Very quiet Valmet

Transmission

In designing the twin input/single output reduction gearboxes for the cruise ship Blue Sea,Valmet Power

Transmission

paid special attention to noise reduction. The transmissions will couple four 5,280kW Wartsila 8L38 engines rotating at 600 rev/min to twin propellers requiring a speed of 119.4 rev/min.

To reduce noise the gear tooth profile has been altered to give profile corrected teeth suited to the application and load condition and plain bearings are used on the input shaft. The housing structure, materials and component selection were also given special attention.

All of these measures have resulted in a reduction in structure-borne noise of around 5dB(A), says Valmet – although it does come at a slight price premium. While basically the transmission is horizontally offset, it also accommodates a 100mm difference in height between the crankshaft and propshaft centrelines.

Each gearbox has two multi-disc clutches allowing one engine of each pair to be maintained while the other provides power for cruising. While the propellers can be disconnect when anchored while maintaining drive to the shaft generator for electrical power.

To meet the required delivery schedules, Valmet designed and built the gearbox within six months.