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By PAUL P. ZElGLER

Rapid growth of the aluminum industry continued through 1948 with an acute shortage of the metal in all forms marking the year. Estimates based on shipments made during the first nine months indicate that, in 1948, the industry shipped more than two billion pounds of aluminum products or roughly four times the amount shipped in the greatest peacetime year prior to the war. The rapid expansion of the aluminum industry is particularly reflected in the production of sheet. Last year, the industry as a whole shipped an estimated 40 per cent more sheet than was produced in the peak war year of 1944.

Jan 1, 1949

By P. H. Dudley

I HAVE taken the liberty of calling the researches herein mentioned industrial, to distinguish them from those strictly scientific, where every known appliance is used to insure accuracy in determining principles. The industrial researches are made to ascertain wherein we have failed to embody, in practice, the principles which have been fully demonstrated by the more purely scientific investigations. So far the researches have been mostly confined to the conditions of combustion as used in locomotive furnaces, although we have examined, to some extent, furnaces under marine and stationary boilers. The products of complete combustion are gases, and, knowing what we should have, it is at once shown by analyzing the products whether the desired reactions are taking place. In spite of imperfect furnaces, lack of system in the arrangement of grate-bars and exhaust nozzles, the results are not altogether vitiated, because the analyses are not closer than one-tenth of one per cent., as under the present conditions it is hardly possible to collect gas exactly under the same conditions at different times. All of our industrial operations have developed in the past few years so rapidly, nearly all of them paying, that, until within the past three years, comparatively little attention has been given to their economy outside of the profession. Great corporations have not asked and considered the question in earnest, can we utilize our heat so as to produce the same effect at less cost? The applications of heat are so extensive, entering into every branch of industry, the principal power used to carry on metallurgical processes, to conduct transportation, that its economical generation becomes of universal importance; in fact, its economical generation and application is the leading industrial question of the day. It is stated by those who have given the subject much attention, that in our best steam-engines not over 10 per cent of the theoretical value of the fuel is utilized, and upon locomotives it is far less, probably not exceeding under the most favorable circumstances 5 or 6 per cent. In recent experiments made with the dynagraph, in drawing trains upon the Lake Shore and Michigan Southern Railway from Cleveland to Erie, 95i miles, we found the force required to draw a stock train of 709 tons to be 2,498,396,320 foot-pounds, exclusive of the force to move the locomotive itself. We

Jan 1, 1876

By G. Sachs, Jr. Brown W. F., Ebert L. J.

It is a generally recognized fact that a steel quenched from the austenitic range and tempered to yield a structure composed of tempered martensite becomes increasingly more ductile with increasing tempering temperature. However, the conventional tensile test fails to yield any value that is sensitive to differences in behavior on tempering among the various low-alloy steels or among different heats of a particular steel. The notched impact bending test, on the other hand, has been recognized for a considerable length of time as capable of revealing differences in impact properties among various steels tempered to 'the same strength level (i.e., the same tensile strength in a conventional tensile test). However, this test is very complex and its significance has not been clarified up to the present time. Of its three characteristic features—the high speed, the notch, and the bending—the notch has been found by Davidenkov2 to be the most potent embrittling factor. Recent investigations on low-alloy steels have shown static notch-bar tensile tests to be more lucid and to evaluate the metal properties in much the same manner as impact tests. In an attempt to analyze the fundamental nature of this test, it was found possible to separate the effects of the two basic characteristics of the stress pattern introduced by the presence of a circumferential notch, the stress state and the high initial stress concentration at the notch bottom. The major conclusions drawn from these previous investigations were as follows: I. The magnitude of the triaxiality at fracture depends primarily on the initial notch depth. Its effect is a great reduction in the average ductility (contraction in area at fracture in the notched section) as compared with that observed in uniaxial tension. This triaxial stress state occurs at a point in the interior of the notch specimen. It determines the notch ductility if the notch is mild and/or the metal possesses a considerable ductility. On the contrary, brittle specimens probably fracture on the metal surface (at the notch bottom) at which point biaxial stress state is present. This biaxiality also considerably reduces the ductility of the metal. For small notch ductilities the notch strength and the notch ductility become very sensitive to embrittling factors. This is contrary to the behavior. of the ductility values derived from a conventional tensile test, which are comparatively insensitive.

