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By J. F. Shaw

MINE fires are usually extinguished by constructing seals in the approaches to the areas to exclude air from the fire areas, which smothers the fires in an oxygen-depleted atmosphere. Seals should be substantially constructed and made as nearly airtight as possible and should be provided with a sampling pipe so that samples of the atmospheres behind the seals may be collected at regular intervals. Methods of constructing seals and of sampling and analysing mine atmospheres are fully described in Bureau of Mines publications. (1, 2). Information obtained on the composition of atmospheres behind fire seals is helpful in determining if a fire has been extinguished or if there is any danger of an explosion when a fire area is being sealed or unsealed. The progress of a mine fire can best be determined by studying percentages of carbon dioxide, carbon monoxide, and hydrogen in the atmosphere behind the seals. Hydrogen will be formed in a bituminous- or subbituminous-coal mine when the temperature exceeds 480° F. and in an anthracite mine when the temperature exceeds 660° F. (3). Carbon monoxide and carbon dioxide are both products of combustion of coal, wood, or other organic compounds. The presence of carbon monoxide has long been accepted as an indication of a mine fire. A sealed fire area should not be reopened until the carbon monoxide has disappeared. Trends in the percentage of carbon dioxide are also useful in determining the status of a mine fire. Carbon dioxide is sometimes liberated by rock strata. In this case, carbon dioxide in the atmosphere behind a seal will be from two sources-the rock strata and the fire. When the, fire is extinguished, carbon dioxide will be liberated from only I source, the rock strata, and when the percentages of carbon dioxide are plotted, the slope of the curve will not be as steep as when this gas was being liberated from 2 sources. If the only source is the fire, the percentages of carbon dioxide will gradually decrease after the fire has been extinguished. By studying analyses of a mine-fire atmosphere, it is possible to determine if the atmosphere is explosive; if the mixture is capable of becoming explosive when mixed with air; and if the mixture can be made nonexplosive or be prevented from becoming explosive by being mixed with an inert gas. These factors can be computed mathematically or determined graphically. The mathematical calculations advanced by Ash and Felegy (7) are discussed, and graphical solutions of their equations are presented. It is believed that the graphical solution will be extremely helpful in determining the characteristics of a mine-fire atmosphere when fighting a fire, because the results can be obtained in a matter of minutes, and there is less likelihood of an error being made under the stress incident to control efforts. The experimental and theoretical work upon which the formulas are based have been adequately described and are not discussed at this time (5) (6).

Jan 1, 1955

By W. C. Sanborn

The Bureau of Mines program of investigation and development of domestic mineral deposits had as its wartime objective the most effective immediate utilization of these resources in the interest of National security. Since the war, the results of individual projects are being prepared for publication as rapidly as practicable. Numerous chromite deposits were examined, among them those of the French Hill Mine in northern California. Situated 16 miles east of Crescent City, 76 miles from the nearest railroad shipping point at Grants Pass, Oreg., this deposit had a recorded yield of about l4,000 tons of metallurgical-grade chromite to the end of 1943. By the end of 1946, total production was more than 25,000 tons, averaging 43 percent Cr2O3, with a chrome:iron ratio of about 2.5:1.

Jan 1, 1948

By P. M. Sullivan

At its College Park Metallurgy Research Center in Maryland, the Bureau of Mines has installed and is operating a 5-ton-per-hour pilot plant for continuous mechanical separation of values contained in raw urban refuse. The entire sys tern was assembled using commercially available equipment. The process relies on multistage processing including shredding, air classification, screening, gravity concentration, and electrostatic separation. Compactor trucks deliver raw refuse collected along typical routes in metropolitan Washington, D.C., to the pilot plant. The loads are separated into concentrates of (1) light-gage iron, (2) massive metals, (3) glass, (4) putrescibles and waste combustibles, (5) paper, and (6) plastics. While some refinements remain to be made in the processing system flow-sheet, the data obtained to date have been highly encouraging, indicating favorable economics for commercial-size plants.

