Search Documents

By James C. Duchon

The use of extended workdays (regular shift lengths of 10 or 12 h (hour), while still maintaining a 4O-h workweek) in mining operations is attracting growing interest in the United States. There is very little doubt that extended workdays is a very popular alternative among the work force because of the significant increase in days off, including weekends, especially when compared with traditional rotation schedules of working seven straight shifts or having only one weekend off every 4 to 6 weeks. However, there are some serious concerns by management, workers, unions, and various governmental policymakers that working 10-or 12-h days may create an added risk of accidents and health problems. The U.S. Bureau of Mines reviewed the literature studies related to the safety and performance issues of extended workdays. This report presents a summary of those findings. The studies examined in this review are divided into three sections: (1) laboratory, (2) field, and (3) accident and injury analysis. In general, results are inconclusive. Studies have shown both positive and negative effects. It is concluded, therefore, that in industries such as mining where accidents are a serious concern, special measures and evaluation in the use of extended workdays be considered.

Jan 1, 1994

By Abrasive Materials

Table 1.-Salient abrasive statistics in the United States [ ]

Jan 1, 1967

By Harry V. Makar

As part of a continuing research program for conserving domestic mineral resources, the Bureau of Mines is investigating new and improved scrap identification techniques to improve sorted mixed scrap purity. This report focuses on various classes of wrought and cast copper alloys produced with recycled scrap. Based on a survey of the literature, principal alloys, such as the brasses and bronzes, are examined with respect to impurity elements and their effects on metallurgical behavior. Effects of elements such as lead, antimony, iron, chromium, and aluminum are discussed. The metallurgical effects described include hot shortness, fire cracking, and undesirable phase transformations.

Jan 1, 1985

By A. Tewarson

Combustibility data are presented for 14 samples representing commonly used mine materials (treated and untreated wood, conveyor belt and brattice cloth). The combustibility data were obtained in the Factory Mutual Small-Scale Combustibility Apparatus (sample area -0.008 m ). The hazards associated with the mine materials were evaluated in terms of: 1) ignition/ surface flame spread using an ignition parameter (IP). A reasonable correlation was found between IP values and U.S. Bureau of Mines ratings for conveyor belts and brattice cloth and large-scale fire test data for treated and untreated timber sets; 2) generation of combustible vapors, using a vapor generation parameter (VP); 3) heat release using a heat generation parameter (HP). A reasonable correlation was found between HP values and the large-scale fire test data for treated and untreated timber sets; 4) generation of "smoke," toxic and corrosive products using a chemical compound generation parameter (CP); and 5) light obscuration by "smoke" using the light obscuration parameter (LP). All the wood treatments, except Fireguard, were found to be effective in reducing the fire hazard. The effectiveness of the treatment appears to be due to enhancement of carbon formation in the solid phase and enhancement of water formation in the vapor phase. Concepts are presented for establishing 1) the relationship between various parameters (IP, VP, HP, CP, and LP) and basic properties of materials, and 2) the usefulness of the parameters as criteria for the combustibility and fire hazard evaluations of the mine materials.

Jan 1, 1982

By C. Özgen Karacan

This study presents the results of core-log analyses from the exploration boreholes, the analyses of face advance rates, and the results of downhole monitoring studies performed in gob gas ventholes for calculation of changes in hydraulic properties in the longwall overburden at a mine site in southwestern (SW) Pennsylvania section of Northern Appalachian Basin. In the ?rst part of the study, coal measure rocks in overburden strata were analyzed and the locations where possible fractures and bedding plane separations would occur were evaluated. In the second part, the hydraulic conductivities were computed by two different slug test analyses methods using the water level changes measured in gob gas ventholes as longwall face approached. Hydraulic conductivities were analyzed with respect to the changes in overburden depth, the locations of the borehole, and mine face advance rates. These data were used to interpret the potential productivities of the gob gas ventholes as a result of fracturing and changes in hydraulic conductivities. The general results showed that the probability of fracturing and bedding plane separations in the overburden increase between strong and weak rock interfaces. Also, the probability of bedding plane separations increases as the interface is close to the extracted coal seam. Evaluation of slug tests showed that the hydraulic conductivity developments in the boreholes and their potential production performances are affected by the underground strata and the roof materials. In situations where the roof material is stiff and thick, the development of high permeability fractures around the borehole will be less. Results also indicated that borehole location with respect to face position affects the fracturing time and permeability evolution as well. Greater overburden depths generally cause earlier fracturing as longwall face approaches, but eventually result in lower hydraulic conductivities and potentially less effective boreholes. Increasing mining rates also resulted in generally lower hydraulic conductivities in the overburden. The results of this study were intended to improve the interpretation of gob gas venthole performance and to provide better siting of these boreholes.

