A crystal, usually grown artificially, in which all parts have the same
crystallographic orientation. McGraw-Hill, 1
For double-pitch roller chains, a sprocket having one set of effective
teeth. Jackson, 1
A screen having one screening surface, not necessarily limited to one size
or shape of aperture. BS, 5
A system of opening a mine by driving a single entry only, in place of a
pair of entries. The air current returns along the face of the rooms,
which must be kept open.
single-entry room-and-pillar mining
See:room-and-pillar
A test in which coal dust is placed only in a single entry.
Rice, 2
An arrangement composed of individual soil particles; characteristic
structure of coarse-grained soils. See also:soil structure;
flocculent structure; honeycomb structure. ASCE
Rock drilling by hand; e.g., in narrow reefs. A drill steel held in the
left hand is struck blows with a 4-lb (1.8-kg) hammer, the drill being
turned between the blows. The drilling is very slow and laborious.
Nelson
A centrifugal fan in which air enters the impeller at one side only.
BS, 8
A ventilating fan that takes or receives its air from one side only.
a. A lightweight hammer, usually 4 lb (1.8 kg) or less. When used in hand
drilling holes in rock, the hammer is held in one hand and the drill is
held in the other. Long
b. Sometimes incorrectly used to designate a sinker drill. Long
c. A drill column having a single jackscrew in the bottom end.
See also:drill column
See:surface-set bit
Any underground opening separated from a free surface by a distance
greater than three times the size of the opening in the direction of the
free face.
For safety reasons, mines with only a single outlet (shaft) are subjected
to restrictions in the numbers of mine workers employed at a time.
Beerman
The conventional method of strip packing on a longwall face, in which the
widest pack is along the roadside. A single packing system varies but may
have a 10-yd (9.1-m) roadside pack, then 7 yd (6.4 m) of waste, followed
by 4-yd (3.7-m) packs and 5 yd (4.6 m) of waste repeated across the entire
face. See also:double packing; strip packing. Nelson
A two-wire circuit using alternating current. Kentucky
A conveyor in which power is transmitted to the belt by one pulley only.
NEMA, 2
Light refraction in an isotropic crystal or amorphous substance according
to Snell's law, as opposed to the birefringence of an anisotropic crystal.
S. Wales. A system of working coal by narrow stalls. Fay
A coal-crushing machine in which the roll teeth crack downward on the lump
and the roll itself compresses the coal against the breaker plates. Teeth
of two or more designs are used generally on the same roll, some for the
slugging, cracking, or blow action and others for a pulling and splitting
force. The breakers are not easy to stall by choking, since they will pass
a heavy overload, partly because of the action of a relief mechanism, with
which they are all equipped. Mitchell