Vibration Isolation of Compressor Modules on FPSO
Vibratec Akustikprodukter in Sweden has delivered anti-vibration mounts (AVMs) for four large compressor modules to Aibel. The modules are installed on a floating production unit, FPSO, named Aoka Mizu. Now that the final tests have been done and Aoka Mizu passed with success, it is now ready for delivery from the yard in Singapore. Aoka Mizu will be installed and ready for production on the Ettric field in the first quarter of 2009.
The four compressor modules weigh approximately 310t each and are supported by four AVMs each. This is due to the fact that these types of compressors normally generate high levels of vibration. The AVMs consist of steel springs that deflect 25mm under the load, thus giving a very soft suspension. This is required to ensure maximum vibration isolation from the compressor modules to the hull. To prevent big movements in the modules during ultimate and accidental limit states (ULS and ALS) the AVMs are also equipped with adjustable movement limiters. Furthermore, the AVMs are constructed in such a way that horizontal movements between module and skid due to thermal expansion is allowed.
Vibratec Akustikprodukter was involved at a late stage in the project, which caused some extra implications in the design of the AVMs. While the AVMs were designed and manufactured the compressor modules were put on dummies that were the height of the future deflected AVMs. When the AVMs were finally installed they had to be pre-compressed with 130t and locked in this compressed state, after which they could be slid under the modules. Once in position the pre-compression could carefully be released, giving a height increase of the AVMs that finally carried the complete module weight.
Due to shortage of time the finalised AVMs, weighing approximately 45t, had to be transported with air freight from Sweden to Singapore.