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By Lisa Steiner, Robin Burgess-Limerick

In 2004, underground coal mines in the United States reported 3,405 injuries to the U.S. Mine Safety and Health Administration (MSHA). Of these, 17 percent were associated with the use of bolting machines, 8 percent with continuous miners, and 4 percent each with scoop/load-haul-dump (LHD), shuttle cars and personnel transport. Analysis of the injury narratives identified five hazards that required attention. They are rock falling from supported roof inadvertent or incorrect operation of bolting machine controls, handling continuous miner cable, collisions while driving underground vehicles and driving or traveling in underground vehicles on rough roadways. The rate of lost-time injuries has steadily decreased during the past 10 years (from more than 10 per 100 FTE in 1995, to six in 2004). However, underground coal mining remains a hazardous industry. One of the contributors to this elevated injury risk is working with or near underground coal mining equipment. Roof bolting machines and continuous miners have been consistently identified as high risk equipment. They account for approximately 24 percent of all injuries to underground coal miners (Sanders and Shaw, 1989). LHD's, shuttle cars and personnel transports are also associated with injuries in underground coal mines (Burgess-Limerick, 2005). Conventional analyses of injury statistics typically provide tables detailing the breakdown of injuries by body part nature of injury or mechanism of injury. Such analyses are worthwhile and may be helpful in tracking broad trends over time. Further information is available in the narrative text field completed for each injury reported. The detail contained in these narratives varies. However, they generally provide some insight into the causes of the injury, such as the activity being performed at the tune of

Use water-jet-assisted cut-ting technology to reduce the exposure of mi ne workers' to respirable dust. Approach Install water-jet-assist on mining machines and evaluate its impact on respirable dust. How It Works Water-jet-assisted cutting involves a mechanical cutting bit working in combination with a moderate pressure (generally up to 10,000 psi) water jet directed just in front of, or through, the bit tip. One of its advantages is reduced dust generation because the jet wets the face of the material being cut more efficiently than a conventional low-pressure water spray, thus capturing much of the dust before it ever becomes airborne. It also removes loose cuttings ahead of the bit before they are pulverized by the bit into respirable dust. Total water consumption is about the same as for conventional low pressure dust control water spray systems. However, there is some increase in power consumption because of the energy needed to provide the high pressure water.

Jan 1, 1987

By C. W. Owings, J. J. Forbes

"INTRODUCTION The recent coal-dust explosions in Illinois and Indiana have again brought forcibly to the attention of mining men the fact that mines which liberate little or no methane can have widespread explosions, if dry and dusty conditions exist and if adequate measures are not taken to control the dust hazard by rock dust¬ing or use of water.Even though rock dust has been used more or less extensively for more than 20 years as a means of limiting or preventing coal-mine explosions, many mine operators have requested information on rock dusting and means of allaying coal dust at its source. The purpose of this circular is to summarize available information on these two methods.COAL MINES TO BE ROCK-DUSTEDAll nonanthracite coal mines must be rock-dusted, except those mines or locations in a mine that are too wet or too high in incombustible content to propagate an explosion.Coal dust that contains 20 percent or more moisture may prevent ignition or propagation of an explosion. Such dust can be molded in the hands, and under such condition the roadway would be considered muddy. Mine dust that is only damp is not wet enough to prevent propagation of an explosion. Beads of water standing on accumulations of dust are not indications that the dust is wet. Only those mines or locations in a mine in which the coal dust can be molded in the hand need not be rock-dusted."

Jun 1, 1947

By Rose L. Ballard

This chapter summarizes data on crude non fuel mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rico. Included also are the tables that show the principal non fuel mineral commodities exported from and imported into the United States and that compare world and U.S. mineral production, The detailed data from which these tables were derived are contained in the individual commodity chapters of Volume I and in the State chapters of Volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at any of several stages of extraction and processing the stage of measurement used in this chapter is what is normally termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the output from auxiliary processing at or near the mines.

Jan 1, 1986

By Hillary W. St. Clair

The effective coefficient for rate of reduction of a sample of granular iron ore may be determined by passing the reducing gas through a bed of the are at constant flow rate and periodically analyzing the effluent gas, The method of analyzing the data is based on a mathematical model that takes into account the variation in composition of the gas and solids with time and position in the bed. A method is described for determining the value of the rate coefficient that gives best agreement between the observed and calculated analyses of the effluent gas.

