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1 Edit this text for your title MEK 4450Marine OperationsEdit this text for your sub-titlePresenter name, location, date etc.Kværner ASA / DNV, Fall 2012
2 Installation of flexibles and cables Typical productsRigid pipesFlexible pipesCables and umbilicalsInstallation and installation analysesInstallation of end terminationsRegular layingSpecial challenges: shallow water, deep water, slopes, turns etcWaiting on weather
5 Flexible pipes Low elastic bending radius Separate layers for Less expensive laying vessels / equipmentMore competitionSeparate layers forAxial loadOuter pressureInner pressureCourtesy: NKT Flexibles
6 Cables Power cables and umbilicals Smaller bending radius, lower unit weightLess expensive vessels / equipmentHigh densityHeavy load on a fully loaded vesselStructural capacity and vessel stabilityLimited plastic bendingCourtesy: Nexans
7 Theory slide. Installation aids Flexible products are installed with various types of vessels with equipment 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 large space and high tension capacity required during deck handling and installation.In the following slides some typical examples are given. The first example shows a laying vessels for electrical cables, where the cables are stored in a horizontal carousel. A horizontal tensioner is used that carries the weight of the cable during laying. The chute over the side of the vessel provides support and prevents damage to the cable as it is over-boarded.We notice that the vessel is equipped with a big crane and a large open deck space. This means that the vessel may be used for other types of marine operations such as installation of subsea modules.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 configuration, where the cable is routed via a vertical laying tower during installation. The tensioners are vertically mounted in the laying tower.The third slide shows a vessel for installation of small diameter rigid pipe (typically < 12” or 16”). Steel pipes are spooled (and deformed plastically) on the large vertical drum in the center of the vessel and installed over a lay ramp. The ramp may be tilted, typically to support a pipe lay angle of degrees. A tensioner that supports pipe lay tension is positioned on the lay ramp, while the reel ensures back-tension. The lay ramp also includes a straightener and a welding/x-ray station.The next two slides show installation vessels with stingers, typically used for installation of large diameter rigid pipes (> 16” or 20”). Pipe sections (typically 12 m long) are continuously welded to the pipe string during laying. The large stinger at the stern of the vessel ensures that the pipe is not plastically deformed as straightening is not possible.The last slide displays a typical J-lay vessel for installation of large diameter rigid pipe in deep water. Pipe segments are lifted into the vertical “J-lay tower” by use of specialized cranes, and then welded to the pipe string during laying.
8 Typical installation vessels Installation vessel with horizontal tensioner and chuteInstallation vessel with lay towerPipe lay vessel with reel and lay rampPipe lay vessel with stingerDP vesselAnchor vesselPipe lay vessel with J-lay tower
9 Installation vessel with horizontal tensioner and chute Aker Connector
10 Tensioner / Caterpillar Used to pay in / out product, and to maintain/ support cable tensionBelts with pads press against the productSufficient force toPull in and overcome friction over chuteSupport maximum cable tension (e.g. storm)High tension + low radial load capacity => long tensioner / many padsInternal friction in the cable may be lower than friction between cable and pads!
11 Chute Cable installation Provides continuous support Introduces vessel heading restrictionsAt maximum design tensionChute structural capacityProduct integrity (bending + tension)Over-bending at tip of chute (top angle from analyses)
12 Installation vessel with lay tower Seven SeasScandi NeptunePertinacia
15 Stinger Provides support for pipes Rollers to reduce friction (=> point loads)Stinger radius above elastic bending radius of pipeDeparture angle high enough to prevent over-bendingAvoid lift-up of pipe in stingerWill impact vessel motion characteristicsNOTE: picture shows stinger in elevated, not operational mode
16 Pipe lay vessel with J-lay tower Pipe sections raised into verticalVertical welding of pipe sectionsPipe tension supported by clamps
17 Installation analyses Establish weather criteria and a plan for laying (laying tables)Ensure robust and safe operations for personnel, equipment and flexible productLow tension: over bending, axial compression, loop formationHigh tension: rupture, tensioner capacity, free spansEnsure that all tolerances are accounted forDetermine and verify survival conditions
18 Installation analyses Shore landingPull-in to shoreShallow lay
19 Installation analyses Uphill vs downhill layDownhill layMore flexible catenary (reduced risk of cable over-bending/compression)May cause high seabed tension and free spansUphill layLess flexible catenary (due to geometry) => reduced weather criteriaRisk of cable sliding downhill
20 Installation analyses Laying in steep slopesDifficulty in assessing where actual touchdown point is => step-by-step analyses as input to operational procedures
21 Installation analyses General considerations (analyses)Deep waterHigh top tension, tensioner capacityCombined tension and bending at vessel interfaceCurve laySliding of productLow lay tension (risk of over-bending/compression)Possible solution: Laying around preinstalled piles etc
22 Installation analyses Installation of buoyancy elementsStep-by step analyses toDetermine vessel movements vs. pay-out of pipe/cableEstablish procedure for attachment/lowering of clump weightMain challengesOver-bending/compression at vessel interface due to buoyancy
23 Installation analyses Pull-in to platformStep-by step analyses toDetermine lowering of pipe/cable from vessel vs pull-in to platformMain challengesVessel positioning (available space)Seabed clearanceOver-bending at I-tube inlet
24 Survival condition Cutting of product More critical for power cables and umbilicalsInstallation 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?