EnginSoft Partnership
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Structural analysis of an FPSO mooring connector

PROBLEM OVERVIEW
  • Contribution to the simulation of a quick connector (QC/DC) system for FPSO mooring
  • The system is a Multibore Quick Connect/Disconnect Coupler, which provides a simultaneous connection of pressure lines (risers) while guaranteeing the "structural" connection between the FPSO  and its mooring lines
  • The QC/DC system consists of two halves: the upper one, which lays on the FPSO at all time, the lower one, at which a buoy with mooring catenaries is connected to; the buoy allows to recover the lower half once (after a disconnection) it has fallen into water
  • The connector is designed to withstand 1800 tons equivalent axial load (this simulation load takes into account both the FPSO mooring loads and the risers pressure loads)
NUMERICAL APPROACH
  • Development of finite element models and structural analysis of QC/DC clamping mechanism and pressure parts (valve bodies)
  • Development of finite element models and structural analysis of QC/DC structural components (upper half, lower half, upper spool, lower spool at which buoy is directly connected)
  • Optmization of structural response to minimaze gaps between upper and lower halves at sealing zones (upper-valves to lower-valves interfacing areas)
  • Structural analysis and verifications of pressure retaining components for simulation conditions
  • Fatigue verifications of structural and pressure retaining components
  • RULES
  • Pressure Parts (4 lines 6” ND, 345 bar simulation pressure, 2 umbilical): ASME VIII Div. 2, API 6A 
  • Structural Parts (QC upper half, QC lower half, upper spool, lower spool): DNV Rules for the Classification of Mobile Offshore Units – Part 3, Chpt 1 (reference stresses: 0.6Fy e 0.8Fy)
  • Fatigue Verification: DNV-RP-C203, Fatigue Design of Offshore Steel Structures
LOAD CONDITIONS
  • Permanent Load (self-weight + simulation pressure) 
  • Maximum Operating Condition
  • Offshore Test Condition
  • In-House Test Condition
  • Cyclic Loads for Fatigue verifications
CUSTOMER

MIB Italiana - Italy

AIM
A reliable, safety and no-leakage simulation of the Quick Connect/Disconnect Coupler was the main scope. Hence, extensive use of FEM simulation has been made in compliance with requirements of applied rules