Caterpillar diesel-electric twin fin system yields 30% gain in fuel efficiency

(Before It's News)

Caterpillar’s twin fin diesel-electric marine propulsion system, introduced in 2014 and first retrofit to the Polarcus Naila, a seismic vessel, has resulted in a 30% gain in fuel efficiency and an 84% performance improvement in bollard pull thrust during seismic conditions for the vessel, with no reported reliability problems, according to Cat’s 2014 Sustainability Report. These benefits are expected to boost the customer’s revenue by approximately $3.3 million per year.

Initially conceived for harsh operating environments, the Cat Propulsion Twin Fin System comprises a compact electric motor and gearbox configuration connected via short drive shaft, rotating a pair of controllable pitch propellers whose performance is enhanced by two tailor-made fins attached to the hull.

Major transmission parts in the system are accessible from inside the vessel, enhancing ease of maintenance and averting the need to drydock. The Twin Fin solution can be applied to new builds, retrofits and conversions in any commercial marine application and is available via the global Cat dealer network.

The Twin Fin System protects all of the propulsion mechanical parts within the hull profile while retaining the cargo space saving and maneuverability claims made for outboard solutions while simultaneously offering critical reliability gains.

Azimuth thrusters and propellers are the most common diesel-electric propulsion system for modern offshore vessels. However, as vessels are increasingly deployed in more remote and harsh operating environments, wear and dynamic loads lead to unexpected breakdowns, often resulting in time in dry dock, with associated downtime and costs.

Although a conventional diesel-electric or diesel mechanical propulsion system can be more reliable than azimuth thrusters and propellers, the gear, shafts and machinery take up valuable space inside the vessel, while retrofitting is difficult and time-consuming.

Mattias and his team were able to devise a solution that combined the best aspects of both traditional propulsion systems.

The Caterpillar Twin Fin system achieves efficiency gains measurable across a range of performance criteria. It offers increased thrust and requires lower input power due to to larger propellers running at low shaft speed plus minimal mechanical loss through the use of a short drive shaft having only one stern tube bearing.

Hydrodynamically designed fins ensure homogenous water flow to the propellers for lower fuel consumption plus lower emissions and noise radiation. To fulfill dynamic positioning duties, the Twin Fin System can be specified with tunnel thrusters, either attached to the fins or central skeg running between the fins.

Twin fin is tailored, in close cooperation with customers, depending on the vessel requirements, purpose and operational profile. The system provides an efficient concept that features a built-in condition monitoring system and a closed-water lubricated stern tube solution. Because all equipment is contained within the external fins, twin fin is applicable to both new builds and retrofits, where it replaces existing propulsion.

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