Curvilinear Radial Seal Coupling for Leak-Tight Fracking Joints
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Solution Overview
Problem
Conventional coupling technologies in the oil and gas industry face challenges such as mechanical failure, high production costs, cumbersome installation, and unreliable sealing due to frustoconical seal designs, which lead to axial distance variations and radial stresses, compromising safety and efficiency in high-pressure fracking operations.
Innovation Solution
A coupling design featuring curvilinear surfaces with a shared longitudinal central axis, utilizing a radial seal formed from the intersection of these surfaces, which limits diametric interference and moves from maximum to minimum radial interference under torque, thereby stabilizing the threads and preventing galling and leaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frustoconical seal engagement is used, then sealing is achieved, but axial distance variations occur and radial stresses increase leading to unreliable sealing
Solution Approach 1:
The patent replaces the frustoconical (tapered) seal surface with a curvilinear surface that has a radius of curvature. This curved surface allows the seal to accommodate axial distance variations while maintaining consistent contact and sealing pressure, eliminating the radial stresses caused by wedge threads and preventing both over-interference and under-interference sealing failures.
2Ease of manufacture
If wedge threads with small lead differences are used, then material removal and machining time are reduced, but axial distance variations increase before wedge-like engagement
Solution Approach 1:
The curvilinear seal surface with radius of curvature compensates for axial distance variations that occur during the make-up process. This allows the use of wedge threads with smaller lead differences (reducing machining time) while the curved surface ensures proper seal engagement is achieved regardless of the axial variation, eliminating the trade-off between machining efficiency and engagement consistency.
3Reliability
If conical seals with small tapers are used to compensate for seal position variability, then sealing is improved, but device complexity and length increase
Solution Approach 1:
The patent uses a curvilinear surface with a specific radius of curvature instead of a conical surface with small taper. This curved geometry achieves consistent sealing across variable positions without requiring the complex, long conical sections, thereby maintaining sealing reliability while reducing device complexity and overall length.
4Reliability
If frustoconical seals are used, then sealing is achieved, but hoop stresses and radial stresses increase causing thread disengagement
Solution Approach 1:
The curvilinear seal surface eliminates the wedge-like engagement that causes radial stresses and thread disengagement. The curved surface distributes sealing pressure uniformly without creating the ramp effect of conical seals, thereby maintaining sealing effectiveness while preserving thread bearing strength and preventing connection failure under cyclic loads.
Data Source
AI summary
A non-frustoconical coupling provides a mechanical connection used in fluid transport for hydrocarbon recovery operations.