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By M. M. Tilman

The Bureau of Mines conducted research to determine whether it is possible to substantially improve the fatigue resistance of lead sheet by means of surface coatings. Five types of coatings were applied to unalloyed chemical lead sheet. Flexural tests revealed that the best fatigue resistance was obtained with coatings of vacuum grease. Vacuum-grease coatings on unalloyed lead sheet resulted in fatigue resistance at least as good as that of the fatigue-resistant alloy Pb-0.04 Ca. Coated lead sheet was also tested in short-time tensile tests and in tensile creep tests. Tensile and yield strengths were increased by several of the coatings with only moderate loss of ductility. Creep resistance was also improved in varying degrees by most of the coatings. The Bureau also conducted research on the effectiveness of noise barriers by using sheet lead in combination with other materials. Noise barriers consisting of continuous-cast sheet lead with gypsum board were found to be effective and relatively inexpensive barriers.

Jan 1, 1978

By Edward L. McHugh

Mineral resources in the Silver Creek study area of the Nez Perce National Forest. Idaho, were investigated during the summer Of 1989. The study area includes the 36,100-acre Silver Creek-Pilot Knob RARE II area (No. 1-849) on the north side of the South Fork Clearwater River, about 11 miles west of Elk City, 10. Mines in and near the study area in the Tenmile and Newsome mining districts produced about 100.000 02 of gold, mostly from placers. Gold production had an historic value estimated at 52 million, equivalent to nearly $40 million at today's prices. Lode mines produced about 19,000 oz of gold, along with smaller amounts of silver, copper, lead, and zinc. Of 34 mines and prospects examined, ten lode properties are considered to be significant by virtue of their past development or production and the presence of possibly ore-grade mineralization. There are no identified mineral resources in the study area; however, samples that contained gold and anomalous arsenic delineate a three-mile-long area from the Sentinel mine, north to the Blue Quartz prospect where exploration might disclose resources. One mining company is conducting geophysical studies and drilling within the delineated area. In addition, six placer sites may contain enough gold to be of possible interest for future exploration and development.

Jan 1, 1991

By Ramie H. Thompson

1.1 BACKGROUND In many underground coal mining operations the use of electromagnetic field equipment, particularly communication systems, not only increases the overall efficiency of the mining operation but can be directly linked with mine safety considerations. The use of electromagnetic field producing equipment in underground coal mining operations can only be expected to grow. Several new communication systems have already been proposed. In addition, high-frequency producing equipments for many diverse uses in mining operations are under study. The use of these equipment in underground mining operations is hampered by the possibility of their electromagnetic fields interacting with the electric blasting cap operations commonly carried out in the mines. Such interactions can have at least two results bearing directly on mine safety: o premature initiation of the cap, either in its normal shot location or during hookup or transportation; o dudding of the cap so that normal firing operations do not cause irritation; thereby leaving unexploded high explosives after normal firing. Since the consequences of a premature initiation could, particularly in coal mines operations, result in catastrophe involving human life, the overall approach to prediction of possible hazard must be, as far as possible, of a "worst case" nature. The general problem of predicting possible RF hazards for any electroexplosive device (EED) is best treated by reference to Appendix A of

Jan 9, 1983

By A. Sainato, S. J. Kravits, G. L. Finfinger

This Bureau of Mines report describes and compares the procedures, capital investments, and operating costs of rotary and in-hole motor drilling techniques used to drain methane gas from the Pittsburgh Coal- bed in an underground mine located in southwestern Pennsylvania. A timestudy was conducted during the drilling of each of two boreholes, and the data were collated to serve as a base for comparing drilling procedures and operating costs. Findings indicate that drilling with an in-hole motor offers four advantages over rotary drilling; namely, an increase in drilling productivity, fewer worker-hours required, ease of maintaining vertical and horizontal bit trajectory, and less expensive drilling cost per foot of borehole.

