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“A New Approach to Repair of FPSO’s Without Hot Work” A. T. Echtermeyer, M. J. Larsen & K. P. Fischer DNV, Høvik, Norway presented by Johan G ä rdin Mobile Offshore Units / FPSO, DNV SEA & ANZ, Singapore Telephone +65 67791266 johan.gardin@dnv.com. JOINT INDUSTRY PROJECT UPDATE. www.dnv.com.

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  1. “A New Approach to Repair of FPSO’s Without Hot Work”A. T. Echtermeyer, M. J. Larsen & K. P. Fischer DNV, Høvik, Norwaypresented byJohan GärdinMobile Offshore Units / FPSO, DNV SEA & ANZ, SingaporeTelephone +65 67791266johan.gardin@dnv.com JOINT INDUSTRY PROJECT UPDATE www.dnv.com

  2. Typical FPSO In-Service experience: Structural and materials protection issues: • Integrity of Hull (3 of 4 suffer cracking in tank boundaries) • Integrity of Ballast and cargo piping (construction standards for cargo and ballast piping appear inadequate. Weld failures, corrosion & subsequent leaks) • General corrosion and coating issues (need for good inspection programme) (Source OLF, Norway: data for 4 FPSO)

  3. FPSO In-Service Inspection: Ballast tank surface area 100,000 – 200,000 m2 The inspectability of most FPSO’s and tankers is a nightmare. Design for inspectability rarely enters the design engineer’s mind until he has to participate in the inspection himself. ” (R. G. Bea)

  4. FPSO In-Service Failures: INADEQUATE PROTECTION INADEQUATE DESIGN or OVERLOAD Local or General Corrosion Fracture

  5. Ideal Repair: ADHESIVE PATCH: • IN-SITU ON LOCATION • ONLY REPAIR AREA • NO CUTTING/WELDING • MOST GEOMETRIES • VERY! • VERY! • EQUIV. TO WELDING • 20 YEARS EXPERIENCE NO GOING OFF LOCATION NO PRODUCTION STOP NO HOT WORK ADAPTABLE TO ANY CASE COST EFFECTIVE QUICK LOW TECH RELIABLE

  6. Shut down production Transit to yard Shut down production Docking + repair Repair & cure Repair Start production Transit to field & hook up Repair Timescales Extensive welded repairs Minor welded repairs Patch repairs Wait for weather-window Wait for weather-window Production interruptions avoided – only damaged area is shut down Clean damaged area No interruption in production Months Weeks

  7. What Is Adhesive Patch Repair? Principle: • A damage (e.g. hole, crack, corrosion) is discovered and needs repair • A patch is fabricated from a structural laminate • The patch is adhesively bonded to the substrate to repair the damage + =

  8. What Is an Adhesive Patch? • MATRIX LAMINATE + • REINFORCEMENT • ADHESIVE

  9. What Is an Adhesive Patch? • ALTERNATIVE PRODUCTION METHODS: • WET LAY-UP (Dry Reinforcement and Resin applied directly to substrate by roller and cured in situ) • PRE-PREG (Impregnated patch and adhesive applied to substrate and cured together under heating) • INFUSION (Dry Reinforcement and low viscosity Resin applied directly to substrate and cured in situ under vacuum bag)

  10. What Is an Adhesive Patch? Typical patch materials depend on application: • MATRIX POLYMERS: • Epoxy, Polyester, Vinylester, Urethane... • REINFORCEMENT: • Glass fibre, Carbon fibre, other high performance fibre types. • Multi orientation (csm), Woven roving (0°/90°), Uni-directional, or Combination mats • ADHESIVES: • Structural adhesive: May be identical to the matrix or a dedicated structural adhesive

  11. Design, Production, Installation • Optimum PATCH DESIGN depends on damage type, location, strength requirements, working conditions during application, available time for repair... • Choice of production and installation METHOD must suit material choice and design of patch repair • Skilled WORKMANSHIP, good PROCEDURES and QUALITY ASSURANCE during design and production / installation is paramount!

