Flush Joint Thread Geometry for High-Torque Pipe Connections
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Solution Overview
Problem
Existing oil & gas pipe designs face tradeoffs between achieving good tensile efficiency and compression efficiency, with most designs failing to achieve both simultaneously at high levels.
Innovation Solution
A flush joint high torque thread design featuring angled shoulders on both sides of the thread, with lead-in chamfers on stab flanks and tapered load flanks, allowing for 70% tensile efficiency and 90% compression efficiency by optimizing thread geometry and shoulder engagement during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional thread designs are used, then manufacturing is simpler, but tensile efficiency and compression efficiency cannot both be achieved at high levels
Solution Approach 1:
The thread design segments the flanks into distinct stab flanks and load flanks with different geometric characteristics. Stab flanks have lead-in chamfers for easy assembly, while load flanks are tapered for high torque transmission. This segmentation allows each part to optimize its function independently, achieving both high tensile efficiency (70%) and compression efficiency (90%) without excessive overall complexity.
Solution Approach 2:
Different regions of the thread are given different local qualities: stab flanks feature lead-in chamfers angled at 5-15 degrees for smooth engagement, while load flanks have taper angles of 1-5 degrees for torque transmission. The shoulders are positioned at specific locations to provide axial load bearing. This localized optimization of geometric properties enables simultaneous high tensile and compression efficiency.
2Force
If thread geometry is optimized for high torque, then torque transmission improves, but tensile and compression efficiency tradeoffs worsen
Solution Approach 1:
The thread design employs asymmetric geometry where stab flanks and load flanks have different angles and functions. Stab flanks are designed with larger lead-in chamfers (5-15 degrees) for assembly ease, while load flanks have smaller taper angles (1-5 degrees) for torque transmission. This asymmetric design allows the thread to simultaneously achieve high torque capability and balanced tensile-compression efficiency without the tradeoffs of symmetric designs.
Solution Approach 2:
The thread design creates dynamic engagement characteristics where stab flanks engage first during assembly (providing guidance and ease of connection), then load flanks engage under torque loading (providing torque transmission). The shoulders provide axial load bearing. This dynamic sequence of engagement ensures high torque transmission while maintaining both tensile and compression efficiency.
Data Source
AI summary
A flush joint high torque thread that achieves superior tensile efficiency and compression efficiency. In one example, the thread of a pin member and a box member includes a thread a chamfer with angled shoulders on each side of the thread to achieve increased torque. The stab flanks each contain a lead-in chamfer extending no further than a thread pitch line. The load flanks are each tapered. The stab flanks engage each other during assembly, but not upon assembly. The load flanks do not engage each other during assembly, and do engage each other upon assembly. The pipe achieves both a 70% tensile efficiency and a 90% compression efficiency.