Jan 1, 1947

By Ebert L. J., G. Sachs, Jr. Brown W. F.

It is a generally recognized fact that a steel quenched from the austenitic range and tempered to yield a structure composed of tempered martensite becomes increasingly more ductile with increasing tempering temperature. However, the conventional tensile test fails to yield any value that is sensitive to differences in behavior on tempering among the various low-alloy steels or among different heats of a particular steel. The notched impact bending test, on the other hand, has been recognized for a considerable length of time as capable of revealing differences in impact properties among various steels tempered to 'the same strength level (i.e., the same tensile strength in a conventional tensile test). However, this test is very complex and its significance has not been clarified up to the present time. Of its three characteristic features—the high speed, the notch, and the bending—the notch has been found by Davidenkov2 to be the most potent embrittling factor. Recent investigations on low-alloy steels have shown static notch-bar tensile tests to be more lucid and to evaluate the metal properties in much the same manner as impact tests. In an attempt to analyze the fundamental nature of this test, it was found possible to separate the effects of the two basic characteristics of the stress pattern introduced by the presence of a circumferential notch, the stress state and the high initial stress concentration at the notch bottom. The major conclusions drawn from these previous investigations were as follows: I. The magnitude of the triaxiality at fracture depends primarily on the initial notch depth. Its effect is a great reduction in the average ductility (contraction in area at fracture in the notched section) as compared with that observed in uniaxial tension. This triaxial stress state occurs at a point in the interior of the notch specimen. It determines the notch ductility if the notch is mild and/or the metal possesses a considerable ductility. On the contrary, brittle specimens probably fracture on the metal surface (at the notch bottom) at which point biaxial stress state is present. This biaxiality also considerably reduces the ductility of the metal. For small notch ductilities the notch strength and the notch ductility become very sensitive to embrittling factors. This is contrary to the behavior. of the ductility values derived from a conventional tensile test, which are comparatively insensitive.

Jan 1, 1947

By C. W. Stratford

[During the last few years, the necessity for development work has been generally recognized by executives throughout the oil industry, resulting in greatly accelerated progress and the adoption of many noteworthy improvements in refining methods and equipment. Several years ago, the Associated Oil Co. decided to improve distillation methods with the object of reducing refining costs. This extremely interesting work was entrusted to the writer, and W. S. James, now Chief of Research for Studebaker Corpn. of America, was selected as the principal collaborator. The latter contributed much during his two years with the Associated Oil Co., to the development work that has followed. The writer extends to the Associated Oil Co. his appreciation for permission to disclose the details of distilling equipment. In petroleum refining the principal requisites of good economics are the separation of high-priced distillates from those of lower price; maxi-mum yield of any desired distillate; lowest capital investment in refining equipment; lowest cost of operation and maintenance, and the best adaptability and flexibility of the same refinery equipment for handling crudes of widely varying characteristics. The first two items mentioned, separation and yields of distillates are determined by efficiency of fractionating equipment,. Discussion in this paper is chiefly concerned with oil-heating equipment, combustion and furl economy. It has long been well known that velocity plays a very important part in all heat transfer systems. Any betterment in specific transfer. rates in such systems must. always involve velocity. Realizing this fact, IV decided to adopt as a basic principle, the employment of energy to impart velocity required for high transfer rates through a heating diaphragm, and our method of modernizing obsolete shell stills is founded on this principle. Mechanical energy is usually cheap and its rational rspcntliture is returned in the form of greatly increased heat transfer rates, on both oil and gas sides of the sheet. Certainly there is nothing new in this principle, the only novelty being that of our peculiar method of application On the oil side (Fig. I) use is made of a centrifugal pump to jet the oil against the heated sheet thereby creating a high velocity sheet flow over the entire fired area. Such a pump is one of the most efficient machines, so far developed, for moving fluids. 'I'he oil, under pressure impinging

