Operating manual- SAB 355 (including ATEX)
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004059 en 2019.11
Operating instructions
Booster compressor loading
The compressor loads when the MSV solenoid valve, YY2, is energised, and oil flows from the oil
manifold through the valve ports, P and B, to the cylinder port, SC2, and enters the loading side
of the cylinder. Simultaneously, oil contained in the unloading side of the cylinder flows out of cyl-
inder port, SC1, through the valve ports, A and T, to the compressor suction side.
Booster compressor unloading
The compressor unloads when MSV solenoid, YY1, is energised, and oil flows from the oil manifold
through valve ports, P and A, to cylinder port, SC1, and enters the unload side of the cylinder. Si-
multaneously, oil contained in the load side of the cylinder flows out of compressor port, SC2,
through valve ports, B and T, to the compressor suction side.
Note: To control the rate of loading and unloading, change cycle time, proportional band and
dead band set points with the control system. If additional control is needed, throttle SC2 or BP.
Note: To slow all valve movements, i.e. loading, unloading and Vi change, throttle valve 186.
Fig. 21: Volumizer volume ratio control
Caution!
Never open valve BP and valve SC2 at the same time during compressor operation.
6.13 Volumizer volume ratio control
Note: See Fig. 20: Compressor hydraulic system for port references.
• Open valve at SC3.
6.14 Compressor V
i
increase
The volume ratio V
i
is increased when MSS solenoid valve YY3 is energized and oil flows from the
oil manifold through valve ports P and A to compressor port SC3, enters the increase side of the
cylinder and overcomes the decrease spring tension. On SAB 355 the SC4 port does not exist.
The inboard side of the slide stop piston is at suction pressure.
6.15 Compressor V
i
decrease
Oil flows from the SC3 port through the valve ports A and T to the compressor suction side. On
SAB 355 models, the SC4 port does not exist. On these models, YY4 is energized, which allows oil
to vent from port A to T with assistance from the unloader spring.
To control the rate of V
i
change, throttle the needle valve at the SC3 port.
SC1
SC3
See hydraulic
schematic for
functional
view of valve
operation
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