Jan 1, 1985

By J. J. Demeter

Anthracite from the four producing regions in Pennsylvania was both ashed in the laboratory and burned on a chain-grate stoker to determine the sulfur-retention properties of its ash. The retention of sulfur in laboratory-prepared anthracite ash was shown to be related to ashing temperature and to the amounts of sulfur and calcium present in the coal. At the usual laboratory ashing temperature of 750° C sulfur retention ranged from 0.8 to 13.2 percent of the total coal sulfur. Sulfur retention in the ash was negligible, o to 0.3 percent, at 1,200° C, which is the thermal decomposition temperature of calcium sulfate; thus calcium sulfate does not form and cannot serve as a sulfur-retaining agent. In several tests the anthracite was mixed with 6 or 10 percent dolomite prior to firing in the chain-grate stoker. The dolomite did not improve sulfur retention owing to the high temperature in the fuel bed. Sulfur retention was, however, related to the unburned carbon in the ash. The relationship of the percentage of original coal sulfur retained in the ash (Y) to the percentage of the original carbon in the coal remaining in the ash (X) is expressed by Y = -0.579 + 0.914X. The percentage of sulfur retained is almost directly proportionate to the percentage of original coal carbon in the ash.

Jan 1, 1968

By James W. Ballard

The facts are generally accepted that an atmosphere containing large quantities of any dust is objectionable to breathe and that some dusts are more dangerous than others. Therefore, knowledge of the composition of dusts is important in evaluating the hazard entailed on exposure. At present, free silica, of which quartz is the most abundant form, is considered one of the most significant dusts, from the standpoint of pneumoconiosis, and one State5/ has established permissible limits of air dustiness on the basis of the free-silica content of rock. The amount of free silica in materials used for rock dusting also has been limited.6/ Determination of free silica or quartz, therefore, is important.

Jan 1, 1940

By D. L. Pool

To increase metal recoveries and to minimize pollution by improved extraction technology, the Bureau of Mines investigated a hydrometallurgical technique to recover copper, lead, nickel, and cobalt from lead smelter mattes. The metals were converted from insoluble sulfides to soluble chlorides using a HCI-CI2-02 leaching system. Parameters studied in a 50-gallon, glass-lined reactor were the ratio of hydrochloric acid to chlorine, chlorine consumption per pound of matte, oxygen reaction pressure, and temperature. The matte material used contained, in percent, 19.7 Cu, 52 Pb, 2.9 Ni, 1.5 Fe, 0.38 Co, 0.19 As, 0.41 Zn, and 0.12 Cd. Extraction of Cu, Pb, Ni, Co, and Cd ranged from 92 to 98 pct, with concomitant extractions of Fe and As of <0.1 pct. The Cu and Pb were recovered as electrowon metals, while the Ni, Co, and Cd were recovered as mixed hydroxides.

Jan 1, 1981

By J. Shawn Peterson, David S. Yantek, Adam K. Smith

Exposure to excessive noise over time can cause permanent hearing loss. Workers in the mining industry are frequently exposed to A-weighted sound levels in excess of 90 dB. The A-weighted sound level at the roof bolter operator’s location can exceed 100 dB while drilling. The National Institute for Occupational Safety and Health (NIOSH) measured the sound pressure at the roof bolter operator’s position and utilized a phased array of microphones with beamforming software to identify noise sources on a roof bolting machine while drilling. The test data indicates the sound level at the operator’s position is dominated by the 2000 Hz through 5000 Hz one-third­octave-band sound levels. The beamforming results indicate that the drilling noise is primarily from two areas: the portion of the drill steel just below the rock and the drill steel-chuck interface. This paper will discuss the methods used to identify the primary noise sources.

By Terry S. Cory

This report covers antenna design, analysis, and development work suited for use with a wireless radio communication system operating at medium frequency. The work includes the test and evaluation of prototype vehicular antennas developed during the program.

