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To permit better cap lamp positioning for users of dust helmets. Approach The present design of the dust helmet prevents use of the miner's cap lamp when the front shield is raised, When the shield is raised I the cap lamp is directed at the mine roof or back, making the lamp useless in the event the miner needs to wear his self-rescuer. A flip bracket was designed by the Bureau of Mines to correct this situation. How It Works The safety hat is modified by the addition of lamp clips, a bracket and a hinge on the cap lamp and face shield. Two clips hold the lamp cord firmly to the helmet. When the safety hat shield is raised, compressive force from the lamp cord causes the cap lamp hinge to swing open about 90%, allowing the lamp

Jan 1, 1984

By D. E. Hirsch

The types of compounds present in aromatic concentrates derived from high-boiling petroleum distillates can be estimated from a gel permeation chromato-graphic (GPC) analysis by the use of tables developed from extensive GPC and mass-spectral analyses on fractions from four crude oils. For a fraction from the GPC analysis, the retention volume and the molecular weights (from mass spectrometer) suffice to indicate the types of compounds which predominate. The tables which show these qualitative analyses were developed through the use of pure compounds as well as the extensive analyses on Prudhoe Bay (Alaska), Gach Saran (Iran), Swan Hills (Canada), and Wilmington (California) crude oils. These tables provide a rapid method for determining which types of compounds are present in a GPC fraction before attempting to develop quantitative data.

Jan 1, 1974

By Kenneth C. Stewart

Eight brands (three samples of each kind) of commercially available audio-dosimeters were performance-tested. Each unit was placed in an anechoic chamber and subjected to various acoustic signals to measure its A-weighting response and overall integration accuracy. All units met the A-weighting tolerance for type II sould level meters, and six brands were within the Bureau I s overall accuracy requirements of ±2 dbA referred to input.

Jan 1, 1974

By R. L. Anderson

Mechanical cleaning of bituminous coal in the United States was begun about 1875, with plants in western Pennsylvania and Illinois. The United States Geological Survey began to record the quantity of washed bituminous coal in 1906; and the series was carried forward to 1923, except that no data were collected, for 1922. This statistical work was transferred to the Bureau of Mines in 1925, and the collection of data on mechanical cleaning was resumed in 1927. Data collected before 1927 include only the coal that was washed at the mines and do not include that cleaned by pneumatic methods at the mines and that cleaned at central washeries operated by consumers.2/ The total bituminous coal washed in 1906 was less than 10 million net tons. In 1927, the first year for which complete figures are available for all types of mechanical cleaning, 28 million net tons of bituminous coal were cleaned in the United States.

Jan 1, 1951

By Charles C. Boley

The Bureau of Mines dried and carbonized two wood wastes, one softwood (redwood) and one hardwood (oak), using continuous, vertical entrainment techniques previously developed for use with coal. It was demonstrated that these techniques are readily applicable to wood waste and that appreciable changes in the yields of carbonization products can be obtained by varying operating conditions. A limited amount of experimental work was done on briquetting the char-coals. Firm briquets were formed with oak charcoal, although greater quantities of starch binder than used commercially for kiln-produced charcoal were required. Redwood charcoal did not briquet successfully under the test conditions employed.

Jan 1, 1969

By C. E. Jordan

The Bureau of Mines conducted laboratory studies on methods to increase the recovery of brine from slime produced by operating potash plants. The slime was comprised of 80 percent brine saturated with KCl and NaCl, and 20 percent solids. A variety of settling techniques, filtration methods, continuous centrifugation, and novel processing techniques were investigated. Vacuum filtration recovered 6S percent of the brine at 47 gallons of brine per square foot per day. Pressure filtration, on the other hand, recovered 74 percent of the brine at 40.9 gallons of brine per square foot per day. Centrifugation in a 6-inch-diameter continuous decanter-type separator resulted in 42 percent recovery of the brine at a treatment rate of 542 gallons of brine per day. Vertical drains proved to be the most promising novel debrining technique investigated. With this method, 45 percent of the brine was recovered in 3 days.

