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