Search Documents

By Stephen Krickovic

Air quantity-pressure and methane concentration surveys were conducted by the Bureau of Mines in accessible portions of an area being pillared in a Pittsburgh coalbed mine in West Virginia. These included two mined-out and three active butt headings and a bleeder system. The particular mine workings were started in virgin coal directly from a set of main headings; the main reason for the study was the difficulty usually encountered in adequately bleeding the gobs under such conditions. Although the two separate return airways in each active butt heading and the North and 1 Left bleeders contained acceptable methane concentrations (0.01 to 0.78 percent in the butts and 0.73 to 1.0 percent in the bleeders) with significant total methane removal (109 cfm in butts and 631 cfm in bleeders), there were relatively large areas in the gobs with possible minimal airflows. This condition appears to have developed from lack of systematic regulation of the airflow across the gobs and appears to indicate the existence of considerably more methane in the probably low flow areas in the gob.

Jan 1, 1973

By Stephen P. Holt, John A. Bowsher

A preliminary examination of the mica deposits in Culberson and Hudspeth Counties , Texas , was made in September 1942 by A. B. Needham, district engineer of the Bureau of Mines . The deposits were reexamined by R. C. Redfield , associate mining engineer of the Bureau in November 1942, at which time he was accompanied by Philip S. Hoyt , geologist , and J. C. Moore , foreman of the Texas Mica and Feldspar Company . Exploratory work was started on February 16 , 1944 , and terminated on April 30 , 1944. A crew of 4 to 10 men was employed under the supervision of the authors .

Feb 1, 1947

By C. Lorimar Colburn

"The use of helmets during the war has accentuated interest in the advisability of using stiff hats in mines to protect the miners against falling rocks. About forty per cent of the accidents in mines are due to falling rocks or roof. A large number of these accidents could be prevented if the miners wore stiff hats or helmets.The use of head protective devices in minas is not new, for they have been in use for many years in Europe and in the Lake Superior District in the United States. In practically all of the mining districts in Europe stiff hats of some kind are required by the mine management. George S. Rice, chief mining engineer of the Bureau of Mines, reported that in Germany, Belgium, and France stiff hats made of papier mache or felt rosin are in use. Similar hats are generally employed in the Lake Superior District. In building the subways of New York and Philadelphia it was the practice of engineers and workers to let the hair grow very long and to wear a close fitting cap or felt hat. In Germany the hats are high like the military helmets, whereas in France and Belgium they fit more closely to the crown. In England the practice is mixed. As a rule the miners use soft padded caps, but in Yorkshire many of the miners use sole leather, tight-fitting caps of jockey pattern with the seam forting a little ridge down the middle of the cap. These hats are very useful allow thin beds of coal, as in crawling one is very likely to strike his head a sharp piece of rock or on a timber. Of course, such mishaps are more likely to occur to a man not familiar with the mine. It must be admitted such hats do not stick on well, though this is usually due to their not being especially fitted. The German hat is particularly unsuited to an American-shaped head.It is interesting to note that on the continent tight cotton caps are generally worn over the hair and under the hard hat. This is a measure for cleanliness which is excellent. In low beds of coal share much crawling on hands and knees is necessary the dirt and coal dust sift down, making the miner black and dirty. In metal mines stiff hats are of especial use in shaft work; also in raises or high stapes. A small fragment of rock falling some distance either down a shaft or raise would kill a man if it struck him squarely on the head. A stiff hat or helmet may protect him and save his life. At a station in a shaft where men are loading the cage or skip, some kind of adequate head protector should be compulsory. A head-protecting hat or cup which is also a good insulator should be worn where there is danger of striking one's head against a wire carving an electric current."

Jun 1, 1920

By Charles L. Kimbell

In overview, the world's mineral industry in 1989 registered gains over its 1988 performance, but these gains were by no means as pronounced as had been those of 1988. The traditional statistical measures of mineral industry performance, namely production, trade, and consumption levels, reflected significant growth in most industry sectors from crude material extraction through the gamut of down- stream processing. Growth in market economy countries generally exceeded growth in the centrally planned economy countries as a result of a variety of causes that will be covered subsequently, but even among the centrally planned countries there were some upturns. In contrast to these measures of the soundness of the industry, the situation for nonfuel mineral and metal prices was less satisfactory than in 1988, and low crude oil prices continued as a problem for the all-important petroleum sector, despite some gains during the year. The oil price situation mitigated against price increases for competitive fuels. Although this was unfavorable for fuel producers, it remained advantageous to consumers, including nonfuel mineral producers, processors, and transporters. Thus it cannot be viewed as a negative factor for the whole of the global mineral industry. Global crude mineral output value was estimated at nearly $1,420 billion in current dollars, an increase of 9% over the 1988 level, and an increase in current dollar terms for the seventh consecutive year. Measured in terms of constant dollars, however, adjusting for inflation, the increase was only 4.7% compared with the 1988 level. Despite the prolonged growth trend, the 1989 crude mineral output value level was still 3.2% below the record high set in 1980, which was $1,467 billion in terms of 1989 dollars.

