Pull-head release mechanism for subsea riser bend stiffener
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Solution Overview
Problem
Existing subsea bend restrictor/limiter systems face damage during pull-in operations due to high installation loads, particularly when there are large angular misalignments between the shaft assembly and the guide funnel assembly, and require manual removal of holdback clamp assemblies by ROVs or divers.
Innovation Solution
An automatic release system with spring-loaded dogs and stopper mechanisms is integrated into the shaft assembly, allowing for controlled load distribution and automated disengagement from the pull-head during pull-in operations, preventing damage and simplifying the process by enabling load transfer through the dogs and subsequent disengagement when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a holdback clamp assembly is used to prevent slipping during pull-in operations, then the shaft assembly and bend restrictor/limiter are protected from slipping, but the system requires manual removal by ROV or diver and may still be damaged by high installation loads
Solution Approach 1:
The connector assembly performs self-service through automatic engagement and disengagement. The spring-loaded dogs automatically engage with the guide funnel assembly during pull-in operations and automatically disengage when the shaft reaches its final position, eliminating the need for manual intervention by ROV or diver to remove holdback clamp assemblies
Solution Approach 2:
The system transitions from a static holdback clamp to a dynamic spring-loaded dog mechanism that automatically adjusts during operation. The spring-loaded dogs can move radially to engage and disengage based on the pull-in force and position, providing adaptive protection without requiring manual removal
2Productivity
If the end of the bend restrictor/limiter is used to transfer pull-in loads, then the shaft assembly can be pulled into the guide funnel assembly, but the end may be damaged due to high installation loads and angular misalignments
Solution Approach 1:
The spring-loaded dogs act as an intermediary load transfer mechanism between the pull-head and the guide funnel assembly. Instead of directly transferring loads to the bend restrictor/limiter end, the dogs engage with the guide funnel assembly to absorb and distribute the installation loads, protecting the bend restrictor/limiter from damage
Solution Approach 2:
The spring-loaded dogs provide beforehand cushioning by being pre-positioned to engage with the guide funnel assembly during pull-in operations. This pre-positioned engagement mechanism cushions the bend restrictor/limiter against high installation loads and angular misalignments before damage can occur
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 automatic release system effectively distributes pull-in loads, reducing the risk of damage to the bend restrictor/limiter and facilitating smoother subsea operations by automating the load transfer and disengagement process, thereby enhancing operational efficiency and safety.
Implementation Method 1
one or more spring-loaded dogs mounted on the outside of the shaft. The dogs may radially move in and out through one or more openings in the shaft
Data Source
AI summary
An automatic release system for a riser includes a guide funnel assembly that receives a shaft coupled to the riser. A pull-head is located inside at least a portion of the shaft and coupled to the shaft. The pull-head is coupled to a pulling mechanism. One or more spring-loaded dogs are mounted on the outside of the shaft. The dogs radially move in and out through one or more openings in the shaft aligned with the dogs and engage a groove on the pull-head when radially moved in through the openings. One or more stopper mechanisms are mounted on the outside of the shaft and aligned with the dogs. In a first position, the stopper mechanisms inhibit the dogs from disengaging from the groove in the pull-head. In a second position, the stopper mechanisms allow the dogs to disengage from the groove in the pull-head.