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By F. A. Rutledge

"The chromite deposits of Red Mountain, 10,miles southeast of Seldovia, Alaska, are in an intrusive of ultramafic rocks. The earliest reference to the deposits was made by U.S. Grant3/; J.B. Mertic, Jr. 4/ made a brief examination in 1917; and A.C. Gill5/ spent 7 weeks studying the ore bodies and geology of the region in 1918. The Federal Geological Survey had a field party in the region from July until September 1940 and the Red Mountain area was mapped and geological data were assembled by P.W. Guild.6/A preliminary investigation of the Kenai chromite deposits was made in July 1941 by R. S. Sanford,7/district engineer of the Bureau of Mines, accompanied by P. W. Guild, assistant geologist of the Geologi¬cal Survey. This was followed by surface sampling and core drilling, which were completed in September 1942 under the direction of John W. Cole,8 associate engineer of the Bureau of Mines. G. O. Gates, associate geologist, and A, B. Unkelsbay, junior geologist, of the Geological Survey, logged cores and interpreted geologic features revealed by Bureau of Mines drilling and trenching.9/J. C. Roehm, associate engineer of the Territorial Department of Mines; examined the Red Mountain area in august 1941.10/Additional exploration of other deposits in. the Red Mountain area was completed during the summer of 194. Work consisted of surface sampling, core drilling, and mapping. G. O. Gates, associate geologist of the Geological Survey, spent 4 days in August investigating results of the Bureau of Mines program.Throughout the exploratory work conducted by the Bureau of Mines the cooperation of Red Mountain Chromite, Inc., and especially of John Blodgett, Jr., and Collis 2, Druley, president and superintendent, respectively, was greatly appreciated. Use of their camp in the Windy River cirque and shops at Kasitsna Bay facilitated the Bureau of Mines program."

Apr 1, 1946

By James P. Rider

Significant advances in longwall mining technology and equipment have occurred over the last decade. By the late 1990s, longwall mine output accounted for 40 percent of all underground output in the U.S., and today longwall mines account for approximately 50 percent of coal produced underground in the United States. A 53 percent increase in average shift production rates has occurred over the last fifteen years. This increased longwall productivity has meant that far more dust is being produced and controlling respirable coal dust provides an ongoing challenge for coal mine operators. The National Institute for Occupational Safety and Health (NIOSH) has completed a series of benchmark surveys at longwall operations across the country to identify current operating practices and the types of controls being used. Gravimetric and instantaneous dust sampling was completed to quantify dust generation from major sources on the longwall section and to determine the relative effectiveness of the different control technologies in use today. Substantial reductions in dust levels were realized at sampling locations on the face when compared longwall surveys conduct in the 1990?s. This paper summarizes the results from the underground dust surveys and discusses current longwall dust control technology and operating practices.

Jan 1, 2010

By Heather N. Dougherty

In the absence of values for each influencing parameter and a known relationship of input-output space, novel approaches should be implemented as proxy solutions to mathematically complicated problems. Proxy solutions can be in the form of linear or non-linear multiple regression equations. Predicting the performance of gob gas ventholes is one of these mathematically complicated problems as it is difficult to know the exact relationships between various parameters influencing gob gas venthole (GGV) performance from active and sealed (completed) longwall panels. In this paper, a discussion of the NIOSH-developed software suite for methane control and prediction (MCP) based on an artificial neural network (ANN) is presented. The application of the ANN-based software suite to develop algebraic relationships for gob gas venthole performance prediction in sealed and active longwall panels is sought. Output information obtained from the NIOSH-MCP software as a response to various input parameters were used to create an input-output database for total flow and methane percentage from GGVs operating in active mines during completed and sealed panel situations. Due to the multi-variable nature of the software, outputs generated using the software for various inputs were used to develop analytical equations first using linear and then second using non-linear multivariable regression techniques. The advantage of this method is its ability to better understand the significant parameters of the relationships between the inputs and outputs for gob gas venthole production in active and sealed panels and to be able to predict their performances using relatively simple analytical functions.

