Analysis Of Structural Reliability Of Subsea Manifold And Software Development Of Reliability Assessment

The subsea manifold is one of the key components of the subsea production system,which plays the role of collecting production fluid.The subsea manifold mostly uses subsea mudmat as the basic support structure,and subsea control module performs the function of opening and closing valves on subsea manifold,and the failure rate of the underwater control module is high.Aiming at the problems of poor foundation stability,complex failure mode and low accuracy of reliability evaluation model of subsea manifold,this paper analyzes the stability and structural reliability of subsea manifold from three aspects: subsea mudmat,subsea manifold structure and subsea control module structure,and develops the reliability evaluation software of subsea manifold structure.Based on the investigation of the historical failure data and the analysis of the general configuration of subsea manifold system,define the research objects of subsea mudmat,subsea manifold and subsea control module.On the basis of existing reliability analysis methods,through comparative analysis,this paper adopts FMECA and FTA methods for reliability analysis,and uses fuzzy comprehensive evaluation method to calculate the event probability of the bottom of fault tree.The stability of the subsea manifold depends on the ultimate bearing capacity of subsea mudmat.This paper analyzes the ultimate bearing capacity of a subsea manifold foundation in South China Sea by API RP 2GEO formula and numerical simulation of soil mechanics,and study the failure law of the soil at the bottom of the foundation to complete the stability analysis of the foundation of subsea manifold.Based on the general configuration analysis of the structure of subsea manifold,use FMECA to define the failure mode,cause and effect of the key components of the underwater manifold structure system,and establish the fault tree model with "subsea manifold structure failure" as its top event.Then,use expert evaluation method and fuzzy mathematics theory to determine the probability of the bottom event of the fault tree.Through qualitative and quantitative analysis of the fault tree,obtain the probability of the top event "subsea manifold structure failure".And,realize the failure modes which have great influence on the occurrence of "subsea manifold structure failure" by the importance analysis.Based on the general configuration analysis of the structure of subsea control module,take the wedge dock-locking subsea control module as the research object,using FMECA,FTA,expert evaluation method and the fuzzy mathematics theory,obtain the probability of occurrence of the top event "structural failure of the subsea control module" and realize the failure modes which have great influence on top event by qualitative analysis,quantitative analysis and importance analysis of the fault tree.According to the reliability assessment models of the structure of subsea manifold and subsea control module established in this paper,develop the reliability assessment software of the structure of s ubsea manifold with C#,and realize the calculation of key reliability indexes of subsea manifold.