Executing a project during the winter requires a special mindset. Daylight is short and there is a limited weather window for executing overboard works and offshore lifting operations. Conbit analyzed various marine spreads to find the best mix of costs, availability and operational suitability. This resulted in the client's final choice to hire the DP2 vessel Normand Reach.
Conbit analyzed several alternative solutions for the tank-replacement procedure. The chosen procedure involved replacing the tanks and their entire supporting structures in a long series of rigging and lifting steps using several sling configurations. As the tanks were so heavy, we needed to identify sufficient strong points and rigging equipment to execute the procedure effectively and safely.
The most interesting, and weather depending step in the procedure was the in-air hand-over of the suspended tanks to the offshore lift. 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.
With the old tanks we could use slings in an easy way because it did not matter that we damage these old tanks. With the new ones this was more challenging. The tanks are isolated with a thin metal covering shelf. The slightest impact will damage them. Therefore we designed a dedicated lifting frame on top of the new tanks. Keeping the frame above the tanks in all the phases of the lifting procedure was the main design challenge.
The client complimented Conbit on its performance. Conbit is known for its professional offshore preparation and execution of lifting-related projects. Our philosophy “Prepare well and execute smoothly” is the secret.