Jan 1, 2010

By Patrick A. Hamilton

This Bureau of Mines report delineates the coal reserve base of anthracite, bituminous and subbituminous coals, and lignite, by mining method and sulfur content, for coal-bearing States west of the Mississippi River. The parameters used to establish the reserve base definition are the result of a joint agreement by the Federal Bureau of Mines and the U.S. Geological Survey. The reserve base of low-sulfur coal, =10 percent sulfur, is 167,324.5 million tons; medium-sulfur coal, 1.1-3.0 percent sulfur, is 37,531.5 million tons; and high-sulfur coal, >3.0 percent sulfur, is 11,244.1 million tons. The reserve base of coal with an unknown sulfur level is 18,323.0 million tons. The percentages of deep and strippable coal are 56 percent and 44 percent, respectively. The basis for reserve base estimates and analytical data for this report was the Fuels Availability System, a Bureau of Mines data bank containing numerous data tin fossil fuels. Information contained in the system was obtained from publications of the Bureau of Mines, U.S. Geological Survey, State agencies, private publications, and company data.

Jan 1, 1975

The importance of controlling respirable dust and methane gas levels in underground coal mining cannot be underestimated. While respirable dust can significantly affect the occupational health of underground coal miners, methane gas accumulations pose significant safety concerns for these same workers. Water sprays and machine mounted dust scrubbers offer effective control of respirable dust exposures and methane gas accumulations. Water must not only be applied carefully to avoid dust rollback to the machine operator but must create sufficient turbulence to remove dead zones that could contain high concentrations of methane gas. While the flooded-bed dust scrubber has been generally responsible for decreased worker exposures to respirable dusts, this device has proved effective in controlling methane levels at the face. This paper reviews practical applications of water sprays and dust scrubbers to control respirable dust and methane gas on continuous miner faces.

The coal-bearing regions of Colorado cover approximately 29,600 square miles, which is 28.4 percent of the state's total area. The most important coal-bearing regions are located in the north western and west-central parts of Colorado. Coal resources vary from lignite to anthracite. More than 70 percent are bituminous; 23 percent subbituminous; 5 percent lignite; and less than 1 percent anthracite. The state's coal reserves total about 17.2 billion tons, 3.5 percent of national reserves. Approximately 8.8 million acres of coal rights in the state are owned by the Federal Government; on about 72percent of this land, the Federal Government controls both the coal and the surface rights. It is estimated that approximately 4.2 billion tons of coal reserves are under federal ownership in Colorado. Permitted acreage of mines in Colorado ranges from 40 to 13,114 acres. Differences in elevation create many climatic zones in Colorado. Local annual precipitation can average less than eight inches in some areas in extreme western Colorado to more than 30 inches in certain mountainous areas. Generally, precipitation rates are low at most mine sites, making revegetation difficult. Colorado gained primacy when its regulatory program was conditionally approved December 15,1980. The Abandoned Mine Land Program was approved June 11, 1982.

Jan 1, 1992

By Sean Gallagher, William S. Marras, Alan S. Litsky, Deborah Burr

This paper describes a comparison of the fatigue failure responses of older versus younger lumbar spine cadaver motion segment specimens. These specimens were repeatedly subjected to loads simulating those experienced by the spine in lifting a 9 kg load in different torso flexion postures (0, 22.5, and 45 degrees of flexion). An older sample of 36 motion segments (average age 81 years + 8 SD) is compared with a younger sample of 18 motion segments (average age: 47 years + 9 SD) with respect to the number of cycles to failure and results of survival analyses evaluating the effects of flexion and bone mineral content with and without the younger data set. Compared to the older sample of spines, the younger sample exhibited many more cycles to fatigue failure in all the torso flexion conditions (10020 versus 8267 average cycles to failure in 0 degrees flexion, 7124 versus 3262 in 22.5 degrees flexion, and 3229 versus 263 cycles to failure in 45 degrees flexion). The increased cycles to failure in young specimens is likely due to the increased bone mineral content (BMC) in younger motion segments (30.7 g + 11.1 g per motion segment versus 27.8 + 9.4 g). Cox regression analyses modeling both flexion effects and BMC indicate that betas are similar when just older spines are modeled and when younger specimens are included in the analysis. Betas for survival analysis models with and without younger specimens generally show little change for flexion (2.716 versus 2.756 for 22.5 degrees [0 degrees referent], 3.926 versus 3.380 for 45 degrees [0 degrees referent]). Bone mineral content shows a similar protective effect in both models (Betas: -0.127 versus -0.087). Overall, comparison of the models indicate that risk ratios are similar for 22.5 degrees flexion, slightly increased for 45 degrees flexion and slightly more protective influence predicted for BMC in the combined sample versus the older sample alone.

