Research On Vibration And Noise Reduction Of Ocean Engineering Pipelines

The rapid economic and social development entails the increasing consumption of energy in all nations. Land resources alone have become difficult to meet the needs of human beings, so more and more attention is paid to the vast ocean. Efforts have been stepped up to explore and develop ocean resources, and needs for offshore structures grow rapidly. Offshore personnel have higher requirements on the comfortableness of working condition, rest area and residence, and have a better awareness of healthy, so vibration and noise reduction of ocean engineering has been attracting greater attention. The International Maritime Organization and institutions of many countries have formulated highly rigorous standards on vibration and noise. The revision of the IMO Code on Noise Levels on Board Ships (DE56) has been enforced, placing higher requirements on vibration and noise reduction of board ships and ocean engineering.The vibration and noise reduction of pipelines, which are an integral part of offshore structures and an important means of noise radiation and vibration transmission, plays a significant part in controlling the vibration and noise of ocean engineering. Vibration isolation mass is a rigid vibration damping method, whose research focus is placed on the plate component. This paper installs different vibration isolation masses in pipelines of different specifications and builds physical experimental models to test and analyze the general rules of vibration isolation masses in pipeline structures of ocean engineering.Square steels were installed as vibration isolation mass in reference to plate structures, and theoretical analysis was made about the working principles of vibration isolation mass in plate structures. Bending wave was the main wave of the vibration transmission in pipelines, and the bending wave’s transmission loss formula was derived according to a wave equation. Pipelines of different sizes were established and different physical experimental models were built with different vibration isolation masses. One end of the pipeline was hammered and knocked forcefully to generate vibration; an acceleration sensor was used to pick up the vibration; and eventually effects of the vibration isolation mass on reducing the vibration of gas-and liquid-filled pipelines were analyzed.Experimental testing and data analysis found the transmission characteristics of vibration waves of pipelines. The measured data on the output end and the input end was compared to obtain the difference in vibration level. The average value on some measuring points of the output end was calculated as the mean vibration level difference. Calculations were also made to see the differences in vibration level on different measuring points with or without vibration isolation mass, finding the change of vibration level difference along with the changing ratio of vibration isolation mass to the pipeline quality per unit length. A variety of working conditions were analyzed by calculating the one-third octave bands spectrum, obtaining the inhibitory effect of the vibration wave in different frequency bands. Research results indicated that in the same pipeline, vibration damping effects improve with the increase of vibration isolation mass; for pipelines of different sizes added with different vibration isolation masses, vibration damping effects improve with the increase of the ratio of vibration isolation mass to pipeline quality per unit length; the vibration isolation mass achieves good effect in inhibiting the high frequency of the vibration wave but no obvious vibration-reducing effect in low-frequency areas. Analytical results offer some value of reference for the vibration and noise reduction of pipelines.For the damping effect of vibration isolation mass in fluid-filled pipelines and gas-filled pipelines, the transmission loss rules of the vibration wave were basically identical. In terms of frequency spectrum, better damping effect was achieved in mid-and high-frequency zones, offering some value of reference for the vibration reduction of fluid-filled pipelines.The research findings of this paper offer some value of reference for the vibration and noise reduction of ocean engineering pipelines. When laying pipelines, flange connection can be applied reasonably to replace welding, so as to reduce vibration and noise. Parameters of vibration isolation mass can also be changed to meet the requirements on vibration and noise reduction. Eventually, research prospects and applications about vibration and noise reduction based on vibration isolation mass were envisioned, and issues in need of attention were proposed.