PSI - Issue 57

Arne Fjeldstad et al. / Procedia Structural Integrity 57 (2024) 692–700 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4. Probabilistic fracture mechanics analysis results for a butt weld with calculated fatigue life of 30 years. Excerpt f rom DNV-RP-C210.

To streamline the inspection planning process for FPSOs, generic inspection plans are often employed to limit the analysis scope, considering the potentially vast number of details involved. These plans involve conducting probabilistic fracture mechanics analyses to assess the inspection plan based on the calculated fatigue life, using inputs that are representative of the overall structure. Fig. 5 depicts an example inspection plan derived from post processing these results. The inspection plan for a specific structural detail is determined by correlating the fatigue life on the x-axis with a vertical line drawn from the corresponding value on the a-axis. The time for the 1 st inspection, 2 nd inspection, and so on, is then assessed by identifying the value on the vertical axis where the vertical line intersects the curve representing the inspections. The vertical line in Fig. 5 represents a structural detail with a calculated fatigue life of 10 years. According to the generic inspection plan, inspections are scheduled to be conducted after 7 and 13 years of operation.

Fig. 5. Probabilistic fracture mechanics analysis results for a butt weld with calculated fatigue life of 30 years.

5.2. Implementing in- service inspection plans for FPSO’s

Ship compartments contain a multitude of structural details, necessitating the implementation of efficient inspection strategies. The scope of inspection is extensive, requiring thorough evaluation of numerous details. Striking a balance between comprehensive inspections to ensure structural integrity and the operational challenges