Jan 1, 1967

By S. J. Pearce

"INTRODUCTION AND SUMMARYComplaints have been made regarding dust respirators that may be used in coal-mining operations. Some of these complaints may be due to improper use of the respirator, inadequate knowledge of its purpose and mode of functioning, poor choice, poor fitting, or inadequate maintenance. It is hoped that this circular will answer these complaints by discussing the various factors relating to the proper use of dust respirators in general and in coal mines in particular.It is pointed out that dust respirators are not to be used as a substitute for dust-control measures. The construction, functioning, choice, fitting, and maintenance of dust respirators are discussed.FIELD OF USEThe function of the dust respirator is to prevent the wearer from inhaling harmful quantities of dust by removing dust from the air he inhales.A dust respirator is not to be used as a permanent substitute for dust-control measures. It is to be used as a temporary substitute until dust-control measures can be instituted or as a protective means where dust-control measures are impracticable, as in applying rock dust in bituminous-coal mines.The following sections of the ""Federal Mine Safety Code for Bituminous-Coal and Lignite Mines in the United States"" 2/ emphasize the fact that every effort should be made to keep the amount of dust in the air of the working places as small as possible:"

Mar 1, 1950

By Vijia K. Karra, John J. Sammarco, Robert Paddock, Edward F. Fries

Workers in hazardous environments such as mining are constantly exposed to the health and safety hazards of dynamic and unpredictable conditions. One approach to enable them to manage these hazards is to provide them with situational awareness: real-time data (environ-mental, physiological, and physical location data) obtained from wireless, wearable, smart sensor technologies deployed at the work area. The scope of this approach is limited to managing the hazards of the immediate work area for prevention purposes; it does not include technologies needed after a disaster. Three critical technologies emerge and converge to support this technical approach: smart-wearable sensors, wireless sensor networks, and low-power embedded computing. The major focus of this report is on smart sensors and wireless sensor networks. Wireless networks form the infrastructure to support the realization of situational awareness; therefore, there is a significant focus on wireless networks. Lastly, the “Future Research” section pulls together the three critical technologies by proposing applications that are relevant to mining. The applications are injured miner (person-down) detection; a wireless, wearable remote viewer; and an ultrawide band smart environment that enables localization and tracking of humans and resources. The smart environment could provide location data, physiological data, and communications (video, photos, graphical images, audio, and text messages).

Jan 4, 2007

Prevent the explosion of methane gas or coal dust by replacing air with inert gas inside highwall mine excavations. Approach Use combustion gases as a source of inert gas with low oxygen content to blanket the cutting, head of highwall mining machines. This gas is placed strategically at the collar of the excavation where it enters the hole to replace the mined coal volume. The elimination of oxygen from the hole prevents explosions of gas or dust. How It Works Highwall mining methods arc used when surface mining becomes uneconomical. One method of highwall mining involves use of a horizontal auger to enter the coalbed from a surface mine bench. The coal is mined in a series of horizontal, parallel, and large-diameter holes. Historically, little methane has been associated with auger mining. However, mining technology has extended the reach of auger mining, which can increase the occurrence of methane. Methane explosions at auger mining operations have been increasing. Methane has been the primary fuel source of these ignitions, but coal dust also may have been involved.

Jan 1, 1993

By Kenneth J. Miller

The Bureau of Mines conducted an investigation to improve the flotation response of coals that are difficult to wash by froth flotation. A literature survey and experimentation showed that, for the most part, refractory coals can be floated with oily collectors and frothers. Collector reagent consumption can be minimized and the selectivity of the flotation enhanced by assuring adequate, but not prolonged, reagent conditioning. Where flotation selectivity is especially poor, two-stage rougher-cleaner flotation is recommended. It was concluded that a major problem with refractory coals is predicting when they will appear in a flotation circuit so that supplementary flotation collectors can be added. Coal losses due to variation in the floatability of the feed might be reduced if a nonpolar collector such as kerosine or fuel oil is used along with a frother as general coal flotation practice.

Jan 1, 1977

By W. H. Lewis

This Bureau of Mines report and its companion report (Information Circular 9074) have been prepared as a complete reference on underground coal mine lighting. This report discusses the fundamentals of light and its interrelationship with the visual process. The purpose of the report is to insure an understanding of the numerous complex and interrelated factors that must be considered to design and implement a mine lighting system that will satisfy human needs for good vision and comfort. Topics include history, objectives, and technical considerations of coal mine lighting; light physics; light and vision relationships; and disability and discomfort glare.

