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Maintain good blowing face ventilation while taking deeper cuts with a radio-remote, scrubber-equipped miner. Approach A six week in-mine study of face ventilation effectiveness was made by comparing the existing MSHA-approved blowing curtain setback distance of 25 ft with brattice set back distances of up to 50 ft. Effectiveness was determined by measuring methane levels at the face and in the immediate return. How It Works Blowing ventilation systems are commonly used in mines because the high velocity air stream created by these systems rapidly mixes with and dissipates methane generated during the cutting of coal. A drawback to blowing ventilation is that the work area is placed in return air and this may create dust compliance problems for the shuttle car and mining machine operator. To clean dust from the return a number of mining machine manufacturers supply dust scrubbers built into the machine. Dust-laden air is drawn into ducting at the front of the mining machine's boom and is ducted to a scrubbing unit located on the machine's main frame. The clean air from the scrubber is discharged as a high velocity jet toward the return, generally from the left fender of the mining machine. When taking cuts deeper than 20 to 25 ft with a scrubber-equipped machine, the machine's discharge is in by the mouth of the blowing curtain, creating a concern by mine workers that a loss of air to the face could result. However, Bureau of Mines research found that the push or throw of air toward the return by the scrubber discharge jet allows good face ventilation to be maintained with extended curtain setbacks.

Jan 1, 1984

By Thomas E. Marshall, Roy H. Grau

The U.S. Bureau of Mines has developed an acoustic test for determining if a rock salt sample is from a "normal" nongassy salt face or from a gassy face where an outburst has the potential to occur. The test is based on the observation that a salt sample taken near an outburst-prone zone produces an audible popping sound when it is dissolved in water. The sound is produced when pressurized gas that is trapped in salt samples is released. In the acoustic test, the sound is electronically measured, digitized, and transmitted to a microcomputer; the output is an average decibel value that classifies the sample as "normal" or "outburst." The acoustic test procedure and equipment are described, and raw test results and data analysis are shown. Results are also shown for several salt samples that were analyzed using a laser Raman microprobe.

Jan 1, 1990

By David M. Hyman

Outbursts are sudden and violent releases of gas and coal that result from a complex function of geology, stress regime, and gas pressure and content. The Bureau of Mines has reviewed methods for prediction and mitigation of such outbursts in use worldwide, as an aid in selecting the proper techniques for use in specific mine environments. Outburst-prone coal may be distinguished from normal coal by its sorption-desorption velocity. Three types of methods used to characterize the kinetics of sorption-desorption are described; all are based on the ability of outburst-prone coal to release, through desorption, methane or carbon dioxide much more rapidly than normal coals. Other prediction methods, based on borehole samples, are also described. Various mitigation methods described and evaluated include (1) working the least stressed, less disturbed, lowest gas content seam in multiple-seam areas; (2) mine opening geometry; (3) inducer shot firing; (4) water infusion; (5) localized stress relief, using boreholes or by cutting a reliever slot in the longwall face; and (6) other gas drainage methods.

Jan 1, 1987

Improve the safety, reliability and overall effectiveness of mine stench warning systems and to provide a means of remote control stench injector operation. Approach Industrial gas odorants were analyzed for their suitability for use in mine stench warning systems. A prototype stench injector capable of precise flowrate control was designed, fabricated, and tested using the odorant chosen as having the most favorable properties. Based on the results of the field tests, a second generation injector was developed. The second generation unit features optional remote control operation, and in addition, is simpler to refill and is less expensive than the original injector. A complete second generation system, consisting of two manually operated injectors and one remote controlled injector was in-mine tested through actual mine fire drills. How It Works Ethyl mercaptan mixed with Freon is the predominant stench agent used in the U.S. underground metal and nonmetal mines. However ethyl mercaptan's toxicity,

