Pipe-in-Pipe Pipeline Assembly for Overlapping Inner-Outer Welding
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Solution Overview
Problem
The assembly of pipe-in-pipe (PiP) pipelines during S-lay operations in the subsea oil and gas industry is hindered by the complexity of handling and welding in a confined space, where the inner pipe must slide relative to the outer pipe, prolonging the fabrication process and complicating handling due to the need for sequential welding of pipe joints.
Innovation Solution
A method and apparatus that utilize a primary and secondary support system to allow simultaneous or overlapping welding operations of inner and outer pipe sections, with the secondary support system retracting to enable the outer pipe section to be advanced and welded to the partially-completed pipeline, reducing the cycle time for adding new pipe joints and simplifying the welding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the inner pipe is allowed to slide relative to the outer pipe during assembly, then thermal expansion accommodation is improved, but handling complexity and welding time increase due to sequential operations required in confined space
Solution Approach 1:
The support system is designed to be dynamic rather than static, allowing the inner pipe to slide relative to the outer pipe during assembly. The secondary support system can be positioned and repositioned along the inner pipe, providing flexible support that adapts to different assembly stages while maintaining the sliding capability needed for thermal expansion accommodation.
Solution Approach 2:
The support system is divided into two independent subsystems: a primary support system for the outer pipe and a secondary support system for the inner pipe. This segmentation allows each subsystem to operate independently, enabling the inner pipe to slide while being supported, and simplifying the overall handling by treating the pipes as separate manageable units during assembly.
2Manufacturing precision
If sequential welding of inner and outer pipe joints is performed, then welding precision is maintained, but productivity decreases due to prolonged fabrication cycle time
Solution Approach 1:
The secondary support system is deployed in advance to support the inner pipe at the required position before the outer pipe is welded. This preliminary support enables the inner pipe welding operation to proceed independently and simultaneously with the outer pipe welding, rather than waiting for sequential completion. The support system is prepared beforehand to facilitate parallel operations.
Solution Approach 2:
The support system enables continuous welding operations by maintaining proper alignment and positioning of both inner and outer pipes throughout the assembly process. Rather than stopping for repositioning or realignment between sequential welding steps, the system allows both welding operations to proceed continuously and simultaneously, maximizing productivity while maintaining precision.
3Area of stationary object
If a compact four-station welding spread is implemented, then space utilization is improved, but device complexity increases due to the need for coordinated support and retraction mechanisms
Solution Approach 1:
The secondary support system for the inner pipe is nested within or alongside the primary support system for the outer pipe. This nested arrangement allows both support systems to coexist in the confined firing line space without requiring separate dedicated areas, enabling compact four-station welding spread while maintaining the functionality of supporting both pipes independently.
Solution Approach 2:
The support system is designed with multi-functionality to handle both inner and outer pipe support, positioning, and alignment tasks. The same structural framework supports both pipes, and the support mechanisms can serve multiple purposes including positioning during welding, allowing movement during sliding, and providing stability during assembly, thereby reducing the need for separate specialized devices.
Data Source
AI summary
Apparatus for assembling a pipe-in-pipe pipeline comprises a primary support system, such as an array of rollers, for supporting an outer pipe section and a secondary support system, such as a set of rails, for supporting an inner pipe section. The primary support system supports the outer pipe section centred on a longitudinal axis in common with a trailing end of a partially-completed pipeline. The secondary support system is deployed to support the inner pipe section also centred on that common axis, enabling the inner pipe section to be advanced and welded to an inner pipe of the partially-completed pipeline. The secondary support system is then retracted to advance the outer pipe section, supported by the primary support system, around the inner pipe section. This enables the outer pipe section to be welded to an outer pipe of the partially-completed pipeline.