Marine Installation Manual
2021-08
6-4
6 Engine Dynamics
6.1 External mass forces and moments
X72DF
If the mode shapes of the vertical hull girder vibrations are known, it might be
possible to install only one iELBA on one of the engine sides. The calculation of
the vertical hull girder frequencies, the corresponding mode shapes and conse
-
quently the decision on the number of iELBA systems to be installed is in the re
-
sponsibility of the shipyard.
Electrically-driven compensator (external compensator)
Alternatively, or if the ship’s vibration pattern is not known at an early stage, an
electrically-driven compensator can be installed or retrofitted if disturbing
second order vibrations should occur. As seen in
, such a compensator
is usually installed in the steering gear compartment. It is tuned to the engine op
-
erating speed and controlled accordingly.
Figure 6
-
3 Locating an electrically-driven compensator
NOTE
The iELBA system cannot be retrofitted to the engine. The iELBA must
be ordered, designed and implemented on engine before manufactur-
ing commences.
SM-0031
F
2V
M
2V
= F
2V
× L
L
M
2V
Electrically-driven
2
nd
order
compensator