Subsea Stab Frame Pivot Mechanism for Large Bore Connection
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Solution Overview
Problem
Existing subsea connection systems are ineffective for large bore applications greater than two inches due to difficulty in installation and inability to withstand high pressures, particularly when connecting high-volume, high-pressure flowlines to subsea structures like relief well injection spools.
Innovation Solution
A subsea connection system featuring a frame with a pivotable hook portion and hydraulic actuator that supports and aligns a large diameter stab with a subsea structure's port, allowing for easy installation and secure connection without requiring a remotely-operated vehicle (ROV) to support the weight, and enabling quick deployment and removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing subsea connection systems are used for large bore applications, then the connection can be made, but the system cannot withstand high pressures and installation is extremely difficult
Solution Approach 1:
The frame is designed to be pivotable about the tool hanger, allowing dynamic adjustment from a vertical transport position to a horizontal working position. This dynamic capability enables the system to adapt to different operational phases, making installation feasible while maintaining structural integrity for high-pressure applications
Solution Approach 2:
The tool hanger serves as an intermediary component mounted on the subsea structure, providing a pivot point that facilitates the connection process. The actuator acts as an intermediary mechanism to move the stab between retracted and extended positions, enabling precise control during connection while the system withstands high pressures
2Manufacturing precision
If a remotely-operated vehicle (ROV) supports the weight of the stab, then alignment can be achieved, but the system becomes too complex for large bore applications
Solution Approach 1:
The frame pivots about a horizontal axis perpendicular to the stabbing direction, introducing a rotational degree of freedom that enables alignment in a different dimensional plane. This allows the heavy large-bore stab to be aligned without requiring complex ROV manipulation, as the pivot mechanism handles orientation while the ROV only needs to position the assembly vertically
Solution Approach 2:
The frame's pivotability and the actuator's movement capability enable the system to self-align and self-position the stab during connection. The hydraulic actuator automatically moves the stab between retracted and extended positions based on pressure differentials, reducing the need for complex external ROV intervention
3Productivity
If quick deployment and removal is enabled, then productivity increases, but the connection stability under high pressure may be compromised
Solution Approach 1:
The frame is pre-configured with the stab in a retracted position during transport, allowing quick deployment to the work site. The pivot mechanism is pre-positioned to enable rapid transition from transport to working configuration, and the actuator is pre-filled with hydraulic fluid to enable immediate extension when needed, all while maintaining connection stability under pressure
Solution Approach 2:
The system transitions dynamically between distinct operational states: transport mode with frame vertical and stab retracted, and working mode with frame horizontal and stab extended. This dynamic state management enables quick deployment and removal while ensuring stable, pressure-resistant connection during the actual working phase through the actuator's locking mechanism
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
Enables efficient and secure connection of large diameter flowlines to subsea structures, facilitating the delivery of high-pressure fluids and allowing for easy removal and redeployment, particularly in emergency situations like well blowouts.
Implementation Method 1
an actuator positioned on the frame and cooperative with the stab. The actuator is adapted to move the stab between a retracted position and an extended position
Data Source
AI summary
A subsea connection system has a subsea structure with a flow channel therein and a port at one end of the flow channel, a stab having a flowline connected thereto, and a frame affixed to the stab. The stab is adapted to engage the port of the subsea structure so as to allow a fluid to flow from the flowline into the flow channel. The frame has a hook portion that is engageable with a tool hanger of the subsea structure so as to support the stab in alignment with the port. The frame is pivotable about the tool hanger so as to move the stab toward the port. An actuator is cooperative with the stab so as to move the stab between a retracted position and an extended position.