Glossary and index of fluid power principles and components 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.

FERRULE
A metal cylinder placed over a hose end to affix the fitting to the hose.

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 mechanical device used to house a filter element. See FILTER ELEMENT.

FILTER ELEMENT
A series of wire or fabric meshes which are bonded together by caps or perforated cylinders and are fitted into hydraulic system passages to strain fine particles and silt from fluid passed through the passage.

FITTING
A mechanical device used to attach two pieces of tubing/piping together or to attach a piece of tubing/pipe to a component.

FLOODED
A condition where the pump inlet is charged by placing the reservoir oil level above the pump inlet port.

FLAT SPOTS
Flat areas on the surface of cured hose caused by deformation during vulcanization.

FLOW CONTROL VALVE, PRESSURE COMPENSATED
A valve used to cause a variable pressure drop in a fluid passage, thus reducing the amount of fluid that may pass through the passage regardless of the pressure level at the inlet of the valve. Often fitted with a check valve that permits free flow of fluid in the opposite direction.

FLOW CONTROL VALVE, NONPRESSURE 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 DIVIDER
A mechanical device used to divide the fluid in a passage into two or more separate fluid streams.

FLOW RATE
The volume, mass, or weight of a fluid passing through any conductor per unit of time.

FLOW SWITCH
A digital device that opens or closes a contact when a preset flow passes over the sensing element. Normally mounted in a fluid flow passage with a paddle or want perpendicular to the fluid stream.

FLOWMETER
An analog 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
A media used in a fluid power system for transfer of energy (work). See FLUID POWER SYSTEM.

FLUID FRICTION
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 Injection Injury
Fluid injection also known as hydraulic injection can be defined as the puncturing of the epidermis by a jet of a fluid under pressure.

FLUID MOTOR
A mechanical device that transforms the flow of pressurized fluid into rotary motion.

FLUID POWER SYSTEM
The term used to describe a system of components that use a pressurized fluid to transfer energy (do work).

FLUID VELOCITY
The speed of fluid through a cross section expressed in length divided by time.

FOLLOW VALVE
A control valve which ports oil to an actuator so the resulting output motion is proportional to the input motion to the valve.

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.

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 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 extreme end to 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 extreme end to extreme end reverses the flow paths of the ports. See FOUR WAY.

FREE LENGTH
The lineal measurement of hose between fittings or couplings.

FREQUENCY
The number of times an action such as vibration or flexure occurs in a unit of time.

FREQUENCY BANDS
A division of the audible range of frequencies into sub-groups for detailed analysis of sound.

FREQUENCY RESPONSE ANALYSIS
A control system analysis which by introducing a varying rhythmic change (like alternating current) into a process or control unit observes what effect these changes have on the output. Since the information determines how a system or control unit will react, it is possible to use this method of analysis to predict what the addition of new equipment will mean to an operation.

FRONT CONNECTED
A condition wherein 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.