- 行业: Mining
- Number of terms: 33118
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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 ...
In this cleaner, the coal is fed from a raw coal hopper by an oscillating plunger feeder ensuring uniform feed throughout the entire width of the machine deck. A rotating shutter in the inlet duct provides a pulsating air current, which is much more effective as a separating current than a uniform airstream. The coal and refuse stratify as they move toward the discharge end of the deck with the refuse falling to the bottom against the deck. The perforated deck has four refuse draws; normally the products of the first two draws are discharged as refuse and the third and fourth draws as middlings. The product of the third draw may be refuse or middlings, depending on the ash content of the feed. Generally, this cleaner is an effective machine for cleaning coal from 3/4 in (1.91 cm) to 1/4 in (0.64 cm) by 28 mesh if it contains less than 5% of surface moisture. It will not clean effectively below 20 mesh.
Industry:Mining
In this fan, the blades are mounted on the curved portion of a dish-shaped rotor and are designed to impart dynamic energy but no pressure or static energy to the air, the dynamic energy being converted to pressure in the diffuser. The fan is suitable for water gauges up to 20 in (50.8 cm) and there is an absence of noise. It is useful where the resistance of the mine is known and not liable to alter materially.
Industry:Mining
In this instrument, the internal comparison lamp is set to a standard brightness as indicated by a photoelectric cell and not by reference to a voltmeter or ammeter.
Industry:Mining
In this jig, raw coal is conveyed to a wash box through sluices. Air pulsations are transmitted through valves to water in a compartment adjacent to the washing bed, causing the water in the wash box to rise. Pulsating water causes the incoming fuel to be loosely suspended in the water and permits heavier refuse to sink to the screen plate while suspended coal spills over into the second compartment. In the second 1930 compartment the process is repeated with the remaining refuse sinking to the screen and clean coal discharging to the dewatering screens.
Industry:Mining
In this kind of excavation, there is complete access to the site from many directions, and the excavation banks can be sloped flatly on two or more sides. Usually shallower in depth than bulk pit excavations but larger in area. Compare: bulk pit excavation
Industry:Mining
In this method for the determination of incombustible matter, the mine roadway dust (dust containing carbonates) is incinerated at a temperature of not less than 500 degrees C and not more than 530 degrees C until it is constant in weight. This temperature is sufficient to complete the combustion of the organic matter in the dust, but is not high enough to decompose the carbonates. However, this method is unsuitable for dust containing magnesium carbonate because this substance decomposes below 500 degrees C, and therefore a low result for the incombustible matter would be obtained. The moisture content of the sample may be calculated so that an allowance can be made for the weight loss attributed to moisture.
Industry:Mining
In this method, digging tools or buckets are suspended on a steel cable and lowered to the sediment surface, where they are loaded and retrieved. Includes the use of dragbucket and clamshell dredges, and generally to a depth of not more than 500 ft (152 m) below sea level.
Industry:Mining
In this method, sticks of explosive are stuck on the side of a boulder with a covering of mud, and when detonated, very little of the energy of the explosive is used in breaking the boulder.
Industry:Mining
In this method, the orebody is worked from the top down in successive slices. In the working of each slice, the unit is worked as a shrinkage stope. The broken ore serves to give lateral support to the sides of the unit and also serves as a working platform from which the back is reached. After working a unit, the cover is caved. No timber mat is used. Also known as the Kimberley method.
Industry:Mining
In this method, two level drives are first connected, the lower and upper one by a raise, from the bottom of which mining is begun. The work proceeds upwards, filling the mined-out room, but in the filling, chutes are left through which the broken ore falls. In inclined seams the chutes, also inclined, have to be timbered. The lower-level drive is 2215 protected either by timbering or vaulting, or by a fairly strong pillar of vein fillings. Stoping in the different cuts always proceeds upwards, but as a whole it proceeds between the two level drives in a horizontal direction. Overhand cut-and-fill, esp. in mining irregular orebodies of greater size, is also called back stoping.
Industry:Mining
