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By Michael J. Sapko, Kenneth L. Cashdollar

In This Chapter [Methane ignition as initiation source for much larger secondary coal dust explosions Rock dusting requirements to prevent coal dust explosions Dangers of hybrid mixtures of methane and coal dust] Although methane explosions are dangerous, those that involve coal dust are even more so. If exploding methane disperses and ignites the coal dust that has accumulated on the mine ribs and floor, the burning coal dust immeasurably increases the strength of the explosion. Such methane-dust explosions are prevented by inerting the coal dust in a way that prevents the exploding methane from igniting it. This chapter discusses the dust hazard and how it is pre-vented in U.S. coal mines. METHANE IGNITION AS INITIATION SOURCE FOR MUCH LARGER SECONDARY COAL DUST EXPLOSIONS The typical scenario for coal mine explosions starts with the ignition of a flammable methane-air atmosphere near the face. The turbulent winds from the primary methane explosion then disperse the coal dust. If there is insufficient rock dust (usually limestone), a secondary coal dust explosion then propagates throughout large sections of the mine. These scenarios have been studied extensively at the Bruceton Experimental Mine (BEM) and the Lake Lynn Experimental Mine (LLEM) of the NIOSH Pittsburgh Research Laboratory. The minimum quantity of methane required to initiate a coal dust explosion was studied in 1930 in the BEM [Rice et al. 1933; Nagy 1981] and then later in the LLEM, whose cross-sectional area (130 ft2) is over twice that of the BEM [Sapko et al. 1987a]. Studies conducted in the BEM closely simulated conditions that existed in operating mines in the early 20th century. The later tests in the 20-ft-wide entries of the LLEM simulated the geometries of modern mines with advanced roof support technology. The data from the BEM tests show that 13 ft3 was the minimum quantity of methane at the face that, when ignited, would disperse and ignite coal dust. In the BEM, this amount of methane was mixed with air to form a total flammable volume of about 140 ft3 of a 9% methane-in-air mix-ture. In the wider entries of the LLEM, about 37 ft3 of methane was required to disperse pure coal dust and start a self-sustained coal dust explosion. This amount of methane was mixed with

Jan 6, 2006

Demand for primary aluminum ingot increased during February, and several producers temporarily suspended new bookings for ingot. Alcoa announced that it would restart a potline at its Warrick, IN aluminum smelter by April 1, 1979, increasing the operations of that plant to its full capacity of 290,000 tons per year. At the end of February, it was reported that Alcoa would reactivate two of the seven units at its idle Point Comfort, TX smelter in May 1979, increasing the company's annual capacity by about 60,000 tons.

Jan 1, 1979

By J. E. Rourke, O&apos

This report incorporates a review of available dewatering technology and an evaluation of its relevance to surface coal mines in the Interior Province of the United States. Guidelines for the selection, design and construction of dewatering systems are included. On the basis of documented experience, candidate dewatering systems were selected and evaluated with respect to their anticipated impact on the environment and mine operations. Included in the discussion is a summary of laws and regulations which can impact on dewatering operations. Following this discussion, geologic and hydrogeologic conditions within the Interior Province are described and potential dewatering problems at surface coal mines are identified. Model mines are developed which exhibit the most difficult dewatering problems identified, and it is demonstrated how available technology can be utilized to deal with these problems. Dewatering of coarse-grained, high permeability terrace deposits might be economically feasible today. Low permeability, saturated glacial tills or lake deposits appear to be significantly outside present economic feasibility for dewatering.