Jan 1, 1992

By Scott Turner

We have gathered here in Pittsburgh, at the Nineteenth Annual Safety Congress, in order to advance the cause of safety. Although my personal inter- est in this movement alone would have been sufficient to insure my presence here, specific duties have brought me to this congress in an official capacity. My responsibilities as the head of the United States Bureau of Mines, which makes the promotion of safety in the mining and allied industries one of its major activities, necessitate my attendance. My obligations as president of the Joseph A. Holmes Safety Association, an organization closely allied to the bureau and which has for one of its objects the public recognition and reward of outstanding achievements in safety, require that I be present at this time. This morning, my job is to present the Holmes safety certificate to the Lehigh Portland Cement Co. First I will remind you of the nature of this safety association, named in honor of the first director of the Bureau of Mines. After Mr. Holmes' death, in 1915, a number of influential organizations banded together to commemorate the name of this leader in the conservation of human life. In order that you may appreciate the significance of an award by the Joseph A. Holmes Safety Association, I shall read you the list of 24 national organizations which comprise its membership:

Nov 1, 1930

By L. R. Burdick, J. F. Barkley

"The agglomerating index of coal is an index based upon the nature of the coke residue left when the standard volatile-matter determination of the well-known proximate analysis is made. In this determination a small amount of coal is heated in a container to about 950° C. (1,742° F.), at which temperature the volatile matter is driven off, leaving a coke formation. The coke residues for various coals are quite different in physical structure: and, for some time past, work has been done on studies of the nature of these residues in connection with the coking of coal. In 1934 Gilmore, Connell, and Nicolls proposed use of the agglomerating index for indicating the dividing line between noncaking coals and those having weakly caking properties. 4/ Its use was adopted in the standard classification of coals by rank as a requisite physical property index to differentiate semianthracite from low-volatile bituminous coal and also high-volatile ""C"" bituminous from subbituminous ""A"" coal, as shown in table 1, the standard coal classification adopted by the American Society for Testing Materials and the American Standards Association. 5./In studying the agglomerating properties of coals based on the coke residue the Bureau of Mines has adopted the notation given in table 2. Coals that in the volatile-matter determination give a coke residue either in the form of an agglomerate button that will support a 500-gram weight without pulverizing or a button that shows swelling or cell structure are considered to be agglomerating."

Nov 1, 1938

By Charles A. Steen

Publication of this information circular results from an invitation extended to the Bureau of Mines by the Utex Exploration Co. to visit the company mine, on the Mi Vida claim about 39 miles southeast of Moab, in the Big Indian mining district, San Juan County, Utah. The Bureau is pleased to present this record of the Utex mine -- a property that in the relatively short period of 4 months has become one of the major uranium-ore producers on the Colorado Plateau. The ore deposit was discovered in July 1952 by Charles A. Steen, a geologist-prospector, now chief geologist of the Utex Exploration Co., in tae course of drilling the first diamond-core borehole in the Big Indian district. High-grade ore, 14 feet thick, was penetrated by the borehole. Sinking of a shaft, from which to develop the ore body, was begun in October, and the first shipment of ore left the property December 6, 1952. Ore production, as recorded on ore-settlement sheets received by the company up to July 15, 1953, totaled 16,000 tons averaging, 0.51 percent U305 and 1.25 percent V205. Discovery of the ore body and the large production of ore were achieved without any financial assistance from the Government.

Jan 1, 1953

By Jack C. White

This U.S. Bureau of Mines report assesses the resource potential of trace metals present in commercial Ti mineral concentrates. Metals of greatest interest: are those defined as "strategic and critical" by the U.S. Congress in 1981. Metals of interest in Ti mineral concentrates are Cb, Cr, Ta, Th, U, V, and Zr. Commercially available Ti mineral concentrates were studied. Characterization and analysis of major and minor constituents were performed by X-ray diffraction, neutron activation, inductively coupled plasma emission, atomic absorption, and classical wet chemical techniques. Of the metals investigated, the Cb, Ta, and V content of some concentrates may be a significant potential resource, depending on their amenability to recovery.

