Applied Product Catalog 2017 2018 Page i48 Technical Reference

i48 Call your local Applied service center to order at 1-866-351-3464 or visit us online at SEQUENCE - The order of a series of operations or movements. To divert flow to accomplish a subsequent operation or movement. SEQUENCE VALVE - A pressure operated valve which diverts flow to a secondary actuator while holding pressure on the primary actuator at a predetermined minimum value after the primary actuator completes its travel. SERVO MECHANISM - A mechanism subjected to the action of a controlling device which will operate as if it were directly actuated by the controlling device, but capable of supplying power output many times that of the controlling device, this power being derived from an external and independent source. SERVO VALVE - A valve which controls the direction and quantity of fluid flow in proportion to an input signal. A follow valve. SIGNAL - A command or indication of a desired position or velocity. SINGLE ACTING CYLINDER - A cylinder in which hydraulic energy can produce thrust or motion in only one direction. (Can be spring or gravity returned.) SKIVING - Cutting, splitting or paring away the outer layer of a flexible hose. SLIP - Internal leakage of hydraulic fluid. SPOOL - A term loosely applied to almost any moving cylindrically shaped part of a hydraulic component which moves to direct flow through the component. STRAINER - A coarse filter. STROKE - The length of travel of a piston or plunger. To change the displacement of a variable displacement pump or motor. SUBPLATE - An auxiliary mounting device for a hydraulic component providing a means of connecting piping to the component. SUCTION LINE - The hydraulic line connecting the pump inlet port to the reservoir. SUPERCHARGE - (See Charge). SURGE - A momentary rise of pressure in a circuit. SUS (Saybolt Universal Seconds) - A measure of viscosity, the time required for a given fluid to flow through a standard orifice. SWASH PLATE - A stationary canted plate in an axial type piston pump or motor which causes the pistons to reciprocate as the cylinder barrel rotates. TANK - The reservoir. THROTTLE - To permit passing of a restricted flow. May control flow rate or create a deliberate pressure drop. TORQUE - A rotary force. The output torque of a fluid motor is usually expressed in pound-inches (lb-in) or Newton-Meters (Nm). TORQUE CONVERTER - A rotary fluid coupling that is capable of multiplying torque. TORQUE MOTOR - An electromagnetic device consisting of coils and the proper magnetic circuit to provide actuation of a spring restrained armature, either rotary or translatory. TURBINE - A rotary device that is actuated by the impact of moving fluid against blades or vanes. TURBULENT FLOW (TURBULENCE) - A condition where the fluid particles move in random paths rather than in continuous parallel paths. TWO-WAY VALVE - A directional control valve with two flow paths. UNLOAD - To release flow (usually directly to the reservoir), to prevent pressure being imposed on the system or portion of the system. UNLOADING VALVE - A valve which bypasses flow to a tank when a set pressure is maintained on its pilot port. VACUUM - The absence of pressure. A perfect vacuum is the total absence of pressure; a partial vacuum is some condition less than atmospheric pressure. Measured in inches of Mercury (in.Hg) with the zero point equal to atmospheric pressure. VALVE - A device which controls fluid flow direction pressure, or flow rate. VAPOR PRESSURE - The pressure at which the liquid and gaseous phases of a fluid are in equilibrium. VELOCITY - The speed of flow through a hydraulic line. Expressed in feet per second (fps) or meters per second (m/s). The speed of a rotating component measured in revolutions per minute (rpm or min-1). VENT - To permit opening of a pressure control valve by opening its pilot port (vent connection) to atmospheric pressure. An air breathing device on a fluid reservoir. VISCOSITY - A measure of the internal friction or the resistance of a fluid to flow. VISCOSITY INDEX - A measure of the viscosity-temperature characteristics of a fluid as referred to that of two arbitrary reference fluids. VOLUME - The size of a space or chamber in cubic units. Loosely applied to the output of a pump in gallons per minute (gpm). WORK - Exerting a force through a definite distance. Work is measured in units of force multiplied by distance; for example, pound-feet or joule (1 J = 1 Nm). Fluid Power Glossary

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