Surface laid subsea pipelines under high temperature and pressure (HT/HP) induces compressive effective axial force which had over the years been the driving factor that initiates lateral buckling of subsea pipeline. This could lead to failure of the pipeline if lateral buckling and the resultant walking phenomenon at the buckle crown are not properly controlled or mitigated.
Over the years, flowline engineers have addressed issues of lateral buckling of exposed subsea pipelines by adopting approach that allows pipeline to buckle provided it is demonstrated that the high thermal axial forces and consequent deformations are acceptable.
This paper will present a study of the lateral buckling capacity of surface laid flowline under varying lay amplitudes and a uniform curvature. It will address the utilization of the buckling capacity with regard to uncertainties in lateral soil friction, shape and/or dimensions of initial imperfection affecting pipe-lay curvature at seabed with respect to maximizing the feed-in into a buckle.
Snake-lay configuration will be considered as the expansions control/sharing mechanism in this paper. The post buckling force will be shown as one of the defining parameter for determining the acceptable lay amplitude that will maximise the pipeline capacity during lateral buckling designs. The paper will further differentiate with finite element analyses (FEA) the acceptability of axial feed-in in design for load control condition (moment-based) and displacement control condition (strain-based) with respect to DNV-RP-F110 and the need for ECA strain limit for plastically deformed pipeline.