Rolls-Royce develops marine thruster for offshore vessels

An innovative marine thruster developed by engineers at Rolls-Royce is claimed to be both more powerful and easier to maintain than existing technology.

The newly developed permanent magnet tunnel thruster (TT-PM) — designed to be positioned on the fore and aft sides of a ship — can be used to help vessels manoeuvre and hold position in rough seas.

According to Rolls-Royce, the system offers a number of advantages over traditional tunnel thrusters, including a 25 per cent increase in power output over similar-sized units and a significant reduction in noise and vibration. The device can also be removed underwater, eliminating the need for dry docking.

The thruster comprises a permanent magnet motor in a rim, which drives the propeller in the centre. The permanent magnet motor consists of a stator that carries a number of electrical coil windings, and a rotor fitted with a number of very strong permanent magnets. According to Rolls-Royce, placing the motor in the rim frees up space directly above the thruster where thruster motors are normally located. This makes the thruster room available for other equipment or alternative use.

A rotating magnetic field is created by the stator which interacts with the fields of the permanent magnets on the rotor, which generates force to drive the rotor around, providing the mechanical power.

Anders Almestad, president — offshore at Rolls-Royce, said: ‘The new thruster is quiet, efficient and extremely durable. It is capable of running for thousands of hours in intensive operations such as the harsh conditions of the offshore oil and gas fields, where rapidly varying loads and alternating thrust directions are the norm.’

The first of the new thrusters has now been delivered to Norwegian company Olympic Shipping, which will operate the system on its Olympic Octopus vessel, a multifunctional anchor-handling vessel (AHTS) that is designed for a range of offshore supply operations.