MAN B&W Controllable pitch propeller. Servo oil system
The principle design of the servo oil systems for VBS (fig. 7) and for VB (fig. 8) is identical.
Fig. 7. Propeller equipment type VBS
The VBS system consists of a servo oil tank unit – Hydra Pack, and a coupling flange with electrical pitch feed-back box and oil distributor ring.
For VB propeller equipment with Alpha reduction gearbox, the servo oil system is an integrated part of the gearbox. This means that the servo piston, pitch feed-back box and oil distributor ring are located inside the gearbox.
Fig. 8. Propeller equipment type VB
The electrical pitch feed-back box measures continuously the position of the pitch feed-back ring and compares the signal to the pitch order signal. If deviation occurs, a proportional valve is actuated.
Hereby high pressure oil is fed to one or the other side of the servo piston, via the oil distributor ring, until the desired propeller pitch has been reached.
The pitch setting is normally remote controlled, but local emergency control is possible.