
Doc. No.: OMS500000104
Rev: A Page 41 of 42
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property of FMC Technologies, and may not be reproduced, disclosed, or made public in any manner prior to express written authorization by FMC.
N P S H A
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.
N P S H R
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.
P I S T O N
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.
P L U N G E R
A type of power pump that uses a cylindrical element or
“plunger” to drive fluid through the valves. The plunger
reciprocates through a stationary set of seals known as
packing.
P O W E R P U M P
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.
P O W E R F R A M E
The major portion of a power pump that encloses and supports
all other components of the power (or drive) end.
S T R O K E L E N G T H
The length of one complete, unidirectional motion of the
piston or plunger. Stroke length is usually expressed in
inches.
V A L V E
A component that allows unidirectional flow of liquid. FMC
pumps have a series of two valves, one inlet or suction and
one discharge, per pumping cylinder.