Submarine pipeline design method based on suspended-span vortex-induced vibration fatigue life

Abstract

The invention discloses a submarine pipeline design method based on the suspended-span vortex-induced vibration fatigue life. The submarine pipeline design method comprises the following steps that firstly, the permissible value of the pipeline hoop stress is calculated; secondly, primary design is conducted to determine the pipeline wall thickness; thirdly, the inherent frequency of a suspended-span structure of a submarine pipeline and the vortex-induced vibration load frequency of the submarine pipeline are calculated; fourthly, it is judged whether the suspended-span structure of the submarine pipeline resonates or not; fifthly, the reduced velocity is calculated; sixthly, the suspended-span vortex-induced vibration amplitude of the submarine pipeline is determined; seventhly, the suspended-span vortex-induced vibration stress range of the submarine pipeline is calculated; eighthly, the number of the permissible fatigue cycle times of the submarine pipeline is determined; ninthly,the suspended-span vortex-induced vibration fatigue life of the submarine pipeline is calculated; tenthly, it is judged whether the designed life requirements of the submarine pipeline are met or not;eleventhly, design improvement is conducted; twelfthly, the submarine pipeline design based on the suspended-span vortex-induced vibration fatigue life is completed. The submarine pipeline design method provides a technical support for China to establish submarine pipeline design standards based on the life.

Description

Technical field [0001] The invention belongs to the technical field of submarine pipeline design, and specifically relates to a submarine pipeline design method based on the fatigue life of overhanging vortex-induced vibration. Background technique [0002] Submarine pipelines are the main form of offshore oil and gas gathering and transportation with the advantages of continuity, speed, and large transportation volume. Due to the influence of ocean currents, navigation, fishery production, earthquakes and other factors, the service conditions of submarine pipelines are far more severe than onshore pipelines, and their safety issues need more attention. This is not only related to the normal production of my country’s offshore oil, but also related to my country’s offshore oil production. Major issues such as the security of petroleum strategic resources and marine environmental pollution. [0003] Submarine pipelines are affected by the seabed and ocean currents, and it is inevita...

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Problems solved by technology

[0005] However, the DNV-RP-F105 specification of Det Norske Veritas DNV is difficult to apply in the fatigue life prediction of submarine pipeline spans in my country. Some of the processing methods are too conservative, such as considering the forced vibration frequency of the span when it is subjected to vortex-induced vibration according to the resonance frequency; the third is that the analysis process is complicated and involves a lot of data, because the actual submarine pipeline service status is always changing with the environment, Therefore some data are difficult to determine

[0006] At present, there is still a lack of design methods for submarine pipelines that specifically address the fatigue life of suspended spans due to vortex-induced vibration. In the design of submarine pipelines, the safety of suspended spans is analyzed from the perspective of avoiding vortex-induced vibrations, and the fatigue damage accumulation of suspended spans is not considered. This is obviously too conservative for life-based structural design of subsea pipelines

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