Gr. Brit. At the National Coal Board collieries, in order to assess the
degree of concentration, certain basic data are collected, involving the
pithead output, length of main haulage roads, and length of coalface in
production. See also:face concentration; geographical concentration;
overall concentration. Nelson
A group or series of sedimentary rocks having some characteristic in
common; specif. coal measures. The term apparently refers to the old
practice of designating the different seams of a coalfield by its measure
or thickness. AGI
A heading or drift made in various strata. Fay
A surveyor's chain, containing 100 links of 7.92 in (20.12 cm) each.
A bin installed adjacent to the shaft bottom in skip winding. The capacity
of the chute is equal to that of the skip used, ranging from 4 to 10 st
(3.6 to 9.1 t). Bin-feeding arrangements differ but may be by a steelplate
conveyor from a surge bunker that in turn receives the ore or coal from
the mine cars or a trunk conveyor. A measuring chute ensures a quick and
correct loading of skips without spillage. Immediately the skip is
positioned in line, the measuring chute bottom door opens and material is
discharged into the skip. See also:pocket
Nelson
The day when face or other work is measured and recorded for assessing
wages. Nelson
In flotation, that portion of the feedback elements that converts the
signal from the primary detecting element to a form compatible with the
reference input. Fuerstenau
Storage space near an entry from underground workings to a hoisting shaft;
laid out so as to deliver a measured volume into a hoisting skip and to be
refilled before the skip returns empty. Pryor, 3
A graduated tape, steel or linen, usually in 50-ft or 100-ft (15-m or
30.4-m) lengths; used by engineers, builders, surveyors, etc.
Crispin
A device for measuring the flow of water. It generally consists of a
rectangular, trapezoidal, triangular, or other shaped notch in a thin
plate in a vertical plane through which the water flows. The weir head is
an index of the rate of flow. See also:notch
Ratio between the resistance or load raised by a machine, and the applied
force. Mechanical advantage divided by velocity ratio gives the efficiency
of the machine. Hammond
A flotation machine that utilizes pulp-body concentration by the agitation
froth method and bubble-column action by pneumatic and cascade means.
Taggart, 1
Determination of the particle-size distribution of a soil, sediment, or
rock by screening, sieving, or other means of mechanical separation; the
quantitative expression of the size-frequency distribution of particles in
granular, fragmental, or powdered material. It is usually expressed in
percentage by weight (and sometimes by number or count) of particles
within specific size limits. See also:particle-size analysis
AGI
One of the machines, such as the Dorr classifier, that are commonly used
to classify a ball-mill or rod-mill discharge into finished product and
oversize. Newton, 1
A clay formed from the products of the abrasion of rocks.
The removal of impurities by mechanical units as compared with hand
picking. Broadly, mechanical cleaning may be subdivided into dry cleaning
and wet cleaning. Mitchell; Nelson
The ratio of the air-indicated horsepower to the indicated horsepower in a
power cylinder, in the case of compression driven by steam or
internal-combustion engines, and to the brake horsepower delivered to the
shaft in the case of a power-driven machine. Lewis
Amount of mechanical energy that can be transformed into a single heat
unit; the equivalent of 778 ft.lbf/Btu (1,000 N.m/kJ). Hammond
An appliance for measuring strain; often used in roof control
investigations. It employs a micrometer dial gage actuated through a lever
giving initial magnification of the movement.
See also:acoustic-strain gage; electrical resistance strain gage.
Nelson
A cell in which the solids-water pulp feed is kept agitated, and is
circulated by means of an impeller mounted at the bottom of a vertical
shaft. The rotating impeller creates vacuum enough to draw air down the
standpipe surrounding the impeller shaft, and the impeller disperses the
air throughout the pulp in the form of small bubbles. The flotable
minerals are carried upward by the bubbles and eventually collect in the
froth above the pulp in the machine. Automatic scrapers remove the
mineral-laden froth that contains the concentrate, and after the values
have been removed, the barren pulp containing the tailing flows out of the
cell. Newton, 1
/; N ûN µ÷ e DICTIONARY TERMS:mechanical loader A power machine for loading mater
[\B]mechanical loader[\N]
A composition of two or more substances, each remaining distinct, and
generally capable of separation by mechanical means. Standard, 2