AS 3764-1990

Sets out procedures for gathering and presenting data on hull vibration in single-shaft and multiple-shaft sea-going merchant ships, and for vibrations of propulsion-shaft systems as it affects hull vibration. This Standard is technically identical to and reproduced from ISO 4867:1984.

This International Standard establishes uniform procedures for gathering and presenting data:a) on hull vibration in single or multiple-shaft sea-going merchant ships;b) for vibration of propulsion-shaft systems as it affects hull vibration.Such data are necessary to establish uniformly the vibration characteristics of hull and propulsion-shaft systems and to provide a basis for design predictions, improvements and comparison against vibration reference levels.The procedures, where applicable, can also be used for inland ships and tug boats. In special cases, where objectionable vibration is found to exist, specific investigative studies may be required.This International Standard is concerned with:a) vibration of the main hull girder and superstructure excited by the propulsion system- at shaft rotational frequency,- at propeller blade rate, harmonics of blade rate and- at frequencies associated with the major components of machinery;b) excitation of the propulsion shaft and main machinery system.It does not deal with other aspects of ship vibration at this time. Local vibration is dealt with in ISO 4868.Anchor drop-and-snub tests in calm water may be an effective means of obtaining the first few vertical hull modes of vibration and their damping constants (see warning in 4.5.5).Detailed design information on the ship is required to assist in developing empirical constants useful in evaluating the vibration of hull and machinery vibratory characteristics.This International Standard gives general principles of vibration measurement on board ships to improve vibration engineering. Therefore, in individual cases, items to be measured may be selected or added to meet the aims of the vibration measurement of each ship.