SCREW COMPRESSORS
Screw compressors are used for small scale compression, where the pressure requirement is low and where high efficiency is required.
A pressure ratio of 3.7 is typically achievable across one stage of a screw compressor (ie, a two stages screw compressor can compress atmospheric air to 13 bar(g).
Screw compressors have two rotors which fit together. One is machined with helical lobes (male) and the other is helically grooved (female). They rotate together in the compressor housing, which is shaped like a figure of eight. As the rotors turn they trap gas between them and the volume of the enclosed space decreases as the gas is pushed towards the outlet.
The diagrams below show a typical helical screw compressor and the process of compression. In this case the male rotor has four lobes and the female has six lobes.
This is how the compressor works stage by stage…..see the below figures…..
Stage Description
1 Gas at supply pressure is trapped between the rotating male and female rotors.
2-4 As the two rotors turn the volume between them progressively decreases, so the pressure of the
trapped gas rises.
5 When the gas reaches the outlet end of the rotors it is released into the discharge header at the
required pressure.
6 The rotors continue to rotate, trapping gas at supply pressure and compressing the gas to outlet
pressure.
Screw compressors are used for small scale compression, where the pressure requirement is low and where high efficiency is required.
A pressure ratio of 3.7 is typically achievable across one stage of a screw compressor (ie, a two stages screw compressor can compress atmospheric air to 13 bar(g).
Screw compressors have two rotors which fit together. One is machined with helical lobes (male) and the other is helically grooved (female). They rotate together in the compressor housing, which is shaped like a figure of eight. As the rotors turn they trap gas between them and the volume of the enclosed space decreases as the gas is pushed towards the outlet.
The diagrams below show a typical helical screw compressor and the process of compression. In this case the male rotor has four lobes and the female has six lobes.
This is how the compressor works stage by stage…..see the below figures…..
Stage Description
1 Gas at supply pressure is trapped between the rotating male and female rotors.
2-4 As the two rotors turn the volume between them progressively decreases, so the pressure of the
trapped gas rises.
5 When the gas reaches the outlet end of the rotors it is released into the discharge header at the
required pressure.
6 The rotors continue to rotate, trapping gas at supply pressure and compressing the gas to outlet
pressure.
The diagrams below show a typical helical screw compressor and the process of compression. In this case the male rotor has four lobes and the female has six lobes.
This is how the compressor works stage by stage…..see the below figures…..
Stage Description
1 Gas at supply pressure is trapped between the rotating male and female rotors.
2-4 As the two rotors turn the volume between them progressively decreases, so the pressure of the
trapped gas rises.
5 When the gas reaches the outlet end of the rotors it is released into the discharge header at the
required pressure.
6 The rotors continue to rotate, trapping gas at supply pressure and compressing the gas to outlet
pressure.
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