Jan 1, 1973

By John C. Edwards, Gene F. Friel, John J. Opferman, Robert A. Franks

As the use of deep -rut mining increases, there - expected to be a greater demand for methane (CH,) measurement devices capable of scanning working faces al depths in excess of 10 m to alert mine personnel of hazardous concentrations of CH and to satisfy regulatory requirements. Remote optical devices offer the most promise to satisfy these objectives while the operator remains safely under supported roof. A second¬-generation remote Optical methanomeor (ROM) bas been designed and Is undergoing laboratory evaluation at the National Institute for Occupational Safety and Health. It operates on the principle of differential absorption of the "u;' fundamental absorption band of CH, centered at 3.31 um in the infrared region of the spectrum. The new instrument differs from the previous prototypes by the replacement of the two hand pass differential absorption technique of measurement with a single filter gas correlation technique and a refinement of the amplifier and gating circuitry used within the unit. This results in a more accurate isolation of the CH, spectral absorption band centered at 3.31 um. A specially designed 0.4m-diam variable-length gas mixing tunnel was constructed and instrumented with CH4 sampling capability to calibrate the ROM. Experiments have demonstrated the ability of the detector to respond to various conditions of CH, (pn•m) at distances as great as 12 m. Thermal radiation generated within the instrument is the controlling factor in the drift of the output signal nod, therefore the reliability of the instrument. Several approaches to reduce this extraneous radiation interfering moth the infrared detector, described, such as the installation of a fan in the instrument and thermoelectric coolers on the detector's beat sink. Implementation of this technology will significantly improve the safely of miners.

Jan 5, 1997

By H. D. Jacobs

The Bureau of Mines developed a concentration method to upgrade and utilize marginal natural or direct-shipping iron ores and fine-grained lean iron ores. Presently these ores receive little beneficiation and accordingly have low iron-silica (Fe-Si02) ratios. Ore samples were roasted with equal weights of solid reductant at 1,100° C for 1 hour to metallize the iron and for an additional hour at 1,200° C to promote grain growth. Concentration was effected by crushing and screening techniques and/or wet magnetic separation. Sized concentrates (minus 4 plus 35 mesh) derived from crushing-screening processes contained from 80 to 85 percent iron that was 90 percent metallized. Iron-silica ratios as high as 12:1 and iron recoveries from 75 to 94 percent were obtained. The sized concentrates were judged suitable for use as blast furnace feed. Minus 200-mesh metallized concentrates derived from roasted minus I-inch plus 8-mesh ore fractions and magnetically concentrated contained 90 percent Fe and 4 percent or less Si02, chemically qualifying them as feed for electric furnaces. Roasting minus 8-mesh ore with hydrogen, then magnetically concentrating it, produced iron concentrates containing 57 percent to 67 percent Fe and 3.6 percent to 8.4 percent Si02. The concentrates having Fe-Si02 ratios ranging from 8:1 to 12:1 were considered adequate for use as blast furnace feed. Overall iron recoveries for the 12 ores tested ranged from 56 percent to 94 percent with an average iron recovery of 86 percent.

Jan 1, 1969

Capture airborne coal dust generated by a continuous mining machine to reduce workers? dust exposure and to improve face visibility. Approach Develop a low-profile dust collector system which can be mounted on the boom of a continuous miner. How It Works When coal is mined with a milling head continuous miner, a substantial amount of coal dust (respirable and non-respirable) escapes the dust suppression sprays at the cutter head. This can cause poor visibility around the cutting head and can expose the workers to high levels of respirable dust. A practical means of removing this dust is with a scrubber mounted directly on the mining machine. Under a Bureau of Mines contract, a low-profile, machine-mounted dust collector (MMDC) was developed to avoid adding extra height to the continuous

