A part of this glossary has been extracted from the American Standard Glossary of Terms for of the publisher, The National Fluid Power Association.

ABSOLUTE TEMPERATUREThe temperature measured using absolute zero as a reference. Absolute zero is 273.16C or 459.69F.

ACCELERATIONTime rate of change of velocity.

ACCUMULATORA device for storing liquid under pressure. It usually consists of a chamber separated into a gas compartment and a liquid compartment by a piston or diaphragm. An accumulator also serves to smooth out pressure surges in a hydraulic system.

ACTUATORA device that converts fluid power into mechanical force and motion.

ADDITIVEA chemical compound or compounds added to a fluid to change its properties.

AIR, COMPRESSEDAir at any pressure greater than atmospheric pressure.

AMBIENTSurrounding, such as ambient air, meaning surrounding air.

BAROMETERAn instrument that measures atmospheric pressure.

BERNOULLIS PRINCIPLEIf a fluid flowing through a tube reaches a constriction, or narrowing of the tube, the velocity of the fluid flowing through the constriction increases and the pressure decreases.

BLEEDER, AIRA bleeder for the removal of air.

BOYLES LAWThe absolute pressure of a fixed mass of gas varies inversely as the volume, provided the temperature remains constant.

CAVITATIONA localized gaseous condition within a liquid stream that occurs where the pressure is reduced to the vapor pressure.

CELSIUSThe temperature scale using the freezing point of water as zero and the boiling point as 100, with 100 equal divisions between, called degrees. This scale was formerly known as the centigrade scale.

CENTRIFUGAL FORCEA force exerted on a rotating object in a direction outward from the center of rotation.

CHARLESS LAWIf the pressure is constant, the volume of dry gas varies directly with the absolute temperature.

CHEMICAL CHANGEA change that alters the composition of the molecules of a substance.

CIRCUITAn arrangement of intercon-nected component parts.

COMPRESSIBILITYThe change in volume of a unit volume of a fluid when it is subjected to a unit change of pressure.

COMPRESSORA device that converts mechanical force and motion into pneumatic fluid power.

COMPUTERA device capable of accepting information, applying prescribed processes to the information, and supplying the results of these processes.

CONDENSATIONThe change from a gaseous (or vapor) state to a liquid state.

CONTAMINANTDetrimental matter in a fluid.

CONTINUITY EQUATIONThe mass rate of fluid flow into any fixed space is equal to the mass flow rate out. Hence, the mass flow rate of fluid past all cross sections of a conduit is equal.

CONTROLA device used to regulate the function of a component or system.

CONTROL, CYLINDERA control in which a fluid cylinder is the actuating device.

CONTROL, ELECTRICA control actuated electrically.

CONTROL, HYDRAULICA control actuated by a liquid.

CONTROL, MANUALA control actuated by the operator.

CONTROL, MECHANICALA control actuated by linkages, gears, screws, cams, or other mechanical elements.

CONTROL, PNEUMATICA control actuated by air or other gas pressure.

CONTROL, SERVOA control actuated by a feedback system that compares the output with the reference signal and makes corrections to reduce the difference.

CONTROLS, PUMPControls applied to positive-displacement variable delivery pumps to adjust their volumetric output or direction of flow.

CONVERGENTThat which inclines and approaches nearer together, as the inner walls of a tube that is constricted.

COOLERA heat exchanger, which removes heat from a fluid.

COOLER, AFTERCOOLERA device that cools a gas after it has been compressed.

COOLER, INTERCOOLERA device that cools a gas between the compressive steps of a multiple stage compressor.

COOLER, PRECOOLERA device that cools a gas before it is compressed.

CORROSIONThe slow destruction of materials by chemical agents and electromechanical reactions.

CYCLEA single complete operation consisting of progressive phases starting and ending at the neutral position.

CYLINDERA device that converts fluid power into linear mechanical force and motion. It usually consists of a movable element, such as a piston and piston rod, plunger, or ram, operating within a cylindrical bore.

CYLINDER, CUSHIONEDA cylinder with a piston-assembly deceleration device at one of both ends of the stroke.

CYLINDER, DOUBLE-ACTINGA cylinder in which fluid force can be applied to the movable element in either direction.

CYLINDER, DOUBLE-RODA cylinder with a single piston and a piston rod extending from each end.

CYLINDER, DUAL-STROKEA cylinder combination that provides two working strokes.

CYLINDER, PISTONA cylinder in which the movable element has a greater cross-sectional area than the piston rod.

CYLINDER, PLUNGERA cylinder in which the movable element has the same cross-sectional area as the piston rod.

CYLINDER, SINGLE-ACTINGA cylinder in which the fluid force can be applied to the movable element in only one direction.

CYLINDER, SINGLE-RODA cylinder with a piston rod extending from one end.

CYLINDER, SPRING-RETURNA cylin-der in which a spring returns the piston assembly.

CYLINDER, TANDEMTwo or more cylinders with interconnected piston assemblies.

CYLINDER, TELESCOPINGA cylinder with nested multiple tubular rod segments which provide a long working stroke in a short retracted envelope.

DENSITYThe weight per unit volume of a substance.

DIAGRAM, COMBINATIONA drawing using a combination of graphical, cutaway, and pictorial symbols.

DIAGRAM, CUTAWAYA drawing show-ing principal internal parts of all components, controls, and actuating mechanisms, all inter-connecting lines and functions of individual components.

DIAGRAM, GRAPHICALA drawing or drawings showing each piece of apparatus including all interconnecting lines by approved standard symbols.

DIAGRAM, PICTORIALA drawing show-ing each component in its actual shape according to the manufacturers installation.

DIAPHRAGMA dividing membrane or thin partition.

DIFFUSERA duct of varying cross section designed to convert a high-speed gas flow into low-speed at an increased pressure.

DISPLACEMENTThe volume of fluid that can pass through a pump, motor, or cylinder in a single revolution or stroke.

DIVERGENTMoving away from each other, as the inner wall of a tube that flares outward.

EFFICIENCYThe ratio of the output power to the input power, generally expressed as a percentage.

ENERGYThe ability or capacity to do work.

EQUILIBRIUMA state of balance between opposing forces or actions.