Jan 1, 1979

By Fred N. Kissell

In This Chapter [Instruments available to measure methane in mines and tunnels Using a portable detector in both accessible and restricted spaces Machine-mounted monitors: placement and response time Calibration of catalytic detectors for different gases and Misinterpreting warning signs This chapter gives guidelines for methane measurement in mines and tunnels. The emphasis is on the measurement procedure and the interpretation of the measurement rather than on the instrument itself.] The failure to properly sample for methane is a major contributing factor to methane explosion risk. Sampling errors are most likely to occur at mines or tunnels where the presence of methane is not suspected or during nonroutine tasks at mines or tunnels known to have gas. More specific information on methane sampling at continuous miner sections is in Chapter 3. Chapters 4 and 5 discuss sampling at longwall sections, and Chapter 14 discusses sampling at tunnels. METHANE DETECTORS FOR MINING Many models of gas detectors are available to measure methane concentrations, as well as most of the other contaminant gases found in mines and tunnels. An example is the iTX Multi-Gas Monitor, a portable gas detector available from Industrial Scientific Corp., Oakdale, PA. This handheld instrument measures several gases simultaneously. The cost (2004) ranges from $1,300 to $2,200, depending on the number of gases measured. Similar instruments are available from other manufacturers. Most methane detectors used in mining use a catalytic heat of combustion sensor to detect methane and other combustible gases. These have been proven through many years of reliable operation. For detection of methane, proper operation of catalytic heat of combustion sensors

Jan 6, 2006

By R. V. Lundquist

A method was developed by the Federal Bureau of Mines for evaluating viscosity data from slurries obtained in leaching sinters from the lime soda sinter process for extracting alumina from aluminous silicates. The logarithm of the viscosity was observed to be a linear function with time. The slope of the plotted line provides a means for evaluating viscosity behavior in a lime soda sinter blurry and also a means for comparing gelation characteristics directly with other variables in the lime soda sinter process. This report presents one aspect of a continuing study by the Bureau of Mines on methods for treating siliceous aluminum ores. It is one of the many programs of the Bureau concerned with conservation, development, and use of our domestic minerals resources. Previous investigations of lime soda processes, both by the Bureau4-7/ and industrial concerns, have demonstrated that sintered materials containing CaO, Na2O, A1203, and S102 in various combinations exhibit a tendency to gel or set when mixed with water or other extraction solutions. Gelling prevents satisfactory recovery of alumina and in extreme cases prevents operation of an extraction plant.

Jan 1, 1960

By V. H. Gottschalk, John Grodd, R. S. Dean

"Elemantary ConsiderationsAlthough magnetiem was first discovered in and derives its name from an oxide of iron found in magnesia and called lodestone its pracical uses date from the discoveries of Faraday concerning its relation to the electric current. We may therefore start our discussion of magnetic properties with Faraday's law for relation between induced electromotive force and the change in a magnetic where e is the electromotive force induced in an electric circuit by a unit rate of change of magnetic flux N, H is the intensity of the magnetic field, S is the area enclosed by the circuit, and i an angle between H and the normal to dS. In the simplest case we could use this law to measure the strength of a magnetic field by passing it at a measured rate through a coil of copper wire and determining the,electromotive force. As a matter of practical convenience, it will be simpler to nee the total quantity of electricity produced by a change of magnetic field. For this purpose we may let i denote the strength of the electric current induced by the change of magnetic field in time in a circuit of area a and resistance R. Then the total electric quantity. Q is given. by"

Mar 1, 1934

By F. W. Horton

Investigation of an extensive deposit of chromite-bearing actinolite-talc schist situated on the summit of Casper Mountain, 10 miles south of Casper, Wyo., was one of the first projects Undertaken by the Bureau of Mines under the Strategic Materials Act (Public 117, 76th Cong., Ch. 190, 1st sess.), for which an appropriation became available August 9, 1939. During the previous summer; the Geological Survey? made? a magnetometrical survey of the area in which the schist occurred. It was exposed in several small lenses and two larger ones aggregating about 19?acres in area. Although the occurrence of chromite here had been known for many years, the only work done on the deposit was the digging of? a few shallow pits on some of the more promising outcrops. From August 23 to December 3, 1939, the Bureau of Mines investigated the larger of the two main schist bodies. Twenty-four trenches having a total length of 8,073 feet were dug across the deposit, and its subsurface extension was explored by 3,623 feet of diamond drilling. Over 32 tons of samples were shipped to the Metallurgical Division of the Bureau of Mines at Reno, Nev., for reduction, analysis, and ore testing. In all, there were 853 individual samples. Geological maps, based upon examination of outcrops, trenches, and drill cores, as well as a contour map of the area were made by the Geological Survey.

