Sandwich Pipe: Reel-Lay Installation Effects

Comprising an annular layer with adequate thermal insulation and structural resistance material enclosed by two concentric steel pipes, sandwich pipes could be an alternative for flowlines in ultra-deepwater for the pre-salt reservoirs in offshore Brazil. In this work, a numerical and experimental study was performed to investigate the collapse behavior of sandwich pipes considering the reel-lay installation method. Experimental models were manufactured using two different geometries of stainless steel pipes and strain hardening cementitious composites with PVA fiber (SHCC) in annular layer. One set of specimens was tested using a reel-lay apparatus and another set was kept intact. A hyperbaric chamber was then used to test both sets of specimens to collapse. The collapse resistance of the proposed sandwich structure was investigated, and the detrimental effect of the reeling strains to the collapse resistance was assessed. The numerical models simulated reeling and straightening loads during reel-lay installation and then the collapse under external pressure. The results were compared with experimental measurements and shown good agreement.