Jan 1, 1928

By W. C. Williamson, J. L. Shugert

DUST control is receiving considerable attention today by most companies as is evidenced by the many articles, papers, and books written on the subject. ~~~t of the larger mining companies have given this subject close study and have established standardized methods of control. W. C. WILLIAMSON and J. L. SHUGERT, Members AIME, are Assistant Ventilation Engineers, Anaconda Copper Mining Co., Butte, Mont. San Francisco Meeting, February 1949. TP 2705 A. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Jan. 17, 1949. Permissible Limits: The question of permissible dust limits has been considered by medical commit-ties and various national conferences. Dr. Lanza, of the Metropolitan Life Insurance Company, Dr. Le-roy U. Gardner, of the Saranac Laboratory for the study of Tuberculosis, and Dr. Pancoast, of the University of Pennsylvania, have been members of these committees. A statement included in reports of some of these committees is as follows: Concentrations to which the dust must be induced in order to be safe have not been absolutely determined. There is evidence that a concentration of more than five million particles per cubic foot of a highly siliceous dust is dangerous. Therefore, it may be stated that it is desirable to avoid counts of more than five million particles of dust containing free silica to a high percent in working places. Table I gives the safe limits adopted by several state industrial codes. Table I. Safe Limits of Dust Concentration Limit Million Particles State Per Cu Ft Cal~fornia Silica (less rhdn 10 pct) 50 Silica (10 pct to 50 pcr) 10 Sllica (more than 50 pct) 5 New York Frcc silica less than 10 pet by weight of rock formation 100 Frec silica more than 10 Pct by weight of rock formation 10 Oregon Silica (over 40 pct) 5 Silica (20 to 40 pct) 10 Silica (10 to 20 pet) 20 Wisconsin 15 million particles, under 10 nicrons in longest dimension per cu ft of air, when the quartz content of the dust is 35 pct, variations in free silica content will make proportional inverse changer in this standard Close attention to dust concentrations has been given to mining operations, since these operations are frequently carried on at considerable distances

Jan 1, 1951

By J. L. Shugert, W. C. Williamson

DUST control is receiving considerable attention today by most companies as is evidenced by the many articles, papers, and books written on the subject. ~~~t of the larger mining companies have given this subject close study and have established standardized methods of control. W. C. WILLIAMSON and J. L. SHUGERT, Members AIME, are Assistant Ventilation Engineers, Anaconda Copper Mining Co., Butte, Mont. San Francisco Meeting, February 1949. TP 2705 A. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Jan. 17, 1949. Permissible Limits: The question of permissible dust limits has been considered by medical commit-ties and various national conferences. Dr. Lanza, of the Metropolitan Life Insurance Company, Dr. Le-roy U. Gardner, of the Saranac Laboratory for the study of Tuberculosis, and Dr. Pancoast, of the University of Pennsylvania, have been members of these committees. A statement included in reports of some of these committees is as follows: Concentrations to which the dust must be induced in order to be safe have not been absolutely determined. There is evidence that a concentration of more than five million particles per cubic foot of a highly siliceous dust is dangerous. Therefore, it may be stated that it is desirable to avoid counts of more than five million particles of dust containing free silica to a high percent in working places. Table I gives the safe limits adopted by several state industrial codes. Table I. Safe Limits of Dust Concentration Limit Million Particles State Per Cu Ft Cal~fornia Silica (less rhdn 10 pct) 50 Silica (10 pct to 50 pcr) 10 Sllica (more than 50 pct) 5 New York Frcc silica less than 10 pet by weight of rock formation 100 Frec silica more than 10 Pct by weight of rock formation 10 Oregon Silica (over 40 pct) 5 Silica (20 to 40 pct) 10 Silica (10 to 20 pet) 20 Wisconsin 15 million particles, under 10 nicrons in longest dimension per cu ft of air, when the quartz content of the dust is 35 pct, variations in free silica content will make proportional inverse changer in this standard Close attention to dust concentrations has been given to mining operations, since these operations are frequently carried on at considerable distances

