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Doc No: OMM50001254
Rev: A Page 44 of 47
Subject to contractual terms and conditions to the contrary, this document and all the information contained herein are the confidential and exclusive
property of FMC Technologies, and may not be reproduced, disclosed, or made public in any manner prior to express written authorization by FMC.
FLOODED SUCTION
Implies that the level of liquid in the suction
vessel is above the centerline of the suction
port of the pump.
FLUID END
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
the Liquid End. It is called a valve chamber in
old literature.
NPSHa
An abbreviation that stands for Net Positive
Suction Head Available. NPSHA is the total
suction pressure, including allowance for
acceleration head, available from the system at
the pump suction connection, minus the vapor
pressure of the liquid at actual pumping
temperature. NPSHA for a reciprocating pump
is normally expressed in units of feet of water.
NPSHr
An abbreviation that stands for “Net Positive
Suction Head Required”. This is the minimum
total inlet pressure required by the pump for
proper operation. This value is a function of
pump design and speed and is determined by
the pump manufacturer through a specific
NPSH test. NPSHA should exceed NPSHR by
at least 5 feet.
PISTON
A type of power pump that uses a cylindrical
seal (piston) mounted on a holder to drive fluid
through the valves. The piston seal
reciprocates within a stationary cylinder.
POWER PUMP
A reciprocating pump that drives the pumping
element(s) using a slider crank mechanism.
Power pumps are piston, plunger, or
diaphragm type. All require a driver with a
rotating shaft, such as a motor or engine, as a
power source.
POWER FRAME
The major portion of a power pump that
encloses and supports all other components of
the power (or drive) end. It is called a pump
case in old literature.
STROKE LENGTH
The length of one complete, unidirectional
motion of the piston or plunger. Stroke length
is usually expressed in inches.