Jan 1, 1977

To develop a quick, safe, and effective method that allows workers at mineral processing operations to clean their dust-soiled clothing periodically throughout the workday. Background Reducing workers' respirable dust exposure to silica and other harmful dusts and contaminants is an ongoing goal in the U.S. mining industry. One area of known worker exposure is from contaminated work clothes. A U.S. Bureau of Mines report documented a number of cases where a tenfold increase in a worker's dust exposure was measured from contaminated work clothes. In these cases, the dust emitted from clothing caused the worker's dust exposure to exceed the permissible exposure limit in less than 2 hours. The most effective way to eliminate this dust source is to have workers clean or change their work clothes. There are two federal regulations that impact the clothes-cleaning process. The first states that at no time shall compressed air be directed toward a person, but that when compressed air is used, then all necessary precautions shall be taken to protect persons from injury. The second regulation states that compressed air should only be used for cleaning purposes when it is less than 30 psi and used along with personal protective equipment. For the mining industry, by default, the only approved method to perform clothes cleaning is to have workers vacuum their clothes using a HEPA filter system. This is very difficult and time-consuming and, in most instances, not very effective. Most workers would prefer to use a single compressed air hose to blow dust from their work clothes. However, not only is this method prohibited by law, it usually creates a significant dust cloud in the work environment and contaminates coworkers.

May 1, 2005

By C. C. Shale

A semicommercia1, high-temperature electrostatic precipitator and adjunct equipment are described, and operating characteristics at 1,470° F and 80 psig are presented for both positive and negative polarity. Removal efficiency for negative corona waS about 91 to 96 percent while that for positive corona was only about 75 to 77 percent. Results are compared with those from bench-scale investigations, and equipment limitations are discussed. Theoretical aspects of the precipitation process are related to the operating characteristics.

Jan 1, 1969

By Isaac A. Zlochower, Kenneth L. Cashdollar

The Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health conducted a study of the explosibility of various metals and other elemental dusts dispersed in air, with a focus on the experimental explosion temperatures. The data are useful for understanding the basics of dust cloud combustion, as well as for evaluating the explosion hazards in the minerals and metals processing industries. The dusts studied included boron, carbon, magnesium, aluminum, silicon, sulfur, titanium, chromium, iron, nickel, copper, zinc, niobium, molybdenum, tin, hafhium, tantalum, tungsten, and lead. The dusts were chosen to cover a wide range of physical properties - from the more volatile materials such as magnesium, aluminum, sulfur, and zinc to the highly "refractory" (very low volatility) elements such as carbon, niobium, molybdenum, tantalum, and tungsten. These flammability studies were conducted in a 20-L chamber, using strong pyrotechc ignitors. The experimental data obtained included the minimum explosible concentrations, maximum explosion pressures, and maximum explosion temperatures. A unique multiwavelength infrared pyrometer was used to measure the temperatures. For the elemental dusts studied, all ignited and burned as air-dispersed dust clouds except for nickel, copper, molybdenum, and lead. The measured maximum explosion temperatures ranged from -1 550 K for tin and tungsten powders to -2800 K for aluminum, magnesium, and titanium powders. The measured temperatures are compared to the calculated, adiabatic flame temperatures. In general, the dusts whose experimental temperatures were closer to the adiabatic values were those with the finer particle sizes, those that were more easily vaporized, and/or those that were intrinsically more reactive.

By Donald P. Tuchman

The U.S. Bureau of Mimes is investigating Fourier transform infrared (FTIR) spectroscopy for on- filter quartz analysis of respirable dust. A custom accessory is described for full-face examination of filters utilizing a large-diameter infrared (IR) beam. The accessory positions samples to match diameters with that of the diverging analytical beam. Sample absorbance is then measured. With nonuniform deposition of dust on collection filters being a major issue for such analyses, this approach is the most direct way to accomplish sample area averaging. The approach is unconventional since it utilizes large-beam geometries instead of the usually desired minimized beam dimensions. The issues and problems involved in the analysis of quartz on a filter matrix are discussed. Absorption bands chosen, light-scattering effects, curved baselines, random noise, interference fringes, and possible solutions to technical difficulties are the topics covered. The more significant findings include a 20-pg detection limit for quartz when the custom accessory is used and minimal occurrence of light-scattering effects at low wavenumbers. The custom accessory performance was satisfactory and merits further work. With continued research, an on-filter method for quartz analysis of respirable dusts seems achievable.