By Donald W. Mitchell, John Nagy

Observations made on coking of coal, deposition of soot, dust transport, flame, violence, and related phenomena following experimental coal-dust explosions are summarized. Data are given on gas explosion pressure, flame length, flame velocity, and variation of these parameters with concentration. Conclusions from these observations are useful in preventing similar occurrences in operating mines and serve as a guide in improving safety.

Dec 1, 1963

The Department of Interior, U.S. Bureau of Mines performs the task of estimating the quantity of coal reserves existing in each state on a county by county basis. As a part of Information Circular 8655, the Bureau of Mines established the criteria for the uniform estimations of coal reserves and listed the most recent estimates of coal reserves by county and by seam. At the same time however, the Bureau recognized that these figures represented the upper bound with regard to the estimated actually usable or obtainable reserves. Recovery of these reserves are subject to the mining methods used and to the resolution of such problems as the use of poor quality coal and competition provided by conflicting land use. These problems, in practice restrict the recovery of the estimated quantities of coal reserves listed in IC 8655. Another impact, the subject of this manual, is the impact resulting from previous mining activities. In particular, many of the reserve seams included in the reserve estimates overlie or underlie mined-out coal beds. Portions of these reserve seams may therefore be unmineable or at best may have a reduced quantity of extractable coal. In order to improve the accuracy of the coal reserve base estimates, the Bureau of Mines funded an effort1 to develop a systematic methodology for estimating the coal loss associated with the impact of previous mining activity. The coal loss calculation model (CLCM) described in this manual is a result of that effort and addresses the percentage of coal loss in reserve seams due to previous overmining or undermining.

Jan 1, 1976

By P. -E. Boileau, P. Marcotte, Y. Aldien, S. Rakheja

A number of biodynamic models of the hand-arm system have evolved on the basis of measured driving-point mechanical impedance (DPMI) responses to facilitate analyses of the coupled hand-tool system [1]. The parameter identifications in such models are based upon minimization of an error function of the model and the target impedance data, which may not yield a unique solution. Consequently, a number of model structures and parameter sets could be realized that would equally satisfy the target curve. Moreover, the vast majority of the reported models exhibit acute deficiencies due to excessive static deflections of model masses, presence of a low frequency mode and very light masses in the order of 1.2- 4.8 grams. The models also do not characterize the dependency of the biodynamic responses on many factors, namely the hand forces, hand-arm posture and vibration intensity. This study aims at development of a hand-arm biodynamic model with considerations of the hand forces, and both the DPMI and power absorption measures, to enhance the uniqueness of the model. Methods Two different model structures are chosen for identifying the model parameters on the basis of measured DPMI and absorbed power characteristics of the hand-arm system under zh-axis vibration over a range of hand-grip and push forces. Owing to the strong influence of the hand-handle coupling forces, the models were initially derived for fixed hand forces, namely 30 N grip and 50 N push forces, as suggested in the ISO 10068 standard [2]. The equations of motion for the model are formulated and solved to compute both the DPMI and absorbed power responses. A constrained minimization function comprising weighted errors of both the DPMI and absorbed power is formulated and solved to identify the parameters. Alternate functions corresponding to different combinations of hand forces are then applied to identify hand-force dependent model parameters. Variations in the model parameters are investigated as functions of the grip, push and coupling forces through linear regression analysis. Regression-based models are formulated for deriving the hand-handle forces dependent model parameters. The validity of the model is also examined under selected combinations of hand forces. [ ]

