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The current procedure for measuring the concentration of respirable coal mine dust is as follows. Each filter is preweighed by the filter manufacturer to ±0.1 mg. Following sampling with the Coal Mine Dust Personal Sample Unit (CPSU) at 2.0 L/min, the filter with coal mine dust is sent to MSHA for weighing. The current MSHA procedure for weighing respirable dust samples uses a Mettler Model AE163 analytical balance in conjunction with an automatic weighing system with a precision of ±0.02 mg [Tomb 19901. Each balance is calibrated twice per day. Quality control for the automatic weighing system includes the systematic weighing of one in eight filters on a second Mettler AE163 balance. Tolerance is set at ±0.1 mg between the two weighings of the same sample. Weights are truncated at the 0.1 mg level (e.g., 3.457 mg is truncated to 3.4 mg) [Bowman et al. 19851. The difference of the two truncated weights is then recorded as the weight of coal dust deposited. The respirable concentration (mg/m3) is computed by multiplying by a correction equal to 1.38 and dividing by the volume of air sampled (2.0 L/min x sampling time [min]).

Jan 1, 1997

By Homer J. Ballinger

The Krueger property was examined by an engineer of the Bureau of Mines in September 1943. The records of 23 old drill holes indicated an appreciable body of ore without delimiting the deposit. It appeared that additional drilling might increase this reserve sufficiently to justify mining. Accordingly, the Bureau of Mines drilled 5 churn-drill holes and 19 diamond-drill holes on the Krueger tract. The last of these holes concluding the Bureau?s project was completed in April 1947.

Jan 1, 1948

By John W. Chandler

The property of the lava Cap Gold: Mining Corporation is in the Nevada City-Grass Valley mining district about 5 miles east of Crass Valley, Calif. At present (July 1940) the plant is mining end milling about 390 tons of gold-silver ore a day; about 310 men are employed. This paper describes the mining methods used and presents mining costs for 1939, when 60,704 tons were mined by cut-and-fill stoping and 55,676 tons by square-setting.

Jan 1, 1941

By D. J. Bauer

A solvent-extraction system employing selective stripping of a pre loaded organic phase was investigated for recovering Sm203 from a light-group rare-earth mixture. The samarium concentrated in the organic phase, and a >99-pct-pure samarium oxide product was obtained at 76-pct recovery in a 20-stage operation using di(2-ethylhexyl) phosphoric acid (EHPA) as the organic phase. The stripping agent was a 1.5-pct hydrochloric acid solution containing 200 g NH4C1/1.

Jan 1, 1972

By Graham W. Marks, RALPH MILLS, FRANK COSSEY

To determine the focal length of lenses or the performance of lens systems before mounting them permanently , it is desirable to have a device in which one or more lenses can be mounted easily and their positions relative to a light source and screen changed readily . We have designed and constructed such an optical bench and lens holder . The bench is similar to that of Houstoun5/ but has been modified , whereas the lens holder is , we believe , a new design .

Jan 1, 1948

1. Data from the Mine Safety and Health Administration (MSHA) indicate that a total of 44,015 employees worked in underground mining locations in 2003, corresponding to 44,778 full-time equivalent (FTE) workers. • Ninety percent of underground employees (n = 39,735) were mine operator employees. • Contractors comprised 10% of all underground mining employees (n = 4,280) and comprised only 5.8% of all underground FTEs. • The majority of underground employees worked for coal operators (73.0%; n = 32,130).

Feb 1, 2005

Any communication system requires at least three elements in order to function: a transmitting device, a receiving device, and a transmission line or propagation medium. Even the device children use, tin cans connected with string, consists or these three elements. One speaks into one can (transmitter), which vibrates at the same frequencies as the voice. The string (transmission path) picks up the vibrations of the can and carries them along its entire length. The other can (receiver) detects the vibration and reproduces the original sounds to a lesser extent depending on distance, tightness of string, type of string, etc. All communication systems depend on these three elements: transmitter, transmission path, and receiver. Communication systems can be divided into three fundamental categories: wired phone systems, radio systems, and carrier current systems. Sections 2.2, 2.3, and 2.4, respectively, describe these systems and explain the basic principles of how each works. Hybrid systems are those systems that use various combinations of the three basic communication methods. Hybrid systems are described in section 2.5. There are some other methods of signaling (stench warning, bell signaling, etc.) that can be used in underground mines to transmit or convey information. These systems, although they cannot be considered true communication systems since they do not provide voice or even two-way communication, are briefly described in section 2.6. 2.2 Wired Phone Systems Wired phone systems are all those that depend on a wire connection between phones with the wire carrying the voice signals. Figure 2-1 is a diagram of two typical wired phone systems.The top panel shows a simple single pair party line system. In this system each phone is connected to a common pair of wires, and a person speaking into one phone will be heard at all the other phones on the line. The bottom panel shows a multipair private line phone system. In this type of system, each phone is connected by its own individual pair of wires to a central switch or telephone exchange. To establish a call between two phones in this system, the lines between the two phones must be connected (switched together) within the telephone exchange. In early exchanges, the connections were made manually by an operator. These exchanges are called Private Branch Exchanges (PBX's). Today, equipment within the exchange can automatically connect each phone to any other phone in the system. These exchanges are called Private Automatic Branch Exchanges (PABX's). There are many different types of automatic exchanges. Some utilize switches to physically make each connection according to the number dialed. Other, more advanced exchanges are completely solid state and may even be computer controlled. [ ]

