Tapered Tubular Threaded Joint for Lower Make-Up Torque
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Solution Overview
Problem
Tubular threaded joints in the oil and gas industry face challenges with high torque requirements, especially in large diameter tubes with thin walls, which can lead to deformation or collapse under high torques.
Innovation Solution
The design incorporates a tubular threaded joint with tapered male and female threads, featuring negatively inclined load and stabbing flanks, and a unique taper configuration in specific portions of the threads to reduce torque requirements and interference near sealing zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional tapered threads are used in large diameter tubes with thin walls, then the joint can be made up, but the torque requirement becomes excessively high causing deformation or collapse of the thin walls
Solution Approach 1:
The thread design applies different taper angles to different portions of the thread. The first portion has a first taper angle while the second portion has a second taper angle, creating local variations in thread geometry. This allows the thread to have high strength engagement in some regions while reducing torque requirements in other regions, particularly near the sealing zone where thin walls are most vulnerable to deformation
Solution Approach 2:
The thread is divided into distinct portions with different geometric characteristics. The first portion and second portion have different taper angles, effectively segmenting the thread functionally. This segmentation allows optimization of different thread regions for different purposes: one portion for strength and engagement, another for reduced torque and protection of thin-walled sections
2Reliability
If high torque is applied to make up the joint in thin-walled large diameter tubes, then the threads engage properly, but the thin walls deform or collapse
Solution Approach 1:
By varying the taper angle locally in different portions of the thread, the design ensures reliable thread engagement in the first portion while reducing the torque transmitted to the thin-walled sections in the second portion. This local differentiation maintains engagement reliability where needed while protecting the tube wall shape where it is vulnerable
Solution Approach 2:
The thread geometry transitions dynamically from one taper angle to another along the axial direction. This dynamic variation in geometry allows the thread to adapt its mechanical characteristics along its length, providing high engagement reliability in the initial portion while reducing torque transmission in the later portion to prevent wall deformation
3Manufacturing precision
If standard tapered threads are used, then thread engagement is achieved, but unwanted interference occurs between sealing surfaces
Solution Approach 1:
The different taper angles in the first and second portions of the thread create local variations in how the threads engage and how forces are transmitted. This local differentiation allows precise thread engagement in the first portion while reducing unwanted interference forces transmitted to the sealing surfaces in the region influenced by the second portion
Data Source
AI summary
A tubular threaded joint for use in the oil and gas industry is described. The tubular threaded joint includes a first tubular member having a pin and a second tubular member having a box, wherein the pin is an end portion of the first tubular member and comprises on its radially outward-facing surface a male threaded zone comprising a tapered male thread.