Glossary of Pump Terms: V

Vacuum: Refers to a pressure level that is lower than atmospheric pressure, typically measured as less than one atmosphere.

Vane passing syndrome: Cavitation caused by insufficient clearance between the impeller and the cutwater, leading to operational issues.

Vane pump (hydraulic): A positive displacement pump that utilizes vanes mounted on a circular rotor within a cavity. The offset between the two circles creates eccentricity, enabling fluid movement.

Vaporize: The transformation of a fluid from a liquid state to a gaseous state.

Vapor pressure: The pressure at which a liquid starts to vaporize within a given chamber or environment.

Variable speed motor: A motor that allows for adjustable speed control, enabling flow regulation within a system by modifying impeller speed.

VDMA: Stands for the German Engineering Federation (Verband Deutscher Maschinen- und Anlagenbau). It serves as the trade association for the German mechanical engineering industry.

Velocity: Typically refers to the speed of an object or fluid, including its directionality.

Velocity head: The energy possessed by a flowing fluid due to its kinetic energy. It is calculated using the equation (velocity)^2 / (2 * acceleration of gravity).

Vent: The act of removing air or gas from a mechanical system, ensuring proper operation and preventing air-related issues.

Venturi (Bernoulli’s law): A pipe with a constricted section in the middle, causing a decrease in pressure according to Bernoulli’s principle. It utilizes the principle of fluid flow to measure or control pressure differentials.

Vertical canned pump: A vertical pump design featuring a double casing consisting of an inner bowl and an outer barrel. The outer barrel compresses the liquid in the inner bowl under full discharge pressure.

Vertical pump: A pump configuration where the shaft is mounted vertically, often used in applications with space constraints or specific system requirements.

Vibration damping: The practice of reducing or minimizing vibrations in mechanical systems, particularly important in mechanical seal design to prevent leakage and ensure optimal performance.

Vibration spectrum: A graphical representation of vibration amplitude plotted against frequency. It helps identify the source or cause of excessive vibration levels in turbomachinery.

Viscosity: The measure of a fluid’s resistance to gradual deformation under shear or tensile stress. It determines the fluid’s ability to flow.

Viscous drag pump: A pump design that employs a flat impeller without vanes. The fluid is moved through the interaction between the impeller’s flat disk and the fluid’s viscosity.

Viton®: A brand name for an elastomer (fluorocarbon) manufactured by E.I. DuPont de Nemours, known for its resistance to heat, chemicals, and extreme environments.

Volute: A spiral-shaped container that houses the impeller in a pump. It collects and directs the flow of liquid discharged from the impeller.

Volute casing: A component that converts the kinetic energy of a fluid into pressure by utilizing the venturi effect.

Volute insert: An insert welded at the volute lip to modify the pump’s performance. This technology is employed to achieve capacity reductions in re-rated pumps.

Volute pump: A pump design where the casing is shaped like a volute (spiral). It can feature either a single lip or two lips.

Vortex: A swirling mass of liquid rotating around an imaginary axis. The flow pattern associated with vortexing is known as vertical flow.

Vortexing liquid: Refers to a liquid at the inlet that exhibits a vortex, which may draw air into the intake.

Vortex pump: A pump designed for applications involving a high concentration of solids within the fluid. It operates with a recessed impeller that is positioned outside the primary flow path.

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