Thruster exchange operations are performed when an azimuth thruster on a DP operated vessel needs to be replaced for repair or maintenance purposes. At present these operations are performed either during a dry-dock call or in sheltered waters with the assistance of a shearleg or heavy lift vessel moored alongside the DP operated vessel. In order to reduce downtime of the DP operated vessel a clear trend is observed of operations being carried out more offshore and in deeper waters by means of a wet handshake between a heavy lift vessel (HLV) and a DP operated vessel. To get insight into the workability of such offshore thruster exchange operations it is important to study the dynamic interactions between the bodies involved. This paper describes the development of a methodology which accurately determines the workability of an offshore thruster exchange operation. The methodology is developed by BigLift Shipping, which has performed several thruster exchange operations in sheltered waters in the past few years. Furthermore the results of a workability analysis of a thruster exchange operation offshore Ghana are presented.
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