Hydraulics Jargon Buster: F
FATIGUE: The weakening or deterioration of a material occurring when a repetitious or continuous application of stress causes strain which can lead to failure.
FEEDBACK: Part of a closed loop system which monitors back information about the condition under control for comparison.
FEEDBACK LOOP: Any closed circuit consisting of one or more forward elements and one or more feedback elements.
FILLER CAP: A mechanical device which provides an access for filling a reservoir or tank. Normally equipped with a fine screen to strain out dirt particles.
FILTER: A device, used to house a filter element, incorporated into a hydraulic system to remove contaminants from the hydraulic oil. See hydraulic filters.
FITTING: A connector or closure for fluid power lines and passages.
FLOAT SPOOL: A spool valve design which connects all ports to the tank (return) port, usually in a detented fourth position, allowing a hydraulic cylinder or hydraulic motor to “float”.
FLOW CHECKING: Other nomenclature “ball checking”, “lock-up”, “check-off”. Occurs when the male tip half valve closes during high flow conditions, such as when quickly lowering a heavy loader.
FLOW CONTROL VALVE: A type of hydraulic valve consisting of a needle valve and a check valve placed in close proximity in a common body. Flow control valves regulate the flow of hydraulic fluid.
FLOW CONTROL VALVE, NON-PRESSURE COMPENSATED: A valve used to cause a variable pressure drop in a fluid passage, thus potentially reducing the amount of fluid that may pass through the passage regardless of the pressure level at the inlet of the valve. Varying pressures at the inlet of the valve will change the flow capacity. Often fitted with a check valve that permits free flow of fluid in the opposite direction.
FLOW DEMAND: The amount of fluid movement in a hydraulic system that is required to perform a specific job or type of work.
FLOW DIVIDER: A mechanical device used to divide the fluid in a passage into two or more separate fluid streams. See hydraulic flow dividers.
FLOW RATE: The volume, mass or weight of a fluid passing through a given point in a given time. Flow rate is commonly measured in gallons per minute (gpm).
FLOW SWITCH: A digital device that opens or closes a contact when a pre-set flow passes over the sensing element.
FLOW, TURBULENT: A flow situation in which fluid particles move in a random matter.
FLOWMETER: An analogue device which indicates the volume of fluid passing through its interior passage. The output signal may be a visual one or a low level electrical signal.
FLUID FRICTION: Friction due to the viscosity of fluids. The measure of the resistance of flow of fluid in a passage, measured in psi (pounds per square inch) or other measures of pressure. Fluid friction results in increased fluid temperature and loss of work potential in the fluid power system.
FLUID MOTOR: A mechanical device that transforms the flow of pressurized fluid into rotary motion.
FLUID POWER: Energy transmitted and controlled through use of a pressurized fluid.
FLUID POWER SYSTEM: The transmission and control of power through the use of fluid pressure. A system of components that use a pressurized fluid to transfer energy (do work).
FLUID STABILITY: Resistance of a fluid to permanent changes in properties.
FLUID VELOCITY: The speed of fluid through a cross section expressed in length divided by time.
FIRE-RESISTANT FLUID: Hydraulic oil used especially in high temperature or hazardous applications.
FLOW, LAMINAR: A flow situation in which fluid moves in parallel laminar or layers.
FORCE: The measure of the result of pressurized fluid acting upon a chamber in a fluid power system. Normally the measure is in pounds and is most often used to state the force in pounds that will be available at the rod of a cylinder when acted upon by pressurized fluid from a fluid power system. The system of units normally used are square inches, pounds per square inch, and pounds.
FORCE MULTIPLICATION: The exponential increase in available power usually associated with tools and power transmission systems.
FOUR-WAY: A term used to describe a valve that has four ports, normally a pressure (inlet) port, a return (tank) port, an `A’ (`1′) work port and a `B’ (`2′) work port. Used to change direction of a cylinder or other output device.
FOUR-WAY SPOOL VALVE: A spool valve that allows the reversal of hydraulic fluid flow. A four-way spool valve has five ports.
FOUR-WAY VALVE, MANUALLY & DIRECT OPERATED: A valve having a four way functional capability that may be manually activated to directly control the operating spool. Movement of the spool from one extreme end to the other extreme end reverses the flow paths of the ports. See FOUR-WAY.
FOUR-WAY VALVE, PROPORTIONAL CONTROL & DIRECT OPERATED: A valve having a four way functional capability that may be proportionately actuated by a solenoid to control the operating spool in infinite resolution. Movement of the spool from extreme end to extreme end completely reverses the flow paths of the ports. See FOUR WAY.
FOUR-WAY VALVE, SOLENOID & DIRECT OPERATED: A valve having a four way functional capability that may be solenoid activated to directly control the operating spool. Movement of the spool from extreme end to extreme end reverses the flow paths of the ports. See FOUR WAY.
FOUR-WAY VALVE, SOLENOID & PILOT OPERATED: A valve having a four way functional capability that may be solenoid activated to directly control the operating spool which then controls a secondary, larger spool. Movement of the secondary spool from one extreme end to the other extreme end reverses the flow paths of the ports. See FOUR WAY.
FREQUENCY: The number of times a given action occurs in a unit of time.
FRONT CONNECTED: The case where piping connections are on normally exposed surfaces of hydraulic components.
FULL FLOW: A filter in which all the fluid must pass through the filter element or medium.
FULL-FLUID-FILM LUBRICATION: Presence of a continuous lubricating film sufficient to completely separate two surfaces.