Study of Fluid-Structure Interaction (FSI) On Benfield Solution (BS) Line Using ANSYS

This research work investigates the fluid-structure interaction between Benfield Solution (BS) fluid and Benfield Solution (BS) vertical pipe. The study involved static and dynamic characteristic of BS Pipe when pipe subjected hydrodynamic load. The static load modeling determines the frequency at the highest deformation by using baseline velocity of fluid. The dynamic loading is exerted to the pipe to see the effect of flow velocity to the severity to the pipe. The dynamic characteristic of pipe is done at three different fluid velocity magnitude based on plant operating mode. The problem identified in this research is when there is an excessive vibration which suspected caused by fluid-induced vibration (FIV) had caused the pipe trunnion support to have a crack at its trunnion support. The crack propagates and caused BS fluid leakage at the weldment between pipe and the trunnion. From visual inspection, the pipe is vibrating horizontally with high magnitude and low frequency with natural frequency higher than 10Hz. The vibration by FIV had caused the trunnion support hit the base frame excessively and exceed it tolerance value which is 10mm. This research is to study the interaction of fluid dynamics and the pipe structure for the determination of the fatigue life of the Benfield pipe. This pipe is modeled using ANSYS Structural Analysis and solved by Modal Analysis to see the highest deformation and maximum stress profile at the fractured trunnion. The simulation result will be validated using Caesar II by Group Technical Solution(GTS) report. In a nutshell, when the BS pipe vibrates approaching to 36.741Hz, the highest deformation of Benfield pipe by 13.01 mm is recorded since the acceptable tolerance between trunion and base frame is 10 mm, mode 4 exceeds this value and cause trunnion deterioration after 2.565e+4 cycles. The area of deformation is occurred at the lower part of the pipe, which resulting the actual pipe leakage area of the project. From that point, maximum stress exerted onto the pipe is validated with GTS data. There is slightly lower value in ANSYS stress analysis due to some reasons, which mainly caused by different scope of study.