Jan 12, 1978

By A. W. Maynard

Simple chemical spot tests for the identification of major alloying elements in aluminum-base alloys are described. The tests are suitable for use by nontechnical personnel working outside a laboratory. Tests for zinc, copper, manganese, and magnesium employ electrographic sampling methods and sample papers. Use of electrographic sampling in a test for magnesium in aluminum is made possible by using glass fiber filter paper. Differentiations between magnesium and magnesium-silicon alloys of aluminum and between aluminum-base and magnesium-base alloys are made by direct chemical solution tests. Description of a device for obtaining reliable electrographic samples is included. A sequence of testing for identification by alloy groups is given.

Jan 1, 1971

"An active list of permissible explosives was published in September 1935 as part of United States Bureau of Mines Report of Investigations 32S6, under the title ""Active List of Permissible Explosives and. Blasting Devices Approved. Prior to July 31, 1935."" This list included 154 brand names,Changes in the list that have been authorized subsequently placed 24 addi¬tional brands of permissible explosives on the active permissible list as a re¬sult of tests, changes in brand names, or transfer from the inactive list. Eight permissible explosives were transferred from the active to the inactive list. The present active permissible list contains 170 brand names. The brand names of the permissible explosives placed on the active list are as follows:Black Diamond Nu-Gel No. 4 By test.Black Diamond Special A,do.Burton 11, L. F. By change in name,Burton G, L. F. By test.Columbia B By change in name.Columbia C Do.Columbia D Do.Columbia E Do.Columbia. F Do.Columbia G Do.Columbia 1 Do.Columbia 2 D.Columbia 3 DoColumbia 4 Do.Columbia-Gel 1 Do.Columbia-Gel 2 Do.Genite 5, Do.Genite 7, Do.Genite G Do.Lump Coal C By test.Peerless No, 1 By transfer from inactivePeerless No. 8, L. F. Do.Tri-State Special No. 1 Do.Unilite No. 2 Do."

Dec 1, 1936

By Steven J. Page

The increasing concern for dust control in metal and nonmetal mining prompted the Bureau of Mines to investigate the dust suppression technique of applying foam to face drilling and crushing operations in a gypsum mine. Previous attempts to achieve effective dust control on face drills using other techniques, such as dry collection and boom-mounted external water sprays, have not been successful. The largest problem encountered when using these techniques has been the lack of sustained effective dust capture at the face. Results for two faces studied show that injection of the foam through the drill steel provided an average dust reduction of 95 pct. However, the use of foam on the crusher provided no dust reduction at the operator&apos;s position (because of good local ventilation) and a 27-pct average dust reduction for two feeders at a location midway between the operator&apos;s position and the crusher. The conclusions obtained from this study are that (1) foam can be an extremely effective dust control technique when used on localized dust sources such as dust generated within a blasthole during drilling, and (2) foam is only marginally effective as a dust control technique when used on nonlocalized dust sources such as dust generated during the feeder-and-crusher operation.

