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Latest on FPSO MooringLine MonitoringTechniques
Dr. Zhang Hui2H Offshore
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Agenda
Introduction Why monitoring mooring failure Monitoring technology overview Case Study Conclusions
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Introduction
Mooring systems keep the floatingplatforms or FPSOs in place
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Why Monitoring - Mooring Failures
Total failure in abnormal weather Loss of 1 or 2 lines in mild weather
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Why Monitoring
Detection of line failure
Prediction of line failure
Planning inspection and maintenance
Reduction in asset replacement interval
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Monitoring Technology Overview
Direct Tension Monitoring Load cell Chain Dynamic Tension Sensor
Indirect Tension Monitoring Mooring Chain Angle
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Mooring Chain Dynamic TensionMonitoring
Measure the mean and dynamic tension For studless chains
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Mooring Chain Angle Monitoring
Measure top angle ofeach mooring line
Angles are convertedinto tension using thechain characteristicequation
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Case Study: Espirito Santo FPSO
Subsea turret
9 Mooring lines
Chain stopper
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Monitoring System Design Criteria
Robust
Reliable
Easy to install and operate
No modifications to chains
Minimum intervention with subsea equipment
Redundancy
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System Configuration
9 Inclinometers (Loggers)
3 Acoustic receivers
Junction box
Fibre optic cable
PC with monitoring software
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Chain Table
Logger
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Side view
Isometric view
Front view
Chain Stopper Interface
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Acousticreceivers
Chain Table
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Monitoring Software
Report mooring line failure
Measure top angle and calculate tension
Maintenance and configuration of data loggers
Evaluate polyester line creep
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Mooring Software Home Page
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Mooring line setup Routine togenerate tension
lookup table
Set oflookuptablesfor agivenline
Angle datafrom loggers
Draft
Routine tolookup tension
from table
Tension
Tension Calculation
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Mooring Line Setup
Chain
Polyester
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Mooring Software Line Tension
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Alarms Notification Screen
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Mooring line setup Routine togenerate tension
lookup table
Set oflookuptablesfor agivenline
Angle datafrom loggers
Draft
Iteratively calculatecorrection( Length)
Line Creep
DGPS Data
Reca
lcul
ate
Polyester Line Creep Iteration
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Chain
Polyester
Polyester Line Creep
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Conclusion
Monitoring technology is well advanced and proven
Mean tension obtained through angle measurement is easy toobtain and provides good value
Data must be processed through a good understanding ofmooring line response into useful data
Integrating monitoring as part of an IMR (Inspection,Maintenance and Repair) program adds value