Jan 6, 2006

By V. Castranova

"A pneumoconiosis is best defined as the accumulation of dust in the lungs and the tissue's reaction to iu presence. Thus, silicosis is the name given to the fibrotic disease of the lungs caused by inhalation of dust containing silicon dioxide, primarily in the free crystalline form. Coal workers' pneumoconiosis (CWP), which was originally thought to be a variant of silicosis, results from inhalation of coal mine dust that usually contains relatively small amounts of free crystalline silica.HISTORYSilicosis is the older and more well known of these mineral pneumoconiosis. In contrast, CWP was not recognized as different from silicosis until the pivotal work of Collis and Gilchrist. 26 They noted that coal trimmers, i.e., special stevedores who leveled coal in the holds of ships at the Cardiff and Swansea docks in Wales, developed identical nodules on the chest radiograph to those of underground miners. The difference was that these men had never worked underground and that the coal was washed before it was loaded into ships; thus, it was unlikely that these men were exposed to silica. Gough54 examined the lungs of coal trimmers who died and found that the histologic appearance of the pulmonary lesions was distinctly different from the whorled nodules seen in silicosis. Gough,"" and subsequently Heppleston,"" then showed that the lung lesions in coal trimmers were similar to those in underground coal miners and different from those of classical silicosis. Nagelschmidt 78 analyzed the mineral content of miners' lungs that became available at autopsy. These studies caused him to propose a scheme in which the relative proportions of silica, other minerals, and/or coal deposited in the lungs determined the type of pulmonary response which develops, i.e., classical silicosis, mixed-dust disease, or CWP."

Nov 1, 1995

By Henry P. Chandler

COMBINED sales of abrasive materials in the United States during 1956 increased at about the same rate as the value of the Gross National Product in terms of 1954 dollars,3 which was nearly 3 percent. However, some segments of the industry did not follow the general pattern. Sales of abrasive grinding wheels increased 9 percent in value. Sales of surface-coated abrasives declined 5 percent in quantity hut increased 1 percent in value, Production of crude silicon carbide in the United States and Canada advanced both in tonnage and value, but that of abrasive-grade [ ]

Jan 1, 1958

By Michael J. Jorgensen, Anoop Polsani, Khurram S. Khan

Riveting operations in aircraft manufacturing involves the use of power tools for manually drilling holes for the rivets, power drills for the setting of the holes for the rivets, as well as rivet guns to drive and set the rivets. To close the rivet, the rivet is driven against a metallic bar commonly called a “bucking bar”. The bucking bars are typically held firmly to increase the quality of the riveting, as well as keep the bucking bar from “dancing” against the metal piece being riveted. Thus, employees in aircraft manufacturing involved in riveting are exposed to hand-arm vibration from several sources, and epidemiological evidence suggests that vibration-related musculoskeletal disorders are associated with long term exposure to riveting tasks in the aircraft manufacturing of aircraft.1,2 Recently, tungsten technology has been introduced into aircraft manufacturing for bucking bars, which are heavier than traditional steel bucking bars of the same size. Rivet guns with tungsten pistons instead of steel pistons have also recently been introduced with the objective of reducing vibration exposure to the riveter. The objective of this study was to assess vibration characteristics of steel and tungsten bucking bars and rivet guns to identify the combination that simultaneously reduced the combined exposure to both the “riveter” and “bucker”. Methods Vibration (10g tri-axial accelerometer, Biometrics S2-10G-MF Series 2) was measured from eight experienced employees using seven different rivet guns on size 6 rivets, with the same person bucking for all subjects. Vibration was also measured on two different bucking bars for these same eight subjects, with the same person driving the rivets using the various rivet guns. The rivet guns consisted of three E4 steel piston guns with different RPMs (Guns A-E4, B-E4, C-E4), an E4 vibration dampened rivet gun (Gun D-E4D), an E3 steel piston rivet gun (Gun E-E3) and an E3 and E4 tungsten piston rivet guns (Guns F-E3T and G-E4T). The bucking bars were made of 90% tungsten (1694g) and cold-rolled steel (843g), and were the same shape and size. A two-way repeated measures analysis of variance was performed on the vibration (mean frequency weighted resultant acceleration) on both the rivet gun side and the bucking bar side, and mean rankings were used to assess the vibration simultaneously for the rivet gun and bucking bars to investigate which combinations provided the lowest vibration exposure. Results Frequency weighted resultant acceleration was significantly lower on the E3 tungsten (F-E3T) rivet gun than the E4 steel piston (B-E4) and the E4 tungsten piston (G-E4T) rivet guns (Figure 1). When measuring vibration on the bucking bar, the E4 (A-E4) steel piston rivet gun resulted in lower vibration on the bucking bars than the E4 tungsten piston (G-E4T) and E4 vibration dampened (D-E4D) rivet guns (Figure 2). Additionally, use of tungsten bucking bars resulted in a 35% decrease in resultant frequency weighted acceleration than when using steel bucking bars.