Jan 1, 2010

By N. Greninger

The Bureau of Mines examined the possibility of a seasonal variation of respirable dust concentration in U.S. coal mines. The first step was to review company and MSHA-inspector dust samples that had been collected during the past several years in 14 selected mines for compliance purposes. Results indicated severe scatter in data; most standard deviations of the dust concentrations measured in winter and summer months were comparable in magnitude with the mean values of dust concentrations for the seasons. Therefore, a detailed statistical analysis was conducted. At the 90% confidence level, the company samples of three mines had winter means 0.15 to 0.54 mg/m3 higher than the summer means; six mines had negligible seasonal variations; and five mines had winter means that ranged from higher to lower than the summer means. Inspector data, however, were too sparse for analysis. In view of both the low frequency of occurrence of a seasonal effect and its wide scatter in several of the mines, the study was ended with the conclusion that seasonal varia-tion in respirable dust levels, in general, is an insignificant factor.

Jan 1, 1986

By John Owens, Hamid Maleki

Efficient and safe use of mobile roof supports (MRS) depends on the interaction between the MRS and coal strata. Of particular interest to this study are the mechanics of strata deformation as influenced by geologic conditions, pillar extraction methods, and MRS load-bearing capabilities. To provide a better understanding of the mechanics of strata deformation, the authors have collected and reviewed measurements of convergence and stress in one western U.S. mine and have completed pseudo-three-dimensional, boundary-element modeling for two typical pillar-pulling plans. Stress distribution in the mine roof above pairs of MRS’s was calculated to demonstrate how MRS’s contributed to the control of roof block movements. It was shown that overall stress and roof-floor convergence patterns were most influenced by the stiffness of coal-measure rocks and by pillar-pulling sequences and layouts. MRS’s and other support systems play a critical role in controlling the stability of both the immediate roof and the middle roof for a distance of up to 18 m (60ft) above the seam. MRS’s provide unique ground control advantages over other types of secondary support by significantly reducing the time between mining and installation of secondary support. Although MRS’s are similar to posts in stiffness and capacity, they are more effective than posts under static loads because they can yield and still maintain loads at near-peak capacity, whereas posts fail and loose their ability to limit mine roof deformation.

By C. E. Armantrout, H. Kato, M. I. Copeland

The data collected during this investigation indicate that the chromiumgadolinium system has extensive liquid immiscibility and one eutectic point . Liquid immiscibility occurred at temperatures above the monotectic isotherm , 1,830 ° C , which extended from less than 0.25 to about 85 weight - percent gadolinium . The eutectic was at 96 percent gadolinium and 1,170 ° C. Gadolinium and chromium were the only phases in this system . There was a solid solubility of less than 0.25 percent gadolinium in chromium at 1,730 ° C and less than 0.10 percent chromium in gadolinium at 1,160 ° C. The alloys were prepared by nonconsumable - electrode arc - melting , and the alloy system was investigated by heat treatment , metallography , thermal analysis , and X- ray diffraction . All the melting , heat treatments , and thermal analyses were conducted in a vacuum or in helium because of the reactivity of chromium and gadolinium with the components present in the atmosphere at elevated temperatures .

Jan 1, 1964

By P. M. Brown

The Bureau of Mines is investigating a dewatering technique for coal-clay waste that uses a flocculant, polyethylene oxide (PEO). This flocculant forms strong stable flocs that can be dewatered on a static screen. A field test unit (FTU) using this technique was operated at approximately 400 gal/min, using a waste stream from the flotation circuit of a coal preparation plant. Consolidated coal-clay material con-taining 55 to 60 pct solids was produced when the flotation circuit slurries of 2.7 to 8 pct solids were treated with 0.1 to 0.3 Ib PEO per ton of solids. The FTU was also operated at 64.5 and 87.5 gal/min using a portion of the underflow slurry from the preparation plant's thickener. Consolidated coal-clay material containing 55 to 60 pct solids was produced when the thickener underflow slurries of 19 to 24 pct solids were treated with 0.08 to 0.2 Ib PEO per ton of solids. PED-treated materials continued to dewater when placed in a pit.

