Torsion in Flexible Pipes, Umbilicals and Cables Under Loadout to Installation Vessels

Abstract

Operations where a flexible pipe, umbilical or cable is loaded out from an on-shore spool to the hold of an installation vessel can cause a build-up of torsion. In unfavourable cases, the torsion has been known to cause spiralling or various forms of damage to the tensile armour. This paper presents a vocabulary for the description of torsion. It then gives a short review of design codes, enumerates known failure modes (some of which have not always been identified as torsion related), and discusses the mechanisms of torsion generation, with an emphasis on the effect of internal friction. It concludes with some ideas on torsion prevention.