Pipe Screw Joint Composite R-Curved Nose for Sealing and Compression
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Solution Overview
Problem
Conventional screw joints for pipes with outer diameters of 168.3mm or less face challenges in achieving sufficient sealing, compression resistance, and galling resistance while maintaining pipe rigidity, particularly in harsh environments such as oil and gas wells.
Innovation Solution
A screw joint design featuring a pin member with a composite R-curved nose portion and a tapered surface on the box member, where the nose portion's outer surface forms an outwardly convex curve with varying radii, and the box member's inner surface is tapered, ensuring metal-to-metal contact and enhanced sealing without excessive deformation, along with specific angle and gap configurations to improve rigidity and resistance properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the nose portion is extended in an elongated manner to form a shape non-continuous with the seal portion, then external pressure resistance property and axial compression resistance property are enhanced, but the thickness of the pin nose is reduced
Solution Approach 1:
The nose portion is formed with a composite R-curved surface consisting of multiple arcs with different radii of curvature. This curved geometry provides continuous load path and structural integrity while achieving the desired elongated shape for enhanced external pressure and compression resistance without compromising pin nose thickness.
2Strength
If the metal touch seal portion is disposed in the vicinity of a threaded portion, then external pressure resistance property is enhanced, but the sealing property may be compromised due to stress concentration
Solution Approach 1:
The seal portion is given a specific geometric configuration with controlled contact surface area and distribution. The composite R-curved surface creates optimal stress distribution in the seal region, ensuring reliable metal-to-metal sealing while maintaining external pressure resistance. The local geometry is optimized to prevent stress concentration at the seal-thread interface.
3Adaptability or versatility
If the pin nose thickness is reduced to achieve elongated shape, then the flexibility for seal portion design is improved, but the rigidity and compression resistance are worsened
Solution Approach 1:
The composite R-curved surface with multiple arcs of different radii provides structural reinforcement while maintaining the elongated profile. This curved geometry distributes stresses more effectively than a straight cylindrical shape, maintaining rigidity and compression resistance even with reduced pin nose thickness, thereby enabling flexible seal design without compromising strength.
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 sealing, compression resistance, and galling resistance properties, maintaining pipe rigidity even at smaller diameters, thereby improving the screw joint's performance in diverse drilling environments.
Implementation Method 1
The male threaded portion (7) and the female threaded portion (5) are threadedly engaged
Implementation Method 2
a screw joint for a pipe including: a pin member (3) having a male threaded portion (7)
Implementation Method 3
the outer peripheral surface of the nose portion (8) and the inner peripheral surface of the box member are brought into a metal to metal contact due to joining of the pin member and the box member by threaded engagement
Implementation Method 4
a contact interface forms a seal surface
Data Source
Figure 1(a)~1(c)
Figure 2~4
Figure 5~6
AI summary
Provided is a screw joint for a pipe which improves seal property, compression resistance property and galling resistance property. The screw joint for a pipe has a pin member 3 of which an outer diameter of a raw pipe portion is set to 168.3mm or less. An outer peripheral surface of a nose portion of the pin member 3 is formed into an outwardly projecting convex curve as viewed in cross section taken along an axial direction of the pin member. The convex curve is formed into a curved shape where a composite R curve is formed by sequentially connecting a plurality of outwardly convex arcs having different radii of curvature R from each other on a generating line of a cylindrical portion disposed adjacent to a male threaded portion. A radius of curvature R of the arc is increased as the arc is away from the male threaded portion, and a tangent of the arc on a connecting point agrees with a tangent of the arc which is a connection counterpart. The inner peripheral surface of a box member 1 is formed into a tapered surface which interferes with the outer peripheral surface of the nose portion of the pin member at the time of joining with the pin member, and a length of the nose portion of the pin member is set to 5mm or more and less than 20mm.