Jan 1, 2009

By H. R. Shell

To obtain a better understanding of the crystallization of fluoride containing amphiboles from melts, an investigation of the range of stability between fluoramphi-boles and other minerals was conducted by the Bureau of Mines. This study has shown that the stability of fluoramphiboles is strongly influenced by both fluoride concentration and isomorphic replacement. Over 150 reactions were made with different compositions and reaction conditions. substitutions attempted and the phases that formed when the composition was crystallized by cooling from the melt are discussed. The attainment of equilibrium in these multicomponent systems is not claimed. Many ions that would be expected to enter the amphibole structure instead resulted in crystallization of phases other than amphibole. Those compositions that resulted in a high yield of acicular fluoramphibole by crystallization from the melts are shown in table 2. The fluoramphiboles obtained from melts typically had an acicular crystal habit and a hardness of 6 to 7 on the Mohs' scale. Although many had relatively high length to cross section ratios, none were fibrous; it was concluded that the possibility of synthesizing a fibrous fluoramphibole from a melt was low. However, many compositions can be crystallized into a tough, hard, impact-resistant mass of interlocking acicular crystals.

Jan 1, 1958

By J. L. Wiley

[NOTE. - P before the number indicates that the ab tract appears in patent section. Abstract numbers without. P appear in literature section. A Abietic acid, hydrogenolysis - 404 Acetone, recovery - P-4024 Acetylacetonate catalyst - P-3352, P-3664, P-6067 Acetylene, production - P-2556, P-3169, P-4064, P-4221, P-4222, P-5002 Acid catalyst - P-4584 Salts - P-4555 See also Specific acid. Acid treatment. See Procedure. Adsorption. See Hydrogen, adsorption. Agitation. See Equipment, agitators; Procedure. Alcohols: Decomposition -1128 Hydrogenation - P-3288, P-4743 In motor fuel - 1486]

Jan 1, 1952

By Henry H. Ginsberg

The effectiveness of 0.01 pct. molybdenum, as ammonium molybdate impregnated on coal, on the hydrogenation of a high-volatile bituminous C coal at 8,000 p.s.i.g. and 460° to 480° C. has been studied in a pilot plant by the Federal Bureau of Mines. Under these conditions, the Bureau obtained 98 to 99 pct. conversion5/ of coal to liquids and gases at throughputs of 29 to 101 lb. of m.a.f. coal per cubic foot of reaction space per hour. At 460° C. the indicated yield of oil ranged from 63 pct. (based on m.a.f. coal) at a throughput of 35 lb./c.f.h. (pounds per cubic foot per hour) to 68.5 pct. at a throughput of 58 lb./c.f.h., and the yield of gaseous hydro-carbons ranged from 25.5 to 19 pct. at the same throughputs. The maximum measured yield of oil boiling under 325° C. was 47 pct.

Jan 1, 1960

The last issue included a discussion of recent indications of a 1983 recovery and a brief analysis of the contribution of the U.S. mining industry to the gross national product (GNP). In this issue we present sales and other data indicating the strength of the 1983 recovery and quantitatively analyze the structural shifts that have taken place in the U.S. economy and mining industry since 1972, and changes in electricity consumption by the mining industry. U.S. Economic Recovery The tentativeness in the February/March issue of Minerals and Materials regarding the strength and sustainability of the U.S. economic recovery can now be replaced with a note of increased confidence. Real growth of GNP on an annual basis in the first quarter of 1983 was 2.5 percent, compared with 1.4 percent predicted in the Economic Report of the President.1/ Preliminary second-quarter 1983 data provide further cause for optimism. Recently released data indicate that consumer spending is playing a key role in the recovery. Retail sales have increased significantly across a wide array of goods, especially consumer durables, where sales increased 4 percent from March to April (table J) and were 12 percent higher in April [ ] than the 1982 monthly average. Consumer durable sales were led by sales of building materials spurred by the growth in residential construction, motor vehicles and parts, and household durables, including appliances and furniture.

Jan 1, 1983

By John F. Papp

Based on a review of historical domestic and international chromium metal production capacity, production, consumption, trade, and trade literature, world annual chromium metal production capacity in 1995 was estimated to have been 38,300 metric tons, a drop from 43,500 tons in 1994. World chromium metal production and consumption were estimated, on average from 1984 through 1992, to have been 21,000 tons per year. U.S. consumption was estimated, on average over the same time period, to have been 6,200 tons per year. The major world chromium metal producers between 1984 and 1995 were China, France, Germany, Japan, Russia, United Kingdom, and United States. From 1984 through 1992, world trade averaged 8,400 tons per year. Germany and the United States accounted for over 75 percent of imports on average during the same time period. U.S. chromium metal import value rose from under $1 per kg before 1964 to over $6 per kg in 1993. Over the same time period, prices rose from about $4 per kg to about $10 per kg. Chemical specifications have become more stringent. Detailed chromium metal trade, prices, value, chromium metal chemical specification, and production capacity by country are reported. A shift in trade patterns was anticipated as Japan exits production and displaces Germany as the second largest importer and as Russia increases its role in world trade.

