SECTION II. DEFINITION OF UNUSUAL TERMS
The following definitions include the terms used in this manual that are not
defined in the text or not listed in the Army Dictionary (AR 310-25).
Head - The pressure against which a pump forces liquid, expressed in feet.
Each pound of pressure per square inch against which the liquid is forced is
equivalent to lifting a column of water l-inch square and 2.31 feet high.
head includes the height to which the liquid must be raised plus the force
required to overcome friction losses in the pipeline or hoseline.
Net positive suction head - The absolute pressure at the pump inlet expressed in
feet of liquid, plus velocity head, minus the vapor pressure of the fluid at
If the inlet liquid is exposed to the atmosphere, it is
also necessary to correct for the elevation at the entrance to the pump impeller.
Suction Pressure - As used on pump suction gauges, the negative or positive
pressure at the pump suction inlet.
It will be a negative pressure if the inlet
liquid is exposed to the atmosphere below the suction inlet (such as a source
pump taking water from a well, stream, or lake).
It will be a positive pressure
if the inlet liquid is from an elevated source (such as a storage tank) or an
Total discharqe head - The sum of the suction pressure and the discharge pressure,
expressed in feet.