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By Geo S. Rice

"Three men lost their lives in the Black Diamond Coal Mine near Seattle, Wash., recently while wearing oxygen breathing apparatus. The press dispatches stated that these men lost their lives while practicing with the apparatus. Later reports stated that the men died while attempting to make a trip 1200 feet down a 25 degree slope which was filled with black damp, in order to measure the amount of water that had accumulated at the bottom of the mine, and the trip was attempted with oxygen in the tanks of the apparatus with dials indicating only 45 minutes supply. The oxygen in the tank was used up and the men therefore lost their lives from a deficiency of air to breathe.In spite of all the education and training done by the Government to prevent accidents, men are prone occasionally to take unnecessary chances. Every piece of apparatus, no matter how perfect, has its limitations. The Government, through the agency of the Bureau of Mines, has trained many thousands of miners in the use of mine rescue apparatus. The training has been given to all miners who requested it, and the Bureau has gone to the extreme of urging miners to join the rescue and first-aid classes. In spite of all the efforts of the Government, men occasionally attempt the impossible."

Jul 1, 1920

By Robert F. Chaiken, Thomas H. Dubaniewicz, Gregory M. Green, Kenneth L. Cashdollar

Optical technologies have progressed rapidly in the past 15 years. One application of laser technology in underground coal mines currently under evaluation is the remote measurement of explosive methane gas. Federal regulations require that atmospheric monitoring systems used in gassy underground mines where permissible equipment is required shall be intrinsically safe. Mine Safety and Health Administration criteria for the evaluation and testing of intrinsically safe apparatus and associated apparatus contain no specific guidance for optoelectronic components such as diode lasers. The National Institute for Occupational Safety and Health is conducting a study to help provide a scientific basis for developing appropriate safety guidelines for optical equipment in under- ground coal mines. Results of experiments involving ignition of methane-air mixtures by collections of small heated particles of Pittsburgh seam coal and black iron oxide are reported. The inert but more strongly absorbing iron oxide targets consistently ignited methane-air mixtures at lower powers than the coal targets. Minimum observed igniting powers for laser energy delivered by 200, 400 and 800 pm core fiber optic cables and directed onto iron oxide targets in methane-air atmospheres were 0.6, 1.1, and 2.2 W, respectively. Comparisons with the results of other researchers are made. A thermal layer theoretical approach to describing the process is included as an appendix.

By Peter Kovalchikb, Gregory Colec, Syd Peng, R. J. Matetic, Jeffrey Petersond

Mine Safety and Health Administration (MSHA) data indicates that the roof bolting machine is third among all equipment and second among equipment in underground coal mining whose operators exceed the MSHA-PEL (Mine Safety and Health Administration-Permissible Exposure Limit). In response to this, the National Institute for Occupational Safety and Health (NIOSH) has conducted a study to reduce overexposures of noise to operators of roof bolting machines. An important segment of the research is to determine, characterize and measure sound power levels radiated by a roof bolting machine during different drilling configurations. The determined sound power levels generated during the drilling cycle are of major interest because the levels represent the overall sound power generated by the machine. These sound power levels, determined from laboratory tests, can be used to accurately assess the effectiveness of proposed controls for reducing noise exposure to roof bolting machine operators. By using the sound power level results obtained from the laboratory and a commercially available acoustical modeling package, a method for predicting sound pressure levels to roof bolting machine operators for differing drilling types and parameters could be determined. This paper provides a method for predicting sound pressure levels at the operator’s position of a roof bolting machine in an underground coal mine using sound power levels determined in the laboratory. To determine validity, underground coal mine data was also collected to compare predicted and measured sound pressure levels. The results of the predicted sound pressure level data were the same as the underground measured results. This research will provide the mining industry with a valid method for predicting a roof bolting machine operator’s noise dosage underground given any type of drilling configuration or drilling method utilized from laboratory testing.

By M. A. Trevits, S. W. Lambert

In this Bureau of Mines investigation, production was monitored for 1 year at over 30 coalbed gas-drainage boreholes located in Alabama, Pennsylvania, and West Virginia. Results indicate that the quality of data gathered from such wells can be improved greatly if potential problems are anticipated and prevented in the early stages of well production. Major water-monitoring problems include solids buildup, freezing, the presence of gas in surface waterlines, and improper pumping interval settings. Such problems may be avoided by incorporating in the original well design waterline filters, sand screens, separator tanks, and systems to automatically control pumping intervals. Problems related to measurement of coalbed gas flow include large quantities of water vapor contained in the gas, especially during winter months; freezing and subsequent obstruction of flow; sudden, uncontrolled release of gas pressure; and solids buildup in metering equipment. The installation of commercially available items, such as filters, separators, and insulation, and the thoughtful application of a basic knowledge of coalbed gas reservoir characteristics will prevent most production-monitoring problems.

