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Transcript of Edit this text for your title Edit this text for your sub-title Presenter name, location, date etc....
Edit this text for your titleEdit this text for your sub-title
Presenter name, location, date etc.
Planer for MEK 4450Marine operasjonerKværner ASA, June 2011
Safety moment
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
Typisk produktinndeling
PipeRigidFlexible
CableElectricUmbilicals
Beam theory. Axial loadCompressionBedning moment
Courtesy: Bredero Shaw
Courtesy: NKT Flexibles
Courtesy: NexansCourtesy: Nexans
Rigid pipe
Large diamterHeavyHigh laying tension
High bending radiusLarge deck spaceExpensive equipment
Plastic deformations acceptableRightning before over boardingAvoid repeated plastic bending!
Thermal isolation (wax formation)
Concrete layers (gas pipes)
Courtesy: Bredero Shaw
Flexible pipes
Low elastic bending radiusLess expensive laying vessels / equipmentMore competition
Separate layers forAxial loadOuter pressureInner pressure
Courtesy: NKT Flexibles
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
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 expensive vessels 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 carry the weight of the product during overboarding. The vertical U- shaped unit at the side of the vessel is called a chute 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 may be 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 forming the 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 of the vessel. The hold-back force is taken by the drum itself. In the stern part there are equipments for straightening out the pipes if there have been plastic deformations and a laying ramp for smooth transition of the product to the sea.
The last two slides shows two other options, particularly useful for laying of rigid pipes. The first case shows a vessel where the new pipe sections are welded to the pipe continuously during over boarding and laying. The huge stinger in the stern of the vessel will prevent critical over bending of the product,- plastic deformation is no longer acceptable 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 is particularily popular in deep water, while the previous solution may be more suited in shallow water.
Typical installation vessels
Installation vessel with horizontal caterpillar og chute
Installation vessel with lay tower
Pipe lay vessel with reel and lay ramp
Pipe lay vessel with stingerSemi-submersibleAnchor vesselDP vessel
Pipe lay vessel with J-lay tower
Installation vessel with horizontal caterpillar and chute
Aker Connector
Tensioner / Caterpillar
Used to pay in / out product, and maintain tension
Belts with pads pushed toward the product. Friction
Sufficient force to Pull 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 friction against pads.
ChuteCable installation
Smooth and even load distribution
Vessel heading restriction
At maximum design tensionChute structural capacityProduct integrity (bending + axial load)Over bending at tip of chute
Top angle from analyses
Installation vessel with lay tower
Scandi Neptune
Pertinacia
Seven Seas
Pipe lay vessel with reel and lay ramp
Pipe lay vessel with stinger
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 exit
Avoid lift-up of pipe in whole stinger
May impact vessel motion characteristics
NOTE: picture shows stinger in elevated, not operational mode
Pipe lay vessel with J-lay tower
Typical laying situation
Picture displaying vessel, water depth, product, and key geometric parameters
A salesman's death
RwH
HDw
H1sin
)sin(1
Dw
T
)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 bøyeradius over touchdown (i ”sag bend”) [m] = Produktvinkel med vertikalen [radianer]D = Vanndyp [m]T = Produktstrekk i øverste 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 fartøy som tåler et gitt toppstrekk. Bør du gripe inn?
D=1000mW=10 kg/mR=5m
H=500N
=0.29 deg!
T=100500N
X=29.98m
Installation analyses
Establish weather criteria and a plan for laying. (Laying tables)
Ensure robust and safe operations for personnel, equipment and flexible product.
Low tension: over bending, axial compression, loop formationHigh tension: rupture, tensioner capacity, free spans
Determine and verify survival conditions
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 over boarding buoyancyAnalysis gives guidance in when to pay in / pay out after installationAnalyses: can the vessel maintain heading and position?
Steep slopes
Uncontrolled sliding of the productAxial compressionFree span formation
Anchor at top of slope?
Another anchor further down?
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
Power cable/umbilical from shore to offshore First 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 to changes in vessel position. Robustness needed
Last end to shore:
More complicated floating
Power cable/umbilical from shore to offshorePlatform end:
Installation through platform J- tubes
Platform 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, platform managers and other unsteady phenomenon.
Floating platform offset
Clash with mooring lines, other risers etc
Over bending at start of J tube
Power cable/umbilical from shore to offshoreInstallation of buoyancy elements:
A “S”- shaped cable configurations at platform may be required.
Buoyancy elements in final stages
Use of clump weights or sea bed abnchoring may also be required
Power cable/umbilical from shore to offshoreChallenges
Compression / overbending near termination of buoyancy elements, touch down etc
Clump weight tangles up
Analyses to determine vessel movements and clump weight
Power cable/umbilical from shore to offshoreSubsea termination
Heavy end termination for subsea plug-in
Bending 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 and
termination during lowering Calculate design loads for product loading