Wartsila ?31DF Series, Product Manual, Page: 162 / 216

11.2.10.2 Silencer system comparison
With a conventional silencer system, the design of the noise reduction system usually starts
from the engine. With the CSS, the design is reversed, meaning that the noise level acceptability
at a certain distance from the ship's exhaust gas pipe outlet, is used to dimension the noise
reduction system.
Fig 11-8 Silencer system comparison
11.2.10.3 Compact silencer system (5N02)
The CSS system is optimized for each installation as a complete exhaust gas system. The
optimization is made according to the engine characteristics, to the sound level requirements
and to other equipment installed in the exhaust gas system, like SCR, exhaust gas boiler or
scrubbers.
The CSS system is built up of three different CSS elements; resistive, reactive and composite
elements. The combination-, amount- and length of the elements are always installation
specific. The diameter of the CSS element is 1.4 times the exhaust gas pipe diameter.
The noise attenuation is valid up to a exhaust gas flow velocity of max 40 m/s. The pressure
drop of a CSS element is lower compared to a conventional exhaust gas silencer (5R02).
11-8 DBAE248994
Wärtsilä 31DF Product Guide 11. Exhaust Gas System