Search Documents

By Harold R. Newman

The performance of Ecuador's mineral industry continued to be affected not only by depressed oil prices in recent years but also by natural disasters. In March 1987, Ecuador canceled foreign debt payments for the rest of the year and appealed for international aid because of a series of earth-quakes that destroyed villages and crippled the nation's oil industry. The earthquake destroyed a key section of the country's main oil pipeline and forced a halt to production and shipment of Ecuador's most important export product. Ecuador produces 240,000 barrels of oil per day and exports 144,000 barrels daily. Oil accounts for 60% of the nation's hard currency earnings. The Government of Ecuador asked the Organization of Petroleum Exporting Countries and other oil-producing countries to assume Ecuador's oil sales commitments. Ecuador agreed to pay the countries back in an equivalent amount of oil when it was able to resume exports.

Jan 1, 1989

By J. Hudy

The performance of six dense-medium washers was evaluated in five preparation plants. Three of the plants were making a two-product separation that produced a clean coal and a refuse; one plant employed dense-medium vessels in series to effect a primary and a secondary separation; and one plant was equipped with a two-compartment washer effecting two separations in one vessel. The separate secondary drum-type washer produced a low-ash metallurgical coal and an intermediate-ash product suitable for plant fuel or steam generation. The two-compartment washer produced a premium anthracite product and a middlings product. The sharpness-of-separation values ranged from good to excellent for the five primary separations and for the secondary separation.

Jan 1, 1968

Reduce shaft sinking costs and workers exposure to mechanical hazards, drill dust, blast dangers, and fumes. Approach Replace drilling and blasting by using a large, cab-mounted impact breaker suspended from the bottom work deck of the galloway. How It Works The pneumatically actuated impact breaker is positioned by an articulated boom con-trolled from an operators cab. The breaker delivers 2,000 ft-lb blows that fragment the rock at the shaft bottom. Mucking is accomplished by a backhoe bucket on an articulated boom mounted on the cab. See photograph. The mucked material can be removed either by dumping into a previously drilled borehole or by being lifted out in a muck bucket as shown in the drawing. Positioning of the breaker, rotating the cab around its vertical axis, and moving the cab support frame around the perimeter of the shaft are all controlled by one joystick. Separate controls position the mucker boom, which can be swung horizontally through a 180° degree arc towards either side of the cab. Because the cab can be rotated to any position around its vertical axis, and can also be moved in a horizontal circle around the shaft, virtually any position on the bottom of the shaft can be reached by the breaker and mucker.

Jan 1, 1981

By O. P. Hood

The smoke problem means different things in different places . In the neighborhood of industrial plants , especially smelting plants and cement plants , the term " smoke " is applied to material discharged from these plants , consisting of a mixture of solid particles ( dust ) , fume which has condensed from vapors , and gases of various kinds that are produced in the operations . In the ordinary use of the word , however , " smoke" refers to the visible material which escapes from the burning of coal . White smoke usually owes its color to small drops of water which have condensed from the water vapor that it formed in the burning of coal . When smoke is black, the color is due to unconsumed particles of carbon and usually when the smoke problem is spoken of , it is this black smoke produced in the burning of coal that is referred to , Many inquiries in regard to smoke are addressed to the Bureau of Mines , and the following brief summary has been prepared as covering the usual questions . For references to the smoke problem in England , I am indebted to a recent interesting paper on this topic by David Brownlie .

Feb 1, 1922

By Nicholas Kyriazi

Significant portions of the present Federal regulations for certification of closed-circuit breathing apparatus (42 CFR 84) are not quantitative. The human-subject testing portion of the regulations specifies activities rather than metabolic work rates; however, heavy human subjects have higher oxygen consumption, CO2 production, and ventilation rates than lighter human subjects performing the same activities. This means that apparatus certified using different human subjects have effectively passed different tests. In addition, apparatus performance is monitored only during selected intervals of testing, and always during rest, rather than during the entire performance period. Further, testing is arbitrarily terminated at specific rated durations, leaving unknown the performance during the remaining duration. Duration itself is misleading to users who believe that the apparatus will last a certain time no matter how much they weigh or how hard they work. The actual duration obtained from an apparatus, however, is highly variable, being inversely proportional to the work rate at which it is used. In this report, recommendations are made to (1) replace the present regulations for certification of closed-circuit breathing apparatus with quantitative tests specifying metabolic work rate rather than activity,(2) continuously monitor relevant physiological stressors, (3) continue testing until exhaustion of the oxygen source, and (4) classify closed-circuit breathing apparatus by quantity of usable oxygen, i.e., capacity, rather than by duration. Physiology-based stressor levels are suggested as well.

