Calculation methods for the gas pipeline failure rate

Abstract

Determination of gas pipeline failure rates is essential for quantitative risk assessment and integrity management of gas pipelines. To this end, the functional relationship between failure rate and failure probability is established by reliability theory, considering that the two terms are often confused in the literature. Then, existing methodologies for the estimation of failure rates are divided into three categories, namely methods based on historical failure data statistics, methods based on expert knowledge and experience, and methods based on structural reliability analysis. Finally, characteristics and applicability of the three methods are compared. We find three essential aspects to consider in determination of the choice of method in practical engineering: (1) operation and management level of gas suppliers, (2) features or merits of detection technologies of pipelines, and (3) integrity of pipeline failure databases. Considering that external interference as a cause of failure belongs to a type of extreme failure load, it would be appropriate to adopt methods based on historical failure statistics to determine failure rates. On the contrary, when historical data are relatively scarce or the pipeline detection technology is advanced, it is advisable to use methods based on structural reliability analysis to obtain the failure rates. In this study, the calculation model and procedures for the method based on historical failure data statistics are established. Furthermore, the so-called bathtub curve of pipeline failure rates is obtained by methods based on structural reliability analysis.