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ratio of size reduction

Ratio of the upper particle size in the crushed material to the upper
particle size of the feed material. BS, 5

rattle boxes

Limonite geodes from Chester County, PA. Schaller

rattler

a. York. Cannel coal.
b. Scot. Inferior gas coal; sandy shale.
c. U.K. A variety of gas coal that fetched high prices and was reputed to
ignite with a match. It is hard, compact, uniform, bright, brittle,
fine-grained, slightly sonorous when struck, and resembling jet but not so
brilliant. Arkell
d. A revolving steel drum with a charge of metal spheres used for testing
the abrasive resistance of brick.
e. A device for shaking out the cores from small castings, such as a
tumbling barrel.

rattler test

A method for evaluating the resistance of paving bricks to impact and
abrasion. A sample of 10 bricks is subjected to the action of 10 cast-iron
balls 3.75 in (9.53 cm) in diameter and 245 to 260 balls 1.875 in (4.76
cm) in diameter in a drum 28 in (71.12 cm) in diameter, 20 in (50.8 cm)
long, rotating at 30 rpm for 1 h. The severity of abrasion and impact is
reported as a percentage loss in weight. Dodd

rattlesnake ore

A gray, black, and yellow mottled ore of carnotite and vanoxite, its
spotted appearance resembling that of a rattlesnake. AGI

rauvite

A mineral, Ca(UO2 )2 V10 O28 .16H2 O ;
radioactive; purple- black; sandstone impregnation on the Colorado
Plateau.

ravelly ground

Rock that breaks into small pieces when drilled and tends to cave or
slough into the hole when the drill string is pulled, or binds the drill
string by becoming wedged or locked between the drill rod and the borehole
wall. Long

ravine

A small, narrow, deep depression, smaller than a gorge or a canyon but
larger than a gully, usually carved by running water; esp. the narrow
excavated channel of a mountain stream. Etymol: French, mountain torrent.
AGI

raw

a. In ceramics, fresh from a plastic process; unbaked. Standard, 2
b. Not prepared for use by heat. Webster 3rd

raw coal

Coal which has received no preparation other than possibly screening.
Syn:raw ore

raw coal screen

A screen used for dividing run-of-mine coal into two or more sizes for
further treatment or disposal; usually employed to remove the largest
pieces for crushing and readdition to the run-of-mine coal. BS, 5

raw dolomite

a. Dolomite that has not been calcined. ARI
b. Crushed dolomite used for dressing of basic open hearth bottoms and
banks. AISI

raw feed coal

Coal supplied to a plant or machine, in which it undergoes some form of
preparation. BS, 5

raw fuel

A fuel used in the form in which it is mined or obtained, for example,
coal, lignite, peat, wood, mineral oil, natural gas. Nelson

rawhide hammer

A hand hammer having a rawhide head that serves to prevent bruising metal
parts against which it is used. Crispin

raw material

The ingredients before being processed that enter into a finished product.
Crispin

raw mica

A term commonly used for unmanufactured mica. Skow

raw ore

a. Ore that is not roasted or calcined.
b. See:raw coal

raydist

A radio system for medium-range precision surveying in which the phases of
two continuous-wave signals are compared. It is based on the heterodyne
principle and uses low or medium frequencies. It requires a minimum number
of frequencies and these frequencies usually need bear no fixed
relationship with each other. Hunt

Rayleigh wave

a. A type of seismic surface wave having a retrograde, elliptical motion
at the free surface. It is named after Lord Rayleigh, the English
physicist who predicted its existence. Syn:R wave
b. A surface wave associated with the free boundary of a solid. The wave
is of maximum intensity at the surface and diminishes quite rapidly as one
proceeds into the solid. Therefore, it has a tendency to hug the surface
of the solid. Such waves have been used quite effectively in detecting
surface cracks and flaws in castings. Hunt

Raymond flash dryer

A suspension-type dryer that employs the principle of flash drying of fine
coal. The coal is transported vertically through a drying column in a
stream of hot gases. The source of heat for this system is usually an
automatic stoker. In this system, the hot gases are drawn into the drying
column by the action of the fan connected to the cyclone collector vent.
The coal to be dried is continuously introduced to the hot gas stream.
Virtually instantaneous drying occurs. The dried coal and the
moisture-laden gases are drawn into the cyclone collector. The dry coal
drops to the bottom of the collector and the moisture-laden gases are
discharged by the fan to the atmosphere. See also:thermal drying
Kentucky; Mitchell