Analysis of Subsea Umbilical Installation Under Radial Compression and Axial Tensile Loading

Abstract Umbilicals are complex structures composed of electrical cables and hoses used to transmit power, fluids, and data between floating production units and subsea systems. Recent developments in oil and gas exploration and production in ultra-deep waters have heightened the need for design analysis to install umbilical cables. During installation, these umbilicals are under radial compression forces (crushing) caused by the tensioner pads of the PLSV ship, which control the installation speed, as well as tensile forces resulting from the weight of the already deployed umbilical. Most studies in this area have focused only on analyzing the concept and design of these umbilicals. Failures caused by the passage of the umbilical through the ship’s tensioner pads, the maximum number of permissible installation/removal operations, and the functional failure conditions of the tested systems were not satisfactorily evaluated. This paper analyzes the results obtained from experimental tests on STU umbilicals to evaluate axial tensile and radial compression forces, displacement, under conditions similar to those of the installation. Experimental tests that simulate the application of the loads by the tensioner pads and the axial tensile forces were carried out using a mechanical apparatus. The tests conducted using the mechanical apparatus were used to calibrate a 2D nonlinear model developed in the FE program. This model was developed to determine the physical parameters that cannot be measured experimentally given the complexity of these structures. Among the results obtained are the residual ovalizations of the sections after the application of combined installation loads, as long as the validation of the radial strength previously assumed to model such structures. It is concluded that the effect of installation loads can be more severe than predicted.