Model Tests of a Riser Armour for Subsea Offshore Loading of Hydrocarbons: Part I. Response to Ice Impacts

An offshore loading system for hydrocarbons was designed for ice-infested waters. The flexible riser linking the tanker to a sub-sea bottom installation is protected in a steel armour made of conical elements. The riser is then protected against ice blocks that may travel under the tanker keel when breaking pressure ridges. A model of the armour was built and mounted under a moored tanker in a flume in the Harbour Laboratory at the Norwegian University of Science and Technology (NTNU), Trondheim. Impacts from big single ice floes were then simulated. A maximal horizontal full-scale deflection of 2.2 m was observed, horizontal forces at the extremities of the armour culminated at 370 kN. These tests indicate an effective way of protecting the riser. The considered design seems to be a safe solution to loading in the arctic offshore.