Partial Self-Locking Threaded Connection for High Make-Up Torque
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Solution Overview
Problem
Existing self-locking threading connections face limitations in providing high make-up torque and semi-premium sealability, especially in applications requiring a maximum outer diameter of the box member to be less than 6% over the nominal outer diameter, while also needing wider machining tolerances and improved durability.
Innovation Solution
A threaded connection design featuring a self-locking thread configuration with varying thread widths, where only a portion of the threaded zones are in self-locking engagement, allowing for high make-up torque and semi-premium sealability, while maintaining a compact design and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional abutment surfaces are used for make-up torque transmission, then the connection can be assembled, but the critical plastication threshold of the abutment surfaces is rapidly reached when too great a make-up torque is applied
Solution Approach 1:
The threaded zone is segmented into a locking portion and a non-locking portion. The locking portion engages first to transmit make-up torque through distributed thread contact, preventing abutment surface plastication. The non-locking portion engages later to provide additional torque capacity and sealing, resolving the contradiction between torque transmission and abutment surface strength.
Solution Approach 2:
Different portions of the threaded zone have different functional qualities: the locking portion is designed for torque transmission with varying thread widths, while the non-locking portion is designed for sealing with constant thread widths. This local differentiation allows the connection to achieve both high make-up torque capacity and protection against abutment surface failure.
2Force
If self-locking threading is used to increase make-up torque capacity, then torque transmission is improved, but the device complexity increases
Solution Approach 1:
Only a portion of the threaded zone (the locking portion) is designed with self-locking characteristics featuring varying thread widths. The remaining non-locking portion uses constant thread widths for sealing. This partial application of self-locking design achieves high torque capacity without the full complexity of a completely redesigned threaded connection.
3Shape
If the maximum outer diameter of the box member is constrained to be less than 6% over the nominal outer diameter, then compactness is achieved, but the ability to provide high make-up torque and semi-premium sealability is limited
Solution Approach 1:
The solution moves from relying solely on radial dimension (outer diameter) to utilize the axial dimension of the threaded zone. By extending the threaded zone axially with locking and non-locking portions, the connection achieves high torque capacity and sealability within the constrained outer diameter, effectively trading radial for axial space utilization.
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 achieves high make-up torque without requiring specific torque charts, allows for efficient liquid sealing meeting ISO 13679:2002 CAL-I standards, and demonstrates improved durability through enhanced structural support and resistance to damage during handling and operation.
Implementation Method 1
locking occurs for self-locking threading when both all the stab flanks and all the load flanks of the male threads (or teeth) lock against respectively all the stab flanks and all the load flanks of the corresponding female threads (or teeth). For this reason, the make-up torque is taken by all of the contact surfaces between the flanks, i.e. a total surface area which is very substantially greater than that constituted by the abutment surfaces of the prior art.
Data Source
Figure 1~3
Figure 4~6
Figure 7~9
AI summary
The threaded connection partially in a self-locking arrangement comprises a first and a second tubular component provided respectively with male and female threaded zone at their respective ends. Only a portion (10p) of a first portion (11) with varying thread width of the male threaded zone (3) cooperate by self-locking tightening with only a portion (10b) of the second portion (12) with varying thread width of the female threaded zone (4) when made up one into the other. The connection is able to withstand high torques required for special applications such as drilling with casing or intermediate casing.