FAHRENHEIT: The temperature scale using the freezing point as 32 and the boiling point as 212, with 180 equal divisions (degrees) between. FAIL: (1) The loss of control signal or power to a component. (2) The breakage or breakdown of a component or component part.

FATIGUE: The tendency of a material to break under repeated strain.

FEEDBACK: (1) A transfer of energy from the output circuit of a device back to its input. (2) Information about a process output which is communicated to the process input.

FEEDER: An electrical conductor or group of conductors between different generating or distributing units of a power system.

FEED HEATER: A heat transfer device that heats the feedwater before it goes to the boiler.

FEEDWATER: Water that meets the require-ments of Naval Ships Technical Manual, Chapter220, for use in a boiler.

FERROUS METAL: Metal with a high iron content.

FIELD WINDING. The coil used to provide the magnetizing force in motors and generators.

FILTER: A device through which gas or liquid is passed; dirt, dust, and other impurities are removed by the separating action.

FIRELINE: Section of piping and hose on discharge side of a proportioner leading to a fire location.

FIRE MAIN: The seawater line that provides firefighting and flushing water throughout the ship.

FIRING ORDER: The order in which the cylinders deliver their power stroke.

FIRING PRESSURE: The highest pressure reached in the cylinder during combustion.

FIRE TUBE BOILER: Boilers in which the gases of combustion pass through the tubes and heat the water surrounding them.

FLASHPOINT: The temperature at which a substance, such as an oil, will give off a vapor that will flash or burn momentarily when ignited.

FLEXIBLE COUPLING. A coupling that transmits rotary motion from one shaft to another while compensating for minor misalignment between the two units.

FLOOR PLATES: The removable deck plating of a fireroom or engine room aboard ship. Also called deck plates.

FLOWMETER: An instrument used to measure quantity or the flow rate of a fluid motion.

FLUID: A substance capable of flowing or conforming to the shape of its container (a liquid or gas or mixture thereof).

FLYWHEEL: A heavy wheel attached to the crankshaft. It stores up energy during the power event and releases it during the remaining events of the operating cycle.

FLYWEIGHT: A governor; weights which move and assume positions in accordance with the speed of rotation.

FOAM NOZZLE: A nozzle designed to entrain air and mix it with water and foam liquid to produce a foam blanket.

FOOT-POUND: (1) The amount of work accomplished when a force of 1 pound produces a displacement of 1 foot. (2) The amount of torque produced by 1 pound of effort applied at a radius of 1 foot.

FORCE: The action of one body on another tending to change the state of motion of the body acted upon. Force is usually expressed in pounds.

FORCE-BALANCE: An arrangement of control system components using a mechanical force as the feedback signal. The feedback applied force must null the forces acting on a balancedmechanism.

FORCED FEED LUBRICATION: A lubrica-tion system that uses a pump to maintain a constant pressure.

FREE FLOW: Flow which encounters negligible resistance.

FREQUENCY: The number of complete cycles per second (hertz) existing in any form of wave motion.

FRESH WATER: Water of relatively low dissolved solids content as compared to seawater. There are two types of shipboard fresh water: (1) feedwater (the low-pressure drains of the steam generator condensate system), and (2) potable water (supplied from either a shore water source or a shipboard distilling plant).

FRESHWATER SYSTEM: A piping system which supplies fresh water throughout the ship.

FRICTION: The action of one body or substance rubbing against another, such as fluid flowing against the walls of a pipe; the resistance to motion caused by this rubbing.

FRICTION PRESSURE DROP: The decrease in the pressure of a fluid flowing through a passage attributable to the friction between the fluid and the passage walls.

FUEL MIXTURE: A ratio of fuel and air.

FUEL OIL SERVICE TANKS: Tanks from which the fuel oil service pumps take suction for supplying diesel fuel oil to the engine. See DAY TANKS.

FUEL TRANSFER PUMP: A mechanical device used to transfer fuel from the tank to the injection pump.

FUEL VALVE: A valve admitting fuel to the combustion chamber. In a more general sense, this term may also apply to any manual or automatic valve controlling the flow or fuel.

FULCRUM: The pivot point of a lever.

FULL-FLOATING PISTON PIN: A piston pin free to turn in the piston boss of the connecting rod eye.

FULL-FLOW OIL FILTER: A type of oil filter through which all engine oil passes before entering the lubrication channels.