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 hammer. Read more.
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 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 damage 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.
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.
Wetted surface - the internal surface of a pump that comes in direct contact with the pumped liquid. Read more.
Whirl - see oil whirl.
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.
[ * ] Some information are excluded in this article. Read more.