Marine Installation Manual
2021-08
6-18
6 Engine Dynamics
6.8 Countermeasures for dynamic effects
X72DF
6.8
Countermeasures for dynamic effects
6.8.1
External mass moments and vibrations
The following tables indicate where dynamic effects and the countermeasures re
-
quired to reduce them are to be given special attention.
Where installations incorporate PTO arrangements (see
),
further investigation is required and WinGD should be contacted.
Table 6
-
1
Countermeasures for external mass moments
Table 6
-
2
Countermeasures for lateral and longitudinal vibrations
Table 6
-
3
Countermeasures for torsional and axial vibrations of the shafting
No. of cyl. Second order compensator
5-6
Balancing countermeasure is likely needed
7-8
Balancing countermeasure is not relevant
No. of cyl. Lateral stays
Longitudinal stays
5
A
C / A
a)
a) ‘A’ for installations having the main torsional critical above nominal speed (installations with in
-
creased shaft diameters)
6
B
C
7
C
b)
/ B
c)
b) ‘C’ for n
cmcr
≤
84rpm
c) ‘B’ for n
cmcr
>
84rpm
C
8
A
C
A = The countermeasure indicated is needed.
B = The countermeasure indicated may be needed and provision for the corresponding
countermeasure is recommended.
C = The countermeasure indicated is usually not needed.
No. of cyl. Torsional vibration
Axial vibration
5-8
Detailed calculations have to be
carried out for every installation;
countermeasures to be selected
accordingly (shaft diameters, cri-
tical or barred speed range, flywheel,
tuning wheel, torsional vibration
damper).
An integrated axial vibration damper
is fitted as standard to reduce the
axial vibration in the crankshaft.
However, the effect of the coupled
axial vibration on the propulsion
shafting components should be
checked by calculation.
