Effect of Limit State Design on the Damage Tolerance of Subsea Systems

Risers, flowlines and other subsea components may be designed using limit state concepts, where displacement controlled loads are allowed to push stresses beyond yield. However, there can be consequences if the lines are damaged or degraded in service.

This paper presents a case study comparing the damage tolerance capacity of a deepwater steel catenary riser (SCR) designed with allowable (working) stress criteria and another designed with limit load criteria. The exercise is also conducted for a production flowline. The damage scenario examines the effects of various levels of pitting corrosion and accounts for the potential of accelerated crack growth due to corrosive effects.