Jan 1, 1978

Design and test a high-production coal mining machine that generates less respirable dust. Background Current coal cutting systems generate excessive amounts of airborne respirable dust and fines during the mining process. Dust control technologies, including dust dilution by ventilation and suppression by water sprays, are not always able to reduce dust levels sufficiently. The U.S. Bureau of Mines (USBM) has designed a cutting system that reduces respirable dust generated by the cutting action of the drum. This cutting system, based on geometric principles developed in the 1500's, makes use of a constant depth, linear cut to remove coal at deeper cut depths and at lower rotary speeds than a conventional rotary drum. A comparison of the linear and rotary cut paths is shown in figure 1. Approach A full-scale prototype of the linear cutting concept was valuated under laboratory conditions to determine its performance relative to standard rotary drums. Results of these evaluations show production of fewer fines, or more uniform product size, a significant reduction in the amount of airborne dust, and reduced torque and power requirements (figure 2). On the basis of these results, a contract effort was undertaken by McCracken and Associates of Bristol, TN, to design a linear cutting head for underground testing.

Jan 1, 1995

By S. P. Kinney, A. C. Fieldner, S. H. Katz

"1 Introduction The regrettable death of James S. Cunningham, Foreman Miner, attached to Bureau of Mines Rescue Car No. 2, while wearing a half-hour type oxygen breathing apparatus in a gasoline storage tank at Trinidad, Colorado, raised the question as to the possibility of gasoline vapors permeating the rubberized fabric of the breathing bags of such apparatus.It is known that most gases and especially certain organic vapors permeate rubber, by solution or a similar process. The rubber becomes saturated with the gas and if a concentration of gas is maintained on one side of the rubber sheet it slowly gives off gas from the other side. It of course takes some time for the gas to diffuse through the rubber and the length of time before it reaches the other side is proportional to the thickness of the rubber. The amount of gas that passes through per unit of area in unit time increases with the concentration of gas and also varies with the structure and composition of the rubber.It has been suggested that the gasoline vapor could not have penetrated into the interior of an oxygen breathing bag because the pressure is greater on the inside, but this is not true as the process of permeation by solution in the rubber is affected only by the difference in the partial pressures of gasoline vapor on the inside and outside of the bag. The positive oxygen pressure on the inside can only prevent the entrance of gasoline vapor through measurable holes, and has no effect on permeation by diffusion through the rubber."

Dec 1, 1919

Design a new acoustic monitoring system to more accurately forecast impending rock bursts, and to assist in understanding the rock burst phenomenon. Background Rock bursts arc the major cause of injuries and deaths in deep underground mines in the Silver District near Wallace, ID. Bureau investigations of the rock burst phenomenon resulted in significant improvements in computerized acoustic technology, and achieved limited success in forecasting several large events. Research demonstrated that the location of rock noise, and the rate at which these events occur, are indicators of areas that could fail violently. In minewide monitoring, the typical array of acoustic sensors (geophones) is arranged to cover an entire mine with 16 to 32 separate instruments. The mines intended to be covered may be 7,000 feet in depth and up to several miles in extent. While such an arrangement is capable of detecting and locating large seismic events (rock slippage along natural fractures or faults), the geophones are too far apart to accurately locate mining-induced events at the active workplaces. The Bureau devised a strategy to concentrate the geophones into typical slopes (mining areas about 200 by 500 feet) to record the rock noise in areas where the miners work. By using such a dense geophone array at a mine, the Bureau provided event location and rate information to mine operators who removed workers and ceased production from active mine areas that subsequently suffered rock bursts.

