WÄRTSILÄ 46F Series, Product Manual

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17. Power Transmission
17.1 Flexible coupling
The engine is connected to the reduction gear or generator with a flexible coupling. The type
of flexible coupling is determined separately for each installation based on the torsional vibration
calculations.
17.2 Clutch
Hydraulically operated multi-plate clutches in the reduction gear are recommended.
A clutch is not absolutely required in single main engine installations, provided that the friction
torque of the shaft line does not exceed the torque capacity of the turning gear, or there is a
tooth coupling so that the engine can be separated from the propeller shaft. A combined
flexible coupling and clutch mounted on the flywheel is usually possible without intermediate
bearings, because the engine is equipped with an additional bearing at the flywheel end.
Clutches are required when two or more engines are connected to the same reduction gear.
To permit maintenance of a stopped engine, either clutches or tooth couplings are required
in twin screw vessels, if the vessel can operate with only one propeller.
17.3 Shaft locking device
A shaft locking device should also be fitted to be able to secure the propeller shaft in position
so that wind milling is avoided. This is necessary because even an open hydraulic clutch can
transmit some torque. Wind milling at a low propeller speed (<10 rpm) can due to poor
lubrication cause excessive wear of the bearings.
The shaft locking device can be either a bracket and key or an easier to use brake disc with
calipers. In both cases a stiff and strong support to the ship’s construction must be provided.
To permit maintenance of a stopped engine clutches must be installed in twin screw vessels
which can operate on one shaft line only.
Fig 17-1 Shaft locking device and brake disc with calipers
DAAB605814 17-1
17. Power Transmission Wärtsilä 46F Product Guide