Threaded Pipe Joint Shoulder Geometry for Torque and Galling Control
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Solution Overview
Problem
Threaded joints used in shale development face challenges in achieving a balance between high torque, seizure resistance, and airtightness while maintaining cost-effectiveness, as uneven contact between pin shoulders leads to plastic deformation and increased risk of galling during tightening.
Innovation Solution
A threaded joint design where the relationship between shoulder angle and thread taper angles is optimized to prevent excessive plastic deformation, with a defined range of Δθ−Δω (−1.5°≤Δθ−Δω≤2.0°) and a thread fitting ratio of 0.0032 to 0.0059, ensuring suitable contact conditions for high torque and airtight performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If shoulders of pins are abutted against each other to set high tightening torque, then torque performance is improved, but uneven contact causes plastic deformation and increased risk of galling
Solution Approach 1:
The invention changes the geometric parameters of the shoulder faces by specifying precise angular relationships between the shoulder angle (θ) and thread taper angle (ω). The condition −1.5°≤Δθ−Δω≤2.0° where Δθ=θA+θB and Δω=ΔωA+ΔωB optimizes the contact distribution, ensuring uniform stress distribution across the shoulder faces during tightening, thereby preventing plastic deformation and galling while maintaining high torque capability.
2Reliability
If premium joint with independent seal section is used to achieve high airtightness, then airtight performance is improved, but manufacturing cost and dimensional accuracy requirements increase
Solution Approach 1:
The invention merges the sealing function with the shoulder abutment structure. The optimized shoulder face contact conditions (−1.5°≤Δθ−Δω≤2.0°) create sufficient contact pressure between the pin shoulders to ensure airtightness without requiring a separate seal section. This integration eliminates the need for additional sealing components and reduces manufacturing complexity while maintaining high airtight performance.
3Strength
If thread fitting ratio is increased to improve connection strength, then joint strength is improved, but stress concentration and plastic deformation increase
Solution Approach 1:
The invention optimizes the thread fitting ratio within the specific range of 0.0032 to 0.0059. This parameter optimization, combined with the shoulder angle relationship (−1.5°≤Δθ−Δω≤2.0°), distributes stress uniformly across the connection interface. The optimized parameters ensure sufficient connection strength while preventing excessive stress concentration that would lead to plastic deformation, thereby reducing the stringency of dimensional accuracy requirements.
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 contact conditions reduce stress concentration and plastic deformation, enhancing the joint's torque performance and airtightness, while being cost-competitive and versatile by avoiding the need for high-dimensional accuracy and long sealing sections.
Implementation Method 1
uneven contact between pin shoulders leads to plastic deformation
Implementation Method 2
radial interference is created to secure the pins 206 in the coupling 204
Data Source
AI summary
A threaded joint wherein a relationship between shoulder angle parameters and thread taper angle parameters for a coupling and a pair of pins inserted from both ends of the coupling is defined by the following expression (1), and a tightening torque with which the threaded joint is tightened is 60% or more and 85% or less of a yield torque determined by the following expression (2):-1.5°≤Δθ-Δω≤2.°,(1)T=(TS+TD)112(2)TS=ftPcE72(2πE 7)L412Pc=Eρm2((W2)2-(E72)2)((E72)2-(d2)2)2(E72)3((W2)2-(d2)2)TD=YmAS(P2π+RtfscosΘ+Rsfs).