Economic and environmental advantages of the two-speed gearbox

Finnøy Gear & Propeller’s two- speed gearbox is used on vessels with large differences in power need, such as anchor handling, tanks or the coastal and oceangoing fishing fleet. Due to relatively low technical complexity, the two- speed gearbox offers optimized functionality at a low cost.

The configuration has the advantage of being able to have two different propeller speeds at constant engine speed, and the propeller can be operated at optimal speed both at high and low load. The two- speed gearbox results in minimized zero pitch loss and keeps propeller noise and vibrations at a minimum both internally and externally. Reduced noise emissions allows for greater comfort for the crew, as well as underwater radiated noise is of great importance for offshore, fishing and seismic vessels. Furthermore, fuel saving at low load results in a reduction of a vessels emissions.

In high gear, clutch 1 is engaged and clutch 2 is disengaged, meaning full engine power can be given to the propeller, and excess power to the shaft generator. In low gear, clutch 1 is disengaged and clutch 2 is engaged, resulting in reduced engine power to the propeller due to lower propeller speed, and excess power to the shaft generator. Both gears allow for uninterrupted work of the generator at constant speed of Power Take- off shaft. In addition, the gearbox can be constructed with a 3rd clutch for disengaging the shaft generator when needed.

In addition to the two- speed gearbox, the vessel can also utilize floating frequency, allowing the engine speed to be lowered in “generator mode”. Variations in the engine speed which correspond to the floating frequency of the shaft generator from 50 Hz to 60 Hz allows for optimal propeller speed in the full operation range. Furthermore, the two- speed gearbox is available in a high range of transmitted power – from 750 kW up to 12000 kW.

Mr. Jakub Kozlowski, Project Engineer at Finnøy Gear & Propeller, said: “To meet the growing demand of shipowners in terms of fuel economy and flexible operation range, the first gearbox from the two-speed family was already delivered in 2000. By applicating high safety margins during engineering work combined with more than 135 years of experience, the gearboxes run both safe and reliable with low transmission losses. Broad engineering knowledge in our team and the usage of top quality materials results in equipment beyond compare on the marine gearbox market.”

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