Wärtsilä introduced a novel engine exhaust noise reduction system that could eventually make conventional single unit diesel engine silencers a thing of the past. Designed for applications where little or no engine noise is an operational requirement, such as passenger ships and ferries, offshore and military vessels, Wärtsilä's Compact Silencer System (CSS) is a patented method for designing the complete exhaust systems using multiple silencer elements distributed along the exhaust pipe.
The new system can also help ship owners reduce operating costs because it negates the need for adding more conventional silencers. A conventional silencer is unable to reduce noise across the entire frequency spectrum because engine noise frequencies vary depending on the number of cylinders. There are also external factors affecting the engine's noise level, such as exhaust gas pipe design, amounts of bends, equipment like SCR, Boiler, etc.
As a result, additional silencers are usually added, but this could prove detrimental to the engine. The introduction of further conventional silencers can increase the exhaust gas pressure drop, increasing the thermal load on the engine. Not only can this actually damage the engine, fuel consumption increases too.
The CSS concept covers the whole frequency spectra while maintaining a low pressure drop - an advantage since the introduction of exhaust gas cleaning equipment, such as SCRs and scrubbers, are likely to further increase the exhaust gas back pressure if conventional engine noise systems are used.
Where low weight, low centre of gravity and space is of concern, CSS components have been optimised to minimise the space requirement of the exhaust system. Pre-insulated silencer elements, for instance, are designed to have almost the same diameter as the insulated exhaust gas pipe. Acoustic properties are optimised according to operational and regulatory noise level requirements. Although the final solution selection depends mainly on the noise reduction demand and allowable piping length, the CSS offers a more slender, lighter cost-effective solution compared to single unit systems.