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Valve

Valve: Globe valve, stem sealed by bellows

The term “valve” stems from the Latin “valva”, which means "moving part of a door".

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Vane

The vanes of a centrifugal pump are either permanently fixed to or fitted in the impeller or diffuser ...

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Vane angle

The vane angle βs determines the fluid flow direction in an impeller (also see Vane, Vane cascade).

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Vane cascade

A vane cascade consists of regularly arranged vane profiles (see Flow profile) along a straight line ...

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Vapour pressure

Vapour pressure (pD) is a substance- and temperature-dependent gas pressure in a multiphase system.

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Variable pitch vane

A variable pitch vane is a vane which can be turned during operation to change its pitch. It plays an ...

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V-belt drive

The V-belt drive is a belt drive that moves smoothly and exhibits minimal slip. The endless belt is ...

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Velocity

The velocity of a body is defined as the distance it travels in a period of time. In fluid systems, ...

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Velocity head

Velocity head is the kinetic portion of the head. In accordance with EN 12723, it is the kinetic ...

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Velocity of pressure wave propagation

The pressure wave propagation velocity is the velocity at which the pressure wave moves in the fluid ...

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Velocity of sound

Velocity of sound (a), or, to use the correct physical term, pressure wave propagation velocity, is ...

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Velocity triangle

The velocity triangle is the vectorial representation of kinematic movement. A vector is a ...

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Venting

Venting is a necessary process which serves to release accumulations of air from pressurised water ...

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Venturi nozzle

A Venturi nozzle that meets the relevant standards is also referred to as a standard Venturi nozzle.

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Venturi tube

Venturi tube: General design

The Venturi tube is a differential pressure flow meter which, in terms of its geometric dimensions, ...

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Vent valve

The vent valve is a device installed to prevent negative pressure (e. g. as a result of surge ...

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Vertical pump

A vertical pump is a centrifugal pump with a vertical shaft, for example, a condensate pump or a ...

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Vertical shaft submersible pump

A vertical shaft submersible pump is a single-stage submersible pump. The vertical, radially split, ...

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Vibration

Vibration of a physical quantity is said to occur when its time profile shows regular or irregular ...

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VIK motor

The acronym VIK stands for "Verband Industrieller Kraftwerksbetreiber" (German Energy and Power ...

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Viscosity

Viscosity is the property of a fluid to resist the relative displacement of adjoining layers ...

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Visualisation

The term "visualisation" refers to the graphical representation of data or relationships provided by ...

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Voltage converter

A voltage converter is a device that converts a specific voltage into a different one, whereby the ...

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Voltage drop

The term voltage drop as used in electrical engineering describes a difference in potential between ...

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Volume flow coefficient

The volume flow coefficient is a characteristic coefficient and is also referred to as the flow ...

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Volume flow rate

The term volume flow rate describes the volume of a fluid flowing through a cross-section over a ...

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Volute casing

The volute casing is designed to guide the flow out of the impeller in order to convert the fluid ...

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Volute casing pump

Volute casing pump: Design to EN 733

The volute casing pump is the most common type of centrifugal pump. Its characteristic feature is the ...

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Vortex

In fluid mechanics, vortices are the circular flows of a fluid and form as a result of different ...

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Vortex flow

The vortex flow exhibits rotational symmetry (see Fluid mechanics) with tangential components. For ...

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Vortex flow pump

Vortex flow pump is another term for torque flow pump. The latter must not be confused with the ...

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VSD

The abbreviation VSD stands for "variable speed drive" and describes a drive whose rotational speed ...

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