Jan 1, 1951

By C. K. Leith

QUOTING from Dr. Richard T. Ely:1 "Conservation, narrowly and strictly considered, means the preservation in unimpaired efficiency of the resources of the earth; or in a condition so nearly unimpaired as the nature of the case, or Wise exhaustion, admits. And broadly considered, it means more than the word itself implies, for it naturally includes an examination of methods Whereby the natural inheritance of the human race may be improved; and still more broadly considered, and as used in popular discussion, it includes a treatment of the effects of productive conservation methods upon distribution. "Conservation means a sacrifice of the present generation to the future generations Whenever it is carried too far. There is a sharp limit to the economic sacrifice that we may reasonably ask the private person to make for even the present Welfare, and the limit is still sharper when we come to consider the interests of future generations." In a paper on the iron ores of America, presented to the Pan-American Scientific Congress at Washington, I have emphasized the fact that the reserves of iron ores in the two Americas are enormously in excess of the requirements of the present generation, in fact, so large that no shortage is to be anticipated for many generations in the future; that a large part of the value of iron ores is put into them by man's efforts to make them available. This fact is fundamental for the intelligent consideration of- policies of conservation as applied to iron ore. As I interpret it, this fact makes it practically unnecessary that the present generation should make any especial sacrifice for future generations in the way of conservation of its iron-ore resources. Even if we were disposed to look forward to a period of 100 or 200 years, with a view to insuring the welfare of the people living at that time, it is doubtful whether any procedure we could now formulate would materially help them in the matter of iron ores, so large are the reserves available. In order that an appeal for conservation may be effective it must obviously favor the welfare of the present or immediately following generations; it must promise benefits to general and individual welfare during a period within the range of comprehension of the average man.

Jan 2, 1916

By C. K. Leith

Conservation, narrowly and strictly considered, means the preservation in unimpaired efficiency of the resources of the earth; or in a condition so nearly unimpaired as the nature of the case, or wise exhaustion, admits. And broadly considered, it means more than the word itself implies, for it naturally includes an examination of methods whereby the natural inheritance of the human race may be improved; and still more broadly considered. and as used in popular discussion, it includes a treatment of the effects of productive conservation methods upon distribution. "Conservation means a sacrifice of the present generation to the future generations whenever it is carried too far. There is a sharp limit to the economic sacrifice that we may reasonably ask the private person to make for even the present welfare, and the limit is still sharper when we come to consider the interests of future generations." In a paper on the iron ores of America, presented to the Pan-American Scientific Congress at Washington, I have emphasized the fact that the reserves of iron ores in the two Americas are enormously in excess of the requirements of the present generation, in fact, so large that no shortage is to be anticipated for many generations in the future; that a large part of the value of iron ores is put into them by man's efforts to make them available. This fact is fundamental for the intelligent consideration of policies of conservation as applied to iron ore. As I interpret it, this fact makes it practically unnecessary that the present generation should make any especial sacrifice for future generations in the way of conservation of its iron-ore resources. Even if we were disposed to look forward to a period of 100 or 200 years, with a view to insuring the welfare of the people living at that time, it is doubtful whether any procedure we could now formulate would materially help them in the matter of iron ores, so large are the reserves available. In order that an appeal for conservation may be effective it must obviously favor the welfare of the present or immediately following generations; it must promise benefits to general and individual welfare during a period within the range of comprehension of the average man.