Jan 1, 1999

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

3. Preliminary Evaluation of Mine Sealing Techniques As the first stage in the development of a technique for the remote sealing of mines, a state-of-the-art survey of various mine sealing techniques was conducted. This was expanded to include a review of different materials offering some potential for use as a mine sealant. Techniques for the remote placement of materials for other applications were evaluated, and system concepts for dis¬tributing remotely placed materials were developed. This preliminary review led to the development of a functional description of a general mine sealing technique to meet the specified conditions. Various potential system configurations were synthesized. These were subjected to a preliminary evaluation based on estimated confidence in system performance, development risk, cost, and sealing time. Based on this preliminary evaluation, promising mine¬sealing techniques were selected for further development. This section presents a review of the following: (a) Techniques for constructing permanent seals from within a mine. (b) State of the art in remote sealing for mine fire control. (c) Techniques for remote placement of materials for other applications. (d) Systems for distributing remotely placed material. (e) Materials for mine sealing. (f) Synthesis of remote mine sealing concepts.

Jan 1, 1973

By Jon K. Ahlness

The Bureau of Mines, in cooperation with the Institute of Mineral Research of Michigan Technological University, and the Upper Great Lakes Regional Commission, conducted an investigation of electronic sorting of native copper ore from Upper Michigan. This report is based on research by the Institute of Mineral Research under contract to the Bureau. The test program evaluated the use of belt and rotary sorters on various size and grade fractions of ore. Both plant-scale sorting and lab sorting tests were run. The plant sorting objectives were to determine the sortability of different ores and the efficiency of the electronic ore sorters. High-and low-grade ores from both conglomerate and amygdaloid types were separated into four size fractions. The two larger sizes were sorted on belt sorters and the two smaller ones on rotary sorters. Copper recoveries ranged from 20.0 pct from a feed grade of 0.40 pct to 80.3 pct from a feed grade of 1.08 pct. Lab sorting tests of conglomerate ore were run to determine the efficiency of a belt sorter equipped with a second sensing coil located above the belt and to determine the sorting characteristics of larger ore size fractions than those used in the plant sorting. Copper recoveries from the combined feed sizes ranged from 47.0 pct from a feed grade of 0.13 pct to 96.8 pct from a feed grade of 4.87 pct. For all the ore types except one, it was found that the copper recovery increased with the feed size.

Jan 1, 1980

By T. F. Tomb

This paper describes field and laboratory investigations conducted on a dust-collection system recently designed for integral use with a continuous mining machine. The results of the field study showed that the average respirable dust concentration measured at the machine operator's position was reduced by about 60 percent (from 8.7 to 3.5 milligrams per cubic meter), and total and respirable dust concentrations in the return air were reduced by approximately 70 percent. The data indicated that approximately 20 percent of the dust generated at the face was not passed through the scrubber. The lab-oratory results showed that the overall efficiency (by particle count) was approximately 80 percent for total dust concentrations (minus 20 micrometers in size) typical of those encountered underground. Calculations based on total dust concentrations measured during the underground study indicated that the respirable mass concentrations of the effluent from the scrubber would still exceed acceptable levels even if scrubbing of all the air at the face were possible.