Jan 1, 1984

By E. A. Barrett, K. M. Kowalski

The U.S. Bureau of Mines (USBM) conducted experiments to determine if training using a latent- image, three-dimensional (3-D) slide simulation exercise improved miners' ability to recognize roof and rib hazards. The effectiveness of this innovative type of classroom training was investigated by measuring workers' performance on a hazard recognition task. The study was unique in that hazard recognition skills were assessed in the workplace using actual coal mine roof and rib hazards. Results showed that training with a latent-image, 3- D slide simulation exercise significantly improved each subject's performance on the in-mine hazard recognition task. Further, the USBM researchers concluded that transfer of learning from the classroom to the workplace occurred.

Jan 1, 1995

By Ann G. Kim

Methane in coal constitutes a serious hazard in coal mining. Draining the methane in advance of mining can mitigate this hazard, conserve energy, and offer economic benefits. This Bureau of Mines report evaluates the Pittsburgh coalbed in Greene County, Pa., to determine if advance drainage is feasible. The gas content of virgin reserves in Greene County is estimated at 100 to 200 ft3/ton, a total of over 370 billion ft3 of gas in an area approximately 310 mi2. Because of the similarity to natural gas, drained coalbed gas could be recovered and added to pipeline supplies of natural gas. The value of conserved gas would offset the cost of drainage and extend energy resources.

Jan 1, 1975

By T. F. Morse, R. Lundstrom, A. J. Brammer, D. Peterson, M. Cherniack, T. Nilsson, J. D. Meyer, E. Toppila, G. Neely, N. Warren

HAVIC is a collaboration of investigators from North America, Sweden, and Finland having a scientific mandate from NIOSH, to study the exposure response relationship between vibratory tool exposure and adverse health effects. Five cohorts, the Suomossalmi forest workers cohort, Volvo truck cab workers, Connecticut shipyard workers, and matriculating dental hygiene students and experienced dental hygienists have been under study. In the case of shipyard workers, there was survey and tool exposure data from 1988, although detailed subject testing was only available within the timeframe of the study. The truck cab assembly workforce was an inception cohort that had been followed from 1994 along with age-matched controls. The Finnish forest workers had cumulative health data on a cohort (n=52) that had been studied from 1976. For a subset of these subjects, there was detailed tactometry testing in 1990, 1995, and 2003. Accordingly, there was historical as well as new prospective data for the industrial cohorts. The Suomossalmi cohort was reassembled only for our study, which precluded follow-up evaluation and because of retirement is almost certainly the last time this historic group will be studied. The study features are: • Characterization of the exposure response relationship for hand-arm vibration through a study design, incorporating multiple cohorts, some having existing historical data, • Selection of cohorts to include different types of vibration: oscillatory (forest workers) impact (truck cab workers), high frequency (dental hygienists) and mixed (shipyard workers), • Inclusion of two inception cohorts: dental hygiene students and Swedish truck cab workers, • Methods for multi-site and historical integration A description follows. [ ] Methods The study included surveys, physical evaluation, and a selection of battery of “best tests” (cold challenge plethysmography, multi-frequency tactometry, segmental sensory nerve conduction velocity [SNCV]1,2,3) applied across groups to quantify responses to exposure. Exposure monitoring included exposure characterization through daylong data logging at the individual level. Workers at each site were instrumented with a microcomputer-based Vibration Exposure Monitoring (VEM) system, developed at the Biodynamics Laboratory of UCHC and about the size of a police walkie-talkie, to record user-specific tool-operating times, vibrations, and grip forces throughout all, or a representative part, of their workday. More specifically, data logging methods involved the direct monitoring of work cycles, involving tool operation time and measures of tool vibration, namely the root-mean-square (RMS), root-mean-quad (RMQ), and root-mean-oct (RMO), and grip forces, each calculated per minute. For this study, the questionnaire was homogenized with other vibration studies4,5,6. Cross-translation was directed by the multi-lingual investigators, and then reviewed by the study team. To extend comparability with future international studies, questions were also added from the Vibration Network (VINET) draft questionnaire, the product of a European

