The limit states design appendix currently being developed for inclusion in the Canadian Standards Association pipeline design code, Z662, Oil and Gas Pipeline Systems contains preliminary partial safety factors that were selected on the basis that they result in designs similar to those produced using the existing working stress design standards.
This paper suggests an approach for selecting partial factors for limit states design of pipelines based on formal reliability analysis. Such an approach recognizes that consistent safety levels can be achieved for different pipeline sections by varying the target reliability as a function of the severity of failure consequences, where consequences are measured in terms of public safety, economic costs, and damage to the environment. Where the consequences of failure are more severe, higher reliability is required. Where the consequences are less severe, lower reliability can be tolerated, with the same risk level being achieved.
This paper reviews the limit states design method and discusses the selection of target reliability levels and the reliability analysis procedures used to calibrate partial design factors.