Identification of the Operating Conditions of the Main Engines of a Fast Support Vessel (FSV)

Abstract

To avoid operational failures in the four main propulsion engines of a fast support vessel, which could place at risk its structure, and consequently also the crew on board, measurements were taken during the vessel’s sea trial aiming at identifying excessive vibration and resonance in the engines. Data were acquired in two stages: free navigation, with 80% MPE load and during the MPE start-up period, considering a 600–1800 rpm variation in rotational speed. The measuring equipment and the points to be monitored were chosen following international standards. The data obtained were analyzed using specialized signal-processing techniques and the results were evaluated as follows: in the free navigation condition, the overall values of the vibration spectra were compared to the limits established by classification societies; for the MPE start-up period, waterfall plots were analyzed to identify the rotation harmonics that excite the engines’ natural frequencies. The final results showed that two MPEs had excessive vibration, and that the main orders of excitation were 1× rpm, 1.5× rpm, 2× rpm, 4× rpm, and 4.5× rpm and the transient analysis identified that the 2× rpm, 4× rpm, and 4.5× rpm orders of excitation caused resonance in the heads and bases of the MPE cylinders.