PSI - Issue 5

Fikri Bashar Yalchiner/ Structural Integrity Procedia 00 (2017) 000 – 000

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Zuheir Barsoum et al. / Procedia Structural Integrity 5 (2017) 377–384 5.2.Spectral Fatigue Analysis Results DNV RP C 203 [18], is used for in line joints and API RP 2A – WSD [19] is used for the other joints for SCF calculation. 383

SACS JOINT NO: 399 FATIGUE LIFE 44.72 YRS AGAINST 100

SACS JOINT NO: 308 FATIGUE LIFE 47.33 YRS AGAINST 100

SACS JOINT NO: 205 FATIGUE LIFE 194.61 YRS AGAINST 200

SACS JOINT NO: 299 FATIGUE LIFE 78.51 YRS AGAINST 200

SACS JOINT NO: 203 FATIGUE LIFE 57.17 YRS AGAINST 200

SACS JOINT NO: 204 FATIGUE LIFE 68.48 YRS AGAINST 200

SACS JOINT NO: 201 FATIGUE LIFE 70.49 YRS AGAINST 200

SACS JOINT NO: 219 FATIGUE LIFE 101.36 YRS AGAINST 200

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Fig. 4. Fatigue Life Estimation Values for the critical joints.

Based on the Spectral fatigue analysis, following conclusions are drawn:

• Failure Critical Nodal Joint at Mudline: Leg joints of the jacket structure at mudline elevation have a fatigue life less than intended design life of jacket with FOS 10.0. Hence Joint No 201,219,299, 203,204,205 are to be inspected. • Critical Nodal Joint above Mudline: All Joints of the jacket structure above mudline other than critical Nodal joint at Mudline have a fatigue life in excess of intended design life of jacket with FOS 5.0, except 2 joints 308 & 399. Hence joint no.308 & 399 are to be inspected. • Inline Joints: All Inline Joints of the jacket structure have a fatigue life in excess of intended design life of jacket with FOS 5.0. Abovementioned joints which have lesser fatigue life than intended design life are potential candidates for HFMI application in this life extension study for fixed offshore platform.

6. Conclusions

Applying HFMI for aged fixed offshore structures not only reduces maintenance costs, increases safety of the structure and extends the intended life in an economic way as compared to other methods. That HFMI treatment is faster to apply as compared to burr grinding, causes work time on the offshore platform to dramatically reduce. The method also can be applied in difficult access areas such as underwater or rope access. Another advantage of HFMI method is that the fatigue life improvement obtained is valid for spectrum loadings as well, since the offshore platforms are mainly subjected to spectrum loading.