Structural simulation of a Horizontal Pressure Vessel for predicting stress under extreme weather conditions

Offshore containers are exposed to the movement caused by wind, ocean currents, and unpredictable weather conditions so a good structural resistance is required for them. A dynamic analysis has been developed using Abaqus/Explicit to study the structural response of a horizontal pressure vessel mounted in Floating Production Storage and Offloading (FPSO) topsides in the Gulf of Mexico (GOM) coast. The model includes fluid behavior of crude oil inside the container for which the linear Us-Up Hugoniot equation of state is used. The viscosity of the oil was varied according to temperature. A single adaptive meshing rule is also used to prevent distortion of fluid elements.
The structural resistance of the horizontal pressure vessel must satisfy the ASTM, ASME and API Standards to prevent catastrophic failure under extreme weather conditions. The vessel is made of a SA516-70 steel, for which mechanical properties are taken into account. The analysis considers thermal effects of fluid and weather conditions by using an appropriate heat transfer coefficient. Wind velocity is expressed in terms of an external pressure load. Stress results have been compared with a stress distribution obtained from a simulation of a pressure vessel located on a fixed platform. This type of simulation is very important since no historical data exist for this FPSO location.