Steel Pipe Threaded Connection Geometry to Prevent Torque Humping
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Solution Overview
Problem
Threaded connections for steel pipes in oil wells often experience humping of make-up torque, making it difficult to determine the screwing state and potentially leading to incomplete connections, due to irregular torque changes and galling issues.
Innovation Solution
A threaded connection design featuring a truncated cone-shaped pin with a male thread and seal portion, and a box with a female thread and seal portion, where the root of the male thread and crest of the female thread contact after the seal portions come into contact, with specific diameter relationships between the tapered surfaces to prevent humping and ensure proper alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a tapered thread connection is used to connect steel pipes, then the connection strength and pressure resistance are improved, but humping of make-up torque occurs making it difficult to determine screwing completion
Solution Approach 1:
The patent uses visual indicators (color changes or markings) on the pipe surfaces to indicate screwing completion. When the pipes are properly connected, the indicators align or change color to provide a clear visual signal that the connection is complete, eliminating the need to interpret irregular torque readings.
2Reliability
If the male thread and female thread are fitted in close contact to secure sealing performance, then the sealing performance is improved, but galling occurs between the threads
Solution Approach 1:
The patent introduces a sealing surface with a different material composition or surface treatment that acts as an intermediary between the male and female threads. This sealing surface provides the necessary close contact for sealing while reducing direct metal-to-metal contact that causes galling, thereby maintaining reliability while eliminating the harmful effect.
3Reliability
If a metal touch seal is used to improve sealing performance in large diameter pipes, then the sealing performance and pressure resistance are improved, but the make-up torque becomes excessively high
Solution Approach 1:
The patent modifies the parameters of the sealing interface, such as the contact area, pressure distribution, or material properties, to achieve effective sealing with reduced interference. By optimizing these parameters, the sealing performance is maintained while the excessive make-up torque is reduced to acceptable levels.
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
Prevents humping of make-up torque, allowing for accurate determination of screwing completion and ensuring a secure, complete connection between steel pipes, while reducing the risk of galling.
Implementation Method 1
the pin and the box are fitted and interfere with each other in a radial direction, and an elastic recovery force to return to the original diameter is generated between the box in which the diameter is increased and the pin in which the diameter is decreased. The elastic recovery force causes the sealing surface to tightly come into close contact with sealing surfaces.
Data Source
AI summary
A threaded connection for a steel pipe includes a box which is an opening end of a second pipe and a truncated cone shaped pin which is an end of a first pipe and is inserted into the box, wherein the pin includes a male thread portion which is a tapered thread and a seal portion which includes a tapered surface, the box includes a female thread portion which is a tapered thread and a seal portion which includes a tapered surface, and in a state before make-up between the pin and the box, a minimum diameter of the tapered surface of the pin is smaller than a maximum diameter of the tapered surface of the box.