DECEMBER 4, 2013 — Wärtsilä has launched a new two-speed marine gearbox designed for vessels that have multiple operational modes or reduced transit speed, including among others RoPax ferries, offshore support vessels, tug boats, and fishing vessels.
Wärtsilä's says that a fuel consumption reduction of eight percent, compared to a single mechanical propulsion system, was verified with the two-speed gearbox during sea trials and anticipates that further reductions of up to 15 percent can be achieved, with a similar lowering of nitrogen oxide (NOx) and sulfur oxide (SOx) exhaust emissions.
These 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 electric power generation from the power take-off on the gearbox to remain uninterrupted.
Furthermore, the Wärtsilä two-speed gearbox will reduce 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.
The first ship to utilize the new two-speed marine 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 successfully 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 two-speed gearbox allows the operator to make the necessary adjustments as needed, thereby saving costs even when operating at low speed.
"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," says Mr. 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 utilization 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," says Mr Arto Lehtinen, Vice President Propulsion, Wärtsilä Ship Power.
The Wärtsilä two-speed gearbox will be available with a high degree of modularization in the power range from 2 MW to 10 MW. Wärtsilä will continue to introduce its range of two-speed marine gearboxes throughout 2014 and 2015.