GRP Offshore Applications and design for firecosacnet/ACIC2002/Monday/m1700Davies.pdf · GRP...

GRP OffshoreApplications and design for fire

Professor J Michael DaviesUniversity of Manchester

The first major application of composites in the North Sea

Helideck fire protection. Amerada Hess Rob Roy rig, early 1980’s

Davy and Bessemer monopod platforms

10% by weight of composite materials in the topside structures:[gratings, handrails, heat protection walls, pipework, etc]

Applications of composites offshoreRecent applications:

_______________________________________________________________Fire protection Walkways and flooring LifeboatsBlast protection Handrails Buoys and floatsCorrosion protection Sub-sea anti-trawl structures ESDV protectionPartition walls Casings Boxes and housings Aqueous pipe systems J-tubes Loading gantriesTanks and vessels Caissons Pipe refurbishmentFirewater systems Cable trays and ladders Riser protectionPipe liners Accumulator bottles Bend restrictorsSeparator internals Well intervention Sub-sea instrument housings_______________________________________________________________

Future applications:_______________________________________________________________Rigid risers Coilable tubing Flexible risersTendons Primary structure Separators_______________________________________________________________

Benefits of using composites offshore:

High strength to weight ratioNo corrosionEase of handling and installation

Barriers to the use of composites offshore:

Cost (less critical than in on-shore construction)Performance in (hydrocarbon) fireLow stiffness (certain applications only)Regulatory requirements (especially on combustibility)Lack of performance informationLack of design procedures and working standardsFragmented structure of the composites industryDifficulty of scaling up fabrication processes to makevery large composite structures

Davy and Bessemer monopod platforms

As a design exercise, carried out by Maunsell Structural Plastics and Odebrecht SLP, these platforms were redesigned to make the maximum possible use of composite materials in the topside structures.In the “conforming design” (same floor design, dimensions etc as the original), the weight saving was 38% with a modest reduction in cost.The “radical” option produced significantly greater weight and cost savings.

Candidate resin systems for use offshore

Polyester and vinyl ester are the general purpose resinsEpoxy is used where strength is important (pipework)Phenolic resins are used where improved fire resistance or reduced smoke and toxicity are requiredModified acrylic resins (eg Modar) may also be used in toxicity-sensitive areas but are not yet widely used offshore

Glass fibre reinforced epoxy pipework

Generally filament wound GGE.

Other resin types are polyester, vinyl ester and phenolic (for fire-critical situations).

Relatively immune to damage from the main organic components of crude oil.

Common joints for Common joints for fibreglass fibreglass pipeworkpipework

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Rubber seal or Key-Lock Threaded

Adhesively bonded jointsTaper-taper Quick-lock

Socket and spigot

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Mechanical joints

Steel strip laminate (SSL) pipeField assembly of the “coil lock” joint

Conventional glass/epoxy inner and outer layersInternal, helically wound layers of high tensile steel stripCapable of handling oilfield fluids at up to 100 bar

Thermoplastic (RTP) pipeThermoplastic inner liner,helically wound reinforcementtypically aramid (eg Kevlar),thermoplastic outer cover

Field trial of low cost flexible RTP for oilfield fluids

Rigid composite production risers250-550 mm diameter high performance tubes

with pressure ratings ; 1000 bar

Specimens prepared for qualification testing

Composite high pressure gas accumulator bottles

On the riser tensioning assembly of a tension leg platform

GRP repair of an externally corroded pipe

Carbon fibre repair of a 350 mm tee joint on a seawater return header

Composite combined corrosion and fire protection applied to a

platform jacket leg

Composites in blast and fire walls

Usually used in sandwich configuration tomaximise stiffness and fire integrityWeight savings of the order of 30% comparedwith traditional corrugated steel fire and blastwall structuresDo not corrode or require painting

There are interesting developments in fireresisting core materials

Composite blast and fire protection of ESDV equipment

Two-skin sandwich construction comprising pultruded skins and a calcium-silicate based core

Pultruded phenolic gratings

On a tension leg platform in the Gulf of Mexico.The Ursa TLP incorporated over 20000m2 of phenolic grating.

Manchester School of EngineeringThree gas-fired furnaces with

computer control

Furnace No. 1: 2m x 2m x 2m working volumeNote portable burner unit at right hand side

Furnace No. 2:For testing sub-frames under load

Fire Scenario for deluge systems

• Ring main is full of stagnant water at all times

• Ring main supplies dry riser pipes which feed sprinkler heads

• When activated automatically, the deluge system is normally running within 30 seconds

• Manual activation may require as long as 3 to 5 minutes

Three distinct conditions to consider in a deluge system

using polymer composite pipes:

• Pipes empty and dry

• Pipes filled with stagnant water

• Pipes filled with flowing water

The empty and dry condition is by far the most critical

Initial test procedure for the empty and dry condition

• 1 metre long length of pipe inserted in furnace with ends plugged with ceramic wool

• Furnace run for desired period following hydrocarbon time-temperature curve

• Burner turned off and pipe withdrawn. Any flames extinguished using carbon dioxide

• Pipe stood on end and filled with water (inside of pipe only) to cool

• Pipe trimmed to length and pressure tested. Maintainable pressure over 3 minutes recorded

Fire testing of dry empty GRP

pipesThis is why it is the “initial” test method!

