Applied Product Catalog 2016 2017 Page i47 Applied Product Catalog 2016/2017

Fluid Power Glossary Industrial Supplies and Expertise i47 MANUAL CONTROL - A control actuated by the operator, regardless of the means of actuation. Example: Lever or foot pedal control for directional valves. MANUAL OVERRIDE - A means of manually actuating an automatically- controlled device. MECHANICAL CONTROL - Any control actuated by linkages, gears, screws, cams or other mechanical elements. METER - To regulate the amount or rate of fluid flow. METER-IN - To regulate the amount of fluid flow into an actuator or system. METER-OUT - To regulate the flow of discharge fluid from an actuator or system. MICRON () - Size of a particle one millionth of a meter. MICRON RATING - The size of the particles a filter will remove. MOTOR - A rotary motion device which changes hydraulic energy into mechanical energy; a rotary actuator. NEWTON METER (Nm) - Metric unit of measure representing force. NPT - National Pipe Taper (requires pipe sealant). NPTF - National Pipe Taper Fuel or Dry Seal Pipe Threads (may not require pipe sealant). OPEN CENTER - A condition where pump delivery circulates freely to tank in the center or neutral position. ORIFICE - A restriction, the length of which is small in respect to its cross-sectional dimensions. OXIDATION - The chemical reaction of elements with oxygen which cause corrosion or deterioration. PASCAL - Unit of pressure in metric system, usually expressed in kPa (kilopascals). 1 kPa = 0.01 bar = 0.145 psi. PASSAGE - A fluid conducting path which lies within or passes through a component. PI () - Ratio of circumference of circle to diameter. Numerically expressed as approximately 3.1416. PILOT PRESSURE - Auxiliary pressure used to actuate or control hydraulic or pneumatic components. PILOT VALVE - An auxiliary valve to control the operation of another valve. The controlling stage of a 2-stage valve. PISTON - A cylindrically shaped part which fits within a cylinder and transmits or receives motion by means of a connecting rod. PLUNGER - A cylindrically shaped part with only one diameter that is used to transmit thrust (also called a ram). POPPET - That part of certain valves which prevents flow when it closes against a seat. PORT - An internal or external terminus of a passage in a component. POSITIVE DISPLACEMENT - A characteristic of a pump or motor which has the inlet positively sealed from the outlet so that fluid cannot recirculate in the pump or motor. POTENTIAL ENERGY - The energy level change which results when an object is raised to a new height. POTENTIOMETER - A control element in the servo-system which measures and controls electrical potential. POWER - Work per unit of time. Measured in horsepower (hp) or watts. ppm (parts per million) - Unit of measure representing the number of particles in a given body. PRECHARGE PRESSURE - The pressure of compressed gas in an accumulator prior to the admission of liquid. PRESSURE - Force per unit area; usually expressed in psi, bar, or kPa. PRESSURE DIFFERENTIAL (PRESSURE DROP) - The difference in pressure between any two points of a system or a component. PRESSURE LINE - The line carrying the fluid from the pump outlet to the pressurized port of the actuator. PRESSURE OVERRIDE - The difference between the cracking pressure and the full flow pressure of a valve. PRESSURE REDUCING VALVE - A valve which limits the maximum pressure at its outlet regardless of the inlet pressure. psia (pounds per square inch absolute) - See Absolute Pressure. psig (pounds per square inch gauge) - See Gauge Pressure. PUMP - A device which converts mechanical force and motion into hydraulic fluid flow. RAM - A single acting cylinder with a plunger rather than a piston and rod. The plunger in a ram type cylinder. RECIPROCATION - Back and forth straight line motion or oscillation. RELIEF VALVE - A pressure operated valve which bypasses pump delivery to the reservoir, limiting system pressure to a predetermined maximum value. REPLENISH - To add fluid to maintain a full hydraulic system. RESERVOIR - A container for storage of liquid in a fluid power system. RESTRICTION - A reduced cross-sectional area in a line or passage which produces a pressure drop. RETURN LINE - A line used to carry exhaust fluid from the actuator back to a tank. REVERSING VALVE - A four-way directional valve used to reverse a double acting cylinder or reversible motor. ROTARY ACTUATOR - A device for converting hydraulic energy into rotary motion. SAE - The Society of Automotive Engineers. SAE O-Ring - Refers to a style of threaded connection that employs straight thread to secure the fitting and an o-ring to provide sealing. This style of connection is very popular for use in hydraulic systems and can be removed and reinstalled numerous times without damaging the sealing ability of the connection. Tapered pipe thread is actually damaged to make a fluid tight seal. Vibration and repeated connection of tapered pipe threaded connections will always result in leaks. An o-ring style or a 37 JIC flared connection are the best choices in preventing leaks. scfm (standard cubic feet per minute) - Unit of measure representing volume of gas flow.

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