Tubular Coupling With Mismatched Thread Radii for Reusable Sealing
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Solution Overview
Problem
Existing tubular connections in oilfield applications require complex and expensive specialty threading, which can be a failure point and incur high replacement costs when threads wear down.
Innovation Solution
A tubular connection design featuring mismatched radii external and internal threads, along with a torque-stop surface and radially-facing sealing surfaces, allows for secure engagement without the need for precise matching, facilitating easier assembly and disassembly while maintaining high torsional load capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If specialty threading is used for tubular connections, then connection strength is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent employs asymmetric thread profiles where the external thread and internal thread have different geometries. The external thread features a flattened top portion while the internal thread has a corresponding recess, creating an asymmetric engagement that provides strong mechanical interlocking without requiring complex specialty threading. This asymmetric design simplifies manufacturing while maintaining connection strength.
2Strength
If specialty threading is used for tubular connections, then connection strength is improved, but replacement cost increases
Solution Approach 1:
The patent designs the thread engagement such that the tubulars can be disconnected and reused. The asymmetric thread profile with flattened portions allows for controlled disengagement without damaging the tubulars themselves. Only the coupling device needs replacement, not the expensive tubulars, thereby reducing replacement costs while maintaining strong connections during use.
3Reliability
If complex threading is used for tubular connections, then connection reliability is improved, but ease of assembly deteriorates
Solution Approach 1:
The patent incorporates a flattened top portion on the external thread and a corresponding recess in the internal thread that are pre-formed during manufacturing. This preliminary action creates self-aligning features that guide the threading engagement process, making assembly easier while maintaining reliable mechanical interlocking. The flattened portions act as alignment guides that prevent cross-threading and facilitate smooth engagement.
Data Source
AI summary
A tubular connection includes an inner body having a bore, external threads defining external thread surfaces, a torque nose, and a radially-facing sealing surface, and an outer body having a bore in communication with the bore of the inner body, internal threads defining internal thread surfaces and being configured to engage the external threads of the inner body, a torque-stop surface that engages the torque nose, and a radially-facing sealing surface that forms a seal with the radially-facing sealing surface of the inner body. The external threads define a first radius between two of the external thread surfaces, the internal threads define a second radius between two of the internal thread surfaces, the external threads where the first radius is defined being configured to engage the internal threads where the second radius is defined, the first and second radii being mismatched.