Marine Riser Weak-Point Joint for Controlled Severing
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Solution Overview
Problem
Existing joint assemblies for marine risers lack a simple design with few parts that can create a weak point allowing severing at a predetermined longitudinal tension rating without reducing the pressure containment rating, often requiring complex designs and added seals.
Innovation Solution
A joint assembly comprising an upper, middle, and lower body with a machined groove or perforations in the middle body, and a means for restoring pressure capacity that surrounds and contacts the perimeter, such as a clamp or inserts, to maintain or exceed the original pressure containment rating while allowing severing at the desired tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a joint is placed between standard pipes to create a weak point, then the riser can sever at a predetermined longitudinal tension rating, but the design becomes complex involving several parts and added seals
Solution Approach 1:
The joint assembly is divided into three distinct bodies (upper, middle, lower) with the middle body containing the machined weak point. This segmentation allows the weak point functionality to be isolated in one component while the other bodies maintain standard pipe characteristics, resolving the contradiction by organizing complexity into manageable segments rather than requiring multiple separate parts and seals.
Solution Approach 2:
The invention merges the weak point creation and pressure containment functions into a single integrated joint assembly. The machined middle body simultaneously provides the tension weakness and the pressure containment structure, eliminating the need for separate seals and multiple parts that would otherwise be required to achieve both functions.
2Reliability
If material is machined out of a unitary pipe joint to create a weak point, then the riser can sever at a predetermined longitudinal tension rating, but the pressure containment rating is reduced
Solution Approach 1:
The middle body is machined with a groove or perforations at a specific location to create the tension weakness, while the rest of the joint assembly maintains full pressure containment capability. This localized modification approach allows the weak point to be created only where needed without compromising the overall pressure containment structure.
Solution Approach 2:
The joint assembly combines machined metal bodies with a pressure-containing means (such as a seal or reinforcement structure) to create a composite structure. The machined middle body provides the tension weakness while the added pressure-containing means restores and maintains the pressure containment rating, effectively combining two different structural approaches.
3Device complexity
If a simple design with few parts is used for the joint assembly, then the device complexity is reduced, but it may require additional seals to maintain pressure containment
Solution Approach 1:
The middle body serves multiple functions simultaneously: it provides the structural connection between upper and lower bodies, creates the tension weakness through machining, and maintains pressure containment either through its own structure or in conjunction with the pressure-containing means. This multi-functionality reduces the need for separate sealed components while maintaining both simplicity and reliability.
Data Source
AI summary
A joint assembly allows a riser system to have a weak point that can fail at a known location and tension value without reducing the riser pressure containment capacity. The joint assembly includes a standard riser pipe machined to remove material, for example, to form a groove. The joint assembly also comprises means for restoring pressure capacity. For example, the means for restoring pressure capacity include a combination of a thick-bodied clamp and a split insert ring. The split insert ring can bridge between the groove and the clamp, at least partially transferring the pressure load contained inside the machined pipe to the clamp.