Threaded Joint Incomplete Threads External Pressure Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Threaded joints for heavy wall steel pipes in harsh environments, such as deep-underground or ultra-deep-water oil wells, face challenges in maintaining effective sealing performance against both internal and external pressures, with existing solutions limited in improving external pressure sealing due to structural constraints and risks of galling or jump-out.
Innovation Solution
A threaded joint design featuring a pin and box configuration with tapered trapezoidal threads, including an incomplete thread section with reduced thread height near the intermediate seal portion, allowing radial contraction of the box under external pressure to enhance contact interfacial pressure, while maintaining sealing performance against internal pressure through surface-to-surface contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional threaded joint designs are used, then structural simplicity is maintained, but sealing performance against external pressure deteriorates
Solution Approach 1:
The threaded portion is segmented into a complete thread section and an incomplete thread section with reduced thread height. This segmentation allows the box to radially contract under external pressure, amplifying contact interfacial pressure at the sealing surface while maintaining structural integrity through the complete thread section.
Solution Approach 2:
The thread height is locally reduced in the incomplete thread section near the sealing surface, while the complete thread section maintains full thread height for structural strength. This local quality variation enables selective functionality: sealing enhancement where needed and structural support where required.
2Reliability
If thread height is reduced to allow radial contraction, then sealing performance against external pressure improves, but structural strength deteriorates
Solution Approach 1:
The threaded portion is divided into two functional segments: a complete thread section that maintains full structural strength and an incomplete thread section that enables radial contraction for sealing. This segmentation resolves the conflict between strength and sealing performance.
Solution Approach 2:
Thread height is locally reduced only in the incomplete thread section where radial contraction is needed for sealing, while the complete thread section retains full thread height to maintain overall structural strength of the joint.
3Reliability
If conventional threaded portions are used, then manufacturing simplicity is maintained, but risk of galling and jump-out increases
Solution Approach 1:
The threaded portion is segmented into complete and incomplete sections, where the incomplete section with reduced thread height reduces friction and contact pressure, thereby reducing the risk of galling and jump-out during tightening and under load.
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 design improves sealing performance against external pressure by amplifying contact interfacial pressure in the intermediate seal portion, maintaining sealing performance against internal pressure, and reducing the risk of galling and jump-out, thus providing a stable and efficient connection in harsh environments.
Implementation Method 1
a threaded joint including: a tubular pin (10), a tubular box (20), the pin (10) and the box (20) being fastened by screwing the pin (10) onto the box (20)
Implementation Method 2
allowing radial contraction of the box under external pressure to enhance contact interfacial pressure
Implementation Method 3
a first surface-to-surface seal portion and a second surface-to-surface seal portion
Data Source
AI summary
A pin includes, in order from a free end thereof, a shoulder surface, a first sealing surface, a first male threaded portion, a second sealing surface, and a second male threaded portion. A box includes a shoulder surface, a first sealing surface, a first female threaded portion, a second sealing surface, and a second female threaded portion. The flank angles of load flanks of the first male threaded portion and the first female threaded portion are each less than 0 degrees. The first male threaded portion is composed of, in order from near the second sealing surface, an incomplete thread section and a complete thread section. The incomplete thread section has a length of at least three times the thread pitch thereof and has a thread height lower than the thread height of the complete thread section. The incomplete thread section is provided with clearances between crests and roots.