Jan 1, 1981

By Jürgen F. Brune, R. Karl Zipf, Michael J. Sapko

Seals are barriers constructed in underground coal mines throughout the United States to isolate abandoned mining panels or groups of panels from the active workings. Historically, mining regulations required seals to withstand a 140-kPa (20-psig) explosion pressure. However, the Mine Improvement and New Emergency Response Act (“MINER Act”) requires the Mine Safety and Health Administration (MSHA) to increase this design standard by the end of 2007. This report provides a sound scientific and engineering justification to recommend a three-tiered explosion pressure design criterion for new seals in coal mines in response to the MINER Act. Much of the information contained in this report also applies to existing seals. Engineers from the National Institute for Occupational Safety and Health (NIOSH) examined seal design criteria and practices used in the United States, Europe, and Australia and then classified seals into their various applications. Next, the engineers considered various kinds of explosive atmospheres that can accumulate within sealed areas and used thermodynamic calculations and simple gas explosion models to estimate worst-case explosion pressures that could impact seals. Three design pressure-time curves were developed for the dynamic structural analysis of new seals under the conditions in which those seals may be used: unmonitored seals where there is a possibility of methane-air detonation or high-pressure nonreactive shock waves and their reflections behind the seal; unmonitored seals with little likelihood of detonation or high-pressure nonreactive shock waves and their reflections; and monitored seals where the amount of potentially explosive methane-air is strictly limited and controlled. Figure 1 is a simple flowchart that illustrates the key decisions in choosing between the monitored or unmonitored seal design approaches and the three design pressure-time curves. For the first condition, an unmonitored seal with an explosion run-up length of more than 50 m (165 ft), the possibility of detonation or high-pressure nonreactive shock waves and their reflections exists. The recommended design pressure-time curve rises to 4.4 MPa (640 psig) and then falls to the 800-kPa (120-psig) constant volume (CV) explosion overpressure. For unmonitored seals with an explosion run-up length of less than 50 m (165 ft), the possibility of detonation or high-pressure nonreactive shock waves and their reflections is less likely. A less severe design pressure-time curve that simply rises to the 800-kPa (120-psig) CV explosion overpressure may be employed. For monitored seals, engineers can use a 345-kPa (50-psig) design pressure-time curve if monitoring can ensure that (1) the maximum length of explosive mix behind a seal does not exceed 5 m (16 ft) and (2) the volume of explosive mix does not exceed 40% of the total sealed volume. Use of this 345-kPa (50-psig) design pressure-time curve requires monitoring and active management of the sealed area atmosphere. These design pressure-time curves apply to new seal design and construction.

Jan 7, 2007

By D. S. Burgess

The characteristics of gas-phase detonations were observed in 20 instrumented firings within earthen tunnels, in 100 such detonations in a 24-in-diam by l63-ft-long steel pipe, and in about 200 smaller scale firings. Most of the fuels studied were representative hydrocarbons--acetylene, propane, gasoline, and a roughly equimolar mixture of methylacetylene, propadiene, and propane. In a pipe with two closed ends, the detonable limits were demonstrated to be very nearly the same as reported limits of flammability. The side-on impulses (pressures integrated over 200-msec intervals) were shown to be the same function of concentration regardless of whether deflagration or detonation had occurred. In a pipe with only the initiation end closed, the impulses of all fuel-air systems tended toward the same level when averaged over comparable ranges of fuel concentration; the lower pressures with saturated hydrocarbons were nearly compensated by longer durations of pressure transient. In all fuel-air systems, unexpectedly high impulses were obtained with slightly lean mixtures. In earthen confining structures, the impulse, of the explosion was efficiently converted into momentum of the failing wall. In the configurations studied, an earth velocity of about 20 fps was critical to overcome the soil&apos;s resistance to shear. The destructive effect was determined by gas pressure rather than by total energy release. The assignment of a "TNT equivalent" to an explosive gas mixture is discussed in terms of the confinement of the mixture.

Jan 1, 1968

By L. Garner McDonald

The U.S. Bureau of Mines tangentially impacted potential coal-cutter bit shank materials against sandstone to investigate the potential of the materials to ignite natural gas by a friction-generated hot streak. The shank material samples were mounted in a 24-in, 550-lb flywheel, which was rotated at surface speeds of 400 to 900 sfpm. The sandstone was advanced toward the rotating flywheel at feed rates of 1 mil per impact. The atmosphere mixture was 7 vol pet natural gas in air. Three grades of polycarbonate resin, an ultra-high-molecular weight polyethylene, and a zinc alloy (ZA27) were among the potential materials. None of these materials caused ignition of the methane at any of the three test speeds (400, 600, and 900 sfpm), but the above materials do not have sufficient strength to hold a carbide tip during coal cutting. Of the materials having sufficient strength to hold a carbide tip, three nickel-based alloys proved less likely to cause a natural gas ignition than did iron-based alloys such as 4340 (a commonly used shank material for coal cutters).

