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 balancing high torque performance and tension performance, with current wedge thread designs not adequately specifying the optimal wedge ratio for both requirements.
Innovation Solution
A threaded connection for steel pipes is designed with a wedge ratio ranging from 3% to 8%, defined as (LP−SP)/LP, where LP is the pitch between loading flanks and SP is the pitch between stabbing flanks, to achieve both high torque and tension performance, with specific flank angles and thread lengths to enhance contact pressure and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If wedge thread designs use a larger difference between loading-flank pitch and stabbing-flank pitch (higher wedge ratio), then torque performance is improved, but tension performance deteriorates due to reduced thread-crest width near the tip
Solution Approach 1:
The patent applies parameter changes by optimizing the wedge ratio to a specific range (3% to 8%, calculated as (LP-SP)/LP where LP is loading-flank pitch and SP is stabbing-flank pitch). This parameter optimization balances the thread-crest width reduction needed for torque performance with the minimum width required for tension performance, resolving the contradiction between these two performance requirements.
2Ease of operation
If thread-crest width is reduced near the tip to facilitate make-up, then ease of operation is improved, but structural strength deteriorates
Solution Approach 1:
The patent applies local quality by creating a gradient in thread-crest width along the thread length. The thread-crest width is reduced near the tip (where make-up facilitation is needed) while maintaining sufficient width in other regions (where strength is needed). This is achieved through the optimized wedge ratio that controls the rate of width reduction, allowing different parts of the thread to have different properties appropriate to their functional requirements.
Data Source
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% (1).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.