| Panel - A mining block that
generally comprises one operating unit. |
|
| Panic bar - A switch, in the
shape of a bar, used to cut off power at the machine in case of an emergency. |
|
| Parting - (1) A small joint in
coal or rock; (2) a layer of rock in a coal seam; (3) a side track or turnout in a haulage
road. |
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| Percentage extraction - The
proportion of a coal seam which is removed from the mine. The remainder may represent coal
in pillars or coal which is too thin or inferior to mine or lost in mining. Shallow coal
mines working under townships, reservoirs, etc., may extract 50%, or less, of the entire
seam, the remainder being left as pillars to protect the surface. Under favorable
conditions, longwall mining may extract from 80 to 95% of the entire seam. With pillar
methods of working, the extraction ranges from 50 to 90% depending on local conditions. |
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| Percussion drill - A drill,
usually air powered, that delivers its energy through a pounding or hammering action. |
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| Permissible - That which is
allowable or permitted. It is most widely applied to mine equipment and explosives of all
kinds which are similar in all respects to samples that have passed certain tests of the
MSHA and can be used with safety in accordance with specified conditions where hazards
from explosive gas or coal dust exist. |
|
| Permit – As it pertains
to mining, a document issued by a regulatory agency that gives approval for mining
operations to take place. |
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| Pillar - An area of coal left
to support the overlying strata in a mine; sometimes left permanently to support surface
structures. |
 |
| Pillar robbing - The
systematic removal of the pillars between rooms or chambers to regulate the subsidence of
the roof. Also termed "bridging back" the pillar, "drawing" the
pillar, or "pulling" the pillar. |
|
| Pinch - A compression of the
walls of a vein or the roof and floor of a orebodyso as to "squeeze" out the
ore. |
|
| Pinning - Roof bolting.
|
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| Pitch - The inclination of a
seam; the rise of a seam. |
|
| Placer - any deposit of
minerals not in place, usually occurs in gravel |
|
| Plan - A map showing features
such as mine workings or geological structures on a horizontal plane. |
|
| Porosity - the void space in
rock or soil, usually expressed as the ratio of the volume of voids to the total volume of
the material. |
 |
| Portal - The structure
surrounding the immediate entrance to a mine; the mouth of an adit or tunnel. |
|
| Post - The vertical member of
a timber set. |
|
| Powder - the miner's term for
dynamite. |
|
| Pressure - the force per unit
area. |
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| Primer (booster) - A package
or cartridge of explosive which is designed specifically to transmit detonation to other
explosives and which does not contain a detonator. |
|
| Prop - Coal mining term for
any single post used as roof support. Props may be timber or steel; if steel--screwed,
yieldable, or hydraulic. |
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