MOLECULEA small natural particle of
matter composed of two or more atoms.
MOTORA device that converts fluid power
into mechanical force and motion. It usually
provides rotary mechanical motion.
motor in which the displacement per unit of
output motion cannot be varied.
MOTOR, LINEAR(See Cylinder.)
MOTOR, ROTARYA motor capable of
continuous rotary motion.
MOTOR, ROTARY LIMITEDA rotary
motor having limited motion.
A motor in which the displacement per unit of
output motion can be varied.
NEOPRENEA synthetic rubber highly
resistant to oil, light, heat, and oxidation.
NEUTRALIZATION NUMBERA mea-
sure of the total acidity or basicity of an oil; this
includes organic or inorganic acids or bases or a
combination of them.
OXIDATIONThe process by which oxygen
unites with some other substance, causing rust or
PACKINGA class of seal that is used to
provide a seal between two parts of a unit which
move in relation to each other.
PASCALS LAWA pressure applied to a
confined fluid at rest is transmitted with equal
intensity throughout the fluid.
PERIPHERYThe outside surface, espe-
cially that of a rounded object or body.
PIPEA type of fluid line whose dimensions
are designated by nominal (approximate) inside
diameter and wall thickness.
PNEUMATICSEngineering science per-
taining to gaseous pressure and flow.
PORTAn internal or external terminus of
a passage in a component.
POTENTIAL ENERGYThe energy a sub-
stance has because of its position, its condition,
or its chemical composition.
POUR POINTThe lowest temperature at
which a liquid will flow under specified con-
POWER UNITA combination of pump,
pump drive, reservoir, controls, and conditioning
components which may be required for its
POWERThe rate of doing work or the rate
of expanding energy.
PRESSUREThe amount of force distrib-
uted over each unit of area, usually expressed in
pounds per square inch.
PRESSURE, ABSOLUTEThe sum of
atmospheric and gauge pressures.
exerted by the atmosphere at any specific location.
PRESSURE, BACKThe pressure encoun-
tered on the return side of a system.
PRESSURE, DIFFERENTIALThe dif-
ference in pressure between any two points of a
system or a component.
PRESSURE, HEADThe pressure due to the
height of a column or body of fluid. It is usually
expressed in feet.
PRESSURE, OPERATINGThe pressure at
which a system operates.
PRESSURE, PRECHARGEThe pressure
of compressed gas in an accumulator prior to the
admission of a liquid.
PRESSURE, PROOFThe nondestructive
test pressure in excess of the maximum rated
PRESSURE, STATICThe pressure in a
fluid at rest.
PRESSURE SWITCHAn electrical switch
operated by the increase or decrease of fluid