Operating manual - SAB 120-151 A-frame (including ATEX)
008668 en 2019.08
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Operating instructions
Fig. 18
Note: The sectional view shows the valve structure. Some of the internal oil channels are not
visible.
6.13 Compressor hydraulic system
The hydraulic system of the compressor utilises oil pressure from internally drilled passages in
the compressor casing to selectively load and unload the compressor by applying this pressure to
the actuating hydraulic piston of the movable slide valve (MSV). It also uses oil pressure to ac-
tuate a hydraulic piston that moves the movable slide stop, Volumizer ® II. This allows adjust-
ment of the compressor volume ratio, (Vi) while the compressor is running.
6.14 Capacity control
Compressor loading
The compressor loads when MSV solenoid coil YY2 is energised and oil flows from the solenoid
valve through the regulating valve 182 to compressor port 2 where it enters the load side of the
slide valve piston. This equalises the force on the slide valve piston and discharge pressure on the
slide valve area loads the compressor.
Compressor unloading
The compressor unloads when MSV solenoid YY1 is energised and oil is allowed to flow from com-
pressor port 2 through the regulating valve 181 to the MSV solenoid. This allows discharge pres-
sure on the slide valve piston to unload the slide valve as the piston moves outward.
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