Polymetallic nodules found in the deep ocean basins contain many economically valuable metals and are viewed as potential resources to supplement depleting onshore reserves and tackle increasing demand. The present work focuses on the preliminary design through analysis of a bottom weighted rigid riser which would form a part of the future full scale prototype nodule mining system under development by the National Institute of Ocean Technology (NIOT), India, operating in a water depth of around 6500m in the Central Indian Ocean Basin. A semisubmersible platform is chosen as a surface support vessel and the hydrodynamic analysis of a conceptual semisubmersible platform is carried out with WAMIT [3] to determine the heave Response Amplitude Operators (RAOs). The initial riser diameter, material grade and wall thickness configuration are arrived at using basic engineering principles and semi-coupled dynamic analysis of the platform riser system is carried out using ORCAFLEX [8] software to determine the loads imposed on the riser. The wall thickness is optimized to meet requirements of offshore standard DNV OS F 201 [6]. Vortex Induced Vibration (VIV) and Fatigue Analysis are then carried out using ORCAFLEX.

This content is only available via PDF.
You do not currently have access to this content.