Product Guide

15. Foundation

15.3 Mounting of generating sets

15.3.1 Generator feet design

Figure 15.5 Instructions for designing the feet of the generator and the distance between its holding down bolt (4V92F0134c)

15.3.2 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.

Product Guide

15. Foundation

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.

Figure 15.6 Recommended design of the generating set seating (3V46L0720e)

15.3.3 Rubber mounts

Thegeneratingsetismountedonconicalresilientmounts,whicharedesignedtowithstandbothcompression and shear loads. In addition the mounts are equipped with an internal buffer to limit 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, chocks or shims should be used to compensate for local tolerances. Only one shim is permitted under each mount.

The transmission of forces emitted by the engine is 10-20% when using conical mounts.

Product Guide

15. Foundation

Figure 15.7 Rubber mounts (3V46L0706a)

15.4 Flexible pipe connections

When the engine or the generating set is resiliently installed, all connections must be flexible and no grating nor ladders may be fixed to the generating set. When installing the flexible pipe connections, unnecessary bending or stretching should be avoided. The external pipe must be precisely aligned to the fitting or flange on the engine. It is very important that the pipe clamps for the pipe outside the flexible connection must be very rigid and welded to the steel structure of the foundation to prevent vibrations, which could damage the flexible connection.