HEAD, VELOCITYThe equivalent head
through which the liquid would have to fall to
attain a given velocity. Mathematically it is equal
to the square of the velocity (in feet) divided by
64.4 feet per second square.
HEAT EXCHANGERA device that
transfers heat through a conducting wall from one
fluid to another.
HYDRAULICSEngineering science pertain-
ing to liquid pressure and flow.
HYDROMETERAn instrument for deter-
mining the specific gravities of liquids.
HYDROPNEUMATICSPertaining to the
combination of hydraulic and pneumatic fluid
pertaining to the energy of liquids at rest.
IMPACT PRESSUREThe pressure of a
moving fluid brought to rest that is in excess of
the pressure the fluid has when it does not flow;
that is, total pressure less static pressure. Impact
pressure is equal to dynamic pressure in incom-
pressible flow; but in compressible flow, impact
pressure includes the pressure change owing to the
IMPINGEMENTThe striking or dashing
upon with a clash or sharp collision, as air
impinging upon the rotor of a turbine or motor.
IMPULSE TURBINEA turbine driven by
a fluid at high velocity under relatively low
INERTIAThe tendency of a body at rest to
remain at rest, and a body in motion to continue
to move at a constant speed along a straight line,
unless the body is acted upon in either case by an
INHIBITORAny substance which slows or
prevents chemical reactions such as corrosion or
INVERSE PROPORTIONThe relation that
exists between two quantities when an increase in
one of them produces a corresponding decrease
in the other.
KELVIN SCALEThe temperature scale
using absolute zero as the zero point and divisions
that are the same size as centigrade degrees.
KINETIC ENERGYThe energy that a
substance has while it is in motion.
KINETIC THEORYA theory of matter that
assumes that the molecules of matter are in
LINEA tube, pipe, or hose that is used as
a conductor of fluid.
LIQUIDA form of matter that has a
definite volume but takes the shape of its
LOADThe power that is being delivered by
any power-producing device. The equipment that
uses the power from the power-producing device.
LUBRICATORA device that adds
controlled or metered amounts of lubricant into
a fluid power system.
MANIFOLDA type of fluid conductor that
provides multiple connections ports.
MANOMETERA differential pressure
gauge in which pressure is indicated by the height
of a liquid column of known density. Pressure is
equal to the difference in vertical height between
two connected columns multiplied by the density
of the manometer liquid. Some forms of
manometers are U tube, inclined tube, well, and
MATTERAny substance that occupies
space and has weight.
MECHANICAL ADVANTAGEThe ratio
of the resisting weight to the acting force. The
ratio of the distance through which the force is
exerted divided by the distance the weight is
METER-INTo regulate the amount of fluid
into a system or an actuator.
METER-OUTTo regulate the flow of fluid
from a system or actuator.
MICRONA millionth of a meter or about