Furnace with series of horizontal stepped hearths each equipped with
stirring rabbles. Used to sweet-roast or desulfurize pyritic concentrates,
notably gold-bearing sulfides. Moist-to-wet feed progresses step by
downward step, meeting hot gases produced toward discharge end from
burning pyrite. Pryor, 3
That portion of the total tension in a conveyor belt effective in actually
moving the loaded belt. It is often referred to as horsepower pull.
Effective tension is the difference between tight side tension and slack
side tension.
A product of the weight, strength and the degree of packing, calculated
per volume of a given drill hole. Langefors
a. The size of an excavation within its stress ring; it includes not only
the actual hole in the rock but the destressed loose and semiloose rock
that surrounds it. Spalding
b. Particle diameter corresponding to 10% finer on the grain-size curve.
Also called effective size. ASCE
In mining, effective grounding means that the path to ground from
circuits, equipment, or conductor enclosures is permanent and continuous
and has carrying capacity ample to conduct safely any currents liable to
be imposed upon it. The path to ground associated with high-voltage
alternating-current systems will have impedance low enough to limit
potential above ground to a maximum of 100 V during the flow of ground
fault current and to facilitate operation of the circuit protective
devices. On low-voltage systems the sustained voltage above ground,
appearing on the frames of power utilizing equipment during existence of a
ground fault, will not be greater than 35 V; except when ground circuit
check systems requiring higher voltage are used, a maximum of 100 V for a
duration of 0.2 s is permissible. When bonded or mechanically connected
track is available, such track is considered the grounding medium for
direct current equipment only.
A measure of the ability of a rock to transmit a given fluid when the rock
contains more than one fluid. Inst. Petrol.
The weighted average weight of the pieces of sink material as found by
separating a given coal product at any required specific gravity.
Syn:piece weight
The area of solid coal within the fractured and crushed edges of the
pillar. Nelson
a. The ratio of the volume of liquid that a given mass of saturated rock
or soil will yield by gravity to the volume of that mass. AGI
b. The property of rock or soil containing intercommunicating interstices,
expressed as a percent of bulk volume occupied by such interstices.
AGI
c. The ratio of the volume of the voids of a soil mass that can be drained
by gravity to the total volume of the mass. ASCE
The cut point (equal errors or partition size) at which a screening
process operates in dividing the material treated into two size fractions.
BS, 5
Total area of the apertures expressed as a percentage of the useful area
of a screen. Syn:open area
The distance between the centers of support, or the clear distance between
supports plus the effective depth of the beam or slab, the lesser value
being taken. Taylor
The number of sprocket teeth that engage the chain rollers during one
revolution of the sprocket. Applies to sprockets for double-pitch roller
chains. Jackson, 1
A measure of warmth that is often employed to assess the health and
comfort conditions of mine workings, which are a function of dry- and
wet-bulb temperatures and air velocity. See also:dehumidification;
dry kata cooling power. Nelson
The unit weight of a soil that, when multiplied by the height of the
overlying column of soil, yields the effective pressure due to the weight
of the overburden. See also:unit weight
A technical officer who examines processes, methods, and operations in a
mine, mill, or smelter, and connecting links, with a view to their
improvement of maintenance at an agreed operating standard.
The ratio of the power output to the total power input.
Coal Age, 1
The weight of underflow (excluding oversize) expressed as a percentage of
the total weight of material below the reference size in the feed.
BS, 5
In coal washing this may be expressed as: Efficiency, percent = Actual
yield of clean coal X 100 / Theoretical yield at the ash content of the
clean coal. The efficiency of separation thus expresses as a percentage,
that proportion of the float coal obtained by float-and-sink analysis that
will be recovered in practice by a particular washer. The theoretical
yield is derived by plotting the cumulative yield of the reconstituted
feed coal against the appropriate cumulative ash content and reading off
the yield corresponding to the ash content of the clean coal actually
obtained. See also:washery
The weight of material correctly placed above or below the reference size,
expressed as a percentage of the weight of corresponding material in the
feed. BS, 5
For a given air quantity, the efficient airway size is that size for which
the combined capital and operating cost is minimal. Hartman, 2