Research On Internal Detection Technology For Spanning States Of Subsea Pipelines

Suspended span refers to the loss of foundation soil support of submarine pipeline due to current erosion or seabed fluctuation,which changes the load form and stress state of pipeline.It is the direct cause of many submarine pipeline rupture accidents.When the ocean current flows through the suspended span pipeline,it will periodically release the vortex,causing the vertical "vortex induced vibration" and even violent resonance of the pipeline.With the increase of span length,the bending and sinking of suspended span pipeline will intensify,and finally rupture due to stress overload.According to the bending and vibration characteristics of submarine suspended span pipeline,this paper proposes a submarine pipeline suspended span detection technology based on spherical internal detector,which has the advantages of quasi real-time,not easy to jam and high efficiency.The main innovative research includes:1.The static and dynamic analysis models of submarine pipeline are established in this paper.Through analytical derivation and simulation calculation,the author deeply studies the particularity of the suspended span state of submarine pipeline different from other in-situ states in theory.This paper points out that the suspended span of submarine pipeline has two main characteristics: bending and vibration,and establishes the free vibration equation of submarine pipeline.Combined with the effect of submarine water environment on pipeline,the author studies the influence of vortex induced vibration on submarine suspended span pipeline.2.The author designed a spherical inner detector specially used to detect the suspended span state of submarine pipeline.This paper studies the composition,trafficability and disturbance of the spherical internal detector in the pipeline,analyzes the rolling stability of the internal detector,and experimentally verifies the influence of the rolling stability on data acquisition and processing.Combined with the above points,the optimal size range and internal component distribution of the spherical inner detector are finally determined.3.The author puts forward the method of using spherical inner detector to detect the suspension span of pipeline,including bending detection and vibration detection.In the bending detection,the sensor layout and algorithm design scheme are given,which can detect the vertical up bending and down bending of the pipeline;In the vibration detection,the method of how to extract the vibration information of suspended span pipeline from the rotation acceleration signal is explained.