Step-to-Step Wedge Thread Connections for High-Pressure Sealing
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Solution Overview
Problem
Wedge thread connections face issues with indeterminate make-up, leading to increased stress and potential failure under high pressure, and the trapping of pipe dope can cause false torque readings and structural integrity issues due to inadequate evacuation.
Innovation Solution
A two-step wedge thread connection with axially misaligned pin and box steps, featuring a step-to-step wedge design that generates increased interference at final make-up, utilizing a dovetailed profile and varying axial separation between steps to create a pre-tensioned and pre-compressed connection, which delays the reduction of seal interference under external forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wedge thread connections are used to form a seal, then thread seal capability is improved, but indeterminate make-up occurs leading to increased stress and potential failure under high pressure
Solution Approach 1:
The connection is divided into two distinct steps: a first step with a first pitch providing initial engagement and alignment, and a second step with a second pitch providing final sealing engagement. This segmentation allows the connection to progress through controlled stages, ensuring determinate make-up while maintaining reliable thread seal capability.
Solution Approach 2:
The invention changes the pitch parameter between steps - the first step has a coarser pitch for easier engagement, while the second step has a finer pitch for precise sealing. This parameter variation enables the connection to achieve both reliable sealing and determinate make-up characteristics, resolving the contradiction between seal capability and strength under pressure.
2Reliability
If wedge thread connections are used, then seal formation is improved, but make-up process becomes indeterminate causing false torque readings
Solution Approach 1:
The make-up process is segmented into two distinct phases corresponding to the two steps. The first step provides initial engagement with a coarser pitch that allows for easier alignment, while the second step with finer pitch provides the final sealing engagement. This segmentation creates determinate make-up characteristics at each stage, enabling accurate torque readings during the critical sealing phase.
Solution Approach 2:
By varying the pitch parameter between the two steps, the invention creates distinct mechanical characteristics for each phase. The transition from coarser to finer pitch ensures that the final sealing engagement occurs at a predictable, determinate point, eliminating false torque readings while maintaining reliable seal formation.
3Ease of operation
If pipe dope is applied to lubricate threads, then ease of make-up is improved, but dope entrapment occurs causing structural integrity issues
Solution Approach 1:
The two-step design segments the make-up process into distinct phases. The first step with coarser pitch allows pipe dope to be effectively lubricated during initial engagement, while the second step with finer pitch provides precise sealing engagement. The segmented structure prevents dope entrapment by ensuring that the sealing surfaces are properly aligned and contacted in the second step, maintaining structural integrity while preserving ease of make-up.
4Stability of the object's composition
If axial separation between steps is varied, then pre-tension and pre-compression are created improving connection stability, but device complexity increases
Solution Approach 1:
The invention varies the axial separation parameter between the two steps to create beneficial pre-tension and pre-compression effects. The first step has a different axial separation than the second step, which generates internal stresses that enhance connection stability under external loads. Despite this parameter variation, the overall device complexity remains manageable because the basic two-step structure is straightforward, and the axial separation variation is achieved through standard manufacturing techniques.
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
The connection achieves improved make-up and break-out torque characteristics, reduces the risk of structural integrity loss, and provides enhanced resistance against radial separation and pressure, while tolerating dope entrapment without compromising the connection's integrity.
Implementation Method 1
wedge threads disposed on each of the first and second pin steps and box steps... step-to-step wedge design that generates increased interference at final make-up... opposing pin and box stab and load flanks at different times during makeup
Data Source
Figure 1A~2
Figure 3A~3B
Figure 3C~3D
AI summary
A threaded connection includes a pin member comprising a first pin step and a second pin step, and pin wedge threads disposed on each of the first and second pin steps and a box member comprising a first box step and a second box step, and box wedge threads disposed on each of the first and second box steps, wherein an axial separation of the first and second pin steps differs from an axial separation of the first and second box steps.