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OFFSHORE ENERGY

Turret Design and Operational Integrity

Andrew Newport, Technology Director, SBM Offshore

Turret Design and Operational Integrity

19.09.2017 2

Overview of turret mooring systems

Design and Operational integrity

Overview of the Stones turret mooring

1

2

3

Weathervaning systems

Turret System Components

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Internal versus External

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Permanent versus Disconnectable

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16 floating units in the fleet

USA

Brazil

Equatorial Guinea

Angola

Asia

Turnkey turrets

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Turret Design and Operational Integrity

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Overview of turret mooring systems

Design and Operational integrity

Mooring legs and Out of Plane (OPB) bending

Weathervaning system

Swivels

Overview of the Stones turret mooring

1

2

3

Mooring legs

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Traditional chain connectors

Anchor Leg Configuration

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Out of Plane Bending Fatigue

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T

T

M B

Interlink angle

4d a total

Tension

Angle

a int M A

MA=-MB+Tsin( a total - a int )*4d

Out of Plane Bending (OPB) fatigue was first identified in 2002 (Girasol Deep Water Buoy)

OPB Guidance

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OTC-25779-MS Chain Out of Plane Bending (OPB) Joint

Industry Project (JIP) Summary and Main Results Lucile Rampi,

SBM Offshore, Fata Dewi, SBM Offshore, Pedro Vargas, Chevron

OMAE2016-54195 Chain Out of Plane Bending (OPB) Joint

Industry Project (JIP) Static Test Program and OPB Interlink

Stiffness Lucile Rampi, SBM Offshore, Fata Dewi, SBM Offshore, Michel Francois, Bureau Veritas,

Arnaud Gerthoffert, Bureau Veritas, Pedro Vargas, Chevron Energy Technology Co.

OMAE2016-54198 Chain Out of Plane Bending (OPB) Joint

Industry Project (JIP) FEA Results and Multiaxiality Study

Results Lucile Rampi, SBM Offshore, Andre Bignonnet, Ab Consulting, Cedric Le Cunff, Principia,

Francois Bourgin, Principia, Pedro Vargas, Chevron Energy Technology Co

OMAE2016-54199 Chain Out of Plane Bending (OPB) Joint

Industry Project (JIP) Fatigue Test Program Result and

Methodology Lucile Rampi, SBM Offshore, Arnaud Gerthoffert, Bureau Veritas, Michel

Francois, Bureau Veritas, Andre Bignonnet, Ab Consulting, Pedro Vargas, Chevron Energy Technology

Co.

Double articulated chain connector

Hawse Pipe

Chain

Roll Body

Pitch Body

Long hawse pipe and low friction bushes ensures the connector rotates before the chain links bend significantly

Articulated Rod Connecting Arm (ARCA)

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Technology Readiness Level 4

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Turret Design and Operational Integrity

19.09.2017 18

Overview of turret mooring systems

Design and Operational integrity

Mooring legs and Out of Plane (OPB) bending

Weathervaning system

Swivels

Overview of the Stones turret mooring

1

2

3

Load transfer between fixed turret and rotating vessel

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Single forged 3 race roller bearings are limited to approximate 10m diameter. This limits load capacity and riser count.

Segmental Bearings

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• Segmental bearings can be used on top mounted turrets and external turrets

• Available in diameters up to 21m, but with limited offshore experience

3 race roller bearings are used in all main turret configurations

External BMIT TMIT

Loads on the bearing

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• Mooring and riser loads

• Inertia of the turret system

• Vessel deformations

• Bearing companion structure deformations

Loads on the bearing

• Mooring loads, riser loads and inertia loads are all directly imposed on the bearing system

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Hull hogging and sagging ovalizes the deck around the moonpool

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Isolated from vessel deformations to avoid additional loads on rollers

