Welded Pipe Threaded Connections With Uniform Internal Diameter
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Solution Overview
Problem
Welded pipes used in oil and gas applications often have non-uniform inner and outer diameters due to longitudinal seams, leading to weakened threaded connections that may leak, and existing methods to enhance these connections, such as swaging, are unreliable as they can cause the pipe to split or yield excessively.
Innovation Solution
A method involving the application of a weld patch along the interior surface of the pipe to create a uniform inside diameter, with specific heat input and machining processes to ensure the patch's strength matches or exceeds the pipe's yield strength, allowing for the formation of strong, gas-tight or liquid-tight threaded connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If welded pipe is used to reduce manufacturing cost, then productivity is improved, but manufacturing precision deteriorates due to non-uniform inside diameter from longitudinal seams
Solution Approach 1:
The weld patch is applied to the interior surface before threading operations to pre-correct the non-uniform inside diameter caused by the longitudinal seam. This preliminary action ensures that subsequent threading occurs on a uniformly prepared surface, preventing connection weaknesses.
Solution Approach 2:
A weld patch is selectively applied only to the interior surface at the location of the longitudinal seam, creating a localized reinforcement zone. This local quality improvement addresses the specific defect area without requiring complete pipe replacement or extensive rework.
2Strength
If swaging is used to enhance connector strength on welded pipe, then strength is improved, but reliability deteriorates due to pipe splitting or excessive yielding
Solution Approach 1:
The weld patch is applied and machined to uniform dimensions before threading operations, pre-strengthening the connector region. This preliminary reinforcement allows the subsequent threading process to create strong, reliable connections without the need for risky swaging operations that could split the pipe.
3Ease of manufacture
If longitudinal seam is present in welded pipe, then ease of manufacture is improved, but strength deteriorates at threaded ends due to non-uniform geometry
Solution Approach 1:
The weld patch is applied to the interior surface before threading to pre-compensate for the geometric non-uniformity caused by the longitudinal seam. This preliminary correction ensures that the threaded connection is formed on a uniformly prepared surface, maintaining connection strength despite the presence of the seam.
Solution Approach 2:
The weld patch creates a localized zone of improved geometry and strength at the interior surface where the longitudinal seam is present. This local quality enhancement specifically addresses the weakness at the threaded ends without affecting the overall ease of manufacture of the welded pipe.
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 method enhances the strength of tubular connections to achieve mechanical properties comparable to seamless pipes, providing reliable gas-tight or liquid-tight seals and increased tensile ratings, addressing the weaknesses in traditional welded pipe connections.
Implementation Method 1
applying a patch of material to the interior surface, such that the patch covers an arcuate segment of the interior surface that includes the welded seam
Implementation Method 2
machining the patch such that the interior surface of the tubular member from the tube end to the axially spaced first location has a uniform inside diameter
Data Source
AI summary
A tubular member includes a tube body, a tube end, an exterior surface, an interior surface, a nominal wall thickness, a longitudinal axis, a welded seam, and a patch of material. The welded seam forms an arcuate portion of the interior surface, and the patch covers a portion of the interior surface that includes a portion of the welded seam, extending from the tube end to an axially spaced first location. The resulting interior surface from the tube end to the axially spaced first location has a uniform inside diameter.