Development of Internally Pressurized Composite/Metallic/Composite Hybrid Pipes

Abstract

The challenge to the pipeline industry is to meet the increased worldwide demand while reducing the cost. Currently, metallic and composite pipelines are the most cost-effective way of transporting water, oil, and gas. Limitations of metallic and composite pipelines are familiar. Corrosion reduces the load-carrying capacity of metallic pipelines, while matrix cracking/abrasion causes the failure of the composite pipelines. Both corrosion and abrasion cause significant losses and decrease the structural integrity of pipelines. This work proposes a corrosion-free hybrid pipe, which will improve the pipeline’s pressure capacity and eliminate internal and external corrosion. First, this research aimed to examine fiber type and fiber orientation’s effects on the interface bonding between steel and fiber-reinforced composites. To this end, fracture loads for modes I and II were experimentally determined for FRP/steel samples with different fiber types and orientations. Results showed that fiber orientations and fiber types have significantly affected the interface bonding between the steel and fiber reinforced composite. Second, a detailed investigation for the effect of the FRP overwrap system on the bending behavior of metallic pipes was presented, especially in the presence of heat-affected zone in the case of welded pipes. It was proved that the use of the proposed FRP overwrap system had eliminated the effect of the heat-affected zone in welded / steel pipes, and the maximum bending flexural load showed a noticeable increase. Third, the internal pressure capacity of hybrid composite/steel/composite pipes was tested according to ASTM D1599 standard. The testing results showed significant improvement in the internal pressure capacity compared to the conventional steel pipes. Fourth, a detailed evaluation of fiber type’s effect on the electrochemical corrosion aspects in different highly corrosive solutions, 0.5 M NaCl, 0.5 M HCl, and 0.5 M H2SO4, was presented. Finally, the corrosion aspects of composite overwrapped steel pipes were evaluated. The FRP/steel pipes were immersed in a glass container containing the corrosive solutions and monitored for six months and one year. The corrosion condition was qualitatively analyzed using SEM, EDX and XRD analysis. Results showed an excellent corrosion resistance for the FRP/steel pipes compared to the conventional carbon steel pipes.