Jan 1, 1992

Provide an improved, rugged, reliable, cost-effective automatic fire protection for mine haulage trucks. Approach Systems that automatically sense and extinguish fires on haulage trucks were designed, built, and in-mine tested. How It Works Temperature sensors mounted above the engine of the truck detect the heat from a fire while it is still small and controllable. A cab-mounted control panel warns the operator of the fire emergency and then automatically triggers the discharge of 60 pounds of multipurpose dry chemical extinguishing agent (from storage tanks through hoses and nozzles) into the engine compartment. If desired, the control panel can be field-adjusted by changing one resistor to delay the discharge for up to 60 seconds to allow time for the operator to stop the truck and shut down the engine. The system can be assembled with either pressurized storage tanks, or a combination of non-pressurized storage tanks plus separate pressure cartridges. This pressure source option is one of the improvements of this system over the earlier systems described in Technology News No. 11. Other improvements are a simplified control circuit and an improved sensor.

Jan 1, 1980

By D. A. Wilson

A process was developed on a laboratory scale in which a solid waste byproduct from refining of secondary lead was converted into three valuable products. Roasted lead blast furnace matte was leached with water to recover copper. This was followed by brine leaching to recover lead. Residues were finally smelted to yield pig iron. Copper was precipitated as cement copper and the lead product obtained was a mixture of pure 3PbO.PbC12.xH20 and Pb(OH)C1. Copper recovery was 89 percent and lead recovery was 96 percent.

Jan 1, 1967

By J. R. Allsup

The Bureau of Mines studied the characteristics of simulated coal gas as an automotive fuel in two multicylinder vehicles in a standard and high-compression-ratio engine configuration. While using simulated coal gas fuel, increasing the engine compression ratio improved the fuel economy and vehicle performance but increased hydrocarbon emissions by 40 pct. photochemical reactivity of exhaust hydrocarbons was found to be extremely low using the coal gas fuel. An oxidizing catalyst used with the simulated coal gas fuel eliminated all but trace amounts of carbon monoxide and reactive hydrocarbons in the exhaust. Spark gap geometry and firing voltage were varied and, within the range tested, had little effect on vehicle performance and emissions using simulated coal gas fuel.

Jan 1, 1975

By Dennis Dolinar, Christopher Mark, Gregory M. Molinda

In 1999, 2,087 unplanned roof falls were reported from 841 mines. Nearly 55% of all mines reported at least one roof fall, and nearly 17% of the mines reported five or more falls. In order to investigate the variables that contribute to roof falls, the National Institute for Occupational Safety and Health (NIOSH) compiled a national database of roof performance from 37 coal mines. Geotechnical factors and their effect on roof fall rates were compiled from over 1,500 miles of drivage. The factor that is the best predictor of roof fall rate is the Coal Mine Roof Rating (CMRR). For a low CMRR (#30), almost all cases have high roof fall rates. Conversely, high roof fall rates are rare for strong roof rocks (CMRR $ 60). Roof fall rates were also higher in deeper mines, probably because of greater stresses. Intersections were much more likely to fall than roadways, and four-way intersections were more prone to fall than three-way intersections. In a controlled comparison of the effect of increasing bolt length on roof fall rates, it was found that longer bolts reduced the roof fall rates in 11 of 13 cases. A relationship between the roof fall rate, the intersection span, and the CMRR was also found. Finally, a systematic method for tracking roof performance and geotechnical variables was demonstrated.

Jan 10, 2000

By James H. Russell

Several solid sorbents were compared for their effectiveness in removing sulfur dioxide from flue gases. The materials were tested for the rate of sorption and capacity at about 300° C, and rate of regeneration around 700° C in thin beds and in 4-inch-diameter fluidized beds. Rates of material loss were also estimated. The sorbents tested included three samples of alkalized alumina, two samples of sodium carbonate-impregnated alumina, and one proprietary sample of porous silica impregnated with copper and iron compounds. The results showed that all the alkalized aluminas had good sorption capacities and rates, required high temperature regeneration, and suffered excessive material loss; the sodium carbonate-impregnated aluminas (1) had high sorption rates but barely adequate capacities, (2) required high temperature regeneration, and (3) suffered excessive material losses; and the copper-iron impregnated silica suffered only slight material loss and could be regenerated at a relatively low temperature, but the sorption rate and capacity were too small. None of the sorbents met all the arbitrary performance criteria that follow: sorption rate constant of 1 min-1, sorption capacity of 0.1 g sulfur per g sorbent, regeneration rate constant of about 0.075 min-1 at a reasonable temperature, less than 0.07 pct per hour material loss during operation, and a chemical life of 500 cycles.

