PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

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Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.0.0 IntroductionDescription of different types of submarine applications for polyethylene pipes.Submarine PE-pipes have been used for transport of drinking water and sewage water since 1960.The pipes were then produced in length of 12 m, welded together by butt fusion, weighted byconcrete loads and sunk to the sea bottom by entering water at one end and releasing air at theother.The method is nearly the same today. However there is more emphasis on design and calculationsto secure a safe installation and avoid damages.Another innovation is use of long length (up to 500 m) pipes continuously extruded at the factory,towed by boat to the site and jointed by flange connections.This solution has been used successfully in overseas projects.Since 1960 there has also been a significant improvement in the development of raw materials andmethods of production.Therefore PE-pipes are today the most common pipe material in submarine applications.The combination of flexibility and strength makes it superior to other materials.In Norway, for instance, more than 95% of submarine pipelines are PE-pipes. The diameters varywithin the range Ø 50 mm - Ø 1600 mm, and the water depth can in special cases reach 250 m.Damages happen very rarely.This is due to :− Excellent materials− Proper design− Experienced contractors− Well educated supervisorsThe consecutive technical catalogue deals with the design subject.Here you will find theory and formulas that will enable you to calculate and solve the most commonproblems occurring in submarine pipeline projects.However, as an introduction, we first will mention the different types of submarine installations andbriefly describe a typical project example regarding the sinking of a pipeline.0.1 Different types of submarine pipelinesIf we follow the natural transport direction for consumer water, we can divide the installation into3 categories :− Intake pipeline− Transit pipeline− Outfall pipeline0.1.1 Intake pipelineIntake pipelines serve both civil and industrial applications.The sources can be rivers, lakes and fiords. The intake depths vary from 2 m to 250 m.The water is normally transported in the pipeline by gravity to an intake chamber.In some cases, the intake pipeline is connected directly to the pump in a pumping station.An intake pipeline is always exposed to negative pressure.Side 4 av 84
Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.Special problems to be aware of :− Under-pressure− Fouling− Air release− Current− WavesThe intake end of the pipeline is normally supplied with a screen.Fig. 0.1.1.1 shows an example from a river water intake. The figure shows a new water intakein Glomma river. The 1200 mm diameter pipeline in 3 km long. The pipe material is PE PN80SDR17.The hydraulic capacity is 1.5 m 3 /sec. The whole pipeline lies in a ditch 2-3 m deep for protectionagainst current, erosion, ice and floating timber. PE-pipes were chosen because of their flexibility,strength and ease of installation.Fig. 0.1.1.1 River water intake0.1.2 Transit pipelineIn many cases it can be suitable to cross lakes and fiords by subwater pipelines instead of usinga longer route along the waterside.In other situations it is necessary to cross rivers and seas to supply cities and islands with water,or to remove wastewater.The water can be transported by gravity or by pumping. During operation there is always anoverpressure in the pipe except in case of pressure surge.It is normal to install a manhole/shaft on each waterside to establish an interface between the underwater pipeline. The equipment in the shafts depends on the service level. It is normal to install shutoffvalves.Special problems to be aware of for transit pipelines are:− Pressure− Air transport− Current− Waves− Fishing equipment− AnchoringFig. 0.1.2.1 indicate a river crossing. The figure shows a profile of a PE-pipeline, a seweragecrossing of the Glomma, the longest river in Norway. The diameter of the pipeline is 600 mm and itswall thickness is 55 mm (PN10). The line length is 450 m. A five-metre deep pipeline-trench at theriver bottom was required to avoid damages to the pipeline from boat anchors. A PE-pipe waschosen because of its flexibility, which permitted producing the whole length in one piece atSide 5 av 84
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