Experimental Research Of Vibration Isolation Mass In Vibration Damping And Noise Reduction Of Pipeline In Ocean Engineering

As many countries have been attaching more importance to marine resourcesdevelopment, the demands of ocean engineering structures are growing up quickly.And with the improving of the request of human work environment, the vibration andnoise problems in ocean engineering have been drawn more and more attentions.Don’t just the IMO and many other organizations in some countries including Chinahave established strict standards to restrict the vibration and noise in oceanengineering. The IMO new criterion (DE56Draft) will be enforced on July1,2014,and the requirements of damping and noise reduction in ocean engineering will behigher and stricter.The pipe system, an indispensable part of the ocean structures, is an importantpathway to transmit vibration and radiated noise in ocean engineering. The vibrationdamping and noise reduction of pipeline system is an important part of vibration andnoise problems in ocean engineering. The technique of vibration isolation mass whichhas been ripe for plate component is gotten attention to be used in pipeline system.Theoretical analysis and numerical simulation method has been used to research onvibration isolation mass for pipe by some scholars. In this paper, a physical model isset up to measure and analyze the data of transmission loss. At last, somegeneral rules and the application prospect of vibration isolation mass for pipe willbeen shown.Firstly, taking the typical structure of plate with quadrate steel beam for example,analyses the general principles of vibration isolation mass for vibration damping andnoise reduction; Based on wave propagation，the formulations of transmission loss forflexural wave (the primary cause of the structure-borne sound) of an infinite pipe witha vibration isolation mass are derived. Then, setting up the physical model of pipewith vibration isolation masses to measure and analyze the data of transmission loss when vibration wave spreads in the gas pipes and liquid pipes.To measure and analyze the data, getting the vibration difference of measuringpoints front and back of the masses; contrasting the vibration difference of eachmeasuring point on the pipe with masses and the pipe without masses. It is shown thatthe isolation mass is very good at reducing the vibration wave transmission inintermediate and high frequency domain, but there is no obvious effect in lowfrequency domain. The larger the radius of inertia and the bigger the weight ofvibration isolation mass，the better the damping effect. Compare with one mass, theeffects of several masses has a lower detection limit frequencies. The distance ofvibration isolation masses plays an important role in the vibration damping of pipe.For the same sections, three parallel and equally spaced masses would not be of greatvibration effect than single mass. When the distances of three masses are different, thevibration effect would be better than three parallel and equally spaced masses.There are similar disciplines of transmission loss when vibration wave spread ongas pipes and liquid pipes with masses. For liquid pipes，the effect of each point onpipes with masses and pipes without masses is lower than gas pipes.This is mainly because the ratio of the mass of isolation masses and unit length ofpipe become smaller, and the influence of the masses for the vibration of pipe isweaker.The study has some reference value for the vibration and noise reduction ofpipeline system in naval architecture and ocean engineering. If conditions allow whenpipe constructed, we can use flange (vibration isolation mass) connectionappropriately instead of welding and transform section sizes, space and amount offlanges to get the good effect of vibration damping and noise reduction. At the end ofthis article, providing an outlook of research and application of the vibration isolationmass and pointing out some problems need to solve in the future.