Tubular Threaded Joint Lip Zone Compression Resistance
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Solution Overview
Problem
Conventional tubular threaded joints face challenges in resisting compression and maintaining sealing performance under external pressure, especially in vertical or sloping wells, due to deformation of the lip zone under compressive loads and external pressure.
Innovation Solution
The design enhances the tubular threaded joint by extending the lip zone length to at least 140 times the stabbing flank clearance, incorporating a noncontacting region between the metal-to-metal seal and shoulder surfaces, and optimizing the shape of the stabbing flank with multiple slope portions and chamfers to reduce plastic deformation and improve resistance to compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the lip zone length is extended to increase resistance to compression, then the joint can withstand higher compressive loads, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by extending the lip zone length to at least 140 times the stabbing flank clearance, which is a specific dimensional parameter modification. This quantitative change transforms the lip zone from a conventional short structure to an extended structure that can withstand compressive loads through elastic deformation, directly resolving the contradiction between strength and complexity by optimizing a key geometric parameter.
Solution Approach 2:
The patent introduces dynamics by creating a noncontacting region between the metal-to-metal seal surface and the shoulder surface, allowing the lip zone to deform elastically under compression and return to its original shape when the load is removed. This dynamic behavior enables the joint to absorb and dissipate compressive energy, achieving high resistance to compression without permanent deformation or excessive structural complexity.
2Manufacturing precision
If the stabbing flank clearance is reduced to improve engagement precision, then the threading accuracy increases, but the ease of operation decreases
Solution Approach 1:
The patent applies parameter changes by establishing a specific relationship between the lip zone length and stabbing flank clearance (L ≥ 140c), where the clearance is maintained within an optimal range of 0.01-0.3mm. This parameter optimization ensures that the stabbing flanks can make precise contact for accurate engagement while the extended lip zone provides sufficient elastic deformation capacity, simultaneously achieving both threading accuracy and ease of operation.
Solution Approach 2:
The patent applies partial action by having only the stabbing flanks contact during insertion, while the load flanks and shoulder surfaces remain noncontacting until the joint is fully tightened. This selective contact mechanism allows the stabbing flanks to guide precise engagement with minimal clearance (0.01-0.3mm) while the extended lip zone provides the necessary compliance, resolving the contradiction between precision and ease of operation.
3Ease of operation
If the chamfer angle of the stabbing flank is increased to facilitate insertion, then the ease of operation improves, but the manufacturing precision decreases
Solution Approach 1:
The patent applies local quality by differentiating the chamfer angles at different portions of the stabbing flank: a first portion with a smaller chamfer angle (5-25°) for precise thread formation and a second portion with a larger chamfer angle (20-70°) for facilitating insertion. This localized variation in geometric properties allows each region to perform its specific function optimally, resolving the contradiction between insertion ease and manufacturing precision.
Solution Approach 2:
The patent applies segmentation by dividing the stabbing flank into multiple portions with different chamfer angles rather than using a uniform angle throughout. The first portion (root side) and second portion (crest side) are segmented to have distinct geometric characteristics, enabling the root portion to maintain manufacturing precision while the crest portion facilitates easier insertion, thus resolving the contradiction between the two requirements.
Data Source
Figure 1(A)~2
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AI summary
A tubular threaded joint which has excellent resistance to compression and which permits easy tightening operation in the field in a vertical state comprises a pin having a male threaded zone and a box having a female threaded zone. The pin or the box has an end shoulder surface on its end, and the other member has a shoulder surface which abuts against the end shoulder surface. The screw threads of the male threaded zone and the female threaded zone are trapezoidal threads having a crest, a load flank, and a stabbing flank. The lip length, which is the distance in the axial direction of a member having an end shoulder surface between the end shoulder surface and the closest engaged thread to that surface, is at least 140 times the stabbing flank clearance, which is the distance in the axial direction between the stabbing flanks of the male thread and the female thread when the load flanks of the male and female threads contact each other. The stabbing flank of the male thread is preferably chamfered.