Jan 1, 1989

Enhance coal mine worker safety and productivity by developing a means to control and predict coal mine mountain bumps. Approach The Bureau of Mines has been engaged in extensive research to understand coal mine mountain bumps and their effect on underground coal mining in the United States. Information was collected on the geologic conditions, mining techniques, and engineering parameters at five mountain-bump-prone mines. Although research has not yet evolved to the point where mountain bumps can be effectively predicted or controlled, such studies are invaluable for providing clues that can lead to the development of mountain bump mitigation technology. Case Study Results and Recommendations Mountain bumps in coal mines are explosions of the coalbed that violently release the strain energy stored within it into openings created by mining. Such an event is not only dangerous to mine workers, but can cause substantial amounts of damage to mine equipment, resulting in productivity loss and downtime. In a coal mine, the occurrence may cause coal to be expelled violently from the coal face or coal pillars or cause the mine floor to heave suddenly. Coal bumps are usually accompanied by a very loud noise and tremors or vibrations. Such ground failure:; usually occur in the vicinity of an active gob line in an active retreating room-and-pillar panel, or at or near the face in an advancing or retreating longwall mining panel.

Jan 1, 1989

To develop a reliable, remotely-controlled, mobile roof support to eliminate the need to set posts, cribs, or props while extracting coal pillars. Approach The primary danger during pillar extraction is premature caving of the mine roof. The roof must cave predictably and dependably to ensure the safety of miners. Support during retreat mining is usually obtained by setting posts, cribs, props, roof bolts, or a combination of these devices. These are set manually by miners in the working area. To help minimize the danger to mine workers and to equipment posed by premature falls, the Bureau of Mines developed the mobile roof support (MRS) system to secure the roof during pillar extraction. How It Works The Mobile Roof Support (MRS) is eight-feet-wide, ten-feet-long and five-feet-high, with twelve inches of ground clearance. It is ruggedly built and exerts less than 20 psi ground pressure. The MRS is powered by a 40-hp, 460-v AC permissible motor. The reversible, variable tram speed is 80 ft/min on a 20-percent grade. It is tire-mounted, has a trailing cable, and is remotely controlled either by a radio or a tether communication cable. The machine carries four 50-ton jacks which serve as props for working heights from seven to fifteen feet. Two jacks are chassis-mounted and two are on swing arms. Each jack has a cap which distributes the roof load to three paints. The swing jacks form a breaker row to stop falling roof and prevent caving Into the work area. One jack has a visual load indicator and a second is wired to the machine lighting system. Blinking lights indicate when the preset loading is being exceeded. In the case of excessive loads, an ability to remotely jettison either or both swing jacks has been incorporated into the system to permit removal of the MRS while the roof is still supported.

Jan 1, 1985

To enhance safety and efficiency when moving large mining equipment under energized trolley lines, and to assist in compliance with Section 75.1003.2, 30 CFR. Approach A system was designed, using established technology, that permits a remotely located circuit breaker to be controlled from the cab of a mine locomotive moving large mining equipment under energized trolley lines. This control consists of setting the desired trip current, automatic or manual tripping, resetting, and voice communications between the locomotive and a remote Circuit breaker location. How It Works According to 75.1003.2, 30 CFR, whenever a piece of off-track equipment (such as a longwall chock or a continuous miner) is moved by rail under energized trolley or feeder lines, power for the locomotive that is moving the equipment must come from only one' circuit breaker. This circuit breaker must be adjusted to permit no more than one-half its rated short-circuit current to flow. The intent is to lessen the danger if an accident should occur, and if the equipment contacts the trolley line. Even so, the danger is great. This half setting can still represent many hundreds or even thousands of amperes, enough to endanger personnel, the equipment, or the mine. The Remote Control System reduces this danger substantially by giving the personnel associated with the move total control over the associated circuit breaker. The system as designed, is intended to be used with portable circuit breakers that are pulled on a small flat car by a mine jeep, and either precede or follow the equipment, depending on the direction of the power. This portable circuit breaker is equipped with a commercially available solid state overcurrent relay and associated shunt. This circuit breaker is connected via heavy duty clamps around an open trolley line tie breaker such that the current through the shunt is also the current in the trolley line. A receiver, interfaced with the overcurrent relay and shunt, completes the remote system.

Jan 1, 1981

By R. V. Ramani, C. B. Manula, A. Owili-Eger

All the input data required to operate the ventilation simulator except the title, are entered with I10 or F1O.O formats. The title is entered with (18A4) format. The floating points are designated by (FP) and the integers by (INT)

Jan 1, 1975

Native asphalt was produced in 1977 by six companies in four States. Leading States were Texas and Utah. Output declined 39% to 1,237,000 tons valued at $18,874,000. Bituminous limestone was produced by Whites Uvalde Mines and by Uvalde Rock Asphalt Co. in Uvalde County, Tex.; by Southern Stone Co. in Colbert. Ala.; and by Barton County Rock Asphalt Co. in Barton County, Mo. Gilsonite was produced by American Gilsanite Co. in Uinta County. Utah, and by Ziegler Chemical and Mineral Corp. in Weber County. Utah. The asphalt was used for streets and roads, and for other purposes.