  12. Limitations to Patch Repair • Some polymers may be SHE HAZARDS • Substrate CLEANLINESS is critical • STIFFNESS may be difficult to achieve • SHEAR AREA between patch and substrate must be adequate • PEELING STRESS must be avoided

  13. Opportunities with Patch Repair • ‘Smart materials’ for performance monitoring • Tailor-made directional properties • Lightweight – easy handling

  14. Current Applications of Patch Repairs Currently used for rehabilitation within: • Infrastructure / civil engineering • Navy vessels • Process plant piping • Offshore piping and non-structural applications Extension to FPSOs could be: • Structural applications, such as: • Reinforcing corroded panels (compensating for loss of thickness) • Bridging of cracks in stiffeners or brackets (relieving hot spot stress) • Strengthening of decks, frames bulkheads etc. to carry additional equipment • Non-structural applications, such as: • Bridging of cracks or holes in platforms etc

  15. Application Examples, DML Deck repairs on naval ships Repair carried out during scheduled maintenance docking: Avoids time-consuming removal / protection of mechanical / electrical outfitting prior to welding All photos courtesy of DML Composites

  16. Application Examples, DML Rehabilitation of pipelines Repair can be permanent or temporary Repair can often be carried out without shutdown of production: Avoids expensive down-time All photos courtesy of DML Composites

  17. Application Examples, DML Repair of flare tower: Repair carried out offshore Repair completed without hot work, avoiding fire hazard All photos courtesy of DML Composites

  18. Qualification of Patch Repairs for FPSO DNV is currently developing a qualification guideline for adhesive patch repairs of FPSO Key objectives include: • Provide a LINK between existing DNV documents for design of offshore ships and design of composite components • Provide SPECIFIC GUIDANCE on design and qualification requirements for patch repairs on FPSO • Develop and test demonstration examples to establish QUALIFICATION TEST requirements

  19. Use of DNV’s Reliability Experience • The basic functional requirements for a patch are simple: • The required strength and stiffness must be restored • The repair must resist the local environment • The growth of the damage must be stopped • Additional strengthening may be required if the damage is due to a design flaw • Acceptance criteria for patch repairs are developed based on: • DNV experience with FPSO and ships in general • Recently developed acceptance criteria for composite materials Loads Material properties Safety factors calibrated to ensure consistent safety level Structural reliability approach Qualified repair

  20. DNV-RP-A203 Qualification procedures for new technology Qualification procedure for adhesive patch repairs DNV-OS-C501 Composite Components Specific information and technical background for patch repair design and qualification Use of existing DNV documents DNV-OS-C101 Design of offshore steel structures, general DNV-OS-C102 Structural design of offshore ships DNV-RP-C203 Fatigue strength of offshore steel structures DNV Rules for ships provide background

  21. Demonstration Examples Key objectives: • Demonstrate principles in patch design and in qualification process • Provide information on failure modes and general performance of generic patch repair designs • Establish base cases to be used as reference when designing full scale patch repairs

  22. Demonstration Examples Two demonstrators are chosen: “The corroded panel” – simulating corrosion damage and leakage in tank or shell plating “The fractured stiffener” simulating a fatigue crack in a beam (local or global stiffening member)

  23. Corroded Panel Demonstrator

  24. Panel Repair: Production Sequence

  25. Fractured Stiffener Demonstrator Composite repair by ”pre-preg” or prefab plates Artificial crack

  26. Demonstrator Testing Corroded panel demonstrator Fractured stiffener demonstrator Detail of notch with strain gauge – ready for testing

  27. Continued Work in a Phase 2 2004-2006: • Extension of test programme (small scale testing – bond zone properties) • Updating the document with more test results • Establishing more repair base cases • Performing a full scale field repair on an FPSO in operation

  28. Conclusions • Fire Adhesive patch repairs enable field repairs of FPSOs and other offshore structures without hot work. • Hazards and shut-down requirements are minimised. • A framework for quality assurance and procedures for qualification of patch repairs will help avoid basic design and production errors, which could potentially lead to repair failures. • This JIP will result in an official DNV document providing such a framework. • Successful full scale field demonstrations will pave the way for patch repairs as an accepted technology in the future.

  29. Acknowledgement DNV would like to thank the following companies in Phase 1 of the JIP “Qualification of Adhesive Bonding in Structural Repairs of FPSO’s” for the permission to present this paper: ConocoPhillips Norsk Hydro Petrobras (CENPES) Petronas (PRSS) Shell-Enterprise Oil Statoil DNV would also like to thankDevonport Royal Dockyard Ltd (DML)for their cooperation in the JIP and also for their contribution to this paper.

  30. PHASE 3(?): MEGA-SCALE TESTING

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