Jan 6, 2006

The production of harmful pollutants from coal mines and/or from coal and associated strata has been a recognizable fact in the United States for over two hundred and seventy years. In 1698, Gabriel Thomas observed(l) that the colored water flowing from streams in this country was similar to that which flowed from the coal mines in Wales. Hence, water pollutants such as acid were being produced before any known coal mines were operating in this country. The coal mining industry has contributed to the increase of pollution by exposing large amounts of sulfide materials that enable the reaction of water, oxygen and sulfur containing materials to form acid. A map of the United States coal fields can be seen on Figure 1. The anthracite regions of Pennsylvania, although small when compared to the total reserves, have produced some of the country's major water problems. The map indicates the extent of bituminous reserves of the Appalachian and midwest regions. Also evident are the bituminous, subbituminous and lignite coal reserves in the west which have recently come into greater demand. Acid mine pollution is encountered in numerous states, but the major problem is found in the Ohio, Susquehanna, and Potomac River basins.(2) Most coal beds contain some sulfur which may be in the inorganic, sulfate, or sulfide form, and thus have the potential to produce sulfuric acid. However, much of the strata that overlays the coal beds also contains acid neutralizing materials. Therefore, the amount of acid produced depends upon the amount of both acid and alkali materials that dissolve in the water in any given mine. The common sources of sulfurous material in the seam or surrounding rock are generally called sulfur balls or "nigger heads" by the miners. Sulfur balls that have been observed(3) seem to be equally divided between those containing sulphuritic iron capable of producing sulfuric acid upon oxidation and those that are primarily calcium carbonate. It has been observed in many instances that two types of water, acid and alkaline, are being produced in the same mine. A study of the geological strata and a survey of subsidence, faults and sulfur balls will usually give some indication of why this happens. The reaction of pyrite (FeS2) with oxygen and water to form ferrous sulfate (FeSO4) and sulfuric acid (H2SO4) by a series of complex chemical interactions is well documented but not well understood.(4,5) However, it is well known that the reactions to form the acid cannot occur unless all three constituents are present. Since pyrite is inherent in most coal seams and air is needed to sustain the miner, the most logical answer is to eliminate water infiltration into the mine, or to remove it from the mine before acids can form.

Jan 1, 1970

Antitrust Investigation Dropped. - The Department of Justice announced that it was dropping its 5-year investigation of the aluminum industry. The investigation was over whether the aluminum companies were acting as if they were a shared monopoly. Deep Seabed Mining. - The Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) has established an Office of Ocean Minerals and Energy which will be responsible for implementing the Deep Seabed Nard Minerals and Energy Act and the Ocean Thermal Energy Conversion Act. It will establish licensing and regulatory programs.

Jan 1, 1980

By W. W. Graff

This paper describing the mining practice at Mine No. 5 of the Marquette range, Michigan, is one of a series being prepared by the Bureau of Mines on mining practices, methods, tend costs in the various mining districts of the United States. The top-slicing system of mining, has been used ever since the present operating company took control of the property in 1903, the main level and sublevel layout being chanced only as local conditions required and the use of mechanical equipment increased.

Jan 1, 1930

By T. E. Gray

This report describes the preparation characteristics of the significant coalbeds in Nicholas County, W. Va. It is one in a series describing coals suitable for producing metallurgical coke, either as mined or after beneficiation. Almost 5 million tons of coal were produced in Nicholas County, W. Va., in 1960, of which over 2.6 million tons were cleaned in eight preparation plants. It has been estimated that over 6 billion tons remained in the county as of December 31, 1960, in beds 12 inches and more thick.

Jan 1, 1962

By B. W. Gandrud

In 1927 Coghill5 showed that there is considerable liberation of the iron oxide mineral from gangue when the Alabama red iron ores are ground to a size suitable for classification and tabling, but that there is not sufficient to make possible a high extraction and a high grade of concentrate. Coghill states: High extraction and high grade of concentrate cannot be obtained without grinding to a size comparable with flotation or cyanide practice. If grade of concentrate be sacrificed the grinding need not be so severe.

Jan 1, 1934

By W. J. Fene

A comprehensive study of all bituminous coal-mine fatalities occurring in Pennsyl¬ vania during the 5-year period, 1926-1930, was made to try to determine the factors that in¬ fluence accidents which cause these fatalities. During this study some two thousand reports of fatalities were reviewed, and pertinent information as to causes and influencing factors were tabulated therefrom. These tabulations are discussed in detail, and in some instances recommendations are made with a view to reducing the hazards in certain classes of these accidents.

Sep 1, 1931

By J. L. Ellenberger, P. W. Jeran

A deep longwall coal mine was instrumented with a three-dimensional microseismic system in order to help determine the exact strata mechanics associated with the rock failure, redistribution of stress and the associated gob formation from the longwall. Overall, 5,000 well calibrated seismic events were recorded during the mining of the panel. Analysis of these events showed a close correlation between the seismic activity and advance rate, and that the majority of the recorded seismic activity occurs in the immediate area of the advancing longwall face.

By F. D. DeVaney

In the course of the investigation by the U. S. Bureau of Mines and the Missouri School of Mines and Metallurgy at the Mississippi Valley Experiment Station at Rolla, Mo., on the beneficiation of the low-grade manganese ores of the country, some samples from the Cuyuna District, Linn., have been examined. The work was done under the direction of W. H. Coghill, supervising engineer of the Mississippi Valley Experiment Station. Joseph and Kinney in writing about the relative importance of Minnesota deposits of low-grade ore compared to the total reserves say: "***It has been estimated that 26 to 35 million tons of ore contain 5 to 35 per cent of manganese, and the total domestic tonnage is from 75 to 48 million tons. The mean of these values is 30.5 million and 42 million tons, so it is seen that about 75 per cent of the reserves are in Minnesota." The manganese-bearing ores of the Cuyuna district maybe roughly grouped into two classes. The most abundant ore is of the low-silica, low-manganese, and high-phosphorus type called brown are. The other type is the so-called black ore, which is characterized by a higher manganese and silica content and by a lowe phosphorus analysis than the brown ore. As a general rule the brown ore carries less than 10 per cent of manganese while the black ore contains about 15 per cent and sometimes as high as 22 per cent of manganese.

Jan 1, 1930

By John D. Foulkes, David A. Curtis, Robert L. Lagace, John L. Rothery

An investigation is made of the feasibility of developing compact transmit antennas and/or other means to efficiently couple VLF to MF band radio energy between portable wireless communication units in coal mines. The completely wireless communication ranges between two portable radios equipped with practically-sized reference loop antennas in representative coal mine environments are estimated. Antenna technology is assessed with respect to transmit moment, range, intrinsic safety, battery and wearability requirements to deter- mine the most suitable antenna types for use by miners. It is concluded that air-core bandolier loop antennas, and perhaps ferrite-loaded loop antennas, having peak transmit moments of about 2.5 ampere-m5 will be the most effective antenna choices for portable units. This choice, however, will not allow the range goal of 1350 feet to be attained in mines having unfavorable signal attenuation and noise environments. Rectangular air-core loops are compared with grounded horizontal-wire and vertical-wire mode exciters for fixed station applications. The potential for significantly increasing the wireless communication range by inductively coupling to communications and power lines in a mine is evaluated and found to be considerable based on theoretical coupling equations. Lastly, the theoretical performance of a hybrid noise cancelling diversity receiving technique that utilizes both the electric and magnetic field components of the ambient noise to improve the receiver output signal-to-noise ratio under certain adverse conditions is estimated and shown to be favorable when the magnetic and electric field noise components are highly correlated.

Jan 1, 1977

By William L. Crentz

Floyd County, KY., contains sizable deposits of high volatile bituminous coal. Some of the coals have been blended with higher-rank coals and used in the manufacture of high-quality metallurgical coke. The Upper Elkhorn No. 3, Upper Elkhorn No. 2, and Upper Elkhorn No. 1 beds produce the bulk of the present output in the county and contain the main known reserves of coal. Little information is available concerning the quality and extent of the deposits underlying the Upper Elkhorn No. 1 bed, although small operations in the past have worked a bed that is reported to be; the Lower Elkhorn. Undoubtedly, these lower beds occur in Floyd County, but depth Will preclude their development into a major source of fuel as long as large deposits of more-accessible coal are available. More is known of the occurrence of the beds above the Upper Elkhorn No. 3 owing to sporadic mining ventures in the upper measures. Many of the coal samples from beds above the Upper Elkhown No. 3. were collected in mines that had been abandoned. Almost all of the present production of Floyd County coal is taken from the Upper Elkhorn beds, and it is unlikely that their dominant position as coal producers will be challenged in the near future. Table 1 shows the coal production of the county by beds, during 1950.

Jan 1, 1952