| The techniques for aging oil pipeline including risk analysis, safety comprehensive assessment, reliability analysis, and decision-making for maintenance, et al, were studied in this dissertation; and the safety assessment technique was introduced in the safety inspection and management for aging oil pipeline, which provided a kind of powerful safety assurance technology for the safe operation of aging oil pipeline. In this paper, structural safety assessment technique and decision-making for maintenance technology of aging long distance oil pipeline were lucubrated based on the project"Research on Digitized Technology of Safe Operation of Oil&Gas Pipeline Structure"listed by STATE ADMINISTRATION OF WORK SAFETY. Considering the randomness, fuzziness, nondeterminacy, et al; based on stochastic reliability theory; an integrated technology system of structural safety reliability analysis and control decision of aging oil pipeline was established primarily, including pipeline structural corrosion damage, dynamic reliability analysis, durability assessment, residual life prediction, inspection, and maintenance decision&control, et al. It could be an guidance for the aging oil pipeline safe operating management; and under its help, pipeline inspection cycle be optimized, life-span cost be reduced, the aging pipeline's safety, reliability, fitness, durability and integrity be ensured, and aging pipeline real-time risk supervision be achieved, and as a result it helps to improve pipeline safety and reliability during the service life. The main work is summarized as follows now:1 Research on Safety Comprehensive Assessment System for Aging Oil Pipeline Considering such characters of aging oil pipeline system as super-dimensionality, complexity, opening, dynamic, et al, the concept of great complex system of aging oil pipeline system was provided, and aging pipeline system safety was analyzed according to those theory: pregnanting accident-environment, accident-cause, accident-result, et al. The basic content of the character of aging oil pipeline's risk and safety comprehensive assessment were discussed based on the human-machine-environment system safety of aging oil pipeline; and five main factors which cover nearly all aspects of aging pipeline system were determined, including the third-party damage, corrosion, safety allowance, false operation and natural disaster; and an integrated safety index system for aging oil pipeline was set up. An engineering assessment index system of aging oil pipeline's spanning section was presented in the view of hydrogeology, earthquake and corrosion. The factors that influence the aging pipeline including types of natural disasters, effect mode and failure mode were introduced, the risk assessment methods were discussed and the system framework considering Natural Disaster, Content, Human/Environment and Prevention Assessment is given. Natural disaster assessment technique for aging pipeline system was studied systemically in this paper, and a natural disaster(such as flood, subsidence, landslide, wave-current, ice force, seism, fire, explosion, et al) assessment technique framework was founded. Doing research on comprehensive disaster assessment technology by combining the risk analysis method with the structural ability to resist disaster, which helped to convert the traditional assessment model of the aging pipeline natural disaster safety assessment into the modern one, and set up the foundation of quantitative assessment of aging pipeline structural reliability.2 Research on Safety Reliability Method for Aging Oil Pipeline SystemConsidering the deficiency of current safety reliability analysis methods, a fuzzy risk analysis method based on SCGM(Simple Center of Gravity Method) was presented, which created a new way for precise assessment of pipeline fuzzy risk analysis; and considering both common factors and individual factors, a integral method of the fuzzy comprehensive evaluation for oil pipeline failure based on fault tree was brought forward; a new safety comprehensive assessment model based on SPA(Set Pair Analysis) was offered by introducing SPA to the field of pipeline safety system assessment. Taking the disadvantage of traditional plane state evaluation method into account, comprehensive evaluation based on CN(Connection Number) and developing trend evaluation based on PCN(Partial Connection Number) were proposed firstly, and proven to be a three-dimensional, single specimen, dynamic, and reevaluating method.According to the difference of the internal inspecting information obtaining manner, the aging pipeline was classified for the first time as the non-internal inspection pipeline and the internal inspection one. Integrated with the up-to-date dynamic/variable weight safety assessment technique, two kinds of reliability assessment methods based on fitness for purpose were put forward separately for these two different kinds of aging pipelines. Based on aging pipeline various failure models, aging pipeline corrosion reliability analysis was carried out, and both the influence on aging pipeline system reliability by the reciprocity of all parameters and its sensitivity analysis was studied in detail. The corrosion fatigue life model was established. A fuzzy probabilistic neural network model for reliability assessment of aging long distance oil pipeline was put forward, considering the imprecision of the information provided by in-line inspection, uncertainties associated with pipeline material properties, operational loads, and the rate of corrosion growth. The dynamic failure probability assessment method for corrosion pipeline was given by the reliability analysis technique, combining the assessment method of"fitness for purpose". 3 Research on the Structural Finite Element Analysis for Aging Oil Pipeline's Crossing and Spanning SectionTaking the fact into account that the devastating impact of such natural disaster as slope, subsidence, sedimentation, et al, in unsteady geologic region; based on the elastic foundation beam theory, the mechanical model of pipe-soil subsidence was established. The pipe-soil interaction was simulated as nonlinear spring element; and the stress distribution under such different circumstances as different spanning length, different buried depth, different wall thickness, different external diameter, et al, was calculated by the finite element analysis; by which both the maximum and the minimum Mises stresses and their corresponding positions were gained; therefore, the critical spanning length which would result in pipeline failure was gained, too. Considering the fact that the crossing highway was one of the dangerous belts for buried pipeline, the elbow part of buried pipeline was modeled, and the stress of the syphon's elbow, transition and the highway's buried part was analyzed; the finite element model of pipeline response to seismic load was set up by considering the pipe-soil interaction. And as a result, the safety assessment of onshore aging pipeline seism-resisting capability was well guided.4 Research on Structural Inspection and Maintenance Scheme of Aging Oil Pipeline The reliability analysis model with the effect of inspection and maintenance considered was the basis of aging pipeline time-dependent reliability analysis. Many reliability analysis models with the effect of inspection and maintenance considered were put forward including life model, failure rate model, life reliability model, et al, which help to the analysis of aging pipeline maintenance effect.Describing and contrasting the structural deterioration model and the maintenance model of aging pipeline, considering the uncertainties existing in the structural deteriorating process and the imperfectness, regarding the semi-Markov model, statistical process or the time-dependent reliability index as the failure function, the dynamic deterioration model was then established. A whole framework which helped to optimizing and evaluating the large aging pipeline's maintenance, replacement, inspection and condition assessment was given.Considering the uncertainties of inspection instruments and maintenance rules, a new inspection and maintenance planning for defects was given by adopting the Markov process. At the same time, combining the"fitness for purpose"assessment, the optimum integrity management scheme which plans to repair the aging pipeline was established, through the cost-effect analysis based on the integrality assessment of aging oil pipeline. Therefore, the economical and safe operation of the aging pipeline would be guaranteed.
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