Wartsila ?31DF Series, Product Manual

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17. Power Transmission
17.1 Flexible coupling
The power transmission of propulsion engines is accomplished through a flexible coupling or
a combined flexible coupling and clutch mounted on the flywheel. The crankshaft is equipped
with an additional shield bearing at the flywheel end. Therefore also a rather heavy coupling
can be mounted on the flywheel without intermediate bearings.
The type of flexible coupling to be used has to be decided separately in each case on the
basis of the torsional vibration calculations.
In case of two bearing type generator installations a flexible coupling between the engine and
the generator is required.
17.2 Torque flange
In mechanical propulsion applications, a torque meter has to be installed in order to measure
the absorbed power. The torque flange has an installation length of 300 mm for all cylinder
configurations and is installed after the flexible coupling.
17.3 Clutch
In dual fuel engine installations with mechanical drive, it must be possible to disconnect the
propeller shaft from the engine by using a clutch. The use of multiple plate hydraulically
actuated clutches built into the reduction gear is recommended.
A clutch is also required when two or more engines are connected to the same driven machinery
such as a reduction gear.
To permit maintenance of a stopped engine clutches must be installed in twin screw vessels
which can operate on one shaft line only.
17.4 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.
A shaft locking device should 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.
DBAE248994 17-1
17. Power Transmission Wärtsilä 31DF Product Guide