Blowout Preventer Bonnet Retention Using Interrupted Threads
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Solution Overview
Problem
Existing wellhead assembly systems, particularly blowout preventers, face challenges in efficiently and safely securing bonnets due to the need for manual handling and rotation of heavy nuts with traditional circumferential threads, which is time-consuming and labor-intensive.
Innovation Solution
The use of mating fasteners with interrupted thread patterns, comprising nuts and shafts, allows for secure connection and retention of bonnets to the blowout preventer's hollow body, enabling axial movement and rotation to engage threads quickly, reducing the need for manual handling and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional circumferential threaded fasteners are used to connect bonnets to blowout preventers, then secure connection is achieved, but manual handling and rotation of heavy nuts is time-consuming and labor-intensive
Solution Approach 1:
The circumferential thread pattern is segmented into discrete radial segments with gaps between them. Each segment is spaced apart to allow tools to access and rotate the fasteners from radial directions, eliminating the need to rotate heavy nuts manually around the entire circumference.
Solution Approach 2:
The thread engagement transitions from a traditional circumferential rotation in the horizontal plane to a radial engagement where fasteners can be accessed and rotated from vertical or radial directions. This dimensional change allows for easier tool access and reduced manual handling of heavy components.
2Reliability
If heavy nuts with traditional threads are used, then secure fastening is achieved, but time required for fastening or unfastening bonnets increases
Solution Approach 1:
The threaded connection is segmented into discrete radial sections rather than continuous circumferential threads. This segmentation allows for quicker engagement and disengagement while maintaining secure connection through the distributed radial thread segments.
Solution Approach 2:
The bonnet and blowout preventor are pre-aligned using alignment features before the final threaded engagement. This preliminary alignment reduces the time required for fastening by eliminating the need for complex manual alignment of heavy components during the fastening process.
3Strength
If traditional fastening methods are used, then bonnets can be secured, but manual handling of heavy nuts increases labor intensity
Solution Approach 1:
The fastening system uses multiple discrete radial thread segments instead of a single heavy circumferential nut. This distributes the fastening load across multiple smaller fasteners that can be independently manipulated, reducing the operational effort required while maintaining overall fastening strength.
Solution Approach 2:
The fastening approach changes from horizontal circumferential rotation of heavy nuts to vertical or radial engagement of smaller fasteners. This dimensional change significantly reduces the manual effort and labor intensity while achieving equivalent or superior fastening strength through the distributed radial configuration.
Data Source
AI summary
Methods and systems for retaining bonnets on blowout preventers. In one embodiment, a blowout preventer includes a hollow body, a ram disposed in a ram cavity of the hollow body, and a bonnet coupled to the hollow body. The bonnet is fastened to the hollow body with threaded fasteners, which include a threaded shaft and a threaded nut. The shaft and the nut include mating interrupted threads with threaded portions and longitudinal unthreaded portions that can be rotationally aligned so that threaded portions of each of the shaft and the nut are aligned with unthreaded portions of the other of the shaft and the nut to allow the threaded shaft to be received within the threaded nut and the threaded nut to then be rotated with respect to the threaded shaft to cause the threaded portions of the threaded nut to engage the threaded portions of the threaded shaft.