Jan 1, 1916

By Paul F. Sikora, John W. Weeton, Philip A. Clarkin

Effects of variations in carbon content and micro-structure on the stress-rupture properties of a liquid-phase-sirztered, Izeut-resistunt alloy were studied. Using the powder rnetallurgy technique, specimens could be produced having stress-rupture profierties equivalent to or better than those of the alloy in wrought form. In addition, sintered specimens were easily hot worked even when carbon contents were as high as I pct. Correlations between stress-rupture properties and micro structure were obtained in some cases. IT is well known that many alloys used in high-temperature service are quite complex both from the standpoint of chemical composition and microstruc-ture. During the development of these alloys their complexity has in some cases led to treatment schedules which, while practical, often do not fully utilize available alloying elements. For example, in some alloys, massive carbides that form during ingot practice may never be dissolved by reasonable solution treatments and therefore are unavailable for subsequent precipitation hardening, Ref. 1. This investigation was undertaken to determine whether the powder metallurgy method of consolidation might provide distinct advantages over the conventional melting method. First, segregation of alloying elements might be eliminated or reduced and thus a more efficient use of these elements obtained. Second, the structures produced in powder specimens might differ considerably from those normally seen in castings, which would perhaps result in better response to subsequent mechanical or thermal treatments. If these results could be achieved, it was felt that both forgeability and stress-rupture properties might be improved. The alloy used in this investigation was S-816 produced by powder metallurgy methods. The influence of carbon content over the range of 0.1 to 1.0 wt pct was studied for the alloy in the as-sintered condition and after three additional treatments involving heat treatment, hot swaging, and combinations thereof. EXPERIMENTAL Standard S-816 has the composition shown in Table I. It is a cobalt-base alloy having a nominal carbon content of 0.4 pct and is classified as a precipitation-hardening alloy. This alloy was chosen because it is representative of a class of heat-resistant alloys and because adequate information was available concerning its response to various treatments and its subsequent properties. For this study, -100 mesh alloy powder having essentially the same composition as shown in Table I but without the 0.4 pct C was used. Desired carbon variations, achieved by wet mixing the alloy powder with graphite, ranged from 0.1 to 1.0 wt pct. Specimens were hydrostatically pressed and then sintered in vacuum by slowly heating until incipient melting was observed. Sintering this way gave a liquid phase in the interstices of the powder particles and achieved reasonably high densities. The average density of as-sintered specimens was about 95 pct of wrought alloy density. In order to obtain various microstructures, some specimens were heat treated (solution treated for 24 hr at 2150°F, water quenched; aged 16 hr at 1400°F, air cooled); others were hot swaged at 2150 o F (50 pct reduction in area), while still others were hot swaged (50 pct reduction in area) and then given the above heat treatment. During hot swaging it was observed that forgeability was quite good even when specimens contained as much as 1.0 pct C. Specimens were evaluated by stress-rupture test-

Jan 1, 1962

By E. P. Jennings

(Read at the Amenia Meeting, October, 1877.) THE abundance and value of the tellurium minerals of Colorado is well known, but, as yet, few analyses have been made of them, and I offer these as a small contribution to the chemistry of these valuable ores. 1. Native Tellurium.-The specimens from which the analyses of this mineral were made are from the "John Jay" Mine, Boulder County, Colorado, where it occurs in quite large masses, though mixed with more or less silica and iron pyrites. It is usually a fine¬grained, tin-white mineral, but sometimes occurs in distorted, hexag¬onal prisms in cavities in the quartz. Before the blowpipe it gives the reactions for tellurium, sulphur and iron; by cupellation, it yields a small amount of gold. An analysis of a coarsely crystallized speci¬men gave the following results

Jan 1, 1878

By P. A. Vukmanic, M. Gensamer

Only recently has it been realized that preferred orientations are common in hot-rolled steels. In a recent paper, N. P. Gossl stated that hot-rolled mild steel exhibits a texture different from that characteristic of cold-rolled steel. No complete study of these hot-rolling textures has been reported using the pole-figure method of Wever. The material used in the work reported in this paper was the same material used by Gensamer and Mehl2 in a recent study of preferred orientations in cold-rolled steel, to which reference may be made for the composition and thermal history of the steel. Automobile-body sheet bar 1/4 in. thick was hot-rolled at two temperatures, 780' and 910' C. (1436' and 1669' F.). These temperatures refer to the temperature of the furnace in which the steel was heated; after each pass the steel was returned to the furnace and held there long enough to return to temperature. Although no accurate method was used to measure the temperature after each pass, it was estimated by color that only a slight drop in temperature occurred. In order to determine the effect of any preferred orientation that might have persisted through the normalizing treatment, one specimen at each temperature was rolled in the same direction as the original working direction and the other at right angles to it. The total reduction in each case was 85 per cent, the specimens having been reduced from 0.250 to 0.0375 in. in five passes. Final cooling was in air. Pinhole reflection photograms were taken of all four specimens, with the rolling direction vertical and the X-ray beam at an angle of 7' with the transverse direction (the transverse direction is defined as that direction in the rolling plane perpendicular to the rolling direction). These photograms, taken with a Mo target at 35 kv., are reproduced in Figs. 1, 2, 3 and 4. They show that a more pronounced texture was developed by the low-temperature rolling (780' C.), and that of the two

