Flexible pipes consist of an extruded plastic pipe reinforced by layers of high strength steel wires, and an outer plastic sheath to protect the wires from the external environment. Flexible risers provide the linkage between subsea systems and floating production vessels, and as such, are subject to dynamic loading with possible fatigue damage to the reinforcement wires. The wires may also be exposed to corrosive species (typically water, CO₂, H₂S) which diffuse through the plastic pipe from the inside, or to seawater in the case of damage to the outer sheath; the corrosive species may reduce the fatigue life of the wires.

The limited years of operational field experience for flexible risers increases the importance of endurance testing and prediction of service life for major deepwater developments. Prediction of the service life of dynamically loaded flexible risers therefore requires corrosion fatigue data for the reinforcement wires in realistic environmental conditions. To allow corrosion processes to occur, the frequency of cycling must be limited and each test can therefore be several weeks long.

Based on our expertise in sour service and corrosion testing, CAPCIS has developed facilities for corrosion-fatigue testing in both sweet and sour (H₂S) environments. We have fatigue test machines in our sour service and high pressure laboratories. Special equipment has been constructed for maintaining environmental conditions over long test periods and for monitoring of test conditions. Corrosion fatigue data from these test programmes has been used by our clients in predicting the service life of flexible risers.