Pipe Threaded Joint Nose Profile for Sealing and Galling Resistance
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Solution Overview
Problem
Existing threaded joints for pipes in oil and gas production face challenges in achieving optimal sealability, compression resistance, and galling resistance, particularly in harsh environments, due to issues like galling during make-up and potential leaks caused by reduced contact pressure.
Innovation Solution
A threaded joint design featuring a pin component with an outward convex curve on its nose surface, formed by a composite R curve of arcs with increasing radii, and a tapered surface on the box component, which intersects the convex curve to create a metal-to-metal seal, reducing the likelihood of galling and maintaining sufficient thickness for enhanced sealability and compression resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seal contact pressure is increased to improve sealability, then sealability is improved, but galling occurs during the make-up process
Solution Approach 1:
The pin nose is designed with a curved surface defined by a composite function of two different radii of curvature. This curved geometry distributes the seal contact pressure more evenly across the sealing surface, preventing localized high stress concentrations that cause galling while maintaining sufficient overall contact pressure for reliable sealing.
2Strength
If the pin nose thickness is reduced to allow seal positioning at the end, then external pressure resistance is improved, but the structural integrity and compression resistance are reduced
Solution Approach 1:
The pin nose structure is segmented into a first region with larger radius of curvature that maintains thickness and structural integrity, and a second region with smaller radius of curvature that optimizes external pressure resistance. This segmentation allows the pin nose to maintain sufficient thickness for structural stability while achieving optimal external pressure resistance through the geometric design of the second region.
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 enhances sealability, compression resistance, and galling resistance by ensuring proper contact pressure distribution and preventing leaks, while maintaining the thickness of the pin nose end, thus providing stable performance under various operational conditions.
Implementation Method 1
the nose outer peripheral surface of the pin component and the inner peripheral surface of the box component come into metal-to-metal contact so that the contact interface forms a seal surface
Implementation Method 2
The tapered thread has a key role in firmly securing the tubular joint
Implementation Method 3
a male member, a nose extending to a pipe end from the male member, and a shoulder provided at an end of the nose; and a box component including a female member screwed onto the male member
Data Source
Figure 1(a)~1(c)
Figure 2~4
Figure 5~6
AI summary
Provided is a threaded joint for a pipe in which sealability, compression resistance, and galling resistance are enhanced. Specifically, a pin nose outer peripheral surface (30) forms an outward convex curve in an axial cross-sectional view; the convex curve is such that a composite R curve (N), in which a plurality of arcs having different radiuses of curvature (Rs) are connected in sequence to a generating line of a cylindrical portion next to a male member (7) directly or via line segments having a length of 2.5 mm or less, is curved such that the radiuses of curvature (Rs) increase with distance from the male member (7) and tangents on connection points of the arcs are aligned with those of corresponding arcs connected thereto; and the inner peripheral surface of a box component (1) facing the pin nose (8) is a tapered surface (20) that interferes with the pin nose outer peripheral surface (30) when connected to a pin component (3).