Bai, X.; Zan, Y.F.; Luo, X.F.; Huang, K., and Guo, R.N., 2020. Position loss risk analysis of dynamic positioning systems of semi-submersible drilling units by considering time-varying failure. In: Guido Aldana, P.A. and Kantamaneni, K. (eds.), Advances in Water Resources, Coastal Management, and Marine Science Technology. Journal of Coastal Research, Special Issue No. 104, pp. 160–165. Coconut Creek (Florida), ISSN 0749-0208.

Position loss risk analysis of dynamic positioning (DP) systems is essential for the operation of semi-submersible drilling units. Traditional risk analysis methods ignore the probability of equipment failure with time-varying, which may result in inaccurate analysis. In this study, fault tree analysis was combined with the continuous-time Bayesian method based on the D-vine copula model to analyze loss of position (LOP). The D-vine model decomposition method was used to calculate multiple two-dimensional copula correlation measures for determining the system reliability with time and for calculating the effect on the occurrence of LOP. The key aspects of LOP were analyzed from the perspective of the variability of equipment at the time of failure. The results can provide a crucial reference for the maintenance of the DP system.