Pipes used for transporting high velocity pressurized fluids often operate under time-varying conditions due to pump and valve operations. This can cause vibration problems. In the present work, a finite element formulation for the fully coupled dynamic equations of motion to include the effect of fluid-structure interaction (FSI) is introduced and applied to a pipeline system used in nuclear reactors. The fluid finite element model is based on flow velocity as the variable. The response of fluid filled pipelines to valve closure excitation has been studied. The model is validated with an experimental pipeline system. © 2003 Elsevier B.V. All rights reserved.