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Planer for MEK 4450
Marine operasjoner
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Presenter name, location, date etc.
Kværner ASA, June 2011
Safety moment
Installation of flexibles and cables
Typical products
Rigid pipes
Flexible pipes
Cable and umbilicals
Configurations at platform
Installation aids
Installation and installation analyzes
Installation of end terminations
Regular lay
Special challenges: shallow water, deep water, slopes, turns etc
Waiting on weather
Typisk produktinndeling
Pipe
Rigid
Flexible
Cable
Electric
Umbilicals
Courtesy: Bredero Shaw
Beam theory.
Courtesy: NKT Flexibles
Axial load
Compression
Bedning moment
Courtesy: Nexans
Courtesy: Nexans
Rigid pipe
Large diamter
Heavy
High laying tension
High bending radius
Large deck space
Expensive equipment
Plastic deformations acceptable
Rightning before over boarding
Avoid repeated plastic bending!
Thermal isolation (wax formation)
Concrete layers (gas pipes)
Courtesy: Bredero Shaw
Flexible pipes
Low elastic bending radius
Less expensive laying vessels / equipment
More competition
Separate layers for
Axial load
Outer pressure
Inner pressure
Courtesy: NKT Flexibles
Cables
Power cables and umbilicals
Small radius, bending radius, unit weight
Less expensive vessels / equipments
High density
Huge loads on a fully loaded vessel
Structural capacity and vessel stability
Combined functionality
No plastic bending
Courtesy: Nexans
Theory slide. Installation aids
Flexible 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 stinger
Semi-submersible
Anchor vessel
DP 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 chute
Keep 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.
Chute
Cable installation
Smooth and even load distribution
Vessel heading restriction
At maximum design tension
Chute structural capacity
Product integrity (bending + axial load)
Over bending at tip of chute
Top angle from analyses
Installation vessel with lay tower
Seven Seas
Scandi Neptune
Pertinacia
Pipe lay vessel with reel and lay ramp
Pipe lay vessel with stinger
Stinger
Stable support for pipes
Checking with analysis
Rollers to reduce friction
Point 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
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=1000m
W=10 kg/m
R=5m
Bunnstrekk:
H  w R
Toppvinkel:
  sin 1 
H



 w D  H 
T
Toppstrekk:
w D
1  sin(  )
Avstand til touchdown:
hvor
H
w
R

D
T
X
H=500N
=
=
=
=
=
=
=
=0.29 deg!
T=100500N
 1  cos( ) 

X  R  ln 
 sin(  ) 
X=29.98m
Horisontalt strekk i produktet i touchdown [N]
Neddykket produktvekt [N/m]
Minste bøyeradius over touchdown (i ”sag bend”) [m]
Produktvinkel med vertikalen [radianer]
Vanndyp [m]
Produktstrekk i øverste ende [N]
Avstand mellom toppunktet og touchdown
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 formation
High tension: rupture, tensioner capacity, free spans
Determine and verify survival conditions
Survival condition
Cutting of product.
More critical for power cables and umbilicals
Installation of buoyancy elements
Establish flexible ”S”- shaped configuration
Step by step analysis to ensure product capacity while over
boarding buoyancy
Analysis gives guidance in when to pay in / pay out after
installation
Analyses: can the vessel maintain heading and position?
Steep slopes
Uncontrolled sliding of the product
Axial compression
Free span formation
Anchor at top of slope?
Another anchor further down?
Other special considerations
Deep water
High top tension, tensioner and chute capacity
Combined tension and bending at vessel interface
Curve lay
Sliding of product
Low laying tension
Laying around preinstalled piles etc
Power cable/umbilical from shore to offshore
First end to shore:
Shallow conditions:
Attach buoyancy elements
Floating
Onshore winch pulls in through ditches or tunnels
Friction, 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 offshore
Platform 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 offshore
Installation 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 offshore
Challenges
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 offshore
Subsea 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