SELECTING THE MARINE SPREAD
Executing a project in mid-winter requires a special mindset. The days are short and there is a limited weather window for executing overboard works and offshore lifting operations. Conbit analyzed various options to advise the client optimally. In consultation with the client, the best mix between costs, availability and operational suitability was chosen. This resulted in choosing the DP2 crane vessel the Normand Reach.
Conbit designed a procedure involving a series of rigging and lifting handovers using several different sling configurations to move the tanks from their suspended position under the platform onto the supply vessel. The new replacement tanks were moved in the opposite direction.
The most critical step in the whole operation was the hand-over of the suspended tanks to the offshore crane. The same was true of the reverse procedure with the new tanks.
The contractual deadline for finishing the project was set to 31-01-2017, which meant executing the project in mid-winter. As the North Sea is infamous for its rough winters, the challenging weather was our main focus during project preparation.
The most weather-dependent activity was the hand-over between the platform and the vessel. We arranged all the steps and equipment in such a way that the two tanks could be replaced in series or in parallel (i.e. simultaneously). Thus, we could optimize the offshore planning to the weather forecast at the time of project execution.