ABS Floating Production Installations Guide Rule Change: FPSO Fatigue and Strength Assessment

Transcription

1 OMAE Specialty Symposium on FPSO Integrity ABS Floating Production Installations Guide Rule Change: FPSO Fatigue and Strength Assessment Ernesto Valenzuela Haihong Sun Jer-Fang Wu Tuanjie Liu Offshore Technology Department American Bureau of Shipping September 1, 2004

2 Overview ABS SafeHull FPSO Concept Enhancement for SafeHull FPSO Enhancement for FPI Guide ABS Guide for Buckling and Ultimate Strength Assessment for Offshore Structures New Development for FPSO Guide 2

3 ABS SafeHull for FPSO Provides evaluation for strength & fatigue assessment for FPSO s by Considering actual trading history and site specific wave environments Applying ESF (Environmental Severity Factors) to modify unrestricted service loads through "Sea Environment Assessment System" (SEAS) Module Incorporating loads/reactions from topsides Determining plate renewal scantlings based on site specific environment and owner specified corrosion rate 3

4 Definition of ESF s Environmental Severity Factor (ESF) is a severity measure of historical or intended environment relative to the unrestricted service environment in terms of fatigue life and extreme loads. It is denoted by α and β in SafeHull-FPSO system, respectively. 4

5 SafeHull FPSO Modules Phase A SEAS 3 Hold Model SafeHull/FPSO V2 G1 Y Z X Output Set: E LE MENT P ROPE R TIES Crit e ria : T HI CKN ES S OR AR EA Phase B 5

6 SafeHull System Flowchart The SafeHull System Consist of Rules & Software Programs Rules G u id e fo r B u ild in g and Classing Steel Vessels Tankers Bulk Carriers Container Ships FPSOs SafeHull Phase A SafeHull Phase B Floating Production Installation (FPI) Supplem ent Supplem ent Spectral-Based Fatigue Analysis for Floating Production, Storage and Offloading (FPSO) System s SEAS Version Version S a fe H u ll F E A G u id a n c e for Hull Structures G lo b a l 3 D A n a lys is (Draft ) 6

7 SafeHull FPSO System SafeHull Dynamic Loading Approach SEAS Site & Route Specific Wave Conditions Unrestricted Wave Conditions SH Loads β-factors α-factors SafeHull FPSO System Strength/Fatigue Criteria Site & Route Specific Hull Strength Design & Assessment 7

8 13 Dynamic Load Parameters 1. VBM 2. HBM 3. EPP 4. EPS 5. VAC Hull Girder Loads 11. WHT Local Loads 6. TAC 10. VRM 13. HSF 12. VSF 9. RMO 8. PMO 7. LAC 8

9 New Supporting Document: Commentary on The Criteria to Adapt the SafeHull System to FPSO Applicatoins (May 2004) The concept of applying SafeHull for new build and conversion FPSO applications The procedure to use SafeHull for FPSO analysis Background of Sea Environment Assessment System (SEAS) 9

10 SafeHull System Adapted to FPSO Applications Site-specific wave environment considerations ABS global wave database is capable of considering actual trading tanker history for conversions Site-specific and route-specific fatigue analysis for FPSOs Concept of Environmental Severity Factors (ESF) to modify unrestricted service loads Vessel RAO database in SEAS and comparisons 10

11 SafeHull System Adapted to FPSO Applications (Contd) Spectral Fatigue approach for FPSO and calibrations Methodology for remaining fatigue life assessment for conversion FPSO with examples Simplified fatigue method in SafeHull system Bimodal spectrum application for site-specific fatigue analysis with examples SafeHull/FPSO application examples 11

12 What is New in SafeHull FPSO V10 Remove 0.5 cap for all ESF Beta's Rule table revision made for sloshing load cases Canned-Route database added to SEAS system Bimodal wave data application New PI for expediting plan review process 12

13 What is New in SafeHull FPSO V10 Wave Heading Effect Previous approach: Different heading used for base and design α = D D spectral U spectral Site ( equal probabilit y) ( required heading ) Improved approach: same heading used for base and design cases α = D D spectral U spectral Site ( required ( required heading heading ) ) 13

14 What is New in SafeHull FPSO V10 25 Canned Routes in SEAS 14

15 What is New in SafeHull FPSO V10 25 Canned Routes in SEAS (Contd) 1. Dover Strait to New York 2. Los Angles to Yokohama 3. Valdez to Los Angles 4. Yokohama to Persian Gulf 5. Gulf of Mexico to Persian Gulf 6. Dover Strait to Persian Gulf 7. Dover Strait to Gulf of Mexico 8. Europe to Persian Gulf 9. Med Sea to Persian Gulf 10. Persian Gulf to Med Sea 11. Europe to Med Sea 12. Gulf of Mexico to Persian Gulf 13. Persian Gulf to Gulf of Mexico 14. Persian Gulf to Red Sea 15. Red Sea to Persian Gulf 16. Persian Gulf service 17. Red Sea service 18. Med Sea service 19. Gulf of Mexico to Med Sea 20. Med Sea to Gulf of Mexico 21. Africa to North America 22. Persian Gulf to Singapore 23. Singapore to Persian Gulf 24. Persian Gulf to Korea 25. Korea to Persian Gulf 15

