Oil Well Pipe Threaded Joint With Stiffened Coupling Seal
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Solution Overview
Problem
Slim-type threaded connections for oil wells with large wall thickness face challenges in maintaining high sealing performance due to deformation under internal pressure, as conventional methods to improve sealing by altering thread shapes are ineffective in preventing diameter increase and subsequent leaks.
Innovation Solution
The design incorporates a tubular coupling with a recess portion of increased wall thickness and specific length, which enhances the stiffness of the coupling, preventing box deformation and maintaining contact force during internal pressure application without increasing the outer diameter of the coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the wall thickness of the box is reduced to achieve slim-type connection with outer diameter equal to pipe body, then the connection efficiency becomes less than 1, but the box deforms under internal pressure causing seal contact force to decrease and leading to leaks
Solution Approach 1:
The coupling is designed with non-uniform wall thickness: the box portion has reduced wall thickness to achieve slim-type connection, while the recess portion has increased wall thickness to provide stiffness and prevent deformation under internal pressure. This local differentiation allows the connection to maintain both small outer diameter and high sealing reliability.
2Reliability
If various thread or seal shapes are devised to improve sealing performance, then sealing performance may be improved, but these methods are ineffective in preventing box deformation and diameter increase under internal pressure
Solution Approach 1:
The invention changes the structural parameter of the coupling by introducing a recess portion with increased wall thickness. This parameter change increases the stiffness of the coupling body, thereby preventing box deformation under internal pressure and maintaining seal contact force, which is more effective than merely changing thread or seal shapes.
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
This configuration provides high sealing performance by maintaining the contact force of the seal, even under high internal pressure, effectively addressing the limitations of slim-type connections with connection efficiency less than 1.
Implementation Method 1
The design incorporates a tubular coupling with a recess portion of increased wall thickness and specific length, which enhances the stiffness of the coupling, preventing box deformation and maintaining contact force during internal pressure application
Implementation Method 2
maintaining contact force of the seal formed by pin and box sealing surfaces contacting each other
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
High sealing performance is provided in a threaded connection used for pipes for oil wells with large wall thickness and with a connection efficiency smaller than 1. A threaded connection (10) connects pipes for oil wells (1). The threaded connection (10) includes two pins (11) and a tubular coupling. Each of the pins (11) is provided on an end of the pipe for oil wells (1) and is in continuity with the pipe body (12), which has a wall thickness not smaller than 12 mm. The coupling (2) includes two boxes (21) and a recess portion (22). The box (21) is provided on both ends of the coupling (2). The recess portion (22) has a length not smaller than 10 mm. The threaded connection (10) has a connection efficiency smaller than 1. When the wall thickness of the pipe body (12) is expressed as tpipe, the wall thickness and length of the recess portion (22) are expressed as t1 and 2×L1, respectively, and the length of each of the boxes (21) is expressed as L2, and if the following expressions (1) and (2) define T and L, then, T and L satisfy the following expression (3): T=t1tpipe L=L1L1+L2 T⋅L1/15>1.4