Tuesday, August 25, 2009

Compressed Air Glossary: M to S

Multicasing Compressor: When two or more compressors, each with a separate casing, are driven by a single motor or turbine, the combined unit is called a multicasing compressor.


Multistage Axial Compressor: A machine having two or more rows of muting vanes operating in series on a single rotor and in a single casing.


Multistage Compressors: Machines employing two or more stages.


Modulating Control: Compressor controls will run the compressor at varying loads to accommodate demand variations.


Off-Load: The compressor which is running & consuming power but is not delivering air.

On-Load: The compressor producing air, either at part load or full load.


Oil-free air: Compressed air produced by a compressor with no oil present in the compression cycle.


Oil Separator: A device that separates oil from the condensate.


OSHA Valve: Valve used to depressurize a system when pressure drop is noticed.


Packaged Air System: Self contained unit consisting of a compressor, a prime mover & various accessories.


Pascal (Pa): The SI derived unit of pressure.


Pressure Drop: A term used to describe the decrease in pressure from one point in a pipe or tube to another.


Pressure Regulator: A device used to decrease the incoming pressure to a lower level & maintains it irrespective to the changes in inlet pressure & outlet flow rate.


Prime Motor: A machine used to derive a compressor.


Particulates: Solid materials such as dust, rust, pollen, etc that is present in air stream.


PPM: Parts Per Million, measurement of the oil present in compressed air.


Receivers: Tanks used to store compressed air & help damp discharge line pulsations.


Reciprocating Compressor: It is a positive displacement compressor which is driven by a piston having a reciprocating motion in a cylinder.

Reduced Pressure: Ratio of actual pressure of a gas to its critical pressure.


Reheaters: Heat exchanger for increasing the temperature of compressed air to increase its volume.


Rotor: A rotating element in a machine & is composed of impeller & shaft.


Rotary Compressor: An air compressor using a rotary impeller driving air through a curved chamber to compress the air.


Regulator: An automatic or manual device designed to control pressure, flow or temperature.


Relief valve: A type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure.


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.


Safety Valve: A device that limits liquids & gas pressure by discharging some of the pressurized liquid or gas.


Safety Relief Valve: An automatic pressure relieving device actuated by the static pressure upstream of the device, which opens in proportion to the increase in pressure over the opening pressure.


Standard Air: Air at a temperature of 68 °F, a pressure of 14.70 psia and a relative humidity of 36 per cent (0.0750 density) (as per A.S.M.E. however in the gas industry the temperature of standard air is usually given as 60 °F.


SCFM: Standard cubic feet per minute.


Set Pressure: The gauge pressure at which a safety valve visibly and audibly opens or at setting which a relief valve discharges an unbroken stream of liquid.


Shaft: A rotating element part on which a rotating division is mounted & therefore helps transmits energy from the prime mover.


Surge Limit: It is the capacity below which the compressor operation becomes unstable.


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