Two-Step Pipe Thread Connection for Compression-Resistant Sealing
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Solution Overview
Problem
Integral, flush-type/semi-flush-type threaded connections with a two-step thread construction face challenges in maintaining sealability due to deformation under compressive loads, which affects the contact width of intermediate shoulder surfaces and reduces tensile strength and sealability.
Innovation Solution
The threaded connection design includes a tubular pin and box with male and female threads constructed such that the clearance between the stab flanks upon completion of make-up allows the stab flanks to contact each other before excessive deformation occurs, thereby distributing the axial compressive load effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intermediate shoulder surfaces are provided in a two-step thread construction to maintain sealability, then sealability is improved, but the contact width of intermediate shoulder surfaces decreases under compressive loads, reducing tensile strength and sealability
Solution Approach 1:
The patent applies parameter changes by carefully controlling the clearance between stab flanks within a specific range (0.01mm to 0.05mm) to optimize the balance between sealability and strength. This parameter adjustment ensures that the stab flanks make contact under compressive loads, distributing the load effectively while maintaining the integrity of the intermediate shoulder surfaces and their sealing function.
2Reliability
If the clearance between stab flanks is reduced to maintain sealability, then sealability is improved, but the compression resistance decreases as intermediate shoulder surfaces deform more easily under load
Solution Approach 1:
The patent optimizes the clearance parameter between stab flanks to a specific range (0.01mm to 0.05mm) that balances sealability and compression resistance. This parameter setting ensures that the stab flanks contact each other under compressive loads, distributing the compressive force effectively while preventing excessive deformation of the intermediate shoulder surfaces, thus maintaining both sealability and compression resistance.
Solution Approach 2:
The patent applies preliminary action by pre-setting the clearance between stab flanks during manufacturing within the optimal range. This preliminary configuration ensures that when compressive loads are applied during operation, the stab flanks are already positioned to make contact at the appropriate load level, distributing the compressive forces before excessive deformation can occur, thereby maintaining compression resistance and sealability.
3Force
If the clearance between stab flanks is increased to improve compression resistance, then compression resistance is improved, but the contact width of intermediate shoulder surfaces decreases, reducing tensile strength
Solution Approach 1:
The patent applies parameter changes by optimizing the clearance between stab flanks to a specific range (0.01mm to 0.05mm) that balances compression resistance and tensile strength. This parameter adjustment ensures that the stab flanks make contact under compressive loads, distributing the compressive force effectively, while preventing excessive deformation of the intermediate shoulder surfaces that would reduce tensile strength and sealability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the compression resistance of the threaded connection by limiting the angle of shoulder rotation, reducing damage to intermediate shoulder surfaces, and maintaining sealability even under high compressive loads.
Implementation Method 1
when a predetermined axial compressive load smaller than a yield compressive load of the pin and the box is applied, the pin and the box deform in such a manner that the stab flanks of the male thread and the female thread start to be in contact so as to bear part of the axial compressive load
Data Source
AI summary
In a threaded connection for pipe having a two-step thread construction with intermediate shoulder surfaces, compression resistance is further improved. Upon completion of make-up of the pin 2 and box 3, the diameter of a stabbing clearance is 0.15 mm or smaller, where the stabbing clearance is defined between the stab flank of a male thread including an inner thread portion 27 and an outer thread portion 23 and the stab flank of a female thread including an inner thread portion 36 and an outer thread portion 32, thereby causing the stab flanks of the male and female threads to start to be in contact before the angle of rotation θ of the intermediate shoulder surfaces 25 and 34 as appearing in a longitudinal cross section starts to rapidly increase, thus preventing accumulation of damage in the intermediate shoulder surfaces 25 and 34.