Jan 1, 1973

By William Wiehagen

This trainer?s guide is designed as a reference manual. The purpose is to offer information and examples to skills trainers to assist them in structuring training for new operators of Walk-Thru roof bolting machines. Trainers can use this manual as a resource for helping trainees learn, understand, and apply knowledge and skills. In this sense, the guide is not prescriptive. It is designed to offer information and trigger ideas on what might be done to accelerate learning to those who are new to the roof-bolting task. On-site trainers can modify this guide to fit their conditions, machines and equipment, and work procedures. They can integrate roof control plans, company policies and procedures, and operators? manuals from the manufacturers of the original equipment into this guide. Every trainee is different and will come to the job with varying levels of relevant knowledge and skills. The trainer?s decisions on where to start, how to organize the on-the-job and classroom training portions, and when and how to offer different aspects of the training will be based on (1) a pretraining assessment of the trainee?s knowledge and skills and (2) the trainer?s experience in conducting skills training. The ?Skill Check? section might be useful for deciding where training should start among miners who have underground experience but limited knowledge of roof-bolting techniques. Every job carries a learning curve and likely has a number of ?teachable moments? where significantly new knowledge and skills can be learned.

Aug 1, 2006

By C. Özgen Karacan

Methane emissions from a longwall ventilation system are an important indicator of how much methane a particular mine is producing and how much air should be provided to keep the methane levels under statutory limits. Knowing the amount of ventilation methane emission is also important for environmental considerations and for identifying opportunities to capture and utilize the methane for energy production. Prediction of methane emissions before mining is difficult since it depends on a number of geological, geographical, and operational factors. This study proposes a principle component analysis (PCA) and artificial neural network (ANN)-based approach to predict the ventilation methane emission rates of U.S. longwall mines. Ventilation emission data obtained from 63 longwall mines in 10 states for the years between 1985 and 2005 were combined with corresponding coalbed properties, geographical information, and longwall operation parameters. The compiled database resulted in 17 parameters that potentially impacted emissions. PCA was used to determine those variables that most influenced ventilation emissions and were considered for further predictive modeling using ANN. Different combinations of variables in the data set and network structures were used for network training and testing to achieve minimum mean square errors and high correlations between measurements and predictions. The resultant ANN model using nine main input variables was superior to multilinear and second-order non-linear models for predicting the new data. The ANN model predicted methane emissions with high accuracy. It is concluded that the model can be used as a predictive tool since it includes those factors that influence longwall ventilation emission rates.

To provide a means for mechanically separating and recovering nonferrous metals continuously from non-magnetic reject material produced at scrap automobile shredding facilities. Approach The Bureau of Mines developed a water elutriator system that separates metals from shredded scrap auto-mobiles based on differences in specific gravities. A premium-quality product, containing aluminum, magnesium, lead, zinc die cast, copper, copper alloys, and stainless steels, is obtained. How It Works Mixed nonmagnetic reject material currently being separated at automobile shred-ding facilities is introduced onto the top of an upwardly flowing vertical column of water. The water, overflowing a weir in the top of the vertical column, carries with it the floating, lightweight waste materials, mostly combustibles, while the heavier pieces sink through the rising water. Medium-density substances such as glass, rubber, and heavy plastics are carried off through a side port, located in the upper third of the column. The cleaned, mixed metal product sinks to the bottom and is continuously removed from the base of the column with a bucket elevator having perforated buckets. All three categories of material are removed from the system on separate wire mesh belt conveyors. Most of the water drains through the belts into a holding tank and, after settling, is recirculated back through the elutriator column. The purity and recovery of the metal product are influenced by two elutriator operating variables: the flow rate of water through the vertical column, and the height of the overflow weir at the top of the column.

Jan 1, 1983

By Douglas C. Peters, Valois R. Shea-Albin, Dennis R. Dolinar

An accurate assessment of the vertical stress on a coal seam at depth is important for mine design. Vertical stress calculation techniques presently available either are not sufficiently accurate or cannot handle complex surface topography. Therefore, the U.S. Bureau of Mines developed a computerized method to calculate vertical stress exerted on surfaces at depth that includes the effect of topography. Two input data sets are required: a digital elevation model containing topographic elevations and a coal seam file defining coal seam elevations at depth. Boussinesq's equation then quantifies the vertical stress resulting from topography. The computerized method was tested on a coal seam overlain by a complex topography where a vertical stress map encompassing several square miles was produced. Results show that depth mitigates the affects of surface topography, while the coal seam topography has a direct effect on the vertical stress. In comparison to the computerized method, the direct stress method overestimates stress under hills and underestimates stress under valleys. The largest difference between the two methods occurs under the steepest topographic relief. A limitation of the computerized method is that stresses cannot be accurately determined near an outcrop.

