Eng. The pit bottom, level, or inset at which the cages are loaded.
Fay
A small fenced pulley hung from the roof or side of a haulage road in
which the tail rope of a main-and-tail haulage is suspended. It keeps the
rope (which is not used for direct haulage of cars) clear of the roadway
and minimizes friction while in motion. The swinging of hanging pulleys
and ropes is a hazard to people traveling on the roadway. Nelson
Scot. A movable platform in a shaft attached to a winding rope.
Scot. Timbers from which cribs are suspended in working through soft
strata.
a. The overlying side of an orebody, fault, or mine working, esp. the wall
rock above an inclined vein or fault. See also:wall; walls; top wall.
Syn:hanger
b. Sticking or wedging of part of the charge in a blast furnace.
Fay
In the United States, a horizontal gallery driven in the hanging wall of a
vein. Nelson
The upper wall of an inclined fault plane. Ballard
Underground, blockage of ore pass or chute by rock. Pryor, 3
See:aplite
a. Containing certain mineral salts in solution, esp. calcium carbonate;
said of water having more than 8 to 10 grains/gal (137 to 171 mg/L) of
such matter to the gallon. Standard, 2
b. Solid; compact; difficult to break or scratch.
See also:hardness scale
A condition encountered in some open-cut mines wherein the rock
occasionally will not be broken down to grade because of an extra-hard
streak of ground or because not enough explosive is used. This is called a
"hard bottom"; it interferes with work and puts undue strain on a shovel.
Such unbroken ores usually are drilled with a jackhammer and blasted.
a. All coal of higher rank than lignite. BS, 4
b. In the United States, the term is restricted to anthracite.
See also:anthracite
A plow type of cutter loader for cutting the harder coal seams. It
consists of stepped kerving bits that precut the coal, leaving the
unstressed coal to be cut by the following bits. The kerving bits may be
either rigid or swiveling. See also:rapid plow
Nelson
Unaltered kimberlite below the zone of blue ground. CF:blue ground
AGI
Steel that has been hardened by quenching from or above the hardening
temperature. Fay
An alloy, rich in one or more alloying elements, added to a melt either to
permit closer composition control than is possible by addition of pure
metals or to introduce refractory elements not readily alloyed with the
base metal. ASM, 1
Metallurgical process in which iron or suitable alloy is quenched by
abrupt cooling from or through a critical temperature range.
See also:precipitation hardening
Liquids into which steel is plunged in hardening. They include cold water,
various oils, and water containing sodium chloride or hydroxide to
increase the cooling power. CTD
Rock that is difficult to work.
Empirical index of grindability of ores or minerals, reached as result of
comminution of a test sample under stated conditions of control.
Pryor, 3
This test utilizes a special grindability mill of the ring-and-ball type,
in which a 50-gm portion of closely sized coal is ground for 60
revolutions. This method is of the constant-work type; i.e., a fixed
amount of work is expended on each coal, and a grindability value is
determined from the size composition of the ground material.
Mitchell