Gas Pipeline Design Methodology Based On Risk Assessment

Pipelines risk assessment technology is a new pattern of pipelines safety assessment technology that originated abroad in nineteen seventies and has strong practical pertinence. In general, the scheme of saving man-hour and fare is mainly chosen when the newly-built gas pipeline is designed. However, the risk of gas pipeline is not taken into account in this condition. The various influence factors should be taken into account during design of gas pipelines, but influences of the many various factors are difficult to evaluate reasonably when the various schemes are compared and selected by traditional design methods. Therefore, in this paper the main problem to solve is how to find out risk factors that have an important effect on safety and reliability of newly-built gas pipelines when gas pipelines are designed and built, thus the quality of gas pipelines is taken measures to inspect and control effectively during design and building of gas pipelines. In addition, a new method in point of risk assessment that can evaluate various design schemes of gas pipelines has been set up.In this paper, it sets forth in brief the development background, investigation practice and application effect of risk assessment of gas pipelines. It also puts forward the basic theory, evaluation flow and evaluation methods of risk assessment of gas pipelines. In addition, based on the basic ideology and evaluation methods of risk assessment of gas pipelines abroad, in condition of design, building and operation management of new-built gas pipelines, complying with technical standard and safety criterion of national gas pipelines, accident probabilities that happen in area of newly-built gas pipelines have been analyzed and expense sequel that is caused by gas pipelines if accident happens have been evaluated, thus fault tree analysis adapts to qualitative risk assessment of newly-built gas pipelines and risk factors can be distinguished. The risk assessment factor system of newly-built gas pipelines that is more complete and can adapt to the national practice of gas pipelines has been established.In addition, because not all failure factors can be quantitative, in this paper, the multilevel fuzzy comprehensive evaluation has been established to evaluate gas pipelines. The uncertainty Analytic Hierarchy Process has been used to make certain various factors weights and improves on fuzzy comprehensive evaluation in order to adapt to practical conditions. Based on the rank weights and the rank assessment matrix of various factor given, according to proper fuzzy arithmetic, the fuzzy assessment aggregate of gas pipeline risk can be calculated. Every leakage effective coefficient index given by the traditional index method is blurred to reckon the relative risk value of each section, thus the risk rank of each section is determined and fuzzy comprehensive evaluation of gas pipeline risk has been achieved.Finally, acceptable risk criterion and risk control measures have been discussed in this paper. On the basis of the discussion, in order to adjust correlative design parameters and building parameters according to various risk degree of gas pipeline segments under distinct circumstances during design and building, the utility function and constrained cost optimization principle have been adopted to make balance among cost, safety and environment protection in point of risk decision-making in this paper. Thus, priority rank of risk controlling of gas pipeline segments comes true. Besides, the method of controlling risk and the catabalic measures of prevention factors are given to make different segments risk level considerable and acceptable. On the basis of above studies, software that can evaluate design taking into account risk assessment of gas pipeline and has been developed and introduced.