VACUUM
Negative pressure, when a gasket or seal is used to prevent the passage of external media or air into the system.
VALVE BODY
The part of a two-piece valve that houses the internal workings of the valve. The flanges that attach the valve to a pipeline are also part of the body.
VALVE BONNET
The part of a two-piece valve that attaches to the valve body. It houses the stuffing box and provides support to guide the valve stem.
VALVE STEM
See "Stem".
VHAP
Abbreviation for "Volatile Hazardous Air Pollutant".
VIBRATION
The ability of a flexible connector to absorb mechanical oscillations in the system.
VISCOSITY
A manifestation of internal friction opposed to mobility. The property of fluids and plastic solids by which they resist an instantaneous change of shape, i.e., resistant to flow.
VOC
Abbreviation for "Volatile Organic Compound".
VOLUME SWELL
Increase in physical size caused by the swelling action of a liquid.
VOLUTE
The internal area (housing) of a centrifugal pump where the fluid comes in contact with the impeller.
VULCANIZATION
An irreversible process during which a rubber compound, through a change in its chemical structure becomes: 1) less plastic, and 2) more resistant to swelling by organic liquids; and elastic properties are conferred, improved or extended over a greater range of temperature.
VULCANIZED SPLICE
A splice that is bonded with heat and pressure.