Vibration Analysis Approach to Mitigate Excessive Vibrations in Main Steam Lines of a Power Station

Abstract Mechanical vibration is one of the inherent characteristics of piping systems under dynamic loadings and can cause mechanical problems and even failure if not fully understood and mitigated. In this paper, vibration analysis and a mitigation strategy to prevent vibration failures in the Main Steam Lines (MSL) of an operating power station are presented. The vibration analysis is performed in the following stages: 1) identifying critical locations to install vibration sensors for the vibration data acquisition, 2) post processing the recorded vibration data using Fast Fourier Transform (FFT) to convert the data from the time domain to the frequency domain, 3) building a Finite Element (FE) model representing the MSL and its connected subsystems using pipe elements in commercial FE software and perform pre-stressed modal analysis followed by harmonic analysis, 4) validation of the FE model by comparing the Harmonic Response extracted from the FE model against the vibration measurements, 5) applying different mitigation strategies by modifying the existing and adding new supports to alter the system’s flexibility leading to a significant reduction in the vibration response, and 6) identifying the allowable vibrational velocities via ASME OM for Operation and Maintenance of Nuclear Power Plants for field monitoring. The proposed changes and additions to the piping supports’ configuration resulted in a significant reduction in the vibrational response of the system that is expected to reduce the potential for fatigue failures.