Probabilistic inspection planning of offshore welds subject to the transition from protected to corrosive environment

In this paper, a novel method is proposed to optimize inspection plans for fatigue accounting for the situations where corrosion-free or protected environments are changed to a corrosive environment, denoted as the Transitional Environmental Protection (TEP) process. Probabilistic fracture mechanics and S-N curve approaches are calibrated to simulate crack propagations and planning of inspections and repairs of offshore welds. The method presented is relatively simple and conservative: The transition between protected and corrosive environments is addressed by shifting the S-N curve parameters during the damage calculations, performing crack size recalibration and modifying the crack growth material parameters. These concepts are incorporated in an algorithm, which is applicable to new designs or existing structures where no data from previous inspections is available. An example illustrates the potential of the algorithm.