PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.A. Hydraulic and technical designA.1 Technical data for design of PE-pipelinesTo carry out calculations we need figures for mechanical properties.The essential mechanical properties are described in terms of :E O = modulus of elasticity at zero loading time and low load (Mpa)E C = creep modulus, time > 0, stress σ > 0 and constant (Mpa)E R = relaxation modulus, time > 0, strain ε > 0 and constant (Mpa)σ O = burst strength at time zero (Mpa)σ C = creep strength at time > 0 (Mpa) (also called burst stress)ν =εlPoisson’s ratio =εrε l = strain in the axial directionε r = strain in the ring directionα = thermal expansion (º C -1 )For practical purposes the relaxation modulus (E R ) and the creep modulus (E C ) are assumed to beequal.E R = E C = E (E-modulus) as being function of load and loading timeThe mechanical properties for a PE-pipe are also dependent on the temperature. Normally theproperties are given at 20ºC or 23ºC .Fig. A.1.1 and A.1.2 show examples of how the E-modulus and the creep strength (burst stress)vary as a function of time and stress. For the creep strength the influence of the temperature is alsoindicated.The curves are taken from the Borealis book “Plastics Pipes for Water Supply and SewageDisposal” written by Lars-Eric Janson [1].= EFig. A.1.1 The relationship between creep modulus E and tensile stress with time as parameter forHDPE Type bars HE2467 (full lines) and HDPE Type 2 bars HE2467-BL (dotted lines) at 23ºC[1].Side 15 av 84