Wedge-Threaded Pipe Connection for Low-Torque Leak Tightness
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Solution Overview
Problem
Threaded pipe connections in the oil and gas industry face challenges with leak tightness, requiring high torques for sealing, which can lead to localized stress and fatigue issues, and often trap thread compounds, affecting performance.
Innovation Solution
The design incorporates wedge-shaped pin and box threads with tapered profiles, where the pin thread crest widens and the box thread root narrows, allowing for improved sealing without additional metal-to-metal seals or compounds, reducing stress, and facilitating controlled evacuation of thread compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high torque is applied to seal threaded connections, then sealing ability is improved, but localized stress increases and fatigue life deteriorates
Solution Approach 1:
The patent applies different taper angles to different portions of the threaded connection. The pin member has a first taper angle on its leading portion and a second taper angle on its trailing portion, with the trailing portion having a greater taper angle. This creates localized variations in thread engagement characteristics, allowing optimal sealing at the leading threads while distributing stress more favorably across the connection, thereby improving sealing ability without proportionally increasing localized stress.
2Reliability
If traditional threaded connections are used, then simplicity is maintained, but leak tightness is insufficient
Solution Approach 1:
The patent modifies the geometric parameters of the threaded connection by implementing varying taper angles along the length of the pin member. The transition from a uniform taper to a variable taper profile changes the engagement characteristics of the threads, improving leak tightness through better contact pressure distribution without requiring additional sealing components or complex assembly procedures.
3Reliability
If uniform thread width is used, then manufacturing is simplified, but sealing performance is reduced
Solution Approach 1:
The patent implements non-uniform thread geometry where the thread width varies along the length of the pin member. The leading threads have different dimensional characteristics compared to the trailing threads, with the varying width creating optimized contact surfaces for sealing. This localized variation in thread dimensions improves sealing performance while maintaining a relatively simple monolithic manufacturing approach for the pin member.
Data Source
AI summary
Provided is a threaded pipe having a pin member connecting to a box member. The pin member contains wedge-shaped pin threads that extends in a helical direction around the outside surface of its pipe end. The pin member is tapered to result in an increasing diameter of the pin threads away from the front end of its pipe. The box member contains a wedge-shaped box thread that stretches in a helical direction around the inside surface of its pipe end. The box member is tapered to result in a decreasing diameter of the box threads away from the front end of its pipe. The pin crest of the pin member increases in width along the pin thread and the box root of the box thread decreases in width along the box thread. When assembled together, the pin thread crest increases in width at a different rate than the box thread root increase in width.