- 行业: Mining
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The U.S. Bureau of Mines (USBM) was the primary United States Government agency conducting scientific research and disseminating information on the extraction, processing, use, and conservation of mineral resources.
Founded on May 16, 1910, through the Organic Act (Public Law 179), USBM's missions ...
This method, as applied for the measurement of airflow in headings, can be used for determining velocities below the working range of the vane anemometer. The tracer used is normally nitrous oxide. The technique consists of releasing a quantity of tracer gas, either instantaneously or over a timed interval. The tracer then diffuses throughout the airstream until a position is reached where it is uniformly dispersed over the cross section of the airway. At such a position, samples are taken and these are put through the analyzer to determine the gas concentration.
Industry:Mining
This nonautomatic detector has the appearance of a mine official's electric hand lamp. It indicates on an illuminated scale percentages of methane from 0 to 3 in steps of 0.1. When a test for combustible gases is to be made, the projecting front piece is turned part of a revolution; this extinguishes the main light and lights up the illuminated scale. A sample of air is flushed into the detector by means of a small aspirator (or hand pump), the button switch at the side is operated, and the percentage of combustible gases, if any, is indicated on the illuminated scale.
Industry:Mining
This nonautomatic detector, or portable air analysis apparatus, can be used underground, or samples of air can be brought out of the mine in small rubber bladders and analyzed at the surface. This apparatus depends for its action on the fact that when methane is burned in air (oxygen) a definite chemical action takes place. When the resulting steam condenses to water there is a reduction in pressure and in the McLuckie detector this reduction of pressure, which is proportionate to the methane present, is indicated by the height of the liquid in one limb of the U-tube which rises up the side of the scale: the scale is graduated from 0% to 3% in steps of 0.1%.
Industry:Mining
This process consists in (1) roasting copper ore, (2) melting and obtaining a matte with 30% to 40% copper called coarse metal, (3) roasting the coarse metal, (4) melting and obtaining a matte with 60% to 70% copper called fine metal, (5) roasting the fine metal, and (6) melting and obtaining black copper.
Industry:Mining
This process consists of roasting iron ore in a reducing atmosphere, thus forming magnetic oxide of iron that is separated by crushing followed by magnetic separation. The internal structure of the kiln is so designed that the ore falls in a continuous veil through the current of reducing gases. Burners are distributed throughout the periphery of the kiln, so that roasting and reduction can be controlled in the various zones to the required temperature. Blast furnace gas for reduction passes into the center of the lower end of the kiln, while the gas and air for heating pass in from the circumference of the drum, nearer to the center and upper end of the furnace. The ingoing ore is crushed to give a maximum size of 20 mm, while the outgoing concentrate is crushed to 3.8 mm after cooling.
Industry:Mining
This projector can be made at any colliery workshop from a few short pieces of piping and an old oil drum. It may be fixed in the drum or in an open tank of larger capacity placed 12 to 15 yd (11.0 to 13.7 m) back from the face of the hard heading. To the water in the drum, powdered washing soda is added at the ratio of 4 oz (113.4 g) to 5 gal (18.9 L) of water. About 2 min before firing, compressed air is turned on and ejections of 1471 water in the form of a coarse mist fill the heading. This continues for a period of 6 min after the firing. In this manner, the heading is filled with a mist of droplets that outnumber the dust particles; the latter are effectively wetted or become attached to the droplets, with the result that the dust rapidly settles out of the air. This mist projector has a high efficiency, particularly where the ventilation current is low.
Industry:Mining
This pump is often of the single-acting bucket or ram type with single or double cylinders and either with or without a flywheel. Vertical pumps may be used where headroom is adequate but area restricted, although horizontal reciprocating pumps are more generally used.
Industry:Mining
This pump--sometimes called a regenerative pump--is classified with centrifugal pumps, but is designed to develop several times the head obtained from a centrifugal pump having the same-diameter impeller and the same speed. The maximum head developed does not have the same relation to the impeller diameter and speed of the centrifugal pump; it involves size and spacing of the impeller vanes, fluid channels, and other factors.
Industry:Mining
This sediment sampler consists of a Plexiglas cylinder closed at each end by an ordinary rubber force cup. The two cups are connected by a length of surgical rubber tubing inside the cylinder, prestressed enough to permit the force cups to retain the sample in the cylinder. In the armed position, the two cups are pulled outside the cylinder, where they are restrained by a releasing mechanism attached to the outside wall. Two short loops of wire connect the cups to the releasing mechanism. The cups are released underwater by sending a messenger down the hydrographic wire. This sampler does not invert, which prevents use of reversing thermometers in conjunction with sampling.
Industry:Mining
This sinking system consists in the use of a cutting shoe on the bottom of a shaft lining that is being continually augmented as the shoe descends, the material inside the lining being excavated.
Industry:Mining
