a. The quantity of infiltration of ventilation air in cubic meters per
second divided by the volume of the room gives the number of so-called air
changes during a given interval of time. Tables of the recommended number
of such air changes for various rooms are used for estimating purposes.
b. The act of instituting a different pattern of air flow in a mine.
In a reverberatory furnace, flues under the hearth and fire bridge through
which air is forced to avoid overheating. Henderson
a. A large volume of air, under compression, used in lieu of a liquid as a
medium to cool the bit and eject drill cuttings from a borehole.
Syn:air flush
b. The general process of moving air around the openings of a mine.
See also:air
a. In powder metallurgy, the separation of powder into particle-size
fractions by means of an airstream of controlled velocity; an application
of the principle of elutriation. ASM, 1
b. Sorting of finely ground minerals into equal settling fractions by
means of air currents. These are usually controlled through cyclones,
which deliver a coarse spigot product and a relatively fine vortical
overflow. See also:infrasizer
c. A method of separating or sizing granular or powdered materials, such
as clay, through deposition in air currents of various speeds. This
principle is widely used in continuous pulverizing of dry materials, such
as frit, feldspar, limestone, and clay. See also:air classifier;
air elutriator. Enam. Dict.
An appliance for approx. sizing crushed minerals or ores by means of
currents of air. See also:air classification; air elutriator.
CTD
A coal-cleaning method that utilizes air to remove the dust and waste from
coal. Air cleaning requires that the coal contain less than 5% of surface
moisture as a rule. It is effective only in the coarse sizes (plus 10 to
28 mesh) and is best suited to coals having a sharply defined line between
coal and refuse material. Predrying to reduce the moisture content of the
coal ahead of the air treatment is not uncommon. It is a less expensive
and also a less accurate method of cleaning coal than the wet-cleaning
method. Kentucky
An airtight portion of any shaft, winze, raise, or level used for
ventilation. BS, 8
The simultaneous control, within prescribed limits, of the quality,
quantity, temperature, and humidity of the air in a designated space. It
is essentially atmospheric environmental control. Control of only one or
two of these properties of the atmosphere does not constitute air
conditioning. The definition and correct usage require that the purity,
motion, and heat content of the air must all be maintained within the
prescribed limits. Hartman, 2
When conditioning is designed to perform only one or a limited number of
functions, then it should be so designated. Air-conditioning processes
include dust control, ventilation, dehumidification, cooling, heating, and
many others. See also:aftercooler; air receiver; compressed air;
duplex compressor; rotary compressor; turbocompressor. Hartman, 2
The material resulting from solidification of molten blast-furnace slag
under atmospheric conditions. Subsequent cooling may be accelerated by
application of water to the solidified surface. ASTM
a. Ventilating passage underground. Pryor, 3
b. A passage through which air is circulated, particularly a long
passageway driven parallel to the workings to carry the air current.
See also:airway
The system of colliery ventilation, introduced about 1760, by which the
intake air current was made to traverse all the underground roadways and
faces before passing into the upcast shaft. Nelson
Stain formed by air entering at edges of mica sheets and penetrating along
cleavage planes. Skow
A bridge where a return airway passes over (overcast) or under (undercast)
an intake airway. It is generally constructed with concrete blocks,
structural steel, and/or sheet metal, and is made airtight to prevent
intermixing of the two air currents. The mining law requires an air
crossing to be so constructed as not to be liable to be damaged in the
event of an explosion. Syn:air bridge; bridge; overcrossing; overgate.
See also:overcast; undercast. Nelson
a. The flow of air ventilating the workings of a mine. Syn:airflow;
air quantity. BS, 8
b. A body of air moving continuously in one direction. Jones, 1
Air trapped in the bottom of a dry borehole by the rapid descent of a
tight string of borehole equipment. Syn:air block
Primarily a vessel for extracting dust from the atmosphere. Nelson
The use of air space or a void within a blast hole between an explosive
charge and inert stemming to enhance the shock wave detonation force.
A cylindrical or bell-shaped container closed at the upper end and
attached in an upright position above and to the discharge of a
piston-type pump. Air trapped inside the closed cylinder acts as a
compressible medium, whose expansion and contraction tends to reduce the
severity of the pulsations imparted to the liquid discharged by each
stroke of a pump piston. Syn:bonnet; pressure dome. CF:dome
Long
A door erected in a roadway to prevent the passage of air. When doors are
erected between an intake and a return airway, they may be known as
separation doors. Syn:door; separation door; trapdoor. BS, 8
A system for breaking down coal by which compressed air, generated locally
by a portable compressor at 10,000 psi (69.0 MPa), is used in a releasing
cylinder, which is placed in a hole drilled in the coal. Thus, slow
breaking results, with no flame, in producing a larger percentage of lump
coal than is made by using explosives. Its principal advantage is that it
may be used with safety in gaseous and dusty mines.
See also:compressed-air blasting