Jan 1, 1983

By R. M. Santmyers

Umber and sienna, like ocher, are naturally occurring mineral pig- ments composed largely of clay permeated with hydrated iron (ferric oxide), but they differ from ocher in that they also contain hydrated manganese oxide. The presence of manganese accounts for their browner color. In addition to silica and alumina (clay) and the coloring oxides of iron and manganese, these pigments often contain lime, barium, and other metallic salts as impurities. Sienna most nearly approaches ocher in chemical composition, and the chief distinction is its physical character. It grades into ocher with de- creasing iron content and into umber with increasing manganese content. Sienna is translucent rather than opaque and is more of a stain than a pigment; as the iron oxide content is rather high (often 60 to 80 per cent), the color is strong and rich and varies from pure brown to reddish brown. This pigment raw sienna, terra di Siena, and Italian earth. is known under several names: Burnt sienna is a pigment of an orange-brown tint made by cautionsly calcining raw sienna. It is divided into two grades; American, and Italian burnt sienna. American burnt sienna is a reddish-brown pigment containing from 25 to 60 per cent iron oxide (Fe2O3). One grade, found in Pennsylvania, analyses as high as 80 per cent and is mown as double strength sienna. Italian burnt sienna is a pigment generally containing more iron than the American product, averaging 60 to 75 per cent iron oxide.3 American pig- ments of the same iron content differ materially in shade, having a Havana- brown color, whereas the Italian is more of a maroon. Italian siennas when tinted with 20 per cent of white, show a bluish tint, whereas American siennas yield a brownish or yellowish hue. Raw umber, also known as Turkey umber, Levant umber, and terra ombra, is a greenish to yellowish brown siliceous and ferruginous earth, containing a considerable proportion of one or other of the higher oxides of manganese, Mng04 and MnO2." It is similar in many respects to raw sienna except that it is much coarser and contains more manganese oxide. All umbers contain over 5 per cent of manganese dioxide. Like sienna, umber is a permanent pigment, not being injured by light or by impure atmospheres. Burnt umber (velvet brown, chestnut brown, etc.), results from the calcination of raw umber. The color is much richer and warmer than that of the raw umber. The colors are equally permanent and can be used in conjunc- tion with all other durable pigments.

Sep 1, 1931

By D. N. Nilsen

The Bureau of Mines is developing a method to recover Ni, Co, and Cu from laterites containing less than 1.2 pct Ni and 0.25 pct Co. The method consists of the following basic unit operations: (1) reduction roasting, (2) leaching, (3) solvent extraction, and (4) electrowinning. The method reflects three Bureau of Mines objectives: (1) recovery of critical minerals that are domestically in short supply from low-grade domestic laterites, (2) lower processing energy requirements, and (3) solution recycling. This report deals with the extraction of cobalt and the preparation of a suitable cobalt electrolyte by solvent extraction from liquor produced by this method. Nickel and copper are coextracted with LIX64N from an ammoniacal ammonium sulfate leach liquor containing about 1.00 g/l Ni, 0.30 g/l Co, 0.03 g/l Cu, and 0.02 g/l Zn. Cobalt (III) in the nickel-copper barren raffinate is reduced to cobalt (II) with cobalt metal. Reduction of cobalt (III) to cobalt (II) greatly aids subsequent extraction. Commercially available XI-51 extracts about 94 pct of the cobalt from the treated raffinate in one stage in a laboratory mixer-settler continuous circuit. Ammonia loaded on the solvent is removed in two washing steps. About 94 pct of the cobalt then is stripped from the XI-51 in one stage with spent cobalt electrolyte containing about 77 g/l Co and 18 g/l sulfuric acid (H2S04), Electrolytes containing less H2S04 also may be used. Preliminary data indicate that coextracted zinc may be removed from pregnant cobalt eletrolyte containing 3 g/l or less H2S04 with di-(2 ethylhexyl) phosphoric acid (D2EHPA).