Jan 6, 2006

By Ren G. Dong, Thomas W. McDowell, John Z. Wu, Chris Warren, Dan E. Welcome, Chun L. Dong

Hand forces are important factors for risk assessment of hand-arm vibration syndrome (HAVS).1 Grip force is one of the most important force components in the operation of powered hand tools. A considerable number of studies on grip force have been reported. It is well known that the grip force applied on a cylindrical handle is not uniformly distributed on each axis across the center of the handle cross-section.2 Therefore, maximum and minimum orientations of grip force exist around the handle. Such orientations have not been clearly identified. In a recently proposed international standard (ISO/CD 15230, 2005),3 it is stated that “the direction of the main gripping force is generally parallel to the z-axis defined in ISO 8727.” 4 This assertion is questionable, and further examinations are required. The objective of this study was to establish a fundamental theory on the distribution of the grip force around cylindrical handles. Methods As shown in Fig. 1, the grip force is defined as a vector composed of normal and shear components (FN & FT) in this study. Fig. 2 shows the hand coordinate system defined in this study, together with the ISO systems.1,4 Based on this novel grip force definition, we derived four fundamental properties and a theorem. More significantly, we formulated a novel hypothesis: similar to Mohr’s circle of stress, the normal and shear components can be represented approximately using an ellipse on the plane of the two force coordinates, as shown in Fig. 3. The maximum and minimum grip normal forces are termed as the first principal grip force (F1) and the second principal grip normal force (F2), respectively. Their corresponding orientations are termed as the first principal grip angle (a1) and the second principal grip angle (a2). A series of experiments were conducted to test this hypothesis. Twelve

Jan 6, 2006

By John C. Machisak

INJURY DATA and experience at, coal mines in the United States for 1953 and 1954 are presented in this publication with a minimum of interpretation and comment because of the numerous tables required to afford detailed comparisons between the 2 years. Corresponding tables for 1953 and 1954 follow in consecutive order under the following general sections: (A) General injury experience: Tables 1 to 11: Contain current data on number of fatal and nonfatal injuries, frequency and severity rates, and average severity and time-loss rates. (B) Selected injury data: Tables 12 to 85: Contain current data on causes of injuries, distribution of injuries by part of body injured, days of disability, extent of hand and machine loading, experience by employment and production groups, and various other operating factors and physical conditions related to the occurrence of injuries at the Nation's coal mines.

