15.3 Mounting of generating sets
15.3.1 Resilient mounting
Generating sets, comprising engine and generator mounted on a common base frame, are
usually installed on resilient mounts on the foundation in the ship.
The resilient mounts reduce the structure borne noise transmitted to the ship and also serve
to protect the generating set bearings from possible fretting caused by hull vibration.
The number of mounts and their location is calculated to avoid resonance with excitations
from the generating set engine, the main engine and the propeller.
NOTE
To avoid induced oscillation of the generating set, the following data must be sent
by the shipyard to Wärtsilä at the design stage:
● main engine speed [RPM] and number of cylinders
● propeller shaft speed [RPM] and number of propeller blades
The selected number of mounts and their final position is shown in the generating set drawing.
Fig 15-2 Recommended design of the generating set seating (DAAE020067B)
15.3.1.1 Rubber mounts
The generating set is mounted on conical resilient mounts, which are designed to withstand
both compression and shear loads. In addition the mounts are equipped with an internal buffer
to limit the movements of the generating set due to ship motions. Hence, no additional side
or end buffers are required.
The rubber in the mounts is natural rubber and it must therefore be protected from oil, oily
water and fuel.
The mounts should be evenly loaded, when the generating set is resting on the mounts. The
maximum permissible variation in compression between mounts is 2.0 mm. If necessary,
15-4 DBAE248994
Wärtsilä 31DF Product Guide15. Foundation
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