ADYABATIC: Compression or expansion of a gas without heat gain or loss.
ACTUATOR (Driving element): Pneumatic device that applies power; for example, a cylinder or air motor.
INTERCOOLING: The process of lowering (removing) the temperature between stages in multi-stage compression.
AFTERCOOLING: The removal of heat generated in the air after the compression cycle.
ATMOSPHERIC PRESSURE: The absolute pressure of the atmosphere at the measurement location (ISO 3857/1).
PRESSURE REGULATOR: A device that reduces and maintains the system pressure at a desired level.
PRESSURE VESSEL (TANK): A container where compressed air is stored.
COMPRESSION RATIO: The ratio between the absolute discharge pressure and the absolute suction pressure.
AMBIENT TEMPERATURE: The temperature of the environment in which a device operates.
DEW POINT: The temperature at which air is fully saturated with water vapor at a given pressure.
MULTI-STAGE COMPRESSION: The process of increasing pressure from suction to final pressure in multiple stages with cooling applied between stages.
DISPLACEMENT: The volume of air moved by the first stage of a compressor or similar device in a unit of time.
SAFETY VALVE: A device that limits system pressure to a specified maximum and vents air to the atmosphere until pressure decreases when the limit is exceeded.
FILTER: An element that removes foreign particles and substances from the working environment.
ISOTHERMAL: Compression or expansion performed without a change in temperature.
RELATIVE HUMIDITY: The ratio of the amount of water vapor present in air at a certain pressure, temperature, and volume to the maximum amount that air can hold under the same conditions; expressed as a percentage (%).
STAGE COMPRESSION RATIO: The compression ratio of any stage in a multi-stage compressor. (Measured pressure before the intercooler.)
CLOSED LOOP SYSTEM: A closed compressed air circuit where air exhausted from actuators is returned to the compressor suction.
COMPRESSOR: A device that enables gas flow against opposing pressure; it converts mechanical power and motion into pneumatic fluid power.
COMPRESSOR CAPACITY: The ratio of actual air volume measured at discharge to the suction volume of the compressor. Usually specified as Free Air Delivery (FAD).
COMPRESSOR REGULATOR: A device installed to control compressor capacity (output volume).
DRIER: A device used to reduce the amount of water vapor in compressed air.
GAUGE PRESSURE: Measurement relative to atmospheric pressure (atmospheric pressure indicated as zero; measurements start from this point). Unless otherwise specified, all atm. and bar units are given as gauge pressure (ISO 3857/1).
ABSOLUTE PRESSURE: Pressure based on absolute zero, i.e., absolute vacuum. It equals atmospheric pressure plus gauge pressure (ISO 3857/1).
ABSOLUTE TEMPERATURE: Temperature measurement starting from absolute zero (ISO 3857/1).
SPECIFIC POWER CONSUMPTION: The drive shaft power required per unit compressor capacity (JOULES / LITER = kW\*s/m3).
PULSATION ABSORBER: A vessel installed at compressor suction or discharge to prevent pulsations and compressor resonance.
SEPARATOR: A liquid separator element that removes liquid from compressed air.
FREE AIR: Air at atmospheric conditions at compressor suction that has not yet been affected by the compressor. Compressor capacity or air tool consumption is always specified on this basis.
STANDARD REFERENCE ATMOSPHERE: A standard reference atmosphere used to reduce specifications and test measurements from different atmospheres. (ISO R558). In the compressor industry: 1000 mBar, 20°C, 65% relative humidity (ISO 2787); in pneumatics: 1013 mBar, 20°C, 65% relative humidity (ISO R554); in petrochemical and aerospace industries (ISO 5024): 1013 mBar, 15°C, and dry sea level reference atmosphere.
SINGLE-STAGE COMPRESSION: Compression from suction pressure to final pressure in a single stage.
THERMAL PROTECTOR: A protective device placed at the hottest point of a compressor to guard against excessive temperatures.
TOTAL STAGE COMPRESSION RATIO: The compression ratio at any stage of a multi-stage compressor. Measured in absolute pressure units (ISO 3857/2). Pressure is measured after the intercooler and separator.
VOLUMETRIC EFFICIENCY: The ratio of free air volume compressed by the compressor to the suction volume (displacement), expressed as a percentage (%). The water vapor content in air may be considered in precise measurements (ISO 3857/2).
LUBRICATOR: A device that supplies a controlled amount of lubricating oil to the working environment.
CONDENSATE: The liquid formed from water vapor in compressed air due to temperature drop or pressure increase.
RING-TYPE MAIN PIPELINE: A main pipeline in a compressor system that forms a closed loop, starting and ending in a ring shape. This allows each consumer to receive compressed air from two directions.