Introducing Hengtong Marine • Hengtong Marine manufacture Submarine Cable Systems • Power, Optical Fibre, Hybrid and Umbilical Cables • Submarine Optical Cables are UJ & UQJ certified • Current optical cable capacity 6500km, which is being upgraded to 12,000km by end 2016 On-Bottom (Sea Bed) Stability Design of Cables Hengtong Marine Presentation to ICPC Plenary April 2016
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Introducing Hengtong Marine• Hengtong Marine manufacture Submarine Cable Systems • Power, Optical Fibre, Hybrid and Umbilical Cables• Submarine Optical Cables are UJ & UQJ certified• Current optical cable capacity 6500km, which is being
upgraded to 12,000km by end 2016
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Hengtong Group – Fibre Products
kilometers of fiber per year
Sold in more than countries and regions
12 production bases around the world
50 million
Hengtong Industry Chain
Fiber Preform
Optical Fiber
Cable
Component and connection system
EPC and turn-key project service
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
On-Bottom (Sea Bed) Stability Design of Cables
Hengtong Marine Cable Systems
Presenter : Dr. Jerry Brown
ICPC Plenary Meeting: 12 April 2016 Hamburg
ICPC Plenary April 2016
www.hengtongmarine.com
Audience Participation(Wake Up & Stretch Your Arms)
• How many people know about DNV-RP-F109 ?• How many people have used DNV-RP-F109 ?• Do you think a DNV recommended practice for
pipelines (typically 76mm to 1800mm diameter & concrete coated) is really applicable to flexible cables (typically 18mm to 40mm diameter) ?
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Why is On-Bottom Cable Stability Important ?• The cable should remain on the as laid cable route
– for ease of location – recovery during future maintenance operations
• For the convenience of other seabed users – to avoid damaging any adjacent equipment, – sensitive or protected marine organisms and
• To avoid cable damage – due to abrasion, – kinking,– fatigue failure due to repeated flexing and bending.
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
• Seabed Type• Roughness• Properties• Friction
coefficient• Cable
penetration• Trench
Depth
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Factors which affect Cable Stability ?
• Cable Diameter
• Cable Weight• Cable Lay
direction• Marine
Growth & density
• Wave direction• Significant Wave
Height• Peak Wave Period• Current Speed &
Direction• Reference height
for current• Water depth
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Cable Design For Stability• TIMING - During the Cable system route engineering, the cable on-
bottom stability should be checked.• CHECK LIST - These checks are often not completed at the design
stage due to a lack of environmental data, or they are over-looked by clients / suppliers.
• DESIGN - On-bottom stability checks completed at the correct time, allows the cable design (armouring) and engineering to be adjusted to meet the site conditions and client requirements… for a reasonable cost.
• TOO LATE - Often the reality is that the cable is manufactured (or deployed) before on-bottom stability is considered.
• FIX - A retro-fitted solution has to be engineered = increased costs.
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
CDrag = CLift= 1.2 μ = 0.5 for armoured cables on rock and sandμ = 0.2 for armoured & LW cables on clay, silt, mud
• Seabed Type• Roughness• Properties• Friction
coefficient• Cable
penetration• Trench Depth
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
The Classical Theory uses some parameters
• Cable Diameter
• Cable Weight• Cable Lay
direction• Marine
Growth & density
• Wave direction• Significant Wave
Height• Peak Wave Period• Current Speed &
Direction• Reference height
for current• Water depth
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Cable
Marine Growth
Knowing the density of the Marine Growth and assuming the cross section of growth shown above, allows an equivalent ‘cable with growth’ diameter & weight in water to be calculated
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
LWP
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
DNV-RP-F109 On-Bottom Stability Design of Submarine Pipelines
• DNV-RP-F109 2007, revised in 10/10, and amended in 11/11. • Analyses the stability characteristics of a circular CSA pipeline
(diameter and weight). Considers water depth, seabed type and environmental conditions (i.e. current and wave profiles).
• Three different design approaches to analyzing pipeline stability • 1st …. calculations for absolute (zero movement) static stability, • 2nd …. calculations for a generalized stability method with design
curves for virtually stable pipes (allowing up to 0.5 diameters lateral displacement) and for up to 10 pipe diameters displacement in an extreme storm condition.
• 3rd …. is based on a full dynamic analysis method.
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
DNV-RP-F109 - Parameters Used … … … … … … but are they all necessary ?
• Cable Diameter
• Cable Weight• Cable Lay
direction• Marine
Growth & density
• Wave direction• Significant Wave
Height• Peak Wave Period• Current Speed &
Direction• Reference height
for current• Water depth
• Seabed Type• Roughness• Properties• Friction
coefficient• Cable
penetration• Trench Depth
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
DNV-RP-F109 – DNV have released STABLELINES … … … … … …Hengtong Marine have verified our software against STABLELINES
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
The Effect of Waves on Seabed Stability of DA cable using DV-RP-F109 (Absolute Stability Method)
DNV-RP-F109 (Absolute Stability Method) Versus Classical Theory for DA cable
Considering the effect of only Current on the Sea Bed Stability of Cables
DNV-RP-F109 provides more conservative results when using a reference height = cable diameter
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Affect of Bottom Roughness on Current Profiles
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Affect of Trench Depth on Stability
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
For a cable bundle dimensions D x 2D, the stability analysis can be simplified and approximated to a circular cable, diameter D with a perpendicular current V90 which is half the current acting on the bundle.
Stability Analysis of Cable Bundles
Affect of Cable Aspect Ratio (Dmax/Dmin)
• As the Cable Body Aspect Ratio increases, seabed stability increases• The current reduction factor allows a circular cable stability analysis with a
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Methods of Improving Seabed Stability of Cables• Change the weight of the cable
– Cable design (additional layers of armour)– Addition of modular ballast elements– Application of protective pipes– Clamp or Pin the Cable to the seabed
• Change the cable profile– Attachment of Ballast Wire (Cable Bundle)– Cover with Mattress (low profile shape)
• Burial of the cable– Rock Dumping– Trenching
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Comparison of Stability Methods
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
On-Bottom (Sea Bed) Stability Design of CablesHengtong Marine Presentation to ICPC Plenary April 2016
Conclusions• Two On-Bottom Stability Calculation methods have been
introduced & results compared • The comprehensive capability of DNV-RP-F109 has been
demonstrated. There are limitations. DNV is working on a joint program to develop an amendment to enhance RP-F109 for flexible cables
• An analysis technique for cable bundles proposed• Some methods of improving on-bottom stability of cables
have been reviewed• Hengtong Marine are developing new methods of