Development and Qualification of End Fittings for Composite Riser Pipe

Abstract

Abstract Whilst much interest is often focussed on the composite pipe body it is often forgotten that a reliable end fitting is a prerequisite of a successful composite pipe application and further that the design challenge of the end fitting is more challenging than the pipe itself. The purpose of this paper is to present the end fitting arrangement for a composite pipe manufactured from carbon fibre and PEEK polymer. The paper describes the design approach and testing/qualification program employed for the end fitting to demonstrate reliable application in a critical and structurally demanding application such as for a deep water dynamic riser. The paper summarises historical design approaches and design alternatives and explains the reason for selecting the proposed arrangement. It presents the design process used to develop the design and to predict its structural response. It discusses manufacturing issues and describes the test program conducted to prove the end fitting performance. Industry focus is often on the pipe rather than the end fitting. However the latter often presents a more difficult design challenge. Without a reliable design solution and methodology composite pipe application cannot be considered. The development work presented in the current paper therefore presents an important step towards application of composite technology on demanding riser applications. An end fitting with reliable structural and sealing performance is a prerequisite for the successful application of composite pipe. Historically, this has proven to be a difficult challenge and end fitting performance limitations have been cited for the slow introduction of composite pipe technology. The current paper presents a new design approach to the problem, made possible by a unique manufacturing process and a better understanding of the composite metallic interface, which together allows the end fitting problems to be resolved. The paper describes fundamentals of the design approach, the development work conducted, manufacturing and qualification testing. The paper discusses the function specification, key design features, FEA approach and results, codes and standards, testing results under combined load conditions and fatigue testing results. Introduction Design, fabrication and installation of riser systems for floating production is a complex challenge. Constraints such as maximum payload capacity and design issues such as internal and external corrosion, fatigue capacity, thermal insulation, weldability and susceptibility to sour service conditions conspire to make riser design one of the most demanding challenges in the offshore industry today. The magnitude of this challenge has grown, perhaps non linearly, as water depths have continued to increase over the last 20 years. Also operating pressures and temperatures have increased, particularly in the last 10 years, with the focus on presalt and subsalt reservoirs.