Wärtsilä has launched its new 2-speed marine gearbox offering economic and environmental benefits. The product will serve vessels having multiple operational modes or reduced transit speed, such as RoPax ferries, offshore support vessels, tug boats, and fishing vessels.
Compared to a single mechanical propulsion system, a fuel consumption reduction of eight per cent was verified with the gearbox during sea trials. It is anticipated that further reductions of up to fifteen per cent can be achieved, with a similar lowering of nitrogen oxide (NOx) and sulphur oxide (SOx) exhaust emissions.
Constant Engine Speed
These 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 Power Take-Off on the gearbox to remain uninterrupted.
Noise Reduction
Furthermore, the 2-speed gearbox reduces noise emissions by as much as 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.
Rescue Vessel
The first ship to utilise the new gearbox is a rescue vessel owned by the Rescue & Salvage Bureau of the People's Republic of China's Ministry of Transport. The sea trials have been carried out at the Huangpu shipyard in China. The contract was signed in December 2011.
The vessel operates mostly in low speed mode and reaches full speed only for limited periods of time. The 2-speed gearbox allows the operator to make the necessary adjustments as needed, thereby saving costs even when operating at low speed.
The Wärtsilä 2-speed gearbox will be available with a high degree of modularisation in the power range from 2 to 10 MW.