Jan 1, 1995

By R. Blickensderfer

The laboratory wear testing capabilities of the Bureau of Mines are described, Wear tests are used to support the Bureau?s research efforts toward reducing the wear of equipment used for mining and minerals processing and any wear involving a loss of strategic or critical materials. The emphasis is on abrasive wear because it accounts for most of the wear losses that occur in mining and minerals processing equipment, Spalling wear, caused by repetitive impact in grinding equipment, also is included, Ten abrasive wear tests, including high- stress and low-stress and two-body and three-body conditions, are described: dry-sand, rubber-wheel abrasive wear; Taber Abraser; abrasion resistance of refractory materials; dry-particle erosive wear; elevated-temperature, dry-particle erosive wear; low-angle slurry pot; jaw crusher gouging wear; ball mill wear; pin-on-drum abrasive wear; and high-speed impact gouging. Two repetitive impact tests are described: ball-on-block impact-spalling and ball-on-ball impact-spalling. Test equipment, procedures, and specimens are described, and typical test results are presented and discussed.

Jan 1, 1985

By Robinson Newcomb

Gypsum is a form of hydrated calcium sulfate (CaS04.2H20) which is widely distributed over the earth's surface. The two varieties worked commercially are rock gypsum and incite. Rock gypsum, the variety commonly mined for commercial purposes, is a relatively soft mineral having a specific gravity of about 2.3 and weighing about 150 pounds per cubic foot. The chief producing States are New York, Michigan, and Iowa. Before being used the crude gypsum is ground and generally calcined. The predominant use of gypsum is for building purposes (the manufacture of plaster), for which calcined gypsum is required. Gypsum is also used as a retarder in Portland cement, as fertilizer, and for other purposes. GYPSUM MINING Crude gypsum is mined by two methods - underground and open-pit. Although the use of the former method predominates, open-pit mining increased in relative importance during the early twenties and contributed about two-fifths of the output during the period 1925-38.

Jan 1, 1940

By John F. Papp

The objective of this U.S. Bureau of Mines study is to calculate an accurate, reliable estimate of chromium and nickel content of stainless and heat-resisting steel produced in the United States. The columbium, manganese, molybdenum, titanium, tungsten, and vanadium contents of this steel are also calculated. Such contents are required for estimating the quantity of alloying element recovered from recycled stainless steel and consumed by market sectors. In this investigation, the elemental fraction of stainless and heat-resisting steel was calculated as the ratio of the weight of element contained in stainless steel to the weight of stainless steel produced. The elemental fraction has been calculated as a time-averaged, grade-averaged value. The elemental fraction was averaged from 1962 through 1983, and averaged over the grades for which production was reported by the American Iron and Steel Institute during that time period. The 1962-83 average elemental fraction of U.S.-produced stainless and heat-resisting steel was calculated for chromium to be about 0.17 ± 0.01; columbium, 0.00014 ± 0.00003; manganese, 0.015 ± 0.005; molybdenum, 0.004 ± 0.001; nickel, 0.07 ± 0.01; silicon, 0.009 ± 0.001; titanium, 0.0004 ± 0.0001; tungsten, 0.0001±0.00003; and vanadium, 0.00003±0.0000l.

Jan 1, 1991

By E. P. Youngman

In the Unfederated Malay States, with the exception of Johore, the rights of suzerainty, protection, and administration were transferred by giam to the British Government in 1909. In the States of Kelantan, Trengganu, Kedah, and Perlis, the rulers are assisted by State Councils and by British advisers appointed by the British Government.3 With respect to Johore, the largest, richest, and most highly organized of the Malay States not in the Federation, the treaty of December 11, 1885, with Great Britain, defined the relations of the State to the British Govern- ment and allowed the Maharaja to assume the title of "Sultan"; an amendment to this treaty (May 12, 1914) provided that the Sultan should be advised by a British officer, the General Adviser. ...... The political organization of the States is reflected in the mining legis- lation, Johore being the only one having a comprehensive code. The mining enactments now in force, according to the High Commissioner for the Malay States, are as follows:

Jun 1, 1932

By T. A. Henrie

The Federal Bureau of Mines has investigated methods of sodium reduction of titanium chlorides to produce high purity titanium metal (14).4/ This investigation was made to obtain a better understanding of the reactions involved in sodium reduction of titanium chlorides and was part of the Bureau's activities toward improving the technology of titanium. Theoretical and experimental evidence show that sodium reduction of titanium tetrachloride occurs by stepwise reactions. The first stage reduction between sodium vapor and vapors of titanium chlorides produces titanium di-and trichlorides which subsequently condense with sodium chloride to form a salt mixture. The second stage reduction takes place in the condensed salt mixture between sodium and titanium subchlorides. Final reduction is a heterogeneous reaction between two separate phases, the a phase which consisted of sodium dissolved in sodium chloride and the ß phase titanium subchlorides dissolved in sodium chloride. The mechanism of the heterogeneous reaction between these phases is electrochemical in nature. The model proposed is a galvanic reaction at the interfacial region.

