Important:
This bar [psi] rating applies only to the compressor and does not reflect the
design pressure of the various system components.
• All bearing and control oil vented to closed thread in the compressor instead of the suction port
to avoid performance penalties from super heating suction gas.
• Shaft seal design to maintain operating pressure on the seal well below the discharge pressure,
for increased seal life.
• Oil injected into the rotors to maintain optimum volumetric and adiabatic efficiency even at very
high compression ratios.
• Integrated suction strainer on the SAB 283.
• Shaft rotation clockwise facing the compressor, see
Figure 18: Shaft rotation
CAUTION
The compressor rotation is clockwise when facing the compressor drive shaft, see
. You must
never operate the compressor in reverse rotation as this will cause bearing damage.
Compressor lubrication system
The lubrication system on a screw compressor unit performs the following functions:
• Provides lubrication to bearings and seal.
• Provides a cushion between the rotors to minimise noise and vibrations.
• Helps keep the compressor cool and prevents overheating.
• Provides an oil supply to hydraulically actuate the slide valve and slide stop.
• Provides oil pressure to the balance pistons to increase bearing life. Some applications and
operating conditions require a regulated pressure to the balance piston through a separate
port.
• Provides an oil seal between the rotors to prevent rotor contact or gas bypassing.
The compressor unit may be equipped with either a “no pump” or a “demand pump” lubrication
system. Additionally, either system may contain:
• Dual oil filters and liquid injection.
• Water-cooled or thermosyphon oil cooler for compressor oil cooling.
The rotors are constructed with an asymmetrical profile. The male rotor has four lobes, and the
female rotor has six, see
SAB 283-355 A-Frame OHU 6042 and OHU 7650 (including ATEX) Screw Compressor Unit
46
