Research On Safety Reliability And Risk Assessment Of Submarine Pipeline

Reliability analysis and risk assessment of submarine pipeline are important research of applied theory and technology used for evaluating reliability, safety and prospective life of submarine pipeline in service process including many risk factors, furthermore, preventing effectively submarine pipeline failure, increasing submarine pipeline reliability, lengthening submarine pipeline life. The major contents are summarized as follows:(1) Based on the obtained research achievement, the mechanisms of submarine pipeline failure, the influences of various typical loads on submarine pipeline failure, and the influences of multifold factors on submarine pipeline strength were attained by means of the data collection and academic deduction. The ultimate state equations of submarine pipeline were established in accordance with the basic failure forms, submarine pipeline strengths and loads. Because submarine pipeline strengths and loads are random, according to the probability and reliability theory, the computing method of failure probability of submarine pipeline was confirmed. The distributions of typical parameters were obtained through academic deduction, relational empirical formulas, and analysis of probability models of typical loads. The factors affecting submarine pipeline failure probability were determined, and the influence law of randomness of submarine pipeline strengths and loads on submarine pipeline reliability were obtained.(2) According to the tensile test result of 16Mn submarine pipeline, the parameter's randomness such as defect size and submarine pipeline strengths were analyzed. Then, Monte Carlo numerical method was used to calculate reliability assessment for welded joints of submarine pipeline steel in Chengdao oilfield with surface flaw at the weld toe based on British standard 7910.The failure probability of submarine pipeline containing defects was worked out. The regularities and parameters of distribution of various submarine pipeline strengths, and the influences of randomness of evaluation parameters on failure probability of submarine pipeline were achieved.(3) The vibration equation of free spanning submarine pipeline was established, the natural frequency and allowable length of free spanning were solved. Influence of water flow velocity, boundary conditions and axial force on vibrating natural frequency of submarine pipeline were obtained. The numerical simulation model of seismic for submarine pipeline was established and seismic response analysis of submarine pipeline was carried on. Then influence law of damping ratio and site types on seismic response of submarine pipelines was obtained.(4) The tension-tension fatigue test of 16Mn submarine pipeline was designed. Based on the probability method of statistical analysis, the experimental data were analyzed and the formula of fatigue life estimation was obtained. The fatigue curve of welded joint for submarine pipeline was corrected, then the P-S-N curve of welded joint under different survival rate were achived. Various formulas of fatigue life were analyzed and simple but accurate for the engineering application for life prediction method was selected. Base on the simulation fatigue test of submarine pipeline, the fatigue life of riser under the wave loading were estimated by using P-S-N curve.(5) By acquiring and analyzing data of submarine pipeline system for Chengdao Oilfield, the model of fault tree analysis is set up and main factors caused by submarine pipeline failure were founded. The fuzzy compositive quantitative risk assessment method and model of submarine pipeline based on fault tree analysis were established. The influence grade and occurrence probability of risk factors of submarine pipeline were analyzed synthetically, and these risk factors include human error and others which are difficult to be quantified or short of data. The risk assessment of a practical submarine pipeline was completed in order to verify the risk assessment model. The result shows that the risk assessment model is reasonable and practical.(6) According to the aforementioned achievement, the software"Reliability and Safety Analysis of Submarine pipeline"was developed and applied to evaluate the security of submarine pipeline successfully based on dynamic database, optimizing filtration technology and computer graphics.