Effects of Ship Propulsion Shafting Alignment on Whirling Vibration and Bearing Temperature Response

Ship’s propulsion shafting is one of the main sources of ship vibration and noise. The shafting, whirling vibrations, and alignment are important factors that affect the comfort, stability, and reliability during a ship’s navigation. However, the mechanism of the interacting of the both factors is not fully revealed. In this paper, the effect of shafting alignment on whirling vibration and the bearing temperature response is studied by experiment. The test scheme is designed reasonably according to the theoretical analysis. The results show that the horizontal component of the shafting whirling vibration can be effectively reduced by adjusting the shafting alignment state while the vertical component is not. The shafting axis balancing position (SABP) slightly moves upward in high speed, which should be considered in the dynamic alignment design of the shafting, especially for the high-speed shafting. Little ABSB (the angle between the shafting centre line and the No. 1 bearing centre line) is beneficial to the stable operation of shafting, while appropriately increasing the ABSB and bearing load is beneficial to reducing the shafting whirling vibration. By balancing the relationship between bearing load and ABSB, the performance of whirling vibration and bearing temperature response can be optimized.

Measurement and analysis of vibrations - evaluation of the criteria of acceptance ISO Standard 10816-6

During the reception and / or delivery tests of a ship, vibration measurement and analysis is made to the propulsion line in order to evaluate and predict the condition of the machinery. The values taken during the measurement of the vibrations are evaluated with the acceptance criteria provided by the standards. International Standard ISO 10816-6 (1995) focuses on reciprocating machinery with power of greater than 100kW, is used by both analysts and manufacturers of propulsion machinery for ships. Through this work, we intend to evaluate the acceptance criteria of this norm in boats smaller than 100 meters. At the end of this work it is concluded that the standard must be updated, indicating and differentiating the acceptance criteria for machinery taking into account its type of anchorage to the structure (flexible or rigid), boats with length less than or greater than 100 meters and the Ship building material (Aluminum, Steel or Composite material).

Experimental Research on the Vibration of Ship Propulsion Shaft under Hull Deformation Excitations on Bearings

With the development of ship enlargement, the problems of coupling vibration between hull and propulsion system and vibration transmission via bearings are more and more prominent. Based on the theory of shaft vibration and the experimental system for dynamic characteristics of the shaft, an experiment plan about propulsion shaft vibration under dynamic excitations is designed in this paper. The performance of propulsion shaft vibration under hull deformation excitations applied on intermediate and stern bearings is studied. Hydraulic excitations in horizontal and vertical directions on the intermediate bearing and stern bearing of the experimental model of propulsion shaft are considered in this paper to simulate hull deformation on bearings of the ship. Vibration characteristics of the shaft under different excitations are gained and coupling effects are discussed. Moreover, the influences of amplitude and direction of excitations on bearings and the shaft rotation speed on the vibration of propulsion are studied. The results show that aiming at improving the safety and reliability of navigation, the hull deformation, especially the horizontal hull deformation excitation on the intermediate bearing, is not neglectable and should be considered during primary design. Also, rotation speed and resonant frequency are needed to be well designed with the frequencies of hull deformation excitations.