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 cylinder
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.
Simultaneously, 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 the
valves SC1 or SC2.
Figure 24: Volumizer volume ration control
CAUTION
Never
open valve BP and valve SC2 at the same time during compressor operation.
Volumizer volume ratio (VI) control
Note:
For port references, see
Open valve at SC3.
Compressor VI increase
The volume ratio VI 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.
53
SAB 283-355 A-Frame OHU 6042 and OHU 7650 (including ATEX) Screw Compressor Unit
