Vibration Preventing Devices
Ishikawajima-Harima Heavy Industries Co., Ltd. (IHI) has developed various practical devices to remedy vibration problems on ships.
One example is an active mass damper, driven by electromagnetic force, reducing vibrations occurring in ships especially in the superstructures.
Features
1. The vibration amplitude largely scatters as long as the vibration is induced by the propeller, because propeller exciting force fluctuates due to the change in flow velocity into the propeller.
2. Vibrations do not always have a single frequency but have several frequencies, since there are several exciting sources in a vessel such as main engine, propeller and auxiliary machines.
Therefore, vibrations in a superstructure cannot be cancelled by installing a simple anti-vibrating device, but a more sophisticated instrument is required.
In order to satisfy the above requirement, an active mass damper has been developed as shown in Photo
An active mass damper can effectively reduce vibrations of fluctuating amplitude as well as the combined frequencies induced by several vibration sources. Vibration characteristics were confirmed by measurements on a VLCC.
