Wedge-Thread Steel Pipe Coupling for Torque and Seal Balance
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Solution Overview
Problem
Existing threaded connections for steel pipes in deep oil wells face challenges in achieving high torque performance, tension performance, and sealability, with the wedge ratio's effect on these aspects not adequately evaluated in previous technologies.
Innovation Solution
A threaded connection design that includes a tubular pin and box with wedge threads, where the wedge ratio is optimized between 3% and 7%, ensuring high torque performance, tension performance, and sealability by controlling the pitch difference between loading and stabbing flanks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the thread width of wedge threads is increased to improve torque performance, then torque performance is improved, but the thread crest becomes more prone to breakage under tensile loads
Solution Approach 1:
The patent optimizes the wedge ratio parameter to a specific range (3% to 7%) to balance torque performance and tension performance. This parameter change resolves the contradiction by finding the optimal value that provides sufficient torque while preventing thread crest breakage under tensile loads.
2Power
If the wedge ratio is increased to improve torque performance, then torque performance is improved, but sealability deteriorates due to reduced contact pressure
Solution Approach 1:
The patent specifies an optimal range for the wedge ratio (3% to 7%) that balances torque performance and sealability. By constraining the wedge ratio within this range, the invention ensures that the difference between loading-flank pitch and stabbing-flank pitch maintains adequate seal contact pressure while still providing improved torque performance.
3Power
If the difference between loading-flank pitch and stabbing-flank pitch is increased to improve torque performance, then torque performance is improved, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent defines a specific range for the wedge ratio (3% to 7%), which translates to a controlled difference between loading-flank pitch and stabbing-flank pitch. This parameter specification makes the thread geometry manufacturable with standard precision while still achieving the torque performance benefits of wedge threads.
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 optimized wedge ratio enhances torque performance, tension performance, and sealability, while preventing thread crest breakage, and maintains effective seal contact pressure, ensuring reliable operation under tensile loads and pressure conditions.
Implementation Method 1
When the threaded connection is made up and the seals are fitted onto each other, the amount of interference causes the diameter of the pin seal to decrease and the diameter of the box seal to increase. Each of the seals tries to recover their original diameters and thus produces elastic recovery forces, which produce contact pressures on the seals such that the seals tightly contact each other along the entire circumference, thereby providing sealability.
Implementation Method 2
A wedge thread has a thread width that gradually changes as it goes along its helical direction. A wedge thread is also known as dovetailed thread, and provides high torque performance.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A threaded connection for steel pipe that provides high torque performance, high tension performance and high sealability is provided. A threaded connection 1 includes: a tubular pin 10 including a pin shoulder 12, a male thread 11 and a pin seal 13; and a tubular box 20 including a box shoulder 22, a female thread 21 and a box seal 23. The male and female threads 11 and 21 are constituted by wedge threads. The pin seal 13 is provided between the pin shoulder 12 and the male thread 11. The box seal 23 corresponds to the pin seal 13 and is located on the inner peripheral surface of the box 20. When the connection is made up, the pin shoulder 12 is spaced apart from the box shoulder 22. The threaded connection 1 satisfies the following expression, (1): 3%≤LP−SP/LP≤7% In expression (1), LP is the pitch between loading flanks 111 of the male thread 11, and SP is the pitch between stabbing flanks 112 of the male thread 11.