A Methodology for Assessment of Internal Flow-Induced Vibration (FIV) in Subsea Piping Systems

A methodology is presented for assessing internal flow-induced vibrations (FIV) in subsea piping systems. Finite Element (FE) models are constructed for the subject piping systems, including insulation, internal hydrocarbon weight and added mass of the surrounding sea water. Operating vibration data are measured using ROV-deployable accelerometer loggers clamped directly to the piping systems. The measured data are processed, analyzed and used for two purposes: model verification and dynamic response correlation. Modal parameters are extracted from the measured data and compared to the modal parameters computed from the structural FE model. The model is refined until the frequencies and mode shape errors are within the desired tolerance. The measured data are then used to derive a representative forcing function for use with frequency-domain random response analysis. The forcing function is derived such that the properties of the predicted vibration spectrum match those of the measured vibration spectrum for all measurement locations. The method presented herein provides a novel semi-empirical technique for calibrating FE models to make fatigue life predictions for subsea piping systems using measured vibration data.