Jan 1, 1937

Edward Payson Mathewson EDWARD PAYSON MATHEWSON, President of the American Institute of Mining and Metallurgi-cal Engineers, was born in Montreal, Canada, Oct. 16, 1864, of Scotch-Irish ancestors. After preparation in private and public schools, he graduated from McGill University with the degree of Bachelor of Applied Science, in 1885, having specialized in mining engineer-ing and metallurgy. He spent the succeeding summer as a surveyor with the Canadian Geological Survey, being employed in the lake region of Ontario. The following spring he left Canada for Colorado, where he immediately obtained a position as assayer with the Pueblo Smelting & Refining Co. Within three years he became superintendent of the plant, and his success in this position brought him to the attention of the Guggenheim family, whose employ he entered in 1897. He was first in charge of their Pueblo plant, but was soon transferred to their refinery at Perth Amboy, N. J. During the succeeding five years he was in charge of important smelting operations conducted by the firm in Mexico and South America. In June, 1902, Mr. Mathewson accepted a position at the Washoe reduction works at Anaconda, soon thereafter becoming manager of the property. It is unnecessary to recount the improvements and enlarge-ments instituted at that plant under his management, until it became the Mecca of all metallurgists visiting the United States. The esteem in which Mr. Mathew-son was held, not only by the men directly under him, but by all his fellow citizens, was expressed in a send-off such as probably no other plant manager has ever received, when he left Anaconda in October, 1916, to accept the general managership of the British America Nickel Corporation, at Nickelton, Ont., Canada. Soon thereafter Mr. Mathewson accepted an appoint-ment as director of the American Smelting and Refining Co., acting as consulting metallurgist for the company and its subsidiaries. In November, 1919, he resigned this position and opened an office in New York City as a consulting metallurgist.

Jan 3, 1923

By S. J. Leach

The possible solution of some of the problems raised in H. L. Hartman's article "Determining Ventilation Requirements for Continuous Miners," which appeared in the March 1962 issue of MINING ENGINEERING, is offered by recent investigative work done at the Safety in Mines Research Establishment, Ministry of Power, Sheffield, England. Highlights of this research are outlined here. Accumulations and layers of methane form in a mine roadway because it is difficult to mix methane with air beneath it by turbulent diffusion. Such mixing involves work contrary to buoyancy forces. In specifying requirements for good ventilation it is not, therefore, sufficient to state that the airflow must be turbulent in the absence of methane. Fundamental work at SMRE on the behavior of methane roof layers has led to the formulation of rules for controlling methane roof layers which specify the ventilation velocity needed to ensure adequate mixing in terms of the rate of flow of methane into the layer (V = cu ft per min) and the airway width (D = ft). A "layering number" for methane and air has been defined by [U37/V/D] where U is the mean ventilation velocity in ft/min in the upper half of the airway. In a horizontal airway there is no mixing by turbulent diffusion for values of the layering number less than about 2, resulting in extensive roof layers. But with a layering number of 5, the layer is "brought under control"-i.e., a further increase in the layering number will shorten the length of the layer only slightly, and a small decrease in the layering number will cause only a small increase in the length of the layer. In a sloping roadway with uphill ventilation, higher values of the layering number are needed to achieve this "controlled" condition; the values range from about 5 at small slopes to about 8 at a slope of 1: 10. In downhill ventilation it is possible for layers to "back" against the ventilation, i.e., to flow uphill. The critical condition for preventing backing can also be expressed in terms of the layering number. Backing will be prevented if layering numbers are about 3 for small slopes and about 4.5 for large slopes; these values for downhill ventilation also give good control of the layer.

