Deep water developments are being pursued vigorously in various parts of the world (West Coast of Africa, Gulf of Mexico, etc.). The riser system is a critical part of the field architecture. Riser failure results in reduction or cessation of revenue. It may also lead to spillage or pollution and may endanger lives. Hence, riser design must carry a high degree of reliability. Steel catenary risers (SCRs) are considered to be technically feasible and commercially efficient solutions, especially when high temperatures and pressures are involved. However, in terms of fatigue, SCRs are very sensitive to environmental loading. The procedure for fatigue analysis is essentially deterministic. This paper concentrates on the probability of failure associated with the current design practice of fatigue analysis of SCRs. The procedure is illustrated with sample calculations with first-order vessel motion and a flow chart for assessing the probability of fatigue failure is also given. The example is chosen so as to highlight the issues involved. The probability of failure is used to determine the "safety index." The probability calculations have been reformulated so that they are applicable for the design of SCRs. The probability of fatigue failure, for the example chosen, is also reported. The overall aim is to increase the confidence in the design of such systems in deep water environment.
展开▼
