Riser Section Locking Ring for Offshore Drilling Tension Management
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Solution Overview
Problem
Deep-sea drilling risers face challenges with excessive weight and pressure losses due to water depth, requiring larger auxiliary pipes, which increases mass and cost, and existing connector systems are not removable for inspection and maintenance.
Innovation Solution
A riser section design featuring a locking ring with multiple rows of tenons and a sliding pivot connection between the main tube and auxiliary tube elements, allowing for adjustable clearance and distribution of tension forces, reducing the need for thick auxiliary lines and facilitating easy assembly and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the water depth increases, then the riser length increases, but the weight of the riser becomes very detrimental
Solution Approach 1:
The riser is divided into modular tubular elements that can be assembled in sections. Each element has connectors at both ends, allowing the riser to be built in discrete segments rather than as a single continuous structure, enabling manageable assembly and reducing overall weight burden.
Solution Approach 2:
The connector design includes a locking ring that can be rotated to engage or disengage tenons, providing dynamic assembly and disassembly capability. This allows the riser configuration to be adjusted based on operational needs, optimizing the weight-length relationship.
2Stress or pressure
If the maximum operating pressure is maintained, then the internal diameter of the auxiliary pipes must be larger, but this increases the mass and cost
Solution Approach 1:
The auxiliary pipes are pre-assembled with the main tube elements at the floating support before deployment. This preliminary assembly allows for optimized sizing of auxiliary pipes based on actual operational requirements rather than conservative over-design, reducing unnecessary mass.
Solution Approach 2:
The system allows adjustment of auxiliary pipe dimensions and configuration based on specific operational parameters. By changing the parameters of auxiliary pipes (diameter, wall thickness, material) according to actual pressure requirements rather than using fixed large dimensions, the mass is optimized while maintaining required pressure capabilities.
3Length of stationary object
If the water depth increases, then the column length increases, but the assembly time becomes more critical
Solution Approach 1:
The riser is segmented into standardized tubular elements with identical connector interfaces. This segmentation allows for pre-fabrication of modules and rapid assembly by simply connecting standardized sections, significantly reducing assembly time for deep-water applications.
Solution Approach 2:
The connector design with standardized tenons and locking rings serves multiple functions: mechanical connection, sealing, and alignment. This multi-functionality eliminates the need for separate alignment and sealing operations, streamlining the assembly process for longer columns.
4Strength
If the auxiliary lines are made thicker to resist tensile forces, then the mass and size of the floats increase, but this generates an increase in cost
Solution Approach 1:
The auxiliary lines are merged with the main tube structure through integral connection at the flanges. This combining allows the main tube and auxiliary lines to work together as a unified structure, distributing tensile forces across the entire assembly rather than requiring auxiliary lines to independently withstand full tensile loads.
Solution Approach 2:
The connector assembly combines different materials and structural elements (metal flanges, locking ring, tenons, auxiliary pipes) into a composite structure. This composite design optimizes the strength-to-weight ratio by placing materials where they are most effective, reducing the need for excessively thick auxiliary lines.
5Reliability
If the connectors are made non-removable to ensure structural integrity, then inspection and maintenance become difficult, but this reduces ease of repair
Solution Approach 1:
The connector incorporates a dynamic locking mechanism with a locking ring that can be rotated to engage or disengage tenons. This dynamic design maintains structural integrity when locked while allowing complete removal when needed for inspection or maintenance, providing the best of both requirements.
Solution Approach 2:
The locking ring acts as an intermediary component between the tenons and the connector body. It provides the locking function to ensure structural integrity while simultaneously serving as the interface for assembly and disassembly, enabling easy maintenance without compromising reliability.
Data Source
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AI summary
The invention relates to a section (4) of a riser, provided with an outer locking ring (11). The locking ring (11) cooperates with a male connector element (9) and a female connector element (8) by means of a series of lugs. The invention also relates to a riser consisting of a plurality of sections (4) and to the use of the riser for performing an offshore drilling operation.