Jan 1, 1971

Provide respiratory protection and a clean work environment for stationary or semimobile workers at minerals processing plants. Approach An Overhead Air Supply Island (OASIS) was developed which filters, conditions, and evenly disperses an envelope of clean air over a worker's head, thereby insuring reduced dust levels and a clean work environment. How It Works The concept for the OASIS derives from an earlier Bureau development of a canopy air curtain for continuous mining machines (see Technology News #21). In this application, the benefits of a reliable, self-contained, self-cleaning industrial-duty air filtration and distribution system are extended to the minerals processing field. The OASIS draws dust-laden room air into a filtration system, removing the dust and delivering clean air to a specific 16-square-foot area. It consists of: ? a self-cleaning primary filter ? a heater (cooling coil optional) ? an airflow distributor and secondary filter (combined)

Jan 1, 1985

By Gregory M. Molinda

The Bureau of Mines conducted an investigation into the occurrence of outbursts of salt known to be responsible for explosions, fatalities, and damage in domal salt mines. The purpose of the investigation was to develop a basis for predicting these outbursts based on geologic and associated physical properties of salt. The investigation was conducted at the Cote Blanche salt mine in southern Louisiana. Because outbursts are the primary mode of methane emission into the mine, more than 80 outbursts, ranging in size from 1 to 50 ft in diameter have been mapped. These outbursts generally are aligned and elongate parallel to the direction of salt layering. More than 200 salt samples, both random and selected, were tested for methane content. It was found that outburst zones are well correlated with high methane content. Detailed mapping also revealed that the zones are well defined, with salt crystal size abruptly increasing upon entry into the zone. The intensity of folding and kinking of the salt layering within the outburst zone also appears to increase. An interbedded sand layer occurring throughout the mine does not appear to be a significant source of methane. However, fine-grained salt may be related to outburst occurrence.

Jan 1, 1988

By Fun-Den Wang

Finite-element structural analyses were performed to determine the stress distribution and displacements around a single rectangular coal mine opening in a multilayered rock system. The effects of changes in mechanical properties of roof and coal layers, roof layer and mine opening geometry, horizontal-to-vertical load ratio, and structural geologic features on the stress distribution about the opening were studied. Variability in the stiffness and relative thickness of the immediate roof layers can produce a considerable difference in the stress distribution about the opening as compared with that of a homogeneous material. Changes in opening width and horizontal-to-vertical load ratio have different effects on the stress distribution about the opening depending on the composition of the roof layers. In general, where a stiff layer exists in the roof at the surface of the opening, the stresses are higher in the roof and ribs around the opening. Horizontal changes in facies in the roof layers produced by structural geologic features can also greatly alter the stress distribution about the opening compared with the simple layered cases.

Jan 1, 1974

By T. E. Sterner

A laboratory investigation was conducted to determine the applicability of the thermal oil-recovery method as a means of increasing ultimate oil recovery in the Appalachian region. The primary objective was to establish self-sustained combustion in consolidated and unconsolidated sand test assemblies saturated with various amounts of Pennsylvania Grade crude oil and synthetic brine. Tests using blocks of sandstone were unsuccessful because of sealing problems and fracturing of the rock due to thermal stresses. A combustion wave of about 700° F was propagated through the sand-oil-water packs in the linear tube tests. The high air flux used resulted in high oil consumption and rapid movement of the combustion wave through the tubes. Analytical tests on the sand pack showed that sufficient fuel was deposited during the linear tube experiments for a self-sustained combustion wave.

Jan 1, 1967

By J. D. Hadden, Albert Sainato

The Bureau of Mines conducted drilling studies in the Pocahontas No. 3, the Pittsburgh, and a western coalbed to establish the gas migration characteristics for each. Gas pressures in the Pittsburgh coalbed were about 260 lb/in2 and in excess of 550 lb/in2 in the Pocahontas No. 3. Caving in drill holes prevented pressure measurements in the western coalbed. The Pittsburgh coalbed contained intersecting "clay veins" which formed gas pres- sure cells. Although these geological features hamper mining, they can be used to control the flow of methane into a mine working. Methane control techniques are proposed for the Pittsburgh and Pocahontas No. 3 coalbeds.

May 1, 1969