Assessment of Fatigue Failure in FPSO Mooring Systems

Mooring lines failures are a critical subject in FPSO designs, analysis, and operations. This study aims to achieve this by extending damage calculations results from rain flow analysis to the computation of an appropriate range of Weibull parameter h. The Weibull method is a fatigue analysis method that is done in the frequency domain. Selection of a particular h parameter that will accurately compute damage is a difficult challenge. So, damage calculations can overestimate or underestimate the fatigue damage and fatigue life of mooring lines. Analysis was also carried out in the frequency domain using Dirlik's method and the results from the two domains compared. Metocean Data for the Gulf of Guinea was obtained and inputted into Orcaflex for analysis. 12 wave classes, current and wind data were extracted and included in a computer model of the FPSO. Rain flow analysis was carried out and the results for all 12 mooring lines in the 12 different wave classes were extracted for analysis. Results from here showed all stresses were within the acceptable limits specified in DNV OS E301 guidelines. Initial analysis was carried out for all 12 wave classes considering Low Frequency LF forces alone and another carried out considering Wave Frequency WF forces alone for 3 wave classes. The 3 classes selected were in line with DNV Ultimate Limit State ULS conditions. Back calculation was used from the fatigue damage results obtained from the analysis and applied to the Weibull equation so an appropriate h parameter can be gotten. Results obtained can be applied to the fatigue analysis of mooring lines within the Gulf of Guinea environment. Adebanjo Victor Abiola | Ibiba Douglas | Matthew N. O.Sadiku | Uwakwe C. Chukwu | Inegiyemiema Morrisson | Onuh Chukwuka Humphery "Assessment of Fatigue Failure in FPSO Mooring Systems" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-6 | Issue-6 , October 2022, URL: https://www.ijtsrd.com/papers/ijtsrd52155.pdf Paper URL: https://www.ijtsrd.com/engineering/other/52155/assessment-of-fatigue-failure-in-fpso-mooring-systems/adebanjo-victor-abiola