Quantitative analysis on failure tree of subsea pipeline pigging risk

The pigging test is an important means for daily operation and maintenance of subsea pipelines. However, most of the current subsea pipeline pigging tests in China involve high execution risks, the most common one being the jamming of pigging balls. In order to reasonably guard against pigging risks, it is necessary to carry out pre-pigging risk analysis. The quantitative analysis of failure tree is applied for risk assessment in this paper. Through risk identification, various intermediate or basic events causing pig sticking were presented, and the failure tree of subsea pipeline pigging was mapped. Furthermore, the minimum cutset and the structural importance of basic events were worked out. On this basis, the resolution processes of mathematical model of fuzzy comprehensive evaluation on pigging risk and level-2 evaluation were given. Through calculation of examples, the level of pigging failure probability was worked out, helping to address the difficulties in quantitative risk assessment of subsea pipeline pigging. The research results can serve as a reference for quantitative analysis on other kinds of operation risks of subsea pipeline.