Jan 1, 1992

Provide a means for continuous measurement and display of respirable dust concentrations in a mine so that when high dust levels occur, timely, corrective measures can be taken. Approach Develop a personal dust monitor that (1) is small and light enough to be worn by a miner, (2) has the capability to continuously measure the respirable fraction of coal dust, (3) will display the respirable dust concentration in mg/m3, and (4) can store the average respirable dust concentration and sampling time of several sampling shifts for later play-back. How It Works The personal dust monitor (PDM-1) uses light scattering and convection air currents to sample the respirable fraction of coal dust. Convective air currents cause dust laden air to pass through an open-celled sampling chamber (light sensing chamber). A near infrared light emitting diode (LED) located in the PDM-1 emits pulses of light. The pulsed light passes through a focusing lens and glass window into the sampling chamber. The light is then reflected, scattered, and refracted by the airborne dust particles. Light scattered within the angles of 450 to 900 (the angles within which the intensity of the scattered light is most closely related to respirable-size dust particles) passes through another window and is focused on a light detector. The light detector signal is amplified and presented as analog output voltage for conventional recording. This signal is also converted to a digital signal which the microprocessor uses with its crystal clock to calculate the 10-second average dust concentration, the shift average concentration, the time-weighted average concentration, and the elapsed sampling time. The microprocessor also stores dust concentrations of the seven most recent sampling periods, controls the operation of the LED and detector, and operates the liquid crystal display (LCD).

Jan 1, 1983

By H. H. Schrenk, Carlton E. Brown

"INTRODUCTION The question as to whether or not the flow of water through pneumatic rock drills commonly used in this country keeps to a minimum dust disseminated into the air during drilling arose during a study of the dust-in-air conditions in Butte mines from February to July 1936 and December 1936 to June 1937 made by the Bureau of Mines in cooperation with the Anaconda Copper Mining Co., Butte, Mont, The purpose of this report is to describe the study, including some experimental work on the subject, and to give test results.ACKNOWLEDGMENTSThe help of the ventilation department of the Anaconda Copper Mining Co. in planning the study and collecting the data is gratefully acknowledged.EXPERIMENTAL CONDITIONSTests were conducted in an untimbered 6- by 8-foot crosscut in medium-hard granitic rock near the shaft station on an inactive level of one of the active Butte mines. Figure 1 shows the plan and section of the test location. Air was drawn from the shaft at the station, through the crosscut, and up through another shaft. The flow of air through the crosscut was decreased by a brattice downstream from the sampling location, so that relatively high, easily measurable dust concentrations would be obtained in the tests. Impinger samples for determing concentration of dust in the air were collected in an opening 51 inches wide, 29 inches high, and about 4o inches from the top of the rails in a wooden stopping about 16 feet downstream from the place where the test holes were drilled."

Apr 1, 1938

By Ronald D. Hill, Elmore C. Grim

1.In 1972 over 595 million tons (51+0 million metric tons) of bituminous coal were mined; 49% of this tonnage was obtained by surface mining methods. Authorities have predicted that the tonnage of surface mined coal will increase in the future, especially since oil and gas resources are becoming limited. 2. Demands for clean air have increased mining activities in the low-sulfur coal deposits in the West. Pollution problems arising from these operations will be considerably different than those found in the East. The deposits are located in arid to semi-arid regions. Coal seams are generally aquifers and are a principle source of fresh water. Therefore mining may result in alteration of groundwater distribution patterns by aquifer disruption. In general, pollution problems associated with western mining are not well characterized. 3.Since any disturbance of the surface will alter the environment in the vicinity of the disturbance, pre-mining planning is a prerequisite to any environmentally successful surface mining operation. If properly carried out, the adverse social, economic, and environmental effects of coal surface mining will be minimized. Certain land areas will be unsuitable for surface mining where: a.Reclamation is not physically or economically possible. b.Mining is incompatible with existing land use plans. c.The proposed mining area is of critical environmental concern. Core drilling is the most satisfactory method of obtaining accurate information for pre-mining planning. 4. Unaccountable strip mining in the past has created problems that are still present today. Contour mining methods that involve the indiscriminate dumping of overburden on the downslope is one of the largest single sources of sediment from strip mining. However, land disturbed by strip mining can be reclaimed. Techniques have been and are being developed by which mining and reclamation are integrated into a single operation. Mountain top removal, head-of-hollow fill, and block cutting are examples in contour surface mining. These methods drastically reduce pollution problems associated with contour stripping.

