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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
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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
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