The goal of this work was to develop a computational approach supported with measurement results for the evaluation of vibrations of large scale piping excited basically by the hydrodynamic forces with emphasis to the growth rate of hypothetic cracks that inevitably exist in any engineering structure. The vibration analysis has been performed using ANSYS procedures where the loading applied as variable internal pressure was scaled in order to match the data obtained at measurement points. The lifetime evaluation has been performed in terms of the maximum number of loading cycles by using the SACC software. The results of computations have been used practically in preparation the Safety analysis report of the 2nd unit of Ignalina NPP.