PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

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Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.F 1Fig. B.3.5 Installation of a transit pipeline in principalFig. B.3.6 Installation of an intake or an outfall pipeline in principal.Pipeline systems are sunk in the direction from shore to the outer end, or other side of water.Normally the whole pipe is sunk in one operation. If the ambient conditions are adverse and varyfrom calm to rough sea, the pipe could be installed in sections, step-by-step. For practical reasons itcan also be convenient to install the pipe in sections.After one section is sunk, its sealed flange end rests on the sea bed. In a period with calm weather,the pipe is filled with air to lift its end to the surface, and the sinking proceeds, as soon as the nextsection in connected to the flange. During connection there must be applied a pulling force to avoidbuckling.There are also other methods to connect pipe sections in a step-by-step sinking. Dependent on thecontractor’s resources over and below sea-level, the connection can take place at seabed, semideepor in surface position.Short pipe pieces may be needed for connection between section ends on seabed dependent on thesinking method. Divers install those pieces after the sinking has taken place and the lengths arebased on exact surveying.During the sinking of pipe, water can be filled in one of the following ways :1. Blind flange with a valve located onshore, and water deliveredby a pump or from a water main.2. Blind flange with a valve located offshore, at a depth of 2 to 5 meters,with water filled directly by opening the valve3. Blind flange with valve in the inlet/outlet chamber,pipe connected to separate flange in chamber wall.Side 82 av 84
Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.The sinking speed, v, should be regulated and should not be greater than thecalculated v max (ref. A.5.3).In the outmost end there must be a valve arrangement for air release and pressure control and acompressor for air filling.The pulling force, F1, and the internal air pressure should be applied according to the calculations inchapter A.5.1 and A.5.2.The sinking speed shall be checked and recorded during sinking. If the speed is too high the internalpressure must be adjusted. The pulling force can be constant or adjusted to the water depth.Before sinking, ensure that :- all bolts are re-tightened to their final torque. This applies to bolts for the concrete weights andthe bolts for flange connections.- all concrete weights are at their correct locations/positions ; verify by measurement- all ancillary devices needed are on hand, including :- air pressure gauge, increments of 0.01 bar- water valves of suitable diameter- blind flanges fitted with air valves, 1" to 2" (in/out)- water valve (in/out)- air compressor of sufficient capacity and pressure- eventually water pump of sufficient capacity and pressureA tug boat or other vessel should be available to supply the necessary pulling force.Its engine power at full speed must be known accurately, to within 10 %.Small tug boats or other vessels may be used to provide transverse control of the floating pipeas it is positioned along the route.Experience shows that sinking of a PE pipeline is normally "a piece of cake" if the planning is good,the resources sufficient and weather conditions taken into consideration.Side 83 av 84
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PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

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