Jan 1, 1992

By D. R. Tesarik, R. W. McKibbin

Material properties affecting slope stability were measured in a large 50-year-old, partially consolidated rockdump located in an active open-pit mine. Field tests included single-ring infiltration and density. In addition, a nuclear depth-moisture gauge was used to measure water content in six stainless-steel-cased drill holes on the crest and an upper bench of the rock dump. Precipitation, evaporation, wind speed and direction, and temperature data were collected at a weather station installed on the dump’s crest. Laboratory tests included particle-size distribution, specific gravity, Atterberg limits, and water content. By measuring material properties of a rock dump presumed to be stable, the safety of miners working on or at the toe of old rock dumps constructed of similar material and located in a similar climate can be assessed.

Jan 1, 1999

By G. W. Eiger

Bureau of Mines laboratory tests show that ilmenite concentrates with titanium dioxide contents as low as 33 wt--pct can be beneficiated to produce a crystalline substitute for natural rutile suitable for direct chlorination. The synthesized product prepared by a three-step procedure was comparable with natural rutile in titanium content. Reduction smelting of ilmenite removes iron as a pig iron byproduct, and the remaining slag phase is greatly enriched in titanium. Oxidation of the slag in the presence of phosphorus¬bearing slag additive converts the titanium-bearing phases to discrete rutile crystals and a glass phase containing most of the associated impurities. Rutile is separated from the glassy impurities by attrition scrubbing ground slag in dilute phosphoric or sulfuric acid solutions. Tests made in a laboratory fluid-bed reactor show that synthetic rutile responds to chlorination at the same rate as natural rutile and that more than 95 pct of the titanium contained in the feedstock was extracted as titanium tetrachloride.

Jan 1, 1974

By Edward L. McHugh, Jami M. Girard

While less than 1% of reported accidents are associated with slope stability problems, slope failures were responsible for about 15% of all U.S. surface mine fatalities between 1995 and 2001. Small rockfalls, which may involve hand-sized rocks weighing only a few kilograms, can cause fatal injuries to workers away from the protection of large machinery. Massive highwall failures containing a million cubic meters of material or more can be fatal even for heavy equipment operators. As part of an ongoing study at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health, several remote-sensing technologies are being evaluated as tools to monitor slopes for hazards and to assess slope stability. Field tests of a hyper spectral imager were conducted to assess its value for improving geologic maps of potentially unstable alteration zones on mine slopes. An interferometric radar device capable of detecting very small displacements on slopes awaits final assembly and field testing. Computerized monitoring methods using images from digital and video cameras are being assessed for application to mine slope surveillance. These and other techniques will eventually provide new tools to augment current methods for monitoring ground control hazards in mines.

By M. M. Fine

A satisfactory mean: of beneficiating a Brazilian phosphate rock was developed in a mineral-dressing-research study by the Bureau of Mines. High-grade concentrates well ever the specified minimum grade of 70 percent tricalcium phosphate, were produced, with goad recoveries by agglomerate tabling and flotation. A lower gads but usable secondary product was recovered by sedimentation of the minus-200-mesh fraction of the ore. The ore wan representative of an extensive deposit recently discovered near Recife in the State of Pernambuco, Brazil, which will be exploited in a plant planned to eventually produce at the rate of 500,000 tons of concentrate annually. Although Brazil has been reported to Lave a substantial reserve of phosphate rock,3/ the country has never been more than a small producer of this commodity. From 1945 to 1950 the highest production of phosphate rock attained in Brazil amounted to 10,421 tons. Production in 1949, the most recent year for which figures are available, was 4,553 tons.4/

Jan 1, 1954

By Curtis H. Elder

In studies conducted by the Bureau of Mines, two test areas were hydraulically stimulated and exposed by mining: One in the Pittsburgh coalbed at the Vesta No. 5 mine, Washington County, Pa.; and one in the Illinois No. 6 coalbed at the Inland mine, Jefferson County, Ill. Induced fractures were contained totally within the coalbed with no adverse effect on the stability of associated rock strata. Induced fractures were vertical and were propagated normal to the direction of least residual tectonic stress. Gas production was increased fivefold to twentyfold by hydraulic stimulation.

Jan 1, 1977