Vane – A fixed or adjustable plate inserted in a gas or air stream used to change the direction of flow.
Vane control – A set of movable vanes in the inlet of a fan to provide regulation of airflow.
Vane guide – A set of stationary vanes to govern direction, velocity and distribution of air or gas flow.
Valve, manual gas shutoff – A manually operated valve in a gas line for the purpose of completely turning on or shutting off the gas supply.
Valve, manual oil shutoff – A manually operated valve in the oil line for the purpose of completely turning on or shutting off the oil supply to the burner.
Valve, manual reset safety shutoff – A manually opened, electronically latched, electrically operated safety shut-off valve designed to automatically shut off fuel when de-energized.
Valve, motor driven reset safety shutoff – An electrically operated safety shut-off valve designed to automatically shut off fuel flow upon being de-energized. The valve is opened and reset automatically by integral motor device only.
Valve, fuel control – An automatically or manually operated device consisting essentially of a regulating valve and an operating mechanism. It is used to regulate fuel flow and is usually in addition to the safety shut-off valve. Such valve may be of the automatic or manually opened type.
Vapor – The gaseous product of evaporation.
Vapor generator – A container of liquid, other than water, which is vaporized by the absorption of heat.
Vaporization – The change from liquid or solid phase to the vapor phase.
Velocity pressure – The measure of kinetic energy of a fluid.
Velocity thermocouple – (suction pyrometer) a device for measuring furnace gas temperature. It is comprised of a thermocouple, which has been recessed into an insulating shroud, and a suction device such as an eductor, which aspirates large volumes of furnace gas through the shroud and past the thermocouple. The high velocity of a gas ensures good convective heat transfer to the thermocouple and surrounding furnace. The velocity thermocouple represents the most accurate means to measure flue gas temperature. Bare thermocouples are unacceptable for this purpose, being in error often by more than 100o F due to radiation losses.
Vent – An opening in a vessel or other enclosed space for the removal of gas or vapor.
Vertical firing – An arrangement of a burner such that air and fuel are discharged into the furnace, in practically a vertical direction.
Viscosity – Measure of the internal friction of a fluid or its resistance to flow.
Volatile matter – Those products given off by a material as gas or vapor, determined by definite prescribed methods.
Volume of air – The number of cubic feet of air per minute expressed at fan outlet conditions.
Vortex – (1) The swirling motion of a liquid in a vessel at the entrance to a discharge nozzle. (2) The point in a cyclonic gas path where the two spirals change general direction by 180o.
Waste fuel – Any by-product fuel that is waste from a manufacturing process.
Waste heat – Sensible heat in non-combustible gases.
Water column – A vertical tubular member connected at its top and bottom to the steam and water space respectively to a boiler, to which the water gage, gage cocks, high and low water alarms and fuel cutoff may be connected.
Water gage – The gage glass and its fittings for attachment.
Water hammer – A sudden increase in pressure of water due to an instantaneous conversion or momentum to pressure.
Water level – The elevation of the surface of the water in a boiler.
Water tube – A tube in a boiler having the water and steam on the inside and heat applied to the outside.
Water vapor – A synonym for steam, usually used to denote steam of absolute low pressure.
Weep – A term usually applied to a minute leak in a boiler joint which forms droplets (or tears) of water very slowly.
Wet back – Baffle provided in a firetube boiler joining the furnace to the second pass to direct the products of combustion that is completely water-cooled.
Wet steam – Steam containing moisture.
Windbox – A chamber below the grate or surrounding a burner, thru which air under pressure is supplied for combustion of the fuel.
Windbox pressure – The static pressure in the windbox of a burner or stoker.