A luxury cruise liner is using special coated spherical roller bearings from Schaeffler to help ensure the smooth, safe manoeuvring of the ship, while reducing vibration and noise levels.

The ship's propulsion and steering drives utilise one FAG radial spherical roller bearing and two FAG spherical thrust roller bearings, which enable the liner to accelerate to a speed of 24 knots (45km/h).

The bearings ensure that steering and precise deceleration manoeuvres are performed smoothly and safely.

Special coatings on the bearings are critical to the efficient operation of the drives.

Propulsion and steering of the ship are combined in a freely rotating vertical pod outside of the hull.

These so-called 'POD drives' provide low vibration and noise levels during operation, therefore enhancing passenger comfort.

The drives improve the manoeuvrability, and therefore the safety, of the ship, as well as offering higher efficiencies, resulting in both lower fuel consumption and reduced emission levels.

The power output per drive unit is 20MW.

Schaeffler's bearings support the drive shaft on the locating bearing side in each of the two engine pods, accommodating thrust forces and loads from the engine and propeller.

The large spherical thrust roller bearing, which has an outside diameter of 850mm, serves as the main thrust bearing and is subjected to thrust loads of up to 150 tonnes at maximum speeds of 135rev/min.

Under extreme conditions, the bearing can even support loads of up to 430 tonnes for short periods.

The smaller counter bearing, which is also an FAG spherical thrust roller bearing, has an outside diameter of 620mm.

The bearing withstands reverse thrust loads during manoeuvring operations.

The bearing is designed for loads of up to 20 tonnes, although in extreme cases, it can withstand loads of up to 200 tonnes for short periods.

The FAG radial spherical roller bearing, also supplied by Schaeffler, is designed to accommodate radial loads from the engine, the weight of the propeller and dynamic forces.

The bearings in the Schaeffler thrust block unit are arranged in such a way that they align via a common point and so are able to compensate for any misalignment of the drive shaft.

In order to optimise bearing system kinematics and reduce friction, the outer ring of the radial spherical roller bearing and the housing washers of the spherical thrust roller bearings are coated with Durotect Z.

Developed by Schaeffler, this special coating reduces the co-efficient of friction and adhesion properties, while increasing the bearing's resistance to corrosion and fretting.

In addition, the outer diameter of the 7.5 tonne thrust block unit (flange connection) is equipped with a 14mm-thick, synthetic compound coating, which offers good damping properties, as well as providing electrical insulation.

This coating prevents the rolling contact zone from being damaged by leakage currents or downdraft.

The coating provides reliable protection up to 15000V.

The thrust block unit's bearing and oil bath are monitored using temperature sensors.

The individual bearings are also fitted with a condition-monitoring system that detects damage at an early stage, enabling maintenance tasks to be planned well in advance.

This eliminates costly, unexpected bearing failures.

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