Operating manual- SAB 355 (including ATEX)
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6.4
Descriptions 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
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Compressor hydraulic system
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Compressor oil cooling system
•
Compressor easy-start 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.
6.5
Compressor
The rotary screw compressor uses mating asymmetrical profile helical rotors to provide a continu-
ous flow of refrigerant vapour, and it 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 the inlet and outlet ends of the
compressor.
•
Heavy-duty, four-point angular-contact ball bearings to carry axial loads are mounted at
the discharge end of compressor.
•
Balance pistons located in the inlet end of the compressor to reduce axial loads on the ax-
ial load bearings and increase the bearing life.
•
Movable slide valve to provide fully modulating capacity control from 100% to approxi-
mately 10% of full load capacity.
•
VOLUMIZER® volume ratio control to allow infinitely variable volume ratio from 2.2 to 5.0
during compressor operation for all models.
•
A hydraulic unloader cylinder to operate the slide stop and slide valve.
•
All bearing and control oil vented to closed thread in the compressor instead of the suction
port to avoid performance penalties from superheating 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.
•
Shaft rotation clockwise facing the compressor, see Fig. 14.