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05-06-2019 | Engine Technology | News | Article

New Noise Reduction Coupling for Ship Propulsion Systems

Author:
Sven Eisenkrämer

The Austrian company Geislinger presents its new lightweight Silenco Coupling. They are designed to minimize the transfer of the structure-borne sound emitted by marine engines and propulsion systems.

Modern couplings for ships and especially for mega yachts have to fulfil various tasks. Over the past years, the awareness for noise, fuel consumption and exhaust gases has significantly increased. The classification societies like Lloyd’s Register or DNV GL also have taken a closer look at these issues, defining new, stricter noise and environmental specifications. 

Engine noise is mainly transferred via the engine mounts into the ship’s hull, the bridge, the passenger cabins, as well as into the ocean, where the noise leads to a disturbance of sea life. In recent years, active mounts and bearings have been introduced and passive mounts have become a lot more efficient in reducing the noise transfer of the “primary path”. Nowadays, the “secondary path” of the structure-borne noise is becoming an increasingly important issue. The structure-borne sound originates from the engine and the gearbox and is transferred through the power train into the ships structure and further on. In many applications, the coupling between the gearbox and the propeller shaft is the most critical connection. The engine and gearbox are mounted with an elastic or double elastic frame against the ship’s structure, therefore a broad-band reduction in transferring structure borne noise is essential.

Flanges made of a combination of composite material, rubber and steel

Geislinger’s contribution to this environmental issue is the development of the new lightweight Silenco Coupling. “Components with the best acoustical performance have been selected and further optimized for the modular system of the Silenco Coupling”, explains Dr. Lothar Kurtze, Manager of Acoustics at Geislinger. “Additionally, special flanges made out of a combination of composite material, rubber, and steel have been developed. Designed to avoid the resonance effects of its components, the Silenco Coupling ensures a broadband reduction of the transfer of the structureborne noise while offering electric insulation properties.”

The Geislinger Silenco Coupling is available in two different sizes: the SC 63 and the SC 140. Depending on the acoustical needs and the required torque, different versions of the components (flanges, membrane and shaft) are available. Therefore, the new acoustic coupling sets new standards for the acoustic attenuation of powertrain systems.

The Silenco Coupling is designed to do both: transmit the torque and reduce structure borne noise to a very low level. Geislinger furthermore promises that the couplings will be ideally suited for hybrid systems. Specific noise of the electric drivetrain system (e.g. inverter frequencies) is taken care of and due to the low weight of the coupling, the ship can be maneuvered faster. 

In the case of the Silenco, the coupling was first tested using the Geislinger acoustic test bed. In the next step it was tested together with an Electric Drive. The coupling has recently been validated during sea trials of a mega yacht in Europe. On the yacht, unusually low noise levels of the propulsion system were proven. Thus, the coupling helps to significantly reduce the noise. This includes the noise reduction in the ship cabins as well as the noise reduction into the environment. 

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