WinGD X62DF-S2.0 User Manual

Marine Installation Manual 2022-03 6-10
6 Engine Dynamics
6.2 External lateral forces and moments
X62DF-S2.0
Determining the minimum number of required lateral stays
On a scientific basis, the only way to determine the minimum number of re-
quired lateral stays (i.e. stays in the lateral direction) is by finite element calcula-
tion. This calculation takes into account the exact mass and stiffness properties
of the foundation, as well as the aft section of the ship. This dynamic finite ele-
ment investigation must be executed by the shipyard or a design institute.
WinGD does not have these ship hull properties available to perform this exten-
sive investigation.
However, based on broad experience with different bore sizes, cylinder numbers,
and engine ratings, WinGD provides an alternative approach to determining the
minimum number of required lateral stays. WinGD provides the magnitude of
the lateral forces and moments resulting from the engine operation at R1 (as
shown in External forces and moments). Project-specific values are available upon
request. The magnitude of the lateral forces and moments is key for determining
the minimum number of required lateral stays. Based on individual experience,
engine builders and shipyards are free to select a different number of lateral stays.
From the project-specific external forces and moments, the values to consider are
the lateral H-type moment (M
LH
) and the lateral X-type moment (M
LX
) which,
without stays, have a resonance with inadmissible amplitude in the speed range
of 70 to 110 % of CMCR speed (n
CMCR
).
Although there may be engines with high lateral excitations displayed on paper,
these high values may not be relevant due to a missing resonance condition, and
therefore, no stays are required. For example, most of the 7-cylinder engines do
not require any lateral stays. This is mainly due to (a) the strong M
LX
Ord.4 res-
onance which is located sufficiently above the CMCR speed (n
CMCR
) and (b) the
strong M
LH
Ord.7 resonance which is located at low speed.
On the other hand, based on experience, most 8-cylinder engines are known to
have a very strong M
LX
Ord.5 resonance which is located close to the CMCR
speed (n
CMCR
), and therefore, lateral stays are mandatory. The same is appli-
cable for 9-cylinder engines that also have a very strong M
LX
Ord.6 resonance
which is located slightly above the CMCR speed (n
CMCR
).
On twin-engine installations, the lateral stays must be attached on the outboard
side of the engines towards the ship hull. Depending on whether the engine is a
standard or a left engine (see Figure 6-9,  6-11 and Figure 6-10,  6-11), the out-
board side can be on the fuel side or the exhaust side.

WinGD X62DF-S2.0 Specifications

General

Brand	WinGD
Model	X62DF-S2.0
Category	Marine Equipment
Language	English