CHALLENGES OF USING

COMPOSITES OFFSHORE

Andreas T. Echtermeyer

Department of Engineering Design and Materials, Norwegian University of Science and Technology (NTNU),

Trondheim, Norway

Composites Offshore

Corroded Structures

A. Echtermeyer!

Piping ! !ISO 14692!Low pressure, water!

Why should we use composites?

Light : High specific strength & high specific modulus

Easy to form complicated shapes

Good long term properties –  Very good fatigue resistance –  No corrosion (in certain environments)

No maintenance

Material is expensive (prices are falling), but system cost are lower

Why is not everybody using them?

Typically stated:

Composites are being used more and more

It has taken a long time BMW Composite Car

Boeing Dreamliner 50% (Vol) Composite

Perceived Disadvantages of Composites

•  Limited Fire Resistance •  Higher Component Cost (maybe) •  Difficult to inspect (need new approaches) •  Lack of supplies? •  Difficult to qualify? •  Less experience / psychological barrier

•  Let´s see if this is true...

MATERIAL A5 - after 6 minutes

MATERIAL A4 - after 19-20 minutes

(no flashover)

Fire Performance

ROOM CORNER FIRE TESTS for PANELS

Fire resistance is still a big challenge topside, its no problem subsea.

Higher component cost

Typically material costs of composites are more expensive than steel, especially for carbon fibers.

Composite prices have been falling.

They are easier to form. Large pressure vessels are cheaper.

Important cost is the Metal Composite Interface MCI – need more clever solutions - less critical for long spoolable tubes with just 2 endfittings

M. Salama, A.T. Echtermeyer, O. Lindefjeld, Composite Risers for Deepwater Applications, Deepwater Offshore Technology (DOT), Stavanger, 1999

Lower system cost

Less weight gives many advantages –  No buoyancy –  Smaller cranes –  Smaller platform –  Easier to handle

The advantages are only achieved if the entire system is designed for the composite solution.

If composites just replace steel parts, they are often less interesting. Exception: rescue an overloaded platform

Lack of Supplies

Early 2000s –  Composite riser and tether for Magnolia (3000 m water depth) –  Composite CNG transport in ships (large tanker) –  Each of these projects alone would have used 1 years world supply of

carbon fibers at that time.

Capacity has increased very much.

Airbus, Boeing and military are still the main carbon fiber customers.

BMW have bought part of a carbon fiber producer to guarantee supplies.

Glass fibers are no problem, wind turbine blades are the biggest consumer.

Production capacity for tubes is limited. Factories for flow lines exist.

Difficult to inspect? Many standard NDT methods do not work

Most subsea components are designed for “no inspection”

Use integrated sensors instead!

Optical fibers can be a good solution:

Foto: NTNU

Foto: NTNU

•  N = 3000, damage = 113 mm •  N = 8000, damage = 132 mm

-150 -100 -50 0 500

500

1000

1500

2000

2500

3000

3500

4000

← →Damage

Patch length [mm] (Center = 0 mm)

Micr

ostra

in

N = 3000N = 8000

Raman Back- scattering

Andreas T. Echtermeyer and Jon Harald L. Grave, “Composite Metal Adhesive Joints – Long-term performance and condition monitoring”, Proceedings: AVT –211 Workshop on Understanding Failure Mechanisms Of Composites For Sustaining & Enhancing Military System Structures, 2013

Difficult to qualify?

To some extend this is a myth

Composites are still new products and need more attention

Standards exist

Relatively high test requirements

High cost? Still small compared to project costs, but high in the development phase

Long time – 10000 hour testing

Main challenge: resistance to long tem degradation

Relevant Documents for Composites

Offshore Standard DNV-OS-C501

COMPOSITE COMPONENTS 2013

DET NORSKE VERITAS

Recommended Practise DNV-RP-F202

COMPOSITE RISERS 2003

DET NORSKE VERITAS

JIP started in summer 1999, completed end of 2001, official DNV document since 2003.

JIP started in summer 2000, completed end of 2001, now official DNV document

Give the same level of safety as standards for metals

API Standards – Flexible Risers

Refers to DNV-OS-C501 for composites

New - Currently JIP document

15#

Anisotropic*Composites*–*Many*Material*Data*

9#Elas)c#proper)es#(12#if#tensile#/#compressive#different)#

9#Strength#values#

Cri)cal#energy#release#rates#

Thermal#expansion#coefficients#

Swelling#coefficients#

+++#

Even%more%if%long%term%proper/es%are%considered%

#

#

Material*Parameters*

16#

Long Term Testing: Carbon Rods for Umbilicals

e↑

f↑

AKER

Too much testing?

Would you like to sit on a plane where the design was based on materials data taken from a text book?

Simplify Long Term Testing

Data interpretation

Data collection

Global Micro Molecular

New JIP Initiative

Most critical component – Endfitting

Difficult to analyze (stress concentrations etc.)

Uncertainty of interface properties.

Proprietary technology

Experience with qualifying composites (risers and others)

Loads are needed more accurately than for metals

Material input data are initially not available. Obtaining them takes time and is costly.

FE analysis a bit more complicated than for metals.

Showing chemical compatibility is not straight forward.

High temperature (80, 100, 120 oC) plus fluid tends to reduce long term properties, especially through thickness strength. Most projects struggle here. These properties should be obtained first!!!

What has been qualified, has worked well.

Less experience / psychological barrier

Maybe the biggest challenge

Many people think composites are exotic

Planes 50%, cars more and more ... Its changing

No standard materials prevent that a good basis of experience and easily available data is built up

Examples of Applications

Pressure Vessels - CNG Transport

A couple of different concepts are being discussed

Patch Repair of corroded plate with composite

Repair without hot-work! JIP project at DNV & EU project

Free falling lifeboats

Impact...

Most Composites are used Subsea

Tethers in each corner

CompTetherTM

Tether Cross Section

PVC Spacers

Strands made up of carbon fiber rods

Outer Jacket

DEEPWATER COMPOSITES!

Spoolable, low weight tether with excellent fatigue properties. Enabling technology for deepwater TLPs!

Subsea Protection Structures

Impact on panels – Numerical model

0o

90o

0o

Composite Air Pressure Vessels

Thermoplastic Composite Pipe

Document long term properties, much testing! JIP guideline has been written DNV RP is being planned

•  Fully bonded flexible pipe, one solid wall, melt-fused

DEEPWATER MODULAR BUOYS DRILLING RISER

BUOYANCY ADCP BUOYS

CompBuoy can deliver material to all this applications

Buoyancy Materials / Elements

Conclusions*

•  Many exciting applications •  The trend going to deep water will increase the use

of composites •  Documentation and understanding of long term

properties under extreme conditions (hot-wet) is a challenge

•  Good design of the composite-metal joint is critical •  Impact resistance is becoming more important

38#

Composites*Offshore*