Abstract

Reeling lay (R-lay) is a common method used for installing line pipes on the seabed. In R-lay, girth-welded line pipes are subjected to repeated plastic strain while on reel barges. This paper discusses the mechanical properties that change in R-lay usage and describes the performance prediction of pipes installed on the seabed. Using full-scale reeling simulation (FSR), changes in the pipe profiles and the mechanical properties were measured. Then, using small-scale reeling simulation (SSR), the impact toughness was evaluated after strain aging. These simulations demonstrate plastic anisotropy in R-lay pipes. The strain capacity in laying was predicted using the FE-model, with measured geometry and strength distribution. The impact toughness is acceptable for laying line pipes in subsea areas. Based on the R-lay simulations, the applicability of HF-ERW line pipes is also discussed.

Introduction

R-lay is an effective laying method for offshore pipeline. HF-ERW pipe with a good roundness and eccentricity is a strong candidate for line pipes used in R-lay (Denniel 2011, Tsuru 2013, Karjadi 2015). Comparing S-lay and J-lay, line pipe R-laid is characterized by the plastic strain repeatedly developed in reeling and unreeling. Before lying on the seabed, the bending and unbending on the spool change the mechanical properties and increase the geometric imperfection in the pipes. Previous studies have presented the impact toughness in seamless pipe and the collapse resistance in ERW pipe after the reeling simulation (Higuchi 2010, Shitamoto 2013, Tsuru 2015). However, there is no data on the mechanical properties and plastic anisotropy changes in reeling operation.

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