The optimal design level for onshore natural gas transmission pipelines was explored through a hypothetical pipeline example in this paper. The work employed the reliability-based cost-benefit analysis framework established in literature and focused on evaluating the life-cycle cost of the pipeline. The pipe wall thickness was selected as the sole design parameter. Based on historical failure statistics, equipment impact and external corrosion were assumed to be the two failure causes for the pipeline. The lifecycle cost included the wall thickness-related initial construction cost as well as the costs of failure and maintenance. The cost of failure included the cost of fatality and injury, costs of damage to the public and private properties, and the value of lost product. Due to a lack of information, indirect failure consequences such as increased regulatory pressure, lost of public confidence, and litigation cost were not considered. The cost of maintenance included the cost of scheduled inline inspection and preventive repair of external corrosion defects. The allowable societal risk was considered as a constraint in the optimal design selection, whereby the average societal risk associated with the gas transmission pipeline network in the United States, as implied by the current design practice, was adopted as the allowable societal risk level. The optimal design for the example pipeline was sought by applying the minimum expected life-cycle cost criterion as well as the first-, second-, and third-degree stochastic dominance rules. The results show that the optimal design based on the minimum expected life-cycle cost criterion utilizes a design factor of 0.74. If the allowable societal risk constraint is applied, the CSA design, which utilizes a design factor of 0.72, becomes the optimal design. It was observed that the expected life-cycle cost is insensitive to wall thickness variation in the vicinity of the optimal design. The expected life-cycle cost of the CSA design is practically the same as that corresponding to a design factor of 0.74. The results also show that the expected cost of maintenance accounts for a significant portion of the expected life-cycle cost. Therefore, the optimal design achieved in this analysis can be potentially improved by considering the maintenance parameters as design parameters in addition to the wall thickness. Based on the second- and third-degree stochastic dominance rules, any designs involving design factors of 0.76 or greater are suboptimal for a risk-averse decision maker. Applying the allowable societal risk constraint will further relegate the design involving a design factor of 0.74 to the suboptimal design set. Both the CSA and ASME designs belong to the optimal design set and satisfy the allowable societal risk constraint. Note that the ASME design has the highest expected life-cycle cost of all candidate designs. The wall thickness of the design with the minimum expected life-cycle cost is the lower bound of those included in the optimal set. The results demonstrate the implication of the variability of the life-cycle cost for selecting the optimal design from a risk-averse perspective.


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    Titel :

    Optimal design of onshore natural gas pipelines


    Beteiligte:
    Zhou, Wenxing (Autor:in) / Nessim, Maher A. (Autor:in)


    Erscheinungsdatum :

    2011


    Format / Umfang :

    11 Seiten, 5 Bilder, 8 Tabellen, 18 Quellen




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch




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