Jan 1, 1949

By Warren E. Morrison

The first major evaluation of the nation's raw materials prospects after World War II was completed by the President's Materials Policy Commission (Paley Commission) in 1952 and submitted to the President in June of that year, as a five-volume study entitled Resources for Freedom. The bulk of the report was devoted to an analysis of the past, present, and probable future of the Nation's mineral supply industries. The Commission's evaluation of the future situation regarding minerals was derived from its forecasts of the probable domestic demand for the major minerals in the 1970's. This demand analysis was made in the context of probable worldwide demand. Several crucial assumptions were made by the Commission's fore-casters. It was assumed in 1950 that the next 20 to 30 years would see no major wars and be a period of sustained economic growth. Another assumption was that the anticipated demand for raw materials must be supplied at essentially no increase in real cost in order to avoid crucial supply problems. The Commission's forecasts were derived within the context of the country's expected future rate of economic activity. The gross national product (GNP) growth to 1975 was derived from projections of the number of people in the labor force, hours of work, and an index of probable production measured per unit of labor input. It was believed labor hours would decrease and labor productivity would increase. The result was a forecast GNP growth rate of 3 percent.

Jan 1, 1970

1. Domestic Production and Use: In 1984, 12 companies operated 27 primary aluminum reduction plants, with 3 firms accounting for 57% of production. Washington, Oregon, and Montana accounted for 35% of the production; Indiana, Kentucky, Missouri, and Tennessee 25%; Alabama, Arkansas, Texas, South Carolina, and North Carolina 20%; other States 20%. Based on published producer prices, output of primary metal in 1984 was valued at $7.2 billion. Aluminum consumption by 25,000 firms was centered in the east-central United States. Packaging accounted for an estimated 35% of domestic consumption in 1984, transportation, 20%; building, 18%; electrical, 9%; consumer durables, 8%; and other uses, 10%.

Jan 1, 1985

By James C. Barker

Alluvial cassiterite concentrations are widespread in river gravel and high level terraces within the Ray River watershed. The area lies in unglaciated terrain of Alaska's northern interior. Cassiterite originates from several calc-alkaline plutons of the Ruby batholith. Extensional stresses resulted in graben-like Tertiary basins that were flooded by a 200 ft thick section of mid-to late- Tertiary basalt flows. Basalt blocked local drainages, and 50- to 100-ft of terrace gravel was eventually deposited on top of the flows. Further downwarping and eventual fluvial downcutting of the flows resulted in cycles of accelerated sediment transport, deposition, and reconcentration. Repeated erosional cycles concentrated heavy minerals and resulted in development of tin placers. Preliminary resource estimates of contained tin in Recent alluvium range from 62 to as much as 172 million lbs-Sn in 300 million yd3. Grade of about 90% of the gravels is estimated to range between 0.2- to 0.5- lbs-Sn/yd3. Associated gold and rare earth elements (REE) in monazite and xenotime may be recoverable. Most of the tin is considered a subeconomic inferred resource, though, at least some of the gravels contain 2-to 6-lbs-sn/yd3. Estimates are projected on the basis of surface sampling and several auger drill holes and are provided for the purpose of land-use management planning.

Jan 1, 2011

By J. A. Organiscak

In the United States, respirable coal mine dust exposures are limited to a 2 mg/m3 time weighted average for a working shift. If the silica content of the sample exceeds 5 percent, the 2 mg/m3 standard is reduced according to 10- (% silica) to limit silica dust exposures to 100 µg/m3. Examinations of dust sampling data collected by the federal coal mine inspectorate showed that roof bolter occupations continue to be at risk for overexposure to respirable silica dust. Testing at the Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health assessed the effectiveness of a canopy air curtain for controlling occupational exposures to respirable silica and coal dusts. Initial testing found that zones of higher velocity airflow shrank as distance beneath the canopy increased. This suggested that protection from occupational dust exposures would likely decrease as distance beneath the canopy increased. Further testing revealed that coal dust reduction efficiencies were most affected by changes in interference air velocity and, to a lesser extent, changes in canopy air quantity. However, respirable silica dust percentages under the canopy were not affected by such changes and, in fact, were not significantly different from silica percentages measured outside the canopy. This implied that the air curtain was equally effective on both respirable coal and respirable silica dust particles.

