Dynamic Riser Connector Radial Engagement for Hoop Stress
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Solution Overview
Problem
Existing pipe connectors for smaller-diameter offshore pipelines face challenges in adapting to smaller diameters due to increased hoop stresses, which can exceed the yield strength of materials, and are difficult to disengage without using high-strength alloys that may be impractical for seawater environments or welding with common alloys.
Innovation Solution
The development of a high-strength, fatigue-resistant pipe connector system featuring frusto-conical, concentrically grooved or threaded mating surfaces with flat surfaces for sealing and preloading, along with contoured radial protrusions and a wedge-shaped seal ring to accommodate axial movement and control radial compliance, allowing for snap engagement and disengagement without overstressing the connector walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional threaded pin-and-box connector systems are used for smaller-diameter pipes, then connection strength is improved, but hoop stresses exceed the yield strength of materials during engagement and disengagement
Solution Approach 1:
The connector system transitions from static threaded engagement to dynamic radial expansion/contraction engagement. The box expands radially and the pin contracts radially during engagement, allowing the threads to snap into place dynamically rather than being forced statically, thereby reducing peak hoop stresses below yield strength thresholds
Solution Approach 2:
The invention changes the engagement parameters from axial threading to radial dimension changes. By controlling the radial expansion of the box and contraction of the pin through hydraulic pressure, the system achieves engagement at stress levels below material yield strength, resolving the contradiction between connection strength and stress limitations
2Strength
If higher-strength alloys are used to withstand increased hoop stresses, then connection strength is improved, but material compatibility with pipeline fluids and environmental conditions deteriorates
Solution Approach 1:
By changing the engagement mechanism from high-stress threaded forcing to controlled radial expansion below yield strength, the invention enables the use of common steel alloys that are compatible with pipeline fluids and seawater environments, eliminating the need for incompatible high-strength alloys
3Strength
If higher-strength alloys are used to withstand increased hoop stresses, then connection strength is improved, but ease of welding with common pipe alloys deteriorates
Solution Approach 1:
The radial expansion engagement mechanism reduces peak stresses to levels achievable with common steel alloys, which are easily weldable to standard pipe materials. This resolves the manufacturing difficulty associated with welding high-strength, low-ductility alloys to common pipe alloys
4Strength
If radial thread displacement is increased to achieve engagement in smaller-diameter connectors, then connection strength is improved, but the required displacement exceeds the yield strength of materials
Solution Approach 1:
The system uses dynamic radial expansion and contraction to achieve thread engagement through snap-action rather than gradual forced displacement. This dynamic engagement achieves strong connections in smaller-diameter connectors without requiring thread displacements that would exceed material yield strength
Solution Approach 2:
The snap-engagement mechanism utilizes elastic deformation and rapid settling similar to vibrational effects, allowing threads to lock into place through controlled dynamic motion rather than static forcing, reducing the total displacement required below yield thresholds
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 connector system provides a simpler, more versatile, and universally usable solution for smaller-diameter pipes, capable of withstanding high pressures and torsional loads, with a longer fatigue life and reduced likelihood of leaks, while being compatible with common steel alloys and practical for subsea environments.
Implementation Method 1
Axial movement of the pin into the tapered mating box results in the radial expansion of the box and radial contraction of the pin until the concentric thread patterns match and interlockingly snap into the connected position
Implementation Method 2
A wedge-shaped, resilient ring (e.g., elastically deformable under pressures and forces applied during connection or disconnection of the box and pin components) is configured to be disposed at (e.g., and at least partially aligned with) the ID of the connector to accommodate axial movement during connector make-up and effect a seal in the connector ID
Implementation Method 3
the pin and box of such connectors systems are typically engaged and disengaged by providing hydraulic fluid under high pressure (typically 5,000 to 10,000 psi, 34473.8 to 68947.6 kPa) in the threaded annulus between the pin and box, thereby expanding the box and contracting the pin in their respective threaded diameters
Data Source
Figure 1
Figure 2~3
Figure 4~9
AI summary
High-strength, fatigue-resistant pipe connectors suitable for use in offshore risers, tendons and pipelines, such as may be connected to floating production systems (FPSs) principally used in the production of oil and gas. The present connectors include tubular pin and box components with mating frusto-conical, concentrically-grooved mating surfaces which threadingly interlock, and non-threaded (e.g., flat) mating surfaces that seal and preload (e.g., preload at least a portion of each component in compression), via axial advancement of the pin component into the box component. In such connectors, axial movement of the pin into the mating box results the in radial expansion of the box and radial contraction of the pin until the concentric thread patterns match and interlockingly snap into the connected position.