An innovative satellite-based condition monitoring system, developed by SKF, is playing a vital role in the successful operation of the Queen Mary II cruise ship.
Fitted to each of the vessel's four powerful pod propulsion systems, the condition monitoring system provides continuous feedback on levels of vibration, temperature and oil quality, with data being fed directly and in real time to both on-board and on-shore monitoring and control stations.
The Queen Mary II (QMII) stands 72 metres high, has 17 decks, carries up to 3,000 passengers and cost 800 million dollars to build. Although the ship has many innovative and features, perhaps the most unusual is the use of four Rolls-Royce Mermaid pod propulsion systems.
These replace the conventional arrangement, where diesel engines drive one or more propellers, with pods mounted externally on each side of the vessel. Each of the pods contains an electric motor, driven via a generator from the ship's diesel engines, and connected via a shaft to a fixed pitch propeller.
Two of the pods are static and two rotate through 360 degrees; combined, the four pods are capable of producing speeds of up to 30 knots, yet produce lower levels of noise and vibration throughout the vessel, and give better fuel efficiency than conventional propulsion systems. In addition, the pods eliminate the need for rudders and stern thrusters providing far greater manoeuvrability than has previously been possible for vessels of this size.
For the ship's operators, the Cunard Line, it is essential to maximise the operating life of the QMII and to minimise the time that the vessel is unavailable due to maintenance or repair. As a result, the ship's engineers have incorporated sophisticated condition monitoring technology in the propulsion pods, based around SKF's MasCon48 system.
The MasCon48 system is designed to measure the level and pattern of vibration from the various shafts and bearings used in each pod, plus the temperature of motor windings and bearings, and the quality and changing condition of lubricating oils using sensors and particle counters mounted in each oil sump. The MasCon48 system relays data and any anomalies to maintenance personnel on-board, together with advice for correcting existing or impending conditions. The data is also simultaneously relayed via satellite to both the SKF Condition Monitoring and the Rolls-Royce Control Centres in Sweden. Alarms are presented as plain text messages to maintenance crews highlighting, for example, problems such as unbalanced shafts, cavitation, bearing condition or electrical faults.
The MasCon48 system was especially modified to meet the demands of the unique operating environment on the QMII. In particular, special rule-based diagnostics were incorporated to prevent false alarms being generated during complicated ship manoeuvres; these can create unusual vibration patterns that vary from normal cruising conditions and can take time to settle. The diagnostics are therefore set to monitor ship speed, shaft speed and steering angle and to compare this data with standard readings before deciding when to resume normal monitoring conditions.
The QMII regularly sails across the Atlantic from London to New York and, in 2007, is embarking its first round the world cruise taking 81 days to sail from Fort Lauderdale in Florida before finally returning to Southampton in the UK. Throughout the voyage the SKF condition monitoring technology will be playing a continuous role to ensure that key ship's systems operate to optimum levels of efficiency and reliability.
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