Jan 1, 1980

By R. S. Conti, C. D. Litton

This U.S. Bureau of Mines (USBM) report discusses the results of research conducted in the USBM experimental mine at its Lake Lynn Laboratory to determine the alarm times of smoke and carbon monoxide(CO) sensors, and a point type heat sensor (PTHS) to slowly developing coal-conveyor belt fires. The tests were conducted at air velocities of 0.44 and 0.97 m/s. The data clearly indicate that smoke sensors provide earlier warning of fire than 10 ppm CO sensors, and that 10 ppm CO sensors provide earlier warning than PTHS. A success rate of 1.0 (indicating detection of every test fire) was obtained for both smoke and CO sensors. For the PTHS, the success rate was 0.57 at the lower air velocity, decreasing to 0 at the higher air velocity. Data are also presented showing the sequence of fire events and detection events at the two air velocities as a function of time. Results show that early detection and warning of underground mine fires will improve the probability of miners’ escape.

Jan 1, 1995

By Fred Baldassare, Marcia Harris, Kenneth K. Eltschlager

Surface mine blasting was recently investigated as a potential source of high concentrations of stray gases found in nearby residences of western Pennsylvania. In one incident carbon monoxide was detected in a home and in the other, high concentrations of carbon dioxide were found in a home. Both carbon monoxide and carbon dioxide are by-products of blasting. However, other potential sources of these gases may also exist in a residential setting. In each case, gas chromatography (GC) and carbon isotopic analyses were used to define atmospheric concentrations inside the homes, and to determine the source of a stray gas. Molecular and isotopic analyses provide geochemical evidence as to the origin and source of the stray gas. This paper discusses elements of a stray gas investigation and the analyses necessary to identify the source of a stray gas.

By H. W. Frevert, A. C. Fieldner, S. H. Katz

"The Bureau of Mines, in its investigations of as masks for use in mines and allied industries tests masks that are voluntarily submitted by manufacturers for examination, and issues approval certificates for masks that meet the bureau's specifications. This paper describes the tests that were conducted on an ammonia gas mask by the Bureau of Mines, which successfully met all requirements and tests for ammonia, masks. The mask tested, known as the GMD ammonia gas mask, is manufactured by the Mine Safety Appliances Co., Pittsburgh, Pa. This ammonia gas mask, which forms a pocket over the face and allows breathing through the nose, consists of a face-piece with non-shatter eyeglasses; this is attached by means of a corrugated rubber tube to a canister supported on wearer's chest by a harness. The canister is green in color and is of tinplate construction. It was a disc valve at the bottom to prevent exhalation through the canister. The filling of the canister consists of a specially impregnated activated charcoal, about 750 c.c. in volume and weighing about 520 grunn. The material is supported above the check valve by a dome of wire screen covered with toweling. Above the granular material is a filter of absorbent cotton screens, and all materials are hold firmly in place by pressure from strong"

May 1, 1926

By Lloyd A. Morley, Alan M. Christman

General An important part of any mine power distribution system is its con¬nection to earth or ground. The grounding network serves to protect men and machinery from the hazards associated with electrical equipment which is operating improperly. Since the mine site is determined by the location of the rock or mineral to be extracted, the conditions required for the installation of an adequate grounding system are not always easily met. If annual rainfall is low or soil resistivity is high, an extensive array of buried metallic conductors may be necessary to assure a low-resistance connec¬tion to earth. Measurement of soil parameters can be made before the construction of a grounding grid is begun, and the configuration of a metallic network, which will yield the desired values of earth resistance and potential gradient, thereby ascertained. Proper design at the time the ground bed is installed will save much time and expense in later years. Ground conductors extend from the buried grid to each piece of mo¬bile and portable equipment via overhead lines or multi-conductor cables. In this fashion all machine frames are referenced to the same potential as the grounding medium. Protective circuitry must be installed to monitor\current flow in the ground conductors or the potential drop across the neutral grounding resistor, which is placed between the grounding grid and the neutral point on the distribution transformer secondary. When properly co-ordinated and used in conjunction with a low-resistance