Bearing support structure (Rotating part) Bearing

Seals

arrangements

Outer

ring

Inner &

Outer

bolts

Inner

ring Rollers

Companion structure deformations must be limited

Regular slamming loads on the bearing should be avoided

Bogie bearings provide a high capacity alternative to roller bearings

• Virtually no limit on riser number

• Virtually no limit on mooring loads

• Bogies and radial wheels are standard components

• Bogies and radial wheels are inspectable and replaceable

The bogie bearing system incorporates bogies and radial wheels

GANTRY

Sea level

TO TOPSIDE

BOGIES

RADIAL WHEELS DECOUPLING BOGIE SUPPORT

STRUCTURE

Lowering the turret cyclinder through the moonpool

• Bogies support axial loads

• Radial wheels support radial loads

• The bogie design is standard, and the number used is selected to accommodate the design loads (N+1)

• Dry access in turret for inspection and maintenance

The system provides dry access for inspection and maintenance

Stoppers gives a massive increase in load capacity for extreme events

• Gap only closed during extreme loads

• Lower stoppers then provide additional load path

• Lower stoppers limit uplift on the bogies

SCHIEHALLION SKARV, PRELUDE, ICHTYS

Mooring force ~ 2000T Mooring force > 5000T

Turret Design and Operational Integrity

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Overview of turret mooring systems

Design and Operational integrity

Mooring legs and Out of Plane (OPB) bending

Weathervaning system

Swivels

Overview of the Stones turret mooring

1

2

3

Swivels transfer fluids, utilities, power and signals

A range of swivel types are required

Fluid Swivels for oil, water and gas

(Pipe Swivels)

Fluid Swivels for oil, water and gas

(Toroidal Swivels)

Electrical and Optical Swivels for the

transfer of power and signals /

information

Utility Swivels for transfer of

chemicals, hydraulics, air/gas,

firewater and vents)

Swivels are assembled into swivel

stacks

Torodial fluid swivels are the principal component of most swivel stacks

Sealing concepts are fundamental to swivel design

Isolation & primary

seals form the Oil

Barrier cavity

The Oil Barrier is

maintained at a higher

pressure than the

process fluid

Secondary seals are

used to back-up primary

seals, and permit leak

monitoring

Seal replacement method should minimize disruption to production

SBM’s approach is to pre-

installed spare seals

Seals can also be replaced

in-situ using seal welding

technology

No impact on adjacent

swivels

Tools to aid seal change-

out are provided with the

swivel stack

Seals can be replaced in-situ

Turret Design and Operational Integrity

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Overview of turret mooring systems

Design and Operational integrity

Overview of the Stones turret mooring

1

2

3

The Stones fieldis located 200 miles (320 km) south of New Orleans

FPSO Turritella is an Suezmax conversion with 7000 t topsides

The novelty was concentrated in the turret mooring system

• Remains connected in winter storms

• Disconnectable to avoid hurricanes

• Installed in 2,900m water depth

• Buoy supports steel lazy wave risers (SLWR)

• 6000 t displacement buoy • Buoy is a hybrid construction

of steel and syntactic foam • Heave compensation system

provided to pull in the buoy • Distributed locking system to

connect and disconnect the buoy

Syntactic foam used to counter high water pressure on the buoy

A trial fit of the lower turret and buoy was carried out in the fabrication yard

A distributed locking system connects the buoy to the turret

A generic prototype was developed to reach TRL 4

The locking devices were installed in the lower turret prior to integration

Successful dynamic drop test of the buoy

Installation of the bogie bearing support

The first application of steel risers on a disconnectable mooring system

Summary

Operational integrity is highly dependent upon the system design, particularly at component level

Out of Plane (OPB) bending fatigue is now recognized and well understood, and chain connector design must account for this phenomenon

Bearing design must account for all external loads, including future loads and the effects of the riser installation program.

The bearing companion structure should be stiff enough to avoid excessive deflections of the bearing, and should isolate the bearing from deck strains

A distributed bearing system such as a bogie bearing allows redundancy in design, and the ability to change out components offshore

In the event of damage to a seal, quick seal change-out with minimum disruption to production is paramount

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Thank you for your attention

Andrew Newport Technology Director

SBM Offshore