Jan 1, 1980

By Fred C. Turin, Jasinder S. Jaspal, Alan G. Mayton, William J. Wiehagen

Dump site injuries occur in all major mineral industries. Working in elevated areas near an edge is a common hazard for operators of off-highway mobile mining equipment. In this Information Circular (IC), serious injuries involving haulage trucks working at dump sites are examined for the period 1988 to 1997. Data were acquired from injury reports gathered by the Mine Safety and Health Administration (MSHA). The IC is organized into three sections. The first presents an overview of the frequency and severity of injuries. The second analyzes injury characteristics using MSHA-defined data fields and author-defined injury classifications. Key findings are discussed in the third section. In summary, 370 serious injuries were identified that involved trucks at dump sites, of which 26 were fatalities. Although haulage truck activities at dump sites resulted in a small proportion of the total number of injuries at surface mines, these injuries were much more likely to result in death or significant amounts of lost time than most other surface mine injuries. These findings support the belief that haulage truck activities at dump sites are worthy of continued study by those interested in improving the health and safety of workers at surface mines.

Jan 3, 2001

By William A. Beck

The K.T. Dome Mine in Owen and Henry Counties, Ky., has been operated intermittently under several different owners since the early nineteen hundreds. No record of total production is available, but it is said that during 1943 and 1944, while being operated by the Twin Valley Mining Co., 30 cars of zinc concentrates and 10 cars of lead concentrates were shipped. The vein can be traced for about 10 miles along the strike from Lockport, Henry County, to Big Twin Creek in Owen County. It pinches and swells both vertically and horizontally and is reported to average 20 inches in width. In order to develop additional reserves on the property, the Bureau of Mines drilled four holes on the south extension of the vein. Drilling disclosed that the vein dips to the west on the south side of the Kentucky River and is continuous along the strike and in depth. However, the extent of mineralization in the vein varies widely.

Jan 1, 1949

By Richard J. Mainiero, Eric S. Weiss

This project investigates the behavior of blast waves from the detonation of high explosives in an underground mine. A series of explosive tests was conducted in the underground and surface facilities at the Bureau of Mines' Lake Lynn Laboratory to evaluate the potentially dangerous effects of blast waves produced by open shooting, blown out holes, or accidental detonations of explosives. Shots of C4 and TNT were fired at the dead end of a 6 ft high by 20 ft wide entry, at the intersection of two entries, and on the surface. C4 and TNT were chosen for this research because they exhibit very consistent performance. Behavior of the blast wave was evaluated through recording of the pressure as a function of distance from the explosive detonation. For both explosives, C4 and TNT, peak pressure decay with travel down the entry was inversely proportional to distance to the 0.9 power. When comparing pressure measurements at 200 versus 100 feet from the detonation; at 200 feet the pressure would be 1/2 0.9 or 54 percent of that measured at 100 feet. By comparison, peak pressure for a surface shot exhibits a decay with distance to the -1.6 power, yielding a pressure at 200 feet 1/2 16 or 33 percent of that measured at 100 feet. This result confirms that the blast wave from detonation of an explosive in an underground mine maintains its force for a greater distance than would be the case on the surface. Table and figures follow the text.

By John R. Reeves

The development of an new industry, which must prepare its marketable products at or near the source of the raw material, and ship them to a market which may cover half a nation, is more or less influenced by a number of natural and cultural conditions such as (1) location of plants with respect to a large market, (2) climatic conditions, (3) transportation facilities, (4) labor supply, and (5) water supply. An effort is made in this pager to give in detail a number of the more important of these conditions as they affect, either favorably or unfavorably, the development of the oil-shale resources of southeastern Indiana. The utilization of the New Albany formation for the production of oil will be similar to a large scale low-grade ore proposition in which the raw material can be obtained in very large quantities at a relatively low cost. It appears, therefore, in considering the value of this shale or its economic position in relation to other oil shales, tie cost of mining and preparation for the retort are of prime importance.

