Boiler glossary

Boiler glossary V


V2M8 BOILER -- Top fired water tube boiler.
V2M9 BOILER -- A vertical two-drum dropped-furnace water tube boiler.
VACUUM AUGMENTER -- An air ejector placed in a steam condenser to produce a higher degree of vacuum than is obtainable by the use of an air-pump alone.
VACUUM PHOTOCELL -- High-vacuum photoemissive cell in which anode current equals total photoemission currents, so that strict proportionality between current and incident illumination is obtained.
VALVE BOUNCE -- The unintended opening of an engine valve due to inadequate rigidity of various parts in the valve gear. The deflected parts allow the valve to seat too early and when their strain energy is released, the valve opens again. This bounce causes valve breakage, seat wear, and irregular function.
VALVE DIAGRAM -- For a steam-engine slide-valve, a graphical method of correlating the throw and angle of advance of the eccentric, the lead and laps of the valve, and the points of admission, cut-off, compression, and release. The Bilgram, the Reulesux and the Zeunet valve diagrams are examples of the method.
VALVE-GEAR -- The linkage by which the valves of an engine derive their motion and timing from the crankshaft rotations. All steamships have a valve-gear although Stephenson named his valve-gear a link-motion.
VANE PUMP -- A type of pump used, e.g., as a vacuum or oil pump or as a compressor, in which a slotted rotor is mounted eccentrically in a circular stator (or a similar geometrical arrangement), and vanes sliding in the rotor slots divide the crescent-shaped fluid space into variable volumes.
VAPORIZATION -- The process of a solid or liquid becoming a gas.
VAPOR PRESSURE -- The pressure exerted by a vapor, either by itself or in a mixture of gases. The term is often taken to mean saturated vapor pressure, which is the vapor pressure of a vapor in contact with its liquid form. The saturated vapor pressure increases with rise of temperature.
VELOX BOILER -- A forced circulation boiler in which very high rates of heat release and heat transfer are obtained by the use of a supercharged furnace and high gas velocities, resulting in exceptionally low unit weight and high efficiency.
VENTURI METER -- One in which flow rate is measured in terms of pressure dropp across a venturi, or tapered throat, in a pipe.
VISCOSITY -- The degree to which a fluid resists flow under an applied force.
VOLATILE -- A volatile substance is one that is capable of being evaporated or changed to a vapor at a relatively low temperature.