Asymmetric Flank Threaded Joint for High Torque
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Solution Overview
Problem
Conventional threaded joints in the oil and gas industry face challenges in achieving high torque performance due to limitations in torque capacity, energy absorption, fatigue resistance, and manufacturing complexity, particularly with wedge threads that require tight machining tolerances and viscous greases, which can decrease torque and increase the risk of thread damage.
Innovation Solution
A threaded joint with a flank-to-flank contact trapezoidal thread profile featuring low and positive load and stabbing flank angles, combined with a dope-free surface coating, allowing for full compliance with a mathematical model and reducing pressure differences during make-up and break-out, thereby achieving high and consistent torque without the need for viscous lubricants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If wedge threads with dovetail shape are used to achieve strong connection and control stress, then connection strength is improved, but thread edges may contact during make up and break down causing damage
Solution Approach 1:
The patent employs asymmetric thread flank angles with the load flank at a lower angle (1° to 10°) and the stabbing flank at a higher angle (10° to 30°). This asymmetric configuration optimizes both load bearing capacity and reduces the risk of edge contact during make up and break down operations, resolving the contradiction between connection strength and thread damage risk
2Force
If wedge thread configurations are used to achieve high torque, then torque capacity is improved, but energy absorption is very low and fatigue resistance decreases
Solution Approach 1:
The patent changes the geometric parameters of the thread profile, specifically using a load flank angle of 1° to 10° and a stabbing flank angle of 10° to 30°. This parameter optimization allows the thread to achieve high torque capacity while improving energy absorption and fatigue resistance by distributing stresses more effectively across the thread engagement
3Force
If wedge threads with acute angles are used to achieve high torque, then torque is improved, but manufacturing complexity increases due to tight machining tolerances
Solution Approach 1:
The patent selects specific parameter ranges for the thread flanks (load flank: 1° to 10°, stabbing flank: 10° to 30°) that balance torque performance with manufacturability. These optimized parameters reduce the stringency of machining tolerances while maintaining high torque capacity, making the threads easier to manufacture and inspect
4Force
If viscous grease dope is used to achieve high torque with modified wedge thread geometry, then torque is improved, but contact pressure between flanks decreases and torque is reduced
Solution Approach 1:
The patent removes the viscous grease dope from the thread interface and replaces it with a dope-free coating system. This extraction of the harmful viscous medium eliminates the pressure differential effect that reduced contact pressure, allowing the optimized thread geometry to achieve high torque through direct flank-to-flank contact without the detrimental influence of viscous lubrication
5Ease of manufacture
If dope-free surface coating is used instead of viscous grease, then manufacturing ease is improved, but torque capacity may be reduced without proper thread geometry
Solution Approach 1:
The patent combines a dope-free coating material with an optimized composite thread geometry (asymmetric flank angles with load flank at 1° to 10° and stabbing flank at 10° to 30°). This composite approach—integrating the coating properties with the geometric design—ensures that torque capacity is maintained or enhanced while eliminating the complexities associated with viscous grease application and removal
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 solution provides a high torque connection with reduced risk of disengagement and thread damage, maintaining consistency across make-up and break-out operations, and is easier to manufacture and inspect, with significant improvements in torque values compared to conventional dope-coated configurations.
Implementation Method 1
The threads are coated with a solid, dope-free surface treatment
Data Source
AI summary
A high torque threaded joint comprising a box member having threads and a pin member having threads (10) configured and positioned to mate with the threads of the box member. There is a flank-to-flank contact thread profile using trapezoidal threads with both a positive and very low load flank angle, (β1 or a); and a positive and very low stabbing flank (14) angle, (β2, or b), wherein the threads are coated with a solid, dopefree surface treatment.