Riser Joint Connection System for Subsea Fatigue Resistance
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Solution Overview
Problem
Riser joint connections in subsea riser strings are vulnerable to harsh environmental conditions, including higher tension, bending, and dynamic fatigue loads, leading to weakness in strength and fatigue resistance.
Innovation Solution
The implementation of a riser joint connection system comprising a central coupler, reaction collars, collar stoppers, collar caps, and C-rings, which form a tight sealing and load-bearing surface through sloped and threaded configurations, allowing for increased strength and sealing capabilities under high pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional couplings are used in riser joints, then the structure is simple and easy to manufacture, but the strength and fatigue resistance are insufficient under harsh environmental conditions
Solution Approach 1:
The connection system is divided into multiple functional components: central coupler, reaction collars, collar stoppers, collar caps, and C-rings. Each component performs a specific function - the central coupler provides the primary connection interface, reaction collars distribute loads, collar stoppers prevent over-traversal, collar caps seal the connection, and C-rings provide additional mechanical interlocking. This segmentation allows each part to be optimized for its specific function while collectively achieving high strength and fatigue resistance.
Solution Approach 2:
The components are nested within each other to form a compact, integrated connection assembly. The C-rings are positioned within grooves of the reaction collars, the collar stoppers are mounted on the outer surface of riser joints, and the collar caps enclose the entire assembly. This nesting approach maximizes space utilization and creates a unified structural system that maintains simplicity despite the multiple components.
2Reliability
If the riser joint connection is designed to withstand higher tension, bending, and dynamic fatigue loads, then the strength improves, but the manufacturing complexity and assembly difficulty increase
Solution Approach 1:
The collar stoppers are pre-mounted onto the outer surface of the riser joints through threaded sections before the main assembly process. The C-rings are pre-positioned within the grooves of the reaction collars. These preliminary actions ensure that the load-bearing components are correctly positioned before the final tightening operation, simplifying the overall assembly process while ensuring reliable load distribution under harsh conditions.
Solution Approach 2:
The reaction collars act as intermediary components between the central coupler and the riser joints. They distribute the loads from the central coupler across multiple contact points on the riser joints, reducing stress concentrations. The collar caps serve as intermediaries that seal the connection and protect the internal components while allowing for torque application during assembly.
3Stress or pressure
If a tight sealing and load-bearing surface is created through sloped and threaded configurations, then the sealing capability and pressure rating improve, but the manufacturing precision requirements increase
Solution Approach 1:
The central coupler features sloped surfaces that create a conical or tapered seating interface with the riser joints. This curved geometry provides self-aligning characteristics during assembly, where the sloped surfaces guide the components into proper alignment as they are brought together. The threaded sections of the reaction collars and collar stoppers also follow helical curvature, which naturally distributes loads and maintains sealing pressure across the interface.
Solution Approach 2:
The threaded sections of the reaction collars and collar stoppers utilize standardized thread parameters (pitch, diameter, thread angle) that are well-established in manufacturing. By changing from a complex multi-dimensional alignment problem to a standardized threaded connection problem, the manufacturing precision requirements are reduced to conventional tolerances for threaded fasteners, which are easier to achieve and control.
Data Source
AI summary
Apparatus and methods related to riser joint connection are described. For example, some embodiments may contain a central coupler, a plurality of reaction collars, collar stoppers, collar caps, and C-rings, for connecting riser joints.