Jan 1, 1986

By G. R. Hopkins

One of the largest items in the expense of operating a refinery is the cost of the fuel used in distillation and for miscellaneous purposes such as in the heating of buildings and in the generation of electricity. On a B. t. u. basis, the average refinery consumes approximately one-tenth as much fuel as it produces. Theoretically, the fuel consumption at refineries should be much smaller than this, but furnaces can not be designed to be 100 per cent efficient and, in addition, a large part of the waste heat is low-temperature heat which would not pay for the expense of recovering it. Annual surveys of fuel consumption at refineries have been made by the United States Bureau of Mines, beginning with 1925. During the 5-year period, 1925-1929, the refineries made steady progress in fuel economy. This is evidenced by the computed figures of heat requirement per carrel of crude oil refined, which show a decline from 829,000 B. t. u. in 1925 to 639,000 B. t. u. in 1929 (see fig. 1). In 1930, however, 'the trend in fuel economy was reversed and the quantity of heat utilized in refining the average barrel of crude oil rose to 672,000 B. t. u. There were undoubtedly a number of reasons for the apparent decrease in fuel economy at refineries in 1930, chief of which were the tendency to carry the distillation farther instead of merely topping the crude and a gain in the consumption of waste oils, such as acid sludge, which in actual practice yield less heat per unit consumed than has been theoretically assigned to oil.

Jan 1, 1931

Reduce potential for steering errors during tramming of articulated vehicles, particularly when the operator is seated to the rear of the machine pivot point and is tramming in reverse. Approach Position-sensing and feedback cylinders were applied to the steering cylinders of two S&S cleanup tractors to cause the steering-control lever to match the orientation of the vehicle sections. The vehicles were tested in two working mines. How It Works A position-sensing cylinder (see Figure 1, Item A) is attached to one of the steering cylinders in the cleanup tractor steering system. As the steering cylinder piston rod is actuated by movement of the control lever, hydraulic oil flows from the position sensing cylinder to the feedbck-cylinder (B), causing the feedback-cylinder piston and rod to move. The outside end of the rod repositions the the steering-control lever until its angular position corresponds to the orientation of the vehicle sections.

Jan 1, 1978

By Ronald D. Hill, Elmore C. Grim

The removal of overburden often exposes pyritic materials (iron disulfide). As shown in equations 1 and 2, the oxidation of this material results in the production of ferrous iron and sulfuric acid. The reaction then proceeds to form ferric hydroxide and more acid, as shown in equations 2 and 4. [ ] Consequently a low pH water is produced (pH 2-4.5). At these pH levels, the heavy metals such as iron, manganese, copper, and zinc are more soluble and enter into the solution to further pollute the water. Water of this type supports only limited water flora, such as acid-tolerant molds and algae; it will not support fish life, destroys and corrodes metal piers, culverts, barges, etc., increases the cost of water treatment for power plants and municipal water supplies, and leaves the water unacceptable for recreational uses. The amount, and rate of acid formation, and the quality of water discharged are a function of the amount and type of pyrite in the overburden and coal, time of exposure, characteristics of the overburden, and amount of available water(l). Crystalline forms of pyritic material are less subject to weathering and oxidation than amorphic forms. Since oxidation by oxygen is the primary reaction during early acid formation, the less time pyritic material is exposed to air, the less acid is formed. Thus, a positive preventative method is to cover pyritic materials as soon as possible with earth, which serves as an oxygen barrier. In terms of mining, this step is accomplished by current reclamation techniques and small open pits.

Jan 1, 1974

By Larry Patts, Michael J. Brnich

Approximately 45% of U.S. coal is produced from underground mining. The use of diesel engines to power under- ground mining equipment has steadily increased over the past four decades in an effort to improve mine safety and productivity. Several advantages realized with the use of diesel-powered mining equipment in underground coal mines are listed in Table I. The primary disadvantage of using diesel equipment in underground coal mines is that diesel exhaust emissions can contaminate mine ventilation air. The major constituents of diesel exhaust are gaseous emissions (which include carbon monoxide, carbon dioxide, oxides of nitrogen, sulfur oxides and unburned hydrocarbons) and diesel particulate matter (DPM). The Mine Safety and Health Administration (MSHA) has incorporated threshold limit values for all gaseous components of diesel exhaust into their regulations. These have been established by the American Conference of Governmental Industrial Hygienists.

By Henry M. Harris

The Bureau of Mines investigated a glass containing approximately 17 percent lithia and 83 percent silica to establish a method of devitrifying cast and rolled shapes. Glass shapes with high strength were made by melting, forming, and rapid cooling of the composition, and the shapes subsequently were converted to a crystalline condition by heat treatment. The best devitrification schedule included rapid cooling of the glass to below 300° C, followed by reheating at a rate of 50° to 400° C per hour, depending on the size of the shape, followed by a of 60 to 70 hours at 500° C and another period of 15 hours at 800° C. attempts to use faster heating rates or slow cooling to accomplish devitrification in deformation of the shapes. The crystalline shapes had flexural strengths that averaged over 33,000 psi, achieved with an annealing time of 60 to 70 hours at 500° C.

