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Presenter name, location, date etc.
Planer for MEK 4450Marine operasjonerKvrner ASA, June 2011
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Safety moment
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Installation of flexibles and cables
Typical productsRigid pipesFlexible pipesCable and umbilicals
Configurations at platform
Installation aids
Installation and installation analyzesInstallation of end terminationsRegular laySpecial challenges: shallow water, deep water, slopes, turns etcWaiting on weather
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Typisk produktinndeling
PipeRigidFlexible
CableElectric
Umbilicals
Beam theory.Axial loadCompressionBedning moment
Courtesy: Bredero Shaw
Courtesy: NKT Flexibles
Courtesy: Nexans
Courtesy: Nexans
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Rigid pipe
Large diamterHeavyHigh laying tension
High bending radiusLarge deck space
Expensive equipment
Plastic deformations acceptableRightning before over boardingAvoid repeated plastic bending!
Thermal isolation (wax formation)
Concrete layers (gas pipes)
Courtesy: Bredero Shaw
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Flexible pipes
Low elastic bending radius
Less expensive laying vessels / equipmentMore competition
Separate layers forAxial loadOuter pressure
Inner pressure
Courtesy: NKT Flexibles
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CablesPower cables and umbilicals
Small radius, bending radius, unit weightLess expensive vessels / equipments
High densityHuge loads on a fully loaded vesselStructural capacity and vessel stability
Combined functionality
No plastic bending
Courtesy: Nexans
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Theory slide. Installation aidsFlexible products are installed with various types of vessels equipped with means / tools for storage and controlled
over boarding of the products. Typically, the installation of rigid steel pipes requires bigger and more expensivevessels due to the huge space and holding capacities required during deck handling and installation.
In the following slides some typical examples are given. The first example show a laying vessels for electrical cables,where the cable are stored on a horizontal turntable. A horizontal caterpillar is used, where a tensioner will carrythe weight of the product during overboarding. The vertical U- shaped unit at the side of the vessel is called achute and prevent damages to the product when it goes into the sea.
We notice that the vessel is equipped with huge crane and a large open deck space. This means that the vessel maybe used for other types of marine operations, like subsea lifting.
Separate slides display the installation equipment used by this vessel. We notice the belt with the orange pads formingthe tensioner. The pads are pushed toward the cable to ensure sufficient friction. By running the belt the cable
may be pulled in or out. The other slide shows the chute.The next slide shows an alternative configurations, where the product are routed via a vertical or almost vertical laying
tower during over boarding. The tensioner are mountd in the laying tower.
The third slide shows a vessels for pipe lay. Steel pipes are spooled on the enormous vertical drum in the centre ofthe vessel. The hold-back force is taken by the drum itself. In the stern part there are equipments forstraightening out the pipes if there have been plastic deformations and a laying ramp for smooth transition of theproduct to the sea.
The last two slides shows two other options, particularly useful for laying of rigid pipes. The first case shows a vesselwhere the new pipe sections are welded to the pipe continuously during over boarding and laying. The hugestinger in the stern of the vessel will prevent critical over bending of the product,- plastic deformation is no longeracceptable as the product are going into the sea and there are no means for straightening it out again.
The last slide displays another alternative, where huge cranes are lifting pipe segments into a vertical J-lay tower.Here the segments are welded to the pipe being laid, again continuously during laying. This solution isparticularily popular in deep water, while the previous solution may be more suited in shallow water.
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Typical installation vessels
Installation vessel with horizontal caterpillar og chuteInstallation vessel with lay tower
Pipe lay vessel with reel and lay ramp
Pipe lay vessel with stinger
Semi-submersibleAnchor vesselDP vessel
Pipe lay vessel with J-lay tower
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Installation vessel with horizontal caterpillar and chute
Aker Connector
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Tensioner / Caterpillar
Used to pay in / out product, and maintaintension
Belts with pads pushed toward the product.Friction
Sufficient force toPull in and overcome friction over chuteKeep cable in position in a storm
High tension + low radial load capacity =long tensioner / many pads
Internal friction may be lower than frictionagainst pads.
