Stepped Threaded Joint Structure for High-Tensile Pipe Connections
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Solution Overview
Problem
Conventional threaded joints used in oil and gas wells lack sufficient tensile strength, particularly at the end positions where the cross-sectional area is smaller, leading to potential fractures under tensile loads.
Innovation Solution
A threaded joint design with specific cross-sectional area ratios and lengths in the first and second thread sequences, along with a radial seal structure and tapered threads, is implemented to distribute tensile loads effectively and prevent fractures, using formulas (P2, B2)min≤P1/{L1/(L1+L2)} and (P2, B2)min≤B1/{L2/(L1+L2)} to optimize stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a reinforcement section is added to maintain rigidity, then rigidity is improved, but tensile strength is not sufficiently improved
Solution Approach 1:
The threaded joint is divided into two thread sequences (first and second) with different functional characteristics. The first thread sequence has larger cross-sectional area for strength, while the second has smaller cross-sectional area for flexibility and sealability. This segmentation allows each portion to optimize for its specific function rather than compromising overall performance.
Solution Approach 2:
Different portions of the threaded joint are given different cross-sectional areas tailored to their specific functional requirements. The first thread sequence location receives enhanced cross-sectional area for strength where needed, while the second thread sequence maintains smaller area for flexibility. This localized optimization resolves the contradiction between rigidity and tensile strength.
2Strength
If the cross-sectional area at thread ends is increased to improve tensile strength, then tensile strength is improved, but sealability and flexibility are reduced
Solution Approach 1:
The threaded joint is divided into two thread sequences (first and second) with different functional characteristics. The first thread sequence has larger cross-sectional area for strength, while the second has smaller cross-sectional area for flexibility and sealability. This segmentation allows each portion to optimize for its specific function rather than compromising overall performance.
Solution Approach 2:
Different portions of the threaded joint are given different cross-sectional areas tailored to their specific functional requirements. The first thread sequence location receives enhanced cross-sectional area for strength where needed, while the second thread sequence maintains smaller area for flexibility and sealability where required.
Data Source
AI summary
A threaded joint with excellent tensile strength, comprising: a pin having an externally threaded part comprising a first and second externally threaded sections across a step on an outer periphery on a distal-end side of a first steel pipe or tube; and a box having an internally threaded part comprising a first and second internally threaded sections across the step on an inner periphery on a distal-end side of a second steel pipe or tube, the externally threaded part being screwed to the internally threaded part to join the pin and the box. The threaded joint has a first and second thread sequence with lengths L1 and L2, respectively, and cross-sectional areas P1, P2, B1, and B2 at end positions 4, 5, 6, and 7, respectively, satisfying Formulas (1) and (2): (P2, B2)min≤P1/{L1/(L1+L2)}(1) and (P2, B2)min≤B1/{L2/(L1+L2)}(2), where (P2, B2)min represents P2 or B2, whichever is smaller.