Jan 1, 1976

Develop a method for mapping planar geologic features in deep underground mines where the presence of metal interferes with compass readings. Background A fundamental problem of mapping planar geologic features in deep underground mines is the presence of metal (water and air pipes, track, equipment, etc.), which affects the accuracy and consistency of compasses. Present geologic mapping methods include use of transits or theodolites, both of which are cumbersome and time consuming to use. To complicate the mapping, process each planar feature must be surveyed, and if that feature is not apparent on the opposite wall, it cannot be mapped. Another method of mapping is to stretch a tape measure between two survey spads and place a string along a planar feature on one wall and out into the opening until it intersects the tape measure. This method, in addition to being time consuming, is also inaccurate. Because detailed mapping of planar geologic features deep underground involves many repetitive measurements, a quick, accurate, and reliable method for making such measurements was necessary. The geolaser was developed to make such measurements in deep underground mines where metal interferes with conventionally used compasses.

Jan 1, 1990

To identify the most successful methods now in use for controlling respirable dust in longwall mines using double-drum shearers. Approach Conduct dust surveys at six longwall mining sections that use double-drum shearers and are regularly in compliance with the Federal Respirable Dust Standard, to identify effective dust control techniques. The selection of mine sites was based on recommendations provided by the Mine Safety and Health Administration. Instantaneous and short-term gravimetric instrumentation make it possible to isolate longwall dust sources and to determine the effectiveness of dust control techniques. (These procedures were developed by the Bureau of Mines, and are described in detail in Technology News Bulletins 134 and 135.) Production levels, and seam heights at each of the six longwall sections were: 53", 700 tps; 60", 800 tps; 72", 1000 tps; 79", 1500 tps; 84", 2000 tps; 96", 1500 tps. Survey Results Three effective dust control techniques were identified. 1. Shearer Operators on Intake Side of Lead Drum-At all mines surveyed, an important factor in controlling dust exposures at the shearer is the use of a cut ting sequence that allows the shearer operators to work most of the time on the intake air side of the lead drum. Dust profiles, like those plotted from data at two mines (see the graphs), show the large gradient in dust concentrations that can

Jan 1, 1982

By S. H. Katz

Artisans and laborers in mineral industries where the air is dusty with particles of reel: are subject to a peculiar pulmonary disease known as miners' phthisis or stone cutters' consumption. In granite cutters the disease is specifically designated as granite pneumoconiosis. Very fine particles of the harder rocks are especially injurious when inhaled into the lungs. It is estimated particles about one micron (1/23000 part of an inch in diameter) are most injurious, because larger particles are more readily removed by the cilia and,wet surfaces of the respiratory passages before reaching the lungs, while smaller particles either do not readily lodge or are more easily eliminated. Silica, of which quartz and flint are composed, and which forms a large part of granite, is one of the hardest of the common rock-forming materials. It is also very insoluble when silica lodges in the lungs elimination is difficult. Rock constituents of granite other than silica are probably injurious but in a lesser degree, and this is also probably true of limestone and the softer rocks. Ultimately a worker who daily inhales much granite dust has considerable deposited in his lungs. If he continues at his trade the lung tissue becomes harder and less elastic, he finds himself short winded, and in extreme cases death may come either directly or indirectly as a result of lung failure.

Feb 1, 1921

By S. M. Shelton, W. A. Calhoun, M. M. Fine, T. L. Johnston

"This report is () expansive test program by the Bureau of Mines to determine methods from various and ferrous manganese-grade product () widespread () and manfniferrous iron ores. Among the samples received for testing was one from the pits of the Barytes Mining Co., 1-1/ 2 miles northeast of Cartersville, Ga.. The property is approximately in the center of the Cartersville manganese district and shares a common corner with properties of the New Riverside Ochre Co. and the Etowah Development Co., both producers of manganifereus ores. The deposit is typical of the district and occurs in residual clays resulting from weathering of the Shady limestone and Weisner quartzite. 7/The property is developed by a number of open pits ranging to 60 feet in depth. In 1918 several carloads of manganiferous iron ore was mined from an alit on the property. Since then mining operations have been negligible. The ore is known locally as calico ore.A 4-ton sample representing -re as it occurs in the -pen pits vas furnished for testing. The sample consisted of a mixture of red iron oxides, wad, and clay, with small pebbles of manganese oxides and siliceous fragments scattered throughout."

Mar 1, 1943