PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.the factory, towing it to the site and submerging it into the trench at the river bottom.After submersion the trench was filled with gravel.Fig. 0.1.2.1 Sewerage river crossing.0.1.3 Outfall pipelineTreated sewage water will normally be conveyed into the recipient discharge area at a certain depthand distance from coast. A depth water outlet will provide excellent dilution of the waste- water.Outlet deep will vary in the range 10-60 m dependent of the recipient’s self-purification capacity.The recipient can be river, lake, fiord or sea.The outfall usually starts from an outfall chamber at the waterfront to which the wastewater is lead bygravity or pumping.Use of pumping directly on the outfall pipeline is rather rare and not recommended. If pumping isnecessary, the best solution is to pump the sewage water into the outfall chamber and conduct it withgravity into the recipient.The main task for the outfall chamber is to prevent air from entering the pipeline.Air can cause floatation of the pipe due to buoyancy.It is also necessary to take into account the variations in low tide and high tide when designingan outfall chamber.Special problems to take into consideration regarding outfall pipelines are :− Air entrainment in pipe flow− Bio fouling− Current and wave induced forces− Sediment transportFig. 0.1.3.1 represent an industrial outfall. The figure shows the outfall system to the sea froma steel plant in northern Norway. The main components in the outfall system are :−430 m pre-stressed concrete pipes with a diameter of 1.800 mm buried in the seabed at a waterdepth of 4 m. The sea end of the concrete pipeline is connected to concrete anchor block. Theland end is connected to an outfall chamber.Side 6 av 84