Flexible Riser
Wednesday, February 17, 2016
Risers transport products from subsea wells, via flowlines, to topside facilities (import riser) or topside facilities, via pipelines, to onshore facilities (export riser). There are fixed static risers, free standing dynamic risers, or combination of both (called hybrid riser). Risers are classified as follows due to material type and its application:
- Rigid pipe – Fixed (clamped) riser, J-tube riser, Fixed (clamped) catenary riser, Top tension riser (TTR), Steel catenary riser (SCR)
- Rigid + Flexible – Hybrid riser
- Flexible pipe – Simple catenary riser, Lazy wave riser (with distributed buoys), Pliant wave riser (chain anchored lazy wave), Steep wave riser (vertical connection at seabed), Lazy S riser (with an arch buoyancy structure), Pliant S riser (chain anchored lazy S), Steep S riser (vertical connection at seabed)
The design of the riser system is
an iterative process. To begin with, a riser configuration must be assumed and
analyzed. The selected configuration is then subjected to a combination of
environmental loadings and vessel motions with the riser empty and full to
determine the global dynamic response. As this is a tension dominated
structure, it is imperative under all circumstances that the riser remain in
tension. Compression may cause bird-caging and will adversely affect the
integrity of the riser and reduce service life.
Finally, the detail static and
dynamic analyses of local areas are performed to enable the design of various
components such as bend stiffeners, bend restrictors, buoyancy modules, subsea
buoyancy arches, and end connectors/flanges.
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Source:
Lee, Jaeyoung. Introduction to
Offshore Pipelines and Risers. 2007.
Guo, Boyun, Shanhong Song, Jacob
Chacko, Ali Ghalambor. USA. 2005.
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