Thread Stops for Determinate Wedge Connection Make-Up
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Solution Overview
Problem
Wedge thread connections in oilfield tubulars face issues with indeterminate make-up, leading to variations in contact stresses and potential radial separation, which can result in premature failure due to over-torquing and repetitive make-up and break-out cycles, lacking positive-stop torque shoulders and determinate engagement.
Innovation Solution
Incorporating pin and box thread stops configured to contact when the connection is fully engaged, with the thread stops being machined using a milling process to ensure precise engagement and prevent radial separation, providing an additional anti-torque feature and determinate make-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wedge thread connections are used without thread stops, then the connection can be made up with simpler geometry, but the make-up position becomes indeterminate leading to variations in contact stresses and potential radial separation
Solution Approach 1:
Thread stops are pre-formed on the pin and box members at predetermined locations. During make-up, these pre-positioned stops automatically engage to establish a determinate final position, eliminating the need for complex control systems or post-assembly adjustments.
Solution Approach 2:
The thread stops act as intermediary elements between the pin and box threads. These stops provide a positive engagement feature that mediates the indeterminate make-up of wedge threads by establishing a fixed contact point, thereby determining the final engagement position without altering the fundamental wedge thread geometry.
2Strength
If higher torque is applied to ensure full engagement, then the connection strength increases, but radial separation and premature failure occur due to over-torquing
Solution Approach 1:
The thread stops provide tactile and torque feedback during the make-up process. When the stops engage, there is a noticeable change in torque resistance that signals full engagement has been achieved, preventing operators from applying excessive torque that would cause radial separation and premature failure.
Solution Approach 2:
The thread stops are pre-positioned to engage at the exact point of full thread engagement. This preliminary positioning ensures that the correct engagement point is reached before high torque is applied, allowing the connection to achieve full strength without the harmful effects of over-torquing.
3Adaptability or versatility
If repetitive make-up and break-out cycles are performed, then the connection can be assembled and disassembled multiple times, but the threads experience wear and loss of torque capacity
Solution Approach 1:
Thread stops are pre-formed with precise geometry and positioning to ensure consistent engagement across multiple make-up cycles. This preliminary precision reduces variability in engagement forces and minimizes wear during each cycle, preserving torque capacity over the connection's service life.
Solution Approach 2:
The thread stops concentrate the engagement forces at specific localized points rather than distributing wear across the entire thread interface. This localized contact quality reduces overall thread wear during make-up and break-out cycles, maintaining torque capacity and extending the reusable life of the connection.
Data Source
AI summary
A threaded connection includes a pin member having an external wedge thread increasing in width in a first direction, a box member having an internal wedge thread increasing in width in a second direction so that complementary internal and external wedge threads move into engagement upon make-up of the connection, a box thread stop at an end of the internal wedge thread of the box member, and a pin thread stop at an end of the external wedge thread of the pin member, wherein the pin and box thread stops are configured to contact when the connection is fully engaged.