16 What is New in SafeHull FPSO V10 Bimodal sea splitting approach Bimodal wave environment with Waves and Swells combined Wave splitting at Tp =7.5 s Waves (Bretschneider spectrum, short crested wave, rain-flow correction) Tp (sec) Total Hs (m) Tp(sec) Total Hs (m) Swells (JONSWAP spectrum, long crested wave, rain-flow correction) Total Total

17 What is New in SafeHull FPSO V10 ESF α for bimodal sea splitting α 1 bimodal = factor 1 ( α waves 1 + α swells ) factor is an owner supplied adjustment factor 17

18 What is New in 2004 FPI Guide for FPSO Optional Notation: FL(Year) for New Constructions Mandatory Notation: RFL(Year), Year in (site of Installation) for Conversion of Existing Vessel to FPSO, FPS or FSO Survey Requirements for Tanker Conversion to FPSO: Conversion Survey Requirements Structural Repairs/Steel Renewal Bottom Plate Pitting Repair SH FPSO V10 Release 18

19 What is New in 2004 FPI Guide for FPSO Adjust tank test cases (at yard and on site for 1-year return period) Specify wave condition (10-year return period) for transit conditions Specify new headings for ESF calculations 19

20 ABS Guide for Buckling and Ultimate Strength Assessment for Offshore Structures (April 2004) CONTENTS Tubular Members Plates and Stiffened Panels Corrugated Panels Circular Stiffened Cylindrical Shells Tubular Joints Finite Element Analysis 20

21 ABS Guide for Buckling and Ultimate Strength Assessment for Offshore Structures (April 2004) FEATURES Covering Most Commonly-used Components and Nonlinear FEM Guidelines Incorporating ABS Experiences Being Most Straightforward for the Users Calibrating with Large Amount of Test Database and Nonlinear FEM Analysis 21

22 ABS Guide for Buckling and Ultimate Strength Assessment for Offshore Structures (April 2004) COMPARISON WITH SHIP RULES Direct Calculation vs. Rule-based Calculation for Loads and Load Effects 100-years Return Period vs. 20-years Service Life for Design Environmental Condition Gross Scantling vs. Net Scantling Allowable Utilization Factors vs. Material Reduction Factors 22

23 New FPSO Guide Guide for Building and Classing FPSO Systems 23

24 New FPSO s Procedure Highlights Adopts gross scantling concept which is the common offshore industry practice Uses actual loading conditions/patterns that are prescribed in the Loading Manual Employs seakeeping analysis including the effect of mooring, riser, thruster, and topside effects Retains two parts of the SafeHull methodology, which are Standard Class Notation of A1 FPSO or A1 FOI, and optional Class Notation SFP or SFI 24

25 FPSO Class Notations According to New Guide Mandatory A1-FPSO or A1-FOI, RFL (Expected Remaining Fatigue Life in years), Matured Year in Site of Installation. For example RFL(15), 2019 in Gulf of Mexico Requires hull girder and main supporting members strength and fatigue review DPS for a Dynamic Positioning System AMS automatic monitoring systems for a Disconnectable System Optional SFP or SFI requires strength and fatigue review using FEA verification SFA (year) based on ABS Guide on Spectral-Based Fatigue analysis for FPSO Systems SH-DLA based on ABS Guidance Notes on SafeHull-Dynamic Loading Approach for Floating Production, Storage and Offloading Systems 25

26 New FPSO (Phase I) Analysis Procedure FPSO Load Conditions Seakeeping Analysis Model Vessel DLP RAO s Nominal Stress RAO s Obtained by Combining DLP RAO s 100-yr Storm at Site 10-yr Storm on Route Full Spectral Analysis to Obtain Extreme Value New FPSO Guide Acceptance Criteria 26

27 New FPSO (Phase II) Analysis Procedure Loadings Screened from Phase I Full Scale FE Model Based on Gross Scantling Stress Spectrum Full Spectral Analysis to Obtain Extreme Value Spectral Fatigue Analysis Strength Check Buckling Check Fatigue Check 27

28 Summary of ABS Experience on Developing FPSO Standards From Well-Proven Tanker Experience Environmental Severity Factors Approach Offshore Approach 28

29 Thank You! Free Download of ABS Standards 29