Jan 10, 1962

By A. Lee Barrett

THE Maintenance Committee of the Coal Division of the American Institute of Mining and Metallurgical Engineers is presenting as a part of this report the second of a series of maintenance cost comparisons. The committee's purpose is to assemble maintenance costs on all equipment connected with mechanical operations at the face of coal mining and to arrange these costs by districts so that comparisons can be made between districts and within districts. The committee, this year, sent 35 questionnaires to representative coal companies who either reported last year or had advised specifically of the inability to report to last year's questionnaire primarily because of limited time. The response to the questionnaire this year was not as good as last year, only 20 of the 35 selected companies returning a completed questionnaire. This year's data has been .compiled and combined with last year's data to present a comparison of the 1945 and 1946 costs of loading machines, shortwall cutting machines, universal cutting machines, service locomotives, shuttle cars, and mine cars. The same tabulation by districts is used as was used for 1945. As was indicated by last year's report there is considerable variation in the maintenance cost of mining machinery in the various coal mining districts and due to this high variability it was not felt practical to attempt to Arrive at weighted averages. Consequently, all average figures used in this report are straight averages. An analysis was made of companies reporting both this year and last year in an attempt to determine the trend in maintenance costs for different classes of equipment. Ten representative companies are used in this computation. Table I shows the average cost for 1945 and 1946. It is felt that the negative trend in the maintenance cost of universal cutting machines probably represents the effect of the purchase of a relatively large number o new machines in 1946 with little maintenance cost appearing during the first yeas of operation. The grand total figure indicates an upward trend amounting to plus 18.7 pct. However, this figure is viewer with some suspicion because of the effect of the universal cutters decreasing maintenance cost and it is concluded that direct application of percentage increase should be made to types of equipment. In Table 2 covering maintenance costs of various types of mining equipment for 1945 and 1946 the results, obtained in Table I indicating trends were applied to those

Jan 1, 1948

Trans. Pamphlet Volume Number Title Author Meeting and Page* 1033 Relation of Air Presaure to Drilling H. W. Seamon New York 66, 743. 766 Speeds of Hammer Drills . Feb. 1921 1034 Time Factor in Depletion of Mines J. W. Roberts New York 66, 711 Feb., 1921 1035 Calculation of Ore Tonnage and Grade J. E. Harding New York 66, 117, 122 from Drill-hole Samples Feb., 1921 1038 Diacuasion of Papers Presented in 1920 1041 Run-off and Mine Drainage H. N. Eavenson New York 66. 624. 630 Feb.. 1921 1043 The Health of the Underground Worker A. J. Lanza New York Feb, 1921 1045 Dust-ventilation Studies in Metal D. Harrington New York 66, 272, 288 Mines Feb., 1921 1046 Discussion of Papers Presented at New York Meeting, 1921 1072 Breakage and Heat Treatment of Rock- B. F. Tillson New York 66. 758 drill Steel Feb., 1921 1073 Discussion of Papers Presented at New York Meeting, 1921 1076-M Analysis of Some Drill-ateel Teats F. B. Foley New York 66,789 Feb.. 1921 1077-M Application of Magnetic Analysis to C. W. Burrows New York 66, -796 Rock Drills Feb., 1921 1078-M Heat Treatment of Rock-drill Steel G. H. Gilman New York 66.779 Feb., 1921 1080 What is the Ideal Drill Steel? F. H. kingdon New York 66, 807 Feb.. 1921 1081 Rock Drill-Steels, etc. W. T. Ober New York 66,814 Feb.. 1921 1082-C Underground Mine Development, Its J. B. Dilworth Wilkes-Barre 66,715, 761 Definition and Valuation Sent.. 1921 1081 Drill Steel from Hollow Ingots P. A. E. Armstrong New York 66,809 Feb., 1921 1068 Authors' Replies to Recent Discussion 1092 Heat Treatment of Rock Drill Steel A.E.Perkins New York 66,811 Feb., 1921 1096-M Octagonal Ventilation Shaft of Davis- J. L. Bruce Wilkes-Barre 66. 252, 608 Daly Copper Co. Sept., 1921 1100-C Determination of Electrical Equip- G. Bright Wilkes-Barre 66,580,606 ment for a Mine Hoist Sept., 1921

