The Wärtsilä 2-speed gear is designed to serve vessels having multiple operational modes or reduced transit speeds. These vessels like fishing vessels, rescue tugs, offshore support vessels and seismic support vessels can gain notable economic & environmental benefits.
The Wärtsilä 2-speed gear is available with a high degree of modularization in the 2 MW to 13 MW power range.
High propulsion efficiency
Certain single screw vessels, such as product tankers and fishing vessels, might have an extra class notation for redundant propulsion in case of a main engine failure. With such a class notation, the Wärtsilä 2-speed gear has a special functionality, since the shaft generator can be used as an electric motor, while the propeller runs at its lowest speed. Thanks to the choice of having two propeller speeds, the actual propulsion power needed to comply with the redundant class notation can be reduced significantly.
Reduced noise and vibration
The Wärtsilä 2-speed gear reduces noise emissions by up to 20 dB, both inside the ship and externally. This allows greater comfort for crew and passengers, while the reduced underwater radiated noise is important for fishing and seismic vessels, and is beneficial to marine life in general.
Fuel savings of up to 15% can be achieved compared to a single speed mechanical propulsion system, thanks to the key feature of the 2-speed gearbox: the option to reduce the propeller speed while the vessel speed remains constant.
All Wärtsilä gears can be supplied with one or more PTOs for driving the shaft alternator, compressor or pump. For single vertical and horizontal gears, the standard PTO is primary driven. For double gears, the PTO is optionally primary or secondary driven.
A primary driven PTO rotates whenever the engine is rotating.
A secondary driven PTO rotates whenever the propeller shaft is rotating.
Most Wärtsilä gears can be supplied with a combined PTO/PTI. In PTI mode the shaft alternator can also be used as an electric motor. PTI is normally used for the following operational modes:
PTI “Booster” mode is used when the main power of the engine is insufficient in order to increase the total propulsion power. For this mode, no clutches are required on the gear.
PTI “Take me home” mode is used in case of emergency should the prime mover be inoperable. For this mode a minimum of 2 clutches are required on the gear.
Based on the standard Wärtsilä gear types, customized solutions can be delivered upon request.
Most Wärtsilä gears are purpose-designed with an integrated hydraulic system for both the gear and the CP propeller. As a separate hydraulic power unit for the CP propeller is superfluous, both installation costs for the yard and operational costs for the owner are reduced. For safety reasons the gear mechanically drives the main pump for the propeller. All gears can also be interfaced with a separate hydraulic power unit.