azimuth thruster · thrusters system

Rolls-Royce Azipull AZP100

The Rolls-Royce Azipull AZP100 is an azimuth thruster, a combined propulsion and steering unit that can rotate through a full circle to direct its thrust in any horizontal direction. Instead of the traditional arrangement of a fixed propeller shaft and a separate rudder, an azimuth thruster mounts the propeller on a steerable underwater unit, so that turning the unit both propels and steers the vessel. This gives outstanding manoeuvrability, which is why azimuth thrusters are favoured for offshore supply vessels, tugs, ferries and other craft that must position themselves precisely. The Azipull is a pulling-type thruster, meaning the propeller is mounted at the forward end of the underwater pod and pulls the unit through relatively undisturbed water, ahead of the supporting strut and gear housing. This inflow benefits efficiency and can improve the smoothness of the water reaching the propeller compared with a pushing arrangement. A bevel-gear drive transmits power from an engine or motor down through the steerable column to the propeller shaft, and the whole unit is rotated by a steering system to set the direction of thrust. Because it can vector thrust in any direction, an azimuth thruster is central to dynamic positioning, the capability by which a vessel holds a fixed position and heading automatically against wind, current and waves, essential for offshore work such as supporting rigs and installing subsea equipment. Several thrusters, controlled together by the dynamic positioning system, continuously adjust their direction and power to keep the ship on station. Azimuth units also allow a vessel to move sideways, turn on the spot and dock without tug assistance. The Azipull is representative of modern propulsion units that integrate propulsion and steering into a single steerable device, delivering the manoeuvrability and station-keeping that many specialised vessels require, in place of the conventional shaft-and-rudder arrangement of typical cargo ships.