Subsea Riser End Fitting With Pivot Joint for Vertical Connection
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Solution Overview
Problem
The subsea oil and gas industry faces challenges in installing and connecting subsea risers with a substantially vertical bottom orientation to subsea equipment, particularly in dynamic environments with high sea states and strong currents, where conventional rigid steel risers experience fatigue and flexible pipes are expensive and have limited flow capacity.
Innovation Solution
An end fitting with a pivot joint assembly and counterweight system allows for vertical installation of subsea risers, enabling engagement with a subsea foundation and pivotability to accommodate dynamic movements, eliminating the need for jumper pipes and simplifying alignment with subsea flowlines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional rigid steel risers are used in dynamic environments, then structural strength is maintained, but fatigue and rupture occur due to repetitive motion
Solution Approach 1:
The riser system incorporates a dynamic joint assembly that allows relative motion between the riser and subsea equipment, transforming the rigid static connection into a dynamic adaptive connection. This enables the system to accommodate repetitive motions from vessel heave, pitch, roll, and seabed walking without generating fatigue stresses in the riser pipe.
Solution Approach 2:
The system changes the operational parameters by allowing angular displacement and positional adjustment at the subsea end. The dynamic joint assembly permits the riser to change its orientation and position dynamically, adapting to environmental conditions while maintaining structural integrity and avoiding fatigue failure.
2Ease of manufacture
If rigid pipes are used for subsea risers, then ease of installation is achieved, but adaptability to dynamic environments deteriorates
Solution Approach 1:
The dynamic joint assembly introduces dynamic capabilities to an otherwise rigid pipe system. It allows the riser to adapt its configuration in real-time to accommodate vessel motions and seabed movements, providing the necessary versatility while maintaining the installation simplicity of rigid pipes.
Solution Approach 2:
The riser system is segmented into a rigid pipe portion and a dynamic joint assembly portion. This segmentation allows the rigid pipe to maintain its installation advantages while the dynamic joint assembly provides the necessary adaptability to dynamic environmental conditions.
3Adaptability or versatility
If jumper pipes are used to connect vertical risers to horizontal flowlines, then connection flexibility is improved, but device complexity and installation cost increase
Solution Approach 1:
The dynamic joint assembly performs multiple functions: it provides the connection flexibility previously requiring jumper pipes, accommodates dynamic vessel and seabed motions, and enables direct vertical connection to subsea equipment. This multi-functionality eliminates the need for separate jumper pipes and reduces overall system complexity.
Solution Approach 2:
The invention merges the functions of the vertical riser connection and the flexible adaptation mechanism into a single integrated dynamic joint assembly. This consolidation eliminates the need for separate jumper pipes and simplifies the overall connection system while maintaining all necessary flexibility and adaptability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates cost-effective and reliable installation of subsea risers without the necessity of jumper pipes, reducing installation costs and enhancing the ability to connect risers under tension, while accommodating dynamic seabed conditions.
Implementation Method 1
counterbalancing the weight of a connector hub that is offset laterally from a flow axis extending substantially vertically through the engagement head and the weight of a connector pipe that extends from the flow axis to the connector hub
Implementation Method 2
mounting an end fitting at the bottom end of a riser pipe, that end fitting being able to rotate at least partially with regard to the riser pipe
Data Source
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AI summary
An end fitting for a subsea riser comprises an engagement head that is arranged to be engaged with a subsea foundation in a substantially vertically-downward longitudinal direction. A structure of the end fitting surrounds a longitudinally-extending flow axis. The structure is arranged to bear a tensile load on a load path that extends longitudinally from the engagement head in parallel to the flow axis. The structure includes a pivot joint assembly having a first part that is attached to or integral with the engagement head and a second part that is pivotable relative to the first part about a centre of rotation that is substantially aligned with the flow axis. The structure may be fixed to the engagement head or removably attached to the engagement head. The engagement head supports an upwardly-facing connector hub that is offset laterally from the flow axis. A connector pipe in fluid communication with the connector hub extends from the flow axis to the connector hub. A counterweight is opposed to the connector hub and the connector pipe about the flow axis.