PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

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Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.B. InstallationThis chapter gives some practical information to the contractor regarding installation of subwaterpipelines. We also refer to chapter 0.2.B.1 Jointing of PE pipesVarious jointing methods have been developed since polyethylene pipes first came on the market inthe early 1960s.To day there are many jointing methods suitable for all sizes of PE pipes :- butt fusion welding- electro-fusion fittings- stub end with steel backing ring- mechanical couplersFusion welded joints are by far the most common.Butt fusion can be used on all sizes of PE pipes, but is mainly used on pipes from 110 mm to1600 mm in diameter.Electro-fusion couplers are now available in sizes up to 500 mm and in the future even biggerdiameters will be available.A stub end with backing ring is mainly used for jointing longer sections of pipes together, forconnections to valves or manholes or to pipes made of other materials.Butt fusion welding of pipe strings combined with stub end / backing rings are usual for the largerPE pipes for installation on land or in marine environments. Butt fusion and electro fusion fittings aremainly used for the smaller pipe sizes.Mechanical fittings for all sizes of PE pipes are now available in various metal and plastic designs.They are preferable under conditions of :- extreme short-term bending stress as during submerging and laying- difficult or impossible welding conditions- under water jointing of repair of pipes in generalIn case of using long prefabricated sections towed by boat to the site, it can be favourable to jointhem together with support sleeves and stub ends as shown in fig. B.1.1.Support sleeves are also used in connecting PE pipes to grouted flanges in manholes. They may bedelivered to fit all sizes of pipes and can be adjusted to suit customer preferences for length andcorrosion protection.Fig. B.1.1 Support sleeveSide 76 av 84
Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.B.2 Butt fusion of PE pipesThe standard butt fusion cycle, according to DS-INF-70/INSTA 2072, is shown in fig. B.2.1.Fig. B.2.1 Butt fusion cycle.P 1 = heating pressure, high (Mpa)P 2 = heating pressure, low (Mpa)P 3 * = welding pressure (Mpa)P 4 = cooling pressure (Mpa) ≈ P 3t 1 = heating time (s) with high pressuret 2 = heating time (s) with low pressure∆t = change-over time (s)t 3,1 = pressure build-up time (s)t 3,2 = cooling time (s), relative to a cooling pressure P 3*) The welding pressure may differ from that stipulated in DS-INF-70/INSTA 2072, as it dependson the welding criteria stated in the standardIn next chapter there is given some guidelines regarding the welding parameters.B.2.1Welding parametersThe welding parameters listed below are average of guideline values. Wall thickness (e) anddiameter (d e ) are stated in millimetres.1. Welding Temperature – TThe welding temperature, T, shall be in the range of T = 210ºC ± 10ºC and shall be measuredcontinuously and verified for each weld using a thermo stick.2. Heating-up Pressure (high) – P1The heating-up pressure shall be P = 0.18 N/mm 2 ± 0.01 N/mm 23. Heating-up Time - t 1This is the bead formation time in seconds. It shall be recorded. See item 4.Side 77 av 84
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PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

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