Jan 1, 1923

By Robert J. Anderson

"Introductory Statement:In melting the nonferrous metals and alloys for foundry and rolling-mill work, even with the best practice, there is always a loss, due principally to oxidation. Melting losses are a serious source of financial loss in brass and bronze practice, but they are especially serious in the case of aluminum and its light alloys because of the relatively high price of aluminum. The indications are that the melting losses in many aluminum foundries of the United States are at times high, and in some plants (especially where certain furnaces are used) they are entirely too high when compared with the average practice. The fact that the oxidation losses in melting aluminum and its light alloys are high is well known, but it is doubtful whether the factors governing the most suitable methods of melting for a minimum of dross are equally well known. The metal losses involved in melting are worthy of especial attention now because of the rapidly growing importance of the aluminum industry.Factors in the operation of furnaces which affect metal and fuel losses:The essential requirements in the commercial melting of any metal or alloy are that the melting losses should be low, the melting should be rapid, and the melting cost should be low. Certainly it may not be possible to obtain these requirements in any furnace selected at random, and it follows that the design and the operation of furnaces for melting different metals are subjects that warrant the most extensive study and tests. As a general rule, in the industrial operation of furnaces, run on aluminum and aluminum alloys, an effort is made to keep the dross and oxidation losses as low as possible. In attempting to hold dross losses low, numerous factors involved in metal melting may be overlooked, or at least disregarded, and the net practical result may be that the furnace is exceedingly wasteful of fuel. In the case of aluminum and its light alloys, the effect of increasing the temperature of melting, at least in an atmosphere containing free oxygen and nitrogen, is to increase the net melting loss."

Apr 1, 1921

By Perry G. Cotter

As a portion of a general program for the synthesis of hard materials, a method was sought by which the hardness and density of tungsten carbide (WC)-cobalt compacts could be increased. It was demonstrated by Cotter that these improvements in quality could be made by employing an electric-resistance sintering process in which heat and pressure are applied simultaneously to presintered compacts composed of powdered tungsten carbide and cobalt. This conclusion was based on tests of material prepared by Cotter on welding equipment in use at the U. S. Naval Engineering Experiment Station, Annapolis, Md., and at Rensselaer Polytechnic Institute, Troy, N. Y. Rockwell-hardness tests made at Norris and core-drilling tests made at the Mount Weather Station of the Bureau of Mines indicated that, for some purposes, carbide material made by this process might be superior to the chemically analogous commercial products prepared by ordinary sintering methods. A program to develop optimum conditions for the electric-resistance sintering of tungsten carbide-cobalt compacts was initiated. The program was followed by a systematic evaluation of the hardness and density of compacts prepared by this method along with a series of carbide compacts furnished by various manufacturers. This paper presents a description of the electric-resistance sintering of tungsten carbide-cobalt compacts and the results of comparative physical tests.

Jan 1, 1955

By N. E. Hanna

To be authorized for use in coal mines, explosives and blasting devices must pass certain safety tests prescribed in schedule 1F,3/ on the basis of extensive practical and theoretical research by the Explosives Testing Station of the Federal Bureau of Mines. An explosive or blasting device that passes these tests is placed on the active permissible list. As this list is constantly revised, it has been the practice of the Bureau of Mines periodically to publish the names of explosives and blasting devices that have been added to the active list, as well as those that have been transferred to the inactive list; changes in brand names also are reported. This circular covers all permissibles including additions, transfers, and changes made between December 31, 1945,4/ and December 31, 1951.

Jan 1, 1952

By Eugene Baker, Joseph Cervik, Albert Sainato

In Europe, water infusion is used widely to reduce generation of respirable dust during mining. Its use in the United States is limited to a few plow operations in the Pocahontas No. 3 Coalbed. This Bureau of Mines report describes the technology for infusing water in to a longwall panel and reports the results of a recent demonstration in the Lower Sunnyside Coalbed that achieved dust reductions averaging 58 pct. Because water infusion increases moisture content of the coalbed, face air velocities in excess of 500 ft/min (2.5 m/s) are possible, further diluting dust levels before dust entrainment occurs. An economic analysis shows a 23-pct reduction in operating costs when coal production is increased by changing from unidirectional mining to bidirectional mining with water infusion.

Jan 1, 1983

By l.J Prosser

from 1990 to 1996, 16 states reported 92 injuries from falls of roof, rib or face in the more than 90 underground stone mines in the United States (Fig. 1). Missouri, Pennsylvania and Kentucky accounted for 48% of the total number of injuries (Fig.2). Of this total, 11 miners were killed. Of the 11 fatalities, 10, or 91 %, were associated with unrecognized loose or failed rock within the roof beam. Additionally, unrecognized roof beam failures resulted in a majority of the falls of ground injuries occurring in underground US stone mines from 1990 to 1996.

