Threaded Joint for Steel Pipes With Dual Sealing Surfaces
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Solution Overview
Problem
Threaded joints for heavy wall steel pipes in harsh environments face challenges in providing adequate sealing performance against both internal and external pressures, with existing solutions not fully addressing the need for improved resistance and contact pressure maintenance.
Innovation Solution
A threaded joint design featuring a pin and box configuration with specific geometric features such as tapered surfaces, annular portions, and a nose portion, which provide enhanced resistance to radial contraction and maintain contact pressure through strategic clearances and surface interactions, ensuring improved sealing performance against both internal and external pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy wall steel pipes are used in harsh environments, then strength and pressure resistance are improved, but sealing performance against internal and external pressures deteriorates
Solution Approach 1:
The threaded joint is divided into multiple functional segments: a first seal portion with first sealing surfaces for internal pressure sealing, and a second seal portion with second sealing surfaces for external pressure sealing. This segmentation allows each seal portion to specialize in sealing against specific pressure directions, resolving the contradiction between strength and sealing performance.
Solution Approach 2:
Different regions of the threaded joint are given different geometric properties: the first sealing surfaces are configured with specific taper angles and contact characteristics optimized for internal pressure, while the second sealing surfaces have different characteristics optimized for external pressure. This local differentiation of quality enables simultaneous optimization for both internal and external pressure sealing.
2Strength
If tapered threaded portions are used, then connection strength is improved, but contact pressure maintenance under excessive loads deteriorates
Solution Approach 1:
The shoulder surfaces are positioned and configured to make contact before the tapered threaded portions engage under excessive loads. This preliminary action of the shoulder surfaces prevents separation of the joint components, thereby maintaining contact pressure on the sealing surfaces even when excessive loads are applied to the tapered threads.
Solution Approach 2:
The shoulder surfaces act as a cushioning element that absorbs and distributes excessive loads before they can compromise the sealing contact. By providing this protective cushioning in advance, the sealing surfaces maintain their contact pressure and sealing effectiveness.
Data Source
AI summary
A threaded joint is constructed of a pin and a box. The pin includes, in order from an end thereof, a shoulder surface, a nose portion, a first sealing surface, a first male threaded portion, an annular portion, a second sealing surface, and a second male threaded portion. The box includes a shoulder surface, a recessed portion, a first sealing surface, a first female threaded portion, an annular portion, a second sealing surface, and a second female threaded portion. In the threaded joint, in a fastened state, the shoulder surfaces are in contact with each other, the first sealing surfaces are in contact with each other, the second sealing surfaces are in contact with each other, a clearance is provided between the nose portion and the recessed portion, a clearance is provided between the annular portions.