Jan 1, 1982

Provide the U.S. mining industry with the means to measure and control exhaust emissions of diesel engines used in underground mines. Approach Diesel research is divided into four primary areas: exhaust aerosol measurement, particulate control, gaseous emission control, and chemical and biological characterizition of particulate matter. Diesel research is frequently cosponsored by industry; collaborative research ventures between industry, academia, other government agencies, and the Bureau arc common. Diesel research at the Bureau is conducted in the diesel engine research facility at the Bureau?s Twin Cities Research Center (TCRC). This facility is a state-of-the-art laboratory capable of performing emissions testing, exhaust control evaluations, and safety tests. Background Exposure of mine workers to airborne contaminants from diesel engine exhaust is potentially harmful. The National Institute for Occupational Safety and Health has recommended that whole diesel exhaust be regarded as "a potential occupational carcinogen" and that ?reductions in exposure to diesel exhaust in the workplace would reduce the risk." The U.S. Mine Safely and Health Administration (MSHA) convened an Advisory Committee on Standards and Regulations for Diesel-Powered Equipment and is beginning to implement its recommendations, which cover health, safety, and certification and approval issues surrounding the use of diesels underground. In January 1992, MSHA published an advance notice of proposed rulemaking to regulate diesel particulate matter in underground mines.

Jan 1, 1992

By John L. Reuss

A laboratory study was conducted by the Bureau of Mines to investigate the technical feasibility of decomposing hydrous magnesium chlorides by using a steam pyrohydrolysis technique. This procedure consisted of injecting steam into the atmosphere of a decomposition furnace containing samples of hydrous magnesium chloride and determining the rate of hydrolysis by measuring the rate of chloride evolution. The variables investigated were temperature, amount of water vapor in the decomposition atmosphere, and hydration stage of magnesium chloride. The application of steam was shown to accelerate both the rate and completeness of magnesium chloride decomposition reactions. For example, when magnesium chloride hexahydrate is exposed to a furnace temperature of 600' C in an air atmosphere for 20 minutes, the decomposition is 37 percent. Under identical conditions in a steam atmosphere, the decomposition is in excess of 70 percent. The magnesium oxide produced by the steam pyrohydrolysis of magnesium chloride dihydrate at 800° C contained 98 percent magnesium oxide. Based on magnesium oxide composition, this is equivalent to that of burned magnesite produced at temperatures in excess of 1,300° C. To demonstrate the quality of the product on a practical basis, metal reduction tests have shown it to be equivalent to reagent-grade magnesium oxide as a carbothermic reduction feed material.

Jan 1, 1974

By A. B. Cecala

A cooperative research effort was established between the Tilden Mining Company LC, the United Steelworkers of America, and the National Institute for Occupational Safety and Health to lower respirable dust levels in an iron ore grinding and concentrator plant. This cooperative effort involved three field studies to evaluate different techniques to lower respirable dust levels. The greatest impact on lowering respirable dust concentrations throughout this facility was achieved through ventilation changes. The most significant improvement was realized by changing the ventilation profile throughout the entire facility. The ventilation to this grinding and concentrator facility was provided by approximately 40 roof fans operating in either the intake or exhaust mode. The operation of these fans was significantly changed in an attempt to pro-vide more of a directional flow pattern throughout the facility, as well as to more closely balance the intake and exhaust air volume. This change accounted for a 31 pct reduction in respirable dust levels in the primary grinding area of the mill. Another successful modification was to improve the sealing of a reclaim tunnel to the outside and by barricading the access point from the reclaim tunnel to the concentrator plant. This minimized the dust liberated in the conveyor tunnels from traveling through the reclaim tunnel and into the plant. These two modifications illustrate the impact that improvements in ventilation can have on lowering respirable dust concentrations in iron ore processing facilities.

