A mixture that when once ignited, will allow flame to be self-propagated
throughout the mixture, independent of and away from the source of
ignition. In coal mines, it is only when methane and air are mixed in
certain definite proportions that the mixture is flammable and explosive,
and will allow flame to spread in all directions.
See also:limits of flammability
Derb. Clay ironstone in beds or seams.
See also:resonance screen
Applied to a vein widening.
A truck or trolley wheel having a flange or flanges at the edge to keep it
from leaving the rail. Crispin
A syn. for limb of a fold.
a. A hole bored ahead of a working place, when approaching old workings.
CTD
b. A borehole to detect water, gas, or other danger, driven from the side
of an underground excavation in a line not parallel with the centerline of
the excavation. Also called flank bore; flanking hole. BS, 10
A shothole drilled at an acute angle to the coal face for the purpose of
trimming it. BS, 12
Holes bored into the face at an angle which may vary from 30 degrees to 60
degrees to the line of face and 6 to 7 ft (1.8 to 2.1 m) long. The
distance between shot holes, the angle of the hole, and the charge, depend
to a great extent on the hardness of the coal. As the coal grows harder,
the burden on each shothole must be reduced by placing the shotholes
closer together and reducing the angle of the hole to the face.
McAdam, 2
a. See:clack
b. The hinged, flat disk mounted inside the lower end of a core barrel
that closes and holds the sample when the barrel is withdrawn from a
boring.
A laborer who flattens copper starting sheets by beating them against a
rigid steel or copperplate with a wooden paddle to remove folds, buckles,
and creases, which tend to cause short circuits during electrolytic copper
refining. Syn:clack
Eng. An air crossing fitted with a double door or valve giving direct
communication between the two air currents when forced open by the blast
of an explosion.
a. Striking through the slag-covered surface of molten copper with a
rabble blade just before the bath is poled to hasten oxidation.
ASM, 1
b. Striking the surface of molten copper with an iron scraper or rabble to
increase the surface exposed to the air. Mersereau, 1
Eng. Rectangular wooden valves about 24 in by 18 in by 1-1/2 in (61 cm by
46 cm by 3.8 cm) thick, hung vertically to the framework of the air
chambers of a ventilator. A flap valve.
Nonreturn valve formed by a hinged flap, which rises as fluid is drawn up
through a pipe or chamber and falls back on seating to prevent return
flow. Pryor, 3
A dragline bucket with a bowl of aluminum alloy covered top and bottom
with steel wearing plates. Sides and back are of steel plates, and
manganese steel is used for the lip and teeth. This bucket has no arch;
thus weight is minimized. The sides are flared, permitting heaped loading,
and the bucket dumps backward, not forward, thereby giving a somewhat
longer dumping range. Lewis
Coarse-grained blastomylonite formed by dislocation metamorphism of a
gabbro. Flakes of mica or chlorite sweep around augen of feldspar and/or
quartz with much recrystallization and neomineralization.
See also:mylonite gneiss
A structure in dynamically metamorphosed rock in which lenses and layers
of original or relatively unaltered granular minerals are surrounded by a
matrix of highly sheared and crushed material, giving the appearance of a
crude flow structure; e.g., flaser gabbro. CF:augen structure
AGI
A box in which a light source, an electromagnet, and a telescope are all
mounted in the pendulum apparatus of gravitational recording. AGI
An appliance in which the moist coal is fed into a column of
upward-flowing hot gases and moisture removal is virtually instantaneous.
Suspension dryers were widely used in the United States for drying coals
from 1/2 in (1.3 cm) downwards in size. See also:Cascade coal dryer;
Raymond flash dryer; suspension dryer; thermal drying. Nelson
Shallow lakes created by the removal of coal. Briggs