Jan 1, 1965

By Francis R. Redfern

Newton's method of solving a nonlinear equation is employed to develop a least-squares acoustic emission source location method in which the spatial residuals of the location equations are minimized. These residuals, related to the distances from the least-squares source location perpendicular to the surfaces described by the location equations, permit location error to be estimated to first order along the spatial axes. The solutions obtained by this method are the best spatial solutions to the location equations in the least-squares sense. Also presented is a procedure by which the geometrical control of a transducer array can be evaluated using the rate of change of source location with fractional velocity change.

Jan 1, 1982

By Ann G. Kim

Hydrocarbon gases, primarily methane but also the Ca through Cs paraffins, the Ca and C3 olefins and possibly the C4 and Cs olefins, are byproducts of coal formation. Although it is generally believed that coal formation occurred at temperatures below 200° C, most experimental work on gas formation from coal has been performed at temperatures between 200° and 1,000°C. The objective of this Bureau of Mines experiment was to determine if observable changes in the gases from coal could be produced at temperatures below 200° C in relatively short periods of time. The experiment involved heating coal samples from six coalbeds at constant temperatures and analyzing evolved gases. The composition of the gases at three temperatures was compared. At 35° C, over 99 pet of the gas is methane; at 125° and 150°, methane constitutes approximately half of the hydrocarbon gas. Isobutane and pentane are the predominant higher hydrocarbons at temperatures between 100° and 150° C.

Jan 1, 1974

By D. L. Paulson

The Bureau of Mines is investigating pyrometallurgica1 and" chemical methods to recover valuable constituents from metallurgical dusts and slags. Under this program a technique was developed to recover iron from molten copper smelting furnace slags by carbon injection. Slags from gas-fired reverberatory and electric copper smelting furnaces were treated in an 800-kva electric-arc furnace by injecting coke breeze into the bottom of the molten bath. Over 95 pct of the iron and over 90 pct of the copper contained in the smelting furnace slags were recovered, while up to 85 pct of the carbon injected into the system was utilized. It is anticipated that the metal product containing approximately 95 wt-pct iron and 2 wt-pct copper will be a satisfactory medium for recovering copper by cementation.

Jan 1, 1977

Improve safety at mineral operations that use cyanide leach solutions to recover precious metals from finely ground ores, Approach Provide an alternative, non-acidic means of cleaning processing systems such as the State-of-Maine filter system, thereby reducing the exposure of workers to toxic hydrogen cyanide gas (HCN), The Problem Many gold and silver mining operations use cyanide solutions to dissolve gold and silver from ores. The precious metals frequently are recovered from pregnant leach solutions by the Merrill-Crowe recovery process, whereby gold and silver is precipitated with zinc dust. When that method is used, suspended particles in the leach solution must be filtered out before zinc precipitation can occur. This filtering is accomplished with small packaged plants, such as the State-of-Maine (SOM) filtering system. Unfortunately, the filters become clogged with calcium carbonate scale after about 2 to 10 days of operation and must be cleaned before further precious metals recovery operations can continue, Cleaning the system is a hazardous task because the acid is not compatible with the alkaline cyanide leach solutions, and toxic hydrogen cyanide (HCN) gas may be produced when the acid and solution are mixed. That gas, if breathed or contacted with the skin, can cause cyanosis which may induce nausea and even asphyxia and death. To reduce this danger, the Bureau of Mines has devised a safer method of cleaning clogged filters,

Jan 1, 1986

By D. Montagna

Large quantities of zinc-base die-cast scrap containing 3 to 4 percent aluminum are presently refined by mixing with other secondary zinc products such as galvanizer dross and distilling in a retort. The Bureau of Mines investigated alternate aluminum removal processes utilizing low-cost fluxes. Basing the investigation on the metallurgical principle that a reactive impurity can be removed from a less reactive matrix metal by melting under a flux consisting of a salt or oxide of a metal less reactive than the impurity, three separate flux mixtures were studied. In the first flux system, [FeCl3] + NaCI (the active component is underlined), part of the aluminum is' eliminated by the formation of volatile aluminum chloride and the rest by the creation of a high melting point iron-aluminum intermetallic compound that can be separated from the remaining molten zinc by filtration. Aluminum removal in the second system, [Fe203] + CaClz + NaCI, is effected by the formation of the iron-aluminum compound and possibly aluminum oxide. The third system, spent sal skimmings--essentially a mixture of [ZnCl2], NH4Cl, and ZnO, depends solely on aluminum chloride formation. Of the three flux systems investigated, the best results obtained were with system 3. Aluminum was reduced in the molten die-cast alloy from 4.10 percent to 0.01 percent when depleted sal skimmings were used.

Jan 1, 1969