FAN – A machine consisting of a rotor and housing for moving air or gases at relatively low pressure differentials.
FAN PERFORMANCE – A measure of fan operation in terms of volume, total pressures, static pressures, speed, power input, mechanical and static efficiency, at a stated air density.
FAN PERFORMANCE CURVES – The graphical presentation of total pressure, static pressure, power input, mechanical and static efficiency as ordinates and the range of volumes as abscissa, all at constant speed and air density.
FEED PUMP – A pump that supplies water to a boiler.
FEEDWATER – Water introduced into a boiler during operation. It includes make-up and return condensate.
FEEDWATER TREATMENT – The treatment of boiler feed water by the addition of chemicals to prevent the formation of scale or to eliminate other objectionable characteristics.
FGR – Flue Gas Recirculation or the recirculation of flue gas with combustion air to reduce NOx emissions.
FILTER – Porous material through which fluids or fluid – and solid mixtures are passed to separate matter held in suspension.
FIN – A fin is an extended surface, a solid, experiencing energy transfer by conduction within its boundaries, as well as energy transfer with its surroundings by convection and/or radiation, used to enhance heat transfer by increasing surface area.
FIN TUBE – A tube with one or more fins.
FIRED PRESSURE VESSEL – A vessel containing a fluid under pressure exposed to heat from the combustion of fuel.
FIRETUBE – A type of boiler design in which combustion gases flow inside the tubes and water flows outside the tubes.
FIRING RATE CONTROL – A pressure temperature or flow controller which controls the firing rate of a burner according to the deviation from pressure or temperature set point. The system may be arranged to operate the burner on-off, high-low or in proportion to load demand.
FIXED CARBON – The carbonaceous residue less the ash remaining in the test container after the volatile matter has been driven off in making the proximate analysis of a solid fuel.
FLAME – A luminous body of burning gas or vapor.
FLAME DETECTOR – A device which indicates if a fuel (liquid, gaseous, or pulverized) is burning, or if ignition has been lost. The indication may be transmitted to a signal or to a control system.
FLAME PROPAGATION RATE – Speed of travel of ignition through a combustible mixture.
FLAME SAFEGUARD – A control that sequences the burner through several stages of operation to provide proper air purge, ignition, normal operation, and shutdown for safe operation.
FLAMMABILITY – Susceptibility to combustion.
FLASHING – The process of producing steam by discharging water into a region of pressure lower than the saturation pressure that corresponds to the water temperature
FLASH POINT – The lowest temperature at which, under specified conditions, fuel oil gives off enough vapor to flash into a momentary flame when ignited.
FLUE – A passage for products of combustion.
FLUE GAS – The gaseous product of combustion in the flue to the stack.
FOAMING – The continuous formation of bubbles which have sufficiently high surface tension to remain as bubbles beyond the disengaging surface.
FORCED CIRCULATION – The circulation of water in a boiler by mechanical means external to the boiler.
FORCED-DRAFT FAN – A fan supplying air under pressure to the fuel burning equipment.
FOULING – The accumulation of refuse in gas passages or on heat absorbing surfaces which results in undesirable restriction to the flow of gas or heat.
FM – Factory Mutual.
FREE ASH – Ash which is not included in the fixed ash.
FUEL – A substance containing combustible used for generating heat.
FUEL-AIR MIXTURE – Mixture of fuel and air.
FUEL-AIR RATIO – The ratio of the weight, or volume, of fuel to air.
FUEL OIL – A liquid fuel derived from petroleum or coal.
FUEL-TO-STEAM EFFICIENCY – The ratio of heat added to boiler feedwater to produce the output steam to the amount of energy inputted with fuel.
FURNACE – An enclosed space provided for the combustion of fuel.
FURNACE PRESSURE – Pressure occurring inside the combustion chamber; positive if greater than atmospheric, negative if less than atmospheric, and neutral if equal to atmospheric.
FURNACE VOLUME – The cubic contents of the furnace or combustion chamber.
FUSIBLE PLUG – A hollowed threaded plug having the hollowed portion filled with a low melting point material.