2. JOINT INDUSTRY PROJECT UPDATE
“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 Gärdin Mobile Offshore Units / FPSO, DNV SEA & ANZ, Singapore Telephone

3. 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)

4. Ballast tank surface area 100,000 – 200,000 m2
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)

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

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

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

8. 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 + =

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

10. 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)

11. 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

12. 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!

13. 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

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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. Use of existing DNV documents
DNV-RP-A203 Qualification procedures for new technology
DNV-OS-C501 Composite Components
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
Qualification procedure for adhesive patch repairs
Specific information and technical background for patch repair design and qualification

22. 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

23. 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)

24. Corroded Panel Demonstrator

25. Panel Repair: Production Sequence

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

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

28. Continued Work in a Phase 2:
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

29. 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.

30. Acknowledgement ConocoPhillips Norsk Hydro Petrobras (CENPES)
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 thank Devonport Royal Dockyard Ltd (DML) for their cooperation in the JIP and also for their contribution to this paper.

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