Strength of submarine hoses in Chinese-lantern configuration from hydrodynamic loads on CALM buoy

Catenary Anchor Leg Moorings (CALM) buoys are offshore structures that have been used for offloading, loading and discharge purposes. In this study, dynamic analysis is carried out on the submarine hoses attached to a CALM buoy and moored by six mooring lines in a water depth of 23.0 m. Two submarine hose-strings in Chinese-lantern configuration are attached underneath the buoy. Three environmental conditions are considered, representing West Africa Sea, North Sea and Gulf of Mexico (GoM), respectively. Hydrodynamic simulation using ANSYS AQWA is first conducted to determine response amplitude operators (RAOs) of the buoy. Coupled dynamic models, where both buoys and hoses are included, are developed using Orcaflex. Parametric studies are conducted to investigate the effects of hose hydrodynamic loads and flow angles on the structural behaviour of the hoses, including bending moments, effective tension and minimum bend radius. From the study, a guidance dynamic amplitude factor of 2.0 considering hydrodynamic loads on hose DAF(hose) is proposed.