Compressed Air Glossary: E to L

Efficiency Compression: The ratio of the theoretical work requirement to the actual work required to be performed on the gas within the cylinder.

Expanders: Engines or turbines in which gas expands, does work & undergoes a drop in temperature.

Filters: Devices that removes or separate the unwanted liquid & dust from air before it enters the compressor.

Fluidics: The general subject of instruments and controls dependent upon low rate flow of air or gas at low pressure as the operating medium.

Gas Bearings: These are load carrying machine which allows some movement in which the lubricant is air or some other gas.

Guide Vane: An adjustable stationary element that helps direct the flowing medium to the inlet of an impeller.

Gauge Pressure: Pressure determined by instruments or gauges.

Head, Adiabatic: The energy in foot pounds required to compress adiabatically and to deliver one pound of a given gas from one pressure level to another.

High Pressure air: Air which is compressed above 150 PSI.

Humidity Relative: The ratio of the partial pressure of the vapour to the vapour saturation pressure at the dry bulb temperature of the mixture.

Inlet Pressure: The pressure at the inlet flange of the compressor, measured in PSIG.

Intercooling: The removal of heat from gas or air between compressor stages.

Inducer: A curved inlet section on impeller.

Intercoolers: heat exchanger device which removes the heat of compression between the stages of compressor.

kPa: Equal to 1000 Pa.

Liquid Piston: A liquid piston compressor is a rotary compressor in which a vaned rotor revolves in an elliptical casing, with the rotor spaces sealed by a ring of liquid rotating with it inside the casing.

Load Time: Time period from when a compressor loads until it unloads.

Load/Unload Control: Control method that allows the compressor to run at full-load or at no load while the driver remains at a constant speed.

Compressed Air Glossary: A to D

Precise information on compressed air system terms is always valuable. Glossary of terms for people who work with compressed air solution.

Absolute Pressure: The total pressure measured from absolute zero.

Ambient Air: Air or Temperature surrounding you.

Absolute Temperature: Temperature calculated from absolute zero on the Kelvin scale or on Rankine scale.

Absolute Zero: Temperature at lowest possible point. The temperature at which kinetic energy is of atoms & molecule are at minimal.

Aftercooler: The heat exchanger unit which helps cooling the air or gas discharged from compressor before it enters the system.

Actual Capacity: Quantity of gas actually compressed & delivered to the discharge system at given rated speed of machine & under given pressure conditions.

Adiabatic Compression: A type of compression where no heat is transferred to or from the gas during the compression process.

Air cooled compressor: Compressors are cooled by atmospheric air by circulating them around the cylinders or casings.

Air Receivers: A vessel designed to store the compressed air & to permit pressure to be stable in the system.

Air Dryer: Devices which will help absorb water vapour from compressed air.

Automatic Sequencer: A device which operates compressors in sequence according to a programme schedule.

Atmospheric Pressure: The pressure exerted by the atmosphere.

Bar: A unit of pressure used in industry field, which is approximately equal to atmospheric pressure.

Base Plate: A metallic structure on which a compressor or other machine is mounted.

Booster Compressor: A machine which helps compressing air or gas from an initial pressure to much higher pressure.

Boss hose fitting: Threaded fitting which connects hose from compressor or extended hose for flow of gas.

Capacity: The amount of air flow delivered from compressor under specific conditions & is usually expressed in cubic feet per minute (CFM).

Casing: The pressure containing stationary element that encloses the rotor & associated internal components of the compressors, and it includes integral inlet and discharge corrections.

Check Valve: A mechanical device which allows the flow of liquid or gas in one direction.

Condensate: Liquid formed in compressor from water vapour due to decrease in temperature &/or increase in pressure.

CFM: Volumetric air flow rate.

Compression Ratio: The ratio of the discharged pressure to the inlet pressure.

Constant Speed Control: A system which runs continuously & matches air supply to demand, by varying compressor load.

Cycle: The series of steps that a compressor performs.

Cut In/Out Pressure: A setting on a pressure discharge used to either load or unload the compressor on a content speed application to either start or stop the machine.

Compressibility: A factor expressing the deviation of gas from the laws of hydraulics.

Compression, Adiabatic: A compression where no heat is transferred to or from the gas during the compression process.

Compression, Isothermal: A compression in which the temperature remains constant. For reversible process the equation PV is constant for perfect gases.

Compression, Polytropic: A graphical relationship between the pressure & volume for various values of specific-heat ratio in a compressor equation pVⁿ = K.

Compression Ratio: The ratio of the discharged pressure to the inlet pressure.

Critical Pressure: It is the saturation pressure at the critical temperature.

Critical Temperature: The highest temperature at which well defined vapor & liquid state exist.

Dew Point: The temperature at which the air gets saturated & changes from vapour to liquid at a given pressure.

Dew Point Suppression: Temperature below ambient.

Desiccant: An adsorption type material which attracts & remove water vapour from the air.

Discharge Pressure: It is the pressure generated on the output side of a gas compressor.

Discharge Temperature: The temperature existing at the discharged port of the compressor.

Dynamic-type Compressors: Air or gas compressed by rotating vanes or impellers.