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doi:10.2204/iodp.proc.332.106.2011

Conclusion

The successful LTBMS installation proves the validity of the various methods and techniques developed to minimize VIV and impact shock damage to the sensor assembly. Results from the field test conducted during Expedition 319 (Saffer, McNeill, Byrne, Araki, Toczko, Eguchi, Takahashi, and the Expedition 319 Scientists, 2010) showed that the structural design of the sensor carrier required a complete redesign. A new H-beam type instrument carrier was developed for the sensor tree assembly and adding drill collars to balance the BHA were discussed. VIV monitoring of different assemblies run in the Kuroshio Current, along with tests conducted on land, helped confirm the value of VIV suppression by adding ropes to the drill string and drill collar counterweights. The key points learned from these operations are as follows: (1) the BHA should be lowered in the LCA, with the relative current speed being as low as possible, (2) the drifting speed should be kept well below 1 kt, and (3) the drifting angle between drifting direction and sea current should be kept as small as possible (definitely <45°). These helped Expedition 332 successfully install one of the most complex CORK assemblies yet attempted, more remarkable in light of the relative inexperience in these operations on the part of the Chikyu.

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