17.5 Input data for torsional vibration calculations
A torsional vibration calculation is made for each installation. For this purpose exact data of
all components included in the shaft system are required. See list below.
Installation
● Classification
● Ice class
● Operating modes
Reduction gear
A mass elastic diagram showing:
● All clutching possibilities
● Sense of rotation of all shafts
● Dimensions of all shafts
● Mass moment of inertia of all rotating parts including shafts and flanges
● Torsional stiffness of shafts between rotating masses
● Material of shafts including tensile strength and modulus of rigidity
● Gear ratios
● Drawing number of the diagram
Propeller and shafting
A mass-elastic diagram or propeller shaft drawing showing:
● Mass moment of inertia of all rotating parts including the rotating part of the OD-box, SKF
couplings and rotating parts of the bearings
● Mass moment of inertia of the propeller at full/zero pitch in water
● Torsional stiffness or dimensions of the shaft
● Material of the shaft including tensile strength and modulus of rigidity
● Drawing number of the diagram or drawing
Main generator or shaft generator
A mass-elastic diagram or an generator shaft drawing showing:
● Generator output, speed and sense of rotation
● Mass moment of inertia of all rotating parts or a total inertia value of the rotor, including
the shaft
● Torsional stiffness or dimensions of the shaft
● Material of the shaft including tensile strength and modulus of rigidity
● Drawing number of the diagram or drawing
Flexible coupling/clutch
If a certain make of flexible coupling has to be used, the following data of it must be informed:
● Mass moment of inertia of all parts of the coupling
● Number of flexible elements
● Linear, progressive or degressive torsional stiffness per element
● Dynamic magnification or relative damping
● Nominal torque, permissible vibratory torque and permissible power loss
Wärtsilä 46F Product Guide - a19 - 1 December 2017 17-3
17. Power TransmissionWärtsilä 46F Product Guide
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