Jan 1, 1974

By Harry Dobroski, Larry G. Stolarczyk

Theoretical and experimental research sponsored by the U.S. Bureau of Mines shows that medium frequency (MF) electromagnetic (EM) signals propagate great distances in an underground environment such as a tunnel or mine. This propagation is enhanced by different mechanisms associated with the geology, and with the existence of metallic conductors in the entryways. In stratified geologies, a transverse electromagnetic (TEM) mode of signal propagation is possible if a low conducting layer is bounded above and below by higher conducting layers. In general, the difference in conductivities must be at least several orders of magnitude. Such geological waveguide conditions often exist in underground mines. Propagation via the waveguide effect is known as the "seam mode" of propagation. Another mode of propagation, the "tunnel mode," exists in underground entries with electrical conductors such as power cables, metal pipes, and phone lines. A monofilar mode of propagation exists when signals are impressed upon conductors and return via the surrounding rock. A bifilar mode of propagation exists when all signals exist only on local conductors. In a given location there is a combination of monofilar and bifilar modes that make possible an interaction between the conductors and a transmitting device in a tunnel or entryway. Signals can be impressed on or received from local conductors via magnetic dipole antennas (loops) or line couplers.

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

By R. R. Sayers

The terms "sanitation and }\Vgienen are often used interchangeably, but it is more "' usual to apply ttsani tat ion'' to th environment or surroundings, and nr.ygieneto the iiiividual, The subject,. h9wever, is so broad that only a few of the phases of sanitation will be di.acusae in ·this paper, vmile the various Fsea of hyg:tene will be deferred for later consideration. One of the bes.t .iaf ini tions of sanitation that I have hearci was given by ur. L. L • Lumsden, of the U, S. Public Heal th Service, who state.d that "'sanitation is t-he c.oir .. 'Don-sens$ application of the principles of cleanliness,

Aug 1, 1922

By an Slo, J. J. Forbes

"INTRODUCTION This is the first of a series of information circulars dealing with the control of roof and the prevention of accidents from falls of rock and coal. These circulars are being published to focus attention of the coal-mining industry on this most prevalent source of fatalities and injuries and to present factual information that should be helpful in reducing loss from these causes.Records of fatal accidents in the coal mines of the United States, from all causes, have been kept since 1906; during this period approximately 30,000 men have been killed by falls of rock and coal in the bituminous-coal mines, and more than 7,000 men have lost their lives in the Pennsylvania anthracite mines from the same causes. From 1906 to 1930, about 900 men were killed annually by falls of rock and coal in bituminous-coal mines, and about 200 men were killed annually in anthracite mines during the same 25-year period. From 1931 to the present time, the number killed annually from falls of rock and coal has averaged more than 500 men in bituminous-coal mines and about 125 men in Pennsylvania anthracite mines.Numerically the record of accidents from falls of rock and coal shows improvement, but on a percentage basis and on a million-man-hours-of-exposure basis little, if any, improvement has been made during the past 40 years. The cold fact is that, year after year, about 50 percent of all those killed in coal mines in the United States lose their lives from falls of rock and coal."

Apr 1, 1948

By H. C. Loesche

The problem of signaling to the hoisting engineer from the cage in a shaft mine has been given considerable thought and attention by engineers and mine operators seeking to Increase the safety and efficiency of hoisting. HISTORY R. L. Rutherford,3/ an employee of the Magma Copper Co., Superior Ariz., realizing the need for a simple and practical moving-cage signaling system, began a serious of experiments early in 1937, Available electrical moving-cage signal in operation at this date required that signal wires be installed in the shaft to make a simple, positive signal without wires, the first experiments used the pipe lines in the shaft for carrying the signal current, but these experiments were not successful.

Jan 1, 1945