By A. S. Swanson

The Babb fault vein in Crittenden and Livingston Counties, Ky. (fig. 1), is one of an extensive series of such veins in the Western Kentucky and Southern Illinois fluorspar district. First operated in 1904, the production to May 1, 1944, was estimated at 143,000 tons of fluorite ore. There are five mines (fig. 2) on the Babb fault zone - Guill ,Kentucky Babb, Delhi-Babb, Eagle-Babb and Howard-Barnes. The Bureau of Mines developed four of these properties by core drilling from July 9, 1943, to May 1, 1944. During that period a total of 8,177.8 feet of diamond drilling was completed in 28 holes.

Jan 1, 1950

This report summarizes the work performed and results achieved on the above contract from October 18, 1971 through July 14, 1972 under Phase II, Task 1: Detailed Design of Prototype and Task 3: Supporting Experimental Investigation. Operation and Service Manuals resulting from Task 3 are submitted under separate cover as are detailed design drawings and specifications, prepared under Task 1. Both items accompany this report. This report also includes (A) an estimate of the cost of construction, (B) a description covering the use of the equipment, and (C) a proposed test plan to demonstrate performance of the equipment in both the laboratory and a mine.

Jan 1, 1972

By H. John Head, Fred N. Kissell

In This Chapter [Gas reports from around the world Regulations for gassy mines in the United States Differences between metal/nonmetal mines and coal mines Monitoring for methane and taking action Diluting methane with additional ventilation Eliminating ignition sources What experienced mine operators say about methane control and Looking for methane when starting a new mine or expanding an existing mine] This chapter gives guidelines for preventing methane gas explosions during metal and nonmetal mine development and subsequent production operations.3 Emphasis is placed on recognizing the differences between coal mines, where the potential for methane hazards is relatively well understood, and metal/nonmetal mines, where methane may accumulate unexpectedly. Also, interviews with experienced mine operators add much to a complete understanding of what must be done to address methane problems in metal/nonmetal mines. METHANE GAS IN METAL/NONMETAL MINES Gas reports from around the world. The presence of methane gas in metal/nonmetal mines around the world is more common than one might imagine [Edwards and Durucan 1991]. For example: • The former Soviet republics have occurrences of methane and hydrogen in apatite, gold, and diamond ores, where solid or liquid bitumen occurs in the rock. • Scandinavian iron ore deposits include methane and other hydrocarbons in boreholes that intersect pitch and asphalt within the deposits, and methane and nitrogen in boreholes and fissures in arsenic and sulfide ores.

