Offshore Pipelaying Conveyor With Friction Stir Pipe Joining
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Solution Overview
Problem
The existing pipelaying processes using arc welding are time-consuming and inefficient, particularly due to the need for frequent vessel stops, difficulties in welding certain metals, and the thermal effects that alter metallurgical properties, especially when dealing with corrosion-resistant pipes.
Innovation Solution
A system utilizing friction stir welding (FSW) machines to connect pipes on a conveyor, allowing continuous vessel movement during pipelaying by forming connections with reduced thermal impact and enabling efficient joining of pipes without the need for frequent stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If arc welding is used to join pipe segments, then the pipes can be connected to form pipelines, but the vessel must stop frequently and the process becomes time-consuming
Solution Approach 1:
The pipe segments are pre-positioned on the conveyor system and pre-aligned before the welding process begins. This preliminary preparation allows the welding operation to proceed without requiring vessel stops, as all positioning and alignment actions are completed in advance while the vessel continues its deployment motion.
Solution Approach 2:
The welding system is designed to operate continuously as the vessel moves, with the conveyor system feeding pipe segments through the welding position at a controlled rate. This continuous operation eliminates the stop-start cycle of traditional arc welding, maintaining productive action throughout the pipelaying process.
2Ease of manufacture
If arc welding is used to join pipes, then connections can be made, but high temperatures are generated that affect metallurgical properties and require cooling time
Solution Approach 1:
The welding process is replaced with a mechanical friction-based joining method. The friction stir welding mechanism uses rotational friction to generate localized heat and mechanically mix the materials, then applies pressure to form a solid-state joint. This mechanical approach generates significantly less heat than arc welding and eliminates the need for post-weld cooling periods.
Solution Approach 2:
The welding process parameters are fundamentally changed from high-temperature arc welding to low-temperature friction stir welding. The temperature parameter is reduced from thousands of degrees (arc welding) to a fraction of that (friction stir welding), allowing the base metal properties to be preserved while still achieving strong joints.
3Reliability
If arc welding is used on corrosion-resistant pipes, then connections can be made, but certain metals are difficult or unweldable with arc welding
Solution Approach 1:
The welding process is replaced with friction stir welding, a mechanical solid-state joining process that does not rely on melting and fusion like arc welding. This mechanical approach can join a broader range of materials including corrosion-resistant alloys, dissimilar metals, and materials previously considered unweldable, while maintaining reliable joint strength.
Solution Approach 2:
The friction stir welding process is capable of joining dissimilar materials and composite structures that are incompatible with traditional arc welding. This includes corrosion-resistant pipe materials and other specialized alloys, expanding the range of materials that can be reliably connected in offshore pipeline applications.
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
Enables continuous pipelaying operations with reduced thermal impact on pipes, improving efficiency and allowing for the use of metals previously considered unweldable, while maintaining the mechanical properties of the pipes.
Implementation Method 1
friction stir welding (FSW) machines configured to connect the one or more pipes
Implementation Method 2
friction stir welding heats the pipes, or at least portions thereof, to high temperatures
Data Source
AI summary
A system for laying pipe includes a conveyor configured to receive one or more pipes, and one or more friction stir welding (FSW) machines configured to connect the one or more pipes to a pipeline deployed toward a sea floor.