This chapter presents data on occupational exposures from several sources. Data from compliance samples obtained by MSHA inspectors are presented in table 6-1 for coal mine dust and silica dust, and in tables 6-2 through 6-6 for metal fumes. Since these samples were taken for compliance monitoring rather than as part of a survey of the industry, it is difficult to predict how well they indicate actual exposures for all mining operations. In the coal industry, 7.8% of all respirable dust samples during 1986-1995 were above the permissible exposure limit (PEL). Of silica dust samples obtained during the 10-year period, 23.7% were above the PEL in coal, 16% in metal, 10.8% in nonmetal, 9.1% in stone, and 7.6% in sand and gravel. Of metal fume samples, silver samples showed the largest percentage above the PEL-approximately 48% of samples in both metal and nonmetal. Tables 6-7 and 6-8 present data on noise exposures from the MSHA "dual threshold" survey, which was published in the Federal Register [61 Fed. Reg. 66347 (1996)] as part of a proposed rule change for occupational noise exposure in mining. This study examined a group of samples obtained during 1991-1995 and compared the percent of samples that were above two separate specified limits. The first limit was the current noise standard, a time-weighted average of 90 dBA, calculated to include only exposures at 90 dBA and above. The second limit was a time-weighted average of 85 dBA, calculated to include exposures at 80 dBA and above. Tables 6-8 and 6-9 refer to musculoskeletal overload conditions examined in the National Occupational Health Survey of Mining (NOHSM) [NIOSH 1996]. Table 6-8 shows the operational definitions for each condition; table 6-9 shows the percentage of the workforce potentially exposed, by commodity. Across all commodities, a large proportion of workers were exposed to musculoskeletal overloads due to positioning of the neck and back; positioning and motion of the forearms, arms, and shoulders; heavy lifting; and positioning and movement of the lower limbs. The recorded overloads were defined in the survey and did not exceed any NIOSH, MSHA, or OSHA guidelines for musculoskeletal overloads. Further information on this survey appears in appendix A.

Jan 5, 2000

By A. E. Raddatz

The Bureau of Mines has determined the electrochemical rate of anodic dissolution of vanadium metal in a VC12-VC13-NaC1 electrolyte at 860' C for the purpose of elucidating the reaction mechanism. Rate measurements were carried out with the help of specially designed equipment capable of continuously recording the weight loss experienced by a cylindrical vanadium anode immersed in the molten salt electrolyte while a constant current is maintained through it. The rate is expressed as a function of current density and VC13 concentration, and the reaction is interpreted in terms of an adsorption mechanism. Multiple regression analysis of the data gave the following rate equation: Rate x 104 (g.cm-2.sec-1) = -0.38 + 2.64 current density (amp-cm-2) + 0.69 log, (mole-percent VC13).

Jan 1, 1974

By J. Drew Potts

The U.S. Bureau of Mines identified respirable dust sources and controls on four continuous auger mining sections, two with relatively low dust levels and two with high levels. Factors adversely affecting dust levels included auger equipment design, continuous haulage, and low seam height. Dust controls included ventilation practices and spray systems. Maximizing airflow seemed to reduce dust levels most. Air leakage and shock loss can be reduced by constructing stoppings with brushed-on mortar containing fiberglass and by keeping areas between curtains and ribs free from obstructions and storing equipment not essential for face activities in outby crosscuts. Curtain configuration, setback distance, and installation can also affect dust levels. Use of both blowing and exhausting curtains is the most effective configuration. Setbacks from the face should not exceed 15 ft. Installing brattice curtains at least 5.5 ft from ribs, when entries are 26 ft wide, minimizes velocity head. Installing curtains tightly against the mine roof and floor helps maintain a forward airflow movement in the center of the mine heading; curtain overlap can create a tighter seal. The wet-auger spray system also effectively controls dust, provided the mine is already exercising good ventilation practices.

Jan 1, 1989