Operating manual - SAB 120-151 A-frame (including ATEX)
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008668 en 2019.08
Operating instructions
6.5 Description of main components and systems
The screw compressor unit is an integrated system consisting of the following major subsystems:
• Control system
• Compressor
• Compressor lubrication system
• Compressor oil separation system
• Compressor hydraulic system
• Compressor oil cooling system.
The information in this section of the manual provides the logical step-by-step instructions to
properly start up and operate the screw compressor unit.
The following subsections must be read and understood before attempting to start or operate the
unit.
6.6 Compressor
The rotary screw compressor uses mating asymmetrical profile helical rotors to provide a continu-
ous flow of refrigerant vapour and is designed for both high-pressure and low-pressure applica-
tions. The compressor incorporates the following features:
• Heavy-duty roller bearings to carry radial loads at both inlet and outlet ends of the
compressor.
• Heavy-duty angular contact ball bearings to carry axial loads are mounted at the dis-
charge end of compressor.
• Moveable slide valve to provide infinite step capacity control from 100% to 25% of full
load capacity.
• VOLUMIZER® II adjusts to the most efficient of three volume ratios (2.2, 3.5 or 5.0) de-
pending on system requirements.
• Hydraulic cylinders to operate the volumizer slide stop and slide valve.
• Compressor housing suitable for 28 bar [400 PSI] pressure.
• Most bearing and control oil is vented to closed threads in the compressor instead of suc-
tion port to avoid performance penalties from superheating suction gas.
• The shaft seal is designed to maintain operating pressure on the seal well below discharge
pressure for increased seal life.
• Oil is injected into the rotors to maintain good volumetric and adiabatic efficiency, even at
very high compression ratios.
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