The complete actuator is normally integrated with two frequency controlled reversible pump
units, valve block and electrical feed back units. The power pump units consist of reversible pump, flexible coupling and electric motor. Compared with a conventional steering gear system where the pump is continuously running and oil is controlled by a manoeuvring valve, the next system works quite different. The normal situation is that pump/electric motor not is running. This means that the pump/electric motor starts when a rudder command signal is given and stops when the rudder has reached the desired position. The valves in the distribution valve will lock the rudder’s position. The advantages will be lower running time, less energy consumption, less noise, lower temperature, less wear, a cleaner system and a longer lifetime. The motor controller for the electric motor on each pump unit has separate and independent supply from the main switchboard. The power for operating control and steering system of each unit is provided from the main supply for the corresponding electric motor. The two systems are therefore both hydraulically and electrically separate and independent. A fault in one system will therefore not interfere the operation of the other unit.
The unique design is patented in the most part of the world. The pistons or vanes are
integrated in the rotor, i.e. rotor and vanes are one part. The actuator consists mainly of four
parts; housing (upper and lower), rotor w/bearings and dividing walls. What makes the design unique is the “hidden” area developing the force/torque. This area is integrated inside the rotor’s contour with the rudderstock as centre. The actuator is also equipped with a unique vane sealing design. The sealings are arranged in a manner that allows them to absorb spherical movement. Either axial-, radial-, or spherical movement or misalignment during installation will therefore transmit forces to the vanes. The developed torque is constant over the full rudder angle.
The spherical rotor bearing minimises internal friction and eliminates the transfer of rudderstock bending forces into the rudder actuator. The contact surface of the bearing is maintained at all time and is independent of deflection. The bearing surface is continuously lubricated by the hydraulic oil, which ensures long lifetime of the bearings. The spherical design and compact synthetic bearing material have good properties for absorbing and damping vibration and shock impulses.
On photos below you will find a genuine actuator installation on a ship.
Information Source – Rolls-Royce Marine AS (Product – Rudder actuator SV – FCP (Frequency Controlled Pumps))