Two-speed marine transmissions from Wärtsilä

04 Dec 2013
The Wärtsilä two-speed gearbox, designed for lower operating cost and better environmental performance

The Wärtsilä two-speed gearbox, designed for lower operating cost and better environmental performance

Wärtsilä has launched a two-speed marine gearbox, intended for ships with multiple operating modes or low transit speeds, such as ro-pax ferries, offshore support vessels, tugs and fishing vessels.

The company claims that sea trials with the two-speed gearbox recorded fuel savings of 8% compared to a single mechanical propulsion system. With further optimisation and development, further savings, possibly as much as 15%, can be achieved, with corresponding reductions in emissions.  

The company says that the cost savings and environmental benefits are achieved by operating the ship's propeller at low speed when maximum vessel speed or propeller thrust is not required. At the same time, the engine speed is kept constant, thereby allowing the electric power generation from the PTO, sited on the gearbox, to remain uninterrupted. Other claimed benefits include a noise reduction of up to 20dB both inside the ship and externally. This allows greater comfort for passengers and crew, while the reduced underwater radiated noise is important for fishing and seismic vessels, and is beneficial to marine life in general.

The first ship to feature the new gearbox is a rescue vessel owned by the People's Republic of China's Ministry of Transport Rescue & Salvage Bureau. The ship, built by the Huangpu shipyard in China, operates mostly in low speed mode and reaches full speed only for limited periods of time. The two-speed gearbox allows the operator to make the necessary adjustments as needed, thereby saving costs even when operating at low speed.

The gearbox will be made available in power handling capabilities from 2MW to 10MW. The modular construction gearbox has been designed in response to demands for lower operating costs and improved environmental performance, requirements that the company believes will become more crucial in the future. Wärtsilä will introduce other two-speed marine gearboxes in the range throughout 2014 and 2015.

"The Wärtsilä two-speed gearbox is the best solution for our rescue vessel in terms of both economy and overall efficiency. This gearbox enables a proper balance between full speed operation and the ship's daily operating mode, which is important because its operating profile varies," said Sun Lu Ming, deputy chief engineer of MOT Rescue and Salvage Bureau.

"This new propulsion solution is based on Wärtsilä's proven gearbox technology and systems engineering. It offers considerable fuel cost savings, increased environmental sustainability, efficient utilisation of the main engine, a high degree of redundancy, retention of 100 per cent engine power at reduced propeller speeds, advanced functionality with low technical complexity, and much more. It also strengthens Wärtsilä's leading position as provider of complete solutions and integrated systems to the maritime sector," said Arto Lehtinen, vice president propulsion, Wärtsilä Ship Power.

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