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.

Slide 1

Slide 2

“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 GärdinMobile Offshore Units / FPSO, DNV SEA & ANZ, Singapore

Telephone +65 [email protected]

www.dnv.com

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 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)

Slide 5 Local or General Corrosion Fracture

FPSO In-Service Failures:

INADEQUATE PROTECTION INADEQUATE 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!

•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 RepairsCurrently 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 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

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 ComponentsDNV-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 demonstrator Fractured stiffener demonstrator

Detail of notch with strain gauge – ready for testing

Demonstrator Testing

Slide 28

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

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 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.

Slide 31

PHASE 3(?):

MEGA-SCALE TESTING