SEAKEEPING EVALUATION OF SHIPS FOR OPERATIONAL PLANNING IN THE GULF OF GUINEA

Abstract

This paper evaluates the sea-keeping characteristics of a Platform Supply Vessel (PSV) for operational planning in the Gulf of Guinea according to the respective international requirements or standard criteria. The ship’s design and operation characteristics were examined, the characteristics of the specified sea environment in which the ship should perform its mission were assessed, the impact of the specified sea environment on the design and operation of the ship was evaluated and ultimately, the operational criteria that should not be exceeded, so that the ship can perform its mission effectively was determined. Structural Analysis and Design Computer-Aided Design (SACS CAD) Software was employed to model the ship design and it was subjected to the environment in which it is to operate. The Joint North Sea Wave Project (JONSWAP) spectrum was used to model the local wind sea wave with Orca Finite Element Analysis of Flexible Systems (ORCAFLEX). This analysis showed the dynamic movement of the Platform Supply Vessel (PSV) in the various degrees of freedom (heave, surge, sway, yaw, roll, and pitch). Broad-based results showed that the PSV is fit to be operational. This was because of the various tests that were conducted for normal conditions. The various degrees of freedom offset exerted by the PSV were below the tolerance limit of platform supply vessels (10% of water depth of 100m=10m). The results obtained were for the south, the heave offset of 1.6032m and surge offset of 2.1507m. For the southwest, the heave offset of 1.5033m, the surge offset of 1.0712m, and the sway offset of 1.0753m. For the west, the heave offset of 1.068m, and the sway offset of 1.2114m. Local Sea wind wave in the south direction (180°) exerts the most environmental loading on the designed PSV. This was because of the result obtained for the extreme condition (heave offset of 1.9571m and surge offset of 1.4107m. The PSV stability parameters were also obtained as summarized in Appendix C and known to be within the limit of acceptability and validated by comparing the righting lever, GZ, of the designed PSV in Figure 16 with that obtained by marine.info (2021). Both righting levers, GZs were above the 30 degrees requirement of UKMCA (2008) criteria for PSVs. The GZ obtained was 62.8 degrees which should not be exceeded to prevent the PSV from capsizing. The study contributes to the body of knowledge surrounding seakeeping evaluations of PSVs and serves as a foundation for evaluating the design and performance of these vessels in the demanding offshore environment