Permeability of methane, carbon dioxide and water in plasticized polyvinylidene fluoride (PVDF) and plasticized polyamid 11 (PA11) has been measured for a number of temperatures and pressures in a small scale test apparatus and permeability coefficients have been calculated. The results have been used to predict if the annulus of flexible pipes will be water wet. For verification of the small scale test, a large scale test has also been carried out in a 50 mm flexible pipe. Both test methods show that the annulus of flexible pipes will be water wet when carrying gas and water. This implies that the conditions in the annulus will be corrosive when pipes are carrying gas which contains carbon dioxide or
hydrogen sulphide. The corrosive conditions and corrosion fatigue must be taken into account when the fatigue life of flexible risers is calculated.
Keywords: permeation, methane, water, PVDF, PA11, flexible pipe, corrosion fatigue