Water hammer: This phenomenon occurs in a piping system when there are rapid fluctuations in pressure, often caused by sudden changes in pump conditions or the abrupt opening or closing of a valve.

Water Horse Power (WHP): The horsepower equivalent of the pump, which can be calculated using the following formula: WHP = head x gpm / 3960.

Water NPSHR: The Net Positive Suction Head Required for a pump when it is pumping water. This value serves as a baseline for estimating the NPSHR when the pump handles other types of liquids.

Watt: A unit of measurement for work. It represents the rate at which work is done when an object maintains a constant velocity against an opposing force of one Newton. (Units are Newton meters/second).

Wave spring: A specialized washer used in mechanical seals when axial space is limited.

Wear ring: Found in closed impeller pumps, this component restricts leakage from the discharge to the inlet and should be replaced if the recommended clearance is doubled.

Welded metal bellows: A mechanical seal design employing metal instead of elastomer, particularly suitable for cryogenic and high-temperature applications.

Wet critical speed (API 610): The critical speed of a rotor that considers the effects of the pumped fluid. It is distinct from the dry critical speed.

Wet end: The section of the pump that comes into contact with the fluid being pumped, including components such as the stuffing box, impeller, and volute.

Wetted surface: Refers to any internal surface of a pump that comes into contact with the process fluid.

Wobble plate: A plate attached to a rotating component to minimize vibration at high speeds by balancing the system.

Related Links

• Pump Glossary
• Pump info