Development of methodologies for sliding wear measurement on liners and flexible riser pipes

Flexible riser pipes are extensively used in deep-water oil and gas exploration to transport these products from the seabed to the platform. These pipes may be severely worn out on the bend stiffener region due to the reciprocating sliding movement against the liners. This relative movement is caused by water currents, bad weather conditions and platform movements. This paper presents the development of methodologies to quantify the wear rate of flexible riser pipes and of liners using a coordinate measuring machine (CMM). Samples of six-inch flexible riser pipes and of liners tested in a large-scale tribometer were used to evaluate these methodologies. The expanded measurement uncertainty of the wear parameters was assessed according to the recommendations of the “Guide to the expression of uncertainty in measurement” (GUM-JCGM 100). Moreover, the contribution of the sample elastic deformation and of the thermal effects on the measurement uncertainty was considered. Among all the factors that affect the measurement uncertainty of the wear rate of the flexible riser pipe, the variability of the thickness along the wear track contributed most to the measurement uncertainty. This variability was caused by a rough inner surface in the riser polymeric layer. When measuring the liner wear rate, the elastic deformation of the polyurethane polymer had the highest contribution. The wear rate of the six-inch riser pipe and of the corresponding liner made it possible to estimate the lifetime of these components in the field.