones) is employed in many metallurgical operations. Such an installation was also considered. However, calculations showed that an installation much larger than the space available would be required to handle the gas volume involved. For example, to cool 153,000 cfm of blast furnace gas from, say, 600' to 250°F (i.e., remove in the order of 58,500,000 Btu per hr with heat transfer rates varying from 1.1 Btu per sq ft per hr per OF for the higher temperature ranges to 0.88 Btu per sq ft per hr per OF for the lower ranges) would need a cooling area of some 175,000 sq ft.

Jan 1, 1953

By S. F. Shaw

Fox some time it has been more or less recognized within the industry that a scientific control of flowing wells would result in increased production and a greater ultimate recovery of oil. About two years ago it was proposed by the writer that this control should follow principles worked out by him while handling large air-life operations. In the case of wells that had ceased to flow where a large quantity of liquid was present, the use of these principles would result in a large increase of production by using compressed air or gas to flow the well; in the case of a well flowing naturally it would take the form of controlling the gas associated with the oil, resulting either in immediate increase of production or in a reduction of the gas consumed per barrel of oil, and in both cases would result in a greater ultimate recovery from the sand. The Roxana Petroleum Corp., appreciating the advantages to be obtained by a scientific application of the principles of the air lift to oil wells, recently engaged, for a limited time, the services of the writer to work out some of the problems involved. The work was carried out at Braman, Garber and Tonkawa in Oklahoma, and at Oxford in Kansas. Following some suggestions of the writer a well was also equipped by the Roxana company at Smackover by A. S. Field.

Jan 11, 1926

By George Otis Smith

A YEAR ago, ,at the Institute's dinner, I closed my A remarks with the words: "The scientist devotes his life to the advancement of learning; the engineer gives his to the advancement of living." May 1 begin tonight where I left off then and speak first of the distinction between science and engineering? This difference is a difference both in purpose and in method: it is the sharp contrast between theory and practice; it marks the broad gap between dream and attainment. Sometimes it happens that the investigator is also the builder and applies what he discovers, yet the distinction between science and engineering serves to point out the broad dependence of the engineer upon his brother the scientist. You remember .the old - saying that "where there is no vision the people perish" translate this into modern experience and we may say that "where there is no science, the engineer fails."

Jan 1, 1929

By Larry A. Shiprnan

DEMANDS upon power plants by the war program in 1941 intensified problems of coal utilization. It was an outstanding year in that field. The domestic heating stove witnessed outstanding development; the research folks progressing so rapidly that the design of the "perfect" stove is just around the corner. Use of colored motion pictures in analyzing fuel-bed performances has reached a new high with the colored pictures taken at minute intervals and projected at sixteen frames a second as shown by the Koppers Coal Co. and the Anthracite Institute (on domestic stokers) and the Consolidated Edison Co. (industrial stokers). Continued efforts of this kind will be beneficial in analyzing further some of the "Code for Testing Coal" problems confronting Subcommittee No. 2 of the Joint A. I. M. E. - A. S. M. E. Committees.

Jan 1, 1942

By Tegner C. Johnson

Just a few years ago, my company was referred to as the Marion Steam Shovel Company. Though we still make shovels, both two and eight-crawler types, the eight-crawler stripping shovel appears to have been replaced by the walking dragline for overburden removal and in some cases for the mineral as well. The walking dragline appeared in the coal fields in the early 1930's. It is popular because it can cope with overburden depths in excess of 100 ft and with blasted sedimentary rock, all at an O & O (ownership and operational) cost of ±10[c] per bank cu yd (bcy).

Jan 10, 1974