First installation of R-R PM rim thruster

The design concept is based on a permanent magnet motor in a rim, which drives the propeller in the centre. The permanent magnet motor consists of two main parts – a stator that carries a number of electrical coil windings, and a rotor fitted with a number of very strong permanent magnets. A rotating magnetic field is created by the stator which interacts with the fields of the permanent magnets on the rotor, generating force to drag the rotor around, providing the mechanical power.

Numerous advantages are claimed for the TT-PM over traditional tunnel thrusters, including an increase in power output of around 25% from the same size propeller, lower noise and vibration, and capability for underwater removal eliminating the need for dry docking.

Other claimed benefits include the freeing up of space directly above the thruster where traditional tunnel thruster motors are located, and a symmetrical design that gives equal thrust to port or starboard. It is available in 1600mm and 2000mm diameters.

Rolls-Royce says the thruster has been through an extensive test programme, operating continuously for many months, to demonstrate its reliability, enhanced maintainability, performance and operational efficiency.

Knut Eilert Røsvik, vice president offshore propulsion, Rolls-Royce said: “We are delighted that Olympic Shipping is the first customer to select our new tunnel thruster, which heralds a step-change in thruster design and performance. This cutting edge technology is suitable for a range of applications in offshore and merchant vessels, where high power output, and rapid response to power demand, combined with exceptionally low noise levels will benefit operators, crew and passengers alike. The goal in the development of the TT-PM has been not just a permanent magnet motor thruster, but a quiet, efficient and durable tunnel thruster, capable of running for thousands of hours in intensive dynamic positioning (DP) mode, where rapidly varying loads and alternating thrust directions are the norm.”

The Olympic Octopus was delivered in 2007 and is a multifunctional AHTS ship to Rolls-Royce design UT 712 L. The TT-PM is currently being fitted into the hull.

Mr Røsvik says: “We are especially proud to be able to install the first commercial TT-PM on this particular vessel. Upon delivery Olympic Octopus was equipped with a demonstrator of a rim driven tunnel thruster from Rolls-Royce. Our continuous research and technology depend on the experiences from the ship owners and their crews.”