Jan 1, 1983

By R. W. Stahl

Methane, a highly explosive gas evolved during the coal-formation process, is one of the hazards of mining most difficult to overcome. It is retained between particles of coal and entrapped in strata overlying and underlying the coal beds to a degree dependent upon the permeability of the enclosing strata. Considering that methane might be encountered at any time during the mining of coal, attempts have been made through the years to minimize the sources of ignition at coal-mine faces, such as the introduction of permissible electric equipment, the prohibition of smoking and open lights, and the development of safer explosives. The sparks created when mining-machine picks contact sandstone or iron pyrites2/ constitute one source of ignition, always recognized as a possibility but never greatly emphasized in the United States until recently, when ignitions began occurring with rather alarming frequency and in widely scattered coal-producing areas.

Jan 1, 1956

By Douglas F. Scott

Researchers from the U.S. Bureau of Mines conducted geologic investigations in an area of the Lucky Friday Mine, Mullan, ID, that included the 5300-107 demonstration stope using underhand longwall cut-and-fill mining. Structural analysis of the area suggested that argillite beds form planes of weakness between blocks of brittle quartzite, and energy may be released along these planes and at the junctures of fractures. Mapping argillite beds and fractures in the stope wall rock showed that the planes of these features diverged and that their attitudes corresponded from one wall to the other. Seismic analysis showed that the number and location of events varied as each cut was mined, with about 39 pct of the total number of events occurring above the cut being mined, about 54 pct below, and 7 pct at the same elevation.

Jan 1, 2010

Lower the respirable dust expo-sure of longwall mine workers by reducing the amount of air-borne respirable dust generated during coal extraction. Approach Increase the moisture content of the coal seam through water infusion before the coal is mined. How Water Infusion Works Increasing the moisture content in coal tends to prevent respirable dust from becoming air-borne during mining and transport. The moisture content of the coal seam can be increased by infusing water into the seam. Water under pressure is forced into the cracks (cleats) of the coal seam through sealed bore-holes. The effectiveness of water infusion is a function of the amount of water the coal seam accepts (its infusibility), which depends on the cleat density (cleat spacing) and cleat size (crack diameter). Thus the effect of water infusion on dust control depends mainly on coal seam characteristics. Water infusion techniques are generally used to restrict the flow of methane gas to the working face; however, the technique provides an alternative dust control method in mines with severe dust problems which limit production.

Jan 1, 1987

By V. A. Marple, K. L. Rubow, Y. Tao

"A personal diesel exhaust aerosol sampler has been designed and evaluated in both laboratory and field settings. The sampler uses size selective sampling for the determination of the respirable mass concentrations of mineral dust and diesel exhaust particulate matter found in underground coal mines. This design is based on the premise that diesel exhaust particulate matter is predominantly less than 0.8 um while mineral dust is greater than 0.8 gm. Operating at a flow rate of 2 L/min, the sampler consists of a 10 mm Dorr-Oliver respirable dust cyclone followed by an 0.8 gm cutpoint impactor and an afterfilter. Field evaluations consisted of sampling at 6 different locations in these underground coal mines. Measured aerosol concentration less than and greater than 0.8 um have been compared with a well characterized cascade impactor.Techniques must be developed for measuring the mass concentration of diesel exhaust particulate matter found in underground coal mines due to the health concerns associated with worker exposure to diesel exhaust particulate matter. Diesel exhaust particles are in the respirable size range and have been regarded as a potential occupational carcinogen by NIOSH (1988). Furthermore, a 1988 MSHA advisory committee directed MSHA to develop a sampling protocol for assessing worker exposure to diesel exhaust particles.The University of Minnesota and the Bureau of Mines, over the past 4 years have measured the size distribution of diesel exhaust particles and mineral dust, both in the laboratory and underground mines (Cantrell, 1987; Cantrell et al., 1987; Cantrell and Rubow. 1988; Marple et al, 1986; Rubow et al., 1988: and Watts et al., 1989). To date, measurements have been made in nine coal mines. Seven mines utilized diesel-powered equipment at the mine face while two used electric-powered equipment. The results of these field tests indicate that mineral dust and diesel exhaust particles can be differentiated on the basis of particle size. The measured particle size distributions have been found to be bimodal with a saddle point at 0.8 um. This has led to the hypothesis that one method for measuring worker exposure to diesel exhaust particles would be to collect size fractionated particle samples separated at 0.8 um with the diesel particles being less than 0.8 um and the mineral dust particles greater than 0.8 um.Aerosol size distribution measurements, using a micro-orifice uniform deposit impactor (MOUDI), have been conducted in the mine intake air portal, intake entry to the working section, haulageway, and section return entry. The MOUDI is a ten stage cascade impactor with particle cutpoints ranging from 0.1 to 15 um aerodynamic diameter (Marple and Rubow. 1984b; Marple et al., 1989). The sampling flow rate is 30 L/min."

