Page 159 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Compressor Best Practices Be st Practice 3.7

Fig 3.7.9 Screw compressor rotor
profiles

application, due to the development of high efficiency oil sep-
aration coalescers and the lower cost of a flooded-screw type
compressor unit. Dry screw compressors should be considered
External timing gears required for sour process services, since sour gas can cause oil quality
Normal compression ratio 5:1 deterioration, which can result in the need for frequent oil
Jacket cooling and/or rotor cooling and liquid injection allows changes and possible component damage. Facts concerning dry
operation up to 288°C (550° F) max ratio = 10:1 P max = screw compressors are noted in Figure 3.7.10.
2,585 kPa (375 PSI) with special screw profile
Multi staging may be required to prevent high discharge
3
temperature and rotor deflection 500–68,000 m /hr (300– Twin screw e oil-flooded
40,000 acfm) A twin screw, oil-flooded compressor is shown in Figure 3.7.11
1
Approximately / 3 speed of centrifugal compressors and 3x with the major components noted.
speed of flooded screw compressors The oil-flooded twin screw compressor, which was developed
Seals required at each end of screws
in the 1960s, has become the most widely used variety.
The primary reason for its success is its ability to handle very
Fig 3.7.10 Dry screw compressor facts high compression ratios without needing external cooling.
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