Jan 6, 2006

By R. Demont, A. Pranesh, S. Rakheja

Ethical concerns of in-vivo procedures and poor repeatability of non-invasive techniques have been major limitations in estimating vibration-induced spine loads through experiments. The biodynamic models of seated human body exposed to whole-body vibration (WBV) have evolved for defining the frequency-weightings, enhancement of human responses to WBV, and developing anthropodynamic manikins for seating assessment activities. The widely reported mechanical-equivalent models, solely based on through- or to-the-body biodynamic response functions, do not seem to resemble the biomechanical structure and do not yield information on the dynamic loading and deflections of segments of concern, namely the spine. On the other hand, biomechanical models with representative anatomical structure and anthropometry are being attempted to simulate segmental movements and the coupling effects, using Finite elements (FE) or multi-body dynamics (MBD) formalisms, which could provide important insights into the inter-vertebral forces [1]. While the FE models pose considerable complexities primarily related to characteristics of the bio-material properties, the MBD technique with discrete rigid bodies offers the flexibility to create multi-segment models with relative ease and lower computational cost. In this study, a preliminary multibody dynamic model of a seated human body exposed to WBV along the vertical direction is formulated using MSC/ADAMS software. The model validity is demonstrated by comparing selected responses with the available measured data. Methods The seated human is represented by nine rigid body segments, including: head, neck, thoracic and lumbar torso, pelvis, hands and thighs, as shown in Fig. 1. The rigid bodies are coupled through different rotational and translational joints, some of which are force elements to allow vertical translations and sagittal–plane rotations of the segments. The measurements of transmission of vertical vibration through-the-body generally require subjects to voluntarily maintain a vertical head position to reduce head-accelerometer orientation errors. The head–neck–shoulder joint is thus considered to be rigid. The shoulders are assumed to be rigidly attached to the thoracic segment. The torso is made up of three (upper, middle and lower) segments connected by visco-elastic revolute and translational joints to permit relative pitch and vertical motions. The forces and torques generated by the joints are derived assuming linear stiffness and damping properties, which were identified from published studies. The pelvis is connected to the rigid seat by similar elements representing the visco-elastic properties of the buttock tissues. The two thighs are rigidly connected to the pelvis, while the segment masses are chosen from the anthropometric data for the 50th percentile male subject. The initial model parameters for the joints were obtained from [2]. The model was analyzed to determine the force-motion relationship at the buttock-seat interface expressed in terms of

Jan 6, 2006

Between 1985-1986, the Bureau of Mines reviewed the mining history and minerals information for areas in and near the San Isabel National Forest to appraise the mineral resources present and determine the types of deposits, and their location in the Forest, that could be mined economically if sufficient demand and metal prices existed. The two major metallic deposit-types that are of national mineral resource significance within the Forest are stockwork- molybdenum (with tungsten and tin) and carbonate-replacement zinc-lead-silver deposits. Historically, small gold placers, gold-quartz veins, silver-quartz veins, skarn iron and copper deposits, volcanogenic copper-zinc-precious metal deposits, and base- and precious-metal veins have been mined. Barite, carbonate rocks, gypsum, other non-metallic deposits, and pegmatites, have also been mined. Sand and gravel, present in large volumes, occurs along and has been mined outside the Forest along the upper Arkansas River valley. Turquoise and gemstones are present in small amounts and are of interest to collectors and jewelers. Geologically, sediment-hosted uranium and copper are present in small occurrences but no resources have been identified. Geothermal resources are related to the Rio Grande rift which parallels the central part of the Forest. Four hot spring areas are present - two of these are within the Forest. Because of the low power requirements of the region, and the presence of other generating facilities, these geothermal resources have had only limited local use. Evaluation of mine models that may be found in the region show that base-metal deposits require a high precious-metal component to be economic. Although molybdenum can be produced at economically competitive prices, there is little demand for the product. Capital costs to start new molybdenum mines would be very high and it is not likely that new mines will be put into production in the near future.

Jan 1, 1989

During the period January 1, 1977 through July 31, 1977, 5 percent (264,000 tons) of U.S. capacity was closed due to power curtailments in the Pacific Northwest because of the shortage of water. During July, one plant in Tennessee cut production by 50,000 tons annually due to a power reduction by the Tennessee Valley Authority. Full capacity production was resumed at a West Virginia smelter during September. If demand for aluminum is strong it seems likely that aluminum supply during the remainder of 1977 and in 1978 will be tight. The price was increased 3¢ per pound to 51¢ per pound effective March 28, 1977, and by an additional 2¢ per pound to 53¢ per pound, effective July 5, 1977. New projects and expansion of existing facilities are planned by Australian aluminum companies over the next 2 to 3 years. The companies listed have committed themselves to spending approximately A$801 million: Alcoa of Australia Ltd. -New alumina plant at Wagerup, south of Perth. Darling Ranges bauxite is located near the proposed project. A$650 million. Coma 1 co Industries Pty. Ltd. -Increase bauxite mining capacity and upgrade or replace other facilities at its Weipa mines on Cape York Peninsula region of Northern Queensland. A$81 million. Alcan Australia Ltd. -Expansion program that will increase capacity of the Kurri Kurri aluminum smelter north of Sydney about 50 percent, and improvement of other facilities at the plant. A$70 million.

