Increased interest in deepwater and ultra-deepwater field development is leading the industry to revisit the standard design and testing methods of production risers. The main challenges involved in a deepwater project are the riser sizing, management of external pressure at maximum water depth with acceptable weight to keep low stress at riser-vessel interface, the riser/vessel dynamic interaction and riser installation. The most critical areas on the riser system are the top section, where most of the damage occurs, and the touchdown zone. While the second area can be addressed by effective riser design, the connection to the production facility is always required and it must be sufficiently strong to provide an appropriate fluid containment. A connector failure can lead to highly flammable fluid leakage, putting in danger the entire production vessel and the surrounding environment. Technological advancements are leading to new equipment layouts with more efficient materials selection. The top section and connector can be subjected to different kinds of loads and environment induced degradation. Applying the actual standards is sometimes difficult due to the fact that they generally are too conservative. With the objective of closing this gap, this paper provides an overview of the issues regarding different types of connectors in different working environments. The criteria for achieving an optimum connection selection depends on the type of riser utilized, riser configuration, metocean conditions, support vessel type, properties of fluid/chemicals transported inside the riser, life expectancy, maintenance and accessibility. Three main kinds of connection seals were analyzed, namely pure metallurgical (i.e. welding), pure mechanical (i.e. flange, threaded connections) and a combination thereof for line-end interface (i.e. metal-to-composite). All of the seals must provide retention of internal fluids and exclusion of external fluids and impurities. In an offshore environment, both of these characteristics must be achieved through the use of at least one metal-to-metal contact between mating interfaces and one static seal (i.e. metal rings).
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