Jan 1, 1958

By G. L. Oldright, Virgil Miller

"This paper is the eighth; of a series on smelting in the lead blast furnace, and the third' of a group on the modifications brought about by the introduction of rich charges.ACKN0WLEDGMENTSThe data that appear in these articles were obtained through the courtesy of the operators of the Bunker Hill smelter at Kellogg, Idaho. The authors take this opportunity to express their appreciation to Stanley A. Easton, the vice-president and general manager, Frank M. Smith, smelter director, and to A. F. Beasley, the smelter superintendent, and his staff.INTR0DUCTI0NIt has been noted that the gases issuing from the top6 of the charges in the International Smelting Co.'s furnaces at Tooele, Utah, were very similar in composition to the gases from the top of the iron blast furnace, as they contained about 26 per cent of CO and 12 per cent of C02, the rest of the constituents being mainly nitrogen with a very little hydrogen and oxygen. It has been seen that where the column of coke was sufficiently high, the production of C0 gas to carry out the reduction of lead ores was accomplished in about the same manner as in a gas producer. In some cases, there was a little oxygen in the ""top gas"" -- usually not over a few tenths of a per cent, but at times amounting to several per cent. The presence of this gas was attributed to irregularities in operation that permitted air to come up through the tuybres to the surface without meeting any coke that was incandescent. Only a hundredth of a per cent or so of sulphurous oxides was present in the gases issuing from the top of the furnace."

Apr 1, 1931

By C. Ozgen Karacan, William P. Diamond

In This Chapter [Measuring the gas content of coal Predicting gas emissions based on geologic and coal reservoir property data Determining the gas storage capacity of coalbeds and other gas-bearing strata Methane drainage borehole monitoring to forecast the remaining gas-in-place and the influence on mine emissions Forecasting gas emissions during mining as a function of mining parameters and Gas emission prediction based on numerical simulation] This chapter provides guidelines for determining the gas content of coalbeds, estimating the gas-in-place, and predicting gas flow and emissions before and during coal mining operations. The techniques are discussed briefly in the following sections. However, detailed information on the techniques is provided in the cited references. INTRODUCTION Coalbed methane, if not properly controlled in the underground mine environment, is a safety concern due to the potential risk for an explosion. This is a particular problem during longwall mining, where the high rate and volume of coal extraction can result in the release of large amounts of methane from the mined coalbed and other adjacent gas-bearing strata. The variability and potential hazards of these sometimes unexpectedly high gas flows provide the impetus to develop methods to predict methane emissions into the underground workplace. A forecast of the volume of gas that might be released during coal mining is helpful for designing ventilation systems and for implementing optimum methane drainage strategies to help mitigate expected gas emission problems. A complete assessment of the need for methane drainage prior to mine development generally requires both an empirical and a theoretical approach. If there are active mines in the general area with similar geologic conditions and coal characteristics, a review of gas problems in those mines provides an initial insight into the level of gas emissions to be expected at a new location. In addition, relatively simple methods exist to determine the in situ gas content (volume of gas per unit weight of coal) of the coalbeds in a particular mining area, as well as the gas-in-place (volume of gas in the coalbed(s) within a defined geographic area).

