Presentation on theme: "Slide 1. Slide 2 A New Approach to Repair of FPSOs Without Hot Work A. T. Echtermeyer, M. J. Larsen & K. P. Fischer DNV, Høvik, Norway presented by Johan."— Presentation transcript:
Slide 2 A New Approach to Repair of FPSOs 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 JOINT INDUSTRY PROJECT UPDATE
Slide 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)
Slide 4 FPSO In-Service Inspection: Ballast tank surface area 100,000 – 200,000 m2 The inspectability of most FPSOs and tankers is a nightmare. Design for inspectability rarely enters the design engineers mind until he has to participate in the inspection himself. (R. G. Bea)
Slide 5 Local or General CorrosionFracture FPSO In-Service Failures: INADEQUATE PROTECTIONINADEQUATE DESIGN or OVERLOAD
Slide 6 Ideal Repair: NO PRODUCTION STOP NO HOT WORK NO GOING OFF LOCATION ADAPTABLE TO ANY CASE COST EFFECTIVE QUICK LOW TECH RELIABLE ADHESIVE PATCH: IN-SITU ON LOCATION ONLY REPAIR AREA NO CUTTING/WELDING MOST GEOMETRIES VERY! EQUIV. TO WELDING 20 YEARS EXPERIENCE
Slide 7 Repair Timescales Shut down production Transit to yard Docking + repair Transit to field & hook up Months Wait for weather- window Shut down production Repair Start production Weeks Wait for weather- window Clean damaged area Repair & cure No interruption in production Extensive welded repairs Minor welded repairs Patch repairs Production interruptions avoided – only damaged area is shut down
Slide 8 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 What Is Adhesive Patch Repair?
Slide 9 MATRIX What Is an Adhesive Patch? LAMINATE + ADHESIVE REINFORCEMENT
Slide 10 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) What Is an Adhesive Patch?
Slide 11 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 What Is an Adhesive Patch?
Slide 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!
Slide 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
Slide 14 Opportunities with Patch Repair Smart materials for performance monitoring Tailor-made directional properties Lightweight – easy handling
Slide 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
Slide 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
Slide 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
Slide 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
Slide 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
Slide 20 Use of DNVs 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 Safety factors calibrated to ensure consistent safety level Qualified repair Loads Material properties Structural reliability approach
Slide 21 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 Qualification procedure for adhesive patch repairs DNV-OS-C501 Composite Components DNV-RP-A203 Qualification procedures for new technology Specific information and technical background for patch repair design and qualification
Slide 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
Slide 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)
Slide 24 Corroded Panel Demonstrator
Slide 25 Panel Repair: Production Sequence
Slide 26 Fractured Stiffener Demonstrator Artificial crack Composite repair by pre-preg or prefab plates
Slide 27 Corroded panel demonstratorFractured stiffener demonstrator Detail of notch with strain gauge – ready for testing Demonstrator Testing
Slide 28 Continued Work in a Phase : 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
Slide 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.
Slide 30 Acknowledgement DNV would like to thank the following companies in Phase 1 of the JIP Qualification of Adhesive Bonding in Structural Repairs of FPSOs 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.