Jan 1, 1960

By C. Harry Benedict

This paper presents the details of milling practice and costs at the conglomerate mill of the Calumet & Hecla Consolidated Copper Co., Lake Linden, Mich., and is one of a series on milling methods being published by the Bureau of Mines. GENERAL DESCRIPTION The mines of the Calumet & Hecla. Consolidated Copper Co. are located in the Keweenaw Peninsula of northern Michigan. The mines of this district lie in a belt not over 4 miles wide and 100 miles long, which contains more or lees commercial ore. The Calumet & Hecla properties are the farthest north, except for the Seneca, of the operating mines. The district borders on Lake Superior, and by means of the Portage and Torch Lake waterways the largest lane vessels, can transport coal and other supplies from the lower Lakes directly to the company docks.

Jan 1, 1930

By John B. Goodman

A LOW-TEMPERATURE carbonization assay test is described, and factual data derived from this test are presented. The test procedure outlined in this report incorporates a mild-steel retort of improved design, an accurately controlled method of heating, and a complete collection and condensation system for the solid, liquid, and gaseous products of carbonization. The test described establishes, under closely controlled conditions, the relationship of temperature to yields of products on carbonization. Noncoking or weakly coking coals and other carbonaceous material are particularly amenable to testing by the assay. Mass balances of 100 percent± 0.3 are obtainable by this test. It is believed that the efficiency of the test and the accuracy of the type data obtained have been materially increased.

Jan 1, 1953

By Norman G. Foster

The mass spectra of 14 previously unreported alkylthiophenes are pre-sented. Low ionization voltage data of selected compounds from these 14 and 23 previously reported alkylthiophenes are presented and discussed for their value in supporting fragmentation mechanisms analytical correlations. A comparison with and corroboration of earlier correlations is made. Additional correlations concerning detection of side chain branching and the detection of ethyl-alkyl and propyl-alkylthiophenes are made. A discussion of the possible fragmentation routes and mechanism of fragmentation is given. Speculative structures are inferred s out some of the ions and hence this work provides a basis for suggesting fation mechanisms for the alkylthiophenes according to modern theories ass spectrometry. Verification of these mechanisms must await the availability of isotopically labeled molecules which are labeled in specific lotions that permit the definition of the paths of frag-mentation. Some suggestions for further work to generalize on the correlations and studies made to this point are presented.

Jan 1, 1965

By Jr. Hazen

This report documents 653 sets of sample data involving 78,366 assays obtained from past exploration for various minerals and metals. Most of these data have been taken from published reports describing exploration projects, conducted jointly by the Bureau of Mines and the Geological Survey, for the Strategic Minerals Program from 1940 through 1949. Means and standard deviations have been computed for the exploration assay data and have been plotted on graphs for 22 minerals and metals. A mathematical model, based on the binomial distribution, has been developed to explain the configuration of the plots of the exploration means and standard deviations. The two statistics, mean and standard deviation, which describe assay data, have been used for simulating probability models. These probability models then have been combined with the binomial model of the exploration assays and related to the sequential decision process associated with exploration drilling for mineral deposits. These probability regions can be used to form the basis for sequentially predicting the probable range of the average grade of mineral or metal that may be expected as an exploration drilling program is continued after the initial discovery of mineralization has been made.

Jan 1, 1966

By J. R. Thoenen

This circular is part 2 of the third subject (entitled "Excavation") of a series summarizing; the technical problems involved in the production and preparation of sand and gravel. Part 1 discussed the use of power shovels, draglines, and excavator cranes. This paper discusses the use of the power scraper, slackline cableway excavator, and hydraulic monitor, and part 3 will discuss the use of various types of dredges. Subsequent papers in the series will discuss the use of haulage equipment, the application of both excavating and haulage equipment to various types of deposits, and operating costs. THE POWER SCRAPER The power scraper is a younger member of the various forms of gravel excavators. It is a mechanized enlargement of the slip scraper and other scrapers which depend upon animals for power and has a greater range of operation from a single set-up than any other excavation unit except the slackline cableway excavator.

Jan 1, 1935