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ChuteCable installation
Smooth and even load distributionVessel heading restriction
At maximum design tensionChute structural capacityProduct integrity (bending + axial load)
Over bending at tip of chuteTop angle from analyses
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Installation vessel with lay tower
Scandi Neptune
Pertinacia
Seven Seas
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Pipe lay vessel with reel and lay ramp
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Pipe lay vessel with stinger
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Stinger
Stable support for pipes
Checking with analysis
Rollers to reduce frictionPoint loads
Stinger radius below elastic bending radius
Departure angle high enough to ensure smooth exitAvoid lift-up of pipe in whole stinger
May impact vessel motion characteristics
NOTE: picture shows stinger in elevated, not operational mode
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Pipe lay vessel with J-lay tower
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Typical laying situation
Picture displaying vessel, water depth, product, and keygeometric parameters
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A salesman's death
RwH
HDw
H1sin
)sin(1
DwT
)sin(
)cos(1ln
RX
Bunnstrekk:
Toppvinkel:
Toppstrekk:
Avstand til touchdown:
hvorH = Horisontalt strekk i produktet i touchdown [N]w = Neddykket produktvekt [N/m]R = Minste byeradius over touchdown (i sag bend) [m] = Produktvinkel med vertikalen [radianer]D = Vanndyp [m]T = Produktstrekk i verste ende [N]X = Avstand mellom toppunktet og touchdown
Oppgaven var: en selger vil skaffe firmaet ditt en jobb der en kabel med gitt en gitt kabel skal installeres av et farty som tler etgitt toppstrekk. Br du gripe inn?
D=1000mW=10 kg/mR=5m
H=500N
=0.29 deg!T=100500N
X=29.98m
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Installation analyses
Establish weather criteria and a plan for laying. (Layingtables)
Ensure robust and safe operations for personnel, equipmentand flexible product.
Low tension: over bending, axial compression, loop formation
High tension: rupture, tensioner capacity, free spans
Determine and verify survival conditions
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Survival conditionCutting of product.
More critical for power cables and umbilicals
Installation of buoyancy elementsEstablish flexible S- shaped configurationStep by step analysis to ensure product capacity while overboarding buoyancyAnalysis gives guidance in when to pay in / pay out after
installationAnalyses: can the vessel maintain heading and position?
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Steep slopes
Uncontrolled sliding of the productAxial compressionFree span formation
Anchor at top of slope?
Another anchor further down?
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Other special considerations
Deep waterHigh top tension, tensioner and chute capacityCombined tension and bending at vessel interface
Curve laySliding of productLow laying tensionLaying around preinstalled piles etc
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Power cable/umbilical from shore to offshoreFirst end to shore:
Shallow conditions:Attach buoyancy elementsFloating
Onshore winch pulls in through ditches or tunnelsFriction, uncertain factor
Actual bottom topography, strong currents etc may lead tochanges in vessel position. Robustness needed
Last end to shore:
More complicated floating
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Power cable/umbilical from shore to offshorePlatform end:
Installation through platform J- tubesPlatform winch and forerunner through J- tubes
Coupling of power cable / forerunner at vessel deck.
Pull-in through J- tubes by platform winch.
Challenges:Plans for vessel positions changed due to wind, platformmanagers and other unsteady phenomenon.
Floating platform offset
Clash with mooring lines, other risers etcOver bending at start of J tube
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Power cable/umbilical from shore to offshoreInstallation of buoyancy elements:
A S- shaped cable configurations at platform may berequired.
Buoyancy elements in final stages
Use of clump weights or sea bed abnchoring may also berequired
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Power cable/umbilical from shore to offshoreChallenges
Compression / overbending near termination of buoyancyelements, touch down etc
Clump weight tangles up
Analyses to determine vessel movements and clump weight
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Power cable/umbilical from shore to offshoreSubsea termination
Heavy end termination for subsea plug-inBending restrictor or similar at neck
Focus on bending moments at neck
Lowered by the cable: head fall over
Lowered by crane more controlled, but requires separation
Analysis
Reveal need for crane
Determine required separation between crane tip andtermination during lowering
Calculate design loads for product loading
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