Aid mine operators as well as mine inspectors in making quick but sufficiently accurate measurements of the rock dust content of coal/rock dust mixtures. The Problem Past research has shown that accumulations of volatile coal dust in underground coal mines can be rendered non-explosive by dilution with chemically inert rock dust (usually limestone). Consequently, rock dusting is required by law in U.S. underground coal mines. However, mine officials and inspectors have no quick and reliable means to determine whether enough rock dust has been applied to achieve a mixture that is in compliance with the law. Even the compliance tests used by the Mine Safety and Health Administration (MSHA) are slow and involved. MSHA assures that a mine has been rock dusted adequately by collecting samples from rock dusted areas of the mine and sending the samples to a laboratory for analyses of the inert-dust content. The analyses may not be completed for more than two weeks, during which time the mine in question might be inadequately protected against coal dust explosions. To solve this problem, the Bureau of Mines devised a quick, simple and reliable device that can immediately determine the rock-dust content of a mixture of coal and rock dust.

Jan 1, 1985

By C. J. Chindgren

The Bureau of Mines investigated the technical problems involved in recovering commercial-grade vanadium products from alkaline solutions of low vanadium content. Conditions were defined for precipitating calcium vanadates from sodium vanadate solutions with calcium chloride and calcium hydroxide and for dissolving the precipitates with acid, sodium carbonate, and sodium bicarbonate to obtain vanadium-enriched solutions from which either red cake or ammonium metavanadate was recovered. Calcium vanadates with CaO:V205 mole ratios of 2, 3, and 4 were produced with recoveries of 93 to 100 percent. Optimum recovery of the low-lime variety of calcium vanadate was obtained by employing excess calcium chloride and adjusting the pH to a range of 8.0 to 8.5. High vanadium extractions were obtained in concentrated solutions by dissolving the calcium vanadate precipitates with any of the reagents tested. The resulting extracts contained 25 to 125 grams V205 per liter. Conventional procedures used to precipitate either red cake or ammonium metavanadate from the enriched solutions gave excellent vanadium recoveries.

Jan 1, 1967

By Wilbur I. Duvall

In this report, the Bureau of Mines presents a theoretical solution for the stresses and displacements in an infinite elastic plate containing a circular hole the boundary of which is loaded by applied radial stresses over four separated arcs. The problem solved is a two-dimensional approximation of the stresses and displacements developed by a large tunnel-boring machine anchored in a circular tunnel. Analysis of the solution shows that the tangential tensile stresses induced on the boundary of the circular opening can be minimized in the roof and maximized in the floor of the opening by proper spacing and loading of the four arcs.

Jan 1, 1967

By T. F. Anstett

The Bureau of Mines investigated the availability of platinum from known major deposits in market economy countries. Fifteen of these deposits contain demonstrated resources totaling 302 million troy ounces of platinum. Detailed geologic, engineering, and cost evaluations were performed on each deposit to determine its potential for platinum production. There are large amounts of demonstrated platinum potentially available from market economy deposits that were not analyzed owing to lack of adequate data or to technological limitations. These include 297 million troy ounces contained in the UG2 and Platreef of the Bushveld Complex, South Africa. This analysis indicates that about 11 0 million troy ounces (2.3 million ounces annually) of platinum are potentially available at the January 1980 producer price of $420 per troy ounce, nearly all from South Africa. An additional 85 million troy ounces occurring in Zimbabwean deposits would become available only through more than a quadrupling of that price. In order to meet projected world demand of 3.5 million troy ounces in 1990, platinum price may have to increase. Only one domestic deposit, the Salmon River in Alaska, is capable of producing platinum at $420 per troy ounce. Regardless of price, at assumed production capacities, domestic deposits could supply less than 10 percent of annual U.S. requirements.

