Marine Installation Manual
2021-08
6-8
6 Engine Dynamics
6.2 External lateral forces and moments
X72DF
6.2.2
Reduction of lateral vibration
The amplitudes of the vibrations transmitted to the hull depend on the design of
engine seating, frame stiffness and exhaust pipe connections. As the amplitude of
the vibrations cannot be predicted with absolute accuracy, the support to the
ship’s structure and the space needed to install stays should be considered in the
early design stages of the engine room structure. This is true for both lateral and
longitudinal vibrations, which is further discussed along with relative reduction
methods in the following sections.
Lateral hydraulic type stays
If needed, lateral stays must be fitted between the upper engine platform and the
ship hull to avoid harmful resonance conditions. The main effect of lateral stays
is to shift the resonance frequency sufficiently above nominal speed. In addition,
some damping effect is provided by the hydraulic type stays. Such hydraulic type
stays can be either for both-side or one-side installation.
•
Hydraulic type stays for one-side installation have two oil chambers (one on
each side of the piston) and provide in this regard a ‘damping effect’ in both
directions.
•
Hydraulic type stays for both-side installation have an oil chamber on one
side of the piston and an air chamber on the other side. The air chamber
provides little to no damping effect.
The two general arrangements for both stay types are shown in
below
and
Figure 6
-
6 General arrangement of hydraulic type stays for one-side installation
NOTE
WinGD recommends a stiff engine foundation design in the longitudinal
and lateral directions, as this is always best practice in minimising hull
vibrations.
NOTE
The shipyard must have confirmation from the hydraulic type stay sup
-
plier acknowledging its suitability for one-side installation on the engine.
on exhaust side
stays amount acc.
to the requirements
OR
SM-0098
on fuel side
stays amount acc.
to the requirements
