Edit this text for your title MEK 4450 Marine Operations 1-3 Edit this text for your sub-title Presenter name, location, date etc. Kværner ASA / DNV, Fall 2014
Installation of flexibles and cables Typical products Rigid pipes Flexible pipes Cables and umbilicals Installation and installation analyses Installation of end terminations Regular laying Special challenges: shallow water, deep water, slopes, turns etc Waiting on weather
Typical product categories Pipe Rigid Flexible Cable Electric Umbilicals Beam theory. Axial load Compression Bedning moment Courtesy: Nexans Courtesy: NKT Flexibles Courtesy: Nexans Courtesy: Bredero Shaw
Rigid pipe Large diameter Heavy High laying tension High bending radius Large deck space Expensive equipment Some plastic deformation acceptable Straightening before over-boarding Avoid repeated plastic bending Thermal insulation (wax formation) Concrete weight 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 Smaller bending radius, lower unit weight Less expensive vessels / equipment High density Heavy load on a fully loaded vessel Structural capacity and vessel stability Limited plastic bending Courtesy: Nexans
Typical installation vessels Installation vessel with horizontal tensioner and chute Installation vessel with lay tower Pipe lay vessel with reel and lay ramp Pipe lay vessel with stinger DP vessel Anchor vessel Pipe lay vessel with J-lay tower
Installation vessel with horizontal tensioner and chute Aker Connector
Tensioner / Caterpillar Used to pay in / out product, and to maintain/ support cable tension Belts with pads press against the product Sufficient force to Pull in and overcome friction over chute Support maximum cable tension (e.g. storm) High tension + low radial load capacity => long tensioner / many pads Internal friction in the cable may be lower than friction between cable and pads!
Chute Cable installation Provides continuous support Introduces vessel heading restrictions At maximum design tension Chute structural capacity Product integrity (bending + tension) 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 Provides support for pipes Rollers to reduce friction (=> point loads) Stinger radius above elastic bending radius of pipe Departure angle high enough to prevent over-bending Avoid lift-up of pipe in stinger Will impact vessel motion characteristics NOTE: picture shows stinger in elevated, not operational mode
Pipe lay vessel with J-lay tower Pipe sections raised into vertical Vertical welding of pipe sections Pipe tension supported by clamps
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 Ensure that all tolerances are accounted for Determine and verify survival conditions
Installation analyses Shore landing Pull-in to shore Shallow lay
Installation analyses Uphill vs downhill lay Downhill lay More flexible catenary (reduced risk of cable overbending/compression) May cause high seabed tension and free spans Uphill lay Less flexible catenary (due to geometry) => reduced weather criteria Risk of cable sliding downhill
Installation analyses Laying in steep slopes Difficulty in assessing where actual touchdown point is => step-by-step analyses as input to operational procedures
Installation analyses General considerations (analyses) Deep water High top tension, tensioner capacity Combined tension and bending at vessel interface Curve lay Sliding of product Low lay tension (risk of over-bending/compression) Possible solution: Laying around preinstalled piles etc
Installation analyses Installation of buoyancy elements Step-by step analyses to Determine vessel movements vs. pay-out of pipe/cable Establish procedure for attachment/lowering of clump weight Main challenges Over-bending/compression at vessel interface due to buoyancy
Installation analyses Pull-in to platform Step-by step analyses to Determine lowering of pipe/cable from vessel vs pull-in to platform Main challenges Vessel positioning (available space) Seabed clearance Over-bending at I-tube inlet
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?