Jan 1, 1982

By Jozef S. Stachulak

In This Chapter [Ore pass dust control Drill dust control Blasting dust control Conveyor belt dust control Transfer point and crusher dust control Roadheader dust control and How much ventilation air to use] This chapter discusses respirable dust control in underground hard-rock mines. These mines use a wide variety of extraction methods, but they have many common dust sources and dust control needs. Ore passes, drills, blasting, conveyor belts, transfer points, crushers, and load-haul-dump operations can be major sources of dust. Roadheaders, which are sometimes used in hard-rock mines, produce dust in large quantities. For the most part, dust in hard-rock mines is controlled with ventilation air, water sprays, and dust collectors. It is also important to prevent dust from getting into the air in the first place. Good dust control practices will reduce overall mine ventilation requirements. [Lack of maintenance is the main source of dust problems in hard-rock mines according to Rodgers [1974], who conducted a dust survey of hard-rock mines several decades ago. Rodgers found that spray systems had clogged sprays, dust enclosures had improperly fitted skirts, and ductwork was plugged and had leaks. Today’s mines have better maintenance programs (we think), but when dust levels are high, maintenance is still the first topic to address.] The Mining Association of Canada [MAC 1980] and Knight [1980] provide good general information about hard-rock dust control. For conveyor belt dust control, Goldbeck and Marti [1996] and Swinderman et al. [1997] are valuable sources of information.

Jan 6, 2003

By Robert L. Chufo

The paper, "An Electromagnetic Roof and Rib Thickness Sensor" presented at The 12th WVU International Mining Electrotechnology Conference in 1992, presented the results of roof coal thickness measurements in underground mines and rib coal thickness measurements in highwall mines. The microwave sensor described uses a unique spatial modulation scheme created by antenna motion, along with frequency domain signal processing, to solve the problem of media, target, and antenna dispersion. This paper further describes the advantages of the unique frequency domain signal processing technology chosen by the U.S. Bureau of Mines in extending previously reported one-dimensional thickness measurement technology to the generation of a full three-dimensional underground image of the underground environment. The electromagnetic signature of a media, whether it is coal or other geological material, is its permeability and permittivity and the effect on the velocity and amplitude of an electromagnetic wave as it passes through. High-quality imaging cannot occur without the identification of, and correction for, the permittivity and permeability of each layer of a multilayer geological deposit. Clutter, or any signal that can interfere with target discrimination, usually comes from objects in the field of view for which there is no design control. These are nuisance targets with possibly very high contrasts compared to the real target. The only proven tool to reduce clutter is to increase spatial, spectral, and polarization diversity. This paper will describe some techniques being used by the U.S. Bureau of Mines to increase the information content of both single-dimensional and three-dimensional imaging systems through the identification of media distortion mechanisms made possible by the use of spatial/spectral sensor technology. These techniques will permit high quality imaging in an environment where the data is corrupted by dispersion and clutter.

By Earl C. Lane

This is the second of a series of reports on a survey of petroleum products manufactured on the Pacific Coast from California crude oils. California crudes differ in many characteristics from the petroleum produced in other parts of the United States, and the claim has been made that some of the present federal Specifications for petroleum products tend to discriminate against California products. The purposes of the present survey are to determine what particular specification requirements California petroleum products characteristically fail to meet, how widely the products deviate from these requirements, and if possible to show whether the fault lies with the specifications or the products, or along what 'lines investigation to determine the question should proceed. The first report* of the series gave the physical and chemical properties of gasoline and mineral spirits made from California crudes. The present report deals with lubricating oils. Sixty-one samples of lubricating stocks and finished commercial products were generously donated by four of the large refining companies of California. Fifteen samples of automobile lubricating oils, made in California from California crudes, were purchased in the open market. Nine samples of lubricating oils mode from Gulf Coast crude were contributed for comparison by a company in Texas. The refining companies have continued the helpful and cordial cooperation shown by them in connection with the earlier work of the survey.

