Glossary of Compressed Air Terms :: R :: Glossary Index A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Radial compressor A compressor belonging to the group of dynamic compressors. Characterized by radial flow. (Centrifugal) Rebound The extension of an air actuator beyond its design height. Receivers Tanks used for the storage of air discharged from compressors. They serve also to damp discharge line pulsations. Reciprocating compressors Machines in which the compressing element is a piston having a reciprocating motion in a cylinder. Recovery pressure Is that pressure of either motive fluid or discharge at which an ejector returns to stable operation following a period of unstable operation due to having previously reached the breaking pressure. There are two recovery pressures, one for motive fluid and one for the discharge pressure. Reduced pressure Ratio of the pressure of a gas to its critical pressure, in like units. Reduced temperature Is the ratio in absolute units of the actual gas temperature to the critical temperature. Refrigerant Media of heat transfer in a refrigeration unit. R12 and R22 are commonly used refrigerants. Refrigeration dryer A device consisting of a heat transfer system, a moisture elimination system and a refrigeration system designed to improve the quality of the air and reduce the temperature of the air. Regeneration The process of desiccants being regenerated by water being driven off the desiccant. Hot air or gas passes through the desiccant bed, heating it. As a result, the partial pressure of the water vapor becomes higher than that in the regenerating air. Water is therefore released from the desiccant and carried away with the air stream (purge air) until a new state of equilibrium is reached. Regulator An automatic or manual device designed to control pressure, flow or temperature. Reheaters Heat exchangers for raising the temperature of compressed air to increase its volume. Relative clearance volume The ratio of clearance volume to the volume swept by the compressing element. Relative humidity The ratio of the actual water-vapor partial pressure to its saturation pressure at the same temperature. (considered only with atmospheric air). Relative vapor pressure The ratio of the vapor pressure to the saturated vapor pressure at the temperature considered. Relief valve A spring loaded pressure relief valve actuated by the static pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over the opening pressure. Required capacity Cubic feet per minute (cfm) of air required at the inlet to the distribution system. Reversible process is an ideal process that may be stopped and made to retrace its steps and restore to the systems or surroundings all work and heat previously removed. It is frictionless. Reynold's number A dimensionless flow parameter, ( Jnr/m), in which J is a significant dimension, often a diameter, n is the fluid velocity, r is mass density, and m is dynamic viscosity, all in consistent units. Rings Circular metallic elements that ride in the grooves of a piston and provide compression sealing during combustion. Also used to spread oil for lubrication. Ring sticking freezing of a piston ring in its groove in a piston engine or reciprocating compressor due to heavy deposits in the piston ring zone. Rock drill A pneumatic percussive drill designed as a boring tool. Rolling element A type of journal bearing in centrifugal air compressors. Rotary actuator A pneumatic device with a rotary output. Typically of a vane or rack-and-pinion construction. Rotary blowers A compressor belonging to the group of displacement rotary compressors, a type of valve less displacement machine. Also referred to as "Roots blower". Rotary compressors Machines in which compression is effected by the positive action of rotating elements. Rotary sliding vane compressors Machines in which axial vanes slide radially in an eccentrically mounted rotor. Rotor The rotating element of a machine and, in the case of a compressor, is composed of the impeller (impellers) and shaft, and may include shaft sleeves and a thrust balancing device. Rust prevention test (turbine oils) -- a test for determining the ability of an oil to aid in preventing the rusting of ferrous parts in the presence of water. Glossary Index A B C D E F G H I J K L M N O P Q R S T U V W X Y Z