Engineering manual - SAB 355 Screw compressor unit (including ATEX)
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004100 en 2020.10
Technical description
high-pressure (TDSH) and low-pressure (TDSB) applications. The compressor incorporates the
following features.
1. High capacity roller bearings to carry radial loads at both the inlet and outlet ends of the
compressor.
2. Heavy-duty, four-point angular contact ball bearings to carry axial loads are mounted at
the compressor discharge end.
3. Balance pistons located at the inlet end of the compressor to reduce axial loads on the ax-
ial load bearings and increase bearing life.
4. Moveable slide valve to provide fully modulating capacity control from 100% to approx.
10% of full load capacity.
5. VOLUMIZER‚ volume ratio control to allow infinitely variable volume ratio from 2.2 to 5.0
during compressor operation for all models.
6. A hydraulic unloader cylinder to operate the slide stop and slide valve.
7. Bearing and casing design for 28 bar [400 psi] discharge pressure. This bar [psi] rating
applies only to the compressor and does not reflect the design pressure of the
various system components.
8. All bearing and control oil vented to closed thread in the compressor instead of suction
port to avoid performance penalties from superheating suction gas.
9. Shaft seal design to maintain operating pressure on seal well below discharge pressure,
for increased seal life.
10. Oil injected into the rotors to maintain good volumetric and adiabatic efficiency even at
very high compression ratios.
11. Shaft rotation facing compressor, suitable for all types of drives.
12. Dual compressor casing design for very low airborne noise transmission.
Fig. 17: Shaft rotation
Compressor rotation is clockwise when facing the compressor drive shaft. See Fig. 17. Never op-
erate the compressor in reverse rotation as this will damage the bearings.
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