PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.Fig. A.5.3 indicates that a speed 0.3 m/s can be applied for pipe diameters ≥ 1200 mm without risksfor oscillations.For Ø 1600 mm the maximum sinking speed with respect to oscillations is 0.6 m/s for SDR26.For practical purposes the sinking speed will be in the range 0.1 – 0.6 m/s for a controlledsubmerging.Example 4Assume a Ø 1200 mm PE80 SDR26 to be sunk to 50 m depth.The longitudinal section of the bottom is given by table A.5.1 below :L (m) H (m) L (m) H (m)0100200300515203040050060070035404550Table A.5.1 Longitudinal sectionThe intention is to sink the pipe by a constant velocity of v = 0.3 m/s.The loading is equal to an air filling rate, a a = 30 %.Assume the inlet opening for water during sinking to be 1 / 4 of the pipes internal diameter.Calculate the balance pressure inside the pipe and the sinking pressure.Find the maximum speed regarding buckling.Solution :Formula A.5-1) is used to calculate the balance overpressure :p b = a a ⋅ H a a = 0.3This gives :L (m) H (m) ρ b (mwc) L (m) H (m) ρ b (mwc)010020030051520301.54.56.09.04005006007003540455010.512.013.515.0Table A.5.2 Balance pressureFormula A.5-13) must be used to estimate p i . We can rewrite this formula :2v (f ⋅ L + k s ⋅ D)ρ i = a a ⋅ H -2 ⋅ g ⋅ DA.5-16)Input values :D = 1107.6 mmf = 0.02k s = 0.5 ⋅ (4) 2 = 8g = 9.81 m/s 2v = 0.3 m/sThe result is given in table A.5.3 :L (m) H (m) p b (mwc) p i (mwc) a i (%)01002003004005006007005152030354045501.54.56.09.010.512.013.515.01.464.465.958.9410.4311.9213.4214.9129.229.829.829.829.829.829.829.8Table A.5.3Internal sinking pressure.Side 73 av 84