PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.ii)Ø 800 mm PE8 SDR17.6Length= 500 mMax. depth = 200 mMax. pulling force = 40 kNWeighting, a a = 15 %v max = 1.0 m/sIf we derive a formula based on a simple energy balance where kinetic energy is transformed toelastic energy in the pipe, and only consider the axial direction, we get the expression :2 1σm2 dv2max = ⋅ ( ⋅ (1 − ))A.5-18)F E ⋅ ρ2Dv max = critical sinking speed (m/s)σ m = σa - σTσ m = stress (Mpa)σ a = design stress (5.0 Mpa)σ T = stress created by pulling force and weighting (≈ 2.5 Mpa)F = factor of safety / correction factorE = Modulus of Elasticity (800 Mpa)d = internal diameterD = external diameterρ = density of water (kg/m 3 )If we put in values and assume the pipe to be thin-walled, we get the formula :7.9v max = A.5-19)F ⋅ SDRIf we now compare this formula to the real projects i) and ii) we get the safety factors / correctionfactors :F i) = 3.4 F ii) = 1.9If we, for instance, use the mean value of the two factors we get the result (F = 2.65) :3.0v ctitical = A.5-20)SDRThis formula gives an indication of the maximum sinking speed during a controlled sinking(pulling force in the end) before the pipe is damaged.We will, however, not recommend to use these speeds without risk analysis.Table A.5.4 gives the critical sinking speeds :SDR-classCritical sinkingspeed (m/s)SDR-classCritical sinkingspeed (m/s)413327.626220.470.520.570.590.6417.61713.61190.720.730.810.901.00Table A.5.4 Critical sinking velocity for PE-pipesSide 75 av 84