Jan 1, 1923

By Maria I. De Rosa

Table 37 and figure 13 show the number of fires and fire injuries for surface stone mines by state during 1990-2001. Table 37 also shows the injury risk rates, employees' working hours, and lost workdays. In all, 96 fires occurred in 31 states and 1 fire occurred in Puerto Rico. Sixty-eight of the fires caused 67 injuries and 1 fatality (including 6 fires and 5 injuries involving contractors). The yearly average was eight fires and 5.6 injuries. The Ewhr value was 689 x 106 hr (Irr = 0.02), and the LWD value was 7,399. Indiana had the most fires (eight fires and four injuries), followed by Georgia (seven fires and seven injuries) and Pennsylvania (seven fires and five injuries). Of these states, Georgia had the highest injury risk rate value (Irr = 0.058). Table 38, partly illustrated in figure 14, shows the number of fires, fire injuries, fire fatalities, risk rates, employees' working hours, and lost workdays by time period. The number of fires and fire injuries show an increase during the second period followed by a decrease during most of the remaining periods. Employees' working hours increased during most of the periods. The In values follow patterns similar to those shown by the injury values. Tables 39-44 show the number of fires by ignition source, method of detection and suppression, equipment involved, location, and burning material by time period. Figure 15 shows the major variables related to fires for 1990-2001. Table 45 shows the number of fire injuries per number of fires causing injuries and total fires by year, ignition source, equipment involved, and location.

Jan 1, 2004

By J. J. Cummins

Green River oil shale previously extracted by benzene was heated at 150°, 200°, 250°, 300°, and 350° C for 0.5 to 360 days to determine the rate at which kerogen degrades to thermal products, the types of thermal products formed, and the effect of prolonged low-temperature heating (preheating) upon subsequent assay yields. Thermal decomposition of kerogen at 150° to 350° C is treated as a first-order reaction. The specific reaction rate for kerogen decomposition increases from 2.2 X 10-4 per day at 150° C to 2.0 X 10-1 per day at 350° C. The calculated kerogen activation energy is 19 kcal. Variations in the rate of formation of individual type components of the pyrolytic products were found. Carbon balances show an increase in the amount of kerogen converted to bitumen and oil (from assay of preheated oil shale) as the temperature of preheating increased from 150° to 350° C. Total product from shale preheated at temperatures of 150° and 200° C gave less than 100 percent of Fischer assay yields while the total products from shale preheated at temperatures of 250° to 350° C gave greater than 100 percent of Fischer assay yields.

Jan 1, 1972

By Leonard J. Prosser, Joseph Cervik, John H. Perry

The Bureau of Mines has developed several techniques for draining methane from coalbeds in advance of mining. Drilling long horizontal holes from an underground location is one such technique, which was successfully demonstrated in the Pittsburgh and Sunnyside Coalbeds. The same technique has now been applied in the Mary Lee Coalbed at Jim Walter Resources, Inc. 's No. 4 Mine, Brookwood, Ala. , where two holes were drilled horizontally--one to a depth of 1,010 feet (308 m) and the other to 540 feet (165 m). The 1,010-foot (3083) hole proved successful in degasifying a portion of the Mary Lee Coalbed. The hole drained methane for 1 year, during which time the initial gas flow of 200,000 ft3/d (5,663 m3/d) declined to 65,000 ft3/d (1,840 m3/d). Total gas production was 40 x lo6 ft3 (1.1 x lo6 m3 ). The gas was of commercial quality, with 98 pct methane and a heat rating of 990 Btu/ft (36.89 Mj/m3). The methane emissions from the faces of the mine section advancing into the degasified zone were reduced by 60 pct. The 540-foot (165-m) hole was terminated prematurely when it became impossible to maintain an open hole. Because of caving, very little gas was drained through this hole.

Jan 1, 1982

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

7. Development of Acoustic Seal Checking System The acoustic approach was shown in Section 4 of this report to be the most promising concept for checking the seals. This section describes the development of this concept into a working hardware system to be used later in the field test program. This development effort included: (1) Theoretical analysis of the acoustic behavior in the mine using acoustic modeling- techniques. (2) Experimental determination of acoustic patterns in mine passages. (3) Refinement of the theoretical model. (4) Verification of final theoretical predictions in the quarter-scale laboratory model of a mine passage and seal. (5) Development of system specifications. (6) Development of the Acoustic Prototype Seal Checking System. 7. 1 Analysis of the Acoustic Seal Checker Concept The acoustic seal checker concept is based on a model which combines corridor acoustics and hole transmission theory. The idealized model for the mine sealing application is shown schematically in Figure 66. A high intensity acoustic- source is located in a corridor at a, position adjacent to the location to be sealed. The acoustic signal transmitted through the seal is monitored by a microphone pick-up placed on the opposite side.

