Flush Self-Locking Threaded Connection for High-Torque Sealing
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Solution Overview
Problem
Conventional threaded connections for shale gas wells face challenges in providing high torque capacity, seal performance, and manufacturing efficiency, especially for small pipe diameters, while also needing to withstand tension, compression, and cyclic fatigue, and maintaining well integrity under complex well configurations.
Innovation Solution
A self-locking threaded connection design with a male and female threaded zone featuring varying thread root widths and crest widths, allowing for a flush connection that achieves sufficient torque and seal performance without requiring extensive make-up torque, utilizing a partially self-locking arrangement to reduce manufacturing costs and improve assembly efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional threaded connections are used with abutment surfaces to achieve high torque capacity, then torque transmission is improved, but the critical plastication threshold is rapidly reached especially for small diameter pipes, limiting further torque increase
Solution Approach 1:
The threaded connection is divided into multiple engagement zones: a first engagement zone with a first thread pitch and a second engagement zone with a second thread pitch. This segmentation allows different portions of the threads to承担 different functions, distributing the torque transmission across multiple zones with varying characteristics.
Solution Approach 2:
Different sections of the threaded connection have different thread pitches optimized for different functions. The first engagement zone has a coarser pitch for initial engagement and torque transmission, while the second engagement zone has a finer pitch for precision and load distribution. This local differentiation optimizes both torque capacity and prevents plastication.
2Reliability
If self-locking threaded arrangement is used to provide seal performance and torque capacity, then sealing is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The thread pitch parameter is varied along the length of the threaded connection, with the first engagement zone having a different pitch than the second engagement zone. This parameter change enables self-locking behavior and improved seal performance without requiring complex additional components or manufacturing processes.
3Area of stationary object
If flush connection is used to maintain outer diameter below 101% of pipe body, then space efficiency is improved, but torque capacity is reduced due to limited thread engagement area
Solution Approach 1:
Instead of increasing torque capacity by increasing radial dimensions (which would violate the flush connection requirement), the invention extends the thread engagement in the axial dimension by providing multiple engagement zones with different pitch characteristics, thereby achieving high torque capacity within the constrained outer diameter.
Solution Approach 2:
The threaded connection is divided into multiple engagement zones: a first engagement zone with a first thread pitch and a second engagement zone with a second thread pitch. This segmentation allows different portions of the threads to承担 different functions, distributing the torque transmission across multiple zones with varying characteristics.
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 connection provides enhanced torque capacity, seal performance, and manufacturing efficiency, allowing for reliable operation in shale gas wells with complex configurations, while maintaining a flush profile and reducing the risk of handling damage and machining costs.
Implementation Method 1
self-locking threaded connection
Data Source
Figure 1
Figure 2~4
Figure 5~6
AI summary
A flush self-locking threaded connection partially in a non-locking engagement comprises a first (1) and a second (2) tubular component provided respectively with male and female threaded zone at their respective ends. First portions of the male (9) and female (10) threaded zones with varying thread width and root cooperate along a self-locking tightening arrangement. A locking region within the threaded connection is located in the middle of non-locking regions, and radially centered to the pipe body API tolerances in order to withstand high torque and seal performances.