Probabilistic Risk Analysis of TLP Tether Fracture

by T. Moan, Norwegian Inst of Technology, Norway,
M. J. Marley, Norwegian Inst of Technology, Norway,
G. Jiao, Norwegian Inst of Technology, Norway,

Document Type: Proceeding Paper

Part of: Structural Safety and Reliability


A stochastic model for fatigue crack growth and final fracture of TLP tethers is formulated. Model updating through in-service inspection is included. The integrity of the cracked tether is evaluated by the R6 assessment procedure. Considered strategies for ensuring tether reliability include regular inspections and leak-before-break criteria. For the example, it is found that the sensitivity of an ultrasonic inspection method may be able to increase the reliability significantly if multiple inspections are performed. For a leak-before-break strategy, it is shown that the probability of final fracture during the repair period is greatly increased by model updating conditioned on the event of a leak.

Subject Headings: Risk management | Probability | Cracking | Stochastic processes | Offshore platforms | Ultrasonic methods | Inspection | Leakage

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