Jan 1, 1977

By N. Dixon

This report summarizes all work performed under U.S. Bureau of Mines Contract J0377014, "Development and Evaluation of Noise Control Techniques for Taconite Processing Equipment." Three areas of taconite processing equipment, grinding mills, fine screens, and crusher screens have been investigated. Extensive noise and vibration measurements have been made on grinding mills in which the process parameters that affect mill noise have been identified, and the level of shell impact noise around the mill defined. A multiplexing telemetry system was used to obtain shell vibration measurements from a rotating mill. Mill noise control methods were investigated and a partial mill barrier was built and tested on a semi-autogeneous mill. A noise reduction of approximately 3 to 6 dBA was achieved on the falling side of the mill. The use of rubber mill liners on autogenous mills has been evaluated. The noise sources on fine screens have been quantified, and noise control treatments developed. Noise reductions of 11 to 13 dBA were achieved at positions around the fine screen and some in-service testing has been done. Noise measurents of crusher screens were obtained and noise control through resilient screen decks appears to hold the most promise. Additional benefits might be lower life-cycle cost, since the service life of resilient decks is claimed to be longer than steel.

Jan 1, 1983

By A. L. Service

In 1965 the Western phosphate industry ranked third after Florida and Tennessee in total mine and marketable production of phosphate rock and phosphate rock products. It has become an important regional industry and, since the close of World War II, it has become important in the national phosphate economy. This report includes an evaluation of the trends and outlook for the Western phosphate industry through 1975 as part of the Bureau's program to determine the rate at which the Nation's mineral resources are being utilized. The first part of this report is concerned with the relationship between the Western phosphate industry and that of the United States and the world. It describes the principal phosphate deposits and discusses production, export, and import of phosphate rock and marketable products. The second part of the report is concerned with the Western phosphate industry and discusses trends and outlook through 1975. Projections for the utilization of phosphate rock, phosphate fertilizers, and elemental phosphorus have been developed and extended through 1975 in an effort to provide data and information pertaining to the rate of depletion of the Nation's phosphate resources.

Jan 1, 1967

By C. H. Riggs

This petroleum-engineering study of the Healdton oil field in Carter County, Okla., describes the geology and production history of that field and estimates the oil reserves that could be produced by efficient secondary-recovery methods. The Healdton field, in western Carter County approximately 20 miles west of Ardmore, Okla., was discovered in 1913 and was one of the early important oil-producing areas in the State. Although the volume of oil recovered from the Healdton sands has been comparatively high, studies show that a large reserve remains in the pressure-depleted sand, which can be recovered by efficient water-flood operations. In making this study of the Healdton-sand reservoir, the writers utilized many data already available in company and Government offices. Most of the fluid samples were collected by Bureau of Mines personnel and analyzed in the Bureau's laboratories at Bartlesville, Okla.; but other data, including logs, core analyses, and production records, were obtained from outside sources. These data were examined critically but were not verified, and possible errors in the original data may be reflected in the conclusions. In this study, attempts were made to consider only those aspects of the available information that would contribute to a clear and concise engineering report on the Healdton-sand reservoir. Other phases of the data, as well as those concerning associated reservoirs, were eliminated from consideration as being irrelevant to the particular problem. Cores and drill cuttings of the Healdton sands were analyzed and studied to determine the nature of the reservoir rocks. Analyses of samples of produced oil, water, and gas were studied to fix the different types, the limits of their occurrence, and the suitability of different waters for injection into the Healdton sands. Records of oil, gas, and water produced and of gas and water injected were studied to interpret the production behavior of the field and of certain individual leases. Theoretical calculations were made to predict the probable water-flood behavior and oil recovery, at constant water-injection rates, for individual sands on two leases.

Jan 1, 1953