Launch and recovery of a work class ROV through wave zone in small offshore service vessel

The deployment of remotely operated underwater vehicle (ROV) from a small offshore service vessel (OSV) based on single point mooring system (SPMS) method is recently adopted in offshore renewable energy sector. However, the tension spike in wire, also known as snap load, often occurs when the ROV passes through the wave zone in launching and lifting operation of deployment. In this study, a practical numerical model for predicting wire tension during launch and recovery of ROV is developed and validated by wave flume test of a 1:10 scaled model. The numerical simulations reveal that the ROV deployment at vessel stern along with an appropriate reduction of horizontal distance from the hull are reliable safety strategies for reducing wire tension. By adopting the new deployment strategy, the annual operational capacity can be expanded by approximately 6% when the safe operational limit of ROV under a significant wave height of 1.25 m. Based on the comprehensive numerical simulation, the newly developed safe operating envelope provides a further guidance for onboard ROV operation in the O&M of offshore wind farms.