Steel Pipe Threaded Joint Geometry for Galling-Free Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Threaded connections for steel pipes face issues with galling on sealing surfaces during make-up, which can lead to damage and decreased sealing performance, and existing solutions like lubricants with heavy metals are environmentally unfriendly or costly.
Innovation Solution
A threaded connection design featuring taper guide surfaces that interfere and slide before the sealing surfaces, with a buffer surface between the box taper guide and sealing surfaces to prevent damage and deformation, reducing the risk of galling while maintaining high sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pin and box sealing surfaces are fitted together with interference to generate contact pressure for sealing, then sealing performance is improved, but galling occurs on the sealing surfaces during make-up
Solution Approach 1:
The connection structure is segmented into three functional zones: taper guide surfaces (for alignment), buffer surfaces (for protection), and sealing surfaces (for sealing). This segmentation allows each zone to perform its specific function without interfering with others, preventing galling while maintaining sealing performance
Solution Approach 2:
The taper guide surfaces perform preliminary alignment action before the sealing surfaces make contact. During make-up, the taper guide surfaces slide against each other first, establishing proper alignment before the buffering action begins, ensuring that sealing surfaces only contact after alignment is complete
2Object-affected harmful factors
If lubricants with heavy metals are used to prevent galling, then galling resistance is improved, but environmental friendliness and cost are worsened
Solution Approach 1:
The connection structure itself provides anti-galling protection through its geometric design (taper guide surfaces and buffer surfaces), eliminating the need for external lubricants or coatings. The structure serves its own protective function, making the connection self-sufficient and environmentally friendly
Solution Approach 2:
The harmful dependency on heavy metal lubricants is extracted and removed from the system. The anti-galling function is achieved purely through mechanical design of the connection surfaces, eliminating environmental pollution and cost associated with specialized lubricants
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 solution effectively prevents galling on the sealing surfaces during make-up and ensures high sealing performance after completion, reducing the risk of damage and maintaining effective sealing against both internal and external pressures.
Implementation Method 1
the pin taper guide surface and the box taper guide surface slide against each other when the pin and the box are made up
Implementation Method 2
Each of the sealing surfaces tries to recover to their original diameters and thus produces an elastic recovery, thereby generating contact pressures on the sealing surfaces
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A threaded connection for steel pipe is provided that prevents galling on the sealing surfaces during make-up while providing high sealing performance after completion of make-up. The pin (10) includes a nose (112) including a pin taper guide surface (112a) and a pin sealing surface (113) including a taper surface (113a). The box (20) includes a nose-receiving portion (22) including a box taper guide surface (22a), a box sealing surface (23) including a taper surface (23a), and a buffer surface (24). The taper angle of the taper surfaces (113a, 23a) includes a second taper angle larger than the taper angle of the taper guide surfaces (112a, 22a). The threaded connection (1) is constructed so as to satisfy Dp2>Db2>Dp1 and Lb2>Lp2. The buffer surface (24), located between the box taper guide surface (22a) and taper surface (23a), has a length of 0.75 mm or larger, and is located outward of an imaginary plane (V) determined along radial directions.