Wedge Threaded Steel Pipe Connection for Torque-Tension Balance
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Solution Overview
Problem
Existing threaded connections for steel pipes in deep oil wells face challenges in achieving both high torque and tension performance, with current wedge thread designs not adequately addressing the impact of wedge ratio on these performance metrics.
Innovation Solution
A threaded connection design that specifies a wedge ratio between 7% and 8% for the difference between loading-flank pitch and stabbing-flank pitch, along with negative flank angles within specific ranges, to optimize both torque and tension performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the wedge ratio is increased to improve torque performance, then contact pressure increases, but the thread-crest width decreases which may cause thread crest breakage under tensile load
Solution Approach 1:
The patent optimizes the wedge ratio parameter to a specific range (7-8%) to balance torque and tension performance. This parameter change resolves the contradiction by finding the optimal value that provides sufficient contact pressure for torque while maintaining adequate thread-crest width for tensile strength.
2Ease of operation
If the thread-crest width is decreased to facilitate make-up, then the difference between loading-flank pitch and stabbing-flank pitch increases, but the ability to resist tensile load is reduced
Solution Approach 1:
The patent controls the difference between loading-flank pitch and stabbing-flank pitch (delta lead) within a specific range to balance make-up ease and tensile strength. This parameter optimization ensures sufficient thread-crest width reduction for easy make-up while maintaining adequate load-bearing capacity.
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 by increasing contact pressure and maintains tension performance by preventing thread crest breakage, while ensuring the threaded connection can resist large tensile loads effectively.
Implementation Method 1
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
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AI summary
A threaded connection for steel pipe that provides both high torque performance and high tension performance is provided. A threaded connection 1 includes a tubular pin 10 formed by one tip portion of a steel pipe and a tubular box 20 adapted to be made up on the pin 10 as the pin 10 is inserted into the box. The pin 10 includes a male thread 11 provided on an outer periphery of the pin 10, the male thread being a wedge thread. The box 20 includes a female thread 21 corresponding to the male thread 11 and provided on the inner periphery of the box 20, the female thread being a wedge thread. The threaded connection 1 satisfies the following expression, (1): 3%≤LP−SP/LP≤8% 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.