15.2.2
Resilient mounting
Engines driving gearboxes, generators, pumps etc. can be resiliently mounted in order to
reduce vibrations and structure borne noise, while the driven equipment is fixed to a solid
foundation. The engine block is rigid, therefore no intermediate base-frame is necessary. The
resiliently elements are bolted to the engine feet directly.
The transmission of forces emitted by the engine is 10...30% when comparing resiliently
mounting with rigid mounting.
Note!
For resiliently mounted 9L engines the available speed range is limited. Please contact
Wärtsilä for further information.
The standard engine mountings are of conical type. With conical mounting the rubber rubber
element is loaded by both compression and shear. The mounts are equipped with an internal
central buffer. Hence no additional side or end supports are required to limit the movements
of the engine due to ships motions. The material of the mountings is rubber, which has superior
vibration technical properties. Unfortunately natural rubber is prone to damage by mineral oil,
therefore such elements should not be installed directly on the tank top, where they might
come into contact with oily water. The rubber elements are protected against dripping and
splashing from above by means of covers.
The number of resilient elements and their location is calculated to avoid resonance with
excitations from the engine and the propeller.
When installing and aligning the engine on resilient elements it should be aimed at getting the
same force on each rubber element. This means that the compression of all elements is equal.
Due to creep of the resilient elements the alignment needs to be checked at regular intervals
and corrected when necessary. To facilitate the alignment and re-alignment resilient elements
of the height adjustable type are used for resiliently mounted engines.
Due to the soft mounting the engine will move when passing resonance speeds at start and
stop. Also due to heavy seas engines will move. Typical amplitudes are ±3.5 mm at the
crankshaft centre and ± 17 mm at top of the engine (the figures are calculated for a 22.5° roll
angle). The torque reaction (at 1000 rpm and 100% load) will cause a displacement of the
engine of up to 1 mm at the crankshaft centre and 5 mm at the turbocharger outlet. The
coupling between engine and driven equipment should be flexible enough to be able to cope
with these displacements.
Wärtsilä 26 Product Guide - a9 - 7 September 2016
15-7
15. Foundation
Wärtsilä 26 Product Guide
Summary of Contents for WARTSILA 26
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