Jan 1, 1927

By T. M. Gurr

The United States is the world's leading producer of phosphate rock. In 1975 according to the US Bureau of Mines' statistics, 44.3 million tonnes (48.8 million st) of phosphate rock were produced in the United States, l which is 40.6% of the world's production.2 The major phosphate producing areas of the United States are located in [Fig. 1] and the production for 1975 is listed as follows: [ ] All of these areas produce phosphate from deposits which are of marine sedimentary origin. Occurrences of phosphate exist throughout the United States in numerous locations that are of both igneous and sedimentary origins. However, these other phosphate occurrences vary greatly in extent and economic significance. Georgia, South Carolina, California, Texas, Arkansas, Kansas, Iowa, Alabama, Kentucky, and Virginia are but a few of the states in which phosphate is thought or known to exist. The near future expansion will probably continue to be in, or near, existing producing areas, (i.e., Florida and North Carolina).

Jan 1, 1980

By William Kobbé

I. INTRODUCTION THE word recovery as used in this paper is applied in its broader sense and not limited to wells producing from horizons of unconsolidated sands. Certain problems connected with the winning of petroleum from such horizons present themselves while drilling is in progress and should be considered before drilling is commenced wherever unconsolidated sands are expected. Maximum recovery depends not alone upon efficient pumping methods but also upon the selection of a proper drilling system and the completion of a well especially adapted to the extraction of these oil-bearing sands. II. DRILLING DETERMINING FACTORS IN SELECTION OF METHOD The selection of a drilling method for the development of a region in which the oil reservoir consists of unconsolidated sands is based on the following considerations: (1) Character of the formations overlying the reservoir; (2) thickness of the oil-bearing stratum or strata; (3) thickness and character of water or gas sands; (4) gas pressure to be encountered or expected; (5) total depth of well.

Jan 12, 1916

By G. C. Mudd, E. J. Myers

Within the last 15 years David Brown Gear Industries has manufactured approximately 200 large mill gears over 6m diam., 58 of them over 9 m and up to 12 m diam. The experience has not been without problems, due to a lack of clear understanding of the loads and stresses imposed on large gear wheels. American Gear Manufacturers Association (AGMA) practices suggest that a service factor be used for mill gears. But what is meant by "service factor"? The layman might be forgiven for believing that the term is synonymous with "safety factor," but this is certainly not true. The service factor is an aggregate of the following in some proportion: -An application factor, i.e., an allowance for the fact that systems do not run smoothly with uniform torque. -An ignorance factor covering the imperfections in the basic gear calculation. -Possibly a safety factor. In the following sections some of the ways in which the limits of applicability can be overstepped are discussed.

Jan 1, 1983

By D. L. Martin, E. R. Parker

DURING the heat-treatment of silver specimens for tensile tests it was observed that the bars blistered and became brittle when heated in a hydrogen atmosphere. [ ] To check this unexpected result, a wide variety of commercial silvers were heated in hydrogen at 850°C, Only a few of the materials developed blisters, the most severe of which is the tube pictured in Fig. I. The microstructure of a cross section of the tube is shown in Fig, 2. The embrittlement is extremely severe at the edge; the blisters result from the severe deforma- [ ] tion of the surface material by large underlying gas pockets, The effects resulting from hydrogen embrittlement of silver have been observed by numerous investigators over a long time1,2,3 although it was only recently that a clear explanation was offered ,4 However, the damage resulting from hydrogen embrittlement has not been generally recognized; and it is of advantage to know more about this phe-

Jan 1, 1943