Marine Installation Manual
2021-08
6-19
6 Engine Dynamics
6.8 Countermeasures for dynamic effects
X72DF
6.8.2
Synchro-Phasing System in twin engines
An available countermeasure for vibration reduction in twin engine vessels is
WinGD’s Synchro-Phasing System (SPS). By changing the relative phase differ
-
ence of the two engines operating with the same speed, it is possible to neutralise
vibrations of a selected frequency and the resulting resonance on the ship’s hull
or structure.
Synchro-Phasing can be an effective way of reducing vibrations without modifi
-
cations to the ship’s structure and with limited cost.
Concept
As discussed previously in this section, it is important that vibrations of the en
-
gine or propeller are minimised. Some specific vibrations will be problematic if
they cause resonance in the surrounding vessel structure.
Alteration of phase angles
With twin-engine vessels the resulting vibration amplitude is equal to the sum of
both engines and is therefore dependent on the phase difference of the engines.
The phase difference of any two vibrations is the relative difference (of angle or
time) between any matching points of their vibrational cycles.
It is shown in
that if the vibrations are in phase (0 ° phase difference)
the resultant amplitude can reach double that of a single vibration. However, to
-
wards a phase difference of 180 ° the amplitude is reduced from the vibrations
neutralising each other.
Figure 6
-
11 Resulting vibration from SPS combinations
By correctly altering the phase angles between two crankshafts, a vibration can
be reduced and possibly eliminated, limiting vibrations distribution in the ship’s
hull and superstructure.
1
st
engine vibration
2
nd
engine vibration
Resulting vibration combination
In phase - 0˚
Out of phase - 90˚
Out of phase - 180˚
SM-0515
