Doc. No.: OMS500000104
Rev: A Page 40 of 42
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Glossary of Commonly Used Terms
C A P A C I T Y
The total volume throughput per unit of time at suction
conditions. It includes both liquid and any dissolved or
entrained gases. For all practical purposes this can be
considered the volume flow rate in the suction pipe. The
standard unit of pump capacity is U.S. gallons per minute
(GPM).
C A V I T A T I O N
The state where fluid pressure drops below vapor pressure,
causing the liquid to begin to change from a liquid to a gas
and boil. Usually occurs in the chamber between the suction
and discharge valves during the suction stroke, and often
sounds like a mechanical knock. Cavitation results in the
formation of gas bubbles, or cavities, in the fluid that cause
vibration and damage when they are collapsed by the
increased fluid pressure on the discharge stroke.
D A M P E N E R
A device that reduces pressure pulsations in the suction or
discharge piping. This may be referred to as a suction
stabilizer, accumulator, or surge suppressor.
D I S P L A C E M E N T
The volume swept by all pistons or plungers per unit time.
This term is typically expressed as gallons per revolution.
P O W E R E N D
The portion of the pump that converts supplied rotary motion
into linear motion used by the Fluid End to move the
pumpage.
E F F I C I E N C Y
Mechanical efficiency is the ratio, expressed as a percentage,
of pump power output to the pump power input. The
mechanical efficiency of reciprocating pumps is very high,
typically in excess of 90%. Volumetric efficiency is the ratio
of actual pump capacity to theoretical displacement
F L O O D E D S U C T I O N Implies that the level of liquid in the suction vessel is above
the centerline of the suction port of the pump.
F L U I D E N D
The portion of the pump that converts the linear motion
supplied by the power end into fluid flow at pressure. This
may also be called a Liquid End.