Twin fins add efficiency benefits to diesel electric installations

16 Jul 2014
Cat Propulsion Twin Fin system from Caterpillar Marine

Cat Propulsion Twin Fin system from Caterpillar Marine

Caterpillar recently formally launched its Cat Propulsion Twin Fin system, designed to save fuel and emissions for diesel-electric installations while improving overall vessel performance.

The system, which was the subject of a presentation at the recent Motorship Propulsion and Emissions conference in Hamburg, was officially launched to the marketplace at the ITS International Tug, Salvage and OSV Convention, held in the same city a few weeks later.

The Twin Fin system is intended to protect 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.

Initially conceived for harsh operating environments, the Twin Fin System comprises a compact electric motor and gearbox configuration connected via a short drive shaft, turning a pair of controllable pitch propellers. The propeller 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 newbuilds, retrofits and conversions in any commercial marine application and is available via the global Cat dealer network.

“We developed the Twin Fin system in partnership with Odense Maritime Technology (OMT) and Scandinavian Marine Group (SMG) initially as a solution to make vessels operating in Arctic conditions less vulnerable to damage to the propulsion system,” said Mattias Hansson, Caterpillar Marine senior project manager. “As the innovative concept has been engineered into vessels, we’ve been pleased to not only see increased reliability but improvements in fuel consumption and thrust performance as well.”

The system is claimed to achieve efficiency gains measurable across a range of performance criteria. The larger propellers running at slower shaft speed offers increased thrust at lower input power, an enhancement that is aided by the minimal mechanical loss within the system. The two fins are hydrodynamically designed, tailored to individual ship designs, which ensures homogenous water flow to the propellers for lower fuel consumption plus lower emissions and noise radiation. For dynamically positioned ships, the system can be specified with tunnel thrusters, either attached to the fins or to a central skeg running between the fins.

Polarcus DMCC was the first operator to incorporate the Twin Fin system on a conversion project involving an Ultstein SX124 vessel.

According to Mr Hansson: “The Twin Fin system is a tailor-made system developed in close collaboration with our clients and is primarily intended for diesel electric vessel applications. The system is designed depending on the operational requirements and profile in order to achieve optimum performance. In addition to being the most compact system of its kind for offshore vessels, the system has proven to be a robust performer during operation without diminishing maneuverability. It achieves better overall performance and increased cargo loading capacity in comparison with azimuth thruster applications.”

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