Hinged Stab and Sliding Mechanism for Subsea Pipeline Terminal
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Solution Overview
Problem
Subsea pipelines experience buckling and drift due to thermal expansion, causing structural damage and operational challenges during hydrocarbon conveyance, especially in deep water environments where extreme pressure and temperature conditions exacerbate the issue.
Innovation Solution
A subsea system featuring a foundation with a receptacle and a hingedly mounted stab to secure the base frame, combined with a sliding mechanism along a track to accommodate longitudinal expansion, and a locking mechanism to prevent vertical movement, ensuring the pipeline end is securely anchored and able to adjust to thermal changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If both ends of the pipeline are secured to fixed locations, then the pipeline is stable during installation, but the pipeline buckles and drifts due to thermal expansion during operations
Solution Approach 1:
The pipeline end terminal incorporates a sliding mechanism that allows the pipeline to move dynamically along the sea floor in response to thermal expansion and contraction, rather than being rigidly fixed. This dynamic adjustment prevents buckling while maintaining stability during installation through the hinged base frame and stab mechanism.
Solution Approach 2:
The terminal assembly is divided into distinct functional segments: a hinged base frame for initial stabilization, a sliding mechanism for thermal expansion accommodation, and a locking mechanism for securing the pipeline end. This segmentation allows each component to address specific aspects of the stability-expansion contradiction.
2Force
If only one end of the pipeline is secured to the sea floor, then stress forces at the ends are reduced, but the unsecured end drifts over a wide range making workover operations difficult
Solution Approach 1:
The terminal provides conditional stability: the hinged base frame with stab mechanism secures the pipeline end horizontally during installation and workover operations, while the sliding mechanism allows longitudinal movement during thermal expansion. This dynamic securing approach reduces stress forces while maintaining operational accessibility.
3Length of moving object
If the pipeline is extended along the sea floor for deep operations, then the pipeline can reach distant wells, but the thermal expansion creates larger forces that exacerbate buckling
Solution Approach 1:
The sliding mechanism enables the pipeline to dynamically adjust its position along the sea floor, accommodating the increased thermal expansion forces that result from greater pipeline lengths in deep water operations. This prevents buckling while allowing the pipeline to extend over long distances.
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
The system effectively secures the pipeline end against horizontal and vertical movements, reducing structural stress and facilitating workover operations by allowing the pipeline to expand and contract without damaging the pipeline or associated equipment.
Implementation Method 1
A stab is hingedly mounted to the base frame. The stab stabs into the receptacle to secure the base frame to the subsea foundation.
Implementation Method 2
The base frame can pivot about the stab to engage the upper portion of the subsea foundation after the stab stabs into the receptacle.
Implementation Method 3
The flowline often expands and contracts due to the heat emitted from the flow of hot hydrocarbons passing through the flowline. The sliding mechanism is carried by the base frame and moves the track.
Implementation Method 4
The base frame can also have a locking mechanism that is selectively extendable into engagement with the foundation deck.
Data Source
AI summary
A subsea system for securing an end portion of a pipeline includes a subsea foundation. The foundation has a lower portion located below the sea floor and an upper portion extending above the sea floor. The subsea foundation has a receptacle formed in the upper portion. The system includes a base frame that lands on the subsea foundation. The base frame has a track formed therein. A stab is hingedly mounted to the base frame. The stab stabs into the receptacle to secure the base frame to the subsea foundation. A sliding mechanism is carried by the base frame and moves along the track. The sliding mechanism is connected to a segment of the pipeline extending along the sea floor. A terminal assembly for an end portion of a pipeline and a method for securing an end portion of a pipeline are also included herein.