Mar 1, 1992

By E. C. Lane

The motor gasoline that is being marketed in the United States this summer is slightly more volatile than that sold a year ago. The increase in volatility is shown by a lowering of the distillation temperatures, ranging from 2°F. at the average initial boiling point to 4°F. at the average end point. During the past nine years the Bureau of Mines has made semiannual surveys of the gasoline marketed in the United States, the survey just completed being the eighteenth in the series. The cities in which samples were collected have been chosen as representative of the more important marketing territories, as it is obviously impracticable to obtain a sample of every gasoline sold in the entire country. Samples were collected in Omaha as well as in the 11 cities where samples were taken last winter. It was believed advisable to include samples from Omaha in order to give a better balance to the survey for the country as a whole.

Jan 1, 1928

By N. S. Dalal, X. Shi

"Electron spin resonance (ESR) measurements provide evidence for the formation of Cr(V) intermediates in the enzymatic reduction of Cr(VI) by glutathione reductase (GSSG-R) in the presence of NADPH, indicating an initial single-electron transfer step in the reduction mechanism. Depending on the pH, at least two different Cr(V) species are generated which are relatively long-lived. In addition, we have detected the hydroxyl (·OH) radical formation during the GSSG-R catalyzed reduction of Cr(VI) by spin trapping, employing 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and a-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) as spin traps. Superoxide dismutase (SOD) causes only a minor effect on the ·OH radical and Cr(V) formation, indicating that the ~ - is not significantly involved in the reaction mechanism. Catalase enhances the Cr(V) formation and substantially inhibits the ·OH radical formation, indicating the involvement of hydrogen peroxide (H20 2) in the reaction mechanism. Addition of H20i suppresses Cr(V) and enhances the ·OH radical fonnation. Measurements involving N-ethylmaleimide show that the Cr(V) species, produced enzymatically by the reduction of Cr(VI) by GSSG-R, react with H2O2 to generate ·OH radicals, which might participate in the initiation of Cr(VI) carcinogenicity.INTRODUCTIONC(VI) compounds have been found to exert serious toxic and carcinogenic effects on humans and animals [1-4) and to cause mutations in bacteria and transformation of mammalian cells [5-8). In contrast, most Cr(lll) compounds are relatively nontoxic, noncarcinogenic, and nonmutagenic [9, 10]. Cr(VI) and Cr(lll) oxidation states are different in their metabolic pathways: Cr(VI) ions are rapidly transported across cellular membranes [2, 11-13), while Cr(lll) moieties do not easily penetrate cells and are not oxidized by cellular constituents [3]. Since it is known that the reduction of Cr(Vl) is required for its reaction with DNA [2], the molecular mechanisms for the intracellular Cr(VI) reduction have been the focus of studies during the past decade but the details are still not understood."

Jan 1, 1990

By R. D. Govier

The U.S. Bureau of Mines has developed a thin-film X-ray fluorescence technique to rapidly determine Cu, Ni, Co, Fe, and Cr in super alloy leach liquors. Total analysis time per sample was less than 15 min, as opposed to several hours for traditional wet chemical methods. Precision and accuracy were checked by replicate analyses of solutions similar in composition to leach liquors, whose analyte concentrations were well known. Coefficients of variation for all elements were found to be less than 2 pet. With the exception of the results for Fe, all relative errors of estimation were also found to be less than 2 pet. Bulk liquids are not introduced into the spectrometer; thus, the potential for damage to the instrument by leakage of corrosive liquids is eliminated.

Jan 1, 1989

By H. G. Iverson

The effects of adding boron and boron plus carbon to electrorefined vanadium were evaluated with respect to mechanical properties at low temperatures and response to heat treatment. Grain size was significantly decreased with the addition of 0.05 percent boron, the decreases ranging from 30 percent at 800° C to 75 percent at 1,100° C. Increasing the boron content resulted in only a small increase in strength at room temperature, but at 77° K, boron contents of 0.005 to 0.076 percent increased the yield strength of vanadium over 50 percent, from 70,000 psi to 110,000 psi. When boron and carbon were present together, the individual grain-refining effects obtained with either element were retained. Approximately a twofold increase in strength was obtained by age-hardening the alloys containing both boron and carbon. Alloys with only boron additions did not age-harden.

Jan 1, 1968