steering gear · steering system

Rolls-Royce Rotary Vane RV 600

The Rolls-Royce Rotary Vane RV600 is a marine steering gear of the rotary-vane type, the machinery that turns a ship's rudder to steer the vessel. Every ship must be able to move its rudder reliably and with enough force to steer in all conditions, and the steering gear is the powered system that does this, responding to orders from the bridge or the autopilot. The rotary-vane design is one of the main forms of hydraulic steering gear, valued for being compact and for applying torque directly to the rudder stock. In a rotary-vane steering gear, vanes fixed to a rotor on the rudder stock sit within a housing containing matching fixed vanes, dividing the housing into chambers. Hydraulic oil, delivered by electrically driven pumps, is admitted to the chambers on one side and released from the other, so that the pressure difference rotates the rotor and with it the rudder stock, turning the rudder. Reversing the flow turns the rudder the other way. Because the torque is produced directly at the stock, the arrangement is space-saving compared with the ram-and-tiller type and delivers high turning moment, which suits it to a wide range of ships. Steering gear is safety-critical equipment, and its design and testing are governed by SOLAS. Ships must have a main steering gear capable of putting the rudder over quickly at full speed, and an auxiliary means of steering, with duplication of essential components and power units so that a single failure does not leave the ship unable to steer. Alarms, and the ability to change over to standby pumps and to control the gear from the steering compartment, are required, and the equipment is tested before departure and exercised in drills. The rotary-vane steering gear such as the RV600 exemplifies the compact, powerful and reliable machinery that turns the rudder and so keeps a ship under command.