Jan 1, 1973

By H. M. Lawrence

"In the land-pebble district of Florida a lively interest in the possibilities of obtaining increased recoveries of phosphate rock is evident. Research in several directions is being carried on by companies operating in the district to increase the yields obtained by the washing plants. The Bureau of Mines is cooperating with this research program to promote more efficient plant practice and to avoid unnecessary depletion of mineral resources.Washing practice, as carried on in the district at present for the recover of phosphate rock from the crude ores or matrix, is not a complicated process. Flow sheets of the several companies are similar, although the equipment varies with the preferences of the individual operators. For disintegrating the matrix log washers are favored, although revolving drums equipped with flights to break up lumps of clay are also used. Fine sand is removed by screening. Vibrating screens have become well established in the district, although stationary flat screens and trammels are also employed.The writer acknowledges with appreciation the cooperation of the phosphate companies in the land-pebble district; suggestions and criticism by Will. H. Coghill, supervising engineer, Ore Dressing Section of the Bureau of Mines; and the laboratory assistance of J. O. Davie, J. W. Pamplin, and E. Roca, cooperative fellows of the University of Alabama.Losses in the Finer SizesOf the phosphate that is not recovered by present washing methods the greater portion is in the finer sizes. In these sizes the phosphate grains are accompanied by grains of sand - largely quartz - of the same size, and recovery of these phosphate grains as a commercial product is not possible by simple washing methods. Phosphate recoveries approaching complete extraction can only be effecte by applying metallurgical processes, either mechanical or chemical. As yet, most of these processes have not advanced much beyond the laboratory or perhaps the pilot-plant stage. Such processes may have some application to the beneficiation of phosphatic ores or washer rejects, but a discussion of them is not within the scope of this paper."

Apr 1, 1929

By D. Harrington, B. W. Dyer

"One of the products of the activities of the United States Chemical Warfare Service is a simple device and method for nearly instantaneous determination of small quantities of carbon monoxide in air. Since the war, this device has been diverted to commercial uses, and is now being marketed in connection with rapid determination of the comparatively small but dangerous quantities of CO, which may be found in garages, in sewers, about blast furnaces, etc. Also, it probably has a definite field of use in both coal and metal mines in connection with fires and explosions, as well as in confined places after firing of explosives) the latter applica-tion being of especial importance in metal mining.The device as marketed is readily portable, being small and light enough to carry in a coat pocket of medium size. In operation, a sample of the air mixture is drawn into a small rubber bulb, then forced through a small glass tube filled with certain chemicals upon which CO has the effect of changing the original color from gray or white to shades of green, the deepness of the green determining the percentage of CO in the air. A color scale is attached for purpose of comparison and determination of CO percentage. Only a few minutes are consumed in obtaining the result, all work being done on the ground.The exact effect of minute quantities (up to 1/10 of 1 percent) of CO on the human system is somewhat uncertain, and much research has been and is being done to obtain definite data on this point. It is, however, definitely known that in air containing more than 1/10 of 1 percent CO men doing hard work are quickly and seriously affected. As the gas is tasteless, colorless and odorless, methods of determining the presence of both small and large quantities have been of much importance. Technical Paper 11 of the U. S. Bureau of Mines gives much data as to effect of CO on mice and canaries. It was found that mice show very little distress until the CO content is about 0.20 percent, but quickly succumb when that percentage is exceeded; canaries are somewhat more susceptible; they quickly show distress in as little as 0.15 percent 00, and soon collapse when that percentage is exceeded."

Jan 1, 1921