MARILEE
The vessel, an oil tanker of panamax size, had increased vibration levels at full speed. The captain had ordered a speed restriction of as much as 1-1.5 knots below specified full speed due to the high vibration levels. ÅF was commissioned by Marinvest AB, Göteborg, to carry out vibration measurements and to propose suitable solutions for reduction of the vibration levels.
Solution
During a three day voyage vibration measurements at different speed conditions, with and without solutions proposed by the ship yard and the engine manufacture were carried out. During the measurements it was obviously that the main engine, the turbo charger and the exhaust pipe were "working together" at the critical revolutions. The vibration study showed that the vibration isolation of the main engine exhaust pipe strongly affected the vibration levels. Principal solutions based on the measured movements of the turbo charger and exhaust pipe were proposed by ÅF. Marinvest decided to implement the solution with a stiffer vibration isolation of the main exhaust pipe and the existing vibration isolators were complemented with two isolators of the same type. By this solution the main exhaust pipe vibration isolation was not only stiffer in vertical direction but also in torsion.
Results
The crew judge that the vibration levels have been lowered significantly in the critical speed interval. The ship operates now in the highest speed interval without high vibration levels occur at the bridge.
Customer: Marinvest AB
Object: Oil tanker of panama size
Commission: Vibration measurements and proposal of suitable solutions of the problem