QUESTION

W.R.T rotary vane steering gears:

a) Describe, with the aid of a sketch, how such a unit incorporates an integral rudder carrier;

(b) Explain how vertical rudder movement is accommodated.

Solution.

The rotary vane unit illustrated complies with the. IMO Rules for oil tankers greater than 100000 tonne dwt. having 2 separate, independent power actuating systems.

The two actuators act simultaneously for normal operation, but if loss of hydraulic pressure is detected, they are isolated by automatic hydraulic valves and the intact actuator will remain fully Operative at 50% of the maximum torque.

The rotary vane unit is enclosed by a heavy casing bolted down onto the seating.

At the base of the rotary vane unit is a thrust ring which will support the load from the rudder that is transmitted from the tapered stock via a hydraulic nut onto the rotary vane.

(b)

In the case of the unit illustrated, the rotor has resilient seals at the top and bottom of the vanes which accommodates small vertical movement by wear down, or the rudder lifting through the jumping clearance when pitching.

An alternative method is for the rotary vane to be mounted in anchor brackets with anchor bolts