It was subsequently found that the attainment of an internal wall temperature of 200oC was a sufficient criterion of failure

Results for empty unprotected pipes

Proprietary filament wound glass-epoxy pipes (Ameron Bondstrand 2000M were used for all tests

Various diameters, wall thickness generally4.3 to 4.6 mm

It is clear that some form of protection is essential

Pipes with thick intumescent protection(a) 100mm dia. pipe with 7.5mm unreinforced Pitt-Char(b) 100mm dia. pipe with 11.5 mm reinforced Pitt-CharResults were similar. Critical temperature of 200oC at inside face reached after about 11 minutes:

Ceramic fibre fire protection of pipesAmeron 200 pipes with additional layers 3.5 mm ceramic

blanket + 2 layers of wetted out woven glass roving

Results of pressure testing pipes after 3 minutes hydrocarbon exposure

Results of pressure testing pipes after 5 minutes hydrocarbon exposure

Jointed pipes in the empty and dry condition

Simple bell and spigot type joint

Testing of pipes in stagnant and flowing water condition

50mm diameter GRE pipe with water flowing at 18 litres per minute

Test results: 50 mm dia. pipe5 minutes stagnant water followed by flow

at 18 litres per minute

Summarised results for fire tests on water-filled pipes

Furnace fire testing of water-filled pipesInter-cooled water supply

More realistic flow rate100 mm dia. GRE pipe with water flowing at

240 litres per minute

Numerical modelling of GRP pipes exposed to (hydrocarbon) fires

• The mathematical model is relatively simple and attempts to replicate the main features of the pyrolosis process and the consequent heat transfer

• It is one-dimensional using polar coordinates and a finite difference solution process

• Various other models also exist in 2 and 3-D in polar and cartesion coordinates

• The basic equations are given in the printed paper and expanded in the quoted References

Numerical modelling of GRP pipes exposed to (hydrocarbon) fires

Main assumptions• The material is homogeneous and all heat and mass

transfer is perpendicular to the faces• There is thermal equilibrium between the decomposition

gasses and the solid material• There is no accumulation of decomposition gasses

within the solid material• The feedback of energy from the flaming of released

volatiles may be ignored• Significant delamination of the GRP matrix does not

occur• Various boundary conditions on the (cold) inside surface

Numerical modelling of GRP pipes exposed to (hydrocarbon) fires

• The most difficult problem is determining the values of the material properties (which are temperature-dependent)

• There is insufficient information in the available technical literature

• The project uses the available information modified by comparison of the test and analytical results

Comparison of numerical and experimental results

Empty 100 mm diameter GRE pipe

Calculated and observed behaviour of a 100 mm dia. pipe

filled with stagnant water

Calculated and observed behaviour of a 100 mm dia. pipe filled with flowing

water at 18 litres/min

Gratings under test

Component test

Complete grating(load from below)

Performance of pultruded primary members at elevated temperature

0.01.02.03.04.05.06.07.08.09.0

Amb 60°C 75°C 90°C 105°C 120°C

Temperature (°C)

Failu

re L

oad

(kN)

Test Sample Single Section

0.00

5.00

10.00

15.00

20.00

25.00

30.00

AMB 60 75 90 105 120

Temperature (°C)

E (k

N/m

m²)

Strength

Stiffness

Compression tests at elevated temperature

Upper Support - Steel tube filled with ConcreteUpper Loading Plate

Lower Support - Steel tube filled with Concrete

Lower Loading Plate

Load Cell

Jack

Test Specimen

Kiln Furnace

Loading Frame

% of Ambient Load ReachedBefore Failure

0

20

40

60

80

100

Amb 60 90 120 150 200 250

Temperature (°C)

% R

etai

ned

Stringer panel construction

Plasterboard Facing

Plasterboard Facing

Mineral Wool Core

GRP Stringer

730 °C

315 °C

284 °C 81 °C

58 °C 69 °C

40 °C 39 °C

23 °C

Temperatures in the GRP stringer after 30 minutes testing (cellulosic fire)

Acknowledgement

Many of the pictures of applications offshore were provided by Professor A G Gibson, Centre for Composite Materials Engineering, University of Newcastle upon Tyne by courtesy of:Vosper Thorneycroft (UK) Ltd, BP-Amoco, Ameron BV, Tubes D-Aquitaine, Pipelife BV, Lincoln Composites, Clockspring Ltd, DML and Strongwell

100 mm diameter GRE pipe with 10 minutes of stagnant water followed by flowing water at 18 litres per minute

Comparison of numerical and experimental results

Empty 75mm dia. pipe - cellulosic curve

Comparison of numerical and experimental results

Empty 5.6 mm thick phenolic pipe

Comparison of numerical and experimental results

Empty 9.5 mm thick phenolic pipe