Coaxial Pipe Element External Welding Junction Forging

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Solution Overview

Problem

Existing methods for connecting coaxial pipe elements in undersea pipelines face challenges in ease of installation, particularly in welding and inspecting welds, which are complex and prone to fatigue due to the need for internal welding and the use of multiple parts that compromise mechanical reliability.

Innovation Solution

A method involving junction forgings with two branches of revolution, where the inner branch is welded externally to the inner pipe and the outer branch is welded externally to the outer pipe, with the inner pipe expanded to facilitate external welding and inspection, using either thermal expansion or mechanical traction to create a sufficient gap for external access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If internal welding is performed to connect the inner pipe to the junction forging, then the connection is achieved, but the welding and inspection process becomes complex and time-consuming

Engineering Contradiction:

Improveweld connection reliabilityVSAvoidwelding and inspection complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional welding approach by performing all welding operations from the outside of the inner pipe rather than from the inside. The junction forging is designed with an inner branch that extends beyond the outer pipe end, allowing welders to access and weld the inner pipe to the inner branch from the outside. This inversion eliminates the complexity of internal welding and inspection while maintaining connection reliability.

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If multiple parts are used in the junction forging assembly, then the connection flexibility is improved, but the mechanical reliability and fatigue resistance decrease

Engineering Contradiction:

Improveconnection flexibilityVSAvoidmechanical reliability and fatigue resistance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent merges the inner and outer branch structures into a single integrated junction forging component. This unified structure eliminates the need for multiple separate parts and connections, thereby improving mechanical reliability and fatigue resistance. The integrated design maintains connection flexibility through the inherent geometry of the merged structure, which accommodates the inner and outer pipes in a coordinated manner.

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If the inner pipe is welded from the outside, then the welding and inspection process is simplified, but the inner pipe must be expanded to create access space

Engineering Contradiction:

Improvewelding and inspection complexityVSAvoidmanufacturing complexity

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by pre-expanding the inner pipe at the end section before the welding operation. This expansion creates the necessary space for welders to access the inner pipe from the outside and perform welding operations. The expansion is performed in advance of the welding step, simplifying the overall manufacturing process by eliminating the need for complex internal welding fixtures and procedures.

Inventive Principle:

Principle #10Preliminary action

4Ease of operation

If the inner pipe is expanded to create gap for external welding, then external welding access is achieved, but the pipe structure is modified

Engineering Contradiction:

Improvewelding accessibilityVSAvoidpipe structural integrity

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by expanding only the end section of the inner pipe rather than the entire pipe structure. This localized expansion creates the necessary gap for external welding access at the junction forging area while leaving the rest of the pipe structure unchanged and intact. The selective modification maintains overall pipe structural integrity while providing the needed accessibility for welding operations.

Inventive Principle:

Principle #3Local quality

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

This method simplifies the connection process, reduces fatigue risks, and enhances mechanical reliability by allowing all welds to be performed externally, improving the assembly and maintenance of undersea pipelines while minimizing stress during installation and operation.

Implementation Method 1

using either thermal expansion or mechanical traction to create a sufficient gap for external access

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

using either thermal expansion or mechanical traction to create a sufficient gap for external access

Methodology Applied

Scientific EffectMechanical traction: Mechanical Force

Data Source

PatentUS8794675B2Coaxial pipe element

Publication Date: 2014.08.05 SAIPEM SA

AI summary

A coaxial pipe element (1) includes an outer pipe (1a) and an inner pipe (1b), and at each of its ends a junction forging (2a, 2b), each forging having at least an inner first branch (32) set back (L1) from an outer first branch (31), in which all of the circular welds between the inner and the outer pipe and the junction forgings are made on the outside of the pipes.