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The following definitions are intended to give basic understanding of the terms
commonly used in the pump industry. Some industry standards, or customer
specifications, may have specific meaning of certain terms that may be different
from their common usage - in such case the terms should be interpreted in the
context of the standards, or specifications, being referred to.
Warm-up procedure –
Water hammer - When a liquid suddenly moves, stops, or changes velocity, the
dynamic energy amplifies the normal system pressure creating a pressure
surge, or spike. When the pressure surge accelerates and approaches the
speed of sound, the surge becomes in acoustic resonance with the sound wave.
The surge is amplified many times over the normal system pressure. This
pressure surge can be very destructive to system components, and is known as
Water HP (WHP) –
Water mark -
Water NPSHR - the net positive suction head (NPSHR) required by a pump
when it is pumping water. It is used as baseline value for estimating its NPSHR
when pumping other types of liquid.
Wear parts -
Wear plate [ * ]
Wear ring - a renewable ring that protects the impeller (rotating impeller ring) or
casing (stationary case ring) from wear, erosion, or corrosion damage. Such is
confined to the wear rings which are cheaper and easier to replace. The
clearance between the wear rings controls the leakage flow that provides
lubrication and cooling to the mating parts.
Weighing procedure –
Weld metal -
Weld procedure -
Weld repair -
Wet critical speed - API 610 defines wet critical speed as a rotor natural
frequency calculated considering the additional support and damping produced
by the action of the pumped liquid within internal running clearances at the
operating conditions and allowing for flexibility and damping within the bearings.
Simply stated, it is the rotor critical speed that takes into account the damping
effect of the pump liquid, hence the word wet. See dry critical speed.
Wet WR^2 -
Wetted surface - the internal surface of a pump that comes in direct contact
with the pumped liquid.
Wheel – slang for impeller.
Whirl - see oil whirl.
Witnessed test -
Wobble plate - an external plate, or support, added to a motor bracket, or
bearing housing, to dampen its vibration, or to minimize the shaft deflection. A
wobble plate is added as a fix, or remedy, to a high vibration problem.