Jan 6, 2006

By Robert L. Lagace, Michael A. Grossman, Alfred G. Emslie

This supplement to the final report is a collection of interim and monthly reports and working memoranda prepared during the course of this program to document the progress, methods and results of the work. The supplement is divided into the self-contained sections briefly described below. I. SELECTED MONTHLY TECHNICAL LETTER REPORTS - This section is a collection of selected monthly technical letter reports that briefly summarizes the chronological development of the analyses and results, including the different concepts, theoretical approaches, and methods of data reduction and analysis explored, and the discoveries, insights and findings made along the way. More detailed treatments of the key developments and results are presented in the interim reports and working memoranda reproduced in subsequent sections of this supplementary report, and in the separately published final report. II. BACKGROUND THEORY FOR MEASUREMENT PROGRAM ON MEDIUM AND HIGH FREQUENCY RADIO TRANSMISSION IN COAL SEAMS - Working Memorandum - This working memorandum gives the initial background theory needed to guide the planned measurements and data analyses of this program to describe the propagation of radio waves-in coal seams for the frequency range of 50 to 5000 kHz. III. MODELLING AND DATA ANALYSIS OF IN-MINE ELECTROMAGNETIC WAVE PROPAGATION - Interim Report - This interim report presents detailed treatments of the data analysis and modelling techniques used, and the associated results obtained from conductor-free area propagation data measured by T. Cory in the first set of six coal mines. The mines were located in three highcoal seams; the Pittsburgh seam in northern West Virginia, the Pocahontas No. 3 seam in Virginia, and the Herrin No. 6 seam in Illinois. IV. ANALYSIS OF MF PROPAGATION DATA FROM MARGARET NO. 11, NANTY GLO, EHRENFELD, AND ADRIAN COAL MINES - Interim Report - This interim report presents detailed treatments of several improved data analysis and Modelling methods applied to, and results obtained from, conductor-free area propagation data measured by T. Cory in the second set of four coal mines. These mines were located in three low-coal seams; the Upper Freeport seam in Pennsylvania and West Virginia and the Lower Freeport and Lower Kittaning seams in Pennsylvania. In addition, this report contains a reprint of two papers presented at a Bureau of Mines sponsored EM Guided Waves in Mine Environments Workshop held in Boulder Colorado. One paper describes the three-layer theoretical model and its application to the conductor-free data from the first six mines, while the second paper describes the theory developed for the coupling of loop antennas to a cable in a mine tunnel in a coal seam, and the model's application to data in the vicinity of cables taken at the Margaret No. 11 mine. V. A METHOD FOR NONINTRUSIVE, IN-SITU MEASUREMENT OF COAL AND ROCK CONDUCTIVITIES IN A COAL MINE TUNNEL - Working Memorandum - This working memorandum briefly describes a possible direct method, and its potential advantages and shortcomings, for performing in-situ measurements of coal and rock conductivities. VI. MODELLING AND DATA ANALYSIS OF IN-MINE ELECTROMAGNETIC WAVE PROPAGATION FROM 50 to 5000 kHz - Interim Report - This interim report presents a summary comparison of theoretical and experimental results for conductor- free areas in eleven coal mines located in seven coal seams. It also summarizes the findings and their implications for intrinsically-safe, portable radio communications between roving miners.

Jan 2, 1980

Research personnel from the Bureau of Mines, representatives of the Mining Enforcement and Safety Administration (MESA), and members of the mining industry met with other Government and Industry representatives at three seminars held in Pittsburgh, Pa., November 4, 1975; St. Louis, Mo., November 6, 1975; and Denver, Colo., November L1, 1975, to discuss the results of Bureau-sponsored research on coal mine illumination. The program, aimed at developing suitable illumination systems fur the working; places of underground coal mines, covered hardware development and field evaluation and the status of proposed MESA standards and proposed MESA enforcement procedures. These proceedings contain the opening remarks to the seminars and eight technical presentations an various aspects of coal mine illumination.

Jan 1, 1976

By Liming Yuan

Barometric pressure changes affect air density, leading to change in the mass of the gas in the gob. When the barometric pressure decreases, the volume of gas in the gob expands, while the volume of gas contracts when the barometric pressure increases, causing the gob to breathe out and in. Although the concept of gob ?breathing? is simple, its effect on spontaneous heating of coal in the gob area is not clear. In this study, computational fluid dynamics (CFD) simulations were conducted to model the spontaneous heating of coal in longwall gob area under measured barometric pressure changes. A single longwall panel using a bleederless ventilation system was simulated. If there is no barometric pressure change, the intake airflow rate is equal to the return airflow rate. When the barometric pressure changes, these two airflow rates are no longer equal, and the difference between the two airflow rates represents the airflow rate the gob breathes in and out. The effect of inflow and outflow of gas on the potential spontaneous heating in the gob was investigated using the CFD model developed in our previous study. The effect of barometric pressure changes on the spontaneous heating was found to be dependent on the gob permeability and